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, ROLD B. LEE LIBRARY
[4hAM YOUNG UNWERSITV
PROVO, UTAH
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f-
I
: 7
ANATOMY
OF
THE HUMAN BODY
:by
HENRY GRAY, F.R.S.
FELLOW OF THE ROYAL COLLEGE OF SURGEONS; LECTURER ON ANATOMY AT ST. GEORGE's
HOSPITAL MEDICAL SCHOOL, LONDON
TWENTIETH EDITION
THOROUGHLY REVISED AND RE-EDITED
BY
WARREN H. LEWIS, B.S., M.D.
PROFESSOR OF PHYSIOLOGICAL ANATOMY, JOHNS HOPKINS UNIVERSITY, BALTIMORE, MD.
HUustratet) mth 1247 jenoravtngs
LEA & FEBIGER
PHILADELPHIA AND NEW YORK
Copyright
LEA & FEBIGER
1918
^r"^"-^?"
PROVO, UTAH
THE FIRST EDITION OF THIS WORK
WAS DEDICATED TO
SIR BENJAMIN COLLINS BRODIE, Bart., F.R.S., D.C.L.
IN ADMIRATION OF
HIS GREAT TALENTS
AND IX REMEMBRANCE OF
MANY ACTS OF KINDNESS SHOWN TO THE ORIGINAL
AUTHOR OF THE BOOK
FROM AN
EARLY PERIOD OF HIS PROFESSIONAL CAREER
PREFACE TO THE TWENTIETH EDITION.
SixcE the publication of the first English edition of this work in 1858 and the
first American edition in 1859 great advances in the subject of Anatomy have been
made, especially in microscopic anatomy and the anatomy of the embrjo. This
knowledge was embodied from time to time in the successive editions until finally
considerable portions of the text, sometimes sections, were devoted to these sub-
jects. However, the main text has always remained primarily a descriptive
anatomy of the human body.
In the present edition the special sections on embryology and histology have
been distributed among the subjects under which they naturally belong. New
matter on physiological anatomy, laws of bone architecture, the mechanics and
variations of muscles have been added, occupying much of the space formerly
devoted to the sections pn applied anatomy.
The sections on the ductless glands and the nervous system have been largely
rewritten. In the latter a more rational presentation of the sympathetic nervous
system has been achieved through the use of diagrams and descriptions based on
physiological and pharmacological work. The central connections of the spinal
and cranial nerves are also emphasized.
Illustrations have been added wherever important points could be made more
clear, and throughout the work colored pictures have been even more extensively
used than heretofore. In this respect special mention might be made of the central
nervous system and the section on the muscles. In the section on Syndesmology
six illustrations are used from Quain's Anatomy through the courtesy of the
publishers, Messrs. Longmans, Green & Company, of London.
The use of the B. N. A. nomenclature in English has been retained practically
unchanged in this edition and important references to the literature have been
added at the end of each section.
As a practical work on the subject for the student, Gray's Anatomy has always
been recognized and appreciated. The plan originally formulated, which has
proved so successful, has been adhered to as much as possible. It is interesting to
note that although Henry Gray saw only the first edition, much of the original
text persists and many of his illustrations are still in use. Bearing this in mind it
has been the endeavor of the Editor to supply only such changes as advances in
the science made necessarv in order that this work may reflect the latest accessions
to anatomical knowledge.
W. H. L.
Baltimore, 1918.
CONTENTS.
EMBRYOLOGY.
The Animal Cell.
Cytoplasm 35
Nucleus 36
Reproduction of Cells 36
Prophase 36
Metaphase 36
Anaphase ... 36
Telophase ... . . 38
The Ovum.
Yolk
Germinal Vesicle
Coverings of the Ovum
Maturation of the Ovum
The Spermatozoon .
Fertilization of the Ovum
Segmentation of the Fertilized Ovum.
The Neural Groove and Tube
The Notochord .
39
40
40
40
42
44
The Primitive Streak; Formation of the
Mesoderm 47
Ectoderm 47
Entoderm 49
Mesoderm 49
50
52
The Primitive Segments
Separation of the Embryo
The Yolk-sac .
52
53
54
Development of the Fetal Membranes and Placenta.
The Allantois 54
The Amnion 56
The Umbilical Cord and Body-stalk ... 57
Implantation or Imbedding of the Ovum . 58
The Decidua 59
The Chorion 60
The Placenta 62
Fetal Portion 62
Maternal Portion 63
Separation of the Placenta .... 64
The Branchial Region.
The Branchial or Visceral Arches and Pharyn-
geal Pouches 65
The Nose and Face 67
The Limbs 71
Development of the Body Cavities . . 72
The Form of the Embryo at Different Stages
of its Growth . ... 74
OSTEOLOGY.
Long Bones . 79
Short Bones 79
Flat Bones 79
Irregular Bones 80
Surfaces of Bones 80
Development of the Skeleton.
The Skeleton 80
The Vertebral Column 80
The Ribs 82
The Sternum 83
The Skull 83
Bone.
Structure and Physical Properties ... 86
Periosteum 87
Marrow 87
Vessels and Nerves of Bone 88
Minute Anatomy 89
Chemical Composition 91
Ossification 91
Intramembranous Ossification ... 91
Intercartilaginous Ossification ... 93
The Vertebral Column.
General Characteristics of a Vertebra.
The Cervical Vertebrae
The First Cervical Vertebra .
The Second Cervical Vertebra
The Seventh Cervical Vertebra
97
99
100
101
The Thoracic Vertebra
The First Thoracic Vertebra
The Ninth Thoracic Vertebra
The Tenth Thoracic Vertebra
The Eleventh Thoracic Vertebra
The Twelfth Thoracic Vertebra
The Lumbar Vertebrae
The Fifth Lumbar Vertebra .
The Sacral and Coccygeal Vertebrae
The Sacrum .....
The Coccyx
Ossification of the Vertebral Column
The Vertebral Column as a Whole.
102
104
104
104
104
104
104
106
106
106
111
111
Curves 114
Surfaces 114
Vertebral Canal . . 116
The Thor.\x.
Boundaries 117
The Sternum 119
Manubrium 120
Body 120
Xiphoid Process 121
The Ribs 123
Common Characteristics of the Ribs . 123
Peculiar Ribs 125
First Rib 125
Second Rib 125
Tenth Rib 126
Eleventh and Twelfth Ribs . . 126
The Costal Cartilages 127
(9)
10
CONTENTS
The Skull.
The Cranial Bones.
The Occipital Bone 129
The Squama 129
Lateral Parts 131
Basilar Parts 132
Angles 132
The Parietal Bone 133
The Frontal Bone 135
Squama 135
Orbital or Horizontal Part .... 137
The Temporal Bone 138
The Squama 139
Mastoid Portion 141
Petrous Portion 142
Tympanic Part 145
Styloid Process 145
The Sphenoid Bone 147
Body 147
The Great Wings 149
The Small Wings 151
Pterygoid Processes 151
The Sphenoidal Conchse 152
Ethmoid bone 153
Cribriform plate 153
Perpendicular Plate 154
Labyrinth or Lateral Mass .... 154
Sutural or Wormian Bones 156
The Facial Bones.
The Nasal Bones 156
The Maxillae (Upper Jaw) . • . . . 157
The Maxillary Sinus or Antrum of High-
more 160
The Zygomatic Process 161
The Frontal Process 161
The Alveolar Process 161
The Palatine Process 162
Changes Produced in the Maxilla by Age 163
The Lacrimal Bone 163
The Zygomatic Bone 164
The Palatine Bone 166
The Horizontal Part 167
The Vertical Part 167
The Pyramidal Process or Tuberosity . 168
The Orbital Process 168
The Sphenoidal Process 169
The Inferior Nasal Concha 169
The Vomer 170
The Mandible (Lower Jaw) 172
Changes Produced in the Mandible by
Age 175
The Hyoid Bone 177
The Exterior of the Skull.
Norma Verticalis 178
Norma Basalis 179
Norma Lateralis 182
The Temporal Fossa 183
The Infratemporal Fossa .... 184
The Pterygopalatine Fossa .... 185
Norma Occipitalis 185
Norma Frontalis 185
The Orbits 188
The Interior of the Skull.
Inner Surface of the Skull-cap .... 189
Under Surface of the Base of the Skull . 190
The Anterior Fossa 190
The Middle Fossa 190
The Posterior Fossa 192
The Nasal Cavity 194
Anterior Nasal Aperture 196
Dififerences in the Skull Due to Age . . . 196
Sexual Differences in the Skull .... 197
Craniology 197
The Extremities.
The Bones of the Upper -Extremity.
The Clavicle 200
Lateral Third 200
Medial Two-thirds 201
The Sternal Extremity 202
The Acromial Extremity 202
The Scapula 202
The Spine 203
The Acromion 203
The Coracoid Process 207
The Humerus 209
Upper Extremity 209
The Head 209
The Anatomical Neck .... 209
The Greater Tubercle .... 209
The Lesser Tubercle .... 209
The Body or Shaft 209
The Lower Extremity 212
The Ulna 214
The Upper Extremity 214
The Olecranon 214
The Coronoid Process .... 214
The Semilunar Notch .... 215
The Radial Notch 215
The Body or Shaft 215
The Lower Extremity 218
The Radius 219
The Upper Extremity 219
The Body or Shaft 219
The Lower Extremity 220
The Hand.
The Carpus 221
Common Characteristics of the Carpal
Bones 221
Bones of the Proximal Row . . . .221
The Na\acular Bone . . . .221
The Lunate Bone 224
The Triangular Bone .... 224
The Pisiform Bone 225
Bones of the Distal Row .... 225
The Greater Multangular Bone . 225
The Lesser Multangular Bone . 225
The Capitate Bone 226
The Hamate Bone 227
The Metacarpus 227
Common Characteristics of the Meta-
carpal Bones . . . . . . . 227
Characteristics of the Individual Meta-
carpal Bones 228
The First Metacarpal Bone . . 228
The Second Metacarpal Bone . . 228
The Third Metacarpal Bone . . 228
The Fourth Metacarpal Bone . . 228
The Fifth Metacarpal Bone . . 228
The Phalanges of the Hand 230
Ossification of the Bones of the Hand . 230
The Bones of the Lower Extremity.
The Hip Bone 231
The Ilium 231
The Body 231
The Ala 232
The Ischium 234
The Body 234
The Superior Ramus .... 235
The Inferior Ramus 235
The Pubis 236
The Body 236
The Superior Ramus .... 236
The Inferior Ramus 237
The Acetabulum 237
The Obturator Foramen . . . 237
The Pelvis 238
The Greater or False Pelvis .... 238
The Lesser or True Pelvis .... 239
Axes ... 240
Position of the Pelvis 241
Differences between Male and Female
Pelves 241
Abnormalities 242
CONTENTS
11
The Femur 242
The Upper Extremity 243
The Head 243
The Neck 243
The Trochanters 244
The Body or Shaft 246
The Lower Extremity 247
The Architecture of the Femur . . . 248
The Patella 255
The Tibia 256
The Upper Extremity 256
The Body or Shaft 257
The Lower Extremity 259
The Fibula 260
The Upper Extremity or Head . . . 260
The Body or Shaft 260
The Lower Extremity or Lateral
Malleolus 262
The Fool.
The Tarsus 263
The Calcaneus 263
The Tarsus—
The Talus 266
The Cuboid Bone 269
The Navicular Bone 270
The First Cuneiform Bone .... 270
The Second Cuneiform Bone . . .271
The Third Cuneiform Bone .... 271
The Metatarsus 272
Common Characteristics of the Meta-
tarsal Bones 272
Characteristics of the Individual Meta-
tarsal Bones 272
The First Metatarsal Bone ... 272
The Second Metatarsal Bone . . 273
The Third Metatarsal Bone . . 274
The Fourth Metatarsal Bone . ' . 274
The Fifth Metatarsal Bone . . 274
The Phalanges of the Foot 275
Ossification of the Bones of the Foot . . 275
Comparison of the Bones of the Hand and
Foot 276
The Sesamoid Bones 277
SYNDESMOLOGY.
Bone 279
Hyaline Cartilage 279
Articular Cartilage 280
Costal Cartilage 281
White Fibrocartilage 281
Interarticular FibrocartUages . . . 281
Connecting FibrocartUages .... 282
Circumferential FibrocartUages . . . 282
Stratiform Fibrocartilages .... 282
Ligaments 282
The Articular Capsules 282
Mucous Sheaths 283
BursjE Mucosae 283
Development of the Joints . . 283
Classification of Joints
Synarthrosis 284
Sutura 284
Schindylesis 284
Gomphosis 284
Synchondrosis 284
Amphlarthrosis 285
Diathrosis 285
Ginglimus • 285
Trochoid 285
Condyloid 286
Articulation by Reciprocal Reception . 286
Enarthrosis 286
Arthrodia 286
The Kind of Movement Admitted in Joints.
Gliding Movement 286
Angular Movement 286
Circumduction 286
Rotation 287
Ligamentous Action of Muscles .... 287
Articulations of the Trunk.
Articulations of the Vertebral Column . . 287
Articulations of Vertebral Bodies . . 287
The Anterior Longitudinal Liga-
ment 287
The Posterior Longitudinal Liga-
ment 288
The Intervertebral Fibrocartilages 289
Structure 289
Articulations of Vertebral Arches . . 289
The Articular Capsules .... 290
The Ligamenta Flava .... 290
The Supraspinal Ligament . . . 290
Articulations of the Vertebral Column —
Articulations of Vertebral Arches —
The Ligamentum Nuchce . . . 290
The Interspinal Ligaments . . . 291
The Intertransverse Ligaments . 291
Articulation of the Atlas with the Epistro-
pheus or Axis 292
The Articular Capsules 292
The Anterior Atlantoaxial Ligament . 293
The Posterior Atlantoaxial Ligament . 293
The Transverse Ligament of the Atlas . 293
Articulations of the Vertebral Column with
the Cranium 295
Articulation of the Atlas with the
Occipital Bone 295
The Articular Capsules .... 295
The Anterior Atlantooccipital Mem-
brane 295
The Posterior Atlantooccipital Mem-
brane 296
The Lateral Ligaments .... 296
Ligaments Connecting the Axis with the
Occipital Bone 296
The Membrana Tectoria . . . 296
The Alar Ligaments 296
Articulation of the Mandible 297
The Articular Capsule 297
The Temporomandibular Ligament . 297
The Sphenomandibular Ligament . . 297
The Articular Disk 298
The Stylomandibular Ligament . . . 298
Costovertebral Articulations 299
Articulations of the Heads, of the Ribs . 299
The Articular Capsule .... 299
The Radiate Ligament .... 299
The Interarticular Ligament . . 300
Costotransverse Articulations . . . 300
The Articular Capsule .... 301
The Anterior Costotransverse Liga-
ment 301
The Posterior Costotransverse Liga-
ment 301
The Ligament of the Neck of the
Rib 302
The Ligament of the Tubercle of
the Rib 302
Sternocostal Articulations 302
The Articular Capsules 302
The Radiate Sternocostal Ligaments . 302
The Interarticular Sternocostal Liga-
ment 303
The Costoxiphoid Ligaments . . . 304
Interchondral Articulations .... 304
Costochondral Articulations .... 304
Articulation of the Manubrium and Body of
the Sternum 304
Mechanism of the Thorax .... 304
12
CONTENTS
Articulation of the Vertebral Column with
the Pelvis 306
The Iliolumbar Ligament .... 306
Articulations of the Pelvis 306
Sacroiliac Articulation 306
The Anterior Sacroiliac Ligament . 307
The Posterior Sacroiliac Ligament. 307
The Interosseous Sacroiliac Liga-
ment 308
Ligaments Connecting the Sacrum and
Ischium 309
The Sacrotuberous Ligament . 309
The Sacrospinous Ligament . . 309
Sacrococcygeal Symphysis .... 309
The Anterior Sacrococcygeal Liga-
ment .309
The Posterior Sacrococcygeal Liga-
ment 309
The Lateral Sacrococcygeal Liga-
ment 310
The Interarticular Ligaments . 310
The Pubic Symphysis 310
The Anterior Pubic Ligament . . 310
The Posterior Pubic Ligament . . 310
The Superior Pubic Ligament . . 310
The Arcuate Pubic Ligament . . 310
The Interpubic Fribrocartilaginous
Lamina 311
Mechanism of the Pelvis 311
Articulations of the Upper Extremity.
Sternoclavicular Articulation 313
The Articular Capsule 313
The Anterior Sternoclavicular Ligament 313
The Posterior Sternoclavicular Liga-
ment 313
The Interclavicular Ligament . . . 314
The Costoclavicular Ligament . . 314
The Articular Disk 314
Acromioclavicular Articulation .... 315
The Articular Capsule 315
The Superior Acromioclavicular Liga-
ment . . 315
The Inferior Acromioclavicular Liga-
ment 315
The Articular Disk 315
The Coracoclavdcular Ligament . . .315
The Trapezoid Ligament .... 315
The Conoid Ligament 315
The Ligaments of the Scapula . . . . 316
The Coracoacromial Ligament . . . 316
The Superior Transverse Ligament . . 317
The Inferior Transverse Ligament . . 317
Humeral Articulation or Shoulder-joint . . 317
The Articular Capsule 317
The Coracohumeral Ligament . . . 318
Glenohumeral Ligaments . . . .318
The Transverse Humeral Ligament . 319
The Glenoidal Labrum 319
Bursse 319
Elbow-joint 321
The Anterior Ligament 321
The Posterior Ligament 322
The Ulnar Collateral Ligament . . . 322
The Radial Collateral Ligament . . 322
Radioulnar Articulation 324
Proximal Radioulnar Articulation . . 324
The Annular Ligament .... 324
Middle Radioulnar Union .... 325
The Oblique Cord 325
The Interosseous Membrane . . 325
Distal Radioulnar Articulation . . . 325
The Volar Radioulnar Ligament 325
The Dorsal Radioulnar Ligament . 325
The Articular Disk 325
Radiocarpal Articulation or Wrist- joint . . 327
The Volar Radiocarpal Ligament . . 327
The Dorsal Radiocarpal Ligament . . 328
The Ulnar Collateral Ligament . . . 328
The Radial Collateral Ligament . . 328
Intercarpal Articulations 328
Articulations of the Proximal Row of
Carpal Bones 328
Intercarpal Articulations —
Articulations of the Proximal Row of
Carpa Bones —
The Dorsal Ligaments .... 328
The Volar Ligaments .... 328
The Interosseous Ligaments . . 328
Articulations of the Distal Row of
Carpal Bones 329
The Dorsal Ligaments .... 329
The Volar Ligaments .... 329
The Interosseous Ligaments . . 329
Articulations of the Two Rows of
Carpal Bones with Each Other .
The Volar Ligaments ....
The Dorsal Ligaments . ' . .
The Collateral Ligaments .
Carpometacarpal Articulations ....
Carpometacarpal Articulation of the
Thumb 330
Articulations of the Other Four Meta-
carpal Bones with the Carpus
The Dorsal Ligaments .
The Volar Ligaments
The Interosseous Ligaments
Intermetacarpal Articulations
The Transverse Metacarpal Ligament
Metacarpophalangeal Articulations .
The Volar Ligaments 332
The Collateral Ligaments , . . . . 332
Articulations of the Digits 333
329
329
329
329
330
331
331
331
331
331
331
332
Articulations of the Lower Extremity.
Coxal Articulation or Hip- joint .
The Articular Capsule ....
The Iliofemoral Ligament
The Pubocapsular Ligament
The Ischiocapsular Ligament
The Ligamentum Teres Femoris
The Glenoidal Labrum ....
The Transverse Acetabular Ligament
The Knee-joint
The Articular Capsule ....
The Ligamentum Patellae
The Oblique Popliteal Ligament
The Tibial Collateral Ligament .
The Fibular Collateral Ligament
The Cruciate Ligaments ....
The Anterior Cruciate Ligament
The Posterior Cruciate Ligament
The Menisci
The Medial Meniscus
The Lateral Meniscus
The Transverse Ligament
The Coronarj' Ligaments
Bursse
Articulations between the Tibia and
Tibiofibular Articulation
The Articular Capsule .
The Anterior Ligament .
The Posterior Ligament
Interosseous Membrane .
Tibiofibular Syndesmosis
The Anterior Ligament .
The Posterior Ligament
The Inferior Transverse Ligament
The Interosseous Ligament
Talocrural Articulation or Ankle-joint
The Articular Capsule ....
The Deltoid Ligament ....
The Anterior Talofibular Ligament
The Posterior Talofibular Ligament
The Calcaneofibular Ligament .
Intertarsal Articulations
Talocalcaneal Articulation
The Articular Capsule .
The Anterior Talocalcaneal Liga
ment
The Posterior Talocalcaneal Liga
ment
The Lateral Talocalcaneal Liga
ment
The Medial Talocalcaneal Liga
ment
333
334
335
335
335
336
336
336
339
340
340
340
341
341
342
342
342
342
343
343
343
343
345
347
348
348
348
348
348
348
348
348
349
349
349
350
350
351
351
351
352
352
352
352
352
352
353
CONTENTS
13
Intertarsal Articulations —
Talocalcaneal Articulation —
The Interosseous Talocalcaneal
Ligament
Talocalcaneonavicular Articulation .
The Articular Capsule .
The Dorsal Talonavicular Ligament
Calcaneocuboid Articulation
The Articular Capsule .
TheDorsalCalcaneocuboidLigamen
The Bifurcated Ligament .
The Long Plantar Ligament
The Plantar Calcaneocuboid Liga
ment
The Ligaments Connecting the Galea
neus and Navicular
The Plantar Calcaneonavicular
Ligament
Cuneonavicular Articulation
The Dorsal Ligaments .
The Plantar Ligaments .
Cuboideonavicular Articulation .
The Dorsal Ligament
353
353
354
354
354
354
354
354
354
354
355
355
356
356
356
356
357
Intertarsal Articulations —
Cuboideonavicular Articulation —
The Plantar Ligament .... 357
The Interosseous Ligament . . 357
Intercuneiform and Cuneocuboid Articu-
lation 357
The Dorsal Ligaments .... 357
The Plantar Ligaments .... 357
The Interosseous Ligaments . . 357
Tarsometatarsal Articulations .... 358
The Dorsal Ligaments 358
The Plantar Ligaments 358
The Interosseous Ligaments .... 358
Intermetatarsal Articulations 358
The Dorsal Ligaments 358
The Plantar Ligaments 358
The Interosseous Ligaments .... 358
The Transverse Metatarsal Ligament . 359
Metatarsophalangeal Articulations . . . 359
The Plantar Ligaments 359
The Collateral Ligaments .... 359
Articulations of the Digits 359
Arches of the Foot 360
MYOLOGY.
Mechanics of Muscle.
The Direction of Muscle Pull
The Action of Muscle Pull on Tendon
The Strength of Muscles ....
The Work Accomplished by Muscles
The Action of Muscles on Joints
Development of the Muscles.
The Ventro-lateral Muscles of the Neck .
Muscles of the Shoulder Girdle and Arm
The Muscles of the Leg
The Muscles of the Head
Striped or Voluntary Muscle ....
Vessels and Nerves of Striped Muscle
363
364
364
365
368
371
371
372
372
373
376
Tendons, Aponeuroses, and Fasci/e.
Tendons 376
Aponeuroses 376
Fasciai 376
The Fasci.*: and Muscles of the Head.
The Muscles of the Scalp.
The Skin of the Scalp 378
The Superficial Fascia 378
Epicranius 378
Occipitalis 379
Frontalis 379
Galea Aponeurotica 380
The Muscles of the Eyelid.
Orbicularis Oculi 380
Gorrugator 381
The Muscles of the Nose.
Procerus ... 382
Nasalis 382
Depressor Septi 382
Dilator Naris Posterior ....... 382
Dilator Naris Anterior 382
The Muscles of the Mouth.
Quadratus Labii Superiorio 383
Caninus 383
Zygomaticus 383
Mentalis 383
Quadratus Labii Inferioris 383
Triangularis 383
Buccinator 384
Pterygomandibular Raphe .... 384
Orbicularis Oris 384
Risorius 385
The Muscles of Mastication.
Parotideomasseteric Fascia 385
Masseter 385
Temporal Fascia 386
Temporalis 386
Pterygoideus Externus 386
Pterygoideus Internus 387
The Fasci-e and Muscles of the Antero-
lateral Region of the Neck.
The Superficial Cervical Muscle.
Superficial Fascia 387
Platysma 388
Variations 388
The Lateral Cervical Muscles.
The Fascia Colli 388
Sternocleidomastoideus 390
Variations 390
Triangles of the Neck 390
The Supra- and Infrahyoid Aluscles.
Digastricus 391
Variations 391
Stylohyoideus 392
Variations 392
The Stylohyoid Ligament .... 392
Mylohyoideus 393
Variations 393
Geniohyoideus 393
Sternohyoideus 393
Variations 393
Sternothyreoideus 393
Variations 394
Thyreohyoideus 394
Omohyoideus 394
Variations 394
The Anterior Vertebral Muscles.
Longus Colli 394
Longus Capitis 395
Rectus Capitis Anterior 395
Rectus Capitis Lateralis 395
14
COX TENTS
The Lateral Vertebral Muscles.
Scalenus Anterior 396
Scalenus Medius 396
Scalenus Posterior 396
Variations 396
The Fascia and Muscles of the Thunk.
The Deep Muscles of the Back.
The Lumbodorsal Fascia 397
Splenius Capitis 397
Splenius Cervicis 397
Variations 397
Sacrospinalis 397
Iliocostalis Lumborum 399
Iliocostalis Dorsi 399
Iliocostalis Cervicis 399
Longissimiis Dorsi 399
Longissimus Cervicis 399
Longissimus Capitis 399
Spinalis Dorsi 399
Spinalis Cer\-icis 400
Spinalis Capitis 400
Semispinalis Dorsi 400
Semispinalis Cervicis 400
Semispinalis Capitis 400
Multifidus 400
Rotatores 400
Interspinales 400
Extensor Coccygis 401
Intertransversarii 401
The Suboccipital Muscles.
Rectus Capitis Posterior Major
Rectus Capitis Posterior Minor
Obliquus Capitis Inferior .
Obliquus Capitis Superior .
The Suboccipital Triangle
401
401
402
402
402
The Muscles of the Thorax.
Intercostal Fascia 402
Intercostales 403
Intercostales Externi 403
Variations 403
Intercostales Interni 403
Subcostales 403
Transversus Thoracis 403
Levatores Costarum 403
Serratus Posterior Superior 404
Variations 404
Serratus Posterior Inferior 404
Variations 404
Diaphragm 404
Medial Lumbocostal Arch .... 404
Lateral Lumbocostal Arch .... 405
The Crura 405
The Central Tendon 406
Openings in the Diaphragm . . . 406
Variations 406
Mechanism of Respiration 407
The Muscles and Fascice of the Abdomen.
The Antero-lateral Muscles of the Abdomen 408
The Superficial Fascia 408
Obliquus Externus Abdominis . 409
Aponeurosis of the Obliquus
Externus Abdominis . 410
Subcutaneous Inguinal Ring . 410
The Intercrural Fibers . 410
The Inguinal Ligament . 411
The Lacunar Ligament . . 412
The Reflected Inguinal Liga-
ment 412
Ligament of Cooper . . . 412
Variations 412
Obliquus Internus Abdominis . . . 412
Variations 414
Cremaster 414
Transversus Abdominis 414
The Antero-lateral Muscles of the Abdomen —
.Transversus Abdominis —
Variations 414
Inguinal Aponeurotic Falx . . . 414
Rectus Abdominis 415
Pyramidalis 416
Variations 417
The Linea Alba 417
The Linese Semilunares 417
The Transversalis Fascia .... 418
The Abdominal Inguinal Ring . . . 418
The Inguinal Canal 418
Extraperitoneal Connective Tissue . . 418
The Deep Crural Arch 419
The Posterior Muscles of the Abdomen . . 419
The Fascia Covering the Quadratus
Lumborum 419
Quadratus Lumborum 420
Variations 420
The Muscles and Fascia of the Pelvis.
Pehac Fascia 420
Levator Ani 422
Coccygeus 424
The Muscles and Fascia of the Perineum.
Muscles of the Anal Region 424
The Superficial Fascia 424
The Deep Fascia 425
Ischiorectal Fossa 425
The Corrugator Cutis Ani .... 425
Sphincter Ani Externus 425
Sphincter Ani Internus 426
The ^Iuscles of the Urogenital Region in
the Male 426
Superficial Fascia 426
The Central Tendinous Point of the
Perineum 427
Transversus Perinsei Superficialis . . 427
Variations 427
Bulbocavernosus 42S
Ischiocavernosus 428
The Deep Fascia . . . . . . .428
Transversus Perinsei Profundus . . 429
Sphincter L'rethrae Membranace® . . 429
The Muscles of the L'rogenital Region in the
Female 430
Transversus Perinoei Superficialis . . 43o
Bulbocavernosus 430
Ischiocavernosus 430
Transversus Perinsei Profundus . . 431
The Fascia axd Muscles of the Upper
Extremity.
The Muscles Connecting the Upper Extremity
to the Vertebral Column.
Superficial Fascia 432
Deep Fascia 432
Trapezius 432
\'ariations 432
Latissimus Dorsi 432
Variations 434
Rhomboideus Major 434
Rhomboideus Minor 434
Variations 435
Levator scapulae 435
Variations 435
The Muscles Connecting the Upper Extremity to
the Anterior and Lateral Thoracic Walls.
Superficial Fascia 435
Pectoralis Major 436
Variations 437
Coracoclavicular Fascia 437
Pectoralis Minor 438
Variations 438
Subcla\-ius 438
^'ariations 438
Serratus Anterior '. 438
\'ariations 439
CONTENTS
15
The Muscles and Fascia of the Shoulder.
Deep Fascia 439
Deltoideus 439
Variations 440
Subscapular Fascia 440
Subscapularis 440
Supraspinatous Fascia 440
Supraspinatus 440
Infraspinatous Fascia 441
Infraspinatus 441
Teres Minor 441
Variations 442
Teres Major 442
The Muscles and Fasciae of the Arm.
Brachial Fascia 442
Coracobrachialis . 443
Variations 443
Biceps Brachii 443
Variations 444
Brachialis 444
Variations 444
Triceps Brachii 444
Variations 445
The Muscles and Fasciae of the Forearm.
Antibrachial Fascia 445
The Volar Antibrachial Muscles .... 445
The Superficial Group 446
Pronator Teres 446
Variations 446
Flexor Carpi Radialis .... 446
Variations 446
Palmaris Longus . . . . . . 446
Variations 446
Flexor Carpi Ulnaris .... 447
Variations 447
Flexor Digitorum Sublimis . . . 448
Variations 448
The Deep Group 448
Flexor Digitorum Profundus . 448
Fibrous Sheaths of the Flexor
Tendons 448
Variations 449
Flexor PoUicis Longus .... 449
Variations 449
Pronator Quadratus . . . . . 449
Variations 450
The Dorsal Antibrachial Muscles. . . .451
The Superficial Group 451
Brachioradialis 451
Variations 451
Extensor Carpi Radialis Longus . 452
Extensor Carpi Radialis Brevis . 452
Variations 452
Extensor Digitorum Communis . 452
Variations 454
Extensor Digiti Quinti Proprius . 454
Variations 454
Extensor Carpi L^lnaris .... 454
Variations 454
AnconiBUS 454
The Deep Group 454
Supinator 454
Abductor PoUicis Longus . . . 455
Variations 455
Extensor PoUicis Brevis . . . 455
Variations 455
Extensor PoUicis Longus . . . 455
Extensor Indicis Proprius . . . 456
Variations 456
Thii Muscles and Fascia: of the Hand.
Volar Carpal Ligament 456
Transverse Carpal Ligament 456
The Mucous Sheaths of the Tendons on the
Front of the Wrist 457
Dorsal Carpal Ligament 458
The Mucous Sheaths of the Tendons on the
Back of the Wrist 459
Palmar Aponeurosis 460
Superficial Transverse Ligament of the
Fingers 461
The Lateral Volar Muscles 461
Abductor PoUicis Brevis 461
Opponens PoUicis 461
Flexor PoUicis Brevis 461
Adductor PoUicis (Obliquus) . . . 462
Adductor PoUicis (Transversus) . . 462
Variations 462
The Medial Volar Muscles 462
Palmaris Brevis 463
Abductor Digiti Quinti 463
Flexor Digiti Quinti Brevis .... 464
Opponens Digiti Quinti 464
Variations 464
The Intermediate Muscles 464
Lumbricales 464
Variations 464
Interossei 464
Interossei Dorsales 464
Interossei Volares 465
The Muscles and Fasciae of the Lower
Extremity.
The Muscles and Fasciae of the Iliac Region.
The Fascia Covering the Psoas and Iliacus 466
Psoas Major 467
Psoas Minor 467
Iliacus 467
Variations 467
The Muscles and Fasciae of the Thigh.
The Anterior Femoral Muscles .... 467
Superficial Fascia 468
Deep Fascia 468
The Fossa Ovalis 469
Sartorius 470
Variations 470
Quadriceps Femoris 470
Rectus Femoris 470
Vastus Lateralis 470
Vastus Medialis 471
Vastus Intermedins 471
Articularis Genu 471
The Medial Femoral Muscles . . . .471
Gracilis 471
Pectineus 472
Adductor Longus 472
Adductor Brevis 473
Adductor Magnus 473
Variations 474
The Muscles of the Gluteal Region . . . 474
Gluteus Maximus 474
Bursae 474
Glutseus Medius 474
Variations 475
Glutseus Minimus 475
Variations 475
Piriformis 476
Variations 476
Tensor Fasciae Latte 476
Obturator Membrane 477
Obturator Internus 477
Gemelli 477
Gemellus Superior 477
Gemellus Inferior 477
Quadratus Femoris 477
Obturator Externus 477
The Posterior Femoral Muscles .... 478
Biceps Femoris 478
Variations 479
Semitendinosus , 479
Semimembranosus .... . 479
Variations .... . . 479
The Muscles and Fasciae of the Leg.
The Anterior Crural Muscles 480
Deep Fascia 480
Tibialis Anterior 480
Variations 480
16
CONTEXTS
The Anterior Crural Muscles —
Extensor Hallucis Longus .... 481
\"ariations 481
Extensor Digitorum Longus .... 481
\'ariation3 482
Peronspus Tertius 482
The Posterior Crural Muscles . . . 482
The Superficial Group 482
Gastrocnemius 482
\'ariatioiis 483
Soleus 483
Variations 483
Tendo Calcaneus 483
Plantaris 483
The Deep Group ....... 483
Deep Transverse Fascia . . . 483
Popliteus 484
Variations 485
Flexor Hallucis Longus .... 485
Variations 485
Flexor Digitorum Longus . . 485
Variations 485
Tibialis Posterior 485
The Lateral Crural Muscles 486
Peron;rus Longus 486
Peronajus Brevis 486
Variations 487
The FascicB Around the Ankle.
Transverse Crural Ligament ..... 488
Cruciate Crural Ligament 488
Laciniate Ligament , 489
Peroneal Retinacula 489
The Mucous Sheaths of the Tendons Around
the Ankle
The Muscles and Fasciae of the Foot.
489
The Dorsal Muscle of the Foot .... 490
Extensor Digitorum Brevis .... 490
^'ariations 490
The Plantar Muscles of the Foot . . . 490
Plantar Aponeurosis 490
The First Layer 491
Abductor Hallucis 491
Variations 491
Flexor Digitorum Brevis . . .491
Variations 492
Fibrous Sheaths of the Flexor
Tendons 492
Abductor Digiti Quinti .... 492
Variations 492
The Second Layer 493
Quadratus PlantiB 493
Variations 493
Lumbricales 493
Variations 493
The Third Layer 493
Flexor Hallucis Bre^ns .... 493
Variations 493
Adductor Hallucis 493
Variations 494
Flexor Digiti Quinti Bre^•is . . 494
The Fourth Layer 495
Interossei 495
Interossei Dorsales .... 495
Interossei Plantares . . . 495
ANGIOLOGY.
Structure of Arteries 498 | The Thoracic Cavitt.
Capillaries 499
Sinusoids 501 The Cavity of the Thorax . . .
Structure of Veins 591 The Upper Opening of the Thorax
The Lower Opening of the Thorax
524
524
524
The Blood.
General Composition of the Blood . . . 503
Blood Corpuscles 503
Colored or Red Corpuscles . . . 503
Colorfesg Corpuscles or Leukocytes 504
Development of the Vascular System.
Further Development of the Heart . . . 508
The Valves of the Heart 514
Further Development of the Arteries . 515
The Anterior Ventral Aortae . . .516
The Aortic Arches 516
The Dorsal Aortae 517
Further Development of the Veins . . 518
The Visceral Veins 518
The Parietal Veins 520
Inferior Vena Cava 520
Venous Sinuses of the Dura Mater . 522
The Pericardium.
Structure of the Pericardium 525
The Heart.
Size 526
Component Parts 526
Right Atrium 528
Sinus Venarum 528
Auricula 528
Right Ventricle 531
Left Atrium 533
Auricula 533
Left Ventricle 535
V^entricular Septum 535
Structure of the Heart 535
The Cardiac Cycle and the Actions of the
Valves 538
Peculiarities in the Vascular System in the
Fetus.
Fetal Circulation 540
Changes in the Vascular System at Birth . 542
THE ARTERIES.
The Pulmonary Arterj"
Relations
543
545
The Aorta.
The Ascending Aorta.
Relations
Branches
546
546
Branches of the Ascending Aorta —
The Coronarj' Arteries 546
Right Coronarj' Arterj- .... 546
Left Coronarj- Artery .... 547
Pecuharities 547
The Arch of the Aorta.
Relations 547
Peculiarities 548
CONTENTS
17
Branches 548
Peculiarities ' 548
The Innominate Artery , 548
Relations 548
Branches 549
ThjTeoidea Ima 549
Collateral Circulation 549
The Arteries of the Head and Neck.
The Common Carotid Artery.
Relations 549
Peculiarities 551
Collateral Circulation 551
The External Carotid Artery 551
Relations 552
Branches 552
Superior Thyroid Artery . . . 552
Relations 552
Branches 552
Lingual Artery 553
Relations 553
Branches 553
External Maxillary Artery . . . 553
Relations 554
Branches 554
Peculiarities 556
Occipital Artery 556
Course and Relations . . 556
Branches 556
Posterior Auricular Artery . . . 557
Branches 557
Ascending Pharyngeal Artery . . 557
Branches 558
Superficial Temporal Artery . . 558
Relations 558
Branches 558
Internal Maxillary Artery . . . 559
Branches 560
The Triangles of the Neck 562
Anterior Triangle 563
Inferior Carotid or Muscular Tri-
angle 563
Superior Carotid or Carotid Tri-
angle 564
Submaxillary or Digastric Tri-
angle 564
Suprahyoid Triangle .... 565
Posterior Triangle 565
Occipital Triangle 565
Subclavian Triangle 565
The Internal Carotid Artery 566
Course and Relations 567
Cer\ical Portion 567
Petrous Portion 567
Cavernous Portion 567
Cerebral Portion . 567
Peculiarities 567
Branches 568
Caroticotympanic 568
Artery of the Pterygoid Canal . . 568
Cavernous 568
Hypophyseal 568
Semilunar 568
Anterior Meningeal 568
Ophthalmic artery 568
Branches 568
Anterior Cerebral Artery . . . 571
Branches 571
Middle Cerebral Artery . . . 572
Branches 573
Posterior Communicating Artery . 573
Anterior Choroidal Artery . . . 574
The Arteries of the Brain.
The Ganglionic System
The Cortical Arterial System
575
575
The Arteries of the Upper Extremity.
The Subclavian Artery.
First Part of the Right Subclavian Artery . 576
Relations 576
First Part of the Left Subclavian Artery . 577
Relations 577
Second and Third Parts of the Subclavian
Artery 577
Relations 577
Relations 577
Peculiarities 577
Collateral Circulation 578
Branches ^78
Vertebral Artery 578
Relations 578
Branches 579
Thyrocervical Trunk 581
Branches 581
Peculiarities 583
Internal Mammary Artery .... 584
Relations 584
Branches 584
The Costocervical Trunk .... 585
The Axilla.
Boundaries 585
Contents 586
The Axillary Artery 586
Relations 586
Collateral Circulation 587
Branches 587
The Highest Thoracic Artery . . 587
The Thoracoacromial Artery . 588
The Lateral Thoracic Artery . . 588
The Subscapular Artery . . 588
The Posterior Humeral Circumflex
Artery 589
The Anterior Humeral Circumflex
Artery 589
Peculiarities 589
The Brachial Artery 589
Relations 589
The Anticubital Fossa 589
Peculiarities 590
Collateral Circtilation 590
Branches 590
The Arteria Profunda Brachii . . 591
The Nutrient Artery .... 591
The Superior Ulnar Collateral
Artery 591
The Inferior Ulnar Collateral
Artery 592
Muscular Branches 592
The Anastomosis Around the Elbow- j oint 592
The Radial Artery 592
Relations 592
Peculiarities 594
Branches 594
Radial Recurrent Artery 594
Muscular 594
Volar Carpal 594
Superficial Volar 594
Dorsal Carpal 594
Arteria Princeps PoUicis . . 595
Arteria Volaris Indicis Radialis 595
Deep Volar Arch 595
Volar Metacarpal Arteries . . 595
Perforating 595
Recurrent 595
The Ulnar Artery 595
Relations 595
Peculiarities 596
Branches 596
Anterior Ulnar Recurrent Artery . 596
Posterior Ulnar Recurrent Artery . 596
Common Interosseous Artery . 596
Muscular 598
Volar Carpal 598
Dorsal Carpal 598
Deep Volar 598
Superficial Volar 598
Relations 598
18
CONTENTS
The Arteries of the Trunk.
The Descending Aorta.
The Thoracic Aorta 598
Relations 599
Peculiarities 599
Branches 600
Pericardial 600
Bronchial 600
Esophageal 600
Mediastinal 600
Intercostal Arteries 600
Branches ... . 691
Subcostal Arteries 601
Superior Phrenic 601
The Abdominal Aorta 602
Relations . 603
Collateral Circulation 603
Branches 603
The Celiac Artery 603
Relations 603
The Superior Mesenteric Artery . 606
Branches 607
The Inferior Mesenteric Artery . 609
Branches 610
The Middle Suprarenal Arteries . 610
The Renal Arteries 610
The Internal Spermatic Arteries . 611
The Ovarian Arteries . . . .611
The Inferior Phrenic Arteries . . 612
The Lumbar Arteries . . . .612
The Middle Sacral Artery ... 613
The Common Iliac Arteries,
Peculiarities 614
Collateral CLrculatioa 614
The Hypogastric Artery 614
Relations 614
Peculiarities 615
Collateral Circulation 615
Branches 615
Superior Vesical Artery .... 615
Middle Vesical Artery .... 615
Inferior Vesical Artery . . . . 615
Middle Hemorrhoidal Artery . . 615
Uterine Artery 615
Vaginal Artery 616
Obturator Artery 616
Branches 616
Peculiarities 617
Internal Pudendal Artery . . . 617
Relations 618
Peculiarities 618
Branches 618
Inferior Gluteal Artery .... 620
Branches 620
Lateral Sacral Arteries . . . .621
Superior Gluteal Artery . . . 622
The External Iliac Artery 622
Relations 622
Collateral Circulation 622
Branches 622
Inferior Epigastric Artery . . . 623
Branches 623
Peculiarities 623
Deep Iliac Circumflex Artery . . 623
The Arteries of the Lower Extremity.
The Femoral Artery.
The Femoral Sheath 625
The Femoral Triangle 626
The Adductor Canal 627
Relations of the Femoral Artery .... 627
Peculiarities of the Femoral Artery . . . 629
Collateral Cii'culation 629
Branches 629
Superficial Epigastric Artery . . . 629
Superficial Iliac Circumflex Artery . . 629
Superficial External Pudendal Artery . 629
Deep External Pudendal Artery . . 629
Muscular 629
Profunda Femoris Artery .... 629
Relations 630
Peculiarities 630
Branches 630
Highest Genicular Artery . . . .631
The Popliteal Fossa 631
Boundaries . .■ , 631
Contents 632
The Popliteal Artery 632
Relations 632
Peculiarities 633
Branches 633
Superior IMusculur .... 633
Sural Arteries 633
Cutaneous Branches . . . 633
Superior Genicular Arteries . . 633
Middle Genicular Artery . . 633
Inferior Genicular Arteries . . 633
The Anastomosis Around the Knee-
joint 634
The Anterior Tibial Artery 634
Relations 635
Peculiarities 635
Branches 635
Posterior Tibial Recurrent Arterj- . 635
Fibular Artery 635
Anterior Tibial Recurrent Artery . 635
Muscular Branches 635
Anterior Medial Malleolar Arterj- . 635
Anterior Lateral Malleolar Artery . 635
The Arteria Dorsalis Pedis 636
Relations 636
Peculiarities 636.
Branches ; 637
Lateral Tarsal Artery .... 637-
Medial Tarsal Artery . . . .637
Arcuate Artery 637
Deep Plantar Artery .... 637
The Posterior Tibial Artery 637
Relations 637
Peculiarities 638
Branches 638
Peroneal Artery 638
Peculiarities 638
Branches 638
Nutrient Artery 638
Muscular Branches 639
Posterior Medial Malleolar Artery 639
Communicating Branch .... 639
Medial Calcaneal 639
Medial Plantar Artery .... 639
Lateral Plantar Artery .... 639
Branches 640
The Pulmonary Veins
The Systemic Veins.
The Veins of the Heart.
Coronary Sinus 642
Tributaries 642
The Veins of the Head and Neck.
The Veins of the Exterior of the Head and
Face 644
The Frontal Vein 644
THE VEINS.
642
The Veins of the Exterior of the Head
and
The Supraorbital Vein 645
The Angular Vein
645
The Anterior Facial Vein
645
Tributaries
645
The Superficial Temporal Vein
645
Tributaries ....
645
The Pterygoid Plexus . .
645
The Internal Maxillary Vein .
646
The Posterior Facial Vein
646
The Posterior Auricular Vein
646
The Occipital Vein
646
CONTENTS
19
The Veins of the Neck
The External Jugular Vein
Tributaries ...
The Posterior External Jugular Vein
The Anterior Jugular Vein
The Internal Jugular Vein
Tributaries
The Vertebral Vein
Tributaries
The Diploic Veins .
The Veins of the Brain
The Cerebral Veins
The External Veins
The Superior Cerebral Vein
The Middle Cerebral Vein .
The Inferior Cerebral Vein .
The Internal Cerebral Veins
The Great Cerebral Vein
The Cerebellar Veins ....
The Sinuses of the Dura Mater. Ophthalmic
Veins and Emissary Veins
The Superior Sagittal Sinus .
The Inferior Sagittal Sinus .
The Straight Sinus ....
The Transverse Sinuses .
The Occipital Sinus ....
The Confluence of the Sinuses .
The Cavernous Sinuses .
The Ophthalmic Veins
The Superior Ophthalmic Vein
The Inferior Ophthalmic Vein
The Intercavernous Sinuses
The Superior Petrosal Sinus
The Inferior Petrosal Sinus
The Basilar Plexus
The Emissary Veins .
646
646
647
647
647
648
648
649
650
651
652
652
652
652
652
652
653
653
653
654
654
655
655
657
658
658
658
658
659
659
659
659
659
660
660
The Veins of the Upper Extremity and
Thorax.
The Superficial Veins of the Upper Extremity 660
Digital Veins 660
The Cephalic Vein 661
The Accessory Cephalic Vein . . 662
The Basilic Vein 662
The Median Antibrachial Vein . . . 662
The Deep Veins of the Upper Extremity . 663
Deep Veins of the Hand 663
Deep Veins of the Forearm .... 663
The Brachial Veins 663
The Axillary Vein 663
The Subclavian Vein 664
Tributaries 664
The Veins of the Thorax 664
The Innominate Veins 664
The Right Innominate Vein . . 664
The Left Innominate Vein . . . 666
Tributaries 666
Peculiarities . . ... 666
The Internal Mammary Veins . . . 666
The Inferior Thyroid Veins .... 666
The Highest Intercostal Vein . . . 666
The Superior Vena Cava .... 666
Relations 667
The Azygos Vein 667
Tributaries 667
The Hemiazygos Veins . . 667
The Veins of the Thora.x —
The Azygos Vein —
The Accessory Hemiazygos
Veins 667
The Bronchial Veins 667
The Veins of the Vertebral Column . . . 667
The External Vertebral Venous Plexuses 668
The Internal Vertebral Venous Plexuses 668
The Basivertebral Veins 668
The Intervertebral Veins .... 669
The Veins of the Medulla Spinalis . . 669
The Veins of the Lower Extremity, Abdomen,
and Pelvis.
The Superficial Veins of the Lower Extremity 669
The Dorsal Digital Veins 669
The Great Saphenous Vein .... 669
Tributaries . 670
The Small Saphenous Vein .... 670
The Deep Veins of the Lower Extremity . 671
The Plantar Digital Veins . . . .671
The Posterior Tibial Veins .... 672
The Anterior Tibial Veins .... 672
The Popliteal Vein 672
The Femoral Vein 672
The Deep Femoral Vein . . . 672
The Veins of the Abdomen and Pelvis . . 672
The External Iliac Vein 672
Tributaries 672
The Hypogastric Veins 673
Tributaries 673
The Hemorrhoidal Plexus .... 676
The Pudendal Plexus 676
The Vesical Plexus 676
The Dorsal Veins of the Penis . . . 676
The Uterine Plexuses 676
The Vaginal Plexuses 677
The Common Iliac Veins .... 677
The Middle Sacral Veins ... 677
Peculiarities 677
The Inferior Vena Cava 677
Relations 678
Peculiarities 678
Applied Anatomy 678
Tributaries 678
Lumbar Veins 678
Spermatic Veins .... 678
Ovarian Veins 679
Renal Veins 679
Suprarenal Veins .... 679
Inferior Phrenic Veins . . . 679
Hepatic Veins 680
The Portal System of Veins.
The Portal Vein 681
Tributaries 681
The Lienal Vein 681
Tributaries 681
The Superior Mesenteric Vein . . 682
Tributaries 682
The Coronary Vein 682
The Pyloric Vein 682
The Cystic Vein 682
The Parumbilical Veins .... 682
THE LYMPHATIC SYSTEM.
The Development of the Lymphatic Vessels 683
Lymphatic Capillaries 684
Distribution 684
Lymphatic Vessels 687
Structure of Lymphatic Vessels .... 687
The Lymph Glands 688
Structure of Lymph Glands .... 688
Hemolymph Nodes 690
Lymph .690
The Thoracic Duct.
The Cisterna Chyli 691
Tributaries 691
The Right Lymphatic Duct 691
Tributaries 692
The Lymphatics
OF the
Neck.
Head, Face, and
The Lymph Glands of the Head .
The Occipital Glands .
The Posterior Auricular Glands
The Anterior Auricular Glands
The Parotid Glands . . .
The Facial Glands
The Deep Facial Glands .
The Lingual Glands
The Retropharyngeal Glands
The Lymphatic Vessels of the Scalp
The Lymphatic Vessels of the Auricula
and External Acoustic Meatus
The Lymphatic Vessels of the Face
692
692
693
693
693
694
694
694
694
694
694
695
20
CONTENTS
The Lymph Glands of the Head —
The Lymphatic Vessels of the Nasal
Cavities 695
The Lymphatic Vessels of the Mouth . 695
The Lymphatic Vessels of the Palatine
Tonsil 695
The Lymphatic Vessels of the Tongue . 696
The Lymph Glands of the Neck .... 697
The Submaxillary Glands .... 697
The Submental or Suprahyoid Glands . 697
The Superficial Cervical Glands . . . 697
The Anterior Cervical Glands . . . 697
The Deep Cervical Glands . . . .697
The Lymphatic Vessels of the Skin and
Muscles of the Neck 698
The Lymphatics of the Upper Extremity.
The Lymph Glands of the Upper Extremity 699
The Superficial Lymph Glands . . . 699
The Deep Lymph Glands .... 699
The Axillary Glands .... 699
The Lymphatic Vessels of the L^pper
Extremity 700
The Superficial Lymphatic Vessels . . 700
The Deep Lymphatic Vessels . . .701
The Lymphatics of the Lower Extremity.
The Lymph Glands of the Lower Extremity 701
The Anterior Tibial Gland .... 701
The Popliteal Glands 701
The Inguinal Glands 702
The Lymphatic Vessels of the Lower
Extremity 703
The Superficial Lymphatic Vessels . . 703
The Deep Lymphatic Vessels . . . 703
The Lymphatics of the Abdomen and Pelvis.
The Lymph Glands of the Abdomen and
Pelvis 703
The Parietal Glands 703
The External Iliac Glands ... 703
The Common Iliac Glands . . . 704
The Epigastric Glands .... 704
The Iliac Circumflex Glands . . 704
The Hypogastric Glands . 704
The Sacral Glands 704
The Lumbar Glands .... 705
The Lymphatic Vessels of the Abdomen and
Pelvis 706
The Superficial Vessels 706
The Deep Vessels 706
The Lymphatic Vessels of the
Perineum and External Genitals 706
The Visceral Glands 706
The Gastric Glands 706
The Hepatic Glands .... 706
The Pancreaticolienial Glands . . 706
The Superior Mesenteric Glands . . 709
The Mesenteric Glands .... 709
The Ileocolic Glands .... 709
The Mesocolic Glands .... 709
The Inferior Mesenteric Glands 710
The Lymphatic Vessels of the Abdominal
and Pelvic Viscera 710
The Lymphatic Vessels of the Abdomina
and Pelvic Viscera —
The Lymphatic Vessels of the Subdia-
phragmatic Portions of the Digestive
Tube . 710
The Lymphatic Vessels of the Stomach 710
The Lymphatic Vessels of the Duodenum 710
The Lymphatic Vessels of the Jejunum
and Ileum 710
The Lymphatic Vessels of the Vermiform
Process and Cecum 710
The Lymphatic Vessels of the Colon . 711
The Lymphatic Vessels of the Anus,
Anal Canal, and Rectum . . . .711
The Lymphatic Vessels of the Liver . 711
The Lymphatic Vessels of the Gall-
bladder 711
The Lymphatic Vessels of the Pancreas 711
The Lymphatic Vessels of the Spleen and
Suprarenal Glands 711
The Lymphatic Vessels of the Urinary
Organs 712
The Lymphatic Vessels of the
Kidney 712
The Lymphatic Vessels of the Ureter 71 2
The Lymphatic Vessels of the
Bladder 712
The Lymphatic Vessels of the
Prostate 713
The Lymphatic Vessels of the
Urethra 713
The Lymphatic Vessels of the Repro-
ductive Organs 713
The Lymphatic Vessels of the
Testes . . 713
The Lymphatic Vessels of the
Ductus Deferens 713
The Lymphatic Vessels of the Ovary 714
The Lymphatic Vessels of the
Uterine Tube 714
The Lymphatic Vessels of the
Uterus 714
The Lymphatic Vessels of the
Vagina 714
The Lymphatics of the Thorax.
The Parietal Lymph Glands 715
The Sternal Glands 715
The Intercostal Glands 715
The Diaphragmatic Glands .... 715
The Superficial Lymphatic Vessels of the
Thoracic Wall 715
The Lymphatic Vessels of the Mamma. 715
The Deep Lymphatic Vessels of the Thoracic
Wall 716
The Visceral Lymph Glands . . . 717
The Anterior Mediastinal Glands . . 717
The Posterior Mediastinal Glands . . 717
The Tracheobronchial Glands . . . 717
The Lymphatic Vessels of the Thoracic
Viscera 718
The Lymphatic Vessels of the Heart . 718
The Lymphatic Vessels of the Lungs 718
The Lymphatic Vessels of the Pleura . 719
The Lymphatic Vessels of the Thymus 719
The Lymphatic Vessels of the Eso-
phagus 719
NEUROLOGY.
Structure of the Nervous System.
Neuroglia 722
Nerve Cells 722
Nerve Fibers 724
Wallerian Degeneration 727
Non-medullated Fibers 728
Structure of the Peripheral Nerves and
Ganglia • 728
Origins and Terminations of Nerves . . . / 29
Ganglia 730
Neuron Theory 732
Fasciculi, Tracts or Fiber Systems . . 732
Development of the Nervous System.
The Medulla Spinalis 733
The Spinal Nerves 735
The Brain 736
CONTENTS
21
The Brain—
The Hind-brain or Rhombencephalon . 738
The Mid-brain or Mesencephalon . . 741
The Fore-brain or Prosencephalon 741
The Diencephalon 742
The Telencephalon 743
The Commissures 746
Fissures and Sulci 747
The Cranial Nerves 748
The Spinal Cord or Medulla Spinalis.
Enlargements 751
Fissures and Sulci 752
The Anterior Median Fissure 752
The Posterior Median Sulcus . . 752
The Internal Structure of the Medulla
Spinalis 753
The Gray Substance 753
Structure of the Gray Substance . 755
The White Substance 758
Nerve Fasciculi 759
Roots of the Spinal Nerves 764
The Anterior Nerve Root .... 764
The Posterior Root 764
The Brain or Encephalon.
General Considerations and Divisions
766
The Hind-brain or Rhombencephalon.
The Medulla Oblongata 767
The Anterior Median Fissure . . 767
The Posterior Median Fissure . . . 767
Internal Structure of the Medulla
Oblongata 775
The Cerebrospinal Fasciculi . 775
Gray Substance of the Medulla
Oblongata 779
Inferior Peduncle 782
Formatio Reticularis .... 784
The Pons 785
Structure 785
The Cerebellum 788
Lobes of the Cerebellum 788
Internal Structure of the Cerebellum . 791
The White Substance . . . .791
Projection Fibres . .791
The Gray Substance .... 794
Microscopic Appearance of the
Cortex 794
The Fourth Ventricle 797
Angles 797
Lateral Boundaries 797
Choroid Plexuses 798
Openings in the Roof 798
Rhomboid Fossa 798
The Mid-brain or Mesencephalon.
The Cerebral Peduncles 800
Structure of the Cerebral Peduncles . 801
The Gray Substance .... 802
The White Substance .... 803
The Corpora Quadrigemina 805
Structure of the Corpora Quadrigemina 806
The Cerebral Aqueduct 806
The Fore-brain or Prosencephalon.
The Diencephalon 807
The Thalamencephalon 808
Structure 810
Connections 810
The Metathalamus 811
The Epithalamus 812
The Hypothalamus 812
The Optic Chiasma 814
The Optic Tracts 814
The Third Ventricle ....".. 815
The Interpeduncular Fossa .... 816
The Telencephalon 817
The Cerebral Hemispheres 817
The Longitudinal Cerebral Fissure . 818
The Surfaces of the Cerebral Hemi-
spheres 818
The Lateral Cerebral Fissure . . .819
The Central Sulcus 819
The Parietooccipital Fissure .... 820
The Calcarine Fissure 820
The Cingulate Sulcus 820
The Collateral Fissure 820
The Sulcus Circularis 821
The Lobes of the Hemispheres . . . 821
The Frontal Lobe 821
The Parietal Lobe 822
The Occipital Lobe 823
The Temporal Lobe 823
The Insula 825
The Limbic Lobe 825
The Rhinencephalon 826
The Olfactory Lobe 826
The Interior of the Cerebral Hemi-
spheres 827
The Corpus Callosum .... 828
The Lateral Ventricles .... 829
The Fornix 838
The Interventricular Foramen . . 840
The Anterior Commissure . . . 840
The Septum Pellucidum .... 840
The choroid Plexus of the Lateral
Ventricle 840
Structure of the Cerebral Hemi-
spheres 842
Structure of the Cerebral Cortex . . 845
Special Types of Cerebral Cortex . . 847
Weight of Encephalon 848
Cerebral Localization 849
Composition and Central Connections of the Spinal
Nerves.
The Intrinsic Spinal Reflex Paths . . . 850
Sensory Pathways from the Spinal Cord
to the Brain 851
Composition and Central Connections of the Cranial
Nerves.
The Hypoglossal Nerve 855
The Accessory Nerve 855
The Vagus Nerve 855
The Glossopharyngeal Nerve 856
The Acoustic Nerve 857
The Vestibular Nerve 860
The Facial Nerve 861
The Abducens Nerve 861
The Trigeminal Nerve 862
The Trochlear Nerve 863
The Oculomotor Nerve 863
The Optic Nerve 864
The Olfactory Nerves 866
Pathways from the Brain to the Spinal Cord.
The Motor Tract 870
The Meninges of the Brain and Medulla Spinalis.
The Dura Mater 872
The Cranial Dura Mater .... 872
Processes 873
Structure 875
The Spinal Dura Mater 875
Structure 876
The Arachnoid 876
The Cranial Part 876
The Spinal Part 876
Structure 876
The Subarachnoid Cavity .... 876
The Subarachnoid Cisternse .... 876
The Arachnoid Villi 878
Structure 878
The Pia Mater 878
The Cranial Pia Mater 879
The Spinal Pia Mater 879
The Ligamentum Denticulatum . . 880
22
CONTENTS
The Cerebrospinal Fluid
The Cranial Nerves.
The Olfactory Nerves
The Optic Nerve.
The Optic Chiasma
The Optic Tract
The Oculomotor Nerve
The Trochlear Nerve .
The Trigeminal Nerve.
The Semilunar Ganglion .
The Ophthalmic Nerve
The Lacrimal Nerve .
The Frontal Nerve
The Nasociliary Nerve
The Ciliary Ganglion .
The Maxillary Nerve .
Branches ....
The Middle Meningeal Nerve
The Zygomatic Nerve
The Sphenopalatine .
The Posterior Superior Alveolar
The Middle Superior Alveolar
The Anterior Superior Alveolar
The Inferior Palpebral
The External Nasal ...
The Superior Labial
The Sphenopalatine Ganglion
The Mandibular Nerve ....
Branches
The Nervus Spinosus
The Internal Pterygoid Nerve
The Masseteric Nerve
The Deep Temporal Nerves
The Buccinator Nerve .
The External Pterygoid Nerve
The Auriculotemporal Nerve
The Lingual Nerve .
The Inferior Alveolar Nerve
The Otic Ganglion
The Submaxillary Ganglion
Trigeminal Nerve Reflexes ...
The Abducent Nerve
880
881
883
884
884
885
886
887
887
887
888
888
889
889
889
889
890
890
891
891
891
891
891
891
893
894
894
894
894
895
895
895
895
895
896
897
898
899
899
The Ganglion Nodosum —
The Meningeal Branch
The Auricular Branch
The Pharyngeal Branch .
The Superior Laryngeal Nerve
The Recurrent Nerve
The Superior Cardiac Branches
The Inferior Cardiac Branches
The Anterior Bronchial Branches
The Posterior Bronchial Branches
The Esophageal Branches
The Gastric Branches
The Celiac Branches
The Hepatic Branches
911
911
911
912
912
912
912
913
913
913
913
913
913
The Accessory Nerve.
The Facial Nerve.
The Greater Superficial Petrosal Nerve . 903
The Nerve to the Stapedius 904
The Chorda Tympani Nerve 904
The Posterior Auricular Nerve .... 905
The Digastric Branch 905
The Stylohyoid Branch 905
The Temporal Branches 905
The Zygomatic Branches 905
The Buccal Branches 905
The Mandibular Branch 905
The Cervical Branch 905
The Acoustic Nerve.
The Cochlear Nerve 906
The Vestibular Nerve 906
The Glossopharyngeal Nerve.
The Superior Ganglion 908
The Petrous Ganglion 908
The Tympanic Nerve 909
The Carotid Branches 909
The Pharyngeal Branches .... 909
The Muscular Branches 909
The Tonsillar Branches 909
The Lingual Branches 909
The Vagus Nerve.
The Jugular Ganglion 911
The Ganglion Nodosum 911
The Cranial Part 913
The Spinal Part 913
The Hypoglossal Nerve.
Branches of Communication 915
Branches of Distribution 916
The Meningeal Branches .... 916
The Descending Ramus 916
The Thyrohyoid Branch 916
The Muscular Branches 916
The Spinal Nerves.
Nerve Roots
. 916
The Anterior Root
. 916
The Posterior Root . . .
. 916
The Spinal Ganglia
. 917
Structure
. 917
Connections -with SjTnpathetic
. 920
Structure
. 920
Divisions of the Spinal Nerves
. 921
The Posterior Divisions .
. 921
The Cervical Nerves
. 921
The Thoracic Nerves
. 923
The Lumbar Nerves
. 924
The Sacral Nerves
. 924
The Coccygeal Nerve
. 925
The Anterior Divisions
. 925
The Cervical Nerves
. 925
The Cervical Plexus
. 925
Great Auricular Nerve
. 926
Cutaneous Cervical N
Brve 927
Supraclavicular Nerve
s . 928
Communicantes Cervicales 928
Phrenic Nerve .
. 928
The Brachial Plexus .
. 930
Relations .
. 931
Dorsal Scapular Nerv
e . 932
Suprascapular Nerve
. 932
Nerve to Subclavius
. 933
Long Thoracic Nerve
. 933
Anterior Thoracic Nerves 933
Subscapular Nerves
. 933
Thoracodorsal Nerve
. 934
Axillarv Nerve
. 934
Musculocutaneous Nerve 935
Medial Antibrachial C
uta-
neous Nerve
. 937
Medial Brachial Cut£
i-
neous Nerve
. 937
Median Nerve .
. 938
L'lnar Nerve
. 939
Radial Nerve .
. 943
The Thoracic Nerves
. 944
First Thoracic Nerve
. 945
Upper Thoracic Nerves
. 945
Lower Thoracic Nerves
. 948
The Lumbosacral Plexus
. 948
The Lumbar Nerves
. 948
The Lumbar Plexus
. 949
Iliohypogastric N(
jrve 950
Ilioinguinal Nerve
. 952
Genitofemoral Ne
rve 953
Lateral Femoral C
uta-
neous Nerve
. 953
Obturator Ner
ve
. 953
CONTENTS
23
Dmsions of the Spinal Nerves —
The Anterior Divisions —
The Lumbosacral Plexus —
The Lumbar Nerves —
The Lumbar Plexus —
Accessory Obturator
Nerve ....
Femoral Nerve
Saphenous Nerve.
The Sacral and Coccygeal
Nerves
The Sacral Plexus
Relations
Nerve to Quadratus
Femoris and
Gemellus Inferior
Nerve to Obturator
Internus and Ge-
mellus Superior .
Nerve to Piriformis
Superior
Nerve .
Inferior
Nerve .
Posterior
Gluteal
Gluteal
Femoral
Cutaneous Nerve
Sciatic Nerve
Tibial Nerve
Lateral Plantar Nerve
Common Peroneal
Nerve ....
Deep Peroneal Nerve
Superficial Peroneal
Nerve ....
The Pudendal Plexus
Perforating Cuta-
neous Nerve
Pudendal Nerve
Anococcygeal Nerve
955
955
956
957
957
957
957
958
959
959
959
959
960
960
963
964
965
966
966
967
967
968
The Cephalic Portion of the Sympathetic
System.
The Internal Carotid Plexus .... 977
The Cavernous Plexus 978
The Cervical Portion of the Sympathetic
Systern.
The Superior Cervical Ganglion
Branches
The Middle Cervical Ganglion
Branches
The Inferior Cervical Ganglion
Branches
978
978
979
979
980
981
The Sympathetic Nerves.
The Cranial Sympathetics 970
The Sacral Sympathetics 973
The Thoracolumbar Svmpathetics . . . 974
The Sympathetic Trunks 976
Connections with the Spinal Nerves . . 976
Development 977
The Thoracic Portion of the Sympathetic
System.
The Greater Splanchnic Nerve .... 981
The Lesser Splanchnic Nerve .... 981
The Lowest Splanchnic Nerve .... 981
The Abdominal Portion of the Sympathetic
System .... 982
The Pelvic Portion of the Sympathetic
System ....
984
The Great Plexuses of the Sympathetic System.
The Cardiac Plexus 984
The Celiac Plexus 985
Phrenic Plexus 985
Hepatic Plexus 986
Lienal Plexus 986
Superior Gastric Plexus 987
Suprarenal Plexus 987
Renal Plexus ......... 987
Spermatic Plexus 987
Superior Mesenteric Plexus . . . 987
Abdominal Aortic Plexus .... 987
Inferior Mesenteric Plexus .... 987
The Hypogastric Plexus 987
The Pelvic Plexuses 987
The Middle Hemorrhoidal Plexus . . 988
The Vesical Plexus 988
The Prostatic Plexus 988
The Vaginal Plexus 989
The Uterine Plexus 989
THE ORGANS OF THE SENSES AND THE COMMON INTEGUMENT.
The Peripheral Organs of the Special
Senses.
The Organs of Taste.
Structure 991
The Organ of Smell.
The External Nose 992
Structure 992
The Nasal Cavity 994
The Lateral Wall 994
The Medial Wall 995
The Mucous Membrane .... 996
Structure 996
The Accessory Sinuses of the Nose . . . 998
The Frontal Sinuses 998
The Ethmoidal Air Cells .... 998
The Sphenoidal Sinuses 998
The Maxillary Sinus 999
The Organ of Sight.
Development 1001
The Tunics of the Eye 1005
The Fibrous Tunic 1005
The Sclera 1005
Structure 1006
The Cornea 1006
Structure 1007
The Tunics of the Eye —
The Vascular Tunic 1009
The Choroid 1009
Structure 1010
The Ciliary Body 1010
Structure 1011
The Iris 1012
Structure 1013
Membrana Pupillaris .... 1014
The Retina 1014
Structure 1015
The Refracting Media 1018
The Aqueous Humor 1018
The Vitreous Body 1018
The Crystalline Lens 1019
Structure 1020
The Accessory Organs of the Eye . . . 1021
The Ocular Muscles . . . . . . 1021
Levator Palpebrae Superior! s . . 1021
The Recti 1022
Obliquus Oculi Superior . . . 1022
Obliquus Oculi Inferior . . . 1023
The Fascia Bulb 1024
The Orbital Fascia 1025
The Eyebrows 1025
The Eyelids 1025
The Lateral Palpebral Commis-
^ sure 1025
The Eyelashes 1025
Structure of the Eyelids . . 1025
The Tarsal Glands 1026
24
CONTENTS
The Accessory Organs of the Eye —
Structure of the Tarsal Glands
The Conjunctiva
The Palpebral Portion
The Bulbar Portion
The Lacrimal Apparatus
The Lacrimal Gland
Structure
The Lacrimal Ducts
The Lacrimal Sac .
Structure
The Nasolacrimal Duct
The Organ of Hearing.
1026
1026
1027
1027
1028
1028
1028
1028
1028
1029
1029
Development 1029
The External Ear 1033
The Auricula or Pinna 1033
Structure 1034
The External Acoustic Meatus . 1036
Relations 1037
The Middle Ear or Tympanic Cavity . 1037
The Tegumental ^yall or Roof . . . 1038
The Jugular Wall or Floor .... 1038
The Membranous or Lateral Wall 1038
The Tympanic Membrane .... 1039
Structure 1039
The Labvrinthic or Medial Wall . . 1040
The Mastoid or Posterior Wall . . 1042
The Carotid or Anterior Wall . 1042
The Auditorj- Tube 1042
The Auditory Ossicles 1044
The Malleus 1044
The Incus 1044
The Stapes 1045
Articulations of the Auditory Ossicles 1045
Ligaments of the Ossicles .... 1045
The Muscles of the Tympanic Cavity 1046
The Tensor Tympani .... 1046
The Stapedius 1046
The Internal Ear or Labyrinth .... 1047
The Osseous Labyrinth 1047
The Internal Ear or Labyrinth —
The Osseous Labyrinth —
The Vestibule
The Bony Semicircular Canals
The Cochlea
The Membranous Labyrinth
The Utricle ....
The Saccule ....
The Semicircular Ducts
Structure
The Ductus Cochlearis
The BasUar Membrane
The Spiral Organ of Corti
Hair Cells ....
1047
1049
1050
1051
1051
1052
1052
1052
1054
1056
1056
1057
Peripheral Terminations of Xerves of General
Sensations.
Free Nerve-endings 1059
Special End-organs 1059
End-bulbs of Krause 1060
Tactile Corpuscles of Grandry .... 1060
Pacinian Corpuscles 1060
Corpuscles of Golgi and Mazzoni . . 1061
Tactile Corpuscles of Wagner and Meissner 1061
Corpuscles of Ruffini 1061
Neurotendinous Spindles 1061
Neuromuscular Spindles 1061
The Comon Integument.
The Epidermis, Cuticle, or Scarf Skin . . 1062
The Corium, Cutis Vera, Dermis, or True
Skin 1065
Development 1066
The Appendages of the Skin.
The NaUs 1066
The Hairs 1067
The Sebaceous Glands 1069
The Sudoriferous or Sweat Glands . . . 1070
SPLANCHNOLOGY.
The Respiratory Apparatus.
Development
107]
The Larynx.
The Cartilages of the Larynx .... 1073
The Thyroid Cartilage .
1073
The Cricoid Cartilage
1074
The Arytenoid Cartilage
1075
The Corniculate Cartilages
1075
The Cuneiform Cartilages
1075
The Epiglottis . . .
1075
Structure
1076
The Ligaments of the Larynx
1076
The Extrinsic Ligaments
1076
The Intrinsic Ligaments
1077
The Interior of the Larynx .
1078
The Ventricular Folds .
1079
The Vocal Folds . . .
1079
The Ventricle of the Larynx
1080
The Rima Glottidis . .
1080
The Muscles of the Larynx .
1081
Cricothyreoideus
1081
Cricoarytsenoideus Posterior
1082
Cricoarytsenoideus Lateralis
1082
Arytaenoideus ....
1082
Thyreoarytaenoideus
1083
The Trachea and Bronchi.
Relations 1084
The Right Bronchus 1085
The Left Bronchus 1085
Structure 1086
The Pleurce.
Reflections of the Pleura 1088
Pulmonary Ligament 1090
Structure of Pleura 1090
The Mediastinum.
Superior Mediastinum 1090
Anterior Mediastinum 1092
Middle Mediastinum 1092
Posterior ^Mediastinum 1093
The Lungs.
The Apex of the Lungs 1094
The Base of the Lungs 1094
Surfaces of the Lungs 1094
Borders of the Lungs 1096
Fissures and Lobes of the Lungs . . . 1096
The Root of the Lung 1097
Di\-isions of the Bronchi 1097
Structure of the Lungs 1098
The Digestive Apparatus.
The Digestive Tube 1100
The Development of the Digestive
Tube 1101
The Mouth 1101
The Salivary Glands .... 1102
The Tongue 1102
The Palatine TonsOs .... 1103
The Further Development of the
Digestive Tube 1103
The Rectum and Anal Canal . 1108
CONTENTS
25
The Mouth.
The Abdomen.
The Vestibule of the Mouth 1110
The Mouth Cavity Proper 1110
Structure 1110
The Lips 1111
The Labial Glands 1111
The Cheeks 1112
Structure 1112
The Gums 1112
The Palate 1112
The Hard Palate 1112
The Soft Palate 1112
The Teeth 1112
General Characteristics 1114
The Permanent Teeth 1115
The Canine Teeth 1117
The Premolar or Bicuspid Teeth . 1118
The Molar Teeth 1118
The Deciduous Teeth 1118
Structure of the Teeth 1118
Development of the Teeth .... 1121
Development of the Deciduous
Teeth 1122
Development of the Permanent
Teeth 1124
Eruption of the Teeth 1124
The Tongue 1125
The Root of the Tongue .... 1125
The Apex of the Tongue . . . . 1125
The Dorsum of the Tongue . . . 1125
The Papilla of the Tongue . . . . 1126
The Muscles of the Tongue . . . 1128
Genioglossus 1129
Hyoglossus 1129
Chondroglossus 1130
Styloglossus 1130
Longitudinalis Linguae Superior 1130
Longitudinalis Linguae Inferior 1130
Transversus Linguae .... 1130
Verticalis Linguae 1131
Structure of the Tongue . . . 1131
Glands of the Tongue 1131
The Salivary Glands 1132
The Parotid Gland 1132
Structures within the Gland . . 1134
The Parotid Duct 1134
Structure 1134
The Submaxillary Gland . . . . 1135
The Submaxillary Duct . . . 1135
The Sublingual Gland 1136
Structure of the Salivary Gland . . 1136
Accessory Glands 1137
The Fauces.
The Glossopalatine Arch ....
1137
The Pharyngopalatine Arch ....
1137
The Palatine Tonsils
1137
Structure
1139
The Palatine Aponeurosis ....
1139
The Muscles of the Palate .
1139
Levator Veli Palatini .
1139
Tensor Veli Palatini . . .
1139
Musculus U\'ulse ....
1139
Glossopalatinus ....
1139
Paryngopalatinus ....
1139
The Pharynx.
The Nasal Part of the Pharynx .
1141
The Oral Part of the Pharynx
1142
The Laryngeal Part of the Pharynx
1142
The Muscles of the Pharj'nx
1142
Constrictor Pharyngis Inferior .
1142
Constrictor Pharyngis Medius .
1142
Constrictor Pharyngis Superior
1142
Stylopharyngeus
. 1142
Salpingopharyngeus
. 1142
Structure of the Pharynx ....
. 1143
The Esophagus.
Relations
. 1145
Structure
. 1146
Boundaries of the Abdomen 1147
The Apertures in the Walls of the Abdomen 1147
Regions of the Abdomen 1147
The Peritoneum .1149
Vertical Dispositions of the Main Peri-
toneal Cavity 1150
Vertical Disposition of the Omental
Bursa 1152
Horizontal Disposition of the Peri-
toneum 1153
In the Pelvis 1153
In the Lower Abdomen . . . 1154
In the Upper Abdomen . . . 1155
The Omenta 1156
The Mesenteries 1157
The Peritoneal Recesses or Fossae . . 1158
The Duodenal Fossae .... 1159
The Cecal Fossffi 1160
The Intersigmoid Fossa . . . 1161
The Stomach.
Openings of the Stomach 1161
Curvatures of the Stomach 1162
Surfaces of the Stomach 1162
Component Parts of the Stomach . . . 1163
Position of the Stomach 1163
Interior of the Stomach 1164
Pyloric Valve 1164
Structure of the Stomach 1164
The Gastric Glands 1166
The Small Intestine.
The Duodenum 1169
Relations 1169
The Jejunum and Ileum 1170
Meckel's Diverticulum 1172
Structure 1172
The Large Intestine.
The Cecum 1177
The Vermiform Process or Appendix . 1178
Structure 1179
The Colic Valve 1179
The Colon 1180
The Ascending Colon 1180
The Transverse Colon 1180
The Descending Colon 1181
The Iliac Colon 1182
The Sigmoid Colon 1182
The Rectum 1183
Relations of the Rectum . . . . 1184
The Anal Canal 1184
Structure of the Colon 1184
The Liver.
Surfaces of the Liver 1188
Fossae of the Liver 1191
Lobes of the Liver 1191
Ligaments of the Liver 1192
Fixation of the Liver 1193
Development of the Liver 1193
Structure of the Liver 1195
Excretory Apparatus of the Liver . . . 1197
The Hepatic Duct 1197
The Gall-bladder 1197
Relations 1197
Structure 1198
The Common BUe Duct .... 1198
Structure 1199
The Pancreas.
Relations 1200
The Pancreatic Duct 1202
Development of the Pancreas .... 1202
Structure 1203
26
CONTENTS
The Urogenital Apparatus.
Development of the Urinary and Generative Organs
The Pronephros and Wolffian Duet . . 1205
The Mesonephros, Miillerian Duct, and
Genital Gland 1205
The Miillerian Ducts 1206
Genital Glands 1207
The Ovary 1207
The Testis 1210
Descent of the Ovaries 1211
The Metanephros and the Permanent
Kidney 1211
The Urinary Bladder 1212
The Prostate 1213
External Organs of Generation . . . . 1213
The Urethra , 1215
The Urinary Organs.
The Kidneys 1215
Relations 1215
Surfaces 1215
Borders 1218
Extremities 1219
Fixation of the Kidney .... 1220
General Structure of the Kidney . . 1220
The Ureters 1225
The Ureter Proper 1226
Structure 1227
Variations 1227
The Urinary Bladder 1227
The Empty Bladder 1227
The Distended Bladder 1228
The Bladder in the Child .... 1229
The Eemale Bladder . . . . . 1230
The Ligaments of the Bladder . . . 1231
The Interior of the Bladder . . . 1231
Structure 1232
Abnormalities 1233
The Male Urethra 1234
The Prostatic Portion 1234
The Membranous Portion .... 1235
The Cavernous Portion 1235
Structure 1235
Congenital Defects 1235
The Female Urethra 1236
Structure 1236
Th Male Genital Organs.
The Testes and their Coverings .... 1236
The Scrotum 1237
The Intercrural Fascia 1238
The Cremaster Muscle 1238
The Infundibuliform Fascia . . . 1239
The Tunica Vaginalis 1239
The Inguinal Canal 1239
The Spermatic Cord 1239
Structure of the Spermatic Cord . 1239
The Testes 1240
The Epididymis 1242
Appendages of the Testis and Epi-
didymis 1242
The Tunica Vaginalis . . 1242
The Tunica Albuginea . . 1242
The Tunica Vasculosa . . 1243
Structure 1243
Peculiarities 1245
The Ductus Deferens 1245
The Ductuli Aberrantes .... 1246
Paradidymis 1246
Structure 1246
The Vesiculae Seminales 1246
Structure 1247
The Ejaculatory Ducts 1247
Structure 1247
The Penis 1247
The Corpora Cavernosa Penis . . . 1248
The Corpus Cavernosum Urethrse . 1248
Structure of the Penis 1250
The Prostate 1251
Structure 1253
The Bulbourethral Glands 1253
Structure 1253
The Female Genital Organs.
The Ovaries 1254
The Epoophoron 1255
The Paroophoron . - 1255
Structure 1255
Vesicular Ovarian Follicles .... 1256
Discharge of the 0\'um 1256
Corpus Luteum 1256
The Uterine Tube 1257
Structure 1257
The Uterus 1258
The Body 1259
The Cervix 1259
The Interior of the Uterus .... 1260
The Ca\ity of the Body . . . 1260
The Canal of the Cervix . . . 1260
The Ligaments of the Uterus . . . 1260
Structure 1262
The Vagina 1264
Relations 1264
Structure 1264
The External Organs 1264
The Mons Pubis 1265
The Labia Majora 1265
The Labia Minora 1265
The Clitoris 1266
The Vestibule 1266
The Bulb of the Vestibule .... 1266
The Greater Vestibular Glands . . 1266
The Mammae 1267
The Mammary Papilla or Nipple . . 1267
Development 1267
Structure 1267
The Ductless Glands.
The Thyroid Gland.
Development 1270
Structure 1271
The Parathyroid Glands.
Development 1272
Structure .... 1273
The Thymus.
Development 1273
Structure 1274
The Hypophysis Cerebri.
Development 1276
The Pineal Body.
Structure 1277
The Chromaphil and Cortical Systems.
Development 1277
The Suprarenal Glands 1278
Development 1278
Relations 1278
Accessory Suprarenals 1279
Structure 1279
Glomus Caroticum 1281
Glomus Coccygeum 1281
The Spleen.
Development 1282
Relation 1282
Structure 1283
CONTENTS
27
SURFACE ANATOMY AND SURFACE MARKINGS.
Surface Anatomy of the Head and Neck.
The Bones 1287
The Joints and Muscles 1288
The Arteries . . , 1290
Surface Markings of Special Regions of the Head
and Neck.
The Cranium 1291
The Scalp 1291
Bony Landmarks 1291
The Brain • . . 1292
Vessels 1294
The Face 1294
External Maxillary Artery .... 1294
Trigeminal Nerve 1295
Parotid Gland 1295
The Nose 1296
The Mouth 1296
The Eye 1299
The Ear 130C
The Tympanic Antrum 1301
The Neck 1301
Muscles 1302
Arteries 1302
Veins 1303
Nerves 1303
Submaxillary Gland 1303
Surface Anatomy of the Back.
Bones 1303
Muscles 1304
Surface Markings of the Back.
Bony Landmarks 1305
Medulla Spinalis 1306
Spinal Nerves 1307
Surface Anatomy of the Thorax.
Bones 1307
Muscles 1307
Mamma 1308
Surface Markings of the Thorax.
Bony Landmarks 1308
Diaphragm 1309
Surface Lines 1309
Pleurae 1309
Lungs 1310
Trachea 1311
Esophagus 1311
Heart 1311
Arteries 1312
Veins 1312
Surface Anatomy of the Abdomen.
Skin 1313
Bones 1313
Muscles 1313
Vessels 1313
Viscera 1313
Surface Markings of the Abdomen.
Bony Landmarks 1315
Muscles 1315
Surface Lines 1315
Stomach 1317
Duodenum 1319
Small Intestine 1319
Cecum and Vermiform Process .... 1319
Ascending Colon 1319
Transverse Colon ' . . . 1319
Descending Colon 1320
IUac Colon 1320
Liver • 1320
Pancreas 1320
Spleen 1320
Kidneys 1320
Ureters 1321
Vessels 1321
Nerves 1322
Surface Anatomy of the Perineum.
Skin 1322
Bones 1322
Muscles and Ligaments 1322
Surface Markings of the Perineum.
Rectum and Anal Canal 1322
Male Urogenital Organs 1323
Female Urogenital Organs 1323
Surface Anatomy of the Upper Extremity.
Skin 1325
Bones 1326
Articulations 1327
Muscles 1327
Arteries 1331
Veins 1331
Nerves "!.... 1331
Surface Markings of the Upper Extremity.
Bony Landmarks . . 1331
Articulations 1331
Muscles 1332
Mucous Sheaths 1334
Arteries 1334
Nerves 1335
Surface Anatomy of the Lower Extremity.
Skin 1336
Bones 1336
Articulations 1338
Muscles 1338
Arteries 1341
Veins 1342
Nerves 1342
Surface Markings of the Lower Extremity.
Bony Landmarks 1342
Articulations 1343
Muscles 1343
Mucous Sheaths 1343
Arteries 1343
Veins 1346
Nerves 1346
ANATOMICAL BIBLIOORAPHY
INDEXES.
Anatomical Bibliography of the Concilium Bibliographicum.
Bibliographic Service; "Wistar Institute of Anatomy, 1917-
Bibliographie Anatomique, 1893-
Index Medicus, 1879-
Index Catalogue of the Library of the Surgeon-General's Office, U. S. Army,
1880-
Jahresberichte iiber die Fortschritte der Anatomic und Physiologic, 1856-1894.
Jahresberichte iiber die Fortschritte der Anatomic und Entwicklungsgeschichte,
1895-
JOURNALS.
The Anatomical Record. 1906-
The American Journal of Anatomy, 1901-
Anatomische Hefte, 1892-
Anatomischer Anzeiger, 1886-
Archives d 'Anatomic IMicroscopique, 1897-
Archiv fiir Anatomic und Physiologic, 1795-
Archiv fiir Entwicklungsmechanik der Organismcn, 1894-
Archiv fiir ^Nlicroskopische Anatomic, 1865-
Archivo Italiano di Anatomia e di Embriologia, 1902-
Biological Bulletin, 1900-
Brain, 1878-
Bibliographie Anatomique, 1893-
Contributions to E^mbryology, Carnegie Institution of Washington, 1914—
Comptcs Rendus de I'Association dcs Anatomistes, 1899-
Gcgenbaur's ]\Iorphologisches Jahrbuch, 1876-
International ]Monatsschrift fiir Anatomic und Histologic, 1884-
The Journal of Anatomy and Physiology, 1867-
Journal of Comparative Neurology, 1891-
Journal de 1 'Anatomic et de Physiologic, etc., 1864-
Journal of Experimental Zoology, 1904-
Journal of ^Morphology, 1887-
Le Nevraxe, 1900-
Morphologische Arbeiten, 1892-1898.
Petrus Camper Nederlandschc Bijdragen tot de Anatomic, 1902-
Proceedings of the Royal Society, Series B.
Quarterly Journal of ^Microscopical Science, 1853-
Zeitschrift fiir ^Morphologic und Anthropologic, 1899-
Zeitschrift fiir Wissenschaftliche Mikroskopie, 1884:-
( xxviii)
ANATOMY OF THE HUMAN BODY
INTRODUCTION.
THE term human anatomy comprises a consideration of the various structures
which make up the human organism. In a restricted sense it deals merely
with the parts which form the fully developed individual and which can be ren-
dered evident to the naked eye by various methods of dissection. Regarded from
such a standpoint it may be studied by two methods: (1) the various structures
may be separately considered^ — systematic anatomy; or (2) the organs and tissues
may be studied in relation to one another — topographical or regional anatomy.
It is, however, of much advantage to add to the facts ascertained by naked-
eye dissection those obtained by the use of the microscope. This introduces
two fields of investigation, viz., the study of the minute structure of the various
component parts of the body — ^histology — and the study of the human organism
in its immature condition, i. e., the various stages of its intrauterine develop-
ment from the fertilized ovum up to the period when it assumes an independent
existence — embryology. Owing to the difficulty of obtaining material illustrating
all the stages of this early development, gaps must be filled up by observations
on the development of lower forms — comparative embryology, or by a consideration
of adult forms in the line of human ancestry — comparative anatomy. The direct
application of the facts of human anatomy to the various pathological conditions
which may occur constitutes the subject of applied anatomy. Finally, the appre-
ciation of structures on or immediately underlying the surface of the body is
frequently made the subject of special study — surface anatomy.
Systematic Anatomy.^ — ^The various systems of which the human body is
composed are grouped under the following headings:
1. Osteology — the bony system or skeleton.
2. Syndesmology — the articulations or joints.
3. Myology — the muscles. With the description of the muscles it is convenient
to include that of the fasciae which are so intimately connected with them.
4. Angiology — the vascular system, comprising the heart, bloodvessels, lymphatic
vessels, and lymph glands.
5. Neurology — the nervous system. The organs of sense may be included in
this system.
6. Splanchnology — the visceral system. Topographically the viscera form
two groups, viz., the thoracic viscera and the abdomino-pelvic viscera. The
heart, a thoracic viscus, is best considered with the vascular system. The rest
3 ( 33 )
34 INTRODUCTION
of the viscera may be grouped according to their functions: (a) the respiratory
apparatus; (6) the digestive apparatus; and (c) the urogenital apparatus. Strictly
speaking, the third subgroup should include only such components of the
urogenital apparatus as are included within the abdomino-pelvic cavity, but it
is convenient to study under this heading certain parts which lie in relation to
the surface of the body, e. g., the testes and the external organs of generation.
For descriptive purposes the body is supposed to be in the erect posture, with
the arms hanging by the sides and the palms of the hands directed forward. The
median plane is a vertical antero-posterior plane, passing through the center of the
trunk. This plane will pass approximately through the sagittal suture of the skull,
and hence any plane parallel to it is termed a sagittal plane. A vertical plane at
right angles to the median plane passes, roughly speaking, through the central
part of the coronal suture or through a line parallel to it; such a plane is known as
a frontal plane or sometimes as a coronal plane. A plane at right angles to both
the median and frontal planes is termed a transverse plane.
The terms anterior or ventral, and posterior or dorsal, are employed to indicate
the relation of parts to the front or back of the body or limbs, and the terms
superior or cephalic, and inferior or caudal, to indicate the relative levels of different
structures; structures nearer to or farther from the median plane are referred to as
medial or lateral respectively.
The terms superficial and deep are strictly confined to descriptions of the
relative depth from the surface of the various structures; external and internal
are reserved almost entirely for describing the Walls of cavities or of hollow
viscera. In the case of the limbs the words proximal and distal refer to the
relative distance from the attached end of the limb.
EMBRYOLOGY.
THE term Embryology, in its widest sense, is applied to the various changes
which take place during the growth of an animal from the egg to the adult
condition: it is, however, usually restricted to the phenomena which occur before
birth. Embryology may be studied from two aspects: (1) that of ontogeny, which
deals only with the development of the individual; and (2) that of phylogeny,
which concerns itself with the evolutionary history of the animal kingdom.
In vertebrate animals the development of a new being can only take place when
a female germ cell or ovum has been fertilized by a male germ cell or spermatozoon.
The ovum is a nucleated cell, and all tiie complicated changes by which the various
tissues and organs of the body are formed from it, after it has been fertilized, are
the result of two general processes, viz., segmentation and differentiation of cells.
Thus, the fertilized ovum undergoes repeated segmentation into a number of cells
which at first closely resemble one another, but are, sooner or later, differentiated
into two groups: (1) somatic cells, the function of which is to build up the various
tissues of the body; and (2) germinal cells, which become imbedded in the sexual
glands — the ovaries in the female and the testes in the male — and are destined for
the perpetuation of the species.
Having regard to the main purpose of this work, it is impossible, in the space
available in this section, to describe fully, or illustrate adequately, all the phenom-
ena which occur in the different stages of the development of the human body.
Only the principal facts are given, and the student is referred for further details
to one or other of the text-books^ on human embryology.
THE ANIMAL CELL.
All the tissues and organs of the body originate from a microscopic structure
(the fertilized ovum), which consists of a soft jelly-like material enclosed in a
membrane and containing a vesicle or small spherical body inside which are one
or more denser spots. This may be regarded as a complete cell. All the solid
tissues consist largely of cells essentially similar to it in nature but differing in
external form.
In the higher organisms a cell may be defined as "a nucleated mass of proto-
plasm of microscopic size." Its two essentials, therefore, are: a soft jelly-like
material, similar to that found in the ovum, and usually styled cytoplasm, and a
small spherical body imbedded in it, and termed a nucleus. Some of the unicellular
protozoa contain no nuclei but granular particles which, like true nuclei, stain with
basic dyes. The other constituents of the ovum, viz., its limiting membrane and
the denser spot contained in the nucleus, called the nucleoliis, are not essential to
the type cell, and in fact many cells exist without them.
Cytoplasm (protoplasm) is a material probably of variable constitution during
life, but yielding on its disintegration bodies chiefly of proteid nature. Lecithin
and cholesterin are constantly found in it, as well as inorganic salts, chief among
' Manual of Human Embryologj-, Keibel and Mall; Handbuch der vergleichenden und experimentellen Entwickel-
uagslehre der Wirbeltiere, Oskar Hertwig; Lehrbuch der Entwickelungsgeschichte, Bonnet; The Physiology of
Reproduction, Marshall.
(35)
36
EMBRYOLOGY
which are the phosphates and chlorides of potassium, sodium, and calcium. It is
of a semifluid, viscid consistence, and probably colloidal in nature. The living
CNtoplasm appears to consist of a homogeneous and structureless ground-substance
in which are embedded granules of various t^-pes. The mitochondria are the most
constant type of granule and vary in form from granules to rods and threads.
Their fmiction is unknowTi. Some of the granules are proteid in nature and prob-
ably essential constituents; others are fat, glycogen, or pigment granules, and are
regarded as adventitious material taken in from without, and hence are styled
cell-inclusions or paraplasm. ^Vhen, however, cells have been "fixed" by reagents
a fibrillar or granular appearance can often be made out under a high power of the
microscope. The fibrils are usually arranged in a network or reticulum, to which
the term spongioplasm is applied, the clear substance in the meshes being termed
hyaloplasm. The size and shape of the meshes of the spongioplasm vary in different
cells and in different parts of the same cell. The relative amounts of spongioplasm
and hyaloplasm also vary in different cells, the latter preponderating in the young
cell and the former mcreasing at the expense of the hyaloplasm as the cell grows.
Such appearances in fixed cells are no indication whatsoever of the existence of
Cell wall
Nuclear
membrane
Vacuole
Centrosome consisting of cen-
trospliere enclosing two cen-
irioles
Nucleolus
Net-knot cf chromatin form-
ing a pseudo-nucleolus
Chromatin network
Cell-inclusions {paraplasm)
Fia. 1. — Diagram of a cell. (Modified from Wilson.)
similar structures in the living, although there must have been something in the
living cell to give rise to the fixed structures. The peripheral layer of a cell is in
all cases modified, either by the formation of a definite cell membrane as in the ovum,
or more frequently in the case of animal cells, by a transformation, probably
chemical in nature, which is only recognizable by the fact that the surface of the
cell behaves as a semipermeable membrane.
Nucleus. — The nucleus is a minute body, imbedded in the protoplasm, and
usually of a spherical or oval form, its size having little relation to that of the cell.
It is surrounded by a well-defined wall, the nuclear membrane; this encloses the
nuclear substance {iniclear matrix), which is composed of a homogeneous material
in which is usually embedded one or two nucleoli. In fixed cells the nucleus seems
to consist of a clear substance or karyoplasm and a network or karyomitome. The
former is probably of the same nature as the hyaloplasm of the cell, but the latter,
which forms also the wall of the nucleus, differs from the spongioplasm of the cell
substance. It consists of fibers or filaments arranged in a reticular manner. These
filaments are composed of a homogeneous material known as linin, which stains
with acid dyes and contains embedded in its substance particles which have a
strong affinity for basic dyes. These basophil granules have been named chromatin
THE ANIMAL CELL 37
or basichromatin and owe their staining properties to the presence of nucleic acid.
Within the nuclear matrix are one or more highly refracting bodies, termed nucleoli,
connected with the nuclear membrane by the nuclear filaments. They are regarded
as being of two kinds. Some are mere local condensations ("net-knots") of the
chromatin; these are irregular in shape and are termed pseudo-nucleoli ; others are
distinct bodies differing from the pseudo-nucleoli both in nature and chemical
composition; they may be termed true nucleoli, and are usually found in resting
cells. The true nucleoli are oxyphil, i. e., they stain with acid dyes.
]\Iost living cells contain, in addition to their protoplasm and nucleus, a small
particle which usually lies near the nucleus and is termed the centrosome. In the
middle of the centrosome is a minute body called the centriole, and surrounding this
is a clear spherical mass known as the centrosphere. The protoplasm surround-
ing the centrosphere is frequently arranged in radiating fibrillar rows of granules,
forming what is termed the attraction sphere.
Reproduction of Cells. — Reproduction of cells is effected either by direct or by
indirect division. In reproduction by direct division the nucleus becomes constricted
in its center, assuming an hour-glass shape, and then divides into two. This is fol-
lowed by a cleavage or division of the whole protoplasmic mass of the cell; and thus
two daughter cells are formed, each containing a nucleus. These daughter cells are
at first smaller than the original mother cell; but they grow, and the process
may be repeated in them, so that multiplication may take place rapidly. Indirect
divsion or karyokinesis (karyomitosis) has been observed in all the tissues — genera-
tive cells, epithelial tissue, connective tissue, muscular tissue, and nerve tissue.
It is possible that cell division may always take place by the indirect method.
The process of indirect cell division is characterized by a series of complex
changes in the nucleus, leading to its subdivision; this is followed by cleavage
of the cell protoplasm. Starting with the nucleus in the quiescent or resting stage,
these changes may be briefly grouped under the four following phases (Fig. 2).
1. Prophase. — The nuclear network of chromatin filaments assumes the form
of a twisted skein or spirem, while the nuclear membrane and nucleolus disappear.
The convoluted skein of chromatin divides into a definite number of V-shaped
segments or chromosomes. The number of chromosomes varies in different animals,
but is constant for all the cells in an animal of any given species; in man the number
is given by Flemming and Duesberg as twenty-four.^ Coincidently with or pre-
ceding these changes the centriole, which usually lies by the side of the nucleus,
undergoes subdivision, and the two resulting centrioles, each surrounded by a
centrosphere, are seen to be connected by a spindle of delicate achromatic fibers
the achromatic spindle. The centrioles move away from each other — one toward
either extremity of the nucleus — and the fibrils of the achromatic spindle are cor-
respondingly lengthened. A line encircling the spindle midway between its ex-
tremities or poles is named the equator, and around this the V-shaped chromosomes
arrange themselves in the form of a star, thus constituting the mother star or
monaster.
2. Metaphase. — Each V-shaped chromosome now undergoes longitudinal
cleavage into two equal parts or daughter chromosomes, the cleavage commencing
at the apex of the V and extending along its divergent limbs.
3. Anaphase. — The daughter chromosomes, thus separated, travel in opposite
directions along the fibrils of the aclu'omatic spindle toward the centrioles, around
which they group themselves, and thus two star-like figures are formed, one at
either pole of the achromatic spindle. This constitutes the diaster. The daughter
chromosomes now arrange themselves into a skein or spirem, and eventually form
the network of chromatin which is characteristic of the resting nucleus.
Dr. J. Duesberg, Anat. Anz., Band xxviii, S. 475.
38
EMBRYOLOGY
4. Telophase. — The cell protoplasm begins to appear constricted around the
equator of the achromatic spindle, where double rows of granules are also sometimes
seen. The constriction deepens and the original cell gradually becomes divided
into two new cells, each with its owii nucleus and centrosome, which assume the
ordinary positions occupied by such structures in the resting stage. The nuclear
membrane and nucleolus are also differentiated during this phase.
II
VI
VII
VIII
I "i<f]
^^^- 2-.— Diagram showing the changes which occur in the centrosomes and nucleus of a cell in the process of mitotic
division, (bchafer.) / to ///, prophase; IV, metaphase; V and VI, anaphase; VII and VIII. telophase.
THE OVUM.
The ova are developed from the primitive germ cells which are imbedded in
the^ substance of the ovaries. Each primitive germ cell gives rise, by repeated
divisions, to a number of smaller cells termed obgonia, from which the ova or
primary oocjrtes are developed.
Human ova are extremely minute, measuring about 0.2 mm. in diameter, and
are enclosed within the egg follicles of the ovaries; as a rule each follicle contains
THE OVUM
39
a single ovum, but sometimes two or more are present.^ By the enlargement and
subsequent rupture of a follicle at the surface of the ovary, an ovum is liberated and
conveyed by the uterine tube to the cavity of the uterus. Unless it be fertilized
it undergoes no further development and is discharged from the uterus, but if
fertilization take place it is retained within the uterus and is developed into a
new being.
In appearance and structure the ovum (Fig. 3) differs little from an ordinary
cell, but distinctive names have been applied to its several parts; thus; the cell
substance is known as the yolk or ooplasm, the nucleus as the germinal vesicle, and
the nucleolus as the germinal spot. The ovum is enclosed within a thick, trans-
FiG. 3. — Human ovum examined fresh in the liquor folliculi. (Waldeyer.) The zona pellucida is seen aa a thick
clear girdle surrounded by the cells of the corona radiata. The egg itself shows a central granular deutoplasmie area
and a peripheral clear layer, and encloses the germinal vesicle, in which is seen the germinal spot.
parent envelope, the zona striata or zona pellucida, adhering to the outer surface
of which are several layers of cells, derived from those of the follicle and collectively
constituting the corona radiata.
Yolk. — The yolk comprises (1) the cytoplasm of the ordinary animal cell with its
spongioplasm and hyaloplasm; this is frequently termed the formative yolk; (2)
the nutritive yolk or deutoplasm, which consists of numerous rounded granules of
fatty and albuminoid substances imbedded in the cytoplasm. In the mammalian
ovum the nutritive volk is extremelv small in amount, and is of service in nourish-
See description of the ovary on a future page.
40 EMBRYOLOGY
ing the embryo in the early stages of its development only, whereas in the egg
of the bird there is sufficient to supply the chick with nutriment throughout
the whole period of incubation. The nutritive yolk not only varies in amount,
but in its mode of distribution within the egg; thus, in some animals it is almost
uniformly distributed throughout the cytoplasm; in some it is centrally placed and
is surrounded by the cytoplasm; in others it is accumulated at the lower pole of the
ovum, while the cytoplasm occupies the upper pole. A centrosome and centriole
are present and lie in the immediate neighborhood of the nucleus.
Germinal Vesicle. — The germinal vesicle or nucleus is a large spherical body
which at first occupies a nearh' central position, but becomes eccentric as the growth
of the ovum proceeds. Its structure is that of an ordinary cell-nucleus, viz., it
consists of a reticulum or karyomitome, the meshes of which are filled with
karyoplasm, while connected with, or imbedded in, the reticulum are a number
of chromatin masses or chromosomes, which may present the appearance of a
skein or may assume the form of rods or loops. The nucleus is enclosed by a
delicate nuclear membrane, and contains in its interior a well-defined nucleolus
or germinal spot.
Coverings of the Ovum.^ — The zona striata or zona pellucida (Fig. 3) is a thick
membrane, which, under the higher powers of the microscope, is seen to be radially
striated. It persists for some time after fertilization has occurred, and may serve
for protection during the earlier stages of segmentation. It is not yet determined
whether the zona striata is a product of the cytoplasm of the ovum or of the cells
of the corona radiata, or both.
The corona radiata (Fig. 3) consists or two or three strata of cells; they are
derived from the cells of the follicle, and adhere to the outer surface of the zona
striata when the ovum is set free from the follicle; the cells are radially arranged
around the zona, those of the innermost layer being columnar in shape. The
cells of the corona radiata soon disappear; in some animals they secrete, or
are replaced by, a layer of adhesive protein, which may assist in protecting and
nourishing the ovum.
The phenomena attending the discharge of the ova from the follicles belong
more to the ordinary functions of the ovary than to the general subject of embry-
ology, and are therefore described with the anatomy of the ovaries.^
Maturation of the Ovum. — Before an ovum can be fertilized it must undergo
a process of maturation or ripening. This takes place previous to or immediately
after its escape from the follicle, and consists essentially of an unequal subdivision
of the ovum (Fig. 4) first into two and then into four cells. Three of the four
cells are small, incapable of further development, and are termed polar bodies or
polocytes, while the fourth is large, and constitutes the mature ovum. The process
of maturation has not been observed in the human ovum, but has been carefully
studied in the ova of some of the lower animals, to which the following description
applies.
It was pointed out on page 37 that the number of chromosomes found in the
nucleus is constant for all the cells in an animal of any given species, and that in
man the number is probably twenty-four. This applies not only to the somatic
cells but to the primitive ova and their descendants. For the purpose of illustrating
the process of maturation a species may be taken in which the number of nuclear
chromosomes is four (Fig. 5). If an ovum from such be observed at the beginning
of the maturation process it will be seen that the number of its chromosomes is
apparently reduced to two. In reality, however, the number is doubled, since
each chromosome consists of four granules grouped to form a tetrad. During the
metaphase (see page 37) each tetrad divides into two dyads, which are equally
' See description of the ovary on a future page.
THE OVUM
41
distributed between the nuclei of the two cells formed by the first division of the
ovum. One of the cells is almost as large as the original ovum, and is named
the secondary oocyte; the other is small, and is termed the first polar body. The
fpn
F:g. 4. — Formation of polar bodies in Asterias glacialis. (Slightly modified from Hertwig.) In I the polar spindle
(sp) has advanced to the surface of the egg. In // a small elevation (ph') is formed which receives half of the spindle.
In /// the elevation is constricted ofT, forming the first polar body (p6'), and a second spindle is formed. In IV is
seen a second elevation which in T' has been constricted off as the second polar body (pt>'). Out of the remainder of
the spindle (/.p't in VI) the female pronucleus is developed.
secondary oocyte now undergoes subdivision, during which each dyad divides and
contributes a single chromosome to the nucleus of each of the two resulting cells.
Primary oocyte
Primary oocyte
(comtnencing
maturation)
Secondary
oocyte
¥ \ First j>oUr
body
Mature
ovum
Polar bodies
Fig. 5. — Diagram showing the reduction in number of the chromosomes in the process of maturation of the ovum.
This second division is also unequal, producing a large cell which constitutes the
mature ovum, and a small cell, the second polar body. The first polar body fre-
quently divides while the second is being formed, and as a final result four cells
42
EMBRYOLOGY
are produced, viz., the ^mature ovum and three polar bodies, each of which con-
tains two chromosomes, i. e., one-half the number present in the nuclei of the
somatic cells of members of the same species. The nucleus of the mature ovum
is termed the female pronucleus.
THE SPERMATOZOON.
The spermatozoa or male germ cells are developed in the testes and are present
in enormous numbers in the seminal fluid. Each consists of a small but greatly
modified cell. The human spermatozoon possesses a head, a neck, a connecting
piece or body, and a tail (Fig. 6).
Head
Connecting 'piece
'Perforator
) yeck
Tail'.
End-piece
y Head-cap
Anterior centriole
Posterior centriole
•Spiral thread
'Mitochondria sheath
•Terminal disc
■Axial filament
Fig. 6. — Human spermatozoon. Diagrammatic. A. Surface view. B. Profile ^^ew. In C the head, neck,
and connecting piece are more highly magnified.
The head is oval or elliptical, but flattened, so that when viewed in profile
it is pear-shaped. Its anterior two-thirds are covered by a layer of modified proto-
plasm, which is named the head-cap. This, in some animals, e. g., the salamander,
is prolonged into a barbed spear-like process or perforator, which probabl}^ facilitates
the entrance of the spermatozoon into the ovum. The posterior part of the head
exhibits an affinity for certain reagents, and presents a transversely striated appear-
ance, being crossed by three or four dark bands. In some animals a central rod-
like filament extends forward for about two-thirds of the length of the head, while
in others a rounded body is seen near its center. The head contains a mass of
THE SPERMATOZOON 43
chromatin, and is generally regarded as the nucleus of the cell surrounded by a
thin envelope.
The neck is less constricted in the human spermatozoon than in those of some
of the lower animals. The anterior centriole, represented by two or three rounded
particles, is situated at the junction of the head and neck, and behind it is a band
of homogeneous substance.
The connecting piece or body is rod-like, and is limited behind by a terminal
disk. The posterior centriole is placed at the junction of the body and neck and,
like the anterior, consists of two or three rounded particles. From this centriole
an axial filament, surrounded by a sheath, runs backward through the body and
tail. In the body the sheath of the axial filament is encircled by a spiral thread,
around which is an envelope containing mitochondria granules, and termed the
mitochondria sheath.
The tail is of great length, and consists of the axial thread or filament, sur-
rounded by its sheath, which may contain a spiral thread or may present a striated
appearance. The terminal portion or end-piece of the tail consists of the axial
filament only.
Primary cocyie Primary spermatocyte
Mature
ovum
Secondary f^ r-\ (^ f\ Secondary
oocyte v. J \^ K J V J spermatocytes
0_^0JD 0_0_0_0
Polar bodies Spermatids
Fig. 7. — Scheme showing analogies in the process of maturation of the ovum and the development of the spermatids
(young spermatozoa).
Krause gives the length of the human spermatozoon as between 52fj. and 62/^,
the head measuring 4 to 5/x, the connecting piece 6/x, and the tail from 41 /x to 52 /x.
By virtue of their tails, which act as propellers, the spermatozoa are capable of
free movement, and if placed in favorable surroundings, e. g., in the female pas-
sages, will retain their vitality and power of fertilizing for several days. In certain
animals, e. g., bats, it has been proved that spermatozoa retained in the female
passages for several months are capable of fertilizing.
The spermatozoa are developed from the primitive germ cells which have become
imbedded in the testes, and the stages of their development are very similar to those
of the maturation of the ovum. The primary germ cells undergo division and
produce a number of cells termed spermatogonia, and from these the primary
spermatocytes are derived. Each primary spermatocyte divides into two secondary
spermatocytes, and each secondary spermatocyte into two spermatids or young
spermatozoa; from this it will be seen that a primary spermatocyte gives rise to
jour spermatozoa. On comparing this process with that of the maturation of the
ovum (Fig. 7) it will be observed that the primary spermatocyte gives rise to
two cells, the secondary spermatocytes, and the primary oocyte to two cells, the
secondary oocyte and the first polar body. Again, the two secondary sperma-
44
EMBRYOLOGY
tocytes by their subdivision give origin to four spermatozoa, and the secondary
oocyte and first polar body to four cells, the mature ovum and three polar bodies.
In the development of the spermatozoa, as in the maturation of the ovum, there
is a reduction of the nuclear chromosomes to one-half of those present in the
primary spermatocyte. But here the similarity ends, for it must be noted that
the four spermatozoa are of equal size, and each is capable of fertilizing a mature
ovum, whereas the three polar bodies are not only very much smaller than the
mature ovum but are incapable of further development, and may be regarded as
abortive ova.
FERTILIZATION OF THE OVUM.
Fertilization consists in the union of the spermatozoon with the mature ovum
(Fig. 8). Nothing is known regarding the fertilization of the human ovum, but
1. Polar hod
Female 'pronucleus
Male pronucleus
Female pronucleus
Male pronucleus
Segmentation
nucleus
Female pronucleus
Male pronucleus
4.
Fused pronuclei
Segmentation
nucleus
commencing
division)
Fig. 8. — The process of fertilization in the ovum of a mouse. (After Sobotta.)
the various stages of the process have been studied in other mammals, and from
the knowledge so obtained it is believed that fertilization of the human ovum takes
place in the lateral or ampullary part of the uterine tube, and the ovum is then
conveyed along the tube to the cavity of the uterus — a journey probably occupy-
ing seven or eight days and during which the ovum loses its corona radiata and zona
striata and undergoes segmentation. Sometimes the fertilized ovum is arrested
in the uterine tube, and there undergoes development, giving rise to a tubal preg-
nancy; or it may fall into the abdominal cavity and produce an abdominal preg-
nancy. Occasionally the ovum is not expelled from the follicle when the latter
ruptures, but is fertilized within the follicle and produces what is known as an
ovarian pregnancy. Under normal conditions only one spermatozoon enters the
yolk and takes part in the process of fertilization. At the point where the sperma
SEGMENTATION OF THE FERTILIZED OVUM
45
tozoon is about to pierce, the yolk is drawn out into a conical elevation, termed
the cone of attraction. As soon as the spermatozoon has entered the yolk, the per-
ipheral portion of the latter is transformed into a membrane, the vitelline membrane
which prevents the passage of additional spermatozoa. Occasionally a second
spermatozoon may enter the yolk, thus giving rise to a condition of polyspermy:
when this occurs the ovum usually develops in an abnormal manner and gives rise
to a monstrosity. Having pierced the yolk, the spermatozoon loses its tail, while
its head and connecting piece assume the form of a nucleus containing a cluster of
chromosomes. This constitutes the male pronucleus, and associated with it there are
a centriole and centrosome. The male pronucleus passes more deeply into the yolk,
and coincidently with this the granules of the cytoplasm surrounding it become
radially arranged. The male and female pronuclei migrate toward each other, and.
meeting near the center of the yolk, fuse to form a new nucleus, the segmentation
nucleus, which therefore contains both male and female nuclear substance; the
former transmits the individualities of the male ancestors, the latter those of the
female ancestors, to the future embryo. By the union of the male and female
pronuclei the number of chromosomes is restored to that which is present in the
nuclei of the somatic cells.
FiQ. 9. — First stages of segmentation of a mammalian ovum. Semidiagrammatic. (From a drawing by Alien
Tiiomson.) z.p. Zona striata, p.gl. Polar bodies, a. Two-cell stage, b. Four-cell stage, c. Eight-cell stage.
d, e. Morula stage.
SEGMENTATION OF THE FERTILIZED OVUM.
The early segmentation of the human ovum has not yet been observed, but
judging from what is known to occur in other mammals it may be regarded as
certain that the process starts immediately after the ovum has been fertilized,
i. e., while the ovum is in the uterine tube. The segmentation nucleus exhibits
the usual mitotic changes, and these are succeeded by a division of the ovum into
two cells of nearly equal size.^ The process is repeated again and again, so that
' In the mammalian ova the nutritive yolk or deutoplasm is small in amount and uniformly distributed through-
out the cytoplasm; such ova undergo complete division during the process of segmentation, and are therefore termed
holoblastic. In the ova of birds, reptiles, and fishes where the nutritive yolk forms by far the larger portion of the
egg, the cleavage is limited to the formative yolk, and is therefore only partial; such ova are termed meroblastic._ Again,
it has been observed, in some of the lower animals, that the pronuclei do not fuse but merely lie in apposition. At
the commencement of the segmentation process the chromosomes of the two pronuclei group themselves around the
equator of the nuclear spindle and then divide; an equal number of male and female chromosomes travel to the opposite
poles of the spindle, and thus the male and female pronuclei contribute equal shares of chromatin to the nuclei of
the two cells which result from the subdivision of the fertilized ovum.
46
EMBRYOLOGY
the two cells are succeeded by four, eight, sixteen, thirty-two, and so on, with the
result that a mass of cells is found within the zona striata, and to this mass the term
morula is applied (Fig. 9). The segmentation of the mammalian ovum may not
take place in the regular sequence of two, four, eight, etc., since one of the two first
formed cells may subdivide more rapidly than the other, giving rise to a three-
or a five-cell stage. The cells of the morula are at first closely aggregated, but soon
they become arranged into an outer or peripheral layer, the trophoblast, which
Inner cell-mass
Entoderm
Blastodermic vesicle
\
Trophoblast
Fig. 10. — Blastodermic vesicle of Vespertilio murinus. (After van Beneden.
• Inner cell-mass Trofhoblast
Embryonic ectoderm Entoderm
Fig. 11. — Section through embryonic disk of Vespertilio murinus. (After van Beneden.)
Maternal bloodvessels
Amniotic cavity
Syncytiotro'phohlost
Cytotrophdblast
Embryonic ectoderm Entoderm
Fig. 12. — Section through embryonic area of Vespertilio murinus to show the formation of the amniotic cavity.
(After van Beneden,)
does not contribute to the formation of the embryo proper, and an inner cell-mass,
from which the embryo is developed. Fluid collects between the trophoblast
and the greater part of the inner cell-mass, and thus the morula is converted into
a vesicle, the blastodermic vesicle (Fig. 10). The inner cell-mass remains in con-
tact, however, with the trophoblast at one pole of the ovum; this is named the
embryonic pole, since it indicates the situation where the future embryo will be
developed. The cells of the trophoblast become differentiated into two strata: an
SEGMENTATION OF THE FERTILIZED OVUM 47
outer, termed the syncytium or syncytiotrophoblast, so named because it consists of
a layer of protoplasm studded with nuclei, but showing no evidence of subdivision
into cells; and an inner la^er, the cytotrophoblast or layer of Langhans, in which
the cell outlines are defined. As already stated, the cells of the trophoblast do not
contribute to the formation of the embryo proper; they form the ectoderm of the
chorion and play an important part in the development of the placenta. On the
deep surface of the inner cell-mass a layer of flattened cells, the entoderm, is differ-
entiated and quickly assumes the form of a small sac, the yolk-sac. Spaces appear
between the remaining cells of the mass (Fig. 11), and by the enlargement and
coalescence of these spaces a cavity, termed the amniotic cavity (Fig. 12), is gradually
developed. The floor of this cavity is formed by the embryonic disk composed
of a layer of prismatic cells, the embryonic ectoderm, derived from the inner cell-
mass and lying in apposition with the entoderm.
The Primitive Streak; rormation of the Mesoderm. — The embryonic disk
becomes oval and then pear-shaped, the wider end being directed forward. Near
the narrow, posterior end an opaque streak, the primitive
streak (Figs. 13 and 14), makes its appearance and extends
along the middle of the disk for about one-half of its
length; at the anterior end of the streak there is a knob-
like thickening termed Hensen's knot. A shallow groove,
the primitive groove, appears on the surface of the streak,
and the anterior end of this groove communicates by
means of an aperture, the blastophore, with the yolk-sac.
The primitive streak is produced by a thickening of the
axial part of the ectoderm, the cells of which multiply,
grow downward, and blend with those of the subjacent
entoderm (I'ig. 15). From the sides of the primitive streak ^ ,o ^ .
,.,,°„,, , ^ , ■, Fig. 13. — Surface view of
a third la^'er ot cells, the mesoderm, extends lateralward embryo of a rabbit. (After
1 , ,1^ ,1 1.1 .1 1 1 1 i> Kolliker.) arg. Embryonic
between the ectoderm and entoderm; the caudal end ot disk. pr. Primitive streak.
the primitive streak forms the cloacal membrane.
The extension of the mesoderm takes place throughout the whole of the embry-
onic and extra-embryonic areas of the ovum, except in certain regions. One of
these is seen immediately in front of the neural tube. Here the mesoderm extends
forward in the form of two crescentic masses, which meet in the middle line so as
to enclose behind them an area which is devoid of mesoderm. Over this area the
ectoderm and entoderm come into direct contact with each other and constitute
a thin membrane, the buccopharyngeal membrane, which forms a septum between
the primitive mouth and pharynx. In front of the buccopharyngeal area, where
the lateral crescents of mesoderm fuse in the middle line, the pericardium is
afterward developed, and this region is therefore designated the pericardial area. A
second region where the mesoderm is absent, at least for a time, is that imme-
diately in front of the pericardial area. This is termed the proamniotic area, and
is the region where the proamnion is developed; in man, however, a proamnion is
apparently never formed. A third region is at the hind end of the embryo where
the ectoderm and entoderm come into apposition and form the cloacal membrane.
The blastoderm now consists of three layers, named from without inward:
ectoderm, mesoderm, and entoderm; each has distinctive characteristics and gives
rise to certain tissues of the body.^
Ectoderm. — The ectoderm consists of columnar cells, which are, however, somewhat
flattened or cubical toward the margin of the embryonic disk. It forms the whole
of the nervous system, the epidermis of the skin, the lining cells of the sebaceous,
' The mode of formation of the germ layers in the human ovum has not yet been observed ; In the youngest known
human ovum (viz., that described by Bryce and Teacher), all three layers are already present and the mesoderm is
split into its two layers. The extra-embr>-onic celom is of considerable size, and scattered mesodermal strands are
seen stretching between the mesoderm of the yolk-sac and that of the chorion.
48
EMBRYOLOGY
Yolk-sac
Notochord
Amnion
\\
Allantois in body-stalk
— Amnion
Neurenteric canal
Primitive streak
Fig. 14.— Surface view of embryo of Hylobates concolor. (After Selenka.) The amnion has been opened to expose
the embryonic disk.
^^ife'^5m
Fig. 15. — Series of transverse sections through the embrj'onic disk of Tarsius. (After Hubrecht ) Section I passes
through the disk, in front of Hansen's knot and sliows only the ectoderm and entoderm. Sections//,///, and /Fpass
through Hensen's knot, which is seen in V tapering away into the primitive streak. In ///, IV , and V the mesoderm
is seen springing from the keel-like thickening of the ectoderm, which in /// and IV is observed to be continuous into
"the entoderm.
SEGMENTATION OF THE FERTILIZED OVUM
49
sudoriferous, and mammary glands, the hairs and nails, the epithelium of the nose
and adjacent air sinuses, and that of the cheeks and roof of the mouth. From it
also are derived the enamel of the teeth, and the anterior lobe of the hypophysis
cerebri, the epithelium of the cornea, conjunctiva, and lacrimal glands, and the
neuro-epithelium of the sense organs.
Entoderm.— The entoderm consists at first of flattened cells, which subsequently
become columnar. It forms the epithelial lining of the whole of the digestive tube
excepting part of the mouth and pharynx and the terminal part of the rectum
(which are lined by involutions of the ectoderm), the lining cells of all the glands
which open into the digestive tube, including those of the liver and pancreas.
m.
IV,
- sm
mty
-'f^//j
, •* # »• •••••■ • ••-
••■•••44
ta^
'%%
:•:*','' /i^siTf --/=?='•
Fig. 16. — A series of transverse sections through an embryo of the dog. (After Bonnet.) Section / is the most
anterior. In V the neural plate is spread out nearly flat. The series shows the uprising of the neural folds to form the
neural canal, a. Aortae. c. Intermediate cell mass. ect. Ectoderm. e7il. Entoderm, h, h. Rudiments of endothelial
heart tubes. In ///, IV, and V the scattered cells represented between the entoderm and splanchnic layer of meso-
derm are the vasoformative cells which give origin in front, according to Bonnet, to the heart tubes, h; l.p. Lateral
plate still undivided in /, II, and III; in IV and V split into somatic (sm) and splanchnic (sp) layers of mesoderm.
Tnes. Mesoderm, p. Pericardium, so. Primitive segment.
the epithelium of the auditory tube and tympanic cavity, of the trachea, bronchi,
and air cells of the lungs, of the urinary bladder and part of the urethra, and that
which lines the follicles of the thyroid gland and thymus.
Mesoderm. — The mesoderm consists of loosely arranged branched cells sur-
rounded by a considerable amount of intercellular fluid. From it the remaining
tissues of the body are developed. The endothelial lining of the heart and blood-
vessels and the blood corpuscles are, however, regarded by some as being of ento-
dermal origin.
As the mesoderm develops between the ectoderm and entoderm it is separated
into lateral halves by the neural tube and notochord, presently to be described. A
4
50
EMBRYOLOGY
longitudinal groove appears on the dorsal surface of either half and divides it into
a medial column, the paraxial mesoderm, lying on the side of the neural tube, and
a lateral portion, the lateral mesoderm. The mesoderm in the floor of the groove
connects the paraxial with the lateral mesoderm and is known as the intermediate
cell-mass; in it the genito-urinary organs are developed. The lateral mesoderm
splits into two layers, an outer or somatic, which becomes applied to the inner surface
of the ectoderm, and with it forms the somatopleure ; and an inner or splanchnic,
which adheres to the entoderm, and with it forms the splanchnopleure (Fig. IG).
The space between the two layers of the lateral mesoderm is termed the celom.
THE NEURAL GROOVE AND TUBE.
In front of the primitive streak two longitudinal ridges, caused by a folding up
of the ectoderm, make their appearance, one on either side of the middle line
(Fig. 16). These are named the neural folds; they commence some little distance
Yolk-sac
Amnion
Neural groove
Neurenteric canal
Primitive streak
Body-stalk -z
Fig. 17. — Human embryo — length, 2 mm. Dorsal view, with the amnion laid open. X 30. (After Graf Spee.)
behind the anterior end of the embryonic disk, w^here they are continuous with
each other, and from there gradually extend backward, one on either side of the
anterior end of the primitive streak. Between these folds is a shallow median
groove, the neural groove (Figs. 10, 17) . The groove gradually deepens as the neural
folds become elevated, and ultimately the folds meet and coalesce in the middle line
and convert the groove into a closed tube, the neural tube or canal (Fig. 18), the
ectodermal wall of which forms the rudiment of the nervous system. After the
coalescence of the neural folds over the anterior end of the primitive streak, the
blastopore no longer opens on the surface but into the closed canal of the neural
tube, and thus a transitory communication, the neurenteric canal, is established
between the neural tube and the primitive digestive tube. The coalescence of the
neural folds occurs first in the region of the hind-brain, and from there extends
forward and backward; toward the end of the third week the front opening (anterior
neuropore) of the tube finally closes at the anterior end of the future brain, and
forms a recess which is in contact, for a time, with the overlying ectoderm; the
hinder part of the neural groove presents for a time a rhomboidal shape, and to this
THE NEURAL GROOVE AND TUBE
51
expanded portion the term sinus rhomboidalis has been applied (Fig. 18). Before
the neural groove is closed a ridge of ectodermal cells appears along the prominent
margin of each neural fold ; this is termed the neural crest or ganglion ridge, and from
it the spinal and cranial nerve ganglia and the ganglia of the sympathetic nervous
system are developed. By the upward growth of the mesoderm the neural tube
is ultimately separated from the overlying ectoderm.
Head fold of amnion partly
covering the fore-brain
Mid-hrain
Hind-brain -i-^
Nerve ganglion
Auditory vesicle -K^ - i
Vitelline vein
Fourteenth primitive
segment
Paraxial mesoderm
Neural fold
Heart
Sinus rhomboidalis -^
Remains of primitive streak ^
Fig. 18. — Chick embryo of thirty-three hour.'i' incubation, vieucJ liuin the dorsal aspect. X 30.
(From Duval'3 "Atlas d'Embryologie.")
The cephalic end of the neural groove exhibits several dilatations, which, when
the tube is closed, assume the form of three vesicles; these constitute the three
primary cerebral vesicles, and correspond respectively to the future fore-brain (pros-
enceyhalon) , mid-brain (mesencephalon), and hind-brain {rhombencephalon) (Fig.
18). The walls of the vesicles are developed into the nervous tissue and neuroglia
of the brain, and their cavities are modified to form its ventricles. The remainder
52
EMBRYOLOGY
of the tube forms the medulla spinalis or spinal cord; from its ectodermal wall
the nervous and neuroglial elements of the medulla spinalis are developed while
the cavity persists as the central canal.
THE NOTOCHORD.
The notochord (Fig. 19) consists of a rod of cells situated on the ventral aspect
of the neural tube; it constitutes the foundation of the axial skeleton, since around
it the segments of the vertebral column are formed. Its appearance synchronizes
with that of the neural tube. On the ventral aspect of the neural groove an axial
thickening of the entoderm takes place; this thickening assumes the appearance
of a furrow — the chordal furrow^ — the margins of which come into contact, and so
convert it into a solid rod of cells — the notochord — which is then separated from
the entoderm. It extends throughout the entire length of the future vertebral
Ectoderm .,
Neural canal Primitive Wolffian
segment duct Celom
, f
Somatic mesoderm
Entoderm '''
Notochord Aorta Splanchnic mesoderm
Fig. 19. — Transverse section of a c}iick embryo of forty-five hours' incubation.
(Balfour.)
column, and reaches as far as the anterior end of the mid-brain, where it ends in
a hook-like extremity in the region of the future dorsum sellse of the sphenoid
bone. It lies at first between the neural tube and the entoderm of the yolk-sac,
but soon becomes separated from them by the mesoderm, which grows medial-
ward and surrounds it. From the mesoderm
surrounding the neural tube and notochord,
the skull and vertebral column, and the
membranes of the brain and medulla spinalis
are developed.
. THE PRIMITIVE SEGMENTS.
Toward the end of the second week
transverse segmentation of the paraxial
mesoderm begins, and it is converted into
a series of well-defined, more or less cubical
masses, the primitive segments (Figs. IS,
19, 20), which occupy the entire length of
the trunk on either side of the middle line
from the occipital region of the head. Fach
segment contains a central cavity — myocoel
— which, however, is soon filled with angular
and spindle-shaped cells.
The primitive segments lie immediately
under the ectoderm on the lateral aspect of
the neural tube and notochord, and are con-
nected to the lateral mesoderm by the inter-
mediate cell-mass. Those of the trunk mav
Yolk-
sac
Cut edge of amnion
Primitive segments
Fig
— Neural folds
•'^'■^37^ • Neurenteric canal
-Dorsum of human embryo, 2.11 mm.
length. (After Eternod.)
SEPARATION OF THE EMBRYO
53
be arranged in the following groups, viz.: cervical 8, thoracic 12, lumbar 5,
sacral 5, and coccygeal from 5 to 8. Those of the occipital region of the head
are usually described as being four in number. In mammals primitive segments
of the head can be recognized only in the occipital region, but a study of the
lower vertebrates leads to the belief that they are present also in the anterior
part of the head, and that altogether nine segments are represented in the
cephalic region.
SEPARATION OF THE EMBRYO.
The embryo increases rapidly in size, but the circumference of the embryonic
disk, or line of meeting of the embryonic and amniotic parts of the ectoderm, is of
relatively glow growth and gradually comes to form a constriction between the
embryo and the greater part of the yolk-sac. By means of this constriction, which
corresponds to the future umbilicus, a small part of the yolk-sac is enclosed within
the embryo and constitutes the primitive digestive tube.
Villi of chorion
Amnion
Embryonic disk
Rvdiment of heart
Chorion
-.vigs^- ^ Mesoderm
Body-stalk
Primitive streak
Allantois
Entoderm
Mesoderm
Bloodvessel
Fig. 21. — Section through the embryo which ia represented in Fig. 17. (After Graf Spee.)
The embryo increases more rapidly in length than in width, and its cephalic and
caudal ends soon extend beyond the corresponding parts of the circumference of
the embryonic disk and are bent in a ventral direction to form the cephalic and
caudal folds respectively (Figs. 26 and 27). The cephalic fold is first formed, and
as the proamniotic area (page 47) lying immediately in front of the pericardial
area (page 47) forms the anterior limit of the circumference of the embryonic
disk, the forward growth of the head necessarily carries with it the posterior end
of the pericardial area, so that this area and the buccopharyngeal membrane are
folded back under the head of the embryo which now encloses a diverticulum of the
yolk-sac named the fore-gut. The caudal end of the embryo is at first connected
to the chorion by a band of mesoderm called the body-stalk, but with the formation
of the caudal fold the body-stalk assumes a ventral position; a diverticulum of the
yolk-sac extends into the tail fold and is termed the hind-gut. Between the fore-gut
54
EMBRYOLOGY
and the hind-gut there exists for a time a wide opening into the yolk-sac, but the
latter is gradually reduced to a small pear-shaped sac (sometimes termed the
umbilical vesicle), and the channel of communication is at the same time narrowed
and elongated to form a tube called the vitelline duct.
THE YOLK-SAC.
The yolk-sac (Figs. 22 and 23) is situated on the ventral aspect of the embryo;
it is lined by entoderm, outside of which is a layer of mesoderm. It is filled with
fluid, the vitelline fluid, which possibly may be utilized for the nourislunent of the
embryo during the earlier stages of its existence. Blood is conveyed to the wall of
the sac by the primitive aortae, and after circulating through a wide-meshed capil-
lary plexus, is returned by the vitelline veins to the tubular heart of the embryo.
This constitutes the vitelline circulation, and by means of it nutritive material is
absorbed from the yolk-sac and conveyed to the embryo. At the end of the fourth
week the yolk-sac presents the appearance of a small pear-shaped vesicle (umbilical
vesicle) opening into the digestive tube by a long narrow tube, the vitelline duct.
The vesicle can be seen in the after-birth as a small, somewhat oval-shaped body
Amnion
Yolk-sac
Heart
Hijoid
Mandibular arch
Maxillary process
Eye
Fore-limb
Bodv-stalk
Fig. 22. — Human embrj'o of 2.6 mni. (His.)
Hind-limb
Fig. 23. — Human embryo from thirty-one to thirty-four
days. (His.)
whose diameter varies from 1 mm. to 5 mm.; it is situated between the amnion
and the chorion and may lie on or at a varying distance from the placenta. As
a rule the duct undergoes complete obliteration during the seventh week, but
in about three per cent, of cases its proximal part persists as a diverticulum
from the small intestine, Meckel's diverticulum, which is situated about three or
four feet above the ileocolic junction, and may be attached by a fibrous cord to
the abdominal wall at the umbilicus. Sometimes a narrowing of the lumen of the
ileum is seen opposite the site of attachment of the duct.
DEVELOPMENT OF THE FETAL MEMBRANES AND THE PLACENTA.
The Allantois (Figs. 25 to 28). — The allantois arises as a tubular diverticulum
of the posterior part of the ^'olk-sac; when the hind-gut is developed the allantois
is carried backward with it and then opens into the cloaca or terminal part of the
hind-gut: it grows out into the body-stalk, a mass of mesoderm which lies below
and around the tail end of the embryo. The diverticulum is lined by entoderm
and covered by mesoderm, and in the latter are carried the allantoic or umbilical
vessels.
DEVELOPMENT OF THE FETAL MEMBRANES AND THE PLACENTA 55
In reptiles, birds, and many mammals the allantois becomes expanded into a
vesicle which projects into the extra-embryonic celom. If its further development
be traced in the bird, it is seen to project to the right side of the embryo, and,
gradually expanding, it spreads over its dorsal surface as a flattened sac between
the amnion and the serosa, and extending in all directions, ultimately surrounds
the yolk. Its outer wall becomes applied to and fuses with the serosa, which lies
immediately inside the shell membrane. Blood is carried to the allantoic sac by
Ainniotic cavity
Fig. 24.
Amniotic cavity
Yolk-sac
Chorion
-Diagram showing earliest observed stage
of human ovum.
Body-stalk
Allantois
• Yolk-sac
Chorion
Fio. 25. — Diagram illustrating early formation of
allantois and differentiation of body-stalk.
the two allantoic or umbilical arteries, which are continuous with the primitive
aortse, and after circulating through the allantoic capillaries, is returned to the
primitive heart by the two umbilical veins. In this way the allantoic circulation,
which is of the utmost importance in connection with the respiration and nutrition
of the chick, is established. Oxygen is taken from, and carbonic acid is given up
to the atmosphere through the egg-shell, while nutritive materials are at the same
time absorbed by the blood from the yolk.
Amniotic cavitij
Embryo
Body-stalk
Placental
villi
Placental
villi
Allantois
Yolk-sac
Chorion
Heart
Fig. 26 — Diagram showing later stage of allan-
toic development with commencing constriction
of the yolk-sac.
Body-stalk
Allantois
Yolk-sac
Heart
Fore-gut
Embryo
Amniotic cavity
Fig. 27. — Diagram showing the expansion of amnion
and delimitation of the umbilicus.
In man and other primates the nature of the allantois is entirely different from
that just described. Here it exists merely as a narrow, tubular diverticulum of the
hind-gut, and never assumes the form of a vesicle outside the embryo. With the
formation of the amnion the embryo is, in most animals, entirely separated from
the chorion, and is only again united to it when the allantoic mesoderm spreads
over and becomes applied to its inner surface. The human embryo, on the other
hand, as was pointed out by His, is never wholly separated from the chorion, its
56
EMBRYOLOGY
Yolk-sac
Umbilical cord
Allantois
Heart
Digestive tube
tail end being from the first connected with the chorion by means of a thick band
of mesoderm, named the body-stalk (Bauchstiel) ; into this stalk the tube of the
allantois extends (Fig. 21).
The Amnion. — The amnion is a membranous sac which surrounds and protects
the embryo. It is developed in reptiles, birds, and mammals, which are hence
called "Amniota;" but not in amphibia and fishes, which are consequently termed
"Anamnia."
In the human embryo the earliest stages of the formation of the amnion have not
been observed; in the youngest embryo which has been studied the amnion was
already present as a closed sac (Figs. 24 and 32), and, as indicated on page 46,
appears in the inner cell-mass as a cavity. This cavity is roofed in by a single
stratum of flattened, ectodermal cells, the amniotic ectoderm, and its floor consists
of the prismatic ectoderm of the embryonic disk — the continuity between the
roof and floor being established at
Placental villi the margin of the embryonic disk.
Outside the amniotic ectoderm is
a thin layer of mesoderm, which
is continuous with that of the
somatopleure and is connected by
the body-stalk with the meso-
dermal lining of the chorion.
When first formed the amnion
is in contact with the body of the
embrvo, but about the fourth or
fifth week fluid (liquor amnii) be-
gins to accumulate within it. This
fluid increases in quantity and
causes the amnion to expand and
ultimately to adhere to the inner
surface of the chorion, so that the
extra-embryonic part of the celom
is obliterated. The liquor amnii
increases in quantity up to the
sixth or seventh month of preg-
nancy, after which it diminishes
somewhat; at the end of preg-
nancy it amounts to about 1 liter. It allows of the free movements of the fetus
during the later stages of pregnancy, and also protects it by diminishing the risk
of injury from without. It contains less than 2 per cent, of solids, consisting of
urea and other extractives, inorganic salts, a small amount of protein, and frequently
a trace of sugar. That some of the liquor amnii is swallowed by the fetus is proved
by the fact that epidermal debris and hairs have been found among the contents of
the fetal alimentary canal.
In reptiles, birds, and many mammals the amnion is developed in the following
manner: At the point of constriction where the primitive digestive tube of the
embryo joins the yolk-sac a reflection or folding upward of the somatopleure takes
place. This, the amniotic fold (Fig. 29), first makes its appearance at the cephalic
extremity, and subsequently at the caudal end and sides of the embryo, and grad-
ually rising more and more, its different parts meet and fuse over the dorsal aspect
of the embryo, and enclose a cavity, the amniotic cavity. After the fusion of the
edges of the amniotic fold, the two layers of the fold become completely separated,
the inner forming the amnion, the outer the false amnion or serosa. The space
between the amnion and the serosa constitutes the extra-embrj'onic celom, and
for a time communicates with the embrvonic celom.
JUmbryo
Amniotic cavity
Fia. 28. — Diagram illustrating a later stage in the development
of the umbilical cord.
DEVELOPMENT OF THE FETAL MEMBRANES AND THE PLACENTA 57
The Umbilical Cord and Body-stalk.— The umbilical cord (Fig. 28) attaches
the fetus to the placenta; its length at full time, as a rule, is about equal to the
false amnion or serosa
vi/ll of
chono,
-Tniiscle
plate
card .T'ein
Wolffian body
and duct
ccelom
Fig. 29. — Diagram of a transverse section, showing ttie mode of formation of the amnion in tlie chick. The amniotic
folds have nearly united ia the middle line. (From Quain's Anatomy.) Ectoderm, blue; mesoderm, red; entoderm
and notochord, black.
Umbilical
cord
Chorion
Placenta
Amnion
Umbilical
cord
Yolk-sac
Vitelline
duel
Fig. 30. — Fetus of about eight weeks, enclosed in the amnion. Magnified a little over two diameters,
from stereoscopic photographs lent by Prof. A. Thomson. Oxford.)
(Drawn
58
EMBRYOLOGY
length of the fetus, i. e., about 50 cm., but it may be greatly diminished or increased.
The rudiment of the umbilical cord is represented by the tissue which connects
the rapidly growing embryo with the extra-embryonic area of the ovum. Included
in this tissue are the body-stalk and the vitelline duct— the former containing the
allantoic diverticulum and the umbilical vessels, the latter forming the communica-
tion between the digestive tube and the yolk-sac. The body-stalk is the posterior
segment of the embryonic area, and is attached to the chorion. It consists of a plate
of mesoderm covered by thickened ectoderm on which a trace of the neural groove
can be seen, indicating its continuity with the embryo. Running through its
mesoderm are the two umbilical arteries and the two umbilical veins, together with
the canal of the allantois — the last being lined by entoderm (Fig. 31). Its dorsal
surface is covered by the amnion, while its ventral surface is bounded by the extra-
embrvonic celom, and is in contact with the vitelline duct and volk-sac. With
the rapid elongation of the embryo and the formation of the tail fold, the bodj'
stalk comes to lie on the ventral surface of the embryo (Figs. 27 and 28), where
Splanchnic
mesoderm
Entoderm
Vitelline veins
Somatic mesoderm
111 Amniotic cavity
■ ill — Amnion
Neural groove
Neurenteric canal
Body-stalk
Fig. 31. — Model of human embrj-o 1.3 mm. long. (After Eternod.)
its mesoderm blends with that of the yolk-sac and the vitelline duct. The lateral
leaves of somatopleure then grow round on each side, and, meeting on the ventral
aspect of the allantois, enclose the vitelline duct and vessels, together with a part
of the extra-embryonic celom; the latter is ultimately obliterated. The cord is
covered by a layer of ectoderm which is continuous with that of the amnion, and
its various constitutents are enveloped by embryonic gelatinous tissue, jelly of
Wharton. The vitelline vessels and duct, together with the right umbilical vein,
undergo atrophy and disappear; and thus the cord, at birth, contains a pair of
umbilical arteries and one (the left) umbilical vein.
Implantation or Imbedding of the Ovum. — As described (page 44), fertilization
of the ovum occurs in the lateral or ampullary end of the uterine tube and is
immediately followed by segmentation. On reaching the cavity of the uterus the
segmented ovum adheres like a parasite to the uterine mucous membrane, destroys
the epithelium over the area of contact, and excavates for itself a cavity in the
mucous membrane in which it becomes imbedded. In the ovum described by
DEVELOPMENT OF THE FETAL MEMBRANES AND THE PLACENTA 59
Bryce and Teacher"^ the point of entrance was visible as a small gap closed by a
mass of fibrin and leucocytes; in the ovum described by Peters^ the opening was
covered by a mushroom-shaped mass of fibrin and blood-clot (Fig. 32) , the narrow
stalk of which plugged the aperture in the mucous membrane. Soon, however,
all trace of the opening is lost and the ovum is then completely surrounded by the
uterine mucous membrane.
The structure actively concerned in the process of excavation is the trophoblast
of the ovum, which possesses the power of dissolving and absorbing the uterine
tissues. The trophoblast proliferates rapidly and forms a network of branching
processes which cover the entire ovum and invade and destroy the maternal
tissues and open into the maternal bloodvessels, with the result that the spaces
in the trophoblastic network are filled with maternal blood; these spaces com-
municate freely with one another and become greatly distended and form the
intervillous space.
m.v. /^ ti.Q. tn
Fig. 32.-Section through ovum imbedded in the uterine decidua. , ^enudiagrammatic (After Peters^) am.
Amniotic cavity, b.c. Blood-clot. b.s. Body-stalk, ect, Embryomc ectoderm, ent Entoderm mes. Mesoderm.
m.v. Maternal vessels, tr. Trophoblast. u.e. Uterine epithelmm. u.g. Uterme glands, y.s. \ olk-sac.
The Decidua.— Before the fertilized ovum reaches the uterus, the mucous
membrane of the body of the uterus undergoes important changes and is then
known as the decidua. The thickness and vascularity of the mucous membrane
are greatly increased; its glands are elongated and open on its free surface by
funnel-shaped orifices, while their deeper portions are tortuous and dilated into
irregular spaces. The interglandular tissue is also increased in quantity, and
is crowded with large round, oval, or polygonal cells, termed decidual cells. These
changes are well advanced by the second month of pregnancy, when the mucous
membrane consists of the following strata (Fig. 33): (1) stratum compactum, next
1 Contribution to the study of the early development and imbedding of the human ovum, 1908.
« Die Einbettung des menschlichen Eies, 1899.
60
EMBRYOLOGY
Mucous tnembrane
Muscular fibers
Stratum compactum
the free surface; in this the uterine glands are only slightly expanded, and are
lined by columnar cells; (2) stratum spongiosum, in which the gland tubes are greatly
dilated and very tortuous, and are ultimately separated from one another by only
a small amount of interglandular tissue, while their lining cells are flattened or
cubical; (3) a thin unaltered or boundary layer, next the uterine muscular fibers,
containing the deepest parts of the uterine glands, which are not dilated, and
are lined with columnar epithelium;
it is from this epithelium that the
epithelial lining of the uterus is re-
generated after pregnancy. Distinc-
tive names are applied to different
portions of the decidua. The part
which covers in the ovum is named the
decidua capsularis; the portion which
intervenes between the ovum and the
uterine wall is named the decidua
basalis or decidua placentalis ; it is here
that the placenta is subsequently
developed. The part of the decidua
which lines the remainder of the body
of the uterus is known as the decidua
vera or decidua parietalis.
Coincidently with the growth of
the embryo, the decidua capsularis is
thinned and extended (Fig. 34) and
the space between it and the decidua
vera is gradually obliterated, so that
by the third month of pregnancy the
two are in contact. By the fifth
month of pregnancy the decidua cap-
sularis has practically disappeared,
while during the succeeding months
the decidua vera also undergoes
atrophy, owing to the increased press-
ure. The glands of the stratum com-
pactum are obliterated, and their
epithelium is lost. In the stratum
spongiosum the glands are compressed
and appear as slit-like fissures, while
their epithelium undergoes degener-
ation. In the unaltered or boundary
layer, however, the glandular epithe-
lium retains a columnar or cubical
form.
The Chorion (Figs. 23 to 28). —The
chorion consists of two layers : an outer
formed by the primitive ectoderm or
trophoblast, and an inner by the soma-
tic mesoderm; with this latter the amnion is in contact. The trophoblast is made
up of an internal layer of cubical or prismatic cells, the cytotrophoblast or layer
of Langhans, and an external layer of richly nucleated protoplasm devoid of cell
boundaries, the syncytiotrophoblast. It undergoes rapid proliferation and forms
numerous processes, the chorionic villi, which invade and destroy the uterine
decidua and at the same time absorb from it nutritive materials for the growth
Stratum spongiosum
Unaltered or
boundary layer
Muscular fibers
Fig. 33. — Diagrammatic sections of the uterine mucous
membrane: A. The non-pregnant uterus. B. The preg-
nant uterus, showing the thickened mucous membrane
and the altered condition of the uterine glands. (Kundrat
and Engelmann.)
DEVELOPMENT OF THE FETAL MEMBRANES AND THE PLACENTA Gl
of the embryo. The chorionic villi are at first small and non-vascular, and consist
of trophoblast only, but they increase in size and ramify, while the mesoderm,
carrying branches of the umbilical vessels, grows into them, and in this way they
are vascularized. Blood is carried to the villi by the branches of the umbilical
Placental villi imbedded in the
^Decidua placentalis
Uterine tube
Allantois
Umbilical cord
with its con-
tained vessels
Non-placental villi im-
bedded in the decidua
capsularis
Cavity of uterus
~ Yolk-sac
Cavity of amnion
Decidua vera
or parietalis
Plug of mucus in the
cervix uteri
Fig. 34. — Sectional plan of the gravid uterus in the third and fourth month. (Modified from Wagner.)
arteries, and after circulating through the capillaries of the villi, is returned to
the embryo by the umbilical veins. Until about the end of the second month
of pregnancy the villi cover the entire chorion, and are almost uniform in size
(Fig, 25), but after this they develop unequally. The greater part of the chorion
Trophoblast
Mesoderm
Branches of umbilical vessels
Fig. 35. — Transverse section of a chorionic villus.
is in contact with the decidua capsularis (Fig. 34), and over this portion the villi,
with their contained vessels, undergo atrophy, so that by the fourth month scarcely
a trace of them is left, and hence this part of the chorion becomes smooth, and is
named the chorion Iseve; as it takes no share in the formation of the placenta, it
62
EMBRYOLOGY
is also named the non-placental part of the chorion. On the other hand, the villi
on that part of the chorion which is in contact with the decidua placentalis increase
greatlv in size and complexity, and hence this part is named the chorion frondosum
(Fig. 28).
Uterine vessels
Uterine glands
Syncytiotrophoblast
- — Cytotrophoblasi
Mesoderm
Fig. 36. — Primary chorionic villi.
Intervillous space
Diagrammatic. (Modified from Bryoe.
The Placenta. — The placenta connects the fetus to the uterine wall, and is the
organ by means of which the nutritive, respiratory, and excretory functions of the
fetus are carried on. It is composed of fetal and maternal portions.
Fetal Portion. — The fetal portion of the placenta consists of the villi of the
chorion frondosum; these branch repeatedly, and increase enormously in size.
These greatly ramified villi are suspended in the intervillous space, and are bathed
Uterine glands
Uterine vessels
Syncytiotrophoblast
Cytotrophoblasi
Core of ynesoderm
with fetal vessels
Mesoderm Intervillous space
Fig. 37. — Secondary chorionic villi. Diagrammatic. (Modified from Bryce.)
in maternal blood, which is conveyed to the space by the uterine arteries and
carried away by the uterine veins. A branch of an umbilical artery enters each
villus and ends in a capillary plexus from which the blood is drained by a tributary
of the umbilical vein. The vessels of the villus are surrounded by a thin layer of
mesoderm consisting of gelatinous connective tissue, which is covered by two
DEVELOPMENT OF THE FETAL MEMBRANES AND THE PLACENTA 63
strata of ectodermal cells derived from the trophoblast: the deeper stratum,
next the mesodermic tissue, represents the cytotrophoblast or layer of Langhans;
the superficial, in contact with the maternal blood, the syncytiotrophoblast (Figs.
36 and 37). After the fifth month the two strata of cells are replaced by a
single layer of somewhat flattened cells.
Maternal Portion. — The maternal portion of the placenta is formed by the
decidua placentalis containing the intervillous space. As already explained, this
space is produced by the enlargement and intercommunication of the spaces in
the trophoblastic network. The changes involve the disappearance of the greater
portion of the stratum compactum, but the deeper part of this layer persists and
is condensed to form what is known as the basal plate. Between this plate and
the uterine muscular fibres are the stratum spongiosum and the boundary layer ;
Wall of uterus
Umbilical cord
Cervix uteri
Fig. 38. — Fetus in utero, between fifth and sixth months.
through these and the basal plate the uterine arteries and veins pass to and from
the intervillous space. The endothelial lining of the uterine vessels ceases at the
point where they terminate in the intervillous space which is lined by the syncytio-
trophoblast. Portions of the stratum compactum persist and are condensed to
form a series of septa, which extend from the basal plate through the thickness
of the placenta and subdivide it into the lobules or cotyledons seen on the uterine
surface of the detached placenta.
The fetal and maternal blood currents traverse the placenta, the former passing
through the bloodvessels of the placental \'illi and the latter through the inter-
villous space (Fig. 39) . The two currents do not intermingle, being separated from
each other by the delicate walls of the villi. Nevertheless, the fetal blood is able
to absorb, through the walls of the villi, oxygen and nutritive materials from the
64
EMBRYOLOGY
maternal blood, and give up to the latter its waste products. The blood, so purified,
is carried back to the fetus by the umbilical vein. It will thus be seen that the
placenta not only establishes a mechanical connection between the mother and the
fetus, but subserves for the latter the purposes of nutrition, respiration, and ex-
cretion. In favor of the view that the placenta possesses certain selective powers
may be mentioned the fact that glucose is more plentiful in the maternal than in
the fetal blood. It is interesting to note also that the proportion of iron, ancj of
lime and potash, in the fetus is increased during the last months of pregnancy.
Further, there is evidence that the maternal leucocytes may migrate into the fetal
blood, since leucocytes are much more numerous in the blood of the umbilical vein
than in that of the umbilical arteries.
The placenta is usually attached near the fundus uteri, and more frequently on
the posterior than on the anterior wall of the uterus. It may, however, occupy
a lower position and, in rare cases, its site is close to the orificium internum uteri,
which it may occlude, thus giving rise to the condition known as placenta previa.
Stratum spongiosum
Limiting or boundary layer
Maternal vessels
Placental septum
Villus
Chorion
Marginal sinus
Fig. 39. — Scheme of placental circulation.
Separation of the Placenta. — -After the child is born, the placenta and membranes
are expelled from the uterus as the after-birth. The separation of the placenta from
the uterine wall takes place through the stratum spongiosum, and necessarily
causes rupture of the uterine vessels. The orifices of the torn vessels are, how^ever,
closed by the firm contraction of the uterine muscular fibers, and thus postpartum
hemorrhage is controlled. The epithelial lining of the uterus is regenerated by the
proliferation and extension of the epithelium which lines the persistent portions
of the uterine glands in the unaltered layer of the decidua.
The expelled placenta appears as a discoid mass which weighs about 450 gm.
and has a diameter of from 15 to 20 cm. Its average thickness is about 3 cm.,
but this diminishes rapidly toward the circumference of the disk, which is continu-
ous with the membranes. Its uterine surface is divided by a series of fissures into
lobules or cotyledons, the fissures containing the remains of the septa which extended
between the maternal and fetal portions. Most of these septa end in irregular
or pointed processes; others, especially those near the edge of the placenta, pass
THE BRANCHIAL REGION
65
through its thickness and are attached to the chorion. In the early months tliese
septa convey branches of the uterine arteries which open into the intervillous
space on the surfaces of the septa. The fetal surface of the placenta is smooth,
being closely invested by the amnion. Seen through the latter, the chorion
presents a mottled appearance, consisting of gray, purple, or yellowish areas.
The umbilical cord is usually attached near the center of the placenta, but
may be inserted anywhere between the center and the margin; in some cases it
is inserted into the membranes, i. e., the velamentous insertion. From the attach-
ment of the cord the larger branches of the umbilical vessels radiate under the
amnion, the veins being deeper and larger than the arteries. The remains of
the vitelline duct and yolk-sac may be sometimes observed beneath the amnion,
close to the cord, the former as an attenuated thread, the latter as a minute sac.
On section, the placenta presents a soft, spongy appearance, caused by the
greatly branched villi; surrounding them is a varying amount of maternalblood
giving the dark red color to the placenta. Many of the larger villi extend from
the chorionic to the decidual surface, while others are attached to the septa which
separate the cotyledons; but the great majority of the villi hang free in the inter-
villous space.
Mid-brain
Fore-brain
Stomodeum
Mandibular arch
irt %.
Hea
Himl-hrain
Auditory vesicle
Visceral
arches
Amnion (cut)
Olfactory pit / \ w,
Maxillary process /)
Mandibular arch
Hyoid arch
Third arch
Fig. 40.-
Body-stalk
-Embryo between eighteen and twenty-one
days. (His.)
Fig. 41. — Head end of human embryo, about the end
of the fourth week. (From model by Peter.)
THE BRANCHIAL REGION.
The Branchial or Visceral Arches and Pharyngeal Pouches. — In the lateral walls
of the anterior part of the fore-gut five pharyngeal i)ouches appear (Fig. 42) ; each
of the upper four pouches is prolonged into a dorsal and a ventral diverticulum.
Over these pouches corresponding indentations of the ectoderm occur, forming what
are known as the branchial or outer pharyngeal grooves. The intervening mesoderm
is pressed aside and the ectoderm comes for a time into contact with the ento-
dermal lining of the fore-gut, and the two layers unite along the floors of the
grooves to form thin closing membranes between the fore-gut and the exterior.
Later the mesoderm again penetrates between the entoderm and the ectoderm.
In gill-bearing animals the closing membranes disappear, and the grooves become
5
66
EMBRYOLOGY
Lateral tongue Thyroid
elevations diverticvlum
complete clefts, the gill-clefts, opening from the pharynx on to the exterior; perfo-
ration, however, does not occur in birds or mammals. The grooves separate a
series of rounded bars or arches, the branchial or visceral arches, in which thickening
of the mesoderm takes place (Figs. 40 and 41). The dorsal ends of these arches
are attached to the sides of the head, while the ventral extremities ultimately
meet in the middle line of the neck. In all, six arches make their appearance,
but of these only the first four are visible externally. The first arch is named the
mandibular, and the second the hyoid; the
others have no distinctive names. In each
arch a cartilaginous bar, consisting of right
and left halves, is developed, and with each
of these there is one of the primitive aortic
arches.
The mandibular arch lies between the first
branchial groove and the stomodeum; from it
are developed the lower lip, the mandible,
the muscles of mastication, and the anterior
part of the tongue. Its cartilaginous bar is
formed by what are known as Meckel's carti-
lages (right and left) (Fig. 43) ; above this the
incus is developed. The dorsal end of each
cartilage is connected with the ear-capsule
and is ossified to form the malleus; the ventral ends meet each other in the region
of the symphysis menti, and are usually regarded as undergoing ossification to form
that portion of the mandible which contains the incisor teeth. The intervening
part of the cartilage disappears; the portion immediately adjacent to the malleus is
replaced by fibrous membrane, which constitutes the spheno-mandibular ligament,
Entrance to
larynx
Fig. 42. — Floor of pharvux of embryo shown in
Fig. 40.
Malleus
Incus
Tympanic ring
■ Jlandible
■ ~- Meckel's cartilage
Hyoid hone
Fig. 43. — Head and neck of a human embryo eighteen weeks old, with Meckel's cartilage and hyoid bar exposed.
(After KoUiker.)
while from the connective tissue covering the remainder of the cartilage the greater
part of the mandible is ossified. From the dorsal ends of the mandibular arch a
triangular process, the maxillary process, grows forward on either side and forms
the cheek and lateral part of the upper lip. The second or hyoid arch assists in
forming the side and front of the neck. From its cartilage are developed the styloid
process, stylohyoid ligament, and lesser cornu of the hyoid bone. The stages prob-
THE BRANCHIAL REGION
G7
ably arises in the upper part of this arch. Tlie cartilage of the third arch gives origin
to the greater cornu of the hyoid bone. The ventral ends of the second and third
arches unite with those of the opposite side, and form a transverse band, from
which the body of the hyoid bone and the posterior part of the tongue are devel-
oped. The ventral portions of the cartilages of the fourth and fifth arches unite
to form the thyroid cartilage; from the cartilages of the sixth arch the cricoid
and arytenoid cartilages and the cartilages of the trachea are developed. The
mandibular and hyoid arches grow more rapidly than those behind them, with
the result that the latter become, to a certain extent, telescoped within the
former, and a deep depression, the sinus cervicalis, is formed on either side of
the neck. This sinus is bounded in front by the hyoid arch, and behind by the
thoracic wall; it is ultimately obliterated by the fusion of its walls.
From the first branchial groove the concha auricuke and external acoustic
meatus are developed, while around the groove there appear, on the mandibular
and hyoid arches, a number of swellings from which the auricula or pinna is formed.
The first pharyngeal pouch is prolonged dorsally to form the auditory tube and the
tympanic cavity; the closing membrane between the mandibular and hyoid arches
Memhranoiis capsule over cerebral hemisphere
Fronto-nasal process
Stomodeiun
Lateral nasal process
Eije
Globular process
Maxillary process
Mandibular arch
Hyomandibular deft
Fig. 44. — Under surface of the head of a human embryo about twenty-nine daj's old. (After His.) '
is invaded by mesoderm, and forms the tympanic membrane. No traces of the
second, third, and fourth branchial grooves persist. The inner part of the second
pharyngeal pouch is named the sinus tonsillaris ; in it the tonsil is developed, above
which a trace of the sinus persists as the supratonsillar fossa. The fossa of Rosen-
miiller or lateral recess of the pharynx is by some regarded as a persistent part of
the second pharyngeal pouch, but it is probably developed as a secondary forma-
tion. From the third pharyngeal pouch the thymus arises as an entodermal diver-
ticulum on either side, and from the fourth pouches small diverticula project and
become incorporated with the thymus, but in man these diverticula probably
never form true thymus tissue. The parathyroids also arise as diverticula from
the third and fourth pouches. From the fifth pouches the ultimobranchial bodies
originate and are enveloped by the lateral prolongations of the median thyroid
rudiment; they do not, however, form true thyroid tissue, nor are any traces
of them found in the human adult.
The Nose and Face. — During the third week two areas of thickened ectoderm, the
olfactory areas, appear immediately under the fore-brain in the anterior wall of the
stomodeum, one on either side of a region termed the fronto-nasal process (Fig. 44).
By the upgrowth of the surrounding parts these areas are converted into pits.
68
EMBRYOLOGY
the olfactory pits, which indent the fronto-nasal process and divide it into a
medial and two lateral nasal processes (Fig. 45). The rounded lateral angles of
the medial process constitute the globular processes of His. The olfactory pits form
Future apex of nose
Medial nasal process
Olfactory pit
Lateral na.sal process
Glchular process
Maxillary process
Stoinodeum
Mandibular arch
Future apex of nose
Medial nasal process
Olfactory pit
Lateral nasal process
Globular process
Maxillary process
Hoof of pharynx
Hypophyseal diverticulum
Dorsal uxill of pharynx
Fig. 45. — Head end of human embryo of about thirty
to thirty-one days. (From model by Peters.)
Fig. 46. — Same embryo as shown in Fig. 45, with front
wall of pharynx removed.
the rudiments of the nasal cavities, and from their ectodermal lining the epithe-
lium of the nasal cavities, with the exception of that of the inferior meatuses, is
<leri\ ed. The globular processes are prolonged backward as plates, termed the nasal
laminae: these laminae are at first some distance apart, but, gradually approach-
Lateral nasal pro-
cess
Globular processes
Fig. 47. — Head of a human embryo of
about eight weeks, in which the nose and
mouth are formed. (His.)
Fig. 48. — Diagram showing the regions of the adult face and neck
related to the fronto-nasal process and the branchial arches.
ing, they ultimately fuse and form the nasal septum; the processes themselves
meet in the middle line, and form the premaxillae and the philtrum or central
part of the upper lip (Fig. 48). The depressed part of the medial nasal process
THE BRANCHIAL REGION
69
between the globular processes forms the lower part of the nasal septum or
columella; while above this is seen a prominent angle, which becomes the future
apex (Figs. 45, 46), and still higher a flat area, the future bridge, of the nose.
The lateral nasal processes form the alae of the nose.
Continuous with the dorsal end of the mandibular arch, and growing forward
from its cephalic border, is a triangular process, the maxillary process, the ventral
extremity of which is separated from the mandibular arch by a > shaped notch
Nares
Primitive
palate
Nasal
cavity
Bucconasal
niembranes
Fig. 49. — Primitive palate of a human embryo of thirty-seven to thirty-eight days. (From model by Peters.)
On the left side the lateral wall of the nasal cavity has been removed.
(Fig. 44). The maxillary process forms the lateral wall and floor of the orbit,
and in it are ossified the zygomatic bone and the greater part of the maxilla; it
meets with the lateral nasal process, from which, however, it is separated for a
time by a groove, the naso-optic furrow, that extends from the furrow encircling
the eyeball to the olfactory pit. The maxillary processes ultimately fuse with the
lateral nasal and globular processes, and form the lateral parts of the upper lip
Globtdar process
\
Palatine process of
globular proces6
Palatine part of
maxillary process
Maxillary process
Mouth of olfactory
pit, or naris
Pharynx
Fig. 50 — The roof of the mouth of a human embryo, aged about two and a half months, showing the mode of
formation of the palate. (His.)
and the posterior boundaries of the nares (Figs. 47, 48). From the third to
the fifth month the nares are filled by masses of epithelium, on the breaking down
and disappearance of which the permanent openings are produced. The maxillary
process also gives rise to the lower portion of the lateral wall of the nasal cavity.
The roof of the nose and the remaining parts of the lateral wall, viz., the ethmoidal
labyrinth, the inferior nasal concha, the lateral cartilage, and the lateral crus of
the alar cartilage, are developed in the lateral nasal process. By the fusion of the
70
EMBRYOLOGY
maxillary and nasal processes in the roof of the stomodeum the primitive palate
(Fig. 49) is formed, and the olfactory pits extend backward above it. The pos-
terior end of each pit is closed by an epithelial membrane, the bucco-nasal membrane,
formed by the apposition of the nasal and stomodeal epithelium. By the rupture
of these membranes the primitive choanae or openings between the olfactory pits
and the stomodeum are established. The jfloor of the nasal cavity is completed
by the development of a pair of shelf-like palatine processes which extend medial-
ward from the maxillary processes (Figs. 50 and 51); these coalesce with each
other in the middle line, and constitute the entire palate, except a small part in
front which is formed by the premaxillary bones. Two apertures persist for a time
between the palatine processes and the premaxillse and represent the permanent
channels which in the lower animals connect the nose and mouth. The union of
the parts which form the palate commences in front, the premaxillary and palatine
processes joining in the eighth week, while the region of the future hard palate
Lateral 'part of^
nasal capsule
Inferior meatus
Vomeronasal
cartilage
Palatine process-
Cartilage of
nasal septum
omeronasal
organ of Jacobson
75-\;'v-.5;;)?'^.v;:.
fy( -M^^-'-
• Inferior meatus
m
Cavity of mouth
Fig. 51. — Frontal section of nasal cavities of a human embryo 28 mm. long. (Kollmann.)
is completed by the ninth, and that of the soft palate by the eleventh week. By
the completion of the palate the permanent choanae are formed and are situated a
considerable distance behind the primiti\"e choanse. The deformity known as
cleft palate results from a non-union of the palatine processes, and that of hare-
lip through a non-union of the maxillary and globular processes (see page 199).
The nasal cavity becomes divided by a vertical septum, which extends downward
and backward from the medial nasal process and nasal laminae, and unites below
with the palatine processes. Into this septum a plate of cartilage extends from
the under aspect of the ethmoid plate of the chodrocranium. The anterior part
of this cartilaginous plate persists as the septal cartilage of the nose and the medial
crus of the alar cartilage, but the posterior and upper parts are replaced by the
vomer and perpendicular plate of the ethmoid. On either side of the nasal septum,
at its lower and anterior part, the ectoderm is invaginated to form a blind pouch
or diverticulum, which extends backward and upward into the nasal septum and
is supported by a curved plate of cartilage. , These pouches form the rudiments of
THE BRANCHIAL REGION
71
the vomero-nasal organs of Jacobson, which open below, close to the junction
of the premaxillary and maxillary bones.
The Limbs. — The limbs begin to make their appearance in the third week as
small elevations or buds at the side of the trunk (Fig. 52). Prolongations from
the muscle- and cutis-plates of several primitive segments extend into each bud,
and carry with them the anterior divisions of the corresponding spinal nerves.
The nerves supplying the limbs indicate the number of primitive segments which
contribute to their formation — the upper limb being derived from seven, viz.,
fourth cervical to second thoracic inclusive, and the lower limb from ten, viz.,
twelfth thoracic to fourth sacral inclusive. The axial part of the mesoderm of
the limb-bud becomes condensed and converted into its cartilaginous skeleton,
and by the ossification of this the bones of the limbs are formed. By the sixth
week the three chief divisions of the limbs are marked off by furrows — the upper
into arm, forearm, and hand; the lower into thigh, leg, and foot (Fig. 53). The
limbs are at first directed backward nearly parallel to the long axis of the trunk,
Heart
Mandibu
Maxillary piocess
Auricula
- Fure-limb
Hind-limb
Fig. 52. — Human embryo from thirty-one to thirty-
four days. (His.)
Umbilical cord
Fig. 53. — Embryo of about six weeks. (His.
and each presents two surfaces and two borders. Of the surfaces, one — the future
flexor surface of the limb — is directed ventrally; the other, the extensor surface,
dorsally; one border, the preaxial, looks forward toward the cephalic end of the
embryo, and the other, the postaxial, backward toward the caudal end. The lateral
epicondyle of the humerus, the radius, and the thumb lie along the preaxial border
of the upper limb; and the medial epicondyle of the femur, the tibia, and the great
toe along the corresponding border of the lower limb. The preaxial part is derived
from the anterior segments, the postaxial from the posterior segments of the limb-
bud; and this explains, to a large extent, the innervation of the adult limb, the
nerves of the more anterior segments being distributed along the preaxial (radial
or tibial), and those of the more posterior along the postaxial (ulnar or fibular)
border of the limb. The limbs next undergo a rotation or torsion through an angle
of 90° around their long axes the rotation being effected almost entirely at the
limb girdles. In the upper limb the rotation is outward and forward; in the lower
limb, inward and backward. As a consequence of this rotation the preaxial (radial)
72
EMBRYOLOGY
border of the fore-limb is directed lateralward, and the preaxial (tibial) border
of the hind-limb is directed mediahvard; thus the flexor surface of the fore-limb
is turned forward, and that of the hind-limb backward.
DEVELOPMENT OF THE BODY CAVITIES.
In the human embryo described by Peters the mesoderm outside the embryonic
^isk is split into two layers enclosing an extra-embryonic coelom; there is no trace
of an intra-embryonic coelom. At a later stage four cavities are formed within the
embryo, viz., one on either side within the mesoderm of the pericardial area, and
one in either lateral mass of the general mesoderm. All these are at first independent
of each other and of the extra-embryonic celom, but later they become continuous.
The two cavities in the general mesoderm unite on the ventral aspect of the gut
and form the pleuro-peritoneal cavity, which becomes continuous with the remains
of the extra-embryonic celom around the umbilicus; the two, cavities in the peri-
cardial area rapidly join to form a single pericardial cavity, and this from two lateral
diverticula extend caudalward to open into the pleuro-peritoneal cavity (Fig. 54).
Mesentery
Pleural cav>ty\^
iMtvg.
Phuro- pericardial.—
opening
Pericardium
Mesoderm
surrounding
duct ofCuvier
■'] -Dorsal mesocardiv/m
'~\"~Heart
Fig. 54. — Figure obtained by combining several successive sections of a human embryo of about the fourth week
(From KoUmann.) The upper arrow is in the pleuroperitoneal opening, the lower in the pleuropericardial.
Between the two latter diverticula is a mass of mesoderm containing the ducts
of Cuvier, and this is continuous ventrally with the mesoderm in which the umbili-
cal veins are passing to the sinus venosus. A septum of mesoderm thus extends
across the body of the embryo. It is attached in front to the body-wall between
the pericardium and umbilicus; behind to the body-wall at the level of the second
cervical segment; laterally it is deficient where the pericardial and pleuro-peri-
toneal cavities communicate, while it is perforated in the middle line by the fore-
gut. This partition is termed the septum transversum, and is at first a bulky plate
of tissue. As development proceeds the dorsal end of the septum is carried grad-
ually caudalward, and when it reaches the fifth cervical segment muscular tissue
with the phrenic nerve grows into it. It continues to recede, however, until it
reaches the position of the adult diaphragm on the bodies of the upper lumbar
vertebrae. The liver buds grow into the septum transversum and undergo
development there.
The lung buds meantime have grown out from the fore-gut, and project laterally
into the forepart of the pleuro-peritoneal cavity; the developing stomach and liver
are imbedded in the septum transversum; caudal to this the intestines project into
the back part of the pleuro-peritoneal cavity (Fig. 55). Owing to the descent of
DEVELOPMENT OF THE BODY CAVITIES
73
the dorsal end of the septum transversum the lung buds come to lie above tlie
septum and thus pleural and peritoneal portions of the pleuro-peritoneal cavity
(still, however, in free communication with one another) may be recognized; the
pericardial cavity opens into the pleural part.
Left due of Cuvier Esofliagus Bight duct of Cuvier
Me.ioderm
surrounding duct
Pleura- pericardial
opening
Rid'je growing across
opening
Omental bursa — r
Stomach i
—Dorsal mesentery
Peritoneal recess
Fia. 55. — Upper part of celom of human embryo of 6.8 mm., seen from behind. (From model by Piper.)
The ultimate separation of the permanent cavities from one another is effected
by the growth of a ridge of tissue on either side from the mesoderm surrounding
Msopliagus
Aorta
Pleural cavity
Lung
Inferior vena cava
YBody wall
Pericardium
Fia. 56. — Diagram of transverse section through rabbit embryo, (.\fter Keith.)
the duct of Cuvier (Figs. 54, 55). The front part of this ridge grows across and
obliterates the pleuro-pericardial opening; the hinder part grows across the pleuro-
peritoneal opening.
With the continued growth of the lungs the pleural cavities are pushed forward
74
EMBRYOLOGY
in the body-wall toward the ventral median line, thus separating the pericardium
from the lateral thoracic walls (Fig. 53) . The further development of the peritoneal
cavity has been described with the development of the digestive tube (page 168
et seq.).
Stemn-cnstal 2>art of
JJiaphra(/ina
Central tendon of Diaphragm a
Inferior vena cava
Spleen
Colon
Suprarenal gland
Eleventh rib
Twelfth rib
(Esophagus
Vertebral part of Diaphragma
Posterior tnediastinal cavity
Aorta
Spino-costal hiatus
Left pleura
Right pleura
Fig. 57. — The thoracic aspect of the diaphragm of a newly born child in which the communication between the
peritoneum and pleura has not been closed on the left side; the position of the opening is marked on the right side by
the spinocostal hiatus. (After Keith.)
THE FORM OF THE EMBRYO AT DIFFERENT STAGES OF ITS GROWTH.
First Week. — During this period the ovum is in the uterine tube. Having been fertiHzed in
the upper part of the tube, it slowly passes down, undergoing segmentation, and reaches the
uterus. Peters' described a specimen, the age of which he reckoned as from three to four days.
It was imbedded in the decidua on the posterior wall of the uterus and enveloped by a decidua
capsularis, the central part of which, however, consisted merely of a layer of fibrin. The ovum
was in the form of a sac, the outer wall of which consisted of a layer of trophoblast; inside thia
Arrmion
Heart
Body-stalk
Chorion
Fig. 58. — Human embryo about fifteen day-s old.
(His.)
was a thin layer of mesoderm composed of round, oval, and spindle-shaped cells. Numerous
villous processes — some consisting of trophoblast only, others possessing a core of mesoderm —
projected from the surface of the ovum into the surrounding decidua. Inside this sac the rudi-
ment of the embryo was found in the form of a patch of ectoderm, covered by a small but com-
1 Die Einbettung des menschlichen Eies, 1899.
FORM OF THE EMBRYO AT DIFFERENT STAGES OF ITS GROWTH 75
pletely closed amnion. It possessed a minute yolk-sac and was surrounded by mesoderm, which
was connected by a band to that lining the trophoblast (Fig. 32).^
Second Week. — By the end of this week the ovum has increased considerably in size, and the
majority of its vilU are vascularized. The embryo has assumed a definite form, and its cephahc
and caudal extremities are easily distinguished. The neural folds are partly united. The embryo
Mid-brain
Fore-hram
Stomodeum
Mandibular arch
Heart
Hind-brain
Auditory vesicle
^ Visceral
arches
Amnion (cut)
Body-stalk
Fig. 59. — Human embryo between eighteen and twenty-one days old. (His.
is more completely separated from the yolk-sac, and the paraxial mesoderm is being divided into
the primitive segments (Fig. 58).
Third Week. — By the end of the third week the embryo is strongly curved, and the primitive
segments number about thirty. The primary divisions of the brain are visible, and the optic
Fore-htnb
Hyoid arch
. Mandibular arch
Maxillary process
Eye
Olfactory pit
Chorion ^ CL
Fig. 60.-
•r, .J , Hind-hmh
-Human embryo, twenty-seven to thirty days old. (His.)
and auditory vesicles are formed. Four branchial grooves are present: the stomodeum is well-
marked, and the bucco-pharyngeal membrane has disappeared. The rudiments of the hmbs
are seen as short buds, and the Wolffian bodies are visible (Fig. 59).
1 Bryce and Teacher (Early Deielopment and Imbedding of (he Human Ovum, 190S) have described an ovum which
they regard as thirteen to fourteen days old. In it the two vesicles, the amnion and yolk-sac, were present, but there
was no trace of a layer of embryonic ectoderm. They are of opinion that the age of Peters ovum has been understated,
and estimate it as between thirteen and one-half and fourteen and one-half days.
76
EMBRYOLOGY
Fourth Week. — The embryo is markedly curved on itself, and when viewed in profile is almost
circular in outhne. The cerebral hemispheres appear as hollow buds, and the elevations which
form the rudiments of the auricula are visible. The limbs now appear as oval flattened projec-
tions (Fig. 60).
Heart
Hyoid arch
Mandibular arch
Maxillary process
Eye
Fore-limb
Hind-limh
Fig. 01. — Human embryo, thirty-one to thirty-four days old. (His.)
Fifth Week. — The embryo is less curved and the head is relatively of large size. Differentiation
of the limbs into their segments occurs. The nose forms a short, flattened projection. The cloacal
tubercle is evident (Fig. Gl).
Auricula
Fore-limb
Mind-limb
Umbilical cord
Fig. 62. — Human embryo of about six weeks.
(His.)
Fig. 63. — Human embryo about eight and a half
weeks old. (His.)
Sixth Week.— The curvature of the embryo is further diminished. The branchial grooves—
except the first — have disappeared, and the rudiments of the fingers and toes can be recognized
(Fig. 62).
Seventh and Eighth Weeks. — The flexure of the head is gradually reduced and the neck is
somewhat lengthened. The upper lip is completed and the nose is more prominent. The nostrils
FORM OF THE EMBRYO AT DIFFERENT STAGES OF ITS GROWTH 77
are directed forward and the palate is not completely developed. The eyelids are present in the
shape of folds above and below the eye, and the different parts of the auricula are distinguish-
able. • By the end of the second month the fetus measures from 28 to 30 mm. in length (Fig. 63).
Third Month.— The head is extended and the neck is lengthened. The eyelids meet and fuse,
remaining closed until the end of the sixth month. The limbs are well-developed and nails appear
on the digits. The external generative organs are so far differentiated that it is possible to dis-
tinguish the sex. By the end of this month the length of the fetus is about 7 cm., but if the legs
be included it is from 9 to 10 cm.
Fourth Month. — The loop of gut which projected into the umbiUcal cord is withdrawn withm
the fetus. The hairs begin to make their appearance. There is a general increase in size so that
by the end of the fourth month the fetus is from 12 to 13 cm. in length, but if the legs be included
it is from 16 to 20 cm.
Fifth Month. — It is during this month that the first movements of the fetus are usually ob-
served The eruption of hair on the head commences, and the vernix caseosa begins to be deposited.
By the end of this month the total length of the fetus, including the legs, is from 25 to 27 cm
Sixth Month. — The body is covered by fine hairs (lanugo) and the deposit of vernix caseosa
is considerable. The papillae of the skin are developed and the free border of the nail projects
from the corium of the dermis. Measured from vertex to heels, the total length of the fetus
at the end of this month is from 30 to 32 cm.
Seventh Month. — ^The pupillary membrane atrophies and the eyehds are open. The testis
descends with the vaginal sac of the peritoneum. From vertex to heels the total length at the
end of the seventh month is from 35 to 36 cm. The weight is a little over three pounds.
Eighth Month. — The skin assumes a pink color and is now entirely coated with vernix caseosa,
and the lanugo begins to disappear. Subcutaneous fat has been developed to a considerable
extent, and the fetus presents a plump appearance. The total length, i. e., from head to heels,
at the end of the eighth month is about 40 cm., and the weight varies between four and one-half
and five and one-half pounds.
Ninth Month. — The lanugo has largely disappeared from the trunk. The umbihcus is almost
in the middle of the body and the testes are in the scrotum. At full time the fetus weighs from
six and one-half to eight pounds, and measures from head to heels about 50 cm.
BIBLIOGRAPHY.
Broman: Normal e und abnorme Entwicklung des Menschen, 1911.
Bryce, Teacher and Kerr: Contributions to the Study of the Early Development and
Imbedding of the Human Ovum, 1908.
Hertwig, O.: Handbuch der Vergleichenden und Experimentellen Entwicklungslehre der
Wirbeltiere, 1906.
His, W. : Anatomic menschlicher Embryonen, 1883-1885.
Hochstetter, F.: Bilder der iiusseren Koperform einiger menschlicher Embryonen aus den
beiden ersten Monaten der Entwicklung, 1907.
Keibel and Elze: Normentafel zur Entwicklungsgescliichte des Menschen, 1908.
Keibel and Mall: Manual of Human Embryology, 1910-1912.
KOLLMANN, J
KOLLMANN, J.
Handatlas der Entwickhmgsgeschichte des Menschen, 1907.
Lehrbuch der Entwicklungsgescliichte des Menschen, 1898.
Mall: Contribution to the Study of the Pathology of the Human Embryo, Jour, of Morph.,
1908. See also contributions to Embryology of the Carnegie Institution of Washington.
Mall: Development of the Human Ccelom, Jour, of Morph., 1897.
Peters, H.: Ueber die Einbettung des menschl ichen Eies und das friiheste bisher bekannte
menschliche Placentationsstadium, 1899.
OSTEOLOGY.
rpHE general framework of the body is built up mainly of a series of bones,
-L supplemented, however, in certain regions by pieces of cartilage; the bony
part of the framework constitutes the skeleton.
In the skeleton of the adult there are 206 distinct bones, as follows:—
' Vertebral column . . . . .26
Axial I Skull 22
Skeleton | Hyoid bone ... . . . .1
, Ribs and sternum . . . . .25
— 74
Appendicular / Upper extremities 64
Skeleton \ Lower extremities . . . . .62
— 126
Auditory ossicles ........ 6
Total ..... 206
The patellae are included in this enumeration, but the smaller sesamoid bones
are not reckoned.
Bones are divisible into four classes: Long, Short, Flat, and Irregular.
Long Bones. — The long bones are found in the limbs, and each consists of a body
or shaft and two extremities. The body, or diaphysis is cylindrical, with a central
cavity termed the medullary canal; the wall consists of dense, compact tissue
of considerable thickness in the middle part of the body, but becoming thinner
toward the extremities; within the medullary canal is some cancellous tissue,
scanty in the middle of the body but greater in amount toward the ends. The
extremities are generally expanded, for the purposes of articulation and to afford
broad surfaces for muscular attachment. They are usually developed from sep-
arate centers of ossification termed epiphyses, and consist of cancellous tissue
surrounded by thin compact bone. The medullary canal and the spaces in the
cancellous tissue are filled with marrow.- The long bones are not straight, but
curved, the curve generally taking place in two planes, thus afi'ording greater
strength to the bone. The bones belonging to this class are: the clavicle, humerus,
radius, ulna, femur, tibia, fibula, metacarpals, metatarsals, and phalanges.
Short Bones. — Where a part of the skeleton is intended for strength and com-
pactness combined with limited movement, it is constructed of a number of short
bones, as in the carpus and tarsus. These consist of cancellous tissue covered
by a thin crust of compact substance. The patellae, together with the other
sesamoid bones, are by some regarded as short bones.
Flat Bones. — Where the principal requirement is either extensive protection or
the provision of broad surfaces for muscular attachment, the bones are expanded
into broad, flat plates, as in the skull and the scapula. These bones are composed
of two thin layers of compact tissue enclosing between them a variable quantity
of cancellous tissue. In the cranial bones, the layers of compact tissue are famili-
arly known as the tables of the skull; the outer one is thick and tough; the inner
is thin, dense, and brittle, and hence is termed the vitreous table. The intervening
(79)
80 OSTEOLOGY
cancellous tissue is called the diploe, and this, in certain regions of the skull,
becomes absorbed so as to leave spaces filled with air (air-sinuses) between
the two tables. The flat bones are: the occipital, parietal, frontal, nasal, lacrimal,
vomer, scapula, os coxae (hip hone), sternum, ribs, and, according to some, the
patella.
Irregular Bones. — The irregular bones are such as, from their peculiar form,
cannot be grouped under the preceding heads. They consist of cancellous tissue
enclosed within a thin layer of compact bone. The irregular bones are: the
vertebrae, sacrum, coccyx, temporal, sphenoid, ethmoid, zygomatic, maxilla, mandible,
palatine, inferior nasal concha, and hyoid.
Surfaces of Bones. — If the surface of a bone be examined, certain eminences
and depressions are seen. These eminences and depressions are of two kinds:
articular and non-articular. Well-marked examples of articular eminences are
found in the heads of the humerus and femur; and of articular depressions in the
glenoid cavity of the scapula, and the acetabulum of the hip bone. Non-articular
eminences are designated according to their form. Thus, a broad, rough, uneven
elevation is called a tuberosity, protuberance, or process, a small, rough prominence,
a tubercle ; a sharp, slender pointed eminence, a spine ; a narrow, rough elevation,
running some way along the surface, a ridge, crest, or line. Non-articular depres-
sions are also of variable form, and are described as fossae, pits, depressions, grooves,
furrows, fissures, notches, etc. These non-articular eminences and depressions serve
to increase the extent of surface for the attachment of ligaments and muscles, and
are usually well-marked in proportion to the muscularity of the subject. A short
perforation is called a foramen, a longer passage a canal.
DEVELOPMENT OF THE SKELETON.
The Skeleton. — The skeleton is of mesodermal origin, and may be divided into
(a) that of the trunk (axial skeleton), comprising the vertebral column, skull, ribs,
and sternum, and (h) that of the limbs (appendicular skeleton).
The Vertebral Column. — The notochord (Fig. 19) is a temporary structure and
forms a central axis, around which the segments of the vertebral column are devel-
oped.^ It is derived from the entoderm, and consists of a rod of cells, M'hich lies
on the ventral aspect of the neural tube and reaches from the anterior end of the
mid-brain to the extremity of the tail. On either side of it is a column of paraxial
mesoderm which becomes subdivided into a number of more or less cubical seg-
ments, the primitive segments (Figs. 19 and 20). These are separated from one
another by intersegmental septa and are arranged symmetrically on either side of
the neural tube and notochord: to every segment a spinal nerve is distributed.
At first each segment contains a central cavity, the myoccel, but this is soon filled
with a core of angular and spindle-shaped cells. The cells of the segment become
differentiated into three groups, which form respectively the cutis-plate or derma-
tome, the muscle-plate or myotome, and the sclerotome (Fig. 64). The cutis-plate
is placed on the lateral and dorsal aspect of the myocoel, and from it the true skin
of the corresponding segment is derived; the muscle-plate is situated on the medial
side of the cutis-plate and furnishes the muscles of the segment. The cells of the
sclerotome are largely derived from those forming the core of the myocoel, and lie
next the notochord. Fusion of the individual sclerotomes in an antero-posterior
direction soon takes place, and thus a continuous strand of cells, the sclerotogenous
layer, is formed along the ventro-lateral aspects of the neural tube. The cells of
this layer proliferate rapidly, and extending medialward surround the notochord;
at the same time they grow backward on the lateral aspects of the neural tube
and eventually surround it, and thus the notochord and neural tube are enveloped
' In the amphioxus the notochord persists and forms the only representative of a skeleton in that animal.
DEVELOPMENT OF THE SKELETON
81
by a continuous sheath of mesoderm, which is termed the membranous vertebral
colimin. In this mesoderm the original segments are still distinguishable, but each
is now differentiated into
two portions, an anterior,
consisting of loosely arranged
cells, and a posterior, of
more condensed tissue (Fig.
65, A and B) . Between the
two portions the rudiment
of the intervertebral fibro- ^•'^•
cartilage is laid down (Fig.
65, C). Cells from the pos-
terior mass grow into the
intervals between the myo-
tomes (Fig. 65, B and C) of
the corresponding and suc-
ceeding segments, and extend
both dorsally and ventrally;
the dorsal extensions sur-
round the neural tube and
represent the future verte-
bral arch, while the ventral
extend into the body-wall
as the costal processes. The
hinder part of the posterior
mass joins the anterior mass
of the succeeding segment
to form the vertebral body.
Each vertebral body is there-
fore a composite of two segments, being formed from the posterior portion of
one segment and the anterior part of that immediately behind it. The vertebral
Fig. G4. — Transverse section of a human embryo of the third week
to show the difTerentiation of the primitive segment. (Kollmann.) ao.
Aorta. m.p. Muscle-plate, n.c. Neural canal, sc. Sclerotome, s p.
cutis-plate.
Myotome
j Anterior portion cf sclerotome
Notochord
Posterior portion of sclerotome
Intermyotomic septum
Costal process
• ■•*
T"^
• ••
*•• •
•v.v-
• •••'
Intervertebral
fibrocartilage
Notochord
trum
<•• • •
• •••
V.VAV.V
• tff f •
• « • « e
»•• ••
• • • * •
• • • * • "^ —
Iv.*.*.?^
B
Fig. 05. — Scheme showing the manner in which each vertebral centrum is developed from portions of two adjacent
segments.
and costal arches are derivatives of the posterior part of the segment in front
of the intersegmental septum with which they are associated.
6
82
OSTEOLOGY
This stage is succeeded by that of the cartilaginous vertebral column. In the
fourth week two cartilaginous centers make their appearance, one on either side of
the notochord; these extend around tlie notochord and form the body of the cartil-
aginous vertebra. A second pair of cartilaginous foci appear in the lateral parts of
the vertebral bow, and grow backward on either side of the neural tube to form
the cartilaginous vertebral arch, and a separate cartilaginous center appears for
each costal process. By the eighth week the cartilaginous arch has fused with the
body, and in the fourth month the two halves of the arch are joined on the dorsal
aspect of the neural tube. The spinous process is developed from the junction of
the two halves of the vertebral arch. The transverse process grows out from the
vertebral arch behind the costal process.
In the upper cervical vertebrae a band of mesodermal tissue connects the ends of
the vertebral arches across the ventral surfaces of the intervertebral fibrocartilages.
This is termed the hypochordal bar or brace; in all except the first it is transitory
and disappears by fusing with the fibrocartilages. In the atlas, however, the entire
bow persists and undergoes chondrification; it develops into the anterior arch of the
bone, while the cartilage representing the body of the atlas forms the dens or
odontoid process which fuses with the body of the second cervical vertebra.
Anterior
longitudinal
ligament
Posteriorlongitudinal
ligament
Cartilaginous end
of vertebral body
Niicleus 'pulposv^
Intervertebral fibro-
cartilage
Slight enlargement
of notochord in
the cartilaginous
vertebral body
Fig. 66. — Sagittal section through an intervertebral fibrocartilage and adjacent parts of two vertebrae of an advanced
sheep's embrj'o. (Kolliker.)
The portions of the notochord which are surrounded by the bodies of the verte-
brae atrophy, and ultimately disappear, while those which lie in the centers of the
intervertebral fibrocartilages undergo enlargement, and persist throughout life as
the central nucleus pulposus of the fibrocartilages (Fig. 66).
The Ribs. — The ribs are formed from the ventral or costal processes of the
primitive vertebral bows, the processes extending between the muscle-plates. In
the thoracic region of the vertebral column the costal processes grow lateralward to
form a series of arches, the primitive costal arches. As already described, the
transverse process grows out behind the vertebral end of each arch. It is at first
connected to the costal process by continuous mesoderm, but this becomes differ-
entiated later to form the costotransverse ligament; between the costal process
and the tip of the transverse process the costotransverse joint is formed by
absorption. The costal process becomes separated from the vertebral bow by the
development of the costocentral joint. In the cervical vertebroB (Fig. 67) the trans-
verse process forms the posterior boundary of the foramen trans versarium, while
the costal process corresponding to the head and neck of the rib fuses with the
DEVELOPMENT OF THE SKELETON
83
body of the vertebra, and forms the antero-lateral boundary of the foramen. The
distal portions of the primitive costal arches remain undeveloped; occasionally
the arch of the seventh cervical vertebra undergoes greater development, and by
the formation of costovertebral joints is separated off as a rib. In the Inmhar
region the distal portions of the primitive costal arches fail; the proximal portions
fuse with the transverse processes to form the transverse processes of descriptive
anatomy. Occasionally a movable rib is developed in connection with the first
lumbar vertebra. In the sacral region costal processes are developed only in
connection with the upper three, or it may be four, vertebra; the processes of
adjacent segments fuse with one another to form the lateral parts of the sacrum.
The coccygeal vertehrce are devoid of costal processes.
CERVICAL
LUMBAR
THORACIC
SACRAL
Fig. 67. — Diagrams showing the portions of the adult vertebrae derived respectively from the bodies, vertebral
arches, and costal processes of the embryonic vertebrae. The bodies are represented in yellow, the vertebral arches
in red, and the costal processes in blue.
The Sternum. — The ventral ends of the ribs become united to one another by a
longitudinal bar termed the sternal plate, and opposite the first seven pairs of ribs
these sternal plates fuse in the middle line to form the manubrium and body of the
sternum. The xiphoid process is formed by a backward extension of the sternal
plates.
The Skull. — Up to a certain stage the development of the skull corresponds with
that of the vertebral column ; but it is modified later in association with the expan-
sion of the brain-vesicles, the formation of the organs of smell, sight, and hearing,
and the development of the mouth and pharynx.
84
OSTEOLOGY
Fossa
hypophyseos
ParacJwrdal
cartilage
The notochord extends as far forward as the anterior end of the mid-brain, and
becomes partly surrounded by mesoderm (F'ig. 68) . The posterior part of this meso-
dermal investment corresponds with the basilar part of the occipital bone, and shows
a subdivision into four segments, which are separated by the roots of the hypo-
glossal nerve. The mesoderm then extends over the brain-vesicles, and thus the
entire brain is enclosed by a mesodermal
investment, which is termed the membran-
ous cranium. From the inner layer of this
the bones of the skull and the membranes
of the brain are developed; from the outer
layer the muscles, bloodvessels, true skin,
and subcutaneous tissues of the scalp. In
the shark and dog-fish this membranous
cranium undergoes complete chondrifi-
cation, and forms the cartilaginous skull
or chondrocranium of these animals. In
mammals, on the other hand, the process
of chondrification is limited to the base
of the skull — the roof and sides being
covered in by membrane. Thus the bones
of the base of the skull are preceded by
cartilage, those of the roof and sides
by membrane. The posterior part of the
base of the skull is developed around
the notochord, and exhibits a segmented
condition analogous to that of the vertebral column, while the anterior part arises
in front of the notochord and shows no regular segmentation. The base of the skull
may therefore be divided into (a) a chordal or vertebral, and (h) a prechordal or
prevertebral portion.
Mesoderm of base
of skull
Notochord
Anterior arch of atlas
Notochord
Body of axis
Third cervical
vertebra
Fig.
68. — Sagittal section of cephalic end of noto-
chord. (Keibel.)
Situation of olfactory pit
Ethmoid plate
aiid nasal Olfactory organ
septum^
Fossa
hypophyseos
Trabecula__
cranii
Situation of
auditory .
vesicle
Parachordal '
cartilage
Notochord'"
Extension around
7 olfactory organ
Foramina for
olfactory nerves
Eyeball
Fossa
hypophyseos
--Basilar plate
--Auditory vesicle
-'Notochord
Fig. 69. — Diagrams of the cartilaginous cranium. (Wiedersheim.
In the lower vertebrates two pairs of cartilages are developed, viz., a pair of
parachordal cartilages, one on either side of the notochord; and a pair of pre-
chordal cartilages, the trabeculse cranii, in front of the notochord (Fig. 60). The
parachordal cartilages (Fig. ()9) unite to form a basilar plate, from which the car-
tilaginous part of the occipital bone and the basi-sphenoid are developed. On the
lateral aspects of the parachordal cartilages the auditory vesicles are situated,
DEVELOPMENT OF THE SKELETON
85
and the mesoderm enclosing them is soon converted into cartilage, forming the
cartilaginous ear-capsules. These cartilaginous ear-capsules, which are of an oval
shape, fuse with the sides of the basilar plate, and from them arise the petrous
and mastoid, portions of the temporal bones. The trabeculse cranii (Fig. 69) are
two curved bars of cartilage which embrace the hypophysis cerebri; their posterior
ends soon unite with the basilar plate, while their anterior ends join to form the
ethmoidal plate, which extends forward between the fore-brain and the olfactory
pits. Later the trabeculae meet and fuse below the hypophysis, forming the floor
Crista galli
Cribriform plate
Meckel's cartilage
Malleus
Inciis
Int. acoristic meat.
Jug ula r Jorame n
Fossa svbarcuata t
Small wing of sphenoid
Optic foramen
Great wing of
sphenoid
Sella turcica
Dorsum selloe
Canal for facial
nerve
Ear capsule
Ductus endol.
Canal for hypoglossal nerve
Foramen magnum
Fig. 70. — Model of the chondrocranium of a human embryo, 8 cm. long. (Hertwig.) The membrane bones are
not represented.
of the fossa hypophyseos and so cutting off the anterior lobe of the hypophysis
from the stomodeum. The median part of the ethmoidal plate forms the bony
and cartilaginous parts of the nasal septum. P>om the lateral margins of the
trabecular cranii three processes grow out on either side. The anterior forms the
ethmoidal labyrinth and the lateral and alar cartilages of the nose; the middle
gives rise to the small wing of the sphenoid, while from the posterior the great
wing and lateral pterygoid plate of the sphenoid are developed (Figs. 70, 71).
The bones of the vault are of membranous formation, and are termed dermal or
covering bones. They are partly developed from the mesoderm of the membranous
86
OSTEOLOGY
cranium, and partly from that which Hes outside the entoderm of the fore-
gut. They comprise the upper part of the occipital squama (interparietal), the
squamse and tympanic parts of the temporals, the parietals, the frontal, the vomer,
the medial pterygoid plates, and the bones of the face. Some of them remain
distinct throughout life, e. g., parietal and frontal, while others join with the bones
of the chondrocranium, e. g., interparietal, squama? of temporals, and medial
pterygoid plates.
Recent observations have shown that, in mammals, the basi-cranial cartilage,
both in the chordal and prechordal regions of the base of the skull, is developed
as a single plate which extends from behind forward. In man, however, its posterior
part shows an indication of being developed from two chondrifying centers which
fuse rapidly in front and below. The anterior and posterior thirds of the cartilage
surround the notochord, but its middle third lies on the dorsal aspect of the noto-
chord, which in this region is placed between the cartilage and the wall of the
pharynx.
Optic foramen Small wing of sphenoid
Great wing of sphenoid
Nasal
capsule
Sept.
nasi
Maxilla
Palatine
bone
Vomer
Mandible
Cricoid cart
Thyroid cart
Styloid process
Fen. cocMeoB
Canal for hypoglossal
nerve
Fia. 71. — The same model as shown in Fig. 70 from the left side. Certain of the membrane bones of the right side
are represented in yellow. (Hertwig.)
BONE
Structure and Physical Properties. — Bone is one of the hardest structures of
the animal body; it possesses also a certain degree of toughness and elasticity.
Its color, in a fresh state, is pinkish-white externally, and deep red within. On
examining a section of any bone, it is seen to be composed of two kinds of tissue,
one of which is dense in texture, like ivory, and is termed compact tissue; the other
consists of slender fibers and lamellae, which join to form a reticular structure;
this, from its resemblance to lattice-work, is called cancellous tissue. The compact
tissue is always placed on the exterior of the bone, the cancellous in the interior.
The relative quantity of these two kinds of tissue varies in different bones, and
in different parts of the same bone, according as strength or lightness is requisite.
Close examination of the compact tissue shows it to be extremely porous, so that
the difference in structure between it and the cancellous tissue depends merely
upon the different amount of solid matter, and the size and number of spaces in
each; the cavities are small in the compact tissue and the solid matter between
BONE
87
them abundant, while in the cancellous tissue the spaces are large and the solid
matter is in smaller quantity.
Bone during life is permeated by vessels, and is enclosed, except where it is
coated with articular cartilage, in a fibrous membrane, the periosteum, by means
of which many of these vessels reach the hard tissue. If the periosteum be stripped
from the surface of the living bone, small bleeding points are seen which mark the
entrance of the periosteal vessels; and on section during life every part of the
bone exudes blood from the minute vessels which ramify in it. The interior of
each of the long bones of the limbs presents a cylindrical cavity filled w4th marrow
and lined by a highly vascular areolar structure, called the medullary membrane.
Thf, Strength
OF Bone Compared
WITH OTHER MATERIALS
Substance.
Weight in
pounds per
cubic foot.
Ultimate strength.
Pounds per square inch.
Tension.
Compression.
Shear.
Medium steel
490
170
46
65,000
1,.500
12,5001
13,2001
17,7001
60,000
15,000
7,0001
18,0001
24,0001
40,000
2,000
4,0002
11,800'i
7,1501
Granite
Oak, white
Compact bone (low) . . / .
Compact bone (high)
119
Periosteum.— The periosteum adheres to the surface of each of the bones in
nearly every part, but not to cartilaginous extremities. When strong tendons or
ligaments are attached to a bone, the periosteum is incorporated with them. It
consists of two layers closely united together, the outer one formed chiefly of
connective tissue, containing occasionally a few fat cells; the inner one, of elastic
fibers of the finer kind, forming dense membranous networks, which again can be
separated into several layers. In young bones the periosteum is thick and very
vascular, and is intimately connected at either end of the bone with the epiphysial
cartilage, but less closely with the body of the bone, from which it is separated by
a layer of soft tissue, containing a number of granular corpuscles or osteoblasts, by
which ossification proceeds on the exterior of the young bone. Later in life the
periosteum is thinner and less vascular, and the osteoblasts are converted into an
epithelioid layer on the deep surface of the periosteum. The periosteum serves
as a nidus for the ramification of the vessels previous to their distribution in the
bone; hence the liability of bone to exfoliation or necrosis when denuded of this
membrane by injury or disease. Fine nerves and lymphatics, w^hich generally
accompany the arteries, may also be demonstrated in the periosteum.
Marrow. — The marrow not only fills up the cylindrical cavities in the bodies of
the long bones, but also occupies the spaces of the cancellous tissue and extends
into the larger bony canals (Haversian canals) which contain the bloodvessels.
It differs in composition in different bones. In the bodies of the long bones the
marrow is of a yellow color, and contains, in 100 parts, 96 of fat, 1 of areolar tissue
and vessels, and 3 of fluid with extractive matter; it consists of a basis of connective
tissue supporting numerous bloodvessels and cells, most of which are fat cells
but some are "marrow cells," such as occur in the red marrow to be immediately
described. In the flat and short bones, in the articular ends of the long bones,
in the bodies of the vertebrae, in the cranial diploe, and in the sternum and ribs
the marrow is of a red color, and contains, in 100 parts, 75 of water, and 25 of solid
matter consisting of cell-globulin, nucleoprotein, extractives, salts, and only a
small proportion of fat. The red marrow consists of a small quantity of connective
tissue, bloodvessels, arid numerous cells (Fig. 72), some few of which are fat cells,
' Indicates stresses with the grain, i. e., when the load is parallel to the long axis of the material, or parallel to the
direction of the fibers of the material.
2 Indicates unit-stresses across the grain, i. c, at right angles to the direction of the fibers of the material.
88
OSTEOLOGY
but the great majority are roundish nucleated cells, the true "marrow cells"
of KoUiker. These marrow cells proper, or myelocytes, resemble in appearance
lymphoid corpuscles, and like them are ameboid; they generally have a hyaline
protoplasm, though some show granules either oxyphil or basophil in reaction.
A number of eosinophil cells are also present. Among the marrow cells may be
seen smaller cells, which possess a slightly pinkish hue; these are the erythroblasts
or normoblasts, from which the red corpuscles of the adult are derived, and which
may be regarded as descendants of the nucleated colored corpuscles of the embryo.
Giant cells {mycloplazes , osteoclasts), large, multinucleated, protoplasmic masses,
are also to be found in both sorts of adult marrow, but more particularly in red
marrow. They were believed by Kolliker to be concerned in the absorption of
bone matrix, and hence the name which he gave to them — osteoclasts. They
excavate in the bone small shallow pits or cavities, which are named Howship's
foveolae, and in these they are found lying.
Normoblast with dividing nucleus
Myelocyte — -~M
Erythrocyte -
Myeloflaxe -^-jn-i-
Myelocyte
Fat-
__ Eosinophil
cell
iJS^ Normoblasts
Myelocyte
dividing
Myelocyte
Fat
Fig. 72. — Human bone marrow. Highly magnified.
Vessels and Nerves of Bone. — The bloodvessels of bone are very numerous. Those
of the compact tissue are derived from a close and dense network of vessels ramify-
ing in the periosteum. From this membrane vessels pass into the minute orifices
in the compact tissue, and run through the canals which traverse its substance.
The cancellous tissue is supplied in a similar way, but by less numerous and larger
vessels, which, perforating the outer compact tissue, are distributed to the cavities
of the spongy portion of the bone. In the long bones, numerous apertures may
be seen at the ends near the articular surfaces; some of these give passage to the
arteries of the larger set of vessels referred to; but the most numerous and largest
apertures are for some of the veins of the cancellous tissue, which emerge apart
from the arteries. The marrow in the body of a long bone is supplied by one
large artery (or sometimes more), which enters the bone at the nutrient foramen
(situated in most cases near the center of the body), and perforates obliquely the
compact structure. The medullary or nutrient artery, usually accompanied by one
or two veins, sends branches upward and downward, which ramify in the medul-
lary membrane, and give twigs to the adjoining canals. The ramifications of this
BONE
89
vessel anastomose with the arteries of the cancellous and compact tissues. In most
of the flat, and in many of the short spongy bones, one or more large apertures are
observed, which transmit to the central parts of the bone vessels corresponding to
the nutrient arteries and veins. The veins emerge from the long bones in three
places (KoUiker): (1) one or two large veins accompany the artery; (2) numerous
large and small veins emerge at the articular extremities; (3) many small veins
pass out of the compact substance. In the flat cranial bones the veins are large,
very numerous, and run in tortuous canals in the diploic tissue, the sides of the
canals being formed by thin lamellae of bone, perforated here and there for the
passage of branches from the adjacent cancelli. The same condition is also
found in all cancellous tissue, the veins being enclosed and supported by osseous
material, and having exceedingly thin coats. When a bone is divided, the vessels
remain patulous, and do not contract in the canals in which they are contained.
Lymphatic vessels, in addition to those found in the periosteum, have been traced
by Cruikshank into the substance of bone, and Klein describes them as running in
the Haversian canals. Nerves are distributed freely to the periosteum, and accom-
pany the nutrient arteries into the interior of the bone. They are said by Kolliker
to be most numerous in the articular extremities of the long bones, in the vertebrae,
and in the larger flat bones.
Fig. 73. — Transverse section of compact tissue bone. Magnified. (Sharpey.)
Minute Anatomy. — A transverse section of dense bone may be cut with a saw
and ground down until it is sufficiently thin.
If this be examined with a rather low power the bone will be seen to be mapped
out into a number of circular districts each consisting of a central hole surrounded
by a number of concentric rings. These districts are termed Haversian systems;
the central hole is an Haversian canal, and the rings are layers of bony tissue
arranged concentrically around the central canal, and termed lamellae. More-
over, on closer examination it will be found that between these lamellae, and
therefore also arranged concentrically around the central canal, are a number of
little dark spots, the lacunae, and that these lacunae are connected with each other
and with the central Haversian canal by a number of fine dark lines, which radiate
like the spokes of a wheel and are called canalicuU. Filling in the irregular intervals
which are left between these circular systems are other lamellae, with their lacunae
and canaliculi running in various directions, but more or less curved (Fig. 73);
they are termed interstitial lamellae. Again, other lamellae, found on the surface
of the bone, are arranged parallel to its circumference; they are termed circum-
90
OSTEOLOGY
ferential, or by some authors primary or fundamental lamellae, to distinguish them
from those laid down around the axes of the Haversian canals, which are then
termed secondary or special lamellae.
The Haversian canals, seen in a transverse section of bone as round holes at or
about the center of each Haversian system, may be demonstrated to be true canals
if a longitudinal section be made (Fig. 74). It will then be seen that the canals
run parallel with the longitudinal axis of the bone for a short distance and then
branch and communicate. They vary considerably in size, some being as much as
0.12 mm. in diameter; the average size is, however, about 0.05 mm. Near the
medullary cavity the canals are larger than those near the surface of the bone.
Each canal contains one or two bloodvessels, with a small quantity of delicate
connective tissue and some nerve filaments. In the larger ones there are also
lymphatic vessels, and cells with branching processes which communicate, through
the canalculi, with the branched processes of certain bone cells in the substance
of the bone. Those canals near the surface of the bone open upon it by minute
orifices, and those near the medullary cavity open in the same way into this space,
so that the whole of the bone is permeated by a system of bloodvessels running
through the bony canals in the centers of the Haversian systems.
The lamellae are thin plates of bony tissue
encircling the central canal, and may be com-
pared, for the sake of illustration, to a number
of sheets of paper pasted one over another
around a central hollow cylinder. After
macerating a piece of bone in dilute mineral
acid, these lamellae may be stripped off in a
Via. 74. — Section parallel to the surface
from the body of the femur. X 100. a. Haver-
sian canals; 6, lacunse seen from the side; c,
others seen from the surface in lamellse, which
are cut horizontally.
Fio. 75. — Perforating fibers, human parietal bone, decalcified.
(H. Miiller.) a, perforating fibers in situ; b, fibres drawn out of
their sockets; c, sockets.
longitudinal direction as thin films. If one of these be examined with a high power
of the microscope, it will be found to be composed of a finely reticular structure,
made up of very slender transparent fibers, decussating obliquely; and coalescing
at the points of intersection ; these fibers are composed of fine fibrils identical with
those of white connective tissue. The intercellular matrix between the fibers is
impregnated by calcareous deposit which the acid dissolves. In many places the
various lamellae may be seen to be held together by tapering fibers, which run
obliquely through them, pinning or bolting them together; they were first de-
scribed by Sharpey, and were named by him perforating fibers (Fig. 75).
The Lacunae are situated between the lamellse, and consist of a number of oblong
BONE 91
spaces. In an ordinary microscopic section, viewed by transmitted light, they
appear as fusiform opaque spots. Each lacuna is occupied during life by a branched
cell, termed a bone-cell or bone-corpuscle, the processes from which extend into the
canaliculi (Fig. 70).
The CanaUcuU are exceedingly minute channels, crossing the lamellae and con-
nectmg the lacunae with neighboring lacunae and also with the Haversian canal.
From the Haversian canal a number of canaliculi are given off, which radiate from
it, and open into the first set of lacunte between the first and second lamellae.
From these lacunae a second set of canaliculi is given off; these run outward to the
next series of lacunae, and so on until the periphery of the Haversian system is
reached; here the canaliculi given off from the last series of lacuna? do not communi-
cate with the lacunae of neighboring Haversian systems, but after passing outward
for a short distance form loops and return to their own lacunar. Thus every
part of an Haversian system is supplied with nutrient fluids derived from the
vessels in the Haversian canal and distributed
through the canaliculi and lacunae.
The bone cells are contained in the lacunae,
which, however, they do not completely fill.
They are flattened nucleated branched cells,
homologous with those of connective tissue; the
branches, especially in young bones, pass into
the canaliculi from the lacunae.
In thin plates of bone (as in the walls of
the spaces of cancellous tissue) the Haversian
canals are absent, and the canaliculi open into
the spaces of the cancellous tissue (medullary
spaces), which thus have the same function as
the Haversian canals. ^^°- 76.— Nucleated bone cells and their
_ _ . processes, contained in the bone lacuna and
Chemical Composition. Bone consists of an t^elr canalicull respectively. From a section
I I , ... through the vertebra of an adult mouse.
animal and an earthy part intimately com- (Kiein and Nobie smith.)
bined together.
The animal part may be obtained by immersing a bone for a considerable time
in dilute mineral acid, after which process the bone comes out exactly the same
shape as before, but perfectly flexible, so that a long bone (one of the ribs, for
example) can easily be tied in a knot. If now a transverse section is made
(Fig. 77) the same general arrangement of the Haversian canals, lamellae, lacunae,
and canaliculi is seen.
The earthy part may be separately obtained by calcination, by which the
animal matter is completely burnt out. The bone will still retain its original
form, but it will be white and brittle, will have lost about one-third of its original
weight, and will crumble down with the slightest force. The earthy matter is
composed chiefly of calcium phosphate, about 58 per cent, of the weight of the
bone, calcium carbonate about 7 per cent., calcium fluoride and magnesium phos-
phate from 1 to 2 per cent, each and sodium chloride less than 1 per cent. ; they confer
on bone its hardness and rigidity, while the animal matter {ossein) determines its
tenacity.
Ossification. — Some bones are preceded by membrane, such as those forming
the roof and sides of the skull; others, such as the bones of the limbs, are preceded
by rods of cartilage. Hence two kinds of ossification are described: the intra-
membranous and the intracartilaginous.
Intramembranous Ossification. — In the case of bones which are developed
in membrane, no cartilaginous mould precedes the appearance of the bony tissue.
The membrane which occupies the place of the future bone is of the nature of con-
nective tissue, and ultimately forms the periosteum; it is composed of fibers and
granular cells in a matrix. The peripheral portion is more fibrous, while, in the
92
OSTEOLOGY
interior the cells or osteoblasts predominate; the whole tissue is richly supplied with
bloodvessels. At the outset of the process of bone formation a little network
of spicules is noticed radiating from the point or center of ossification. These
rays consist at their growing points of a network of fine clear fibers and granular
Fig.
Haversian canal
Bone corpuscle Bone corpuscle
between inter-
stitial lainellm
'7. — Transverse section of body of human fibula, decalcified. X 250.
corpuscles with an intervening ground substance (Fig. 78). The fibers are termed
osteogenetic fibers, and are made up of fine fibrils diftering little from those of white
fibrous tissue. The membrane soon assumes a dark and granular appearance from
the deposition of calcareous granules in the fibers and in the intervening matrix,
Union of
adjacent ~"
spicules
Osteoblasts'.
Osteogenetic
fibers
Calcified deposit
~ ~ between the fibers
Bony spicules
Fig. 78. — Part of the growing edge of the developing parietal bone of a fetal cat. (After J. Lawrence.)
and in the calcified material some of the granular corpuscles or osteoblasts are
enclosed. By the fusion of the calcareous granules the tissue again assumes a
more transparent appearance, but the fibers are no longer so distinctly seen.
The involved osteoblasts form the corpuscles of the future bone, the spaces in
BONE
93
9, '
^^^
which they are enclosed constituting the lacunae. As the osteogenetic fibers grow
out to the periphery they continue to calcify, and give rise to fresh bone spicules.
Thus a network of bone is formed, the meshes of which contain the bloodvessels
and a delicate connective tissue crowded with osteoblasts. The bony trabeculae
thicken by the addition of fresh layers of bone formed by the osteoblasts on their
surface, and the meshes are correspondingly encroached upon. Subsequently
successive layers of bony tissue are deposited under the periosteum and around
the larger vascular channels which become the Haversian canals, so that the bone
increases much in thickness.
Intercartilaginous Ossification. — Just before ossification begins the mass is
entirely cartilaginous, and in a long bone, which may be taken as an example, the
process commences in the center and proceeds toward the extremities, which for
some time remain cartilaginous. Subsequently a similar process commences in
one or more places in those extremities and gradually extends through them.
The extremities do not, however, become joined to the body of the bone by bony
tissue until growth has ceased; between the body and either extremity a layer of
cartilaginous tissue termed the epiphysial cartilage persists for a definite period.
The first step in the ossification of
the cartilage is that the cartilage cells,
at the point where ossification is com-
mencing and which is termed a center
of ossification, enlarge and arrange
themselves in rows (Fig. 79). The
matrix in which they are imbedded
increases in quantity, so that the cells
become further separated from each
other. A deposit of calcareous material
now takes place in this matrix, between
the rows of cells, so that thev become
separated from each other by longi-
tudinal columns of calcified matrix,
presenting a granular and opaque ap-
pearance. Here and there the matrix
between two cells of the same row also
becomes calcified, and transverse bars
of calcified substance stretch across
from one calcareous column to another.
Thus there are longitudinal groups of
the cartilage cells enclosed in oblong
cavities, the walls of which are formed
of calcified matrix which cuts off all
nutrition from the cells; the cells, in
consequence, atrophy, leaving spaces
called the primary areolae.
At the same time that this process
is going on in the center of the solid
bar of cartilage, certain changes are
taking place on its surface. This is
covered by a very vascular membrane,
the perichondrium, entirely similar to the
embryonic connective tissue already
described as constituting the basis of
membrane bone; on the inner surface of this — that is to say, on the surface in
contact with the cartilage — are gathered the formative cells, the osteoblasts. By
the agency of these cells a thin layer of bony tissue is formed between the peri-
FiG. 79. — Section of fetal bone of cat. ir. Irruption
of the subperiosteal tissue, p. Fibrous layer of the perios-
teum. 0. Layer of osteoblasts, im. Subperiosteal bony
deposit. (From Quain's "Anatomy," E. A. Schafer.)
94
OSTEOLOGY
chondrium and the cartilage, by the intramemhranous mode of ossification just
described. There are then, in this first stage of ossification, two processes going
on simultaneously: in the center of the cartilage the formation of a number of
oblong spaces, formed of calcified matrix and containing the withered cartilage
cells, and on the surface of the cartilage the formation of a layer of true mem-
brane bone. The second stage consists in the prolongation into the cartilage of
processes of the deeper or osteogenetic layer of the perichondrium, which has
now become periosteum (Fig. 79, ir). The processes consist of bloodvessels and
cells — osteoblasts, or bone-formers, and osteoclasts, or bone-destroyers. The latter
are similar to the giant cells (myeloplaxes) found in marrow, and they excavate
passages through the new-formed bony layer by absorption, and pass through
it into the calcified matrix (Fig. 80). Wherever these processes come in con-
tact with the calcified walls of the primary areolae they absorb them, and thus
cause a fusion of the original cavities and the formation of larger spaces, which
are termed the secondary areolae or medullary spaces. These secondary spaces
become filled with embryonic marrow, consisting of osteoblasts and vessels, derived,
in the manner described above, from the
osteogenetic layer of the periosteum (Fig. 80).
Thus far there has been traced the forma-
tion of enlarged spaces (secondary areolae),
the perforated walls of which are still formed
by calcified cartilage matrix, containing an
embryonic marrow derived from the processes
sent in from the osteogenetic layer of the
periosteum, and consisting of bloodvessels and
osteoblasts. The walls of these secondary
areolae are at this time of only inconsiderable
thickness, but they become thickened by the
deposition of layers of true bone on their sur-
face. This process takes place in the follow-
ing manner: Some of the osteoblasts of the
embryonic marrow, after undergoing rapid
division, arrange themselves as an epithelioid
layer on the surface of the wall of the space
(P'ig. 81). This layer of osteoblasts forms a
bony stratum, and thus the wall of the space
becomes gradually covered with a layer of
Osteoclasts- '^^
Fig. 80. — Part of a longitudinal section of
the developing femur of a rabbit, a. Flattened
cartilage cells, b. Enlarged cartilage cells, c,
d. Newly formed bone. e. Osteoblasts. /.
Giant cells or osteoclasts. g, h. Shrunken
cartilage cells. (From ' 'Atlas of Histology, "
Klein and Noble Smith.)
Osteoblasts
fl'^f-f.>7 rdUKr:,
^^^^'^z^nx-rmm^p^^^^^
Fig. 81. — Osteoblasts and osteoclasts on trabecula of lower jaw of
calf embryo. (KoUiker.)
true osseous substance in which some of the bone-forming cells are included as
bone corpuscles. The next stage in the process consists in the removal of these
primary bone spicules by the osteoclasts. One of these giant cells may be found
lying in a Howship's foveola at the free end of each spicule. The removal of the
BONE 95
primary spicules goes on jpari passu with the formation of permanent bone by
the periosteum, and in this way the medullary cavity of the body of the bone is
formed.
This series of changes has been gradually proceeding toward the end of the body
of the bone, so that in the ossifying bone all the changes described above may
be seen in different parts, from the true bone at the center of the body to the hyaline
cartilage at the extremities.
While the ossification of the cartilaginous body is extending toward the articular
ends, the cartilage immediately in advance of the osseous tissue continues to grow
until the length of the adult bone is reached.
During the period of growth the articular end, or epiphysis, remains for some
time entirely cartilaginous, then a bony center appears, and initiates in it the
process of intracartilaginous ossification; but this process never extends to any
great distance. The epiphysis remains separated from the body by a narrow
cartilaginous layer for a definite time. This layer ultimately ossifies, the distinc-
tion between body and epiphysis is obliterated, and the bone assumes its completed
form and shape. The same remarks also apply to such processes of bone as are
separately ossified, e. g., the trochanters of the femur. The bones therefore con-
tinue to grow until the body has acquired its full stature. They increase in length
by ossification continuing to extend behind the epiphysial cartilage, which goes
on growing in advance of the ossifying process. They increase in circumference
by deposition of new bone, from the deeper layer of the periosteum, on their exter-
nal surface, and at the same time an absorption takes place from within, by which
the medullary cavities are increased.
The permanent bone formed by the periosteum when first laid down is cancellous
in structure. Later the osteoblasts contained in its spaces become arranged in
the concentric layers characteristic of the Haversian systems, and are included
as bone corpuscles.
The number of ossific centers ^•a^ies in different bones. In most of the short
bones ossification commences at a single point near the center, and proceeds toward
the surface. In the long bones there is a central point of ossification for the body
or diaph}'sis: and one or more for each extremity, the epiphysis. That for the
body is the first to appear. The times of union of the epiphyses with the body
vary inversely with the dates at which their ossifications began (with the exception
of the fibula) and regulate the direction of the nutrient arteries of the bones. Thus,
the nutrient arteries of the bones of the arm and forearm are directed toward
the elbow, since the epiphyses at this joint become united to the bodies before
those at the opposite extremities. In the lower limb, on the other hand, the
nutrient arteries are directed away from the knee: that is, upward in the femur,
downward in the tibia and fibula; and in them it is observed that the upper epiphysis
of the femur, and the lower epiphyses of the tibia and fibula, unite first with the
bodies. Where there is only one epiphysis, the nutrient artery is directed toward
the other end of the bone; as toward the acromial end of the clavicle, toward the
distal ends of the metacarpal bone of the thumb and the metatarsal bone of the
great toe, and toward the proximal ends of the other metacarpal and metatarsal
bones.
Parsons^ groups epiphyses under three headings, viz.: (1) pressure epiphyses,
appearing at the articular ends of the bones and transmitting "the weight of the
body from bone to bone;" (2) traction epiphyses, associated with the insertion
of muscles and "originally sesamoid structures though not necessarily sesamoid
bones;" and (3) atavistic epiphyses, representing parts of the skeleton, which at
one time formed separate bones, but which have lost their function, "and only
appear as separate ossifications in early life."
' Jour, of Anat. and Phys., vols, zxxviii, xsxix, and xlii.
96
OSTEOLOGY
THE VERTEBRAL COLUMN (COLUMNA VERTEBRALIS ; SPINAL
COLUMN).
The vertebral column is a flexuous and flexible column, formed of a series oi
bones called vertebrae.
The vertebrae are thirty-three in number, and are grouped under the names
cervical, thoracic, lumbar, sacral, and coccygeal, according to the regions they
occupy; there are seven in the cervical region, twelve in the thoracic, five in the
lumbar, five in the sacral, and four in the coccygeal.
This number is sometimes increased by an additional vertebra in one region,
or it may be diminished in one region, the deficiency often being supplied by an
additional vertebra in another. The number of cervical vertebra is, however,
very rarely increased or diminished.
The vertebrae in the upper three regions of the column remain distinct through-
out life, and are known as true or movable vertebrae; those of the sacral and
coccygeal regions, on the other hand, are termed false or fixed vertebrae, because
they are united with one another in the adult to form two bones — fi^'e forming
the upper bone or sacrum, and four the terminal bone or coccyx.
With the exception of the first and second cervical, the true or movable vertebrae
present certain common characteristics which are best studied by examining one
from the middle of the thoracic region.
GENERAL CHARACTERISTICS OF A VERTEBRA.
A typical vertebra consists of two essential parts — viz., an anterior segment, the
body, and a posterior part, the vertebral or neural arch; these enclose a foramen,
the vertebral foramen. The vertebral arch consists of a pair of pedicles and a pair
of laminae, and supports seven processes — viz., four articular, two transverse, and
one spinous.
Costal fovea ■ S
Pedicle or roo' of
vertebral arch
Lami
ina
II
ISuperwr articular process
Fig. 82. — A typical thoracic vertebra, viewed from above.
^Mien the vertebrae are articulated with each other the bodies form a strong
pillar for the support of the head and trunk, and the vertebral foramina constitute
a canal for the protection of the medulla spinalis (spinal cord), while between
every pair of vertebrae are two apertures, the intervertebral foramina, one on
either side, for the transmission of the spinal nerves and vessels.
Body {corpus rertebrcp). — The body is the largest part of a vertebra, and is
more or less cylindrical in shape. Its upper and lower surfaces are flattened and
THE CERVICAL VERTEBRJE
97
rough, and give attachment to the intervertebral fibrocartilages, and each presents
a rim around its circumference. In front, the body is convex from side to side
and concave from above downward . Behind, it is flat from above downward
and slightly concave from side to side. Its anterior surface presents a few small
apertures, for the passage of nutrient vessels; on the posterior surface is a single
large, irregular aperture, or occasionally more than one, for the exit of the basi-
vertebral veins from the body of the vertebra.
Pedicles {radices orci vertebrce). — The pedicles are two short, thick processes,
which project backward, one on either side, from the upper part of the body,
at the junction of its posterior and lateral surfaces. The concavities above and
below the pedicles are named the vertebral notches; and when the vertebrae are
articulated, the notches of each contiguous pair of bones form the intervertebral
foramina, already referred to.
Laminae. — The laminae are two broad plates directed backward and medialward
from the pedicles. They fuse in the middle line posteriorly, and so complete the
posterior boundary of the vertebral foramen. Their upper borders and the lower
parts of their anterior surfaces are rough for the attachment of the ligamenta
flava.
Processes. — Spinous Process (processus spinosus). — The spinous process is
directed backward and downward from the junction of the laminae, and serves
for the attachment of muscles and ligaments.
Articular Processes. — ^The articular processes, two superior and two inferior,
spring from the junctions of the pedicles and laminae. The superior project
upward, and their articular surfaces are directed more or less backward; the
inferior project do\\'nward, and their surfaces look more or less forward. The
articular surfaces are coated with hyaline cartilage.
Transverse Processes (processus transversi). — The transverse processes, two in
number, project one at either side from the point where the lamina joins the
pedicle, between the superior and inferior articular processes. They serve for
the attachment of muscles and ligaments.
Structure of a Vertebra (Fig. S3). — The body is composed of cancellous tissue, covered by
a thin coating of compact bone; the latter is perforated by numerous orifices, some of large size
for the passage of vessels; the interior of the bone is traversed by one or two large canals, for the
reception of veins, which converge toward a single large, irregular aperture, or several small
apertures, at the posterior part of the
body. The thin bony lamellae of the
cancellous tissue are more pronounced
in hnes perpendicular to the upper
and lower surfaces and are developed
in response to greater pressure ni this
direction (Fig. S3). The arch and
processes projecting from it have
thick coverings of compact tissue.
The Cervical Vertebrae (Verte-
brae Cervicales).
The cervical vertebrae (Fig.
84) are the smallest of the true
vertebrae, and can be readily
distinguished from those of the thoracic or lumbar regions by the presence of a
foramen in each transverse process. The first, second, and seventh present excep-
tional features and must be separately described; the following characteristics are
common to the remaining four.
The body is small, and broader from side to side than from before backward
The anterior and posterior surfaces are flattened and of equal depth; the former
Fig. 83. — Sagittal section of a lumbar vertebra.
98
OSTEOLOGY
is placed on a lower level than the latter, and its inferior border is prolonged
downward, so as to overlap the upper and forepart of the vertebra below. The
upper surface is concave transversely, and presents a projecting lip on either side;
the lower surface is concave from before backward, convex from side to side, and
presents laterally shallow concavities which receive the corresponding projecting
lips of the subjacent vertebra. The pedicles are directed lateralward and backward,
and are attached to the body midway between its upper and lower borders, so that
the superior vertebral notch is as deep as the inferior, but it is, at the same time,
Anterior tubercle of
transverse 'process
Foramen
iransversarium
Posterior tubercle of—'
transverse process
inotis
process
Fig. 84. — A cerv-ical vertebra.
Transverse process
Superior articular
process
Inferior articular
process
narrower. The laminae are narrow, and thinner above than below; the vertebral
foramen is large, and of a triangular form. The spinous process is short and bifid,
the two divisions being often of unequal size. The superior and inferior articular
processes on either side are fused to form an articular pillar, which projects lateral-
ward from the junction of the pedicle and lamina. The articular facets are flat
and of an o^'al form: the superior look backward, upward, and slightly medial-
ward: the inferior forward, downward, and slightly lateralward. The transverse
processes are each pierced by the foramen transversarimn, which, in the upper six
Body /C
Anterior tubercle of ^
transverse process
Sulcus for nerve
Superior articular surface
Articular pillar
Fig.
Posterior tubercle of
transverse process
85. — Side view of a typical cervical vertebra.
Spinalis process
vertebrae, gives passage to the vertebral artery and vein and a plexus of sympa-.
thetic nerves. Each process consists of an anterior and a posterior part. The
anterior portion is the homologue of the rib in the thoracic region, and is there-
fore named the costal process or costal element: it arises from the side of the bod}'',
is directed lateralward in front of the foramen, and ends in a tubercle, the anterior
tubercle. The posterior part, the true transverse process, springs from the
vertebral arch behind the foramen, and is directed forward and lateralward; it
ends in a flattened vertical tubercle, the posterior tubercle. These two parts
THE CERVICAL VERTEBRM
99
are joined, outside the foramen, by a bar of bone which exhibits a deep sulcus
on its upper surface for the passage of the corresponding spinal nerve. ^
First Cervical Vertebra.— The first cervical vertebra (Fig. 86) is named the
atlas because it supports the globe of the head. Its chief peculiarity is that it has
no body, and this is due to the fact that the body of the atlas has fused with that
of the next vertebra. Its other peculiarities are that it has no spinous process,
is ring-like, and consists of an anterior and a posterior arch and two lateral masses.
The anterior arch forms about one-fifth of the ring: its anterior surface is convex,
and presents at its center the anterior tubercle for the attachment of the Longus
colli muscles; posteriorly it is concave, and marked by a smooth, oval or circular
facet {fovea dentis), for articulation with the odontoid process {dens) of the axis.
The upper and lower borders respectively give attachment to the anterior atlanto-
occipital membrane and the anterior atlantoaxial ligament; the former connects
it with the occipital bone above, and the latter with the axis below. The posterior
arch forms about two-fifths of the circumference of the ring: it ends behind in the
posterior tubercle, which is the rudiment of a spinous process and gives origin to
the Recti capitis posteriores minores. The diminutive size of this process pre-
vents any interference with the movements between the atlas and the skull.
The posterior part of the arch presents above and behind a rounded edge for
Anterior tvhercle
Tratisverse
process
Oxiline of section of odontoid
process
Outline of section of trans-
verse atlanfal ligament
Foramen
trayisver-
sarium
Groove for vtrichral artery
and first cervical nerve
Posterior tubercle
Fig. 86. — First cer%acal vertebra, or atlas.
the attachment of the posterior atlantooccipital membrane, while immediately
behind each superior articular process is a groove {sidcus arterioe vertebralis) ,
sometimes converted into a foramen by a delicate bony spiculum which arches
backward from the posterior end of the superior articular process. This groove
represents the superior vertebral notch, and serves for the transmission of the
vertebral artery, which, after ascending through the foramen in the transverse
process, winds around the lateral mass in a direction backward and medialward; it
also transmits the suboccipital (first spinal) nerve. On the under surface of the
posterior arch, behind the articular facets, are two shallow grooves, the inferior
vertebral notches. The lower border gives attachment to the posterior atlanto-
axial ligament, which connects it with the axis. The lateral masses are the most
bulky and solid parts of the atlas, in order to support the weight of the head.
Each carries two articular facets, a superior and an inferior. The superior facets
are of large size, oval, concave, and approach each other in front, but diverge
behind: they are directed upward, medialward, and a little backward, each forming
a cup for the corresponding condyle of the occipital bone, and are admirably
adapted to the nodding movements of the head. Not infrequently they are
' The costal element of a cervical vertebra not only includes the portion which springs from the side of the body, but
the anterior and posterior tubercles and the bar of bone which connects them (Fig. 67).
100
OSTEOLOGY
partially subdivided by indentations which encroach upon their margins. The
inferior articular facets are circular in form, flattened or slightly convex and directed
downward and medialward, articulating with the axis, and permitting the rotatory
movements of the head. Just below the medial margin of each superior facet is
a small tubercle, for the attachment of the transverse atlantal ligament which
stretches across the ring of the atlas and divides the vertebral foramen into two
unequal parts — the anterior or smaller receiving the odontoid process of the axis,
the posterior transmitting the medulla spinalis and its membranes. This part
of the vertebral canal is of considerable size, much greater than is required for the
accommodation of the medulla spinalis, and hence lateral displacement of the
atlas may occur without compression of this structure. The transverse processes
are large; they project lateralward and downward from the lateral masses, and
serve for the attachment of muscles which assist in rotating the head. Thev
are long, and their anterior and posterior tubercles are fused into one mass; the
foramen transversarium is directed from below, upward and backu^ard.
Dens
For alar ligaments
For trans, ligament of alias
Superior articular
surface
Foramen
transversarium
Spinous process
Fig. 87. — Second cervical vertebra, or epistropheus, from above.
Second Cervical Vertebra. — The second cervical vertebra (Fig. S7 and SS) is named
the epistropheus or axis because it forms the pivot upon which the first vertebra,
carrying the head, rotates. The most distinctive characteristic of this bone is
the strong odontoid process which rises perpendicularly from the upper surface
of the body. The body is deeper in front than behind, and prolonged downward
anteriorly so as to overlap the upper and fore part of the third vertebra. It pre-
sents in front a median longitudinal ridge, separating two lateral depressions for
the attachment of the Longus colli muscles. Its under surface is concave from
before backward and covex from side to side. The dens or odontoid process exhibits
a slight constriction or neck, where it joins the body. On its anterior surface
is an oval or nearly circular facet for articulation with that on the anterior arch
of the atlas. On the back of the neck, and frequenth* extending on to its lateral
surfaces, is a shallow groove for the transverse atlantal ligament which retains
the process in position. The apex is pomted, and gi^•es attaclmient to the apical
odontoid ligament; below the apex the process is somewhat enlarged, and pre-
sents on either side a rough impression for the attaclmient of the alar ligament;
these ligaments connect the process to the occipital bone. The internal structure
THE CERVICAL VERTEBRA
101
of the odontoid process is more compact than that of the body. The pedicles
are broad and strong, espe^cially in front, where they coalesce with the sides of
the body and the root of the odontoid process. They are covered above by the
superior articular surfaces. The laminae are thick and strong, and the vertebral
Odontoid process
Rough surface for alar ligament
Groove for transverse atlanial ligament
Spinous process-^
Articular facet for
anterior arch of atlas
Body
Transverse process
Inferior articular process
Fig. 88. — Second cervical vertebra, epistropheus, or axis, from the side.
Transverse
process
foramen large, but smaller than that of the atlas. The transverse processes are
very small, and each ends in a single tubercle; each is perforated by the foramen
transversarium, which is directed obliquely upward and lateralward. The superior
articular surfaces are round, slightly convex, directed upward and lateralward,
and are supported on the body,
pedicles, and transverse processes. ^"'^'^
The inferior articular surfaces have
the same direction as those of the
other cervical vertebrae. The supe-
rior vertebral notches are very shal-
low, and lie behind the articular
processes; the inferior lie in front
of the articular processes, as in the
other cervical vertebrae. The spinous
process is large, very strong, deeply
channelled on its under surface,
and presents a bifid, tuberculated
extremity.
The Seventh Cervical Vertebra
(Fig. 89). — The most distinctive
characteristic of this vertebra is
the existence of a long and promi-
nent spinous process, hence the
name vertebra prominens. This pro-
cess is thick, nearly horizontal in
direction, not bifurcated, but ter-
minating in a tubercle to which the lower end of the ligamentum nuchse is
attached. The transverse processes are of considerable size, their posterior roots
are large and prominent, while the anterior are small and faintly marked; the
upper surface of each has usually a shallow sulcus for the eighth spinal nerve,
and its extremity seldom presents more than a trace of bifurcation. The foramen
Spinous process
Fia. 89. — Seventh cervical vertebra.
102
OSTEOLOGY
transversarium may be as large as that in the other cervical vertebrae, but is
generally smaller on one or both sides; occasionally it is double, sometimes it is
absent. On the left side it occasionally gives passage to the vertebral artery;
more frequently the vertebral vein traverses it on both sides; but the usual
arrangement is for both artery and vein to pass in front of the transverse pro-
cess, and not through the foramen. wSometimes the anterior root of the trans-
verse process attains a large size and exists as a separate bone, which is known
as a cervical rib.
The Thoracic Vertebrae (Vertebrae Thoracales).
The thoracic vertebrae (Fig. 90) are intermediate in size between those of
the cervical and lumbar regions; they increase in size from above downward, the
upper vertebrae being much smaller than those in the lower part of the region.
They are distinguished by the presence of facets on the sides of the bodies for
articulation with the heads of the ribs, and facets on the transverse processes of
all, except the eleventh and twelfth, for articulation with the tubercles of the ribs.
Superior articular process
Demi-facet for head of rib
Facet for articular part
of tubercle of rib
Demi-facet for head of rib
Inferior articular process
Fig. 90. — A thoracic vertebra.
The bodies in the middle of the thoracic region are heart-shaped, and as broad
in the antero-posterior as in the transverse direction. At the ends of the thoracic
region they resemble respectively those of the cervical and lumbar vertebrae.
They are slightly thicker behind than in front, fiat above and below, convex from
.side to side in front, deeply concave behind, and slightly constricted laterally
and in front. They present, on either side, two costal demi-facets, one above,
near the root of the pedicle, the other below, in front of the inferior vertebral
notch; these are covered with cartilage in the fresh state, and, when the vertebrae
are articulated with one another, form, with the intervening intervertebral fibro-
cartilages, oval surfaces for the reception of the heads of the ribs. The pedicles
are directed backward and slightly upward, and the inferior vertebral notches
are of large size, and deeper than in any other region of the vertebral column.
The laminae are broad, thick, and imbricated — that is to say, they overlap those
of subjacent vertebrae like tiles on a roof. The vertebral foramen is small, and of
a circular form. The spinous process is long, triangular on coronal section, directed
obliquely downward, and ends in a tuberculated extremity. These processes
THE THORACIC VERTEBRA
103
overlap from the fifth to the eighth, but are less oblique in direction above and
below. The superior articular processes are thin plates of bone projecting upward
from the junctions of the pedicles and lamina; their articular facets are practi-
cally flat, and are directed backward and a little lateralward and upward. The
inferior articular processes are fused to a considerable extent with the laminse,
An entire facet above;
a datii-facet below
demi-facet above
— One entire facet
One entire facet.
No facet on trans, proc.
which is rudimentary
One entire facet.
No facet on trans-
verse process.
Infer. artic.process
convex and turned
lateralwards
Fio. 91. — Peculiar thoracic vertebrse.
and project but slightly beyond their lower borders; their facets are directed
forward and a little medialward and downward. The transverse processes arise
from the arch behind the superior articular processes and pedicles; they are thick,
strong, and of considerable length, directed obliquely backward and lateralward,
and each ends in a clubbed extremity, on the front of which is a small, concave
surface, for articulation with the tubercle of a rib.
104
OSTEOLOGY
The first, ninth, tenth, eleventh, and twelfth thoracic vertebrae present certain
pecuHarities, and must be specially considered (Fig. 91).
The First Thoracic Vertebra has, on either side of the body, an entire articular
facet for the head of the first rib, and a demi-facet for the upper half of the head
of the second rib. The body is like that of a cervical vertebra, being broad trans-
versely; its upper surface is concave, and lipped on either side. The superior
articular surfaces are directed upward and backward; the spinous process is thick,
long, and almost horizontal. The transverse processes are long, and the upper
vertebral notches are deeper than those of the other thoracic vertebrae.
The Ninth Thoracic Vertebra may have no demi-facets below. In some sub-
jects however, it has two demi-facets on either side; when this occurs the tenth
has only demi-facets at the upper part.
The Tenth Thoracic Vertebra has (except in the cases just mentioned) an entire
articular facet on either side, which is placed partly on the lateral surface of the
pedicle.
In the Eleventh Thoracic Vertebra the body approaches in its form and size
to that of the lumbar vertebrae. The articular facets for the heads of the ribs
are of large size, and placed chiefly on the pedicles, which are thicker and stronger
in this and the next vertebra than in any other part of the thoracic region. The
spinous process is short, and nearly horizontal in direction. The transverse processes
are very short, tuberculated at their extremities, and have on articular facets.
The Twelfth Thoracic Vertebra has the same general characteristics as the
eleventh, but may be distinguished from it by its inferior articular surfaces being
convex and directed lateralward, like those of the lumbar vertebrae; by the general
form of the body, laminae, and spinous process, in which it resembles the lumbar
vertebrae; and by each transverse process being subdivided into three elevations,
the superior, inferior, and lateral tubercles: the superior and inferior correspond
to the mammillary and accessory processes of the lumbar vertebrae. Traces of
similar elevations are found on the transverse processes of the tenth and eleventh
thoracic vertebrae.
Superior articvlar process
Fig. 92. — A lumbar vertebra seen from the side.
The Lumbar Vertebrae (Vertebrae Lumbales).
The lumbar vertebrae (Figs. 92 and 93) are the largest segments of the movable
part of the vertebral column, and can be distinguished by the absence of a
foramen in the transverse process, and by the absence of facets on the sides of
the body.
The body is large, wider from side to side than from before backward, and a
little thicker in front than behind. It is flattened or slightly concave above and
THE LUMBAR VERTEBRA
105
below, concave behind, and deeply constricted in front and at the sides. The
pedicles are very strong, directed backward from the upper part of the body;
Transverse process
Inferior articular
process
Superior articular
process
Mamillary process
Accessory process
FiQ. 93. — A lumbar vertebra from above and behind.
consequently, the inferior vertebral notches are of considerable depth. The
laminae are broad, short, and strong; the vertebral foramen is triangular, larger
Fig. 94. — Fifth lumbar vertebra, from above.
than in the thoracic, but smaller than in the cervical region. The spinous process
is thick, broad, and somewhat quadrilateral; it projects backward and ends in
106 OSTEOLOGY
a rough, uneven border, thickest below where it is occasionally notched. The
superior and inferior articular processes are well-defined, projecting respectively
upward and downward from the junctions of pedicles and laminae. The facets
on the superior processes are concave, and look backward and medialward; those
on the inferior are convex, and are directed forward and lateralward. The former
are wider apart than the latter, since in the articulated column the inferior articular
processes are embraced by the superior processes of the subjacent vertebra. The
transverse processes are long, slender, and horizontal in the upper three lumbar
vertebrae; they incline a little upward in the lower two. In the upper three verte-
brae they arise from the junctions of the pedicles and laminae, but in the lower
two they are set farther forward and spring from the pedicles and posterior parts
of the bodies. They are situated in front of the articular processes instead of behind
them as in the thoracic vertebrae, and are homologous with the ribs. Of the three
tubercles noticed in connection with the transverse processes of the lower thoracic
vertebrae, the superior one is connected in the lumbar region with the back part
of the superior articular process, and is named the mammillary process; the inferior
is situated at the back part of the base of the transverse process, and is called the
accessory process (Fig. 93).
The Fifth Lumbar Vertebra (Fig. 94) is characterized by its body being much
deeper in front than behind, which accords with the prominence of the sacro-
vertebral articulation ; by the smaller size of its spinous process ; by the wide interval
between the inferior articular processes; and by the thickness of its transverse
processes, which spring from the body as well as from the pedicles.
The Sacral and Coccygeal Vertebrae.
The sacral and coccygeal vertebrae consist at an early period of life of nine
separate segments which are united in the adult, so as to form two bones, five
entering into the formation of the sacrum, four into that of the coccyx. Some-
times the coccjTC consists of five bones; occasionally the number is reduced to
three.
The Sacrum {os sacrum). — The sacrum is a large, triangular bone, situated
in the lower part of the vertebral column and at the upper and back part of the
pelvic cavity, where it is inserted like a wedge between the two hip bones; its
upper part or base articulates with the last lumbar vertebra, its apex with the
coccyx. It is curved upon itself and placed very obliquely, its base projecting
forward and forming the prominent sacrovertebral angle when articulated with
the last lumbar vertebra; its central part is projected backward, so as to give
increased capacity to the pelvic cavity.
Pelvic Surface (fades ijclvina). — The pelvic surface (Fig. 95) is concave from
above downward, and sHghtly so from side to side. Its middle part is crossed
by four transverse ridges, the positions of which correspond with the original
planes of separation between the five segments of the bone. The portions of bone
intervening between the ridges are the bodies of the sacral vertebrae. The body
of the first segment is of large size, and in form resembles that of a lumbar vertebra;
the succeeding ones diminish from above downward, are flattened from before
backward, and curved so as to accommodate themselves to the form of the sacrum,
being concave in front, convex behind. At the ends of the ridges are seen the
anterior sacral foramina, four in number on either side, somewhat rounded in form,
diminishing in size from above downward, and directed lateralward and forward;
they give exit to the anterior divisions of the sacral nerves and entrance to the
lateral sacral arteries. Lateral to these foramina are the lateral parts of the sacrum,
each consisting of five separate segments at an early period of life; in the adult,
these are blended with the bodies and with each other. Each lateral part is tra-
THE SACRAL AND COCCYGEAL VERTEBRA
107
versed by four broad, shallow grooves, which lodge the anterior divisions of the
sacral nerves, and are separated by prominent ridges of bone which give origin
to the Piriformis muscle.
If a sagittal section be made through the center of the sacrum (Pig. 99), the
bodies are seen to be united at their circumferences by bone, wide intervals being
left centrally, which, in the fresh state, are filled by the intervertebral fibro-
cartilages. In some bones this union is more complete between the lower than
the upper segments.
Dorsal Surface (fades dorsalis) .—The dorsal surface (Fig. 9G) is convex and
narrower than the pelvic. In the middle line it displays a crest, the middle sacral
crest, surmounted by three or four tubercles, the rudimentary spinous processes
Promontory
\ I
Fig. 95. — Sacrum, pelvic surface.
of the upper three or four sacral vertebrae. On either side of the middle sacral
crest is a shallow groove, the sacral groove, which gives origin to the iNIultifidus,
the floor of the groove being formed by the united laminae of the corresponding
vertebrae. The laminae of the fifth sacral vertebra, and sometimes those of the
fourth, fail to meet behind, and thus a hiatus or deficiency occurs in the posterior
wall of the sacral canal. On the lateral aspect of the sacral groove is a linear
series of tubercles produced by the fusion of the articular processes which together
form the indistinct sacral articular crests. The articular processes of the first
sacral vertebra are large and oval in shape; their facets are concave from side to
side, look backward and medialward, and articulate with the facets on the inferior
processes of the fifth lumbar vertebra. The tubercles which represent the inferior
articular processes of the fifth sacral vertebra are prolonged downward as rounded
108
OSTEOLOGY
processes, which are named the sacral comua, and are connected to the cornua
of the coccyx. Lateral to the articular processes are the four posterior sacral
foramina; they are smaller in size and less regular in form than the anterior, and
transmit the posterior divisions of the sacral nerves. On the lateral side of the
posterior sacral foramina is a series of tubercles, which represent the transverse
processes of the sacral vertebrae,, and form the lateral crests of the sacrum. The
transverse tubercles of the first sacral vertebra are large and very distinct; they,
together with the transverse tubercles of the second vertebra, give attacliment
to the horizontal parts of the posterior sacroiliac ligaments; those of the third
vertebra give attaclmient to the oblique fasciculi of the posterior sacroiliac liga-
ments; and those of the fourth and fifth to the sacrotuberous ligaments.
Sacrospinal
— Latissimus
dor si
Sacrospinalts
Upper half of fifth
rior sacral foramen
Fig. 96. — Sacrum, dorsal surface.
Lateral Surface. — The lateral surface is broad above, but narrowed into a thin
edge below. The upper half presents in front an ear-shaped surface, the auricular
surface, covered with cartilage in the fresh state, for articulation with the ilium.
Behind it is a rough surface, the sacral tuberosity, on which are three deep
and uneven impressions, for the attachment of the posterior sacroiliac ligament.
The lower half is thin, and ends in a projection called the inferior lateral angle;
medial to this angle is a notch, which is converted into a foramen by the trans-
verse process of the first piece of the cocc\'x, and transmits the anterior division of
the fifth sacral nerve. The thin lower half of the lateral surface gives attachment
to the sacrotuberous and sacrospinous ligaments, to some fibers of the Gluteeus
maximus behind, and to the Coccygeus in front.
Base Q)asis oss. sacri). — The base of the sacrum, which is broad and expanded,
is directed upward and forward. In the middle is a large oval articular surface,
THE SACRAL AND COCCYGEAL VERTEBRA
109
the upper surface of the body of the first sacral vertebra, which is connected with
the under surface of the body of the last lumbar vertebra by an intervertebral
Articular process
Medial sacral crest
Cornu of sacrum^
Cornu of coccyx
Fig. 97. — Lateral surfaces of sacrum and coccyx.
Sacral canal
Articular process
Fig. 98 — Base of sacrum.
no
OSTEOLOGY
fibrocartilage. Behind this is the large triangular orifice of the sacral canal, which
is completed by the laminse and spinous process of the first sacral vertebra. The
superior articular processes project from it on either side; they are oval, concave,
directed backward and medialward, like the superior articular processes of a lumbar
vertebra. They are attached to the body of the first sacral vertebra and to the
alse by short thick pedicles; on the upper surface of each pedicle is a vertebral
notch, which forms the lower part of the foramen between the last lumbar and first
sacral vertebrae. On either side of the body is a large triangular surface, which
supports the Psoas major and the lumbosacral trunk, and in the articulated
pelvis is continuous with the iliac fossa. This is called the ala; it is slightly concave
Cornua
Anterior Surface
Rudim.
Trans,
prac.
Posterior surface
FlQ. 99. — Median sagittal section of the sacrum.
Fig. 100.— Coccyx.
from side to side, convex from before backward, and gives attachment to a few
of the fibers of the Iliacus. The posterior fourth of the ala represents the trans-
verse process, and its anterior three-fourths the costal process of the first sacral
segment.
Apex (apex oss. sacri). — ^The apex is directed downward, and presents an oval
facet for articulation with the coccyx.
Vertebral Canal (canalis sacralis; sacral canal). — The vertebral canal (Fig. 99)
runs throughout the greater part of the bone; above, it is triangular in form;
below, its posterior wall is incomplete, from the non-development of the laminse
and spinous processes. It lodges the sacral nerves, and its walls are perforated by
the anterior and po-sterior sacral foramina through which these nerves pass out.
THE SACRAL AND COCCYGEAL VERTEBRA 111
Structure. — The sacrum consists of cancellous tissue enveloped by a thin layer of compact bone.
Articulations. — The sacrum articulates with four bones; the last lumbar vertebra above, the
coccyx below, and the hip bone on either side.
Differences in the Sacrum of the Male and Female. — In the female the sacrum is shorter and
wider than in the male; the lower half forms a greater angle with the upper; the upper half is
nearly straight, the lower half presenting the greatest amount of curvature. The bone is also
directed more obliquely backward; this increases the size of the pelvic cavity and renders the
sacrovertebral angle more prominent. In the male the curvature is more evenly distributed
over the whole length of the bone, and is altogether greater than in the female.
Variations. — The sacrum, in some cases, consists of six pieces; occasionally the number is
reduced to four. The bodies of the first and second vertebrae may fail to unite. Sometimes
the uppermost transverse tubercles are not joined to the rest of the ala on one or both sides,
or the sacral canal may be open throughout a considerable part of its length, in consequence of
the imperfect development of the laminae and spinous processes. The sacrum, also, varies con-
siderably with respect to its degree of curvature.
The Coccyx (os coccygis). — The coccyx (Fig. 100) is usually formed of four
rudimentary vertebrae; the number may however be increased to five or diminished
to three. In each of the first three segments may be traced a rudimentary body
and articular and transverse processes; the last piece (sometimes the third) is a
mere nodule of bone. All the segments are destitute of pedicles, laminae, and
spinous processes. The first is the largest; it resembles the lowest sacral vertebra,
and often exists as a separate piece; the last three diminish in size from above
downward, and are usually fused with one another.
Surfaces. — The anterior surface is slightly concave, and marked with three trans-
verse grooves which indicate the junctions of the different segments. It gives
attachment to the anterior sacrococcygeal ligament and the Levatores ani, and
supports part of the rectum. The posterior surface is convex, marked by transverse
grooves similar to those on the anterior surface, and preseiits on either side a linear
row of tubercles, the rudimentary articular processes of the coccygeal vertebrae.
Of these, the superior pair are large, and are called the coccygeal comua; they
project upward, and articulate with the cornua of the sacrum, and on either side
complete the foramen for the transmission of the posterior division of the fifth
sacral nerve.
Borders. — The lateral borders are thin, and exhibit a series of small eminences,
which represent the transverse processes of the coccygeal vertebrae. Of these,
the first is the largest; it is flattened from before backward, and often ascends
to join the lower part of the thin lateral edge of the sacrum, thus completing the
foramen for the transmission of the anterior division of the fifth sacral nerve;
the others diminish in size from above downward, and are often wanting. The
borders of the coccyx are narrow, and give attachment on either side to the sacro-
tuberous and sacrospinous ligaments, to the Coccygeus in front of the ligaments,
and to the Glutaeus maximus behind them.
Base. — The base presents an oval surface for articulation with the sacrum.
Apex. — The apex is rounded, and has attached to it the tendon of the Sphincter
ani externus. It may be bifid, and is sometimes deflected to one or other side.
Ossification of the Vertebral Colimm. — Each cartilaginous vertebra is ossified from three primary
centers (Fig. 101), two for the vertebral arch and one for the body.' Ossification of the vertebral
arches begins in the upper cervical vertebrae about the seventh or eighth week of fetal hfe, and grad-
ually extends down the column. The ossific granules first appear in the situations where the trans-
verse processes afterward project, and spread backward to the spinous process forward into the
pedicles, and lateralward into the transverse and articular processes. Ossification of thebodies begins
about the eighth week in the lower thoracic region, and subsequently extends upward and down-
ward along the column. The center for the body does not give rise to the whole of the body of
the adult vertebra, the postero-lateral portions of which are ossified by extensions from the verte-
bral arch centers. The body of the vertebra during the first few years of life shows, therefore,
■ A vertebra is occasionally found in which the body consists of two lateral portions — a condition which proves that
the body is sometimes ossified from two primary centers, one on either side of the middle line.
112
OSTEOLOGY
two sjTichondroses, neurocentral synchondroses, traversing it along the planes of junction of
the three centers (Fig. 102). In the thoracic region, the facets for the heads of the ribs lie behind
the neurocentral synchondroses and
Fig. 101. — Ossification of a vertebra
By 3 primary centers
1 for body (Slh week)
are ossified from the centers for the
vertebral arch. At birth the vertebra
consists of three pieces, the body and
the halves of the vertebral arch. Dur-
ing the first year the halves of the
arch unite behind, union taking place
first in the lumbar region and then
extending upward through the thoracic
and cervical regions. About the third
year the bodies of the upper cervical
vertebrae are joined to the arches on
either side; in the lower lumbar verte-
brae the union is not completed until the
sixth year. Before puberty, no other
Ijor each vertebral arch {lih or 8<A week)
Fig. 102.
By 3 secondary centers
Neurocentral
synchondrosis
1 for each
trans, process
\Qth year
1 for spinous process ( IQth year)
Fig. 103.
By 2 additional plates
1 for upper surface^
of body
. ].6th year
1 for under surface
of body
Fig. 104.— Atlas.
By .3 centers
1 for anter. arch {end cf 1st year)
I for each \m week
lateral mass j
Fig. 105.— Axis.
By 7 centers
2nd year
Gth month
1 /or each vertebral arch (i
or Sth iteek)
1 for body {4th month)
1 /or under sur/ace o/body
th
Fig. 106. — Lumbar vertebra.
2 additional centers for mammillary processes
Additional centers
for costal elements*
At birth
Fig. 107
At 4^ yrs
Fig. 108
Two epiphysial plates
for each lateral surface *
At
25th year
Fig. 107-109. — Ossification of the sacrum.
changes occur, excepting a gradual increase of these primary centers, the upper and under sur-
faces of the bodies and the ends of the transverse and spinous processes bemg cartilagmous.
THE SACRAL AND COCCYGEAL VERTEBRA
113
About the sixteenth year (Fig. 102), five secondary centers appear, one for the tip of each transverse
process, one for the extremity of the spinous process, one for the upper and one for the lower
surface of the body (Fig. 103). These fuse with the rest of the bone about the age of twenty-five
Exceptions to this mode of development occur in the first, second, and seventh cervical verte-
brae, and in the lumbar vertebrae.
Atlas.— The atlas is usually ossified from three centers (Fig. 104). Of these, one appears in
each lateral mass about the seventh week of fetal life, and extends backward; at birth, these
portions of bone are separated from one another behind by a narrow interval filled with cartilage
Between the third and fourth years they unite either directly or through the medium of a separate
center developed in the cartilage. At birth, the anterior arch consists of cartilage; in this a
separate center appears about the end of the first year after birth, and joins the lateral masses
from the sixth to the eighth year— the lines of union extending across the anterior portions of
the superior articular facets. OccasionaUy there is no separate center, the anterior arch being
formed by the forward extension and ultimate junction of the two lateral masses; sometimes
this arch is ossified from two centers, one on either side of the middle line.
Epistropheus or Axis.— The axis is ossified from five primary and two secondary centers (Fig.
105). The body and vertebral arch are ossified in the same manner as the corresponding parts
in the other vertebrae, viz., one center for the body, and two for the vertebral arch. The centers
for the arch appear about the seventh or eighth week of fetal fife, that for the body about the
fc irth or fifth month. The dens or odontoid process consists originally of a continuation upward
of the cartilaginous mass, in which the lower part of the body is formed. About the sixth month
of fetal life, two centers make their appearance in the base of this process: they are placed
laterally, and join before birth to form a conical bilobed mass deeply cleft above; the interval
between the sides of the cleft and the summit of the process is formed by a wedge-shaped piece
of cartilage. The base of the process is separated from the body by a cartilaginous disk, which
gradually becomes ossified at its circumference, but remains cartilaginous in its center until
advanced age. In this cartilage, rudiments of the lower epiphysial lamella of the atlas and
the upper epiphysial lamella of the axis may sometimes be found. The apex of the odontoid
process has a separate center which appears in the second and joins about the twelfth year; this
is the upper epiphysial lamella of the atlas. In addition to these there is a secondary center for
a thin epiphysial plate on the under surface of the body of the bone.
The Seventh Cervical Vertebra.— The anterior or costal part of the transverse process of this
vertebra is sometimes ossified from a separate center which appears about the sixth month of
fetal life, and joins the body and posterior part of the transverse process between the fifth and
sixth years. Occasionally the costal part persists as a separate piece, and, becoming lengthened
lateralward and forward, constitutes what is known as a cervical rib. Separate ossific centers
have also been found in the costal processes of the fourth, fifth, and sixth cervical vertebrae.
Lumbar Vertebrae.- The lumbar vertebrae (Fig. 106) have each two additional centers, for
the mammillary processes. The transverse process of the first lumbar is sometimes developed as
a separate piece, which may remain permanently ununited with the rest of the bone, thus form-
ing a lumbar rib — a peculiarity, however,
rarely met with.
Sacrum (Figs. 107 to 110).— The body
of each sacral vertebra is ossified from a
primary center and two epiphysial plates,
one for its upper and another for its under
surface, while each vertebral arch is ossi-
fied from two centers.
The anterior portions of the lateral parts
have six additional centers, two for each
of the first three vertebrae; these represent
the costal elements, and make their ap-
pearance above and lateral to the anterior
sacral foramina (Figs. 107, 108).
On each lateral surface two epiphysial plates are developed (Figs. 109, 1 10) : one for the auric-
ular surface, and another for the remaining part of the thin lateral edge of the bone.i
Periods of Ossification. — About the eighth or ninth week of fetal Ufe, ossification of the
central part of the body of the first sacral vertebra commences, and is rapidly followed by deposit
of ossific matter in the second and third; ossification does not commence in the bodies of the
lower two segments until between the fifth and eighth months of fetal life. Between the sixth
Center for
neural a
Center for
neural arch.
Costal
dement
Costal
element.
body.
Lateral
epiphysis.
Fig. 110. — Base of young sacrum
Lateral
epiphysis.
' The ends of the spinous processes of the upper three sacral vertebrae are sometimes developed from separate
epiphyses, and Fawcett (Anatomischer Anzeiger, 1907, Band xxx) states that a number of epiphysial nodules may be
seen in the sacrum at the age of eighteen years. These are distributed as follows: One for each of the mammillary pro-
cesses of the first sacral vertebra ; twelve — six on either side — in connection with the costal elements (two each for the first
and second and one each for the third and fourth) and eight for the transverse processes — four on either side — one each
for the first, third, fourth, and fifth. He is further of opinion that the lower part of each lateral surface of the sacrum
is formed by the extension and union of the third and fourth "costal" and fourth and fifth "transverse" epiphyses.
114 OSTEOLOGY
and eighth months ossification of the vertebral arches takes place; and about the same time the
costal centers for the lateral parts make their appearance. The junctions of the vertebral
arches with the bodies take place in the lower vertebrae as early as the second year, Lut are not
effected in the uppermost until the fifth or sixth year. About the sixteenth year the epiphysial
plates for the upper and under surfaces of the bodies are formed; and between the eighteenth and
twentieth years, those for the lateral surfaces make their appearance. The bodies of the sacral
vertebrae are, during early hfe, separated from each other by intervertebral fibrocartilages, but
about the eighteenth year the two lowest segments become united by bone, and the process of
bony union gradually extends upward, with the result that between the twenty-fifth and thirtieth
j^ears of hfe all the segments are united. On examining a sagittal section of the sacrum, the situa-
tions of the intervertebral fibrocartilages are indicated by a series of oval cavities (Fig. 99).
Coccyx. — The coccyx is ossified from four centers, one for each segment. The ossific nuclei
make their appearance in the following order: in the first segment between the first and fourth
years; in the second between the fifth and tenth years; in the third between the tenth and fifteenth
years; in the fourth between the fourteenth and twentieth years. As age advances, the segments
unite with one another, the union between the first and second segments being frequently delaj^ed
until after the age of twenty-five or thirty. At a late period of life, especially in females, the coccyx
often fuses with the sacrum.
THE VERTEBRAL COLUMN AS A WHOLE.
The vertebral column is situated in the median line, as the posterior part of the
trunk; its average length in the male is about 71 cm. Of this length the cervical
part measures 12.5 cm., the thoracic about 28 cm., the lumbar 18 cm., and the
sacrum and qoqqxx 12.5 cm. The female column is about 61 cm. in length.
Curves. — ^\'iewed laterally (Fig. Ill), the vertebral column presents several
curves, which correspond to the different regions of the column, and are called
cervical, thoracic, lumbar, and pelvic. The cervical curve, convex forward, begins
at the apex of the odontoid process, and ends at the middle of the second thoracic
vertebra; it is the least marked of all the curves. The thoracic curve, concave for-
ward, begins at the middle of the second and ends at the middle of the twelfth
thoracic vertebra. Its most prominent point behind corresponds to the spinous
process of the seventh thoracic vertebra. The lumbar curve is more marked in
the female than in the male; it begins at the middle of the last thoracic vertebra,
and ends at the sacrovertebral angle. It is convex anteriorly, the convexity of
the lower three vertebrae being much greater than that of the upper two. The
pelvic curve begins at the sacrovertebral articulation, and ends at the point of the
coccyx; its concavity is directed downward and forward. The thoracic and pelvic
curves are termed primary curves, because they alone are present during fetal life.
The cervical and lumbar curves are compensatory or secondary, and are developed
after birth, the former when the child is able to hold up its head (at three or four
months), and to sit upright (at nine months), the latter at twelve or eighteen
months, when the child begins to walk.
The vertebral column has also a slight lateral curvature, the convexity of which
is directed toward the right side. This may be produced by muscular action,
most persons using the right arm in preference to the left, especially in making
long-continued efforts, when the body is curved to the right side. In support of
this explanation it has been found that in one or two individuals who were left-
handed, the convexity was to the left side. By others this curvature is regarded as
being produced by the aortic arch and upper part of the descending thoracic
aorta — a view which is supported by the fact that in cases where the viscera are
transposed and the aorta is on the right side, the convexity of the curve is
directed to the left side.
Surfaces. — Anterior Surface. — When viewed from in front, the width of the bodies
of the vertebrse is seen to increase from the second cervical to the first thoracic;
there is then a slight diminution in the next three vertebrse; below this there
is again a gradual and progressive increase in width as low as the sacrovertebral
angle. From this point there is a rapid diminution, to the apex of the coccyx.
THE VERTEBRAL COLUMN AS A WHOLE
115
Posterior Surface. — The posterior surface
of the vertebral cohimn presents in the
median Hne the spinous processes. In the
cervical region (with the exception of the
second and seventh vertebrae) these are
short and horizontal, with bifid extremities.
In the upper part of the thoracic region
they are directed obliquely downward; in
the middle they are almost vertical, and in
the lower part they are nearly horizontal.
In the lumbar region they are nearly hori-
zontal. The spinous processes are separated
by considerable intervals in the lumbar
region, by narrower intervals in the neck,
and are closely approximated in the middle
of the thoracic region. Occasionally one of
these processes deviates a little from the
median line — a fact to be remembered in
practice, as irregularities of this sort are
attendant also on fractures or displacements
of the vertebral column. On either side of
the spinous processes is the vertebral groove
formed by the laminae in the cervical and
lumbar regions, where it is shallow, and by
the laminae and transverse processes in the
thoracic region, wdiere it is deep and broad ;
these grooves lodge the deep muscles of the
back. Lateral to the vertebral grooves are
the articular processes, and still more later-
ally the transverse processes. In the tho-
racic region, the transverse processes stand
backward, on a plane considerably behind
that of the same processes in the cervical
and lumbar regions. In the cervical region,
the transverse processes are placed in front
of the articular processes, lateral to the
pedicles and between the intervertebral
foramina. In the thoracic region they are
posterior to the pedicles, intervertebral
foramina, and articular processes. In the
lumbar region they are in front of the
articular processes, but behind the inter-
vertebral foramina.
Lateral Surfaces. — The lateral surfaces are
separated from the posterior surface by the
articular processes in the cervical and lum-
bar regions, and by the transverse processes
in the thoracic region. They present, in
front, the sides of the bodies of the verte-
brae, marked in the thoracic region by the
facets for articulation with the heads of
the ribs. More posteriorly are the inter-
vertebral foramina, formed by the juxta-
position of the vertebral notches, oval in
Jst cervical
or Atlas
2nd cervical
or Axis
W\
1st thoracic-\
2-\
4'
*-l
9-} f
:>H^'
io-l
ii~
)i^m-
■ If'S
«'U
tl
1^
1st lumbar -
'""i«ii^
>.:
.*^i
Fia. 111. — Lateral view of the vertebral column.
116
OSTEOLOGY
shape, smallest in the cervical and upper part of the thoracic regions, and gradually
increasing in size to the last lumbar. They transmit the spinal nerves and are
situated between the transverse processes in the cervical region, and in front of
them in the thoracic and lumbar regions.
Vertebral Canal. — The vertebral canal follows the different curves of the column;
it is large and triangular in those parts of the column which enjoy the greatest
freedom of movement, viz., the cervical and lumbar regions; and is small and
rounded in the thoracic region, where motion is more limited.
Abnormalities. — Occasionally the coalescence of the laminae is not completed, and conse-
quently a cleft is left in the arches of the vertebra), through which a protrusion of the spinal
membranes (dura mater and arachnoid), and generally of the medulla spinahs itself, takes place,
constituting the malformation known as spina bifida. This condition is most common in the
lumbosacral region, but it may occur in the thoracic or cervical region, or the arches throughout
the whole length of the canal may remain incomplete.
-First thoracic
Fig. 112. — The thorax from in front. (Spalteholz.)
THE THORAX.
The skeleton of the thorax or chest (Figs. 112, 113, 114) is an osseo-cartilaginous
cage, containing and protecting the principal organs of respiration and circulation.
THE THORAX
117
It IS conical in shape, being narrow above and broad below, flattened from before
backward, and longer behind than in front. It is somewhat reniform on trans-
verse section on account of the projection of the vertebral bodies into the cavitv
First thoracic
Fig. 113 — The thorax from behind. (Spalteholz.)
Boundaries. — The posterior surface is formed by the twelve thoracic vertebrae
and the posterior parts of the ribs. It is convex from above downward, and pre-
sents on either side of the middle line a deep groove, in consequence of the lateral
and backward direction which the ribs take from their vertebral extremities to
their angles. The anterior surface, formed by the sternum and costal cartilages,
is flattened or slightly convex, and inclined from above downward and forward.
The lateral surfaces are convex; they are formed by the ribs, separated from
each other by the intercostal spaces, eleven in number, which are occupied by
the Intercostal muscles and membranes.
The upper opening of the thorax is veniform in shape, being broader from side
to side than from before backward. It is formed by tlie first thoracic vertebra
behind, the upper margin of the sternum in front, and the first rib on either side.
118
OSTEOLOGY
It slopes downward and forward, so that the anterior part of the opening is on a
lower level than the posterior. Its antero-posterior diameter is about 5 cm., and
its transverse diameter about 10 cm. The lower opening is formed by the twelfth
thoracic vertebra behmd, by the eleventh and twelfth ribs at the sides, and in front
by the cartilages of the tenth, ninth, eighth, and seventh ribs, which ascend on
either side and form an angle, the subcostal angle, into the apex of which the
sternum
Twelfth thoracic
First lumbar
Fig. 114 — The thorax from the right. (Spalteholz.)
xiphoid process projects. The lower opening is wider transversely than from
before backward, and slopes obliquely downward and backward, it is closed by
the diaphragm which forms the floor of the thorax.
The thorax of the female differs from that of the male as follows: 1. Its capacity is less. 2.
The sternum is shorter. 3. The upper margin of the sternum is on a level with the lower part
of the body of the third thoracic vertebra, whereas in the male it is on a level with the lower
part of the body of the second. 4. The upper ribs are more movable, and so allow a greater
enlargement of the upper part of the thorax.
THE STERNUM
119
The Sternum (Breast Bone).
The sternum (Figs. 115 to 117) is an elongated, flattened bone, forming the
middle portion^ of the anterior wall of the thorax. Its upper end supports the
clavicles, and its margins articulate with the cartilages of the first seven pairs
STERNOCUEIDOMASTOIDEUS
SUBCLAVICS "\ '^'fffulaf
Fig. 115. — Anterior surface of sternum and costa cartilages.
of ribs. It consists of three parts, named from above downward, the manubrium,
the body or gladiolus, and the xiphoid process; in early life the body consists of four
segments or sterncbrce. In its natural position the inclination of the bone is oblique
from above, downward and forward. It is slightly convex in front and concave
120
OSTEOLOGY
behind; broad above, becoming narrowed at the point where the manubrium joins
the body, after which it again widens a little to below the middle of the body,
and then narrows to its lower extremity. Its average length in the adult is about
17 cm., and is rather greater in the male than in the female.
Manubrium (manubrium sterni). — The manubrium is of a somewhat quad-
rangular form, broad and thick abo^'e, narrow below at its junction with the body.
Surfaces. — Its anterior surface, convex from side to side, concave from above
downward, is smooth, and affords attachment on either side to the sternal
origins of the Pectoralis major and Sternocleidomastoideus. Sometimes the
ridges limiting the attachments of these muscles are very distinct. Its posterior
surface, concave and smooth, affords attachment on either side to the Sterno-
hyoideus and Sternothyreoideus.
For 1st
- custal
canilage
Sternal
angle
Xiphoid procesf
FiQ. 116. — Posterior surface of sternum.
Articular surface
for clavicle
Depression for
Idit costal cartilage
Manvbrium
Demifacets for 2nd costal
cartilage
Facet fpf Zrd costal cartilage
Body
Facet for Alh costal cartilage
Facet for 5th costal cartilage
- Facet for Gth costal cartilage
Facet for 7th costal cartilage
Xiphoid process
Fig. 117. — Lateral border of sternum.
Borders. — The superior border is the thickest and presents at its center the jugular
or prestemal notch; on either side of the notch is an oval articular surface, directed
upward, backward, and lateralward, for articulation with the sternal end of the
clavicle. The inferior border, oval and rough, is covered in a fresh state with a
thin layer of cartilage, for articulation with the body. The lateral borders are each
marked above by a depression for the first costal cartilage, and below by a small
facet, which, with a similar facet on the upper angle of the body, forms a notch
for the reception of the costal cartilage of the second rib. Between the depression
for the first costal cartilage and the demi-facet for the second is a narrow, curved
edge, ^\•hich slopes from above downward and medialward.
Body (corpus sterni; gladiolus). — The body, considerably longer, narrower, and
thinner than the manubrium, attains its greatest breadth close to the lower end.
Surfaces. — Its anterior surface is nearly fiat, directed upward and forward,
and marked by three transverse ridges which cross the bone opposite the third.
THE STERNUM 121
fourth, and fifth articuhir depressions.^ It affords attachment on either side to
the sternal origin of the PectoraHs major. At the junction of the third and fourth
pieces of the body is occasionally seen an orifice, the sternal foramen, of var^•ing
size and form. The posterior surface, slightly concave, is also marked by three
transverse lines, less distinct, however, than those in front; from its lower part,
on either side, the Transversus thoracis takes origin.
Borders.— The superior border is oval and articulates with the manubrium, the
junction of the two forming the sternal angle (anguhis Liidovici^). The inferior
border is narrow, and articulates with the xiphoid process. Each lateral border
(Fig. 117), at its superior angle, has a small facet, which with a similar facet on
the manubrium, forms a cavity for the cartilage of the second rib; below this
are four angular depressions which receive the cartilages of the third, fourth,
fifth, and sixth ribs, while the inferior angle has a small facet, which, with a cor-
responding one on the xiphoid process, forms a notch for the cartilage of the seventh
rib. These articular depressions are separated by a series of curved interarticular
intervals, which diminish in length from above downward, and correspond to
the intercostal spaces. Most of the cartilages belonging to the true ribs, as will
be seen from the foregoing description, articulate with the sternum at the lines
of junction of its primitive component segments. This is well seen in many of
the lower animals, where the parts of the bone remain ununited longer than in
man.
Xiphoid Process (processus xipJwideus; ensiform or xiphoid appendix). — The
xiphoid process is the smallest of the three pieces: it is thin and elongated,
cartilaginous in structure in youth, but more or less ossified at its upper part in
the adult.
Surfaces. — Its anterior surface affords attachment on either side to the anterior
costoxiphoid ligament and a small part of the Rectus abdominis; its posterior sur-
face, to the posterior costoxiphoid ligament and to some of the fibers of the dia-
phragm and Transversus thoracis, its lateral borders, to the aponeuroses of the
abdominal muscles. Above, it articulates wdth the lower end of the body, and
on the front of each superior angle presents a facet for part of the cartilage of the
seventh rib; below, by its pointed extremity, it gives attachment to the Imea
alba. The xiphoid process varies much in form; it may be broad and thin, pointed,
bifid, perforated, curved, or deflected considerably to one or other side.
Structure.^The sternum is composed of highly vascular cancellous tissue, covered by a thin
layer of compact bone which is thickest in the manubrium between the articular facets for the
clavicles.
Ossification. — The sternum originally consists of two cartilaginous bars, situated one on either
side of the median plane and connected with the cartilages of the upper nine ribs of its own side.
These two bars fuse with each other along the middle line to form the cartilaginous sternum which
is ossified from six centers: one for the manubrium, four for the body, and one for the xiphoid
process (Fig. IIS). The ossific centers appear in the intervals between the articular depressions
for the costal cartilages, in the following order; in the manubrium and first piece of the body,
during the sixth month ; in the second and third pieces of the body, during the seventh month of
fetal life; in its fourth piece, during the first year after birth; and in the xiphoid process, between
the fifth and eighteenth years. The centers make their appearance at the upper parts of the seg-
ments, and proceed gradually downward.^ To these may be added the occasional existence of
two small episternal centers, which make their appearance one on either side of the jugular notch;
they are probably vestiges of the episternal bone of the monotremata and lizards. Occasionally
some of the segments are formed from more than one center, the number and position of which
vary (Fig. 120). Thus, the first piece may have two, three, or even six centers. When two are
1 Paterson (The Human Sternum, 1904), who examined 521 specimens, points out that these ridges are altogether
absent in 26.7 per cent. ; that in 09 per cent, a ridge exists opposite the third co.-itiil attachment; in 39 per cent, opposite
the fourth; and in 4 per cent, only, opposite the fifth.
2 Named after the French surgeon Antoine Louis, 1723-1792. The Latin name angulus Ludovici is not infrequently
mistranslated into English as " the angle of Ludwig. "
^ Out of 141 sterna between the time of birth and the age of sixteen years, Paterson {.op. cit.) found the fourth or
lowest center for the body present only in thirty-eight cases — i. e., 26.9 per cent.
122
OSTEOLOGY
Time
of
appearance
Time
of
union
In
number of
centers
In
mode of
union
1 for manvhrium
^6th month
4 for body
5 1st year after birth
7th month
I „ , 1 for xiphoid \
!»' process j5th to 18th year
Fig. lis. — Ossification of the sternum.
Rarely unite, except in old age
Between puberty and the 25th year
Partly cartilaginous to advanced life
Fig. 119
for first piece, two or more centers
for second piece, usually one
for third \
(2, placed laterally
for fourth J
for fifth
Fig. 120. — Peculiarities.
Arrest of ossification of lateral pieces,
produciiig :
Sternal fissure, and
Sternul foramen
Fig. 121
THE RIBS 123
present, they are generally situated one above the other, the upper being the larger; the second
piece has seldom more than one; the third, fourth, and fifth pieces are often formed from two
centers placed laterally, the irregular union of which explains the rare occurrence of the sternal
foramen (Fig. 121), or of the vertical fissure which occasionally intersects this part of the bone
constituting the malformation known as fissura sterni; these conditions are further explained by
the manner in which the cartilaginous sternum is formed. More rarely still the upper end of the
sternum may be divided by a fissure. Union of the various centers of the body begins about
puberty, and proceeds from below upward (Fig. 119) ; by the age of twenty-five they are all united.
The xiphoid process may become joined to the body before the age of thirty, but this occurs
more frequently after forty; on the other hand, it sometimes remains ununited in old age. In
advanced life the manubrium is occasionally joined to the body by bone. When this takes place,
however, the bony tissue is generally only superficial, the central portion of the intervening
cartilage remaining unossified.
Articulations. — The sternum articulates on either side with the clavicle and upper seven costal
cartilages.
The Ribs (Costse).
The ribs are elastic arches of bone, which form a large part of the thoracic
skeleton. They are twelve in number on either side; but this number mav be
increased by the development of a cervical or lumbar rib, or may be diminished
to eleven. The first seven are connected behind with the vertebral column, and in
front, through the intervention of the costal cartilages, with the sternum (Fig.
115); they are called true or vertebro-stemal ribs.^ The remaining five are false
ribs; of these, the first three have their cartilages attached to the cartilage of the
rib above (vertebro-chondral) : the last two are free at their anterior extremities
and are termed floating or vertebral ribs. The ribs vary in their direction, the
upper ones being less oblique than the lower; the obliquity reaches its maximum
at the ninth rib, and gradually decreases from that rib to the twelfth. The ribs
are situated one below the other in such a manner that spaces called intercostal
spaces are left between them. The length of each space corresponds to that of
the adjacent ribs and their cartilages; the breadth is greater in front than behind,
and between the upper than the lower ribs. The ribs increase in length from
the first to the seventh, below which thev diminish to the twelfth. In breadth
they decrease from above downward; in the upper ten the greatest breadth is at
the sternal extremity.
Common Characteristics of the Ribs (Figs. 122, 123). — A rib from the middle
of the series should be taken in order to study the common characteristics of these
bones.
Each rib has two extremities, a posterior or vertebral, and an anterior or sternal,
and an intervening portion — the body or shaft.
Posterior Extremity. — The posterior or vertebral extremity presents for examination
a head, neck, and tubercle.
The head is marked by a kidney-shaped articular surface, divided by a hori-
zontal crest into two facets for articulation with the depression formed on the
bodies of two adjacent thoracic vertebrae; the upper facet is the smaller; to the
crest is attached the interarticular ligament.
The neck is the flattened portion which extends lateralward from the head; it
is about 2.5 cm. long, and is placed in front of the transverse process of the
lower of the two vertebrse with which the head articulates. Its anterior surface is
flat and smooth, its posterior rough for the attachment of the ligament of the neck,
and perforated by numerous foramina. Of its two borders the superior presents a
rough crest {crista colli costxp) for the attachment of the anterior costotransverse
ligament; its inferior border is rounded. On the posterior surface at the junction
of the neck and body, and nearer the lower than the upper border, is an eminence
' Sometimes the eighth rib cartilage articulates with the sternum; this condition occurs more frequently on the
right than on the left side.
124
OSTEOLOGY
—the tubercle ; it consists of an articular and a non-articular portion. The articular
portion, the lower and more medial of the two, presents a small, oval surface for
Angle
Non-articular part 0/ tubercle
Articular part of tubercle
^
Ni
K
Fig. 122. — A central rib of the left side.
Inferior aspect.
articulation with the end of the transverse pro-
cess of the lower of the two vertebrae to w^hich
the head is connected. The non-articular por-
tion is a rough elevation, and affords attach-
ment to the ligament of the tubercle. The
tubercle is much more prominent in the upper
than in the lower ribs.
Body. — The body or shaft is thin and flat,
with two surfaces, an external and an internal;
and two borders, a superior and an inferior.
The external surface is convex, smooth, and
marked, a little in front of the tubercle, by a
prominent line, directed downward and lateral-
ward; this gives attachment to a tendon of
the lliocostalis, and is called the angle. At
this point the rib is bent in two directions,
and at the same time twisted on its long axis.
If the rib be laid upon its lower border, the
portion of the body in front of the angle rests
upon this border, while the portion behind the
angle is bent medialward and at the same
time tilted upward; as the result of the twist-
ing, the external surface, behind the angle,
looks downward, and in front of the angle,
slightly upward. The distance between the
angle and the tubercle is progressively greater
from the second to the tenth ribs. The por-
tion between the angle and the tubercle is
rounded, rough, and irregular, and serves for
the attachment of the Longissimus dorsi. The
internal surface is concave, smooth, directed a
little upward behind the angle, a little down-
ward in front of it, and is marked by a ridge
which commences at the lower extremity of
the head; this ridge is strongly marked as far
as the angle, and gradually becomes lost at
the junction of the anterior and middle thirds
of the bone. Between it and the inferior
border is a groove, the costal groove, for the
intercostal vessels and nerve. At the back
part of the bone, this groove belongs to the
I
THE RIBS
125
inferior border, but just in front of the angle, where it is deepest and broadest, it is
on the internal surface. The superior edge of the groove is rounded and serves
for the attachment of an Intercostalis internus; the inferior edge corresponds to
the lower margin of the rib, and gi\x>s attachment to an Intercostalis externus.
Within the groove are seen the orifices of numerous small foramina for nutrient
vessels which traverse the shaft obliquely from before backward. The superior
border, thick and rounded, is marked by an external and an internal lip, more
distinct behind than in front, which serve for the attachment of Intercostales
externus and internus. The inferior border is thin, and has attached to it an Inter-
costalis externus.
Anterior Extremity.— The anterior or sternal extremity is flattened, and presents a
porous, o\i\\, concave depression, into which the costal cartilage is received.
Peculiar Ribs.— The first, second, tenth, eleventh, and twelfth ribs present
certain variations from the common characteristics described above, and require
special consideration.
■ Demifacet for vertebra
Inter articular crest
Demifacet for vertebra
Costal groove
Fig. 123. — A central rib of the left side, viewed from behind.
First Rib. — The first rib (Fig. 1 24) is the most curved and usually the shortest
of all the ribs; it is broad and flat, its surfaces looking upward and downward,
and its borders inward and outward. The head is small, rounded, and possesses
only a single articular facet, for articulation with the body of the first thoracic
vertebra. The neck is narrow and rounded. The tubercle, thick and prominent,
is placed on the outer border. There is no angle, but at the tubercle the rib is
slightly bent, with the convexity upward, so that the head of the bone is directed
downward. The upper surface of the body is marked by two shallow grooves,
separated from each other by a slight ridge prolonged internally into a tubercle,
the scalene tubercle, for the attachment of the Scalenus anterior; the anterior
groove transmits the subclavian vein, the posterior the subclavian artery and
the lowest trunk of the brachial plexus. ^ Behind the posterior groove is a rough
area for the attachment of the Scalenus medius. The imder surface is smooth,
and destitute of a costal groove. The outer border is convex, thick, and rounded,
and at its posterior part gives attachment to the first digitation of the Serratus
anterior; the inner border is concave, thin, and sharp, and marked about its center
by the scalene tubercle. The anterior extremity is larger and thicker than that
of any of the other ribs.
Second Rib. — The second rib (Fig. 125) is much longer than the first, but has a
very similar curvature. The non-articular portion of the tubercle is occasionally
1 Anat. Anzeiger, 1910, Band xxxvi.
126
OSTEOLOGY
only feebly marked. The angle is slight, and situated close to the tubercle. The
body is not twisted, so that both ends touch any plane surface upon which it may
be laid; but there is a bend, with its convexity upward, similar to, though smaller
than that found in the first rib. The body is not flattened horizontally like that
of the first rib. Its external surface is convex, and looks upward and a little outward ;
near the middle of it is a rough eminence for the origin of the lower part of the
Fig. 124
Angle
Fig. 126
Single articular facet — "
FiQ. 127
Single articular facet
Fia. 128
Single articular facet ■
Figs. 124 to 128. — Peculiar ribs.
first and the whole of the second digitation of the Serratus anterior; behind and
above this is attached the Scalenus posterior. The internal surface, smooth, and
concave, is directed downward and a little inward: on its posterior part there is
a short costal groove.
Tenth Rib. — The tenth rib (Fig. 126) has only a single articular facet on its head.
Eleventh and Twelfth Ribs.— The eleventh and twelfth ribs (Figs. 127 and 128)
have each a single articular facet on the head, which is of rather large size; they
THE COSTAL CARTILAGES 127
have 710 necks or tubercles, and are pointed at their anterior ends. The eleventh
has a slight angle and a shallow costal groove. The twelfth has neither; it is much
shorter than the eleventh, and its head is inclined slightly downward. Sometimes
the twelfth rib is even shorter than the first.
Structure. — The ribs consist of highly vascular cancellous tissue, enclosed in a thin layer of
compact bone.
Ossification. — Each rib, with the exception of the last two, is ossified from four centers; a
primary center for the body, and three epiphysial centers, one for the head and one each for the
articular and non-articular parts of the tubercle. The eleventh and twelfth ribs have each only
two centers, those for the tubercles being wanting. Ossification begins near the angle toward the
end of the second month of fetal life, and is seen first in the sixth and seventh ribs. The epiphyses
for the head and tubercle make their appearance between the sixteenth and twentieth years, and
are united to the body about the twenty-fifth year. Fawcett^ states that "in all probability there
is usually no epiphysis on the non-articular part of the tuberosity below the sixth or seventh rib.
The Costal Cartilages (Cartilagines Costales).
The costal cartilages (Fig. 115) are bars of hyaline cartilage which serve to
prolong the ribs forward and contribute very materially to the elasticity of the
walls of the thorax. The first seven pairs are connected with the sternum; the
next three are each articulated with the lower border of the cartilage of the pre-
ceding rib; the last two have pointed extremities, which end in the wall of the
abdomen. Like the ribs, the costal cartilages vary in their length, breadth, and
direction. They increase in length from the first to the seventh, then gradually
decrease to the twelfth. Their breadth, as well as that of the intervals between
them, diminishes from the first to the last. They are broad at their attachments
to the ribs, and taper toward their sternal extremities, excepting the first two,
which are of the same breadth throughout, and the sixth, seventh, and eighth,
which are enlarged where their margins are in contact. They also vary in direc-
tion: the first descends a little, the second is horizontal, the third ascends slightly,
while the others are angular, following the course of the ribs for a short distance,
and then ascending to the sternum or preceding cartilage. Each costal cartilage
presents two surfaces, two borders, and two extremities.
Surfaces. — The anterior surface is convex, and looks forward and upward: that
of the first gives attachment to the costoclavicular ligament and the Subclavius
muscle; those of the first six or seven at their sternal ends, to the Pectoralis major.
The others are covered by, and give partial attachment to, some of the flat muscles
of the abdomen. The posterior surface is concave, and directed backward and
downward; that of the first gives attachment to the Sternothyroideus, those of
the third to the sixth inclusive to the Trans versus thoracis, and the six or seven
inferior ones to the Transversus abdominis and the diaphragm.
Borders. — Of the two borders the superior is concave, the inferior convex; they
afford attachment to the Intercostales interni : the upper border of the sixth gives
attachment also to the Pectoralis major. The inferior borders of the sixth, seventh,
eighth, and ninth cartilages present heel-like projections at the points of greatest
convexity. These projections carry smooth oblong facets which articulate respec-
tively with facets on slight projections from the upper borders of the seventh,
eighth, ninth, and tenth cartilages.
Extremities. — The lateral end of each cartilage is continuous with the osseous
tissue of the rib to which it belongs. The medial end of the first is continuous
with the sternum; the medial ends of the six succeeding ones are rounded and are
received into shallow concavities on the lateral margins of the sternum. The
medial ends of the eighth, ninth, and tenth costal cartilages are pointed, and are
connected each with the cartilage immediately above. Those of the eleventh and
twelfth are pointed and free. In old age the costal cartilages are prone to undergo
superficial ossification.
1 Journal of Anatomy and Physiology, vol. xlv.
128
OSTEOLOGY
Cervical ribs derived from the seventh cervical vertebra (page S3) are of not infrequent occur-
rence, and are important chnically because they may give rise to obscure nervous or vascular
symptoms. The cervical rib may be a mere epiphysis articulating only with the transverse process
of the vertebra, but more commonly it consists of a defined head, neck, and tubercle, with or
without a body. It extends lateralward, or forward and lateralward, into the postft-ior triangle
of the neck, where it may terminate in a free end or may join the first thoracic rib, the first costal
cartilage, or the sternum.^ It varies much in shape, size, direction, and -mobility. If it reach
far enough forward, part of the brachial plexus and the subclavian artery and vein cross over
it, and are aj)t to suffer compression in so doing. Pressure on the artery may obstruct the circula-
tion so much that arterial thrombosis results, causing gangrene of the finger tips. Pressure on
the nerves is commoner, and affects the eighth cervical and first thoracic nerves, causing paralj'sis
of the muscles they supply, and neuralgic pains and paresthesia in the area of skin to which they
are distributed : no oculopupillary changes are to be found.
The thorax is frequently found to be altered in shape in certain diseases.
In rickets, the ends of the ribs, where they join the costal cartilages, become enlarged, giving
rise to the so-caUed "rickety rosary," which in mild cases is only found on the internal surface
of the thorax. Lateral to these enlargements the softened ribs sink in, so as to i^resent a groove
passing dowmward and lateralward on either side of the sternum. This bone is forced forward
by the bending of the ribs, and the antero-posterior diameter of the chest is increased. The ribs
affected are the second to the eighth, the lower ones being prevented from falling in bj- the pres-
ence of the liver, stomach, and spleen ; and when the abdomen is distended, as it often is in rickets,,
the lower ribs may be pushed outward, causing a transverse groove (Harrison's sulcus) just
above the costal arch. This deformit}'' or forward projection of the sternum, often asymmetrical,
is known as pigeon breast, and may be taken as evidence of active or old rickets except in cases
of primary spinal curvatui'e. In many instances it is associated in children with obstruction in
the upper air passages, due to enlarged tonsils or adenoid growths. In some rickety children or
adults, and also in others who give no history or further evidence of having had rickets, an opposite
condition obtains. The lower part of the sternum and often the xiphoid process as well are deeply
depressed backward, producing an oval hollow in the lower sternal and upper epigastric regions.
This is known as funnel breast (German, Trichterbrnst); it never appears to produce the least
disturbance of any of the vital functions. The phthisical chest is often long and narrow, and with
great obliquity of the ribs and projection of the scapulae. In pulmonary emphysema the chest is
enlarged in all its diameters, and presents on section an almost circular outline. It has received
the name of the barrel-shaped chest. In severe cases of lateral curvature of the vertebral column
the thorax becomes much distorted. In consequence of the rotation of the bodies of the vertebrae
which takes place in this disease, the ribs opposite the convexity of the dorsal curve become
extremely convex behind, being thrown out and bulging, and at the same time flattened in front,
so that the two ends of the same rib are almost parallel. Coincidently with this the ribs on the
opposite side, on the concavity of the curve, are sunk and depressed behind, and bulging and
convex in front.
THE SKULL.
The skull is supported on the summit of the vertebral column, and is of an
oval shape, wider behind than in front. It is composed of a series of flattened
or irregular bones which, with one exception (the mandible), are immovably
jointed together. It is divisible into two parts: (1) the cranium, which lodges
and protects the brain, consists of eight bones, and (2) the skeleton of the face,
of fourteen, as follows:
Skull, 22 bones
Cranium, 8 bones
. Face, 14 bones
Occipital.
Two Parietals.
Frontal.
Two Temporals.
Sphenoidal.
Ethmoidal.
^ Two Nasals.
Two :\Iaxillffi.
Two Lacrimals.
Two Zygomatics.
Two Palatines.
Two Inferior Nasal Conchse.
Vomer.
[ ]Mandible.
> W. Thorburn, The Medical Chronicle, Manchester, 1907, 4th series, xiv, No. 3
THE OCCIPITAL BONE
129
In the Basle nomenclature, certain bones developed in association with the nasal
capsule, viz., the inferior nasal conchas, the lacrimals, the nasals, and the vomer,
are grouped as cranial and not as facial bones.
The hyoid bone, situated at the root of the tongue and attached to the base
of the skull by ligaments, is described in this section.
THE CRANIAL BONES (OSSA CRANE).
The Occipital Bone (Os Occipitale).
The occipital bone (Figs. 129, 130), situated at the back and lower part of the
cranium, is trapezoid in shape and curved on itself. It is pierced by a large oval
aperture, the foramen magnum, through which the cranial cavity communicates
with the vertebral canal.
Highest
mtchal I
Hypoglossal canal
Constrictor pharyngis
superior
Fig. 129.— Occipital bone. Outer surface.
The curved, expanded plate behind the foramen magnum is named the squama;
the thick, somewhat quadrilateral piece in front of the foramen is called the
basilar part, whilst on either side of the foramen is the lateral portion.
The Squama {squama occipitalis). — The squama, situated above and behind
the foramen magnum, is curved from above downward and from side to side.
Surfaces. — The external surface is convex and presents midway between the
summit of the bone and the foramen magnum a prominence, the external occipital
protuberance. Extending lateralward from this on either side are two curved
lines, one a little above the other. The upper, often faintly marked, is named
the highest nuchal line, and to it the galea aponeurotica is attached. The lower
9
130
OSTEOLOGY
is termed the superior nuchal line. That part of the squama which lies above
the highest nuchal lines is named the planum occipitale, and is covered by the
Occipitalis muscle; that below, termed the planum nuchale, is rough and irregular
for the attachment of several muscles. From the external occipital protuberance
a ridge or crest, the median nuchalline, often faintly marked, descends to the fora-
men magnum, and affords attachment to the ligamentum nuchae; running from
the middle of this line across either half of the nuchal plane is the inferior nuchal
line. Several muscles are attached to the outer surface of the squama, thus:
the superior nuchal line gives origin to the Occipitalis and Trapezius, and msertion
to the Sternocleidomastoideus and Splenius capitis: into the surface between
Su/ien'o .
S u/i pj.
Inferior A ngLe
Fig. 130. — Occipita bone.
the superior and inferior nuchal lines the Semispinalis capitis and the Obliquus
capitis superior are inserted, while the inferior nuchal line and the area below
it receive the insertions of the Recti capitis posteriores major and minor. The
posterior atlantooccipital membrane is attached around the postero-lateral part
of the foramen magnum, just outside the margin of the foramen.
The internal surface is deeply concave and divided into four fossae by a cruciate
eminence. The upper two fossae are triangular and lodge the occipital lobes of
the cerebrum; the lower two are quadrilateral and accommodate the hemispheres
of the cerebellum. At the point of intersection of the four divisions of the cruciate
eminence is the internal occipital protuberance. From this protuberance the upper
division of the cruciate eminence runs to the superior angle of the bone, and on
THE OCCIPITAL BONE 131
one side of it (generally the right) is a deep groove, the sagittal sulcus, which lodges
the hinder part of the superior sagittal sinus; to the margins of this sulcus the falx
cerebri is attached. The lower division of the cruciate eminence is prominent,
and is named the internal occipital crest; it bifurcates near the foramen magnum
and gives attachment to the falx cerebelli; in the attached margin of this falx
is the occipital sinus, which is sometimes duplicated. In the upper part of the
internal occipital crest, a small depression is sometimes distinguishable; it is
termed the vermian fossa since it is occupied by part of the vermis of the cerebellum.
Transverse grooves, one on either side, extend from the internal occipital protuber-
ance to the lateral angles of the bone; those grooves accommodate the transverse
sinuses, and their prominent margins give attachment to the tentorium cerebelli.
The groove on the right side is usually larger than that on the left, and is
continuous with that for the superior sagittal sinus. Exceptions to this condition
are, however, not infrequent; the left may be larger than the right or the two
may be almost equal in size. The angle of union of the superior sagittal and trans-
verse sinuses is named the confluence of the sinuses {torcular Herophili^), and its
position is indicated by a depression situated on one or other side of the
protuberance.
Lateral Parts {pars lateralis). — The lateral parts are situated at the sides of
the foramen magnum; on their under surfaces are the condyles for articulation
with the superior facets of the atlas. The condyles are oval or reniform in shape,
and their anterior extremities, directed forward and medialward, are closer together
than their posterior, and encroach on the basilar portion of the bone; the posterior
extremities extend back to the level of the middle of the foramen magnum. The
articular surfaces of the condyles are convex from before backward and from
side to side, and look downward and lateral ward. To their margins are attached
the capsules of the atlantooccipital articulations, and on the medial side of each
is a rough impression or tubercle for the alar ligament. At the base of either
condyle the bone is tunnelled by a short canal, the hypoglossal canal {anterior
condyloid foramen). This begins on the cranial surface of the bone immediately
above the foramen magnum, and is directed lateralward and forward above the
condyle. It may be partially or completely divided into two by a spicule of bone ;
it gives exit to the hypoglossal or twelfth cerebral nerve, and entrance to a meningeal
branch of the ascending pharyngeal artery. Behind either condyle is a depression,
the condyloid fossa, which receives the posterior margin of the superior facet of
the atlas when the head is bent backward; the floor of this fossa is sometimes
perforated by the condyloid canal, through which an emissary vein passes from the
transverse sinus. Extending lateralward from the posterior half of the condyle
is a quadrilateral plate of bone, the jugular process, excavated in front by the jugular
notch, which, in the articulated skull, forms the posterior part of the jugular fora-
men. The jugular notch may be divided into two by a bony spicule, the intra-
jugular process, which projects lateralward above the hypoglossal canal. The
under surface of the jugular process is rough, and gives attachment to the Rectus
capitis lateralis muscle and the lateral atlantooccipital ligament; from this
surface an eminence, the paramastoid process, sometimes projects downward, and
may be of sufficient length to reach, and articulate with, the transverse process
of the atlas. Laterally the jugular process presents a rough quadrilateral or tri-
angular area which is joined to the jugular surface of the temporal bone by a plate
of cartilage; after the age of twenty-five this plate tends to ossify.
The upper surface of the lateral part presents an oval eminence, the jugular
tubercle, which overlies the hypoglossal canal and is sometimes crossed by an
oblique groove for the glossopharyngeal, vagus, and accessory nerves. On the
' The columns of blood coming in different directions were supposed to be pressed together at this point {iorcular.
a wine press).
132
OSTEOLOGY
upper surface of the jugular process is a deep groove which curves medialward
and forward and is continuous with the jugular notch. This groove lodges the
terminal part of the transverse sinus, and opening into it, close to its medial
margin, is the orifice of the condyloid canal.
Basilar Part (pars basilaris). — The basilar part extends forward and upward
from the foramen magnum, and presents in front an area more or less quadrilateral
in outline. In the young skull this area is rough and uneven, and is joined to the
body of the sphenoid by a plate of cartilage. By the twenty-fifth year this cartil-
aginous plate is ossified, and the occipital and sphenoid form a continuous bone.
Surfaces. — On its lower surface, about 1 cm. in front of the foramen magnum,
is the pharyngeal tubercle which gives attachment to the fibrous raphe of the pharynx.
On either side of the middle line the Longus capitis and Rectus capitis anterior
are inserted, and immediately in front of the foramen magnum the anterior
atlantooccipital membrane is attached.
The upper surface presents a broad, shallow groove Avhich inclines upward
and forward from the foramen magnum; it supports the medulla oblongata, and
near the margin of the foramen magnum gives attachment to the membrana
tectoria. On the lateral margins of this surface are faint grooves for the inferior
petrosal sinuses.
Foramen Magnum. — The foramen magnum is a large oval aperture with its long
diameter antero-posterior ; it is wider behind than in front where it is encroached
upon by the condyles. It transmits the medulla oblongata and its membranes,
the accessory nerves, the vertebral arteries, the anterior and posterior spinal
arteries, and the membrana tectoria and alar ligaments.
Angles. — The superior angle of the occipital bone articulates with the occipital
angles of the parietal bones and, in the fetal skull, corresponds in position with the
posterior fontanelle. The inferior angle is fused with the body of the sphenoid.
The lateral angles are situated at the extremities of the grooves for the transverse
sinuses: each is received into the interval
between the mastoid angle of the parietal
and the mastoid part of the temporal.
Borders. — The superior borders extend
from the superior to the lateral angles:
thej" are deeply serrated for articulation
with the occipital borders of the parietals,
and form by this union the lambdoidal
suture. The inferior borders extend from
the lateral angles to the inferior angle;
the upper half of each articulates with
the mastoid portion of the corresponding
temporal, the lower half with the petrous
part of the same bone. These two por-
tions of the inferior border are separated
from one another by the jugular process,
the notch on the anterior surface of which
forms the posterior part of the jugular
foramen.
Fig. 131. — Occipital bone at birth.
Structure. — The occipital, like the other cranial
bones, consists of two compact lamellae, called
the outer and inner tables, between which is the cancellous tissue or diploe; the bone is especially
thick at the ridges, protuberances, condyles, and anterior part of the basilar part; in the inferior
fossge it is thin, semitransparent, and destitute of diploe.
Ossification (Fig. 131). — The planum occipitale of the squama is developed in membrane,
and may remain separate throughout life when it constitutes the interparietal bone; the rest of
Planum
< ccipitale
Planum
imcfiale
Kerckring's
center
Lateral
part
Basilar part
1
THE PARIETAL BONE
133
the bone is developed in cartilage. The number of nuclei for the planum occipitale is usually
given as four, two appearing near the middle line about the second month, and two some little
distance from the middle line about the third month of fetal life. The planum nuchalc of the
squama is ossified from two centers, which appear about the seventh week of fetal life and soon
unite to form a single piece. Union of the upper and lower portions of the squama takes place
in the third month of fetal life. An occasional center (Kerckring) appears in the posterior margin
of the foramen magnum dm'ing the fifth month; this forms a separate ossicle (sometimes double)
which unites with the rest of the squama before birth. Each of the lateral parts begins to
ossify from a single center during the eighth week of fetal hfe. The basilar portion is ossified
from two centers, one in front of the other; these appear about the sixth week of fetal life and
rapidly coalesce. Mall' states that the planum occipitale is ossified from two centers and the
basilar portion from one. About the fourth year the squama and the two lateral portions unite,
and about the sixth year the bone consists of a single piece. Between the eighteenth and twenty-
fifth years the occipital and sphenoid become united, forming a single bone.
Articulations.^The occipital articulates with six bones: the two parietals, the two temporals,
the sphenoid, and the atlas.
The Parietal Bone (Os Parietale).
The parietal bones form, by their union, the sides and roof of the cranium. Each
bone is irregularly quadrilateral in form, and has two surfaces, four borders,
and four angles.
Articulates with opposite parietal bone
With sphenoid
With mastoid portion of
temvoral bone
Fig. 132. — -Left parietal bone. Outer surface.
Surfaces.— The external surface (Fig. 132) is convex, smooth, and marked near
the center by an eminence, the parietal eminence {tuber paridale), which indicates
the point where ossification commenced. Crossing the middle of the bone in an
• American Journal of Anatomy, 1906, vol. v.
134
OSTEOLOGY
arched direction are two curved lines, the superior and inferior temporal lines; the
former gives attachment to the temporal fascia, and the latter indicates the upper
limit of the muscular origin of the Temporalis. Above these lines the bone is
covered by the galea aponeurotica ; below them it forms part of the temporal
fossa, and affords attachment to the Temporalis muscle. At the back part and
close to the upper or sagittal border is the parietal foramen, which transmits a
vein to the superior sagittal sinus, and sometimes a small brancli of the occipital
artery; it is not constantly present, and its size varies considerably.
The internal surface (Fig. 133) is concave; it presents depressions corresponding
to the cerebral convolutions, and numerous furrows for the ramifications of the
middle meningeal vessel;^ the latter run upward and backward from the sphenoidal
angle, and from the central and posterior part of the squamous border. Along
the upper margin is a shallow groove, which, together with that on the opposite
!^^m^f^bA',.
Occipital , r'~-\^Jf
angle [ '■/\^
;'"'-... I. J'^'onial
angle
Mastoid
angle
Sphenoidal angle
Fig. 133. — Left parietal bone. Inner surface.
parietal, forms a channel, the sagittal sulcus, for the superior sagittal sinus; the
edges of the sulcus afford attachment to the falx cerebri. Near the groove are
several depressions, best marked in the skulls of old persons, for the arachnoid
granulations {Pacchionian bodies). In the groove is the internal opening of the
parietal foramen when that aperture exists.
Borders. — The sagittal border, the longest and thickest, is dentated and articu-
lates with its fellow of the opposite side, forming the sagittal suture. The squamous
border is divided into three parts: of these, the anterior is thin and pointed, bevelled
at the expense of the outer surface, and overlapped by the tip of the great wing
of the sphenoid; the middle portion is arched, bevelled at the expense of the outer
surface, and overlapped by the squama of the temporal; the posterior part is thick
and serrated for articulation with the mastoid portion of the temporal. The
» Journal of Anatomy and Physiology, 1912, vol. xlvi.
THE FRONTAL BONE 135
frontal border is deeply serrated, and bevelled at the expense of the outer surface
above and of the inner below; it articulates with the frontal bone, forming one-
half of the coronal suture. The occipital border, deeply denticulated, articulates
with the occipital, forming one-half of the lambdoidal suture.
Angles.— The frontal angle is practically a right angle, and corresponds with
the point of meeting of the sagittal and coronal sutures; this point is named the
bregma; in the fetal skull and for about a year and a half after birth this region is
membranous, and is called the anterior fontanelle. The sphenoidal angle, thin
and acute, is received into the interval between the frontal bone and the great
wing of the sphenoid. Its inner surface is marked by a deep groove, sometimes
a canal, for the anterior divisions of the middle meningeal artery. The occipital
angle is rounded and corresponds with the point of meeting of the sagittal and
lambdoidal sutures— a point which is termed the lambda; in the fetus this part
of the skull is membranous, and is called the posterior fontanelle. The mastoid
angle is truncated; it articulates with the occipital bone and with the mastoid
portion of the temporal, and presents on its inner surface a broad, shallow groove
which lodges part of the transverse sinus. The point of meeting of this angle
with the occipital and the mastoid part of the temporal is named the asterion.
Ossification. — The parietal bone is ossified in membrane from a single center, which appears
at the parietal eminence about the eighth week of fetal life. Ossification gradually extends in
a radial manner from the center toward the margins of the bone; the angles are consequently
the parts last formed, and it is here that the fontanelles exist. Occasionally the parietal bone
is divided into two parts, upper and lower, by an antero-posterior suture.
Articulations. — The parietal articulates with five bones: the opposite parietal, the occipital,
frontal, temporal, and sphenoid.
The Frontal Bone (Os Frontale).
The frontal bone resembles a cockle-shell in form, and consists of two portions
— a vertical portion, the squama, corresponding with the region of the forehead;
and an orbital or horizontal portion, which enters into the formation of the roofs
of the orbital and nasal cavities.
Squama {squama frontalis). — Surfaces. — The external surface (Fig. 134) of this
portion is convex and usually exliibits, in the lower part of the middle line, the
remains of the frontal or metopic suture; in infancy this suture divides the bone into
two, a condition which may persist throughout life. On either side of this suture,
about 3 cm. above the supraorbital margin, is a rounded elevation, the frontal emi-
nence (tuber frontale). These eminences vary in size in different individuals, are
occasionally unsymmetrical, and are especially prominent in young skulls; the sur-
face of the bone above them is smooth, and covered by the galea aponeurotica.
Below the frontal eminences, and separated from them by a shallow groove, are
two arched elevations, the superciliary arches; these are prominent medially, and
are joined to one another by a smooth elevation named the glabella. They are
larger in the male than in the female, and their degree of prominence depends
to some extent on the size of the frontal air sinuses;^ prominent ridges are, how-
ever, occasionally associated with small air sinuses. Beneath each superciliary
arch is a curved and prominent margin, the supraorbital margin, Avliich forms the
upper boundary of the base of the orbit, and separates the squama from the orbital
portion of the bone. The lateral part of this margin is sharp and prominent,
affording to the eye, in that situation, considerable protection from injury; the
medial part is rounded. At the junction of its medial and intermediate thirds is
1 Some confusion is occasioned to students commencing the study of anatomy by the name "sinus" having been
given to two different kinds of space connected with the skull. It may be as well, therefore, to state here that the
"sinuses" in the interior of the cranium which produce the grooves on the inner surfaces of the bones are venous
channels which convey the Ijlood from the brain, while the "sinuses" external to the cranial cavity (the frontal,
sphenoidal, ethmoidal, and maxillary) are hollow spaces in the bones themselves; they communicate with the nasal
javities and contain air.
136
OSTEOLOGY
a notch, sometimes converted into a foramen, the supraorbital notch or foramen,
which transmits the supraorbital vessels and nerve. A small aperture in the upper
part of the notch transmits a vein from the diploe to join the supraorbital vein.
The supraorbital margin ends laterally in the zygomatic process, which is strong
and prominent, and articulates with the zygomatic bone. Running upward and
backward from this process is a well-marked line, the temporal line, which divides
into the upper and lower temporal lines, continuous, in the articulated skull, with
the corresponding lines on the parietal bone. The area below and behind the tem-
poral line forms the anterior part of the temporal fossa, and gives origin to the
Temporalis muscle. Between the supraorbital margins the squama projects down-
ward to a level below that of the zygomatic processes; this portion is known as the
nasal part and presents a rough, uneven interval, the nasal notch, which articulates
Zygomatic
process
Frontal I spine
Fig. 134. — Frontal bone. Outer surface.
on either side of the middle line with the nasal bone, and laterally with the frontal
process of the maxilla and with the lacrimal. The term nasion is applied to the
middle of the frontonasal suture. From the center of the notch the nasal process
projects downward and forwon] beneath the nasal bones and frontal processes of
the maxillae, and supports the bridge of the nose. The nasal process ends below
in a sharp spine, and on either side of this is a small grooved surface which enters
into the formation of the roof of the corresponding nasal cavity. The spine forms
part of the septum of the nose, articulating in front with the crest of the nasal
bones and behind with the perpendicular plate of the ethmoid.
The internal siirface (Fig. 1.35) of the squama is concave and presents in the
upper part of the middle line a vertical groove, the sagittal sulcus, the edges of
which unite below to form a ridge, the frontal crest; the sulcus lodges the superior
sagittal sinus, while its margins and the crest afford attachment to the falx cerebri.
THE FRONTAL BONE
137
The crest ends below in a small notch which is converted into a foramen, the fora-
men cecum, by articulation with the ethmoid. This foramen varies in size in
different subjects, and is frequently impervious; when open, it transmits a vein
from the nose to the superior sagittal sinus. On either side of the middle line the
bone presents depressions for the convolutions of the brain, and numerous small
furrows for the anterior branches of the middle meningeal vessels. Se\eral small,
irregular fossae may also be seen on either side of the sagittal sulcus, for the
reception of the arachnoid granulations.
Orbital or Horizontal Part {pars orbitalis) .—This portion consists of two thin
triangular plates, the orbital plates, which form the vaults of the orbits, and are
separated from one another by a median gap, the ethmoidal notch.
Supraorbital
foramen
With maxilla
With nasal ^ I
With 'perpendicular plate of ethmoid
Frontal sinus
Under surface of nasal process
forming part of roof of nose
Fig. 135. — Frontal bone. Inner surface.
Surfaces. — The inferior surface (Fig. 135) of each orbital plate is smooth and
concave, and presents, laterally, under cover of the zygomatic process, a shallow
depression, the lacrimal fossa, for the lacrimal gland; near the nasal part is a depres-
sion, the fovea trochlearis, or occasionally a small trochlear spine, for the attach-
ment of the cartilaginous pulley of the Obliquus oculi superior. The superior
surface is convex, and marked by depressions for the convolutions of the frontal
lobes of the brain, and faint grooves for the meningeal branches of the ethmoidal
vessels.
The ethmoidal notch separates the two orbital plates; it is quadrilateral, and
filled, in the articulated skull, by the cribriform plate of the ethmoid. The margins
of the notch present several half-cells which, when united with corresponding
half-cells on the upper surface of the ethmoid, complete the ethmoidal air cells.
Two grooves cross these edges transversely; they are converted into the anterior
138
OSTEOLOGY
and posterior ethmoidal canals by the ethmoid, and open on the medial wall of the
orbit. The anterior canal transmits the nasociliary nerve and anterior ethmoidal
vessels, the posterior, the posterior ethmoidal nerve and vessels. In front of the
ethmoidal notch, on either side of the frontal spine, are the openings of the frontal .
air sinuses. These are two irregular cavities, which extend backward, upward,
and lateralward for a variable distance between the two tables of the skull; they
are separated from one another by a thin bony septum, which often deviates to
one or other side, Avith the result that the sinuses are rarelv svmmetrical. Absent
at birth, they are usually fairly well-developed between the seventh and eighth
years, but only reach their full size after puberty. They vary in size in different
persons, and are larger in men than in women. ^ They are lined by mucous mem-
brane, and each communicates with the corresponding nasal cavity by means of a
passage called the frontonasal duct.
Borders. — The border of the squama is thick, strongly serrated, bevelled at the
expense of the inner table above, where it rests upon the parietal bones, and at
the expense of the outer table on either side, where it receives the lateral pressure
of those bones; this border is continued below into a triangular, rough surface,
which articulates with the great wing of the sphenoid. The posterior borders of
the orbital plates are thin and serrated, and articulate with the small wings of the
sphenoid.
Structure. — ^The squama and the zj^gomatic processes are very thick, consisting of diploic
tissue contained between two compact lamina?; the diploic tissue is absent in the regions occupied
by the frontal air sinuses. The orbital portion is thin, translucent, and (Composed entirely of
compact bone; hence the faciUty with which instruments can penetrate the cranium through
this part of the orbit; when the frontal sinuses are exceptionally large they may extend backward
for a considerable distance into the orbital portion, which in such cases also consists of only two
tables.
Ossification (Fig. 136). — The frontal bone is ossified in membrane from tivo primary
centers, one for each half, which appear toward the end of the second month of fetal life, one
above each supraorbital margin. From each of these centers ossification extends upward to form
the corresponding half of the squama, and backward to form the orbital plate. The spine is
ossified from a pair of secondary centers,
on either side of the middle line; similar
centers appear in the nasal part and zygo-
matic processes. At birth the bone consists
of two pieces, separated by the frontal
suture, which is usually obUterated, except
at its lower part, by the eighth year, but
occasionally persists throughout Ufe. It is
generally maintained that the development
of the frontal sinuses begins at the end of
the first or beginning of the second year,
but Onodi's researches indicate that de-
velopment begins at birth. The sinuses
are of considerable size by the seventh or
eighth year, but do not attain their full
proportions until after puberty.
Articulations. — The frontal articulates
with twelve bones: the sphenoid, the eth-
moid, the two parietals, the two nasals, the
two maxillse, the two lacrimals, and the
two zygomatics.
.9,
quama
Nasal part
Zygomatic process
Spine
Fig. 136. — Frontal bone at birth.
The Temporal Bone (Os Temporale).
The temporal bones are situated at the sides and base of the skull. Each consists
of live parts, viz., the squama, the petrous, mastoid, and tympanic parts, and the
styloid process.
1 Aldren Turner (The Accessory Sinuses of the Nose, 1901) gives the following measurements for a sinus of average
size: height, 13€ inches; breadth, 1 inch; depth from before backward, 1 inch.
THE TEMPORAL BONE
139
The Squama {squama temporalis) .—The squama forms the anterior and upper
part of the bone, and is scale-hke, thin, and translucent.
Surfaces.— Its outer surface (Fig. 137) is smooth and convex; it affords attach-
ment to the TemporaHs muscle, and forms part of the temporal fossa; on its hinder
part is a vertical groove for the middle temporal artery. A curved line, the tem-
poral line, or supramastoid crest, runs backward and upward across its posterior
part; it serves for the attachment of the temporal fascia, and limits the origin
of the Temporalis muscle. The boundary between the squama and the mastoid
portion of the bone, as indicated by traces of the original suture, lies about 1 cm.
below this line. Projecting from the lower part of the squama is a long, arched
process, the zygomatic process. This process is at first directed lateralward, its
two surfaces looking upward and downward; it then appears as if twisted inward
Croove for middle
temporal artery
Parietal notch
Suprameatal
triangle
Occipitalis
Articular tubercle
Post-glenoid process
31andih ula r fossa
Petrotympanic fissure
Vaginal process
Styloglossus
Tympanic part
Stylohyoideus
Styloid process
Fia. 137. — Left temporal bone. Outer surface.
Occipital groove
upon itself, and runs forward, its surfaces now looking medial ward and lateralward.
The superior border is long, thin, and sharp, and serves for the attachment of the
temporal fascia; the inferior, short, thick, and arched, has attached to it some
fibers of the Masseter. The lateral surface is convex and subcutaneous ; the medial
is concave, and affords attachment to the Masseter. The anterior end is deeply
serrated and articulates with the zygomatic bone. The posterior end is connected
to the squama by two roots, the anterior and posterior roots. The posterior root, a
prolongation of the upper border, is strongly marked ; it runs backward above the
external acoustic meatus, and is continuous with the temporal line. The anterior
root, continuous with the lower border, is short but broad and strong; it is directed
medialward and ends in a rounded eminence, the articular tubercle (eminentia
articularis) . This tubercle forms the front boundary of the mandibular fossa,
140
OSTEOLOGY
and in the fresh state is covered with cartilage. In front of the articular tubercle
is a small triangular area which assists in forming the infratemporal fossa; this
area is separated from the outer surface of the squama by a ridge which is continu-
ous behind with the anterior root of the zygomatic process, and in front, in the
articulated skull, with the infratemporal crest on the great wing of the sphenoid.
Between the posterior wall of the external acoustic meatus and the posterior root
of the zygomatic process is the area called the suprameatal triangle (Macewen),
or mastoid fossa, through which an instrument may be pushed into the tympanic
antrum. At the junction of the anterior root with the zygomatic process is a pro-
jection for the attachment of the temporomandibular ligament; and behind the
anterior root is an oval depression, forming part of the mandibular fossa, for the
reception of the condyle of the mandible. The mandibular fossa {glenoid fossa)
ctal iofii
Parietal
nolch
Eminentia
nrcuata
I
Mastoid foramen
Aquoeductus vcstihuli
Aquoediictus cochlcce
Internal acoustic meatus
Fig. 138. — Left temporal bone. Inner surface.
is bounded, in front, by the articular tubercle; behind, by the tympanic part of
the bone, which separates it from the external acoustic meatus; it is divided into
two parts by a narrow slit, the petrotympanic fissure {Glaserian fissure). The
anterior part, formed by the squama, is smooth, covered in the fresh state with
cartilage, and articulates with the condyle of the mandible. Behind this part
of the fossa is a small conical eminence; this is the representative of a prominent
tubercle which, in some mammals, descends behind the condyle of the mandible,
and prevents its backward displacement. The posterior part of the mandibular
fossa, formed by the tympanic part of the bone, is non-articular, and sometimes
lodges a portion of the parotid gland. The petrotympanic fissure leads into the
middle ear or tympanic cavity; it lodges the anterior process of the malleus, and
transmits the tympanic branch of the internal maxillary artery. The chorda
1
THE TEMPORAL BONE
141
tympani nerve passes through a canal {canal of Huguier), separated from the an-
terior edge of the petrotympanic fissure by a thin scale of bone and situated on
the lateral side of the auditory tube, in the retiring angle between the squama
and the petrous portion of the temporal.
The internal surface of the squama (Fig. 138) is concave; it presents depressions
corresponding to the convolutions of the temporal lobe of the brain, and grooves
for the branches of the middle meningeal vessels.
Borders.— The superior border is thin, and bevelled at the expense of the internal
table, so as to overlap the squamous border of the parietal bone, forming with
it the squamosal suture. Posteriorly, the superior border forms an angle, the
parietal notch, with the mastoid portion of the bone. The antero-inferior border
is thick, serrated, and bevelled at the expense of the inner table above and of
the outer below, for articulation with the great wing of the sphenoid.
Mastoid Portion {pars mastoidea) .—The mastoid portion forms the posterior
part of the bone.
Tympanic antrum
Tegmen tympani
Prominence of lateral semicircular canal
Prominence of facial canal
Fenestra vestihuli
Bristle in semicanal for Terisor tympani
Septum canal is muscvlotubarii
Bristle in hiatus of facial canal
Carotid canal
Bony part of auditory tube
Promontory
Bristle in pyramid
Fenestra cochleoe
Sulctis tympanicus
Mastoid cells ^^^^^^^ *** stylomastoid foramen
Fig. 139. — Coronal section of right temporal bone.
Surfaces. — Its outer surface (Fig. 137) is rough, and gives attachment to the
Occipitalis and Auricularis posterior. It is perforated by numerous foramina; one
of these, of large size, situated near the posterior border, is termed the mastoid
foramen; it transmits a vein to the transverse sinus and a small branch of the occipi-
tal artery to the dura mater. The position and size of this foramen are very
variable; it is not always present; sometimes it is situated in the occipital bone,
or in the suture between the temporal and the occipital. The mastoid portion is
continued below into a conical projection, the mastoid process, the size and form
of which vary somewhat; it is larger in the male than in the female. This process
serves for the attachment of the Sternocleidomastoideus, Splenius capitis, and
Longissimus capitis. On the medial side of the process is a deep groove, the
mastoid notch {digastric fossa), for the attachment of the Digastricus; medial to
this is a shallow furrow, the occipital groove, which lodges the occipital artery.
142 OSTEOLOGY
The inner surface of the mastoid portion presents a deep, curved groove, the
sigmoid sulcus, which lodges part of the transverse sinus; in it may be seen the
opening of the mastoid foramen. The groove for the transverse sinus is separated
from the innermost of the mastoid air cells by a very thin lamina of bone, and even
this may be partly deficient. .
Borders. — The superior border of the mastoid portion is broad and serrated, for
articulation with the mastoid angle of the parietal. The posterior border, also
serrated, articulates with the inferior border of the occipital between the lateral
angle and jugular process. Anteriorly the mastoid portion is fused with the
descending process of the squama above; below it enters into the formation of
the external acoustic meatus and the tympanic cavity.
A section of the mastoid process (Fig. 139) shows it to be hollowed out into a
number of spaces, the mastoid cells, which exliibit the greatest possible variety
as to their size and number. At the upper and front part of the process they are
large and irregular and contain air, but toward the lower part they diminish in
size, while those at the apex of the process are frequently quite small and contain
marrow; occasionally they are entirely absent, and the mastoid is then solid
throughout. In addition to these a large irregular cavity is situated at the upper
and front part of the bone. It is called the tympanic antrum, and must be distin-
guished from the mastoid cells, though it communicates with them. Like the mas-
toid cells it is filled with air and lined by a prolongation of the mucous membrane
of the tympanic cavity, with which it communicates. The tympanic antrum is
bounded above by a thin plate of bone, the tegmen tympani, which separates it
from the middle fossa of the base of the skull; below by the mastoid process; later-
ally by the squama just below the temporal line, and medially by the lateral semi-
circular canal of the internal ear which projects into its cavity. It opens in front
into that portion of the tympanic cavity which is known as the attic or epitympanic
recess. The tympanic antrum is a cavity of some considerable size at the time of
birth; the mastoid air cells may be regarded as diverticula from the antrum,
and begin to appear at or before birth; by the fifth year they are well-marked,
but their development is not completed until toward puberty.
Petrous Portion {pars pefrosa [pyramis]). — The petrous portion or pyramid is
pyramidal and is wedged in at the base of the skull between the sphenoid and
occipital. Directed medialward, forward, and a little upward, it presents for
examination a base, an apex, three surfaces, and three angles, and contains, in
its interior, the essential parts of the organ of hearing.
Base. — The base is fused with the internal surfaces of the squama and mastoid
portion.
Apex. — The apex, rough and uneven, is received into the angular interval between
the posterior border of the great wing of the sphenoid and the basilar part of the
occipital; it presents the anterior or internal orifice of the carotid canal, and
forms the postero-lateral boundary of the foramen lacerum.
.Siu-faces. — The anterior surface forms the posterior part of the middle fossa of
the base of the skull, and is continuous with the imier surface of the squamous
portion, to which it is united by the petrosquamous suture, remains of which are
distinct even at a late period of life. It is marked by depressions for the convolu-
tions of the brain, and presents six points for examination: (1) near the center,
an eminence {eminentia arcuata) which indicates the situation of the superior semi-
circular canal; (2) in front of and a little lateral to this eminence, a depression indi-
cating the position of the tympanic cavity : here the layer of bone which separates
the tympanic from the cranial cavity is extremely thin, and is known as the
tegmen tympani; (3) a shallow groove, sometimes double, leading lateralward and
backward to an oblique opening, the hiatus of the facial canal, for the passage of
the greater superficial petrosal nerve and the petrosal branch of the middle men-
THE TEMPORAL BONE
143
ingeal artery; (4) lateral to the hiatus, a smaller opening, occasionally seen, for
the passage of the lesser superficial petrosal nerve; (5) near the apex of the bone,
the termination of the carotid canal, the wall of which in this situation is deficient
in front; (6) above this canal the shallow trigeminal impression for the reception
of the semilunar ganglion.
The posterior surface (Fig. 1.38) forms the front part of the posterior fossa of
the base of the skull, and is continuous with the inner surface of the mastoid
portion. Near the center is a large orifice, the internal acoustic meatus, the size of
which varies considerably; its margins are smooth and rounded, and it leads into
a short canal, about 1 cm. in length, which runs lateralward. It transmits the
facial and acoustic nerves and the internal auditory branch of the basilar artery.
The lateral end of the canal is closed by a vertical plate, which is divided by a
horizontal crest, the crista falciformis, into two unequal portions (Fig. 140). Each
portion is further subdivided by a vertical ridge into an anterior and a posterior
part. In the portion beneath the crista falciformis are three sets of foramina;
one group, just below the posterior part of
the crest, situated in the area cribrosa media, ■> '
consists of several small openings for the
nerves to the saccule; below and behind this
area is the foramen singulare, or opening for
the nerve to the posterior semicircular duct;
in front of and below the first is the tractus
spiralis foraminosus, consisting of a number of
small spirally arranged openings, which encircle
the canalis centralis cochleae; these openings
together with this central canal transmit the
nerves to the cochlea. The portion above
the crista falciformis presents behind, the
area •cribrosa superior, pierced by a series of
small openings, for the passage of the nerves
to the utricle and the superior and lateral
semicircular ducts, and, in front, the area
faciaiis, with one large opening, the com-
mencement of the canal for the facial nerve
(aquseductus FaUopii). Behind the internal
acoustic meatus is a small slit almost hidden
by a thin plate of bone, leading to a canal,
the aquaeductus vestibuli, which transmits the
ductus endolymphaticus together with a small artery and vein. Above and
between these two openings is an irregular depression which lodges a process of
the dura mater and transmits a small vein; in the infant this depression is repre-
sented by a large fossa, the subarcuate fossa, which extends backward as a blind
tunnel under the superior semicircular canal.
The inferior surface (Fig. 141) is rough and irregular, and forms part of the
exterior of the base of the skull. It presents eleven points for examination: (1)
near the apex is a rough surface, quadrilateral in form, which serves partly for the
attachment of the Levator veli palatini and the cartilaginous portion of the audi-
tory tube, and partly for connection with the basilar part of the occipital bone
through the intervention of some dense fibrous tissue; (2) behind this is the large
circular aperture of the carotid canal, which ascends at first vertically, and then,
making a bend, runs horizontally forward and medialward; it transmits into the
cranium the internal carotid artery, and the carotid plexus of nerves; (3) medial
to the opening for the carotid canal and close to its posterior border, in front of the
jugular fossa, is a triangular depression; at the apex of this is a small opening, the
Fig. 140. — Diagrammatic view of the fundus
of the right internal acoustic meatus. (Testut.)
1. Crista falciformis. 2. Area facialis, with (2')
internal opening of the facial canal. 3. Ridge
separating the area facialis from the area crib-
rosa superior. 4. Area cribrosa superior, with
(4') openings for nerve filaments. 5. Anterior
inferior cribriform area, with (o') the tractus
spiralis foraminosus, and (5") the canalis cen-
tralis of the cochlea. 6. Ridge separating the
tractus spiralis foraminosus from the area crib-
rosa media. 7. Area cribrosa media, with (7')
orifices for nerves to saccule. 8. Foramen
singulare.
144
OSTEOLOGY
aquaeductus cochleae, which lodges a tubular prolongation of the dura mater establish-
ing a communication between the peril ^inphatic space and the subarachnoid space,
and transmits a vein from the cochlea to join the internal jugular; (4) behind these
openings is a deep depression, the jugular fossa, of variable depth and size in different
skulls; it lodges the bulb of the internal jugular vein; (5) in the bony ridge dividing
the carotid canal from the jugular fossa is the small inferior tympanic canaliculus
for the passage of the tympanic branch of the glossopharyngeal nerve; (6) in the
lateral part of the jugular fossa is the mastoid canaliculus for the entrance of the
auricular branch of the vagus nerve; (7) behind the jugular fossa is a quadrilateral
area, the jugular surface, covered with cartilage in the fresh state, and articulating
wuth the jugular process of the occipital bone; (8) extending backward from the
carotid canal is the vaginal process, a sheath-like plate of bone, which divides
Semicanals for
auditory
tube and
Tensor
tympani
Lev. veli palatini
Rough quadrilateral surface
Opening of carotid canal
Inferior tympanic canaliculus —
Aqvcpduchis cochlece
3Iastoid canaliculus
Jugular fossa
Vaginal process
Styloid process
Stylomastoid foramen
Jugidar surface
Tympanomastoid fissure
Slylopharyngeus
Fig. 141. — Left temporal bone. Inferior surface.
behind into two laminae; the lateral lamina is continuous with the tympanic part
of the bone, the medial with the lateral margin of the jugular surface; (9) between
.these laminae is the styloid process, a sharp spine, about 2.5 cm. in length; (10)
between the styloid and mastoid processes is the stylomastoid foramen; it is the
termination of the facial canal, and transmits the facial nerve and stylomastoid
artery; (11) situated between the tympanic portion and the mastoid process is the
tympanomastoid fissure, for the exit of the auricular branch of the vagus nerve.
Angles. — The superior angle, the longest, is grooved for the superior petrosal
sinus, and gives attachment to the tentorium cerebelli; at its medial extremity
is a notch, in which the trigeminal nerve lies. The posterior angle is intermediate
in length between the superior and the anterior. Its medial half is marked by
a sulcus, which forms, with a corresponding sulcus on the occipital bone, the
channel for the inferior petrosal sinus. Its lateral half presents an excavation
— the jugular fossa — which, with the jugular notch on the occipital, forms the
THE TEMPORAL BONE 145
jugular foramen ; an eminence occasionally projects from the center of the fossa,
and divides the foramen into two. The anterior angle is divided into two parts
—a lateral joined to the squama by a suture (petnmiimmotts), the remains of which
are more or less distinct; a medial, free, which articulates with the spinous process
of the sphenoid.
At the angle of junction of the petrous part and the squama are two canals,
one above the other, and separated by a thin plate of bone, the septum canalis
musculotubarii (processus cochleariformis); both canals lead into the tympanic
cavity. The upper one (semicanalis m. tensoris tympani) transmits the Tensor
tympani, the lower one {semicanalis tuhco anditivw) forms the bony part of the
auditory tube.
The tympanic cavity, auditory ossicles, and internal ear, are described with
the organ of hearing.
Tympanic Part (pars tympanica). — The tympanic part is a curved plate of bone
lying below the squama and in front of the mastoid process.
Surfaces. — Its postero-superior surface is concave, and forms the anterior wall,
the floor, and part of the posterior wall of the bony external acoustic meatus.
Medially, it presents a narrow furrow, the tympanic sulcus, for the attachment
of the tympanic membrane. Its antero-inferior surface is quadrilateral and slightly
concave; it constitutes the posterior boundary of the mandibular fossa, and is
in contact with the retromandibular part of the parotid gland.
Borders. — Its lateral border is free and rough, and gives attachment to the car-
tilaginous part of the external acoustic meatus. Internally, the tympanic part
is fused with the petrous portion, and appears in the retreating angle between
it and the squama, where it lies below and lateral to the orifice of the auditory
tube. Posteriorly, it blends with the squama and mastoid part, and forms the
anterior boundary of the tympanomastoid fissure. Its upper border fuses laterally
with the back of the postglenoid process, while medially it bounds the petro-
tympanic fissure. The medial part of the lower border is thin and sharp; its lateral
part splits to enclose the root of the styloid process, and is therefore named the
vaginal process. The central portion of the tympanic part is thin, and in a consid-
erable percentage of skulls is perforated by a hole, the foramen of Huschke.
The external acoustic meatus is nearly 2 cm. long and is directed inward and
slightly forward: at the same time it forms a slight curve, so that the floor of the
canal is convex upward. In sagittal section it presents an oval or elliptical shape
with the long axis directed downward and slightly backward. Its anterior wall
and floor and the lower part of its posterior wall are formed by the tympanic
part; the roof and upper part of the posterior wall by the squama. Its inner
end is closed, in the recent state, by the tympanic membrane; the upper limit
of its outer orifice is formed by the posterior root of the zygomatic process, imme-
diately below which there is sometimes seen a small spine, the suprameatal spine,
situated at the upper and posterior part of the orifice.
Styloid Process (processus styloideus) . — The styloid process is slender, pointed,
and of varying length; it projects downward and forward, from the under surface
of the temporal bone. Its proximal part (tympanohyal) is ensheathed by the
vaginal process of the tympanic portion, while its distal part (stylohyal) gives
attachment to the stylohyoid and stylomandibular ligaments, and to the Stylo-
glossus, Stylohyoideus, and Stylopharyngeus muscles. The stylohyoid ligament
extends from the apex of the process to the lesser cornu of the hyoid bone, and
in some instances is partially, in others completely, ossified.
Structure.^ — The structure of the squama is like that of the other cranial bones: the mastoid
portion is spongy, and the petrous portion dense and hard.
Ossification. — The temporal bone is ossified from eight centers, exclusive of those for the internal
ear and the tympanic ossicles, viz., one for the squama including the zygomatic process, one for
10
146
OSTEOLOGY
the tympanic part, four for the patrous and mastoid parts, and two for the styloid process. Just
before the close of fetal life (Fig. 142) the temporal bone consists of three principal parts: 1.
The squama is ossified in membrane from a single nucleus, which appears near the root of the
zygomatic process about the second month. 2. The petromastoid part is developed from four
centers, which make their appearance in the cartilaginous ear capsule about the fifth or sixth
month. One (prodtic) appears in the neighborhood of the eminentia arcuata, spreads in front
and above the internal acoustic meatus and extends to the apex of the bone; it forms part of the
Septum canalis musculotubarii .
Fenestra vestibuli
Tympanic antrum,
Sulcus tympanicus
Bristle in facial
canal
Lateral wall of
tympanic antrum
Fig. 142. — The three principal parts of the tempora bone at birth. 1. Outer surface of petromastoid part.
2. Outer surface of tympanic ring. 3. Inner surface of squama.
cochlea, vestibule, superior semicircular canal, and medial wall of the tympanic cavity. A second
{opisthotic) appears at the promontory on the medial wall of the tympanic cavity and surrounds
the fenestra cochleae; it forms the floor of the tympanic cavity and vestibule, surrounds the carotid
canal, invests the lateral and lower part of the cochlea, and spreads medially below the internal
acoustic meatus. A third (pterotic) roofs in the tympanic cavity and antrum; while the fourth
Squama
Squama
Petrosquamous
suture
Petrosquamous suture
Eminentia arcuata
Tympanic ring
Petromastoid portion
Fig. 143. — Temporal bone at birth.
Outer aspect.
Fig. 144.
Fossa subarcuata
Internal acoustic meatus
-Temporal bone at birth. Inner
aspect.
(epiotic) appears near the posterior semicircular canal and extends to form the mastoid process
(Vrolik), 3. The tympanic ring is an incomplete circle, in the concavity of which is a groove,
the tympanic sulcus, for the attachment of the circumference of the tympanic membrane. This
ring expands to form the tympanic part, and is ossified in membrane from a single center which
appears about the third month. The styloid process is developed from the proximal part of the
cartilage of the second branchial or hyoid arch by two centers: one for the proximal part, the
tympanohyal, appears before birth; the other, comprising the rest of the process, is named the
THE SPHENOID BONE 147
slylohyal, and does not appear until after birth. The tympanic ring unites with the squama
shortly before birth; the petromastoid part and squama join during the first year, and the tym-
panohyal portion of the styloid process about the same time (Figs. 143, 144). The stylohyal
does not unite with the rest of the bone until after puberty, and in some skulls never at all.
The chief subsequent changes in the temporal bone apart from increase in size are: (1) The
tympanic ring extends outward and backward to form the tympanic part. This extension does
not, however, take place at an equal rate all around the circumference of the ring, but occurs most
rapidly on its anterior and posterior portions, and these outgrowths meet and blend, and thus,
for a time, there exists in the floor of the meatus a foramen, the foramen of Huschke; this foramen
is usually closed about the fifth year, but may persist throughout Ufe. (2) The mandibular fossa
is at first extremely shallow, and looks lateralward as well as downward; it becomes deeper and
is ultimately directed downward. Its change in direction is accounted for as follows. The part
of the squama which forms the fossa lies at first below the level of the zygomatic process. As,
however, the base of the skull increases in width, this lower part of the squama is directed hori-
zontally inward to contribute to the middle fossa of the skull, and its surfaces therefore come
to look upward and downward; the attached portion of the zygomatic process also becomes
everted, and projects like a shelf at right angles to the squama. (3) The mastoid portion is at
first quite flat, and the stylomastoid foramen and rudimentary styloid process lie immediately
behind the tympanic ring. With the development of the air cells the outer part of the mastoid
portion grows downward and forward to form the mastoid process, and the styloid process and
stylomastoid foramen now come to lie on the under surface. The descent of the foramen is
necessarily accompanied by a corresponding lengthening of the facial canal. (4) The downward
and forward growth of the mastoid process also pushes forward the tympanic part, so that the
portion of it which formed the original floor of the meatus and contained the foramen of Huschke
is ultimately found in the anterior wall. (5) The fossa subarcuata becomes filled up and almost
obliterated.
Articulations.— The temporal articulates with five bones : occipital, parietal, sphenoid, mandible
and zygomatic.
The Sphenoid Bone (Os Sphenoidale).
The sphenoid bone is situated at the base of the skull in front of the temporals
and basilar part of the occipital. It somewhat resembles a bat with its wings
extended, and is divided into a median portion or body, two great and two small
wings extending outward from the sides of the body, and two pterygoid processes
which project from it below.
Body {corpus si>henoidale) . — The body, more or less cubical in shape, is hollowed
out in its interior to form two large cavities, the sphenoidal air sinuses, which are
separated from each other by a septum.
Surfaces. — The superior surface of the body (Fig. 145) presents in front a promi-
nent spine, the ethmoidal spine, for articulation with the cribriform plate of the
ethmoid; behind this is a smooth surface slightly raised in the middle line, and
grooved on either side for the olfactory lobes of the brain. This surface is bounded
behind by a ridge, which forms the anterior border of a narrow, transverse groove,
the chiasmatic groove {optic groove), above and behind which lies the optic chiasma;
the groove ends on either side in the optic foramen, which transmits the optic
nerve and ophthalmic artery into the orbital cavity. Behind the chiasmatic
groove is an elevation, the tuberculum sellae; and still more posteriorly, a deep
depression, the sella turcica, the deepest part of which lodges the hypophysis
cerebri and is known as the fossa hypophyseos. The anterior boundary of the
sella turcica is completed by two small eminences, one on either side, called the
middle clinoid processes, while the posterior boundary is formed by a square-
shaped plate of bone, the dorsum sellae, ending at its superior angles in two tubercles,
the posterior clinoid processes, the size and form of which vary considerably in
different individuals. The posterior clinoid processes deepen the sella turcica,
and give attachment to the tentorium cerebelli. On either side of the dorsum
sells is a notch for the passage of the abducent nerve, and below the notch a sharp
process, the petrosal process, which articulates with the apex of the petrous portion
of the temporal bone, and forms the medial boundary of the foramen lacerum.
148
OSTEOLOGY
Behind the dorsum sellse is a shallow depression, the clivus, which slopes obliquely
backward, and is continuous with the groove on the basilar portion of the occipital
bone; it supports the upper part of the pons.
Middle Clinoid process
Posterior Clinoid process
Ethmoidal
spine
Groove for
olfactoni
Optic foramen
Superior orbital
fissu re
Foramen rotund um
Foramen Vesalii
Foramen orale
Foramen spinonum
Spina annularis
palatine
Fig. 14o. — Sphenoid bone. Upper surface.
The lateral surfaces of the body are united with the great wings and the medial
pterygoid plates. Above the attachment of each great wing is a broad groove,
curved something like the italic letter /; it lodges the internal carotid artery and
the cavernous sinus, and is named the carotid groove. Along the posterior part
Infratemporal
crext
Tensor vel
palatini
Medial pteryrjo
Fig. 14G. — Sphenoid bone. .Vnterior and inferior surfaces.
of the lateral margin of this groove, in the angle between the body and great wing,
is a ridge of bone, called the lingula.
The posterior surface, quadrilateral in form (Fig. 147), is joined, during infancy
and adolescence, to the basilar part of the occipital bone by a plate of cartilage.
THE SPHENOID BONE
149
Between the eighteenth and twenty-fifth years this becomes ossified, ossification
commencing above and extending downward.
The anterior surface of the body (Fig. 14()) presents, in the middle line, a vertical
crest, the sphenoidal crest, which articulates with the perpendicular plate of the
ethmoid, and forms part of the septum of the nose. On either side of the crest
is an irregular opening leading into the corresponding sphenoidal air sinus. These
sinuses are two large, irregular cavities hollowed out of the interior of the body
of the bone, and separated from one another by a bony septum, which is commonly
bent to one or the other side. They vary considerably in form and size,^ are
seldom symmetrical, and are often partially subdivided by irregular bony lamina.
Occasionally, they extend into the basilar part of the occipital nearly as far as the
forameri magnum. They begin to be developed before birth, and are of a consid-
erable size by the age of six. They are partially closed, in front and below, by two
thin, curved plates of bone, the sphenoidal conchse (see page ]r)2), leaving in the
articulated skull a round opening at the upper part of each sinus by which it com-
Anlerior clinoid process
Posterior clinoid process j Jsfoich jor abducent
oramen rolundum
f f\ «'i<fcw • Spina anguiaris
Scaphoid fossa' IMUr^^ / / /Ml ( ^^terygoid canal
Pterygoid fossa z:jMS^'m I I 1 111 -^^^ Lateral pteryuoid lamina
Medial pterygoid lamina
Hamulus
Rostrum
FiQ. 147. — Sphenoid bone. Upper and posterior surfaces.
municates with the upper and back part of the nasal cavity and occasionally with
the posterior ethmoidal air cells. The lateral margin of the anterior surface is
serrated, and articulates with the lamina papyracea of the ethmoid, completing
the posterior ethmoidal cells; the lower margin articulates with the orbital process
of the palatine bone, and the upper with the orbital plate of the frontal bone.
The inferior surface presents, in the middle line, a triangular spine, the sphenoidal
rostrum, which is continuous with the sphenoidal crest on the anterior surface,
and is received in a deep fissure between the ahe of the vomer. On either side of
the rostrum is a projecting lamina, the vaginal process, directed medialward from
the base of the medial pterygoid plate, with which it will be described.
The Great Wings (alee inagncp). — The great wings, or ali-sphenoids, are two
strong processes of bone, which arise from the sides of the body, and are curved
upward, lateralward, and backward; the posterior part of each projects as a tri-
angular process which fits into the angle between the squama and the petrous
' Aldren Turner {op. cit.) gives the following a.-) their average measurements: vertical height, '/s inch: antero-posterior
depth, '/s inch; transverse breadth, ?^ inch.
150 OSTEOLOGY
portion of the temporal and presents at its apex a downwardly directed process,
the spina angularis {sphenoidal spine).
Surfaces. — ^The superior or cerebral surface of each great wing (Fig. 145) forms
part of the middle fossa of the skull; it is deeply concave, and presents depressions
for the convolutions of the temporal lobe of the brain. At its anterior and medial
part is a circular aperture, the foramen rotiindum, for the transmission of the maxil-
lary nerve. Behind and lateral to this is the foramen ovale, for the transmission
of the mandibular nerve, the accessory meningeal artery, and sometimes the
lesser superficial petrosal nerve. ^ Medial to the foramen ovale, a small aperture,
the foramen Vesalii, may occasionally be seen opposite the root of the pterygoid
process; it opens below near the scaphoid fossa, and transmits a small vein from
the cavernous sinus. Lastly, in the posterior angle, near to and in front of the spine,
is a short canal, sometimes double, the foramen spinosum, which transmits the
middle meningeal vessels and a recurrent branch from the mandibular nerve.
The lateral surface (Fig. 146) is convex, and divided by a transverse ridge, the
infratemporal crest, into two portions. The superior or temporal portion, convex
from above downward, concave from before backward, forms a part of the tem-
poral fossa, and gives attachment to the Temporalis; the inferior or infratemporal,
smaller in size and concave, enters into the formation of the infratemporal fossa,
and, together with the infratemporal crest, affords attachment to the Pterygoideus
externus. It is pierced by the foramen ovale and foramen spinosum, and at its
posterior part is the spina angularis, which is frequently grooved on its medial
surface for the chorda tympani nerve. To the spina angularis are attached the
sphenomandibular ligament and the Tensor veli palatini. Medial to the anterior
extremity of the infratemporal crest is a triangular process which serves to increase
the attachment of the Pterygoideus externus; extending downward and medialward
from this process on to the front part of the lateral pterygoid plate is a ridge which
forms the anterior limit of the infratemporal surface, and, in the articulated skull,
the posterior boundary of the pterygomaxillary fissure.
The orbital surface of the great wing (Fig. 146), smooth, and quadrilateral in
shape, is directed forward and medialward and forms the posterior part of the
lateral wall of the orbit. Its upper serrated edge articulates with the orbital plate
of the frontal. Its inferior rounded border forms the postero-lateral boundary of
the inferior orbital fissure. Its medial sharp margin forms the lower boundary
of the superior orbital fissure and has projecting from about its center a little
tubercle which gives attachment to the inferior head of the Rectus lateralis oculi;
at the upper part of this margin is a notch for the transmission of a recurrent
branch of the lacrimal artery. Its lateral margin is serrated and articulates with
the zygomatic bone. Below the medial end of the superior orbital fissure is a
grooved surface, which forms the posterior wall of the pterygopalatine fossa,
and is pierced by the foramen rotundum.
Margin (Fig. 145). — Commencing from behind, that portion of the circum-
•ference of the great wing which extends from the body to the spine is irregular.
Its medial half forms the anterior boundary of the foramen lacerum, and presents
the posterior aperture of the pterygoid canal for the passage of the correspond-
ing nerve and artery. Its lateral half articulates, by njeans of a synchondrosis,
with the petrous portion of the temporal, and between the two bones on the
under surface of the skull, is a furrow, the sulcus tubse, for the lodgement of the
cartilaginous part of the auditory tube. In front of the spine the circumference
presents a concave, serrated edge, bevelled at the expense of the inner table below,
and of the outer table above, for articulation with the temporal squama. At
the tip of the great wing is a triangular portion, bevelled at the expense of the
* The lesser superficial petrosal nerve sometimes passes through a special canal (canaliculus innominatus of Arnold)
situated medial to the foramen spinosum.
THE SPHENOID BONE 151
internal surface, for articulation with the sphenoidal angle of the parietal bone;
this region is named the pterion. Medial to this is a triangular, serrated surface,
for articulation with the frontal bone; this surface is continuous medially with
the sharp edge, which forms the lower boundary of the superior orbital fissure,
and laterally with the serrated margin for articulation with the zygomatic bone.
The Small Wings (a/cp parvce). —The small wings or orbito-sphenoids are two
thin triangular plates, which arise from the upper and anterior parts of the body,
and, projecting lateralward, end in sharp points (Fig. 145).
Surfaces.— The superior surface of each is flat, and supports part of the frontal
lobe of the brain. The inferior surface forms the back part of the roof of the orbit,
and the upper boundary of the superior orbital fissure. This fissure is of a triangular
form, and leads from the cavity of the cranium into that of the orbit: it is bounded
mediaUy by the body; above, by the small wing; beloiv, by the medial margin of
the orbital surface of the great wing; and is completed laterally by the frontal
bone. It transmits the oculomotor, trochlear, and abducent nerves, the three
branches of the ophthalmic division of the trigeminal nerve, some filaments from
the cavernous plexus of the sympathetic, the orbital branch of the middle menin-
^ geal artery, a recurrent branch from the lacrimal artery to the dura mater, and the
* ophthalmic vein.
Borders. — The anterior border is serrated for articulation with the frontal bone.
The posterior border, smooth and rounded, is received into the lateral fissure of
the brain; the medial end of this border forms the anterior clinoid process, which
gives attachment to the tentorium cerebelli; it is sometimes joined to the middle
clinoid process by a spicule of bone, and when this occurs the termination of the
groove for the internal carotid artery is converted into a foramen (carotico-clinoid).
The small wing is connected to the body by two roots, the upper thin and flat,
the lower thick and triangular; between the two roots is the optic foramen, for the
transmission of the optic nerve and ophthalmic artery.
Pterygoid Processes (processus pterygoidei). — The pterygoid processes, one on
either side, descend perpendicularly from the regions where the body and great
wings unite. Each process consists of a medial and a lateral plate, the upper parts
of which are fused anteriorly; a vertical sulcus, the pterygopalatine groove, descends
on the front of the line of fusion. The plates are separated below by an angular
cleft, the pterygoid fissure, the margins of which are rough for articulation with
the pyramidal process of the palatine bone. The two plates diverge behind and
enclose between them a V-shaped fossa, the pterygoid fossa, which contains the
Pterygoideus internus and Tensor veli palatini. Above this fossa is a small, oval,
shallow depression, the scaphoid fossa, which gives origin to the Tensor veli palatini.
The anterior surface of the pterygoid process is broad and triangular near its
root, where it forms the posterior wall of the pterygopalatine fossa and presents
the anterior orifice of the pterygoid canal.
Lateral Pterygoid Plate. — The lateral pterygoid plate is broad, thin, and everted;
its lateral surface forms part of the medial wall of the infratemporal fossa, and
gives attachment to the Pterygoideus externus; its medial surface forms part of
the pterygoid fossa, and gives attachment to the Pterygoideus internus.
Medial Pterygoid Plate. — The medial pterygoid plate is narrower and longer
than the lateral ; it curves lateralward at its lower extremity into a hook-like pro-
cess, the pterygoid hamulus, around which the tendon of the Tensor veli palatini
glides. The lateral surface of this plate forms part of the pterygoid fossa, the
medial surface constitutes the lateral boundary of the choana or posterior aperture
of the corresponding nasal cavity. Superiorly the medial plate is prolonged on to
the under surface of the body as a thin lamina, named the vaginal process, which
articulates in front with the sphenoidal process of the palatine and behind this
with the ala of the vomer. The angular prominence between the posterior margin
152
OSTEOLOGY
of the vaginal process and the medial border of the scaphoid fossa is named the
pterygoid tubercle, and immediately above this is the posterior opening of the
pterygoid canal. On the under surface of the vaginal process is a furrow, which
is converted into a canal by the sphenoidal process of the palatine bone, for the
transmission of the pharyngeal branch of the internal maxillary artery and the
pharyngeal nerve from the sphenopalatine ganglion. The pharyngeal aponeurosis
is attached to the entire length of the posterior edge of the medial plate, and the
Constrictor pharyngis superior takes origin from its lower third. Projecting
backward from near the middle of the posterior edge of this plate is an angular
process, the processus tubarius, which supports the pharyngeal end of the auditory
tube. The anterior margin of the plate articulates with the posterior border of
the vertical part of the palatine bone.
The Sphenoidal Conchse {conchce sphenoidales; sphenoidal iurbiiiated processes).
— The sphenoidal concha^ are two thin, curved plates, situated at the anterior
and lower part of the body of the sphenoid. An aperture of variable size exists
in the anterior wall of each, and through this the sphenoidal sinus opens into the
nasal cavity. Each is irregular in form, and tapers to a point behind, being broader
and thinner in front. Its upper surface is concave, and looks toward the cavity
of the sinus; its under surface is convex, and forms part of the roof of the corre-
sponding nasal cavity. Each bone articulates in front with the ethmoid, laterally
with the palatine; its pointed posterior extremity is placed above the vomer,
and is received between the root of the pterygoid process laterally and the rostrum
of the sphenoid medially. A small portion of the sphenoidal concha sometimes
enters into the formation of the medial wall of the orbit, between the lamina
papyracea of the ethmoid in front, the orbital plate of the palatine below, and the
frontal bone above.
Ossification. — Until the seventh or eighth month of fetal life the body of the sphenoid consists
of two parts, viz., one in front of the tubercuhim scUae, the prespheuoid, with which the small
wings are continuous; the other, comprising the sella turcica and dorsum sella^, the postsphenoid,
with which are associated the great
wings, and pterygoid processes. The
greater part of the bone is ossified in
cartilage. There are fourteen centers
in all, six for the presphenoiil and eight
for the postsphenoid.
Presphenoid. — About the ninth week
of fetal life an ossific center appears for
each of the small wings (orbit osphenoids)
just lateral to the oi)tic foramen; shortly
afterward two nuclei appear in the pre-
sphenoid part of the body. The sphe-
noidal concha^ are each developed from
a center which makes its appearance about the fifth month ;i at birth they consist of small
triangular lamina^, and it is not until the third year that they become hollowed out and cone-
shaped; about the fourth year they fuse with the labyrinths of tlie ethmoid, and between the
ninth and twelfth years they unite with the sphenoid.
Postsphenoid. — The first ossific nuclei are those for the great wings (ali-sphenoids)=. ( )ne makes
its appearance in each wing between the foramen rotundum and foramen ovale about the eighth
week. The orbital plate and that part of the sjihenoid which is found in the temporal fossa, as
well as the lateral pterygoid plate, are ossified in membrane (Fawcett)^ Soon after, the centers
for the postsphenoid part of the body appear, one on either side of the sella turcica, and become
blended together about the middle of fetal life. Each medial pterygoid plate (.with the exception
of its hamulus) is ossified in membrane, and its center probably appears about the ninth or tenth
week; the hamulus becomes chondrified during the third month, and almost at once imdergoes
Fig. 148. — Sphenoid bone at birth. Posterior aspect.
' According to Cleland, each sphenoidal concha is ossified from four centers.
2 Mall. Am. .lour. Anat., 1906, states that the pterjgoid center appears first in an embryo fifty-seven days old.
s Journal of Anatomy and Physiology, 1910, vol. xliv.
THE ETHMOID BONE
153
ossification (Fawcett). The medial joins the lateral pterygoid plate about the sixth month.
About the fourth month a center appears for each lingula and speedily joins the rest of the bone.
The presphenoid is united to the postsphenoid about the eighth month, and at birth the bone
IS in three pieces (Fig. 148) : a central, consisting of the body and small wings, and two lateral,
each compnsmg a great wing and ptery-goid. process. In the first vear after birth the great wings
and body unite, and the small wings extend inward above the anterior part of the body, and,
meeting with each other in the middle hne, form an elevated smooth surface, termed ihejugum
sphenoidale. By the twenty-fifth year the sphenoid and occipital arc completely fused. Between
the pre- and postsphenoid there are occasionally seen the remains of a canal, the canalis cranio-
pharyngeus, through which, in early fetal life, the hypophyseal diverticulum of the buccal ecto-
derm IS transmitted.
The sphenoidal sinuses are present as minute cavities at the time of birth (Onodi), but do not
attain their full size until after puberty.
Intrinsic Ligaments of the Sphenoid.— The more important of these are: the pierygospinous,
stretching between the spina angularis and the lateral pterj^goid plate (see cervical fascia); the
tnterchnoid, a fibrous process joining the anterior to the posterior clinoid process; and the
caroticoclinoid, connecting the anterior to the middle cUnoid process. These ligaments occa-
sionally ossify.
Articulations.— The sphenoid articulates with twelve bones: four single, the vomer, ethmoid,
frontal, and occipital; and four paired, the parietal, temporal, zygomatic, and palatine.^
The Ethmoid Bone fOs Ethmoidale).
The ethmoid bone i.s exceedingly light and spongy, and cubical in shape; it
IS situated at the anterior part of the base of the cranium, between the two orbits,
at the roof of the nose, and contributes to each of these cavities. It consists of
four parts: a horizontal or cribriform plate, forming part of the base of the cranium;
a perpendicular plate, constituting part of the nasal septum; and two lateral masses
or labyrinths.
Cribiform Plate {lamina cribrosa; horizontal lamina).— The cribriform plate
(Fig. 149) is received into the ethmoidal notch of the frontal bone and roofs in
the nasal cavities. Projecting upward from the middle line of this plate is a thick,
smooth, triangular process, the crista galli, so called from its resemblance to a
cock's comb. The long thin posterior border of the crista galli serves for the
attachment of the falx cerebri.
Its anterior border, short and
thick, articulates with the frontal
bone, and presents two small pro-
jecting alae, which are received
into corresponding depressions in
the frontal bone and complete
the foramen cecum. Its sides are
smooth, and sometimes bulging
from the presence of a small air
sinus in the interior. On either
side of the crista galli, the cribri-
form plate is narrow and deeply
grooved ; it supports the olfactory
bulb and is perforated by fora-
mina for the passage of the olfac-
tory nerves. The foramina in the
middle of the groove are small
and transmit the nerves to the
roof of the nasal cavity; those at the medial and lateral parts of the groove are
larger — the former transmit the nerves to the upper part of the nasal septum,
the latter those to the superior nasal concha. At the front part of the cribriform
' Anatomischer Anzeiger. March. 1905.
It also sometimes articulates with the tuberosity of the maxilla (see page 159).
Perpendicular plate
Ala
Crista galli
Cribriform plain
Anterior ethmoidal
groove
Posterior ethmoidal
groove
Fig. 149. — tlhiuoid bone from above.
154
OSTEOLOGY
plate, on either side of the crista galh, is a small fissure which is occupied by a
process of dura mater. Lateral to this fissure is a notch or foramen which trans-
mits the nasociliary nerve; from this notch
anterior ethmoidal foramen.
a groove extends backward to the
^thEthmo.
Fig. 150. — Perpendicular plate of ethmoid. Shown by removing the right labyrinth.
Perpendicular Plate (laviina perpendmdaris; vertical plate). — The perpendicular
plate (Figs. 150, 151) is a thin, flattened lamina, polygonal in form, which descends
from the under surface of the cribriform plate, and assists in forming the septum
of the nose; it is generally deflected a little to one or other side. The anterior border
articulates with the spine of the frontal bone and the crest of the nasal bones.
The posterior border articulates by its upper half with the sphenoidal crest, by its
lower with the vomer. The inferior border is thicker than the posterior, and serves
for the attachment of the septal cartilage of the nose. The surfaces of the plate
are smooth, except above, where numerous grooves and canals are seen; these
lead from the medial foramina on the cribriform plate and lodge filaments of the
olfactory nerves.
The Labyrinth or Lateral Mass {labyrinthus ethmoidalis) consists of a number
of thin-walled cellular cavities, the ethmoidal cells, arranged in three groups,
anterior, middle, and posterior, and inter-
posed between two vertical plates of bone ;
the lateral plate forms part of the orbit,
the medial, part of the corresponding
nasal cavity. In the disarticulated bone
many of these cells are opened into, but
when the bones are articulated, they are
closed in at every part, except where
they open into the nasal cavity.
Surfaces. — The upper surface of the laby-
rinth (Fig. 149) presents a number of
half-broken cells, the walls of which are
completed, in the articulated skull, by
the edges of the ethmoidal notch of the
frontal bone. Crossing this surface are
two grooves, converted into canals by articulation with the frontal; they are the
anterior and posterior ethmoidal canals, and open on the inner wall of the orbit.
The posterior surface presents large irregular cellular cavities, which are closed in
Fig. 151.-
Crista gain
— Labyrinth
Superior nasal
concha
Superior meatus
Uncinate process
Middle nasal concha
Perpendicular plate
Ethmoid bone from behind.
THE ETHMOID BONE
155
by articulation with the sphenoidal concha and orbital process of the palatine.
The lateral surface (Fig. 152) is formed of a thin, smooth, oblong plate, the lamina
papyracea {os planum), which covers in the middle and posterior ethmoidal cells
Ethmoidal
cells
Per'pendicular
plate
Uncinate process
Fig. 152. — Ethmoid bone from the right side.
and forms a large part of the medial wall of the orbit; it articulates above with
the orbital plate of the frontal bone, below with the maxilla and orbital process
of the palatine, in front with the lacrimal, and behind with the sphenoid.
In front of the lamina papyracea are some broken air cells which are overlapped
and completed by the lacrimal bone and the frontal process of the maxilla. A
Frontal sinus
Crista galli
Sella turcica
Uncinate
process of
ethmoid
ngs into
maxillary simis
Medial pterygoid plate
Hamulus
Fio. 153. — Lateral wall of nasal cavity, showing ethmoid bone in position.
curved lamina, the uncinate process, projects downward and backward from this
part of the labyrinth; it forms a small part of the medial wall of the maxillary
sinus, and articulates with the ethmoidal process of the inferior nasal concha.
156 OSTEOLOGY
The medial surface of the labyrinth (Fig. 153) forms part of the lateral wall
of the corresponding nasal cavity. It consists of a thin lamella, which descends
from the under surface of the cribriform plate, and ends below in a free, convoluted
margin, the middle nasal concha. It is rough, and marked above by numerous
grooves, directed nearly vertically downward from the cribriform plate; they
lodge branches of the olfactory nerves, which are distributed to the mucous mem-
brane covering the superior nasal concha. The back part of the surface is sub-
divided by a narrow oblique fissure, the superior meatus of the nose, bounded above
by a thin, curved plate, the superior nasal concha; the posterior ethmoidal cells
open into this meatus. Below, and in front of the superior meatus, is the convex
surface of the middle nasal concha; it extends along the whole length of the medial
surface of the labyrinth, and its lower margin is free and thick. The lateral surface
of the middle concha is concave, and assists in forming the middle meatus of the
nose. The middle ethmoidal cells open into the central part of this meatus, and a
sinuous passage, termed the infundibulum, extends upward and forward through
the labyrinth and communicates with the anterior ethmoidal cells, and in about
50 per cent, of skulls is continued upward as the frontonasal duct into the frontal
sinus.
Ossification. — The ethmoid is ossified in the cartilage of the nasal capsule by three centers:
one for the perpendicular plate, and one for each labyrinth.
The labjTinths are first developed, ossific granules making their appearance in the region of
the lamina papyracea between the fourth and fifth months of fetal life, and extending into the
concha^. At birth, the bone consists of the two labyrinths, which are small and ill-developed.
During the first year after birth, the perpendicular plate and crista galli begin to ossify from a
single center, and are joined to the labyrinths about the beginning of the second year. The
cribriform plate is ossified partly from the perpendicular plate and partly from the labyrinths.
The development of the ethmoidal cells begins during fetal life.
Articulations. — The ethmoid articulates with fifteen bones: four of the cranium — the frontal,
the sphenoid, and the two sphenoidal conchse; and eleven of the face — -the two nasals, two maxilla),
two lacrimals, two palatines, two inferior nasal conchie, and the vomer.
Sutural or Wormian' Bones. — In addition to the usual centers of ossification of the cranium,
others may occur in the course of the sutures, giving rise to irregular, isolated bones, termed
sutural or Wormian bones. They occur most frequently in the course of the lambdoidal suture,
but are occasionally seen at the fontanelles, especially the posterior. One, the pterion ossicle,
sometimes exists between the sphenoidal angle of the parietal and the great wing of the sphenoid.
They have a tendency to be more or less symmetrical on the two sides of the skull, and vary
much in size. Their number is generally limited to two or three; but more than a hundred have
been found in the skull of an adult hydrocephalic subject.
THE FACIAL BONES (OSS A FACIEI).
The Nasal Bones (Ossa Nasalia).
The nasal bones are two small oblong bones, varying in size and form in different
individuals; they are placed side by side at the middle and upper part of the face,
and form, by their junction, "the bridge" of the nose (Fig. 190). Each has two
surfaces and four borders.
Surfaces. — The outer surface (Fig. 155) is concavoconvex from above downward,
convex from side to side; it is covered by the Procerus and Compressor naris, and
perforated about its center by a foramen, for the transmission of a small vein.
The inner surface (F'ig. 150) is concave from side to side, and is traversed from above
downward, by a groove for the passage of a branch of the nasociliary nerve.
Borders. — The superior border is narrow, thick, and serrated for articulation with
the nasal notch of the frontal bone. The inferior border is thin, and gives attach-
' Ole Worm, Professor of Anatomy at Copenhagen, 1624-1639, was erroneously supposed to have given the first
detailed description of these bones.
THE MAXILLA
157
ment to the lateral cartilage of the nose; near its middle is a notch which marks
the end of the groove just referred to. The lateral border is serrated, bevelled
at the expense of the inner surface above, and of the outer below, to articulate
with the frontal process of the maxilla. The medial border, thicker above than
Fossa for lacrimal sac
Infraorbital
foramen
Fig. 154. — Articulation of nasal and lacrimal bones with maxilla.
below, articulates with its fellow of the opposite side, and is prolonged behind into
a vertical crest, which forms part of the nasal septum: this crest articulates, from
above downward, with the spine of the frontal, the perpendicular plate of the
ethmoid, and the septal cartilage of the nose.
Foramen
'or vein
fiit/i
Fig. 155. — Right nasal bone. Outer surface.
Groove.
Fig. 156. — Right nasal bone. Inner surface.
Ossification. — Each bone is ossified from one center, which appears at the beginning of the
third month of fetal life in the membrane overlying the front part of the cartilaginous nasal
capsule.
Articulations. — The nasal articulates with four bones: two of the cranium, the frontal and
ethmoid, and two of the face, the opposite nasal and the maxilla.
The Maxillae (Upper Jaw).
The maxillae are the largest bones of the face, excepting the mandible, and
form, by their union, the whole of the upper jaw. Each assists in forming the
158
OSTEOLOGY
boundaries of three cavities, viz., the roof of the mouth, the floor and lateral
wall of the nose and the floor of the orbit; it also enters into the formation of two
fossae, the infratemporal and pterygopalatine, and two fissures, the inferior orbital
and pterygomaxillary.
Each bone consists of a body and four processes — zygomatic, frontal, alveolar,
and palatine.
The Body (corpus maxillor). — The body is somewhat pyramidal in shape, and
contains a large cavity, the maxillary sinus (antrum of HigJunore). It has four
surfaces — an anterior, a posterior or infratemporal, a superior or orbital, and a
medial or nasal.
Surfaces. — The anterior surface (Fig, 157) is directed forward and lateralward.
It presents at its lower part a series of eminences corresponding to the positions
of the roots of the teeth. Just above those of the incisor teeth is a depression,
the incisive fossa, which gives origin to the Depressor a\-x nasi; to the alveolar
border below the fossa is attached a slip of the Orbicularis oris; above and a little
Med. palp. lig.~r^l
I* ^Lacrimal tubercle
DILATATOR NARIS POSTERIOR
Incisive fossa
"tu ^Alveclar canals
Maxillary tuberosity
Fig. 157. — Left masilla. Outer surface.
lateral to it, the Xasalis arises. Lateral to the incisive fossa is another depression,
the canine fossa; it is larger and deeper than the incisive fossa, and is separated
from it by a vertical ridge, the canine eminence, corresponding to the socket of
the canine tooth; the canine fossa gives origin to the Caninus. Above the fossa
is the infraorbital foramen, the end of the infraorbital canal ; it transmits the infra-
orbital vessels and nerve. Above the foramen is the margin of the orbit, which
affords attachment to part of the Quadratus labii superioris. ^Medially, the anterior
surface is limited by a deep concavity, the nasal notch, the margin of which gives
attachment to the Dilatator naris posterior and ends below in a pointed process,
which with its fellow of the opposite side forms the anterior nasal spine.
The infratemporal surface (Fig. 157) is convex, directed backward and lateral-
ward, and forms part of the infratemporal fossa. It is separated from the anterior
surface by the zygomatic process and by a strong ridge, extending upward from
the socket of the first molar tooth. It is pierced about its center by the apertures
of the alveolar canals, which transmit the posterior superior alveolar vessels and
nerves. At the lower part of this surface is a rounded eminence, the maxillary
THE MAXILLA
159
tuberosity, especially prominent after the growth of the wisdom tooth; it is rough
on its lateral side for articulation with the pyramidal process of the palatine bone
and in some cases articulates with the lateral pterygoid plate of the sphenoid.
It gives origin to a few fibers of the Pterygoideus internus. Immediately above
this is a smooth surface, which forms the anterior boundary of the pterygopalatine
fossa, and presents a groove, for the maxillary nerve; this groove is directed lateral-
ward and slightly upward, and is continuous with the infraorbital groove on the
orbital surface.
The orbital surface (Fig. 157) is smooth and triangular, and forms the greater
part of the floor of the orbit. It is bounded medially by an irregular margin which
in front presents a notch, the lacrimal notch; behind this notch the margin articu-
lates with the lacrimal, the lamina papyracea of the ethmoid and the orbital process
of the palatine. It is bounded behind by a smooth rounded edge which forms
the anterior margin of the inferior orbital fissure, and sometimes articulates at
its lateral extremity with the orbital surface of the great wing of the sphenoid.
With frontal
Bones partially closing orifice of sinus
marked in red
Ethmoid-
Inferior nasal concha — -^^^V
Palati}ie
ith nasal bone
Ani. TMsal spine
Bristle passed
through incisive
canal
Fig. 158. — Left maxilla. Nasal surface.
It is limited in front by part of the circumference of the orbit, which is continuous
medially with the frontal process, and laterally with the zyogmatic process. Near
the middle of the posterior part of the orbital surface is the infraorbital groove,
for the passage of the infraorbital vessels and nerve. The groove begins at the
middle of the posterior border, where it is continuous with that near the upper
edge of the infratemporal surface, and, passing forward, ends in a canal, which
subdi^•ides into two branches. One of the canals, the infraorbital canal, opens
just below the margin of the orbit; the other, wdiich is smaller, runs downward in
the substance of the anterior wall of the maxillary sinus, and transmits the anterior
superior alveolar vessels and nerve to the front teeth of the maxilla. From the
back part of the infraorbital canal, a second small canal is sometimes given off; it
runs downward in the lateral wall of the sinus, and con\'eys the middle alveolar
nerve to the premolar teeth. At the medial and forepart of the orbital surface,
just lateral to the lacrimal groove, is a depression, which gives origin to the Obliquus
oculi inferior.
160
OSTEOLOGY
The nasal surface (Fig. 158) presents a large, irregular opening leading into the
maxillary sinus. At the upper border of this aperture are some broken air cells,
which, in the articulated skull, are closed in by the ethmoid and lacrimal bones.
Below the aperture is a smooth concavity which forms part of the inferior meatus
of the nasal cavity, and behind it is a rough surface for articulation with the per-
pendicular part of the palatine bone; this surface is traversed by a groove, com-
mencing near the middle of the posterior border and running obliquely downward
and forward; the groove is converted into a canal, the pterygopalatine canal, by the
palatine bone. In front of the opening of the sinus is a deep groove, the lacrimal
groove, which is converted into the nasolacrimal canal, by the lacrimal bone and
inferior nasal concha; this canal opens into the inferior meatus of the nose and
transmits the nasolacrimal duct. INlore anteriorly is an oblique ridge, the conchal
crest, for articulation with the inferior nasal concha. The shallow concavity above
this ridge forms part of the atrium of the middle meatus of the nose, and that
below it, part of the inferior meatus.
Anterior
ethmoidal foramen
Posterior ethmoidal foramen
Orbital process of •palatine
Oplic foiamen
Sphenopalatine foramen
SeUa turcica
Probe m foramen rotundum
Fossa for
lacrimal sac
Uncinate process
of etinnoid
Openings of
maxillary sinus
Inferior nasal
concha
Probe in pterygoid canal
/ Probe in pterygopalatiiie canal
/^Palatine bone
\^ Lateral pterygoid plate
Pyramidal process cf palatine
Fig. 1o9. — Left maxillary sinus opened from the exterior.
The Maxillary Sinus or Antrum of Highmore (simis maxillaris) . — The maxillary
sinus is a large pyramidal cavity, within the body of the maxilla: its apex, directed
lateralward, is formed by the zygomatic process; its base, directed medialward,
by the lateral wall of the nose. Its walls are everywhere exceedingly thin, and
correspond to the nasal orbital, anterior, and infratemporal surfaces of the body
of the bone. Its nasal wall, or base, presents, in the disarticulated bone, a large,
irregular aperture, communicating with the nasal cavity. In the articulated
skull this aperture is much reduced in size by the following bones: the uncinate
process of the ethmoid above, the ethmoidal process of the inferior nasal concha
below, the vertical part of the palatine behind, and a small part of the lacrimal
above and in front (Figs. 158, 159) ; the sinus communicates with the middle meatus
THE MAXILLA 161
of the nose, generally by two small apertures left between the above-mentioned
bones. In the fresh state, usually only one small opening exists, near the upper
part of the cavity; the other is closed by mucous membrane. On the posterior
wall are the alveolar canals, transmitting the posterior superior alveolar vessels
and nerves to the molar teeth. The floor is formed by the alveolar process of the
maxilla, and, if the sinus be of an average size, is on a level with the floor of
the nose; if the sinus be large it reaches below this level.
Projecting into the floor of the antrum are several conical processes, correspond-
ing to the roots of the first and second molar teeth ;i in some cases the floor is
perforated by the fangs of the teeth. The infraorbital canal usually projects into
the cavity as a well-marked ridge extending from the roof to the anterior wall;
additional ridges are sometimes seen in the posterior wall of the cavity, and
are caused by the alveolar canals. The size of the cavity varies in different skulls,
and even on the two sides of the same skull. ^
The Zygomatic Process {processus zygomaticus; malar process). — The zygomatic
process is a rough triangular eminence, situated at the angle of separation of the
anterior, zygomatic, and orbital surfaces. In front it forms part of the anterior
surface; beJmid, it is concave, and forms part of the infratemporal fossa; above,
it is rough and serrated for articulation wdth the zygomatic bone; while below,
it presents the prominent arched border which marks the division between the
anterior and infratemporal surfaces.
The Frontal Process ('processus frontalis; nasal process). — The frontal process
is a strong plate, which projects upward, medialward, and backward, by the side
of the nose, forming part of its lateral boundary. Its lateral surface is smooth,
continuous with the anterior surface of the body, and gives attachment to the
Quadratus labii superioris, the Orbicularis oculi, and the medial palpebral ligament.
Its medial surface forms part of the lateral wall of the nasal cavity; at its upper
part is a rough, uneven area, which articulates with the ethmoid, closing in the
anterior ethmoidal cells; below this is an oblique ridge, the ethmoidal crest, the
posterior end of which articulates with the middle nasal concha, while the anterior
part is termed the agger nasi; the crest forms the upper limit of the atrium of the
middle meatus. The upper border articulates with the frontal bone and the anterior
with the nasal; the posterior border is thick, and hollowed into a groove, which is
continuous below with the lacrimal groove on the nasal surface of the body: by
the articulation of the medial margin of the groove with the anterior border of
the lacrimal a corresponding groove on the lacrimal is brought into continuity,
and together they form the lacrimal fossa for the lodgement of the lacrimal sac.
The lateral margin of the groove is named the anterior lacrimal crest, and is con-
tinuous below with the orbital margin; at its junction with the orbital surface is
a small tubercle, the lacrimal tubercle, which serves as a guide to the position of
the lacrimal sac.
The Alveolar Process {processus alveolaris). — The alveolar process is the thickest
and most spong}' part of the bone. It is broader behind than in front, and exca-
vated into deep cavities for the reception of the teeth. These cavities are eight
in number, and vary in size and depth according to the teeth they contain. That
for the canine tooth is the deepest; those for the molars are the widest, and are
subdivided into minor cavities by septa; those for the incisors are single, but
deep and narrow. The Buccinator arises from the outer surface of this process,
as far forward as the first molar tooth. When the maxillae are articulated with each
other, their alveolar processes together form the alveolar arch; the center of the
anterior margin of this arch is named the alveolar point.
1 The number of teeth whose roots are in relation with the floor of the antrum is variable. The sinus "may extend
so as to be in relation to all the teeth of the true maxilla, from the canine to the dens aapicnlicc. " (Salter.)
2 Aldren Turner (op. cit.) gives the following measurements as those of an average sized sinus: vertical height
opposite first molar tooth, 1}^ inch; transverse breadth, 1 inch; and antero-posterior depth, \]4 inch.
11
162
OSTEOLOGY
The Palatine Process (processus palatiniis; palatal process). — ^The palatine
process, thick and strong, is horizontal and projects mediahvard from the nasal
surface of the bone. It forms a considerable part of the floor of the nose and the
roof of the mouth and is much thicker in front than behind. Its inferior surface
(Fig. 160) is concave, rough and uneven, and forms, with the palatine process of
the opposite bone, the anterior three-fourths of the hard plate. It is perforated
by numerous foramina for the passage of the nutrient vessels; is channelled at the
back part of its lateral border by a groove, sometimes a canal, for the transmission
of the descending palatine vessels and the anterior palatine nerve from the spheno-
palatine ganglion; and presents little depressions for the lodgement of the palatine
glands. When the two maxillse are articulated, a funnel-shaped opening, the
incisive foramen, is seen in the middle line, immediately behind the incisor teeth.
In this opening the orifices of two lateral canals are visible; they are named the
Incisive canals
Incisive foramen
Foramina of Scarpa
Palatine process of mnzilla ^ Greater palatine foramen
Horizontal plate of palatine bone Lesser palatine foramina
Fig. 160. — The bony palate and alveolar arch.
incisive canals or foramina of Stenson; through each of them passes the terminal
branch of the descending palatine artery and the nasopalatine nerve. Occasionally
,two additional canals are present in the middle line; they are termed the foramina
of Scarpa, and when present transmit the nasopalatine nerves, the left passing
through the anterior, and the right through the posterior canal. On the under
surface of the palatine process, a delicate linear suture, well seen in young skulls,
mav sometimes be noticed extending lateralward and forward on either side from
the incisive foramen to the interval between the lateral incisor and the canine tooth.
The small part in front of this suture constitutes the premaxilla {os incisimm),
which in most vertebrates forms an independent bone ; it includes the whole thick-
ness of the alveolus, the corresponding part of the floor of the nose and the anterior
nasal spine, and contains the sockets of the incisor teeth. The upper surface of
the palatine process is concave from side to side, smooth, and forms the greater
part of the floor of the nasal cavity. It presents, close to its medial margin, the
THE LACRIMAL BONE
163
upper orifice of the incisive canal. The lateral border of the process is incorporated
with the rest of the bone. The medial border is thicker in front than behind, and
is raised above into a ridge, the nasal crest, which, with the corresponding ridge
of the opposite bone, forms a groove for the reception of the vomer. The front
part of this ridge rises to a considerable height, and is named the incisor crest;
it is prolonged forward into a sharp process, which forms, together with a similar
process of the opposite bone, the anterior nasal spine. The 'posterior border is ser-
rated for articulation with the horizontal part of the palatine bone.
Ossification. — The maxilla is ossified in membrane. Mall* and Fawcett^ maintain that it is
ossified from tiro centers only, one for the maxilla proper and one for the premaxilla. These
centers appear during the sixth week of fetal life and unite in the beginning of the third month,
but the suture between the two portions persists on the palate until nearly middle life. Mall
states that the frontal process is developed from both centers. The maxillary sinus appears as
a shallow groove on the nasal surface of the bone about the fourth month of fetal life, but does
not reach its full size until after the second dentition. The maxilla was formerly described as
ossifying from six centers, viz., one, the orbitonasal, forms that portion of the body of the bone
which lies medial to the infraorbital canal, including the medial part of the floor of the orbit and
the lateral wall of the nasal cavity; a second, the zygomatic, gives origin to the portion which lies
lateral to the infraorbital canal, including the zj-gomatic process; from a third, the palatine, is
developed the palatine process posterior to the incisive canal together with the adjoining part
of the nasal wall; a fourth, the premaxillary, forms the incisive bone which carries the incisor
Fig. 161. — Anterior surface of maxilla at birth.
Fig. 162. — Inferior surface of maxilla at birth.
teeth and corresponds to the premaxilla of the lower vertebrates;' a fifth, the nasal, gives rise to
the frontal process and the portion above the canine tooth; and a sixth, the infravomerine, Ues
between the palatine and premaxillary centers and beneath the vomer; this center, together with
the corresponding center of the opposite bone, separates the incisive canals from each other.
Articulations. — The maxilla articulates with nine bones: two of the cranium, the frontal and
ethmoid, and seven of the face, viz., the nasal, zygomatic, lacrimal, inferior nasal concha, palatine,
vomer, and its fellow of the opposite side. Sometimes it articulates with the orbital surface,
and sometimes with the lateral pterygoid plate of the sphenoid.
CHANGES PRODUCED IN THE MAXILLA BY AGE.
At birth the transverse and antero-posterior diameters of the bone are each greater than the
vertical. The frontal process is well-marked and the body of the bone consists of little more than
the alveolar process, the teeth sockets reaching almost to the floor of the orbit. The maxillary
sinus presents the appearance of a furrow on the lateral wall of the nose. In the adult the vertical
diameter is the greatest, owing to the development of the alveolar process and the increase in
size of the sinus. In old age the bone reverts in some measure to the infantile condition; its
height is diminished, and after the loss of the teeth the alveolar process is absorbed, and the
lower part of the bone contracted and reduced in thickness.
The Lacrimal Bone (Os Lacrimale).
The lacrimal bone, the smallest and most fragile bone of the face, is situated
at the front part of the medial wall of the orbit (Fig. 164). It has two surfaces
and four borders.
' American Journal of Anatomj', 1906, vol. v.
2 Journal of Anatomv and Physiology, 1911, vol. xlv.
3 Some anatomists believe that the premaxillary bone is ossified by two centers (see page 299).
164 OSTEOLOGY
Surfaces. — The lateral or orbital surface (Fig. 163) is divided by a vertical ridge,
the posterior lacrimal crest, into two parts. In front of this crest is a longitudinal
groove, the lacrimal sulcus {sulcus lacrimalis) , the inner margin of which unites
with the frontal process of the maxilla, and the lacrimal fossa is thus completed.
The upper part of this fossa lodges the lacrimal sac, the lower part, the naso-
lacrimal duct. The portion behind the crest is smooth,, and forms part of the
medial wall of the orbit. The crest, with a part of the orbital surface imme-
diately behind it, gives origin to the lacrimal part of the Orbicularis oculi and
ends below in a small, hook-like projection, the lacrimal hamulus, which articu-
lates with the lacrimal tubercle of the maxilla, and completes
wiOFronfai the Upper orifice of the lacrimal canal; it sometimes exists as
/j/'^k^^ \ a ^ separate piece, and is then called the lesser lacrimal bone.
The medial or nasal surface presents a longitudinal furrow,
corresponding to the crest on the lateral surface. The area in
front of this furrow forms part of the middle meatus of the
nose; that behind it articulates with the ethmoid, and completes
some of the anterior ethmoidal cells.
Borders. — Of the four borders the anterior articulates with
the frontal process of the maxilla ; the posterior with the lamina
infe^lmsai concha papyracca of the ethmoid; the superior with the frontal bone.
Fig. 163.— Left lacri- The inferior is divided by the lower edge of the posterior lacri-
face. ^niarged.'*^ ^""^ mal crest iuto two parts : the posterior part articulates with the
orbital plate of the maxilla; the anterior is prolonged downward
as the descending process, which articulates with the lacrimal process of the inferior
nasal concha, and assists in forming the canal for the nasolacrimal duct.
Ossification. — The lacrimal is ossified from a single center, which appears about the twelfth
week in the membrane covering the cartilaginous nasal capsule.
Articulations. — The lacrimal articulates with four bones: two of the cranium, the frontal
and ethmoid, and two of the face, the maxilla and the inferior nasal concha.
The Zygomatic Bone (Os Zygomaticum; Malar Bone).
The zygomatic bone is small and quadrangular, and is situated at the upper
and lateral part of the face? it forms the prominence of the cheek, part of the
lateral wall and floor of the orbit, and parts of the temporal and infratemporal
fossae (Fig. 164). It presents a malar and a temporal surface; four processes, the
frontosphenoidal, orbital, maxillary, and temporal; and four borders.
Surfaces. — The malar surface (Fig. 165) is convex and perforated near its center
by a small aperture, the zygomaticofacial foramen, for the passage of the zygomatico-
facial nerve and vessels; below this foramen is a slight elevation, which gives
origin to the Zygomaticus.
The temporal surface (Fig. 166), directed backward and medialward, is concave,
presenting medially a rough, triangular area, for articulation with the maxilla,
and laterally a smooth, concave surface, the upper part of which forms the anterior
boundary of the temporal fossa, the lower a part of the infratemporal fossa. Near
the. center of this surface is the zygomaticotemporal foramen for the transmission
of the zygomaticotemporal nerve.
Processes. — The frontosphenoidal process is thick and serrated, and articulates
with the zygomatic process of the frontal bone. On its orbital surface, just within
the orbital margin and about 11 mm. below the zygomaticofrontal suture is a
tubercle of varying size and form, but present in 95 per cent, of skulls (WhitnalP).
' Journal of .\natomy and Physiology, vol. xlv. The structures attached to this tubercle are: (1) the check
ligament of the Rectus lateralis; (2) the lateral end of the aponeurosis of the Levator palpebrae superioris; (3) the
suspensory ligament of the eye (Lockwood) ; and (4) the lateral extremities of the superior and inferior tarsi.
THE ZYGOMATIC BONE
165
The orbital process is a thick, strong pLate, projecting backward and mecUahvard
from the orbital margin. Its antero-medial surface forms, by its junction with
the orbital surface of the maxilla and with the great wing of the sphenoid, part
of the floor and lateral wall of the orbit. On it are seen the orifices of two canals,
'M Parietal
Fig. 164. — Left zygomatic bone in situ.
the zygomaticoorbital foramina; one of these canals opens into the temporal fossa,
the other on the malar surface of the bone; the former transmits the zygomatico-
temporal, the latter the zygomaticofacial nerve. Its iwstero-Jateral surface, smooth
and convex, forms parts of the temporal and infratemporal fossse. Its anterior
margin, smooth and rounded, is part of the circumference of the orbit. Its superior
With Frontal
Bristles passed
through
zygomat ico-
orbilal foramina
Fig. 165. — Left zygomatic bone. Malar surface.
Fig. 166. — Left zygomatic bone. Temporal surface.
margin, rough, and directed horizontally, articulates with the frontal bone behind
the zygomatic process. Its posterior margin is serrated for articulation, with the
great wing of the sphenoid and the orbital surface of the maxilla. At the angle
of junction of the sphenoidal and maxillary portions, a short, concave, non-articular
166
OSTEOLOGY
part is generally seen; this forms the anterior boundary of the inferior orbital fissure:
occasionally, this non-articular part is absent, the fissure then being completed
by the junction of the maxilla and sphenoid, or by the interposition of a small
sutural bone in the angular interval between them. The maxillary process presents
a rough, triangular surface which articulates with the maxilla. The temporal
process, long, narrow, and serrated, articulates with the zygomatic process of the
temporal.
Borders. — The antero-superior or orbital border is smooth, concave, and forms
a considerable part of the circumference of the orbit. The antero-inferior or maxil-
lary border is rough, and bevelled at the expense of its inner table, to articulate
with the maxilla; near the orbital margin it gives origin to the Quadratus labii
superioris. The postero-superior or temporal border, curved like an italic letter /,
is continuous above with the commencement of the temporal line, and below with
the upper border of the zygomatic arch; the temporal fascia is attached to it.
The postero-inferior t)r zygomatic border affords attachment by its rough edge to
the Masseter.
Ossification. — The zygomatic bone is generally described as ossifying from three centers —
one for the malar and two for the orbital portion; these appear about the eighth week and fuse
about the fifth month of fetal life. Mall describes it as being ossified from one center which
appears just beneath and to the lateral side of the orbit. After birth, the bone is sometimes
divided by a horizontal suture into an upper larger, and a lower smaller division. In some quad-
rumana the zygomatic bone consists of two parts, an orbital and a malar.
Articulations. — The zygomatic articulates with /oar bones: the frontal, sphenoidal, temporal,
and maxilla.
Groove for
nasolacrimal duct
Frontal process
Maxillary siuus
Orbital process
Sphenopalatine
notch
Sphenoidal
process
Conchal crest
-Concfial crest
Fig. 167. — Articulation of left palatine bone with maxilla.
The Palatine Bone (Os Palatinum; Palate Bone).
The palatine bone is situated at the back part of the nasal cavity between the
maxilla and the pterygoid process of the sphenoid (Fig. 167). It contributes
to the walls of three cavities: the floor and lateral wall of the nasal cavity, the
roof of the mouth, and the floor of the orbit; it enters into the formation of two
fossae, the pterygopalatine and pterygoid fossae; and one fissure, the inferior orbital
fissure. The palatine bone somewhat resembles the letter L, and consists of a
horizontal and a vertical part and three outstanding processes — viz., the pyramidal
THE PALATINE BONE
167
process, which is directed backward and lateralward from the junction of the two
parts, and the orbital and sphenoidal processes, which surmount the vertical
part, and are separated by a deep notch, the sphenopalatine notch.
The Horizontal Part (pars horizontalis ; horizontal plate) (Figs. 108, 169).— The
horizontal part is quadrilateral, and has two surfaces and four borders.
Surfaces. — The superior surface, concave from side to side, forms the back part
of the floor of the nasal cavity. The inferior surface, slightly concave and rough,
forms, with the corresponding surface of the opposite bone, the posterior fourth
of the hard palate. Near its posterior margin may be seen a more or less marked
transverse ridge for the attachment of part of the aponeurosis of the Tensor veli
palatini.
■^jlid Pi'oc
Maxillary surface
Superior meatus.
Sphenopalatine foramen —
/»>,
01
,.V'-
SiirJ
Maxillary
process
t Pterygo-
►J palatine ,
o canal
Sphenopalatine
foramen
Sphenoidal process
Articular portion
Non-articular
portion
Fig. 168.-
HORIZONTAL PART
-Left palatine bone.
Enlarged.
iifSm
nlkiL,. ^^^3
S Posterior
jmiim
l>lpp** ^
nasal
/wc'^i^^^^.^BI jfl
XjMusculus uvulae
spine
Pyramidal \P
^ HORIZONTAL
process
PART
Nasal aspect.
Fig. 169. — Left palatine bone. Posterior aspect.
Enlarged.
Borders. — The anterior border is serrated, and articulates with the palatine process
of the maxilla. The posterior border is concave, free, and serves for the attachment
of the soft palate. Its medial end is sharp and pointed, and, when united with
that of the opposite bone, forms a projecting process, the posterior nasal spine
for the attachment of the IMusculus uvulae. The lateral border is united with
the lower margin of the perpendicular part, and is grooved by the lower end of
the pterygopalatine canal. The medial border, the thickest, is serrated for articu-
lation with its fellow of the opposite side; its superior edge is raised into a ridge,
which, united with the ridge of the opposite bone, forms the nasal crest for articu-
lation with the posterior part of the lower edge of the vomer.
The Vertical Part {pars perpendicularis; perpendicular plate) (Figs. 168, 169). —
The vertical part is thin, of an oblong form, and presents two surfaces and four
borders.
Surfaces. — The nasal surface exhibits at its lower part a broad, shallow depres-
sion, which forms part of the inferior meatus of the nose. Immediately above this
is a well-marked horizontal ridge, the conchal crest, for articulation with the
inferior nasal concha; still higher is a second broad, shallow depression, which
forms part of the middle meatus, and is limited above by a horizontal crest less
prominent than the inferior, the ethmoidal crest, for articulation with the middle
nasal concha. Above the ethmoidal crest is a narrow, horizontal groove, which
forms part of the superior meatus.
168 OSTEOLOGY
The maxillary surface is rough and irregular throughout the greater part of its
extent, for articuhition with the nasal surface of the maxilla; its upper and back
part is smooth where it enters into the formation of the pterygopalatine fossa;
it is also smooth in front, where it forms the posterior part of the medial wall
of the maxillary sinus. On the posterior part of this surface is a deep vertical
groove, converted into the pterygopalatine canal, by articulation with the maxilla;
this canal transmits the descending palatine vessels, and the anterior palatine
nerve.
Borders. — The anterior border is thin and irregular; opposite the conchal crest is a
pointed, projecting lamina, the maxillary process, which is directed forward, and
closes in the lower and back part of the opening of the maxillary sinus. The
posterior border (Fig. 1G9) presents a deep groove, the edges of which are serrated
for articulation with the medial pterygoid plate of the sphenoid. This border
is continuous above with the sphenoidal process; below it expands into the
pyramidal process. The superior border supports the orbital process in front and the
sphenoidal process behind. These processes are separated by the sphenopalatine
notch, which is converted into the sphenopalatine foramen by the under surface of
the body of the sphenoid. In the articulated skull this foramen leads from the
pterygopalatine fossa into the posterior part of the superior meatus of the nose,
and transmits the sphenopalatine vessels and the superior nasal and nasopalatine
nerves. The inferior border is fused with the lateral edge of the horizontal part,
and immediately in front of the pyramidal process is grooved by the lower end
of the pterygopalatine canal.
The JPyramidal Process or Tuberosity (processus pyramidalis). — The pyramidal
process projects backward and lateralward from the junction of the horizontal
and vertical parts, and is received into the angular interval between the lower
extremities of the pterygoid plates. On its posterior surface is a smooth, grooved,
triangular area, limited on either side by a rough articular furrow. The furrows
articulate with the pterygoid plates, while the grooved intermediate area completes
the lower part of the pterygoid fossa and gives origin to a few fibers of the Ptery-
goideus internus. The anterior part of the lateral surface is rough, for articulation
with the tuberosity of the maxilla; its posterior part consists of a smooth triangular
area which appears, in the articulated skull, between the tuberosity of the maxilla
and the lower part of the lateral pterygoid plate, and completes the lower part
of the infratemporal fossa. On the base of the pyramidal process, close to its
union with the horizontal part, are the lesser palatine foramina for the transmis-
sion of the posterior and middle palatine nerves.
The Orbital Process (processus orbitalis). — The orbital process is placed on a
higher level than the sphenoidal, and is directed upward and lateralward from
the front of the vertical part, to which it is connected by a constricted neck. It
presents five surfaces, which enclose an air cell. Of these surfaces, three are articu-
lar and two non-articular. The articular surfaces are: (1) the anterior or maxillary,
•directed forward, lateralward, and downward, of an oblong form, and rough for
articulation with the maxilla; (2) the posterior or sphenoidal, directed backward,
upward, and medialward; it presents the opening of the air cell, which usually
communicates with the sphenoidal sinus; the margins of the opening are serrated
for articulation with the sphenoidal concha; (3) the medial or ethmoidal, directed
forward, articulates with the labvrinth of the ethmoid. In some cases the air
cell opens on this surface of the bone and then communicates with the posterior
ethmoidal cells. j\Iore rarely it opens on both surfaces, and then communicates
with the posterior ethmoidal cells and the sphenoidal sinus. The non-articular
surfaces are: (1) the superior or orbital, directed upward and lateralward; it is
triangular in shape, and forms the back part of the floor of the orbit; and (2) the
lateral, of an oblong form, directed toward the pterygopalatine fossa; it is separated
THE INFERIOR NASAL CONCHA 169
from the orbital surface by a rounded border, which enters into the formation of
the inferior orbital fissure.
The Sphenoidal Process (proces.ms spheuoidalis).— The sphenoidal process is
a thin, compressed plate, much smaller than the orbital, and directed upward
and medialward. It presents three surfaces and two borders. The superior surface
articulates with the root of the pterygoid process and the under surface of the
sphenoidal concha, its medial border reaching as far as the ala of the vomer; it
presents a groove which contributes to the formation of the pharyngeal canal.
The medial surface is concave, and forms part of the lateral wall of the nasal cavity.
The lateral surface is divided into an articular and a non-articular portion: the
former is rough, for articulation with the medial pterygoid plate; the latter is
smooth, and forms part of the pterygopalatine fossa. The anterior border forms
the posterior boundary of the sphenopalatine notch. The posterior border, ser-
rated at the expense of the outer table, articulates with the medial pterygoid
plate.
The orbital and sphenoidal processes are separated from one another by the
sphenopalatine notch. Sometimes the two processes are united above, and form
between them a complete foramen (Fig. 1()8), or the notch may be crossed by one
or more spicules of bone, giving rise to two or more foramina.
Ossification. — The palatine bone is ossified in membrane from a single center, which makes
its appearance about the sixth or eighth week of fetal life at the angle of junction of the two parts
of the bone. From this point ossification spreads medialward to the horizontal part, downward
into the pyramidal process, and upward into the vertical part. Some authorities describe the
bone as ossifying from four centers: one for the pyramidal process and portion of the vertical
part behind the pterygopalatine groove; a second for the rest of the vertical and the horizontal
parts; a third for the orbital, and a fourth for the sphenoidal process. At the time of birth the
height of the vertical part is about equal to the transverse width of the horizontal part, whereas
in the adult the former measures about twice as much as the latter.
Articulations. — The palatine articulates with six bones: the sphenoid, ethmoid, maxilla,
inferior nasal concha, vomer, and opposite palatine.
The Inferior Nasal Concha (Concha Nasalis Inferior; Inferior Turbinated Bone).
The inferior nasal concha extends horizontally along the lateral wall of the
nasal cavity (Fig. 170) and consists of a lamina of spongy bone, curled upon itself
like a scroll. It has two surfaces, two borders, and two extremities.
The medial surface (Fig. 171) is convex, perforated by numerous apertures,
and traversed by longitudinal grooves for the lodgement of vessels. The lateral
surface is concave (Fig. 172), and forms part of the inferior meatus. Its upper
border is thin, irregular, and connected to various bones along the lateral wall
of the nasal cavity. It may be divided into three portions: of these, the anterior
articulates with the conchal crest of the maxilla; the posterior with the conchal
crest of the palatine; the middle portion presents three well-marked processes,
which vary much in their size and form. Of these, the anterior or lacrimal process
is small and pointed and is situated at the junction of the anterior fourth with
the posterior three-fourths of the bone: it articulates, by its apex, with the descend-
ing process of the lacrimal bone, and, by its margins, with the groove on the back
of the frontal process of the maxilla, and thus assists in forming the canal for the
nasolacrimal duct. Behind this process a broad, thin plate, the ethmoidal process,
ascends to join the uncinate process of the ethmoid; from its lower border a thin
lamina, the maxillary process, curves downward and lateralward; it articulates
with the maxilla and forms a part of the medial wall of the maxillary sinus. The
inferior border is free, thick, and cellular in structure, more especially in the middle
of the bone. Both extremities are more or less pointed, the posterior being the
more tapering.
170
OSTEOLOGY
Ossification. — The inferior nasal concha is ossified from a single center, which appears about
the fifth month of fetal hfe in the lateral wall of the cartilaginous nasal capsule.
Articulations. — The inferior nasal concha articulates with four bones: the ethmoid, maxilla,
lacrimal, and palatine.
Uncinate
process
oj ethmoid
Frontal sinus
Crista galli
Sella turcica
Openings into
maxilla ry sinus
Medial pterygoid plate
Pterygoid hamulus
Fig. 170. — Lateral wall of right nasal cavity showing inferior concha in situ.
FiQ. 171. — Right inferior nasal concha.
Medial surface.
Fig. 172.-
-Right inferior nasal concha.
Lateral surface.
The Vomer.
The vomer is situated in the median plane, but its anterior portion is frequently
bent to one or other side. It is thin, somewhat quadrilateral in shape, and forms
the hinder and lower part of the nasal septum (Fig. 173) ; it has two surfaces and
four borders. The surfaces (Fig. 174) are marked by small furrow^s for blood-
vessels, and on each is the nasopalatine groove, which runs obliquely downward
and forward, and lodges the nasopalatine nerve and vessels. The superior border,
the thickest, presents a deep furrow, bounded on either side by a horizontal pro-
jecting ala of bone; the furrow receives the rostrum of the sphenoid, while the
margins of the alse articulate with the vaginal processes of the medial pterygoid
plates of the sphenoid behind, and with the sphenoidal processes of the palatine
bones in front. The inferior border articulates with the crest formed bv the maxillae
THE VOMER
171
and palatine bones. The anterior border is the longest and slopes downward and
forward. Its upper half is fused with the perpendicular plate of the ethmoid;
its lower half is grooved for the inferior margin of the septal cartilage of the nose.
The posterior border is free, concave, and separates the choanse. It is thick and
bifid above, thin below.
Crest of nasal hones
Frontal spine
Space for triangular
cartilage of septum
Crest of palatines
Crest of maxillae
Fig. 173. — Median wall of left nasal cavity showing vomer in situ.
Ossification. — At an early period the septum of the nose consists of a plate of cartilage, the
ethmovomerine cartilage. The postero-superior part of this cartilage is ossified to form the per-
pendicular plate of the ethmoid; its antero-inferior portion persists as the septal cartilage, while
the vomer is ossified in the membrane covering its postero-inferior part. Two ossific centers,
one on either side of the middle line, appear about the eighth week of fetal life in this part of
the membrane, and hence the vomer consists primarily of two lamellae. About the third month
Fig. 174. — The vomer.
Fig 175. — Vomer of infant.
these unite below, and thus a deep groove is formed in which the cartilage is lodged. As
growth proceeds, the union of the lamellae extends upward and forward, and at the same time the
intervening plate of cartilage undergoes absorption. By the age of puberty the lamellaj are almost
completely united to form a median plate, but evidence of the bilaminar origin of the bone is
seen in the everted alae of its upper border and the groove on its anterior margin.
172
OSTEOLOGY
Articulations.— The vomer articulates with six bones: two of the cranium, the sphenoid and
ethmoid; and four of the face, the two maxilte and the two palatine bones; it also articulates
with the septal cartilage of the nose.
The Mandible (Mandibula; Inferior Maxillary Bone; Lower Jaw).
The mandible, the largest and strongest bone of the face, serves for the reception
of the lower teeth. It consists of a curved, horizontal portion, the body, and two
perpendicular portions, the rami, which unite with the ends of the body nearly
at right angles.
The Body {corpus mandihulw). — ^The body is curved somewhat like a horseshoe,
and has two surfaces and two borders.
Surfaces. — The external surface (Fig. 176) is marked in the median line by a
faint ridge, indicating the symphysis or line of junction of the two pieces of which
the bone is composed at an early period of life. This ridge divides below and
encloses a triangular eminence, the mental protuberance, the base of which is de-
Coronoid process
Condyle
TEMrORALIS
Mental
protuberance
Groove for external
maxillary artery
Fig. 176. — Mandible. Outer surface. Side view.
pressed in the center but raised on either side to form the mental tubercle. On either
side of the symphysis, just below the incisor teeth, is a depression, the incisive
fossa, which gives origin to the jNIentalis and a small portion of the Orbicularis
oris. Below the second premolar tooth, on either side, midway between the upper
and lower borders of the body, is the mental foramen, for the passage of the mental
vessels and nerve. Running backward and upward from each mental tubercle
is a faint ridge, the oblique line, which is continuous with the anterior border of the
ramus; it affords attachment to the Quadratus labii inferioris and Triangularis;
the Platysma is attached below it.
The internal surface (Fig. 177) is concave from side to side. Xear the lower
part of the symphysis is a pair of laterally placed spines, termed the mental spines,
which give origin to the Genioglossi. Immediately below these is a second pair
of spines, or more frequently a median ridge or impression, for the origin of the
Geniohyoidei. In some cases the mental spines are fused to form a single eminence,
in others they are absent and their position is indicated merely by an irregularity
of the surface. Above the mental spines a median foramen and furrow are some-
times seen; they mark the line of union of the halves of the bone. Below the mental
THE MANDIBLE
173
spines, on either side of the middle line, is an oval depression for the attachment
of the anterior belly of the Digastricus. Extending upward and backward on either
side from the lo\yer part of the symphysis is the mylohyoid line, which gives origin
to the Mylohyoideus; the posterior part of this line, near the alveolar margin,
gives attachment to a small part of the Constrictor pharyngis superior, and to
the pterygomandilnilar raphe. Above the anterior part of this line is a smooth
triangular area against which the sublingual gland rests, and below the hinder
part, an oval fossa for the submaxillary gland.
Borders.— The superior or alveolar border, wider behind than in front, is hollowed
into cavities, for the reception of the teeth; these cavities are sixteen in number,
and vary in depth and size according to the teeth which they contain. To the
outer lip of the superior border, on either side, the Buccinator is attached as
far forward as the first molar tooth. The inferior border is rounded, longer than
the superior, and thicker in front than behind; at the point where it joins the
lower border of the ramus a shallow groove; for the external maxillary artery,
may be present.
^iyj^.^
hyoideus
Mylohyoid line
BODY
Fig. 177. — Mandible. Inner surface. Side view.
Genio-
glossics
The Ramus {ramus mandibulcp; perpendicular portion). — The ramus is quadri-
lateral in shape, and has two surfaces, four borders, and two processes.
Surfaces. — The lateral surface (Fig. ITO) is flat and marked by oblique ridges
at its lower part; it gives attachment throughout nearly the whole of its extent
to the Masseter. The medial surface (Fig. 177) presents about its center the oblique
mandibular foramen, for the entrance of the inferior alveolar vessels and nerve.
The margin of this opening is irregular; it presents in front a prominent ridge,
surmounted by a sharp spine, the lingula mandibulse, which gives attachment to
the sphenomandibular ligament; at its lower and back part is a notch from which
the mylohyoid groove runs obliquely downward and forward, and lodges the mylo-
hyoid vessels and nerve. Behind this groove is a rough surface, for the insertion
of the Pterygoideus internus. The mandibular canal runs obliquely downward
and forward in the ramus, and then horizontally forward in the body, where it
is placed under the alveoli and communicates with them by small openings. On
arriving at the incisor teeth, it turns back to communicate with the mental foramen,
giving off two small canals which run to the cavities containing the incisor teeth.
174 OSTEOLOGY
[n the posterior two-thirds of the bone the canal is situated nearer the internal
surface of the mandible; and in the anterior third, nearer its external surface. It
contains the inferior alveolar vessels and nerve, from which branches are dis-
tributed to the teeth. The lower border of the ramus is thick, straight, and con-
tinuous with the inferior border of the body of the bone. At its junction with the
posterior bonier is the angle of the mandible, which may be either inverted or everted
and is marked by rough, oblique ridges on each side, for the attachment of the
Masseter laterally, and the Pterygoideus internus medially; the stylomandibular
ligament is attached to the angle between these muscles. The anterior border is
thin above, thicker below, and continuous with the oblique line. The posterior
border is thick, smooth, rounded, and covered by the parotid gland. The upper
border is thin, and is surmounted by two processes, the coronoid in front and the
condyloid behind, separated by a deep concavity, the mandibular notch.
The Coronoid Process {processus coronoideus) is a thin, triangular eminence,
which is flattened from side to side and varies in shape and size. Its anterior
border is convex and is continuous below with the anterior border of the ramus;
its posterior border is concave and forms the anterior boundary of the mandibular
notch. Its lateral surface is smooth, and affords insertion to the Temporalis and
^Slasseter. Its medial surface gives insertion to the Temporalis, and presents
a ridge which begins near the apex of the process and runs downward and forward
to the inner side of the last molar tooth. Between this ridge and the anterior
border is a grooved triangular area, the upper part of which gives attachment
to the Temporalis, the lower part to some fibers of the Buccinator.
The Condyloid Process (processus condyloideus) is thicker than the coronoid,
and consists of two portions: the condyle, and the constricted portion which sup-
ports it, the neck. The condyle presents an articular surface for articulation with
the articular disk of the temporomandibular joint; it is convex from before back-
ward and from side to side, and extends farther on the posterior than on the ante-
rior surface. Its long axis is directed medialward and slightly back^vard, and if
prolonged to the middle line will meet that of the opposite condyle near the ante-
rior margin of the foramen magnum. At the lateral extremity of the condyle
is a small tubercle for the attachment of the temporomandibular ligament. The
neck is flattened from before backward, and strengthened by ridges which descend
from the forepart and sides of the condyle. Its posterior surface is convex; its
anterior presents a depression for the attachment of the Pterygoideus externus.
The mandibular notch, separating the two processes, is a deep semilunar depres-
sion, and is crossed by the masseteric vessels and nerve.
Ossification. — The mandible is ossified in the fibrous membrane covering the outer sm-faces
of ^Meckel's cartilages. These cartilages form the cartilaginous bar of the mandibular arch (see
p. 66), and are two in number, a right and a left. Their proximal or cranial ends are connected
with the ear capsules, and their distal extremities are joined to one another at the symphysis
by mesodermal tissue. They run forward immediately below the condyles and then, bending
downward, lie in a groove near the lower border of the bone; in front of the canine tooth they
' incline upward to the symphysis. From the proximal end of each cartilage the malleus and
incus, two of the bones of the middle ear, are developed; the next succeeding portion, as far as
the lingula, is replaced by fibrous tissue, which persists to form the sphenomandibular hgament.
Between the Mngula and the canine tooth the cartilage disappears, while the portion of it below
and behind the incisor teeth becomes ossified and incorporated with this part of the mandible.
Ossification takes place in the membrane covering the outer surface of the ventral end of
Meckel's cartilage (Figs. 178 to 181), and each half of the bone is formed from a single center
which appears, near the mental foramen, about the sLxth week of fetal hfe. By the tenth week
the portion of Meckel's cartilage which lies below and behind the incisor teeth is surrounded and
invaded by the membrane bone. Somewhat later, accessory nuclei of cartilage make their appear-
ance, viz., a wedge-shaped nucleus in the condyloid process and extending downwai'd through
the ramus; a small strip along the anterior border of the coronoid process; and smaller nuclei
in the front part of both alveolar walls and along the front of the lower border of the bone. These
accessory nuclei possess no separate ossific centers, but are invaded by the surrounding membrane
THE MANDIBLE
175
bone and undergo absorption The inner alveolar border, usually described as arising from a
separate ossific center [svlemal center), is formed in the human mandible by an ingrowth from
the main mass of the bone. At birth the bone consists of two parts, united by a fibrous symphysis,
in which ossmcation takes place during the first year.
The foregoing description of the ossification of the mandible is based on the researches of
Lowi and t awcett,^ and differs somewhat from that usually given.
Articulations.— The mandible articulates with the two temporal bones.
Mental nerve
Lingual nerve
Inf. alveolar n.
Mylohyoid nerve
Fig. 178. — Mandible of human embryo 24 mm.
long. Outer aspect. (From model by Low.)
Mandibular nerve
Meckel's cartilage
111*
Stapes
Facial nerve
Mylohyoid nerve
Chorda tympani
RcicherVs cartilage
FiQ. 179. — Mandible of human embryo 24 mm. long.
Inner aspect. (From modnl by Low.)
Mental nerve
Anterior process of malleus
Fig. 180. — Mandible of human embryo 95 mm. long. Outer aspect. Nuclei of cartilage stippled.
, (From model by Low.)
Auriculotemporal nerve
Lingual nerve
Meckel's
cartilage
Ant. process of malleus
Chorda tympani
Symphysis Mylohyoid nerve
Fig. 181. — Mandible of human embryo 95 mm. long. Inner aspect. Nuclei of cartilage stippled.
(From model by Low.)
CHANGES PRODUCED IX THE MANDIBLE BY AGE.
At birth (Fig. 182) the body of the bone is a mere shell, containing the sockets of the two
incisor, the canine, and the two deciduous molar teeth, imperfectly partitioned off from one
another. The mandibular canal is of large size, and runs near the lower border of the bone; the
mental foramen opens beneath the socket of the first deciduous molar tooth. The angle is obtuse
(175°), and the condyloid portion is nearly in fine with the body. The coronoid process is of
comparatively large size, and projects above the level of the condyle.
' Proceedings of the Anatomical and .\nthropological Society of the University of Aberdeen, 1905, and Journal of
Anatomy and Physiology, vol. xliv.
' Journal of the -American Medical Association, September 2, 1905.
17G
OSTEOLOGY
Fi3. 182. — At birth.
Fig. 183. — In childhood.
Fig. 184.— In the adult.
Fig. 185.— In old age.
Side view of the mandible at different periods of life.
THE HYOID BONE
177
After birth (Fig. 183) the two segments of the bone become joined at the symphysis, from
below upward, m the first year; but a trace of separation may be visible in the beginning of the
second year, near the a veolar margin. The body becomes elongated in its whole length, but
more especially behind the mental foramen, to provide space for the three additional teeth devel-
oped in this part. The depth of the body increases owing to increased growth of the alveolar
part to afford room for the roots of the teeth, and by thickening of the subdental portion which
enables the jaw to withstand the powerful action of the masticatory muscles; but the alveolar
portion IS the deeper of the two, and, consequently, the chief part of the body lies above the
obhque line The mandibular canal, after the second dentition, is situated just above the level
of the mylohyoid line; and the mental foramen occupies the position usual to it in the adult
The angle becomes less obtuse, owing to the separation of the jaws by the teeth; about the fourth
year it is 140 .
In the adult (Fig. 184) the alveolar and subdental portions of the body are usually of equal
depth. The mental foramen opens midway between the upper and lower borders of the bone
and the mandibular canal runs nearly paraUel with the mylohyoid line. The ramus is ahnost
vertical in direction, the angle measuring from 110° to 120°.
In old age (Fig. 1S5) the bone becomes greatly reduced in size, for with the loss of the teeth
the alveolar process is absorbed, and, consequently, the chief part of the bone is below the obhque
line. The mandibular canal, with the mental foramen opening from it, is close to the alveolar
border. The ramus is oblique in direction, the angle measures about 140°, and the neck of the
condyle is more or less bent backward.
►
Constrictor Pharysgis Medius^
HvOGLOSSUSn
Lesser cornu Chondroglossus ,
V Genioglossus * #\ /
)J\'/
The Hyoid Bone (Os Hyoideum; Lingual Bone).
The hyoid bone is shaped like a horseshoe, and is suspended from the tips of the
styloid processes of the temporal bones by the stylohyoid ligaments. It consists
of five segments, viz., a body, two greater cornua, and two lesser cornua.
The Body or Basihyal {corpus oss. h y aide i).— The body or central part is
of a quadrilateral form. Its anterior surface (Fig. 186) is'convex and directed
forward and upward. It is crossed in its upper half by a well-marked transverse
ridge with a slight downward
convexit>', and in many cases ^n^, ^Greater comu
a vertical median ridge divides
it into two lateral halves.
The portion of the vertical
ridge above the transverse line
is present in a majority of
specimens, but the lower por-
tion is evident only in rare
cases. The anterior surface
gives insertion to the Genio-
hyoideus in the greater part
of its extent both above and
below the transverse ridge; a
portion of the origin of the
Hyoglossus notches the lateral
margin of the Geniohyoideus attachment. Below the transverse ridge the IMylo-
hyoideus, Sternohyoideus, and Omohyoideus are inserted. The posterior surface is
smooth, concave, directed backward and downward, and separated from the epi-
glottis by the hyothyroid membrane and a quantity of loose areolar tissue; a bursa
intervenes between it and the hyothyroid membrane. The superior border is
roimded, and gives attachment to the hyothyroid membrane and some aponeurotic
fibers of the Genioglossus. The inferior border affords insertion medially to the
Sternohyoideus and laterally to the Omohyoideus and occasionally a portion of the
Thyreohyoideus. It also gives attachment to the Levator glandulse thyreoidese,
when this muscle is present. In early life the lateral borders are connected to
the greater cornua by synchondroses; after middle life usually by bony union.
12
Body
DIGASTRICUS <fc
STYLOHYOIDEUS
TllYKEOHYOIDElS
Omohyoideus
/ Mylohtoidecs Sternohyoideus
Geniohyoideus
Fig. 186. — Hyoid bone. Anterior surface. Enlarged.
178 OSTEOLOGY
The Greater Cornua or Thyrohyals {cornua majora). — The greater cornua
project backward from the lateral borders of the body; they are flattened from
above downward and diminish in size from before backward; each ends in a tubercle
to which is fixed the lateral hyothyroid ligament. The upper surface is rough
close to its lateral border, for muscular attachments: the largest of these are the
origins of the Hyoglossus and Constrictor pharyngis medius which extend along
the whole length of the cornu; the Digastricus and Stylohyoideus have small
insertions in front of these near the junction of the body with the cornu. To the
medial border the hyothyroid membrane is attached, while the anterior half of the
lateral border gives insertion to the Thyreohyoideus.
The Lesser Cornua or Ceratohyals (cornua minora). — The lesser cornu are two
small, conical eminences, attached by their bases to the angles of junction between
the body and greater cornua. The>' are connected to the body of the bone by fibrous
tissue, and occasionally to the greater cornua by distinct diartlirodial joints,
which usually persist throughout life, but occasionally become ankylosed.
The lesser cornua are situated in the line of the transverse ridge on the body
and appear to be morphological continuations of it (Parsons^). The apex of each
cornu gives attachment to the stylohyoid ligament;- the Chondroglossus rises
from the medial side of the base.
Ossification. — The hyoid is ossified from six centers: two for the body, and one for each cornu.
Ossification commences in the greater cornua toward the end of fetal Hfe, in the body sliortl}'
afterward, and in the lesser cornua during the first or second year after birth.
THE EXTERIOR OF THE SKULL.
The skull as a whole may be viewed from different points, and the views so
obtained are termed the normse of the skull; thus, it may be examined from above
(norma verticalis), from below (norma basalis), from the side (norma lateralis),
from behind (norma occipitalis), or from the front (norma frontalis).
Norma Verticalis. — \Yhen viewed from above the outline presented varies
greatly in different skulls; in some it is more or less oval, in others more nearly
circular. The surface is traversed by three sutures, viz.: (1) the coronal sutures,
nearly transverse in direction, between the frontal and parietals; (2) the sagittal
sutm-es, medially placed, between the parietal bones, and deeply serrated in its
anterior two-thirds; and (3) the upper part of the lambdoidal suture, between the
parietals and the occipital. The point of junction of the sagittal and coronal suture
is named the bregma, that of the sagittal and lambdoid sutures, the lambda; they
indicate respectively the positions of the anterior and posterior fontanelles in the
fetal skull. On either side of the sagittal suture are the parietal eminence and parietal
foramen — the. latter, however, is frequently absent on one or both sides. The
skull is often somewhat flattened in the neighborhood of the parietal foramina,
and the term obelion is applied to that point of the sagittal suture which is on
a level with the foramina. In front is the glabella, and on its lateral aspects are
the superciliary arches, and above these the frontal eminences. Immediately above
the glabella may be seen the remains of the frontal suture ; in a small percentage
of skulls this suture persists and extends along the middle line to the bregma.
Passing backward and upward from the zygomatic processes of the frontal bone
are the temporal lines, which mark the upper limits of the temporal fossae. The
zygomatic arches may or may not be seen projecting beyond the anterior portions
of these lines.
•See article on "The Topography and Morphology of the Human Hyoid Bone," bv F. G. Parsons, Journal of
Anatomy and Physiology, vol. xliii.
2 These ligaments in many animals are distinct bones, and in man may imdergo partial ossification.
THE EXTERIOR OF THE SKULL
179
Norma BasaUs (Fig. 187).— The inferior surface of the base of the skull, exclu-
sive of the mandible, is bounded in front by the incisor teeth in the maxilla?; behind,
Incisors
CaniTie
Incisive canal
Traiismils left nasopalatine nerve
Traiijimits dencendiiuj palatine vesseh
Transmita right nasopalatine nerve
Lesser palatine foramina
Posterior iiasal spine
Musculus uvulae
Pterygoid hamulus
Sphenoidal process of palatine
Pharyngeal canal
Tensor tympani
Pharyngeal tubercle
Situation of auditory tuhe and
semicanal for Tensor tympani
Tensor veli palatini
Inferior tympanic caiuxliculus
Aqnaeduclus cochleae
Jugular foramen
Slastoid canalimlus
Tympanomastoid fissure
Fig. 187. — Base of skull. Inferior surface.
180 OSTEOLOGY
by the superior nuchal lines of the occipital; and laterally by the alveolar arch,
the lower border of the zygomatic bone, the zygomatic arch and an imaginary
line extending from it to the mastoid process and extremity of the superior nuchal
line of the occipital. It is formed by the palatine processes of the maxillae and
palatine bones, the vomer, the pterygoid processes, the under surfaces of the
great wings, spinous processes, and part of the body of the sphenoid, the under
surfaces of the squamae and mastoid and petrous portions of the temporals, and
the under surface of the occipital bone. The anterior part or hard palate projects
below the level of the rest of the surface, and is bounded in front and laterally
by the alveolar arch containing the sixteen teeth of the maxillae. Immediately
behind the incisor teeth is the incisive foramen. In this foramen are two lateral
apertures, the openings of the incisive canals {foramina of Stenson) which transmit
the anterior branches of the descending palatine vessels, and the nasopalatine
nerves. Occasionally two additional canals are present in the incisive foramen;
they are termed the foramina of Scarpa and are situated in the middle line; when
present they transmit the nasopalatine nerves. The vault of the hard palate
is concave, uneven, perforated by numerous foramina, marked by depressions for
the palatine glands, and traversed by a crucial suture formed by the junction of the
four bones of which it is composed. In the young skull a suture may be seen ex-
tending on either side from the incisive foramen to the interval between the lateral
incisor and canine teeth, and marking off the os incisivum or premaxillary bone.
At either posterior angle of the hard palate is the greater palatine foramen, for the
transmission of the descending palatine vessels and anterior palatine nerve; and
running forward and medialward from it a groove, for the same vessels and nerve.
Behind the posterior palatine foramen is the pyramidal process of the palatine bone,
perforated by one or more lesser palatine foramina, and marked by the commence-
ment of a transverse ridge, for the attachment of the tendinous expansion of the
Tensor veli palatini. Projecting backward from the center of the posterior border
of the hard palate is the posterior nasal spine, for the attachment of the jNIuscuIus
uvulae. Behind and above the hard palate are the choanae, measuring about
2.5 cm. in their vertical and 1.25 cm. in their transverse diameters. They are
separated from one another by the vomer, and each is bounded above by the body
of the sphenoid, below by the horizontal part of the palatine bone, and laterally
by the medial pterygoid plate of the sphenoid. At the superior border of the
vomer may be seen the expanded alae of this bone, receiving between them the ros-
trum of the sphenoid. Near the lateral margins of the alae of the vomer, at the
roots of the pterygoid processes, are the phar3aigeal canals. The pterygoid process
presents near its base the pterygoid canal, for the transmission of a nerve and artery.
The medial pterygoid plate is long and narrow ; on the lateral side of its base is the
scaphoid fossa, for the origin of the Tensor veli palatini, and at its lower extremity
the hamulus, around which the tendon of this muscle turns. The lateral pterygoid
plate is broad; its lateral surface forms the medial boundary of the infratemporal
fossa, and affords attachment to the Pterygoideus externus.
Behind the nasal cavities is the basilar portion of the occipital bone, presenting
near its center the pharyngeal tubercle for the attachment of the fibrous raphe
of the pharynx, with depressions on either side for the insertions of the Rectus
capitis anterior and Longus capitis. At the base of the lateral pterygoid plate
is the foramen ovale, for the transmission of the mandibular nerve, the accessorv
meningeal artery, and sometimes the lesser superficial petrosal nerve ; behind this are
the foramen spinosum which transmits the middle meningeal vessels, and the promi-
nent spina angularis {sphenoidal spine), which gives attachment to the spheno-
mandibular ligament and the Tensor veli palatini. Lateral to the spina angularis
is the mandibular fossa, divided into two parts by the petrotympanic fissure; the
anterior portion, concave, smooth, bounded in front hv the articular tubercle,
THE EXTERIOR OF THE SKULL 181
serves for the articulation of the condyle of the mandible; the posterior portion,
rough and bounded behind by the tympanic part of the temporal, is sometimes
occupied by a part of the parotid gland. Emerging from between the laminae
of the vaginal process of the t\mpanic part is the styloid process; and at the base
of this process is the stylomastoid foramen, for the exit of the facial nerve, and
entrance of the stylomastoid artery. Lateral to the stylomastoid foramen, between
the tympanic part and the mastoid process, is the tympanomastoid fissure, for the
auricular branch of the vagus. Upon the medial side of the mastoid process is
the mastoid notch for the posterior belly of the Digastricus, and medial to the notch,
the occipital groove for the occipital artery. At the base of the medial pterygoid
plate is a large and somewhat triangular aperture, the foramen lacerum, bounded
in front by the great wing of the sphenoid, behind by the apex of the petrous
portion of the temporal bone, and medially by the body of the sphenoid and basilar
portion of the occipital bone; it presents in front the posterior orifice of the ptery-
goid canal ; behind, the aperture of the carotid canal. The lower part of this opening
IS filled up in the fresh state by a fibrocartilaginous plate, across the upper or
cerebral surface of which the internal carotid artery passes. Lateral to this aperture
is a groove, the sulcus tubse auditivse, between the petrous part of the temporal and
the great wing of the sphenoid. This sulcus is directed lateralward and backward
from the root of the medial pterygoid plate and lodges the cartilaginous part of the
auditory tube; it is continuous behind with the canal in the temporal bone which
forms the bony part of the same tube. At the bottom of this sulcus is a narrow
cleft, the petrosphenoidal fissure, which is occupied, in the fresh condition, by a
plate of cartilage. Behind this fissure is the under surface of the petrous portion
of the temporal bone, presenting, near its apex, the quadrilateral rough surface,
part of Avhich affords attachment to the Levator veli palatini ; lateral to this surface
is the orifice of the carotid canal, and medial to it, the depression leading to the
aquseductus cochleae, the former transmitting the internal carotid artery and the
carotid plexus of the sympathetic, the latter serving for the passage of a vein from
the cochlea. Behind the carotid canal is the jugular foramen, a large aperture,
formed in front by the petrous portion of the temporal, and behind by the occipital;
it is generally larger on the right than on the left side, and may be subdivided
into three compartments. The anterior compartment transmits the inferior
petrosal sinus; the intermediate, the glossopharyngeal, vagus, and accessory
nerves; the posterior, the transverse sinus and some meningeal branches from the
occipital and ascending pharyngeal arteries. On the ridge of bone dividing the
carotid canal from the jugular foramen is the inferior tympanic canaliculus for
the transmission of the tympanic branch of the glossopharyngeal nerve; and on the
wall of the jugular foramen, near the root of the styloid process, is the mastoid
canaliculus for the passage of the auricular branch of the vagus nerve. Extending
forward from the jugular foramen to the foramen lacerum is the petrooccipital fissure
occupied, in the fresh state, by a plate of cartilage. Behind the basilar portion
of the occipital bone is the foramen magnum, bounded laterally by the occipital
condyles, the medial sides of which are rough for the attachment of the alar
ligaments. Lateral to each condyle is the jugular process which gives attachment
to the Rectus capitis lateralis muscle and the lateral atlantooccipital ligament.
The foramen magnum transmits the medulla oblongata and its membranes, the
accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries,
and the ligaments connecting the occipital bone with the axis. The mid-points
on the anterior and posterior margins of the foramen magnum are respectively
termed the basion and the opisthion. In front of each condyle is the canal for the
passage of the hypoglossal nerve and a meningeal artery. Behind each condyle
is the condyloid fossa, perforated on one or both sides by the condyloid canal, for
the transmission of a vein from the transverse sinus. Behind the foramen magnum
182
OSTEOLOGY
is the median nuchal Une ending above at the external occipital protuberance, while
on either side are the superior and inferior nuchal lines; these, as well as the surfaces
of bone between them, are rough for the attachment of the muscles which are
enumerated on pages 129 and 130.
Norma Lateralis (Fig. 188).— When viewed from the side the skull is seen to
consist of the cranium above and behind, and of the face below and in front. The
cranium is somewhat ovoid in shape, but its contour varies in different cases and
depends largely on the length and height of the skull and on the degree of promi-
nence of the superciliary arches and frontal eminences. Entering into its formation
are the frontal, the parietal, the occipital, the temporal, and the great wing of the
Fig. 188. — Side view of the skull.
sphenoid. These bones are joined to one another and to the zygomatic b\' the follow-
ing sutures: the zygomaticotemporal between the zygomatic process of the temporal
and the temporal process of the zygomatic ; the zygomaticofrontal uniting the zygo-
matic bone with the zygomatic process of the frontal; the sutures surrounding the
great wing of the sphenoid, viz., the sphenozygomatic in front, the sphenofrontal
and sphenoparietal above, and the sphenosquamosal behind. The sphcnoj^arietal
suture varies in length in different skulls, and is absent in those cases where the
frontal articulates with the temporal squama. The point corresponding with the
posterior end of the sphenoparietal suture is named the pterion; it is situated about
3 cm. behind, and a little above the level of the zygomatic process of the frontal
bone.
THE EXTERIOR OF THE SKULL 183
The squamosal suture arches backward from the pterion and connects the tem-
poral squama with the lower border of the parietal: this suture is continuous
behind with the short, nearly horizontal parietomastoid suture, which unites the
mastoid process of the temporal with the region of the mastoid angle of the parietal.
Extending from above downward and forward across the cranium are the coronal
and lambdoidal sutiires; the former connects the parietals with the frontal, the latter,
the parietals with the occipital. The lambdoidal suture is continuous below with
the occipitomastoid suture between the occipital and the mastoid portion of the
temporal. In or near the last suture is the mastoid foramen, for the transmission
of an emissary vein. The point of meeting of the parietomastoid, occipitomastoid,
and lambdoidal sutures is known as the asterion. Immediately above the orbital
margin is the superciliary arch, and, at a higher level, the frontal eminence. Near
the center of the parietal bone is the parietal eminence. Posteriorly is the ex-
ternal occipital protuberance, from which the sujjerior nuchal line may be followed
forward to the mastoid process. Arching across the side of the cranium are the
temporal lines, which mark the upper limit of the temporal fossa.
The Temporal Fossa {jossa temporalis) .—The temporal fossa is bounded above
and behind by the temporal lines, which extend from the zygomatic process of the
frontal bone upward and backward across the frontal and parietal bones, and then
curve downward and forward to become continuous with the supramastoid crest
and the posterior root of the zygomatic arch. The point where the upper temporal
line cuts the coronal suture is named the stephanion. The temporal fossa is bounded
in front by the frontal and zygomatic bones, and opening on the back of the latter
is the zygomaticotemporal foramen. Laterally the fossa is limited by the zygomatic
arch, formed by the zygomatic and temporal bones; below, it is separated from the
infratemporal fossa by the infratemporal crest on the great wing of the sphenoid,
and by a ridge, continuous with this crest, which is carried backward across the
temporal squama to the anterior root of the zygomatic process. In front and
below, the fossa communicates with the orbital cavity through the inferior orbital
or sphenomaxillary fissure. The floor of the fossa is deeply concave in front and
convex behind, and is formed by the zygomatic, frontal, parietal, sphenoid, and
temporal bones. It is traversed by vascular furrows; one, usually well-marked, runs
upward above and in front of the external acoustic meatus, and lodges the middle
temporal artery. Two others, frequently indistinct, may be observed on the
anterior part of the floor, and are for the anterior and posterior deep temporal
arteries. The temporal fossa contains the Temporalis muscle and its vessels and
nerves, together with the zygomaticotemporal nerve.
The zygomatic arch is formed by the zygomatic process of the temporal and
the temporal process of the zygomatic, the two being united by an oblique suture;
the tendon of the Temporalis passes medial to the arch to gain insertion into the
coronoid process of the mandible. The zygomatic process of the temporal arises
by two roots, an anterior, directed inward in front of the mandibular fossa, where
it expands to form the articular tubercle, and a posterior, which runs backward
above the external acoustic meatus and is continuous with the supramastoid
crest. The upper border of the arch gives attachment to the temporal fascia;
the lower border and medial surface give origin to the IMasseter.
Below the posterior root of the zygomatic arch is the elliptical orifice of the
external acoustic meatus, bounded in front, below, and behind by the tympanic
part of the temporal bone; to its outer margin the cartilaginous segment of the
external acoustic meatus is attached. The small triangular area between the
posterior root of the zygomatic arch and the postero-superior part of the orifice is
termed the suprameatal triangle, on the anterior border of which a small spinous
process, the suprameatal spine, is sometimes seen. Between the tympanic part
and the articular tubercle is the mandibular fossa, divided into two parts by the
184
OSTEOLOGY
petrotympanic fissure. The anterior and larger part of the fossa articulates with
the condyle of the mandible and is limited behind by the external acoustic meatus:
the posterior part sometimes lodges a portion of the parotid gland. The styloid
process extends downward and forward for a variable distance from the lower
part of the tympanic part, and gives attachment to the Styloglossus, Stylohy-
oideus, and Stjdopharyngeus, and to the stylohyoid and stylomandibular ligaments.
Projecting downward behind the external acoustic meatus is the mastoid process,
to the outer surface of which the Sternocleidomastoideus, Splenius capitis, and
Longissimus capitis are attached.
The Infratemporal Fossa {fossa mfratemyoralis; zygomatic fossa) (Fig. 189).— The
infratemporal fossa is an irregularly shaped cavity, situated below and medial to the
zygomatic arch. It is bounded, in front, by the infratemporal surface of the maxilla
FropJra^
1 Parietal .
■/eat
i SquaT?::y
-^
Inferior orbital fissure \
Infratemporal crest
Pterygomaxillary fissure
r teu^pr. ;.' ■
Pterygoid hamulus
FiQ. 189. — Left infratemporal fossa.
_>^
External acoustic meatus
Tympanic part of temporal
Styloid process
Mandibular cavity
Zygomatic process [cut)
Lateral pterygoid plate
and the ridge which descends from its zygomatic process; behind, by the articular
tubercle of the temporal and the spina angularis of the sphenoid ; cr6oi'e, by the great
wing of the sphenoid below the infratemporal crest, and by the under surface of
the temporal squama; below, by the alveolar border of the maxilla; medially, by
the lateral pterygoid plate. It contains the lower part of the Temporalis, the
Pterygoidei internus and externus, the internal maxillary vessels, and the man-
dibular and maxillary nerves. The foramen ovale and foramen spinosum open on
its roof, and the alveolar canals on its anterior wall. At its upper and medial
part are two fissures, which together form a T-shaped fissure, the horizontal limb
being named the inferior orbital, and the vertical one the pterygomaxillary.
The inferior orbital fissure (fissura orbitalis inferior; sphenomaxillary fissure),
horizontal in direction, opens into the lateral and back part of the orbit. It is
bounded above by the lower border of the orbital surface of the great wing of the
^HE EXTERIOR OF THE SKULL 185
sphenoid; helow, by the lateral border of the orbital surface of the maxilla and the
orbital process of the palatine bone; laterally, by a small part of the zygomatic
bone ■} medially, it joins at right angles with the pterygomaxillary fissure. Through
the inferior orbital fissure the orbit communicates with the temporal, infratem-
poral, and pterygopalatine fossae; the fissure transmits the maxillary nerve and
its zygomatic branch, the infraorbital vessels, the ascending branches from the
sphenopalatine ganglion, and a vein which connects the inferior ophthalmic vein
with the pterygoid venous plexus.
The pterygomaxillary fissure is vertical, and descends at right angles from the
medial end of the preceding; it is a triangular interval, formed by the diver-
gence of the maxilla from the pterygoid process of the sphenoid. It connects
the infratemporal with the pterygopalatine fossa, and transmits the terminal part
of the internal maxillary artery.
The Pterygopalatine Fossa {fossa pterygopalatina; sphenomaxillary fossa). — The
pterygopalatine fossa is a small, triangular space at the angle of junction of the
inferior orbital and pterygomaxillary fissures, and placed beneath the apex of
the orbit. It is bounded above by the under surface of the body of the sphenoid
and by the orbital process of the palatine bone; in front, by the infratemporal
surface of the maxilla; behind, by the base of the pterygoid process and lower part
of the anterior surface of the great wing of the sphenoid; medially, by the vertical
part of the palatine bone with its orbital and sphenoidal processes. This fossa
communicates with the orbit by the inferior orbital fissure, with the nasal cavity
by the sphenopalatine foramen, and with the infratemporal fossa by the pterygo-
maxillary fissure. Five foramina open into it. Of these, three are on the posterior
wall, viz., the foramen rotundum, the pterygoid canal, and the pharyngeal canal,
in this order downward and medialward. On the medial wall is the sphenopalatine
foramen, and below is the superior orifice of the pterygopalatine canal. The fossa
contains the maxillary nerve, the sphenopalatine ganglion, and the terminal part
of the internal maxillar}^ artery.
Norma Occipitalis. — When viewed from behind the cranium presents a more
or less circular outline. In the middle line is the posterior part of the sagittal
suture connecting the parietal bones; extending downward and lateralward from
the hinder end of the sagittal suture is the deeply serrated lambdoidal suture join-
ing the parietals to the occipital and continuous below with the parietomastoid and
occipitomastoid sutures; it frequently contains one or more sutural l)ones. Near
the middle of the occipital squama is the external occipital protuberance or inion,
and extending lateralward from it on either side is the superior nuchal line, and
above this the faintly marked highest nuchal line. The part of the squama above
the inion and highest lines is named the planum occipitale, and is covered by the
Occipitalis muscle; the part below is termed the planum nuchale, and is divided
by the median nuchal line which runs downward and forward from the inion to the
foramen magnum; this ridge gives attachment to the ligamentum nuchse. The
muscles attached to the planum nuchale are enumerated on p. 130. Below and in
front are the mastoid processes, convex laterally and grooved medially by the
mastoid notches. In or near the occipitomastoid suture is the mastoid foramen for
the passage of the mastoid emissary vein.
Norma Frontalis (Fig. 190). — When viewed from the front the skull exliibits a
somewhat oval outline, limited above by the frontal bone, below by the body of the
mandible, and laterally by the zygomatic bones and the mandibular rami. The
upper part, formed by the frontal squama, is smooth and convex. The lower part,
made up of the bones of the face, is irregular; it is excavated laterally by the orbital
cavities, and presents in the middle line the anterior nasal aperture leading to the
' Occasionally the maxilla and the sphenoid articulate with each other at the anterior extremity of this fissure: the
zygomatic is then excluded from it.
186
OSTEOLOGY
nasal cavities, and below this the transverse slit between the upper and lower
dental arcades. Above, the frontal eminences stand out more or less prominently,
and beneath these are the superciliary arches, joined to one another in the middle
by the glabella. On and above the glabella a trace of the frontal suture sometimes
persists; beneath it is the frontonasal suture, the mid-point of which is termed the
nasion. Behind and below the frontonasal suture the frontal articulates with the
frontal process of the maxilla and with the lacrimal. Arching transversely below
the superciliary arches is the upper part of the margin of the orbit, thin and promi-
Supraorbital foramen
Superior orbital fissure
Lamina papyracea of ethmoid
Lacrimal
Inferior orbital fissure
Zygonmticofacial 'foramen
Infraorbital foramen
Nasal cavity
Inferior nasal concha
Mental foramen
Fig. 190.— The skull from the front.
nent in its lateral two-thirds, rounded in its medial third, and presenting, at the
junction of these two portions, the supraorbital notch or foramen for the supra-
orbital nerve and vessels. The supraorbital margin ends laterally in the zygomatic
process which articulates with the zygomatic bone, and from it the temporal line
extends upward and backward. Below the frontonasal suture is the bridge of the
nose, convex from side to side, concavo-convex from above downward, and formed
by the two nasal bones supported in the middle line by the perpendicular plate
of the ethmoid, and laterally by the frontal processes of the maxillae which are
prolonged upward between the nasal and lacrimal bones and form the lower and
THE EXTERIOR OF THE SKULL
187
medial part of the circumference of each orbit. Below the nasal bones and between
the maxilke is the anterior aperture of the nose, pyriform in shape, with the narrow
end directed upward. Laterally this opening is bounded by sharp margins, to
which the lateral and alar cartilages of the nose are attached; helow, the margins
are thicker and curve medialward and forward to end in the anterior nasal spine.
On looking into the nasal cavity, the bony septum which separates the nasal
cavities presents, in front, a large triangular deficiency; this, in the fresh state,
is filled up by the cartilage of the nasal septum; on the lateral wall of each nasal
cavity the anterior part of the inferior nasal concha is visible. Below and lateral
to the anterior nasal aperture are the anterior surfaces of the maxillee, each
perforated, near the lower margin of the orbit, by the infraorbital foramen for the
Nasal bone
Lacrfmal sulcus
Zygomatic hone
Maxilla
Ant. ethmoidal cells
Nasal septum
Probe in
infundibulum
Middle elhmx)idal cells
Superior 7iasal concha
Post, ethmoidal cells
Superior meatus
Sphenoidal sinuses
Infraorbital groove
Inferior orbital
fissure
Palatine bone
Sphenoidal bone
Foramen roiundum
Foramen ovale
_ Foramen spinosum
Carotid canal
Fig. 191. — Horizontal section of nasal and orbital cavities.
passage of the infraorbital nerve and vessels. Below and medial to this foramen
is the canine eminence separating the incisive from the canine fossa. Beneath
these fossae are the alveolar processes of the maxillae containing the upper teeth,
which overlap the teeth of the mandible in front. The zygomatic bone on either
side forms the prominence of the cheek, the lower and lateral portion of the orbital
cavity, and the anterior part of the zygomatic arch. It articulates medially with
the maxilla, behind with the zygomatic process of the temporal, and above with
the great wing of the sphenoid and the zygomatic process of the frontal; it is per-
forated by the zygomaticofacial foramen for the passage of the zygomaticofacial
nerve. On the body of the mandible is a median ridge, indicating the position
of the symphysis; this ridge divides below to enclose the mental protuberance, the
lateral angles of which constitute the mental tubercles. Below the incisor teeth
188
OSTEOLOGY
is the incisive fossa, and beneath the second premolar tooth the mental foramen
which transmits the mental nerve and vessels. The oblique line runs upward from
the mental tubercle and is continuous behind with the anterior border of the ramus.
The posterior border of the ramus runs downward and forward from the condyle
to the angle, which is frequently more or less everted.
The Orbits (orbitce) (Fig. 190). — The orbits are two quadrilateral pyramidal cavi-
ties, situated at the upper and anterior part of the face, their bases being directed
forward and lateralward, and their apices backward and medialward, so that their
long axes, if continued backward, would meet over the body of the sphenoid.
Each presents for examination a roof, a floor, a medial and a lateral wall, a base,
and an apex.
Anterior
ethmoidal foramen
Posterior ethmoidal foramen
Orbital 'process of pilatine
Optic foramen
Sphenopalatine foramen
Sella turcica
Probe in foramen rotundum
Fossa for
lacrimal sac
Uncinate process
of ethmoid
Openings of
maxillary sinns
Inferior nasal'
concha,
Probe in pterygoid cava
(^^Prdbe in pterygopalatine canal
/^^ Palatine hone
ml
Lateral pterygoid plate
Pyramidal process cf palatine
Fig. 192.— Medial wall of left orbit.
The roof is concave, directed downward, and slightly forward, and formed in
front by the orbital plate of the frontal; behind by the small wing of the sphenoid.
It presents medially the trochlear fovea for the attachment of the cartilaginous
pulley of the Obliquus oculi superior; laterally, the lacrimal fossa for the lacrimal
gland; and posteriorly, the suture between the frontal bone and the small wing
of the sphenoid. '
The floor is directed upward and lateralward, and is of less extent than the
roof; it is formed chiefly by the orbital surface of the maxilla; m front and laterally,
by the orbital process of the zygomatic bone, and behind and medially, to a small
extent, by the orbital process of the palatine. At its medial angle is the upper
opening of the nasolacrimal canal, immediately to the lateral side of which is a
depression for the origin of the Obliquus oculi inferior. On its lateral part is the
suture between the maxilla and zygomatic bone, and at its posterior part that
between the maxilla and the orbital process of the palatine. Running forward
near the middle of the floor is the infraorbital groove, ending in front in the infra-
orbital canal and transmitting the infraorbital nerve and vessels.
THE INTERIOR OF THE SKVLL 189
The medial wall (Fig. 192) is nearly vertical, and is formed from before back-
ward by the frontal process of the maxilla, the lacrimal, the lamina papyracea
of the ethmoid, and a small part of the body of the sphenoid in front of the optic
foramen. Sometimes the sphenoidal concha forms a small part of this wall (see
page 152). It exhibits three vertical sutures, viz., the lacrimomaxillary, lacrimo-
ethmoidal, and sphenoethmoidal. In front is seen the lacrimal groove, which lodges
the lacrimal sac, and behind the groove is the posterior lacrimal crest, from which
the lacrimal part of the Orbicularis oculi arises. At the junction of the medial
wall and the roof are the frontomaxillary, frontolacrimal, frontoethmoidal, and
sphenofrontal sutures. The point of junction of the anterior border of the lacrimal
with the frontal is named the dacryon. In the frontoethmoidal suture are the
anterior and posterior ethmoidal foramina, the former transmitting the nasociliary
nerve and anterior ethmoidal vessels, the latter the posterior ethmoidal nerve and
vessels.
The lateral wall, directed medialward and forward, is formed by the orbital
process of the zygomatic and the orbital surface of the great wing of the sphenoid;
these are united by the sphenozygomatic suture which terminates below at the
front end of the inferior orbital fissure. On the orbital process of the zygomatic
bone are the orbital tubercle (Whitnall) and the orifices of one or two canals which
transmit the branches of the zygomatic nerve. Between the roof and the lateral
wall, near the apex of the orbit, is the superior orbital fissure. Through this fissure
the oculomotor, the trochlear, the ophthalmic division of the trigeminal, and the
abducent nerves enter the orbital cavity, also some filaments from the cavernous
plexus of the sympathetic and the orbital branches of the middle meningeal artery.
Passing backward through the fissure are the ophthalmic vein and the recurrent
branch from the lacrimal artery to the dura mater. The lateral wall and the floor
are separated posteriorly by the inferior orbital fissure which transmits the maxillary
nerve and its zygomatic branch, the infraorbital vessels, and the ascending branches
from the sphenopalatine ganglion.
The base of the orbit, quadrilateral in shape, is formed above by the supra-
orbital arch of the frontal bone, in which is the supraorbital notch or foramen for
the passage of the supraorbital vessels and nerve; helow by the zygomatic bone and
maxilla, united by the zygomaticomaxillary suture; laterally by the zygomatic
bone and the zygomatic process of the frontal joined by the zygomaticofrontal
suture; medially by the frontal bone and the frontal process of the maxilla united
by the frontomaxillary suture.
The apex, situated at the back of the orbit, corresponds to the optic foramen^
a short, cylindrical canal, which transmits the optic nerve and ophthalmic artery.
It will thus be seen that there are nine openings communicating with each
orbit, viz., the optic foramen, superior and inferior orbital fissures, supraorbital
foramen, infraorbital canal, anterior and posterior ethmoidal foramina, zygomatic
foramen, and the canal for the nasolacrimal duct.
THE INTERIOR OF THE SKULL.
Inner Surface of the Skull-cap. — The inner surface of the skull-cap is concave
and presents depressions for the convolutions of the cerebrum, together with
numerous furrows for the lodgement of branches of the meningeal vessels. Along
the middle line is a longitudinal groove, narrow^ in front, where it commences at
the frontal crest, but broader behind; it lodges the superior sagittal sinus, and its
margins afford attachment to the falx cerebri. On either side of it are several
' Some anatomists describe ttie apex of the orbit as corresponding with tlie medial end of the superior orbital fissure.
It seems better, however, to adopt the statement in the text, since the ocular muscles take origin around the optic
foramen, and diverge from it to the bulb of the eye.
190 OSTEOLOGY
depressions for the arachnoid granulations, and at its back part, the openings of
the parietal foramina when these are present. It is crossed, in front, by the coronal
suture, and behind by the lambdoidal, while the sagittal lies in the medial plane
between the parietal bones.
Upper Surface of the Base of the Skull (Fig. 193). — The upper surface of the
base of the skull or floor of the cranial cavity presents three fossse, called the anterior,
middle, and posterior cranial fossae.
Anterior Fossa (fossa cranii anterior). — The floor of the anterior fossa is formed
by the orbital plates of the frontal, the cribriform plate of the ethmoid, and the
small wings and front part of the body of the sphenoid ; it is limited behind by the
posterior borders of the small wings of the sphenoid and by the anterior margin
of the chiasmatic groove. It is traversed by the frontoethraoidal, sphenoethmoidal,
and sphenofrontal sutures. Its lateral portions roof in the orbital cavities and sup-
port the frontal lobes of the cerebrum ; they are convex and marked by depressions
for the brain convolutions, and grooves for branches of the meningeal vessels.
The central portion corresponds with the roof of the nasal cavity, and is markedly
depressed on either side of the crista galli. It presents, in and near the median
line, from before backward, the commencement of the frontal crest for the attach-
ment of the falx cerebri; the foramen cecum, between the frontal bone and the crista
galli of the ethmoid, which usually transmits a small vein from the nasal cavity
to the superior sagittal sinus; behind the foramen cecum, the crista galli, the
free margin of which affords attachment to the falx cerebri; on either side of the
crista galli, the olfactory groove formed by the cribriform plate, which supports
the olfactory bulb and presents foramina for the transmission of the olfactory
nerves, and in front a slit-like opening for the nasociliary nerve. Lateral to either
olfactory groove are the internal openings of the anterior and posterior ethmoidal
foramina; the anterior, situated about the middle of the lateral margin of the olfac-
tory groove, transmits the anterior ethmoidal vessels and the nasociliary nerve; the
nerve nms in a groove along the lateral edge of the cribriform plate to the slit-like
opening above mentioned; the posterior ethmoidal foramen opens at the back part
of this margin under cover of the projecting lamina of the sphenoid, and transmits
the posterior ethmoidal vessels and nerve. Farther back in the middle line is the
ethmoidal spine, bounded behind b}' a slight elevation separating two shallow lon-
gitudinal grooves which support the olfactory lobes. Behind this is the anterior
margin of the chiasmatic groove, running lateralward on either side to the upper
margin of the optic foramen.
The Middle Fossa (fossa cranii media). — The middle fossa, deeper than the pre-
ceding, is narrow in the middle, and wide at the sides of the skull. It is bounded
in front by the posterior margins of the small wings of the sphenoid, the anterior
clinoid processes, and the ridge forming the anterior margin of the chiasmatic
groove; behind, by the superior angles of the petrous portions of the temporals
and the dorsum sellae; laterally by the temporal squamae, sphenoidal angles of the
parietals, and great wings of the sphenoid. It is traversed by the squamosal,
sphenoparietal, sphenosquamosal, and sphenopetrosal sutures.
The middle part of the fossa presents, in front, the chiasmatic groove and tuber-
culum sellae; the chiasmatic groove ends on either side at the optic foramen, which
transmits the optic nerve and ophthalmic artery to the orbital cavity. Behind
the optic foramen the anterior clinoid process is directed backward and medialward
and gives attachment to the tentorium cerebelli. Behind the tuberculum sellse
is a deep depression, the sella turcica, containing the fossa hypophyseos, which lodges
the hypophysis, and presents on its anterior wall the middle clinoid processes.
The sella turcica is bounded posteriorly by a quadrilateral plate of bone, the dorsum
sellae, the upper angles of which are surmounted by the posterior clinoid processes:
these afford attachment to the tentorium cerebelli, and below each is a notch for
THE INTERIOR OF THE SKULL
191
the abducent nerve. On either side of the sella turcica is the carotid groove, which
is broad, shallow, and curved somewhat like the italic letter /. It begins behind
Groove for super, sagittal sinus
Grooves for anter. meningeal vessels
Foramen ccecum-
Crista galli
Slit for nasociliary nerve
Groove/or naxociliary nerve
Anterior ethmoidal foramen
Orifices for olfactory nerves
Posterior ethmoidal foramen
Ethmoidal spine
Olfactory grooves
Optic foramen
Chiasmatic groove
Tuberculnm sellae
Anterior clinoid process
Middle clinoid process
Posterior clinoid process
Groove for abducent nerve
Foramen lacerum
Orifice of carotid canal
Depression for semilunar ganglion
Internal acoustic meatus
Slit for dura mater
Groove for superior petrosal sinus
Jugular foramen
Hypoglossal canal
Aqxicediictus vestihuli
Condyloid foramen
Mastoid foramen
Posterior meningeal grooves
Fig. 193. — Base of the skull. Upper surface.
at the foramen lacerum, and ends on the medial side of the anterior clinoid process,
where it is sometimes converted into a foramen (carotico-dmoid) by the union ot
the anterior with the middle clinoid process; posteriorly, it is bounded laterally
192 OSTEOLOGY
by the lingula. This groove lodges the cavernous sinus and the internal carotid
artery, the latter being surrounded by a plexus of sympathetic nerves.
The lateral parts of the middle fossa are of considerable depth, and support
the temporal lobes of the brain. They are marked by depressions for the brain
convolutions and traversed by furrows for the anterior and posterior branches
of the middle meningeal vessels. These furrows begin near the foramen spinosum,
and the anterior runs forward and upward to the sphenoidal angle of the parietal,
where it is sometimes converted into a bony canal ; the posterior runs lateralward
and backward across the temporal squama and passes on to the parietal near
the middle of its lower border. The following apertures are also to be seen. In
front is the superior orbital fissure, bounded above by the small wing, below, by the
great wing, and medially, by the body of the sphenoid; it is usually completed
laterally by the orbital plate of the frontal bone. It transmits to the orbital
cavity the oculomotor, the trochlear, the ophthalmic division of the trigeminal,
and the abducent nerves, some filaments from the cavernous plexus of the
sympathetic, and the orbital branch of the middle meningeal artery ; and from the
orbital cavity a recurrent branch from the lacrimal artery to the dura mater, and
the ophthalmic veins. Behind the medial end of the superior orbital fissure is
the foramen rotundum, for the passage of the maxillary nerve. Behind and lateral
to the foramen rotundum is the foramen ovale, which transmits the mandibular
nerve, the accessory meningeal artery, and the lesser superficial petrosal nerve. ^
Medial to the foramen ovale is the foramen VesaUi, which varies in size in different
individuals, and is often absent; when present, it opens below at the lateral side
of the scaphoid fossa, and transmits a small vein. Lateral to the foramen ovale
is the foramen spinosum, for the passage of the middle meningeal vessels, and a
recurrent branch from the mandibular nerve. INIedial to the foramen ovale is
the foramen lacenim; in the fresh state the lower part of this aperture is filled up
by a layer of fibrocartilage, while its upper and inner parts transmit the internal
carotid artery surrounded by a plexus of sympathetic nerves. The nerve of the
pterygoid canal and a meningeal branch from the ascending pharyngeal artery
pierce the layer of fibrocartilage. On the anterior surface of the petrous portion
of the temporal bone are seen the eminence caused by the projection of the superior
semicircular canal; in front of and a little lateral to this a depression corresponding
to the roof of the tympanic cavity; the groove leading to the hiatus of the facial
canal, for the transmission of the greater superficial petrosal nerve and the petrosal
branch of the middle meningeal artery; beneath it, the smaller groove, for the pas-
sage of the lesser superficial petrosal nerve; and, near the apex of the bone, the
depression for the semilunar ganglion and the orifice of the carotid canal.
The Posterior Fossa {fossa cranii posterior). — The posterior fossa is the largest
and deepest of the three. It is formed by the dorsum sella? and clivus of the
sphenoid, the occipital, the petrous and mastoid portions of the temporals, and the
mastoid angles of the parietal bones; it is crossed by the occipitomastoid and the
parietomastoid sutures, and lodges the cerebellum, pons, and medulla oblongata.
It is separated from the middle fossa in and near the median line by the dorsum
sellae of the sphenoid and on either side by the superior angle of the petrous por-
tion of the temporal bone. This angle gives attachment to the tentorum cerebelli,
is grooved for the superior petrosal sinus, and presents at its medial end a notch
upon which the trigeminal nerve rests. The fossa is limited behind by the grooves
for the transverse sinuses. In its center is the foramen magnum, on either side of
which is a rough tubercle for the attachment of the alar ligaments; a little above
this tubercle is the canal, which transmits the hypoglossal nerve and a meningeal
branch from the ascending pharyngeal artery. In front of the foramen magnum
' See footnote, page 150.
THE INTERIOR OF THE SKULL
193
the basilar portion of the occipital and the posterior part of the body of the sphenoid
form a grooved surface which supports the medulla oblongata and pons; in the
young skull these bones are joined by a synchondrosis. This grooved surface is
separated on either side from the petrous portion of the temporal by the petro-
occipital fissure, which is occupied in the fresh state by a plate of cartilage; the
fissure is continuous behind with the jugular foramen, and its margins are grooved
for the inferior petrosal sinus. The jugular foramen is situated between the lateral
part of the occipital and the petrous part of the temporal. The anterior portion
of this foramen transmits the inferior petrosal sinus; the posterior i)ortiou, the
transverse sinus and some meningeal branches from the occipital and ascending
pharyngeal arteries; and the intermediate portion, the glossopharyngeal, vagus,
and accessory nerves. Above the jugular foramen is the internal acoustic meatus,
for the facial and acoustic nerves and internal auditory artery; behind and lateral
Nasal bone
Frontal process
of maxilla
Inf. nasal concha
I
I
I
Palatine bone
Fig. 194. — Sagittal section of skull.
to this is the slit-like opening leading into the aquceductus vestibuli, which lodges
the ductus endolymphaticus; while between these, and near the superior angle of
the petrous portion, is a small triangular depression, the remains of the fossa sub-
arcuata, which lodges a process of the dura mater and occasionally transmits a small
vein. Behind the foramen magnum are the inferior occipital fossae, which support
the hemispheres of the cerebellum, separated from one another by the internal
occipital crest, which serves for the attachment of the falx cerebelli, and lodges
the occipital sinus. The posterior fossae are surmounted by the deep grooves for
the transverse sinuses. Each of these channels, in its passage to the jugular foramen,
grooves the occipital, the mastoid angle of the parietal, the mastoid portion of the
temporal, and the jugular process of the occipital, and ends at the back part of
the jugular foramen. Where this sinus grooves the mastoid portion of the temporal,
the orifice of the mastoid foramen may be seen; and, just previous to its termina-
tion, the condyloid canal opens into it ; neither opening is constant.
. 13
194
OSTEOLOGY
The Nasal Cavity {cavum nasi; nasal fossa). — The nasal cavities are two irregular
spaces, situated one on either side of the middle line of the face, extending from the
base of the cranium to the roof of the mouth, and separated from each other by a
thin vertical septum. They open on the face through the pear-shaped anterior nasal
aperture, and their posterior openings or choanae communicate, in the fresh
state, with the nasal part of the pharynx. They are much narrower above than
below, and in the middle than at their anterior or posterior openings: their depth,
which is considerable, is greatest in the middle. They communicate with the
frontal, ethmoidal, sphenoidal, and maxillary sinuses. Each cavity is bounded
by a roof, a floor, a medial and a lateral wall.
The roof (Figs. 195, 196) is horizontal in its central part, but slopes down-
ward in front and behind ; it is formed in front by the nasal bone and the spine
of the frontal ; in the middle, by the cribriform plate of the ethmoid ; and behind,
Crest of nasal bones
Frontal spine
Space for triangular
cartilage of septum
— Crest of palatines
Crest of maxillos
Fig. 195. — Medial wall of left nasal fossa.
by the body of the sphenoid, the sphenoidal concha, the ala of the vomer and the
sphenoidal process of the palatine bone. In the cribriform plate of the ethmoid
are the foramina for the olfactory nerves, and on the posterior part of the roof
is the opening into the sphenoidal sinus.
The floor is flattened from before backward and concave from side to side.
It is formed by the palatine process of the maxilla and the horizontal part of
the palatine bone; near its anterior end is the opening of the incisive canal.
The medial wall {septum nasi) (Fig. 195), is frequently deflected to one or other
side, more often to the left than to the right. It is formed, in front, by the crest
of the nasal bones and frontal spine; in the middle, by the perpendicular plate
of the ethmoid; behind, by the vomer and the rostrum of the sphenoid; below,
by the crest of the maxillae and palatine bones.- It presents, in front, a large,
triangular notch, which receives the cartilage of the septum; and behind, the
free edge of the vomer. Its surface is marked by numerous furrows for vessels
THE INTERIOR OF THE SKULL
195
and nerves and by the grooves for the nasopalatine nerve, and is traversed by
sutures connecting the bones of which it is formed.
The lateral wall (Fig. 196) is formed, in front, by the frontal process of the
maxilla and by the lacrimal bone; in the middle, by the ethmoid, maxilla, and
inferior nasal concha; behind, by the vertical plate of the palatine bone, and the
medial pterygoid plate of the sphenoid. On this wall are three irregular antero-
posterior passages, termed the superior, middle, and inferior meatuses of the nose.
The superior meatus, the smallest of the three, occupies the middle third of the
lateral wall. It lies between the superior and middle nasal conchfe; the spheno-
palatine foramen opens into it behind, and the posterior ethmoidal cells in front.
The sphenoidal sinus opens into a recess, the sphenoethmoidal recess, which is placed
above and behind the superior concha. The middle meatus is situated between the
middle and inferior conchse, and extends from the anterior to the posterior end of
Nasal bone
Frontal spine
Cribriform plate of ethmoid^
Sphenoid
Probe passed through
nasolacrimal canal
Bristle passed through
infundibulum
Anterior nasal spine
Palatine proc. of naxilla
Horizontal part of palatin
Posterior nasal spine
Incisive canal
Frontal pror. of maxilla
Larritnal
Ethmoid
Uncinate proc. of ethmoid
Inferior nasal concha
Palatine
— -Superior meatus
Middle meatus
Inferior meatus
Fig. 196. — Roof, floor, and lateral wall of left nasal cavity.
the latter. The lateral wall of this meatus can be satisfactorily studied only after
the removal of the middle concha. On it is a curved fissure, the hiatus semilunaris,
limited below by the edge of the uncinate process of the ethmoid and above by
an elevation named the bulla ethmoidalis; the middle ethmoidal cells are contained
within this bulla and open on or near to it. Through the hiatus semilunaris
the meatus communicates with a curved passage termed the infundibulum, which
communicates in front with the anterior ethmoidal cells and in rather more than
fifty per cent, of skulls is continued upward as the frontonasal duct into the frontal
air-sinus; when this continuity fails, the frontonasal duct opens directly into the
anterior part of the meatus. Below the bulla ethmoidalis and hidden by the unci-
nate process of the ethmoid is the opening of the maxillary sinus (ostium maxillare) ;
an accessory opening is frequently present above the posterior part of the inferior
nasal concha. The inferior meatus, the largest of the three, is the space between
the inferior concha and the floor of the nasal cavitv. It extends almost the entire
196
OSTEOLOGY
length of the lateral wall of the nose, is broader in front than behind, and presents
anteriorly the lower orifice of the nasolacrimal canal.
The Aiiterior Nasal Aperture (Fig. 181) is a heart-shaped or pyriform opening,
whose long axis is vertical, and narrow end upward ; in the recent state it is much
contracted by the lateral and alar cartilages of the nose. It is bounded above by
the inferior borders of the nasal bones; laterally by the thin, sharp margins which
separate the anterior from the nasal surfaces of the maxillse; and helow by the same
borders, where they curve medialward to join each other at the anterior nasal
spine.
The choanse are each bounded above by the under surface of the body of the
sphenoid and ala of the vomer; helow, by the posterior border of the horizontal
part of the palatine bone; laterally, by the medial pterygoid plate; they are
separated from each other by the posterior border of the vomer.
DIFFERENXES IX THE SKULL DUE TO AGE.
At birth the skull is large in proportion to the other parts of the skeleton, but its facial portion
is small, and equals only about one-eighth of the bulk of the cranium as compared with one-half
in the adult. The frontal and parietal eminences are prominent, and the greatest width of the
skull is at the level of the latter; on the other
Frontal Jontand hand, the glabella, supercihary arches, and
mastoid processes are not developed. Ossi-
fication of the skull bones is not completed,
and many of them, e. g., the occipital, temp-
orals, sphenoid, frontal, and mandible, consist
of more than one piece. Unossified mem-
branous intervals, termed fontanelles, are seen
at the angles of the parietal bones; these
fontaneUes are six in number: two, an ante-
rior and a posterior, are situated in the middle
Une, and two, an antero-lateral and a postero-
lateral, on either side.
The anterior or bregmatic fontanelle (Fig.
197) is the largest, and is placed at the junc-
tion of the sagittal, coronal, and frontal
sutures; it is lozenge-shaped, and measures
about 4 cm. in its antero-posterior and 2.5
cm. in its transverse diameter. The 'posterior
fontanelle is triangular in form and is situated
at the junction of the sagittal and lambdoidal
sutures. The lateral fontanelles (Fig. 19S) are
small, irregular in shape, and correspond re-
spectively with the sphenoidal and mastoid
angles of the parietal bones. An additional
fontanelle is sometimes seen in the sagittal
suture at the region of the obeUon. The
fontanelles are usuallj'^ closed by the growth
and extension of the bones which surroimd
them, but sometimes they are the sites of
separate ossific centers which develop into
sutural bones. The posterior and lateral fon-
tanelles are obliterated within a month or two after birth, but the anterior is not completely
closed imtil about the middle of the second j'ear.
The smaUness of the face at birth is mainly accounted for by the rudimentary- condition of
the maxillse and mandible, the non-eruption of the teeth, and the small size of the maxillary air
sinuses and nasal cavities. At birth the nasal cavities he almost entirely between the orbits, and
the lower border of the anterior nasal aperture is only a httle below the level of the orbital floor.
With the eruption of the deciduous teeth there is an enlargement of the face and jaws, and these
changes are still more marked after the second dentition.
The skull grows rapidly from birth to the seventh j'ear, by which time the foramen magnum
and petrous parts of the temporals have reached their fuU size and the orbital cavities are only
a little smaller than those of the adult. Growth is slow from the seventh year until the approach
Occipital fontanel
Fig. 197. — Skull at birth, showing frontal and occipital
fonticuli.
CRANIOLOGY
197
of puberty, when a second period of activity occurs: this results in an increase in all directions,
but it IS especially marked in the frontal and facial regions, where it is associated with the develop-
ment of the air sinuses.
ObUteration of the sutures of the vault of the skull takes place as age advances. This process
may commence between the ages of thirty and forty, and is first seen on the inner surface, and
some ten years later on the outer surface of the skull. The dates given are, however, only approxi-
mate, as it is impossible to state with anything hke accuracy the time at which the sutures are
closed. Obhteration usually occurs first in the posterior part of the sagittal suture, next in the
coronal, and then in the lambdoidal.
In old age the skull generally becomes thinner and Ughter, but in a small proportion of cases
it increases in thickness and weight, owing to an hypertrophy of the inner table. The most strik-
ing feature of the old skull is the diminution in the size of the maxilla; and mandible consequent
on the loss of the teeth and the absorption of the alveolar processes. This is associated with a
marked reduction in the vertical measurement of the face and with an alteration in the angles
of the mandible.
Frontal fontanel
Mastoid fontanel
Sphenoidal fontanel
Fig. 198. — Skull at birth, showing sphenoidal and mastoid fonticuli.
SEXUAL DIFFERENCES IN THE SKULL.
Until the age of puberty there is Httle difference between the skull of the female and that of
the male. The skull of an adult female is, as a rule, Ughter and smaller, and its cranial capacity
about 10 per cent, less, than that of the male. Its walls are thinner and its muscular ridges less
strongly marked; the glabella, supercihary arches, and mastoid processes are less prominent,
and the corresponding air sinuses are small or rudimentary. The upper margin of the orbit is
sharp, the forehead vertical, the frontal and parietal eminences prominent, and the vault some-
what flattened. The contour of the face is more rounded, the facial bones are smoother, and the
maxillae and mandible and their contained teeth smaller. From what has been said it wiU be seen
that more of the infantile characteristics are retained in the skull of the adult female than in that
of the adult male. A well-marked male or female skuU can easily be recognized as such, but in
some cases the respective characteristics are so indistinct that the determination of the sex may
be difficult or impossible.
CRANIOLOGY.
Skulls vary in size and shape, and the term craniology is applied to the study of these varia-
tions. The capacity of the cranial cavity constitutes a good index of the size of the bram which
it contained, and is most conveniently arrived at by filhng the cavity with shot and measuring
the contents in a graduated vessel. Skulls may be classified according to their capacities as
follows :
1. Microcephalic, with a capacity of less than 1350 c.cm. — e. g., those of native Australians
and Andaman Islanders.
2. Mesocephalic, with a capacity of from 1350 c.cm. to 1450 c.cm. — e. g., those of African
negroes and Chinese.
3 Megacephalic, with a capacity of over 1450 c.cm. — e. g., those of Europeans, Japanese, and
Eskimos.
198 OSTEOLOGY
In comparing the shape of one skull with that of another it is necessary to adopt some definite
position in which the skulls should be placed during the process of examination. They should
be so placed that a line carried through the lower margin of the orbit and upper margin of the
external acoustic meatus is in the horizontal plane. The normae of one skuU can then be com-
pared with those of another, and the differences in contour and surface form noted. Further,
it is necessary that the various hnear measurements used to determine the shape of the skull
ehould be made between definite and easily localized points on its surface. The principal points
may be divided into two groups: (1) those in the median plane, and (2) those on either side of it'.
The Points in the Median Plane are the:
Mental Point. The most prominent point of the chin.
Alveolar Point or Prosthion. The central point of the anterior margin of the upper alveolar
arch.
Subnasal Point. The middle of the lower border of the anterior nasal aperture, at the base
of the anterior nasal spine.
Nasion. The central point of the frontonasal suture.
Glabella. The point in the middle line at the level of the superciliary arches.
Ophryon. The point in the middle Une of the forehead at the level where the temporal lines
most nearly approach each other.
Bregma. The meeting point of the coronal and sagittal sutures.
Obelion. A point in the sagittal suture on a level with the parietal foramina.
Lambda. The point of junction of the sagittal and lambdoidal sutures.
Occipital Point. The point in the middle line of the occipital bone farthest from the glabella.
Inion. The external occipital protuberance.
Opisthion. The mid-point of the posterior margin of the foramen magnum.
Basion. The mid-point of the anterior margin of the foramen magnum.
The Points on Either Side of the Median Plane are the:
Gonion. The outer margin of the angle of the mandible.
Dacryon. The point of union of the antero-superior angle of the lacrimal with the frontal
bone and the frontal process of the maxilla.
Stephanion. The point where the temporal line intersects the coronal suture.
Pterion. The point where the great wing of the sphenoid joins the sphenoidal angle of the
parietal.
Auricular Point. The center of the orifice of the external acoustic meatus.
Asterion. The point of meeting of the lambdoidal, mastociccipital, and mastoparietal sutures.
The horizontal circumference of the cranium is measured in a plane passing through the glabella
(Turner) or the ophryon (Flower) in front, and the occipital point behind; it averages about
50 cm. in the female and 52.5 cm. in the male.
The occipitofrontal or longitudinal arc is measured from the nasion over the middle line of the
vertex to the opisthion: while the basinasal length is the distance between the basion and the
nasion. These two measurements, plus the antero-posterior diameter of the foramen magnum,
represent the vertical circumference of the cranium.
The length is measured from the glabella to the occipital point, while the breadth or greatest
transverse diameter is usually found near the external acoustic meatus. The proportion of
. 1 ,. , T. (breadth X 100) .
breadth to length . -r^ is termed the cephalic index or i?idex of breadth.
The height is usually measured from the basion to the bregma, and the proportion of height
^ (height X 100)
to length . ,, constitutes the vertical or height index.
In studjing the face the principal points to be noticed are the proportion of its length and
breadth, the shape of the orbits and of the anterior nasal aperture, and the degree of projection
of the jaws.
The length of the face may be measured from the ophryon or nasion to the chin, or, if the mandible
be wanting, to the alveolar point; while its width is represented by the distance between the
zygomatic arches. By comparing the length with the width of the face, skulls may be divided
into two groups; dolichofacial or leptoprosope (long faced) and brachyfacial or chemoprosope (short
faced).
The orbital index signifies the proportion which the orbital height bears to the orbital width,
thus:
orbital height X 100
orbital width
The nasal index expresses the proportion which the width of the anterior nasal aperture bears
to the height of the nose, the latter being measured from the nasion to the lower margin of the
nasal aperture, thus:
nasal width X 100
nasal height
CRANIOLOGY
199
The degree of projection of the jaws is determined by the gnathic or aheolar index, which repre-
sents the proportion between the basialvcolar and basinasal lengths, thus:
basialveolar length X 100
basinasal length
The following table, modified from that given by Duckworth,' illustrates how these different
indices may be utihzed in the classification of skulls:
Index.
Classification.
Nomenclature.
Examples.
1. Cephalic
Below 75
Between 75 and 80
Above 80
Below 84
Between 84 and S9
Above 89
DoUchocephalic
MesaticephaUc
Brachycephalic
Kaffirs and Native Australians.
Europeans and Chinese.
Mongohans and Andamans.
2. Orbital
Microseme
Mesoseme
Megaseme
Leptorhine
Mesorhine
Platyrhine
Orthognathous
Mesognathous
Prognathous
Tasmanians and Native Austra-
Hans.
Europeans.
Chinese and Polynesians.
3. Nasal
Below 48
Between 48 and 53
Above 53
Europeans.
Japanese and Chinese.
Negroes and Native Australians.
4. Gnathic
Below 98
Between 98 and 103
Above 103
Europeans.
Chinese and Japanese.
Native Australians.
The chief function of the skull is to protect the brain, and therefore those portions of the skull
which are most exposed to external violence are thicker than those which are shielded from injury
by overlying muscles. Thus, the skull-cap is thick and dense, whereas the temporal squamse
being protected by the temporales muscles, and the inferior occipital fossae, being shielded by the
muscles at the back of the neck, are thin and fragile. Fracture of the skull is further prevented
by its elasticity, its rounded shape, and its construction of a number of secondary elastic arches,
each made up of a single bone. The manner in which vibrations are transmitted through the
bones of the skull is also of importance as regards its protective mechanism, at all events as far
as the base is concerned. In the vault, the bones being of a fairly equal thickness and density,
vibrations are transmitted in a uniform manner in all directions, but in the base, owing to the
varying thickness and density of the bones, this is not so; and therefore in this situation there
are special buttresses which serve to carry the vibrations in certain definite directions. At the
front of the skull, on either side, is the ridge which separates the anterior from the middle fossa
of the base; and behind, the ridge or buttress which separates the middle from the posterior fossa;
and if any violence is apphed to the vault, the vibrations would be carried along these buttresses
to the sella turcica, where they meet. This part has been termed the "center of resistance,"
and here there is a special protective mechanism to guard the brain. The subarachnoid cavity
at the base of the brain is dilated, and the cerebrospinal fluid which fills it acts as a water cushion
to shield the brain from injury. In like manner, when violence is applied to the base of the skull,
as in falls upon the feet, the vibrations are carried backward through the occipital crest, and
forward through the basilar part of the occipital and body of the sphenoid to the vault of the skull.
In connection with the bones of the face a common malformation is cleft palate. The cleft
usually starts posteriorly, and its most elementary form is a bifid uvula; or the cleft may extend
through the soft palate; or the posterior part of the whole
of the hard palate may be involved, the cleft extending as
far forward as the incisive foramen. In the severest forms,
the cleft extends through the alveolus and passes between
the incisive or premaxillary bone and the rest of the max-
iUa; that is to say, between the lateral incisor and canine
teeth. In some instances, the cleft runs between the central
and lateral incisor teeth; and this has induced some
anatomists to believe that the premaxillary bone is devel-
oped from two centers (Fig. 199) and not from one, as was
stated on p. 163. The medial segment, bearing a central
incisor, is called an endognathion; the lateral segment, bear-
ing the lateral incisor, is called a mesognathion. The cleft
may affect one or both sides; if the latter, the central part is frequently displaced forward and re-
mains united to the septum of the nose, the deficiency in the alveolus being complicated with a cleft
' Morphology and Anthropology, by W. L. H. Duckworth, M.A., Cambridge University Press.
EndognatTiion
Mesognathion j!:^
Exognath ion
Fig. 199. — The premaxilla and its sutures.
(After Albrecht.)
200 OSTEOLOGY
in the lip (hare-lip). On examining a cleft palate in which the alveolus is not impHcated, the cleft
will generally appear to be in the median line, but occasionally is unilateral and in some cases bilat-
eral. To understand this it must be bornein mind that three processes are concerned in the formation
of the palate — the palatine processes of the two maxillte, which grow in horizontally and unite
in the middle line, and the ethmovomerine process, which grows downward from the base of
the skull and frontonasal process to unite with the palatine processes in the middle line. In
those cases where the palatine processes fail to unite with each other and with the medial process,
the cleft of the palate is median; where one palatine process unites with the medial septum, the
other faihng to do so, the cleft in the palate is unilateral. In some cases where the palatine pro-
cesses fail to meet in the middle, the ethmovomerine process grows downward between them and
thus produces a bilateral cleft. Occasionally there may be a hole in the middle line of the hard
palate, the anterior part of the hard and the soft palate being perfect; this is rare, because, as
a rule, the union of the various processes progresses from before backward, and therefore the
posterior part of the palate is more frequently defective than the anterior.
THE EXTREMITIES.
The bones by which the upper and lower limbs are attached to the trunk con-
stitute respectively the shoulder and pelvic girdles. The shoulder girdle or girdle
of the superior extremity is formed by the scapulae and clavicles, and is imperfect
in front and behind. In front, however, it is completed by the upper end of the
sternum, with which the medial ends of the clavicles articulate. Behind, it is
widely imperfect, the scapulae being connected to the trunk by muscles only.
The pelvic girdle or girdle of the inferior extremity is formed by the hip bones,
which articulate with each other in front, at the symphysis pubis. It is imperfect
behind, but the gap is filled in by the upper part of the sacrum. The pelvic girdle,
with the sacrum, is a complete ring, massive and comparatively rigid, in marked
contrast to the lightness and mobility of the shoulder girdle.
THE BONES OF THE UPPER EXTREMITY (OSS A EXTREMITATIS SUPERIORIS).
The Clavicle (Clavicula; Collar Bone).
The clavicle (Figs. 200, 201) forms the anterior portion of the shoulder girdle.
It is a long bone, curved somewhat like the italic letter/, and placed nearly horizon-
tally at the upper and anterior part of the thorax, immediately above the first
rib. It articulates medially with the manubrium sterni, and laterally with the
acromion of the scapula.^ It presents a double curvature, the convexity being
directed forward at the sternal end, and the concavity at the scapular end. Its
lateral third is flattened from above downward, while its medial two-thirds is of
a rounded or prismatic form.
Lateral Third. — The lateral third has two surfaces, an upper and a lower; and
two borders, an anterior and a posterior.
Surface. — The upper surface is flat, rough, and marked by impressions for the
attachments of the Deltoideus in front, and the Trapezius behind; between these
impressions a small portion of the bone is subcutaneous. The imder surface is
flat. At its posterior border, near the point where the prismatic joins with the
flattened portion, is a rough eminence, the coracoid tuberosity (conoid tubercle);
this, in the natural position of the bone, surmounts the coracoid process of the
scapula, and gives attachment to the conoid ligament. From this tuberosity an
oblique ridge, the oblique or trapezoid ridge, runs forward and lateralward, and
aftord attachment to the trapezoid ligament.
1 The clavicle acts especially as a fulcrum to enable the muscles to give lateral motion to the arm. It is accordingly
absent in those animals whose fore-limbs are used only for progression, but is present for the most part in animals
whose anterior extremities are clawed and used for prehension, though in some of them — as, for instance, in a large
number of the carnivora — it is merely a rudimentarj' bone suspended among the muscles, and not articulating with
either the scapula or sternum.
THE CLAVICLE
201
Borders. — The anterior border is concave, thin, and rough, and gives attachment
to the Deltoideus. The posterior border is convex, rough, thicker than the anterior,
and gives attachment to the Trapezius.
Medial Two-thirds.— The medial two-thirds constitute the prismatic portion
of the bone, which is curved so as to be convex in front, concave behind, and is
marked by three borders, separating three surfaces.
Borders. — The anterior border is continuous with the anterior margin of the fiat
portion. Its lateral part is smooth, and corresponds to the interval between the
attachments of the Pectoralis major and Deltoideus; its medial part forms the
lower boundary of an elliptical surface for the attachment of the clavicular portion
Sternal extremity
Acromial extremity
Fig. 200. — Left clavicle. Superior surface.
of the Pectoralis major, and approaches the posterior border of the bone. The
superior border is continuous with the posterior margin of the flat portion, and
separates the anterior from the posterior surface. Smooth and rounded laterally,
it becomes rough toward the medial third for the attachment of the Sternocleido-
mastoideus, and ends at the upper angle of the sternal extremity. The posterior
or subclavian border separates the posterior from the inferior surface, and extends
from the coracoid tuberosity to the costal tuberosity; it forms the posterior bouii-
dary of the groove for the Subclavius, and gives attachment to a layer of cervical
fascia which envelops the Omohyoideus.
Articular capsule
Articular capsule
Fio. 201. — Left clavicle. Inferior surface.
Surfaces. — The anterior surface is included between the superior and anterior
borders. Its lateral part looks upward, and is continuous with the superior sur-
face of the flattened portion; it is smooth, convex, and nearly subcutaneous, being
covered only by the Platysma. Medially it is divided by a narrow subcutaneous
area into two parts: a lower, elliptical in form, and directed forward, for the
attachment of the Pectoralis major; and an upper for the attachment of the
Sternocleidomastoideus. The posterior or cervical surface is smooth, and looks
backward toward the root of the neck. It is limited, above, by the superior
border; below, by the subclavian border; medially, by the margin of the sternal
extremity; and laterally, by the coracoid tuberosity. It is concave medio-laterally,
202 OSTEOLOGY
and is in relation, by its lower part, with the transverse scapular vessels. This
surface, at the junction of the curves of the bone, is also in relation with the brachial
plexus of nerves and the subclavian vessels. It gives attachment, near the sternal
extremity, to part of the Sternohyoideus ; and presents, near the middle, an oblique
foramen directed lateralward, which transmits the chief nutrient artery of the
bone. Sometimes there are two foramina on the posterior surface, or one on the
posterior and another on the inferior surface. The inferior or subclavian surface is
bounded, in front, by the anterior border; behind, by the subclavian border.
It is narrowed medially, but gradually increases in width laterally, and is contin-
uous with the imder surface of the flat portion. On its medial part is a broad
rough surface, the costal tuberosity {rhomboid impression), rather more than 2 cm.
in length, for the attachment of the costoclavicular ligament. The rest of this
surface is occupied by a groove, which gives attachment to the Subclavius; the
coracoclavicular fascia, which splits to enclose the muscle, is attached to the margins
of the groove. Not infrequently this groove is subdi\ided longitudinally by a
line which gives attachment to the intermuscular septum of the Subclavius.
The Sternal Extremity {extremiias sternalis; internal extremity). — The sternal
extremity of the clavicle is triangular in form, directed medialward, and a little
downward and forward; it presents an articular facet, concave from before back-
ward, convex from above downward, which articulates with the manubrium sterni
through the intervention of an articular disk. The lower part of the facet is con-
tinued on to the inferior surface of the bone as a small semi-oval area for articula-
tion with the cartilage of the first rib. The circumference of the articular surface
is rough, for the attachment of numerous ligaments; the upper angle gives attach-
ment to the articular disk.
The Acromial Extremity (extremitas acromialis; aider extremity). — The acromial
extremity presents a small, flattened, oval surface directed obliquely downward,
fgr articulation with the acromion of the scapula. The circiunference of the
articular facet is rough, especially above, for the attachment of the acromio-
clavicular ligaments.
In the female, the clavicle is generally shorter, thinner, less curved, and smoother than in the
male. In those persons who perform considerable manual labor it becomes thicker and more
curved, and its ridges for muscular attachment are prominently marked.
Structure. — The clavicle consists of cajicellous tissue, enveloped by a compact laj-er, which
is much thicker in the intermediate part than at the extremities of the bone.
Ossification. — The clavicle begins to ossify before any other bone in the body; it is ossified
from three centers — viz., two primary centers, a medial and a lateral, for the body,* which appear
during the fifth or sixth week of fetal hfe; and a secondarj- center for the sternal end, which
appears about the eighteenth or twentieth year, and unites with the rest of the bone about the
twenty-fifth year.
The Scapula i, Shoulder Blade).
The scapula forms the posterior part of the shoulder girdle. It is a flat, trian-
gular bone, with two surfaces, three borders, and three angles.
Surfaces. — The costal or ventral surface (Fig. 202) presents a broad concavity,
the subscapular fossa. The medial two-thirds of the fossa are marked by several
oblique ridges, which run lateralward and upward. The ridges give attachment
to the tendinous insertions, and the surfaces between them to the fleshy fibers,
of the Subscapularis. The lateral third of the fossa is smooth and coA-ered by the
fibers of this muscle. The fossa is separated from the vertebral border by smooth
triangular areas at the medial and inferior angles, and in the interval between
these by a narrow ridge which is often deficient. These triangular areas and the
intervening ridge afford attachment to the Serratus anterior. At the upper part
of the fossa is a transverse depression, where the bone appears to be bent on itself
1 Mall, American Journal of Anatomy, vol. v; Fawcett, Journal of Anatomy and Physiologj-, vol. slvii.
THE SCAPULA 203
along a line at right angles to and passing through the center of the glenoid cavity,
forming a considerable angle, called the subscapular angle; this gives greater
strength to the body of the bone by its arched form, while the summit of the
arch serves to support the spine and acromion.
The dorsal surface (Fig. 203) is arched from above downward, and is subdivided
into two unequal parts by the spine; the portion above the spine is called the
supraspinatous fossa, and that below it the infraspinatous fossa.
The supraspinatous fossa, the smaller of the two, is concave, smooth, and broader
at its vertebral than at its humeral end; its medial two-thirds give origin to the
Supraspinatus.
The infraspinatous fossa is much larger than the preceding; toward its vertebral
margin a shallow concavity is seen at its upper part; its center presents a promi-
nent convexity, while near the axillary border is a deep groove which runs from
the upper toward the lower part. The medial two-thirds of the fossa give origin
to the Infraspinatus; the lateral third is covered by this muscle.
The dorsal surface is marked near the axillary border by an elevated ridge,
which runs from the lower part of the glenoid cavity, downward and backward
to the vertebral border, about 2.5 cm. above the inferior angle. The ridge serves
for the attachment of a fibrous septum, which separates the Infraspinatus from
the Teres major and Teres minor. The surface between the ridge and the axillary
border is narrow in the upper two-thirds of its extent, and is crossed near its
center by a groove for the passage of the scapular circumflex vessels; it affords
attachment to the Teres minor. Its lower third presents a broader, somewhat
triangular surface, which gives origin to the Teres major, and over which the Latis-
simus dorsi glides; frequently the latter muscle takes origin by a few fibers from
this part. The broad and narrow portions above alluded to are separated by an
oblique line, which runs from the axillary border, downward and backward, to
meet the elevated ridge: to it is attached a fibrous septum which separates the
Teres muscles from each other.
The Spine (spina scapulw). — The spine is a prominent plate of bone, which
crosses obliquely the medial four-fifths of the dorsal surface of the scapula at its
upper part, and separates the supra- from the infraspinatous fossa. It begins
at the vertical border by a smooth, triangular area over which the tendon of inser-
tion of the lower part of the Trapezius glides, and, gradually becoming more ele-
vated, ends in the acromion, which overhangs the shoulder-joint. The spine is
triangular, and flattened from above downward, its apex being directed toward
the vertebral border. It presents two surfaces and three borders. Its superior
surface is concave; it assits in forming the supraspinatous fossa, and gives origin
to part of the Supraspinatus. Its inferior surface forms part of the infraspinatous
fossa, gives origin to a portion of the Infraspinatus, and presents near its center
the orifice of a nutrient canal. Of the three borders, the anterior is attached to the
dorsal surface of the bone; the posterior, or crest of the spine, is broad, and presents
two lips and an intervening rough interval. The Trapezhis is attached to the supe-
rior lip, and a rough tubercle is generally seen on that portion of the spine which
receives the tendon of insertion of the lower part of this muscle. The Deltoideus
is attached to the whole length of the inferior lip. The interval between the lips
is subcutaneous and partly covered by the tendinous fibers of these muscles. The
lateral border, or base, the shortest of the three, is slightly concave; its edge, thick
and round, is continuous above with the under surface of the acromion, below
with the neck of the scapula. It forms the medial boundary of the great scapular
notch, which serves to connect the supra- and infraspinatous fossae.
The Acromion.^The acromion forms the summit of the shoulder, and is a large,
somewhat triangular or oblong process, flattened from behind forward, projecting
at first lateralward, and then curving forward and upward, so as to overhang the
204
OSTEOLOGY
glenoid cavity. Its superior surface, directed upward, backward, and lateralward,
is convex, rough, and gives attachment to some fibers of the Deltoideus, and in the
rest of its extent is subcutaneous. Its inferior surface is smooth and concave.
Its lateral border is thick and irregular, and presents three or four tubercles for the
tendinous origins of the Deltoideus. Its medial border, shorter than the lateral,
is concave, gives attachment to a portion of the Trapezius, and presents about
its center a small, oval surface for articulation with the acromial end of the clavicle.
Articrdar capsule
Cora coacromial
ligament
Articular
capsule
FiQ. 202. — Left scapula. Costal surface.
Its apex, which corresponds to the point of meeting of these two borders in front,
is thin, and has attached to it the coracoacromial ligament.
Borders.— Of the three borders of the scapula, the superior is the shortest and
thinnest; it is concave, and extends from the medial angle to the base of the cora-
coid process. At its lateral part is a deep, semicircular notch, the scapular notch,
THE SCAPULA
205
formed partly by the base of the coracoid process. This notch is converted into
a foramen by the superior transverse ligament, and serves for the passage of the
suprascapular nerve; sometimes the ligament is ossified. The adjacent part of
the superior border affords attachment to the Omohyoideus. The axillary border
Coracohumeral
ligament
Coraco-acromial ligament
^'^fo
Trapezoid ligament
Conoid ligament
Articvlar
capsule
Fia. 203. — Left scapula. Dorsal surface.
is the thickest of the three. It begins above at the lower margin of the glenoid
cavity, and inclines obliquely downward and backward to the inferior angle.
Immediately below the glenoid cavity is a rough impression, the infraglenoid
tuberosity, about 2.5 cm. in length, which gives origin to the long head of the Tri-
ceps brachii; in front of this is a longitudinal groove, which extends as far as the
206
OSTEOLOGY
lower third of this border, and affords origin to part of the Subscapularis. The
inferior third is thin and sharp, and serves for the attachment of a few fibers of
the Teres major behind, and of the Subscapularis in front. The vertebral border
is the longest of the three, and extends from the medial to the inferior angle. It
is arched, intermediate in thickness between the superior and the axillary borders,
and the portion of it above the spine forms an obtuse angle with the part below.
This border presents an anterior and a posterior lip, and an intermediate narrow
area. The anterior lip affords attachment to the Serratus anterior; the posterior
lip, to the Supraspinatus above the spine, the Infraspinatus below; the area
Fig. 204. — Posterior view of the thorax and shoulder girdle. (Morris.)
between the two lips, to the Levator scapula* above the triangular surface at the
commencement of the spine, to the Rhomboideus minor on the edge of that surface,
and to the Rhomboideus major below it; this last is attached by means of a fibrous
arch, connected above to the lower part of the triangular surface at the base of
the spine, and below to the lower part of the border.
Angles. — Of the three angles, the medial, formed by the junction of the superior
and vertebral borders, is thin, smooth, rounded, inclined somewhat lateralward,
and gives attachment to a few fibers of the Levator scapulae. The inferior angle,
thick and rough, is formed by the union of the vertebral and axillary borders;
its dorsal surface affords attachment to the Teres major and frequently to a few
THE SCAPULA
207
Coracoid
process
Acromion
Glenoid cavity
Infraglenoid tubercle
fibers of the Latissimus dorsi. The lateral angle is the thickest part of the bone,
and is sometimes called the head of the scapula. On it is a shallow pvriform,
articular surface, the glenoid cavity, which is directed lateralward and 'forward
and articulates with the head of the humerus; it is broader below than above
and its vertical diameter is the longest. The surface is covered with cartilage
in the fresh state; and its margins, slightly raised, give attachment to a fibro-
cartilaginous structure, the glenoidal labrum, which deepens the cavity. At its
apex is a slight elevation, the
SUpraglenoid tuberosity, to which Supraglenoid tubercle
the long head of the Biceps
brachii is attached. The neck
of the scapula is the slightly
constricted portion which sur-
rounds the head; it is more dis-
tinct below and behind than
above and in front.
The Coracoid Process (processus
coracoideus) . — The coracoid pro-
cess is a thick curved process at-
tached bv a broad base to the
upper part of the neck of the
scapula; it runs at first upward
and medialward; then, becoming
smaller, it changes its direction,
and projects forward and lateral-
ward. The ascending portion,
flattened from before backward,
presents in front a smooth con-
cave surface, across which the
Subscapularis passes. The hori-
zontal portion is flattened from
above downward; its upper sur-
face is convex and irregular, and
gives attachment to the Pector-
alis minor; its under surface is
smooth; its medial and lateral
borders are rough; the former
gives attachment to the Pectoralis
minor and the latter to the cora-
coacromial ligament; the apex is
embraced by the conjoined tendon
of origin of the Coracobrachialis
and short head of the Biceps
brachii and gives attachment to
the coracoclavicular fascia. On
the medial part of the root of the
coracoid process is a rough im-
pression for the attachment of
the conoid ligament; and running from it obliquely forward and lateralward,
on to the upper. surface of the horizontal portion, is an elevated ridge for the
attachment of the trapezoid ligament.
For Subscapularis
Axillary border
-Inferior arujle
Fig. 205. — Left scapula. Lateral view.
Structure.^The head, processes, and the thickened parts of the bone, contain cancellous
tissue; the rest consists of a thin layer of compact tissue. The central part of the supraspinatous
208
OSTEOLOGY
fossa and the upper part of the infraspinatous fossa, but especially the former, are usually so thin
as to be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent
muscles are separated only by fibrous tissue.
Ossification (Fig. 206). — The scapula is ossified from seven or more centers: one for the body,
two for the coracoid process, two for the acromion, one for the vertebral border, and one for the
inferior angle.
Ossification of the body begins about the second month of fetal life, by the formation of an
irregular quadrilateral plate of bone, immediately behind the glenoid cavity. This plate extends
so as to form the chief part of the bone, the spine growing up from its dorsal surface about the
third month. At birth, a large part of the scapula is osseous, but the glenoid cavity, the coracoid
process, the acromion, the vertebral border, and the inferior angle are cartilaginous. From the
fifteenth to the eighteenth month after birth, ossification takes place in the middle of the coracoid
process, which as a rule becomes joined with the rest of the bone about the fifteenth year. Between
the fourteenth and twentieth years, ossification of the remaining parts takes place in quick succes-
sion, and usually in the following order; first, in the root of the coracoid process, in the form of a
broad scale; secondly, near the base of the acromion; thirdly, in the inferior angle and contiguous
part of the vertebral border; fourthly, near the extremity of the acromion; fifthly, in the vertebral
border. The base of the acromion is formed by an extension from the spine; the two separate
nuclei of the acromion unite, and then join with the extension from the spine. The upper third
Fig. 206. — Plan of ossification of the scapula. From seven centers.
of the glenoid cavity is ossified from a separate center (subcoracoid), which makes its appear-
ance between the tenth and eleventh years and joins between the sixteenth and the eighteenth.
Further, an epiphysial plate appears for the lower part of the glenoid cavity, while the tip of the
coracoid process frequently presents a separate nucleus. These various epiphyses are joined
to the bone by the twenty-fifth year. Failure of bony union between the acromion and spine
sometimes occurs, the junction being effected by fibrous tissue, or by an imperfect articulation;
in some cases of supposed fracture of the acromion with ligamentous union, it is probable that
the detached segment was never united to the rest of the bone.
THE HUMERUS 209
The Humerus (Arm Bone).
The humerus (Figs. 207, 208) is the longest and largest bone of the upper
extremity; it is divisible into a body and two extremities.
Upper Extremity.— The upper extremity consists of a large rounded head joined
to the body by a constricted portion called the neck, and two eminences, the greater
and lesser tubercles.
The Head {cayut humeri).— The head, nearly hemispherical in form,i is directed
upward, medial ward, and a little backward, and articulates with the glenoid cavity
of the scapula. The circumference of its articular surface is slightly constricted
and is termed the anatomical neck, in contradistinction to a constriction below the
tubercles called the surgical neck which is frequently the seat of fracture. Fracture
of the anatomical neck rarely occurs.
The Anatomical Neck (collum anatomicum) is obliquely directed, forming an
obtuse angle with the body. It is best marked in the lower half of its circum-
ference ; in the upper half it is represented by a narrow groove separating the head
from the tubercles. It affords attachment to the articular capsule of the shoulder-
joint, and is perforated by numerous vascular foramina.
The Greater Tubercle (tuberculum majus; greater tuberosity). — The greater
tubercle is situated lateral to the head and lesser tubercle. Its upper surface is
rounded and marked by three flat impressions : the highest of these gives insertion
to the Supraspinatus; the middle to the Infraspinatus; the lowest one, and the
body of the bone for about 2.5 cm. below it, to the Teres minor. The lateral
surface of the greater tubercle is convex, rough, and continuous with the lateral
surface of the body.
The Lesser Tubercle {tuberculum minus; lesser tuberosity). — The lesser tubercle,
although smaller, is more prominent than the greater: it is situated in front, and
is directed medialward and forward. Above and in front it presents an impression
for the insertion of the tendon of the Subscapularis.
The tubercles are separated from each other by a deep groove, the intertubercular
groove (bicipital groove), which lodges the long tendon of the Biceps brachii and
transmits a branch of the anterior humeral circumflex artery to the shoulder-joint.
It runs obliquely downward, and ends near the junction of the upper with the
middle third of the bone. In the fresh state its upper part is covered with a
thin layer of cartilage, lined by a prolongation of the synovial membrane of the
shoulder-joint; its lower portion gives insertion to the tendon of the Latissimus
dorsi. It is deep and narrow above, and becomes shallow and a little broader
as it descends. Its lips are called, respectively, the crests of the greater and lesser
tubercles {bicipital ridges), and form the upper parts of the anterior and medial
borders of the body of the bone.
The Body or Shaft {corpus humeri). — The body is almost cylindrical in the upper
half of its extent, prismatic and flattened below, and has three borders and three
surfaces.
Borders. — The anterior border runs from the front of the greater tubercle above
to the coronoid fossa below, separating the antero-medial from the antero-lateral
surface. Its upper part is a prominent ridge, the crest of the greater tubercle;
it serves for the insertion of the tendon of the Pectoralis major. About its center
it forms the anterior boundary of the deltoid tuberosity ; below, it is smooth and
rounded, affording attachment to the Brachialis.
The lateral border runs from the back part of the greater tubercle to the
1 Though the head is nearly hemispherical in form, its margin, as Humphry has shown, is by no ineans a true circle.
Its greatest diameter is, from the top of the intertubercular groove in a direction downward, medialward, and back-
ward. Hence it follows that the greatest elevation of the arm can be obtained by rolling the articular surface m this
direction — that is to say, obliquely upward, lateralward, and forward.
14
210
OSTEOLOGY
Articular capstde
cavity
^^
'.> ±<>
^erc^
>'
>Rl!
L^'.^x.
SurqCoai Neek-
r-
^
All;
0 l"^ •-/
■ 'IJI
V -
\\
%
oy
•\5J
Brachioradialis
^ i^\
,m\^
Extensor carpi radialis
longiLs
Common origin oj
Flexor carpi radialis '^%
Palmaris longus '^'^
Flexor digitorum, svblimis
Flexor carpi ulnaris
'., FossO
rochlea-M
A: \^
Jt Capii
ami
niv,
%i Articular capstde
"S'
V^
Common origin of
Extensor carpi rad. brev,
,, digitorum communis
,, dig it i qu int i prop.
,, carpi ulnaris
Supinator
Fig. 207. — Left humerus. Anterior view.
THE HUMERUS
211
lateral epicondyle, and separates the antero-
lateral from the posterior surface. Its upper
half is rounded and indistinctly marked, serv-
ing for the attachment of the lower part of the
insertion of the Teres minor, and below this
giving origin to the lateral head of the Triceps
brachii; its center is traversed by a broad but
shallow oblique depression, the radial sulcus
(muscnlospiral groove). Its lower part forms a
prominent, rough margin, a little curved from
behind forward, the lateral supracondylar ridge,
which presents an anterior lip for the origin
of the Brachioradialis above, and Extensor
carpi radialis longus below, a posterior lip for
the Triceps brachii, and an intermediate ridge
for the attachment of the lateral intermuscu-
lar septum.
The medial border extends from the lesser
tubercle to the medial epicondyle. Its upper
third consists of a prominent ridge, the crest of
the lesser tubercle, which gives insertion to the
tendon of the Teres major. About its center
is a slight impression for the insertion of the
Coracobrachialis, and just below this is the
entrance of the nutrient canal, directed down-
ward; sometimes there is a second nutrient
canal at the commencement of the radial sulcus.
The inferior third of this border is raised into
a slight ridge, the medial supracondylar ridge,
which becomes very prominent below; it pre-
sents an anterior lip for the origins of the
Brachialis and Pronator teres, a posterior lip
for the medial head of the Triceps brachii,
and an intermediate ridge for the attachment
of the medial intermuscular septum.
Surfaces. — The antero-lateral surface is di-
rected laterahvard above, where it is smooth,
rounded, and covered by the Deltoideus; for-
ward and laterahvard below, where it is slightly
concave from above downward, and gives origin
to part of the Brachialis. About the middle
of this surface is a rough, triangular elevation,
the deltoid tuberosity for the insertion of the
Deltoideus; below this is the radial sulcus,
directed obliquely from behind, forward, and
downward, and transmitting the radial nerve
and profunda artery.
The antero-medial surface, less extensive than
the antero-lateral, is directed medialward above,
forward and medialw^ard below; its upper part
is narrow, and forms the floor of the intertuber-
cular groove which gives insertion to the tendon
of the Latissimus dorsi; its middle part is
slightly rough for the attachment of some of
Uteres]
>llt<OII
f^\
t >
toll
Articular
capsule
Articvlar
capsule
\\ fffLt^^^*
Fig. 208. — Left humerus Posterior view.
212 OSTEOLOGY
the fibers of the tendon of insertion of the Coracobrachialis; its lower part is
smooth, concave from above downward, and gives origin to the Brachiahs.^
The posterior surface appears somewhat twisted, so that its upper part is
directed a httle medialward, its lower part backward and a little lateralward.
Nearly the whole of this surface is covered by the lateral and medial heads of
the Triceps brachii, the former arising above, the latter below the radial
sulcus.
The Lower Extremity. — The lower extremity is flattened from before backward,
and curved slightly forward; it ends below in a broad, articular surface, which is
divided into two parts by a slight ridge. Projecting on either side are the lateral
and medial epicondyles. The articular surface extends a little lower than the
epicondyles, and is curved slightly forward ; its medial extremity occupies a lower
level than the lateral. The lateral portion of this surface consists of a smooth,
rounded eminence, named the capitulum of the humerus ; it articulates with the cup-
shaped depression on the head of the radius, and is limited to the front and lower
part of the bone. On the medial side of this eminence is a shallow groove, in which
is received the medial margin of the head of the radius. Above the front part
of the capitulum is a slight depression, the radial fossa, which receives the anterior
border of the head of the radius, when the forearm is flexed. The medial portion
of the articular surface is named the trochlea, and presents a deep depression be-
tween two well-marked borders; it is convex from before backward, concave from
side to side, and occupies the anterior, lower, and posterior parts of the extremity.
The lateral border separates it from the groove which articulates with the margin
of the head of the radius. The medial border is thicker, of greater length, and
consequently more prominent, than the lateral. The grooved portion of the artic-
ular surface fits accurately within the semilunar notch of the ulna; it is broader and
deeper on the posterior than on the anterior aspect of the bone, and is inclined
obliquely downward and forward toward the medial side. Above the front part
of the trochlea is a small depression, the coronoid fossa, which receives the coronoid
process of the ulna during flexion of the forearm. Above the back part of the troch-
lea is a deep triangular depression, the olecranon fossa, in which the summit of the
olecranon is received in extension of the forearm. These fossae are separated from
one another by a thin, transparent lamina of bone, which is sometimes perforated
by a supratrochlear foramen; they are lined in the fresh state by the synovial
membrane of the elbow-joint, and their margins afford attachment to the anterior
and posterior ligaments of this articulation. The lateral epicondyle is a small,
tuberculated eminence, curved a little forward, and giving attachment to the radial
collateral ligament of the elbow-joint, and to a tendon common to the origin of
the Supinator and some of the Extensor muscles. The medial epicondyle, larger
and more prominent than the lateral, is directed a little backward ; it gives attach-
ment to the ulnar collateral ligament of the elbow-joint, to the Pronator teres,
and to a common tendon of origin of some of the Flexor muscles of the forearm;
the ulnar nerve runs in a groove on the back of this epicondyle. The epicondyles
are continuous above with the supracondylar ridges.
Structure. — The extremities consist of cancellous tissue, covered with a thin, compact layer
(Fig. 209) ; the body is composed of a cylinder of compact tissue, thicker at the center than toward
the extremities, and contains a large medullary canal which extends along its whole length.
1 A small, hook-shaped process of bone, the supracondylar process, varying from 2 to 20 mm. in length, is not infre-
quently found projecting from the antero-medial surface of the body of the humerus 5 cm. above the medial epicondyle.
It is curved downward and forward, and its pointed end is connected to the medial border, just above the medial
epicondyle, by a fibrous band, which gives origin to a portion of the Pronator teres; through the arch completed by
this fibrous band the median nerve and brachial artery pass, when these structures deviate from their usual course.
Sometimes the nerve alone is transmitted through it, or the nerve may be accompanied by the ulnar artery, in cases
of high division of the brachial. A well-marked groove is usually found behind the process, in which the nerve and
artery are lodged. This arch is the homologue of the supracondyloid foramen found in many animals, and probably
Berves in them to protect the nerve and artery from compression during the contraction of the muscles in this region.
THE HUMERUS
213
Ossification (Figs. 210, 211).— The humerus is ossi-
fied from eight centers, one for each of the following
parts; the body, the head, the greater tubercle, the
lesser tubercle, the capitulum, the trochlea, and one
for each epicondyle. The center for the body appears
near the middle of the bone in the eighth week of fetal
fife, and soon extends toward the extremities. At birth
the humerus is ossified in nearly its whole length, only
the extremities remaining cartilaginous. During the
first year, sometimes before birth, ossification commences
in the head of the bone, and dm-ing the third year the
center for the greater tubercle, and during the fifth that
for the lesser tubercle, make their appearance. By the
sixth year the centers for the head and tubercles have
joined, so as to form a single large epiphysis, which fuses
with the body about the twentieth year. The lower end
of the humerus is ossified as follows. At the end of
the second year ossification begins in the capitulum,
and extends medialward, to form the chief part of the
articular end of the bone; the center for the medial part
of the trochlea appears about the age of twelve. Ossifi-
cation begins in the medial epicondyle about the fifth
year, and in the lateral about the thirteenth or four-
teenth year. About the sixteenth or seventeenth year,
the lateral epicondyle and both portions of the articu-
lating surface, having already joined, unite with the
body, and at the eighteenth year the medial epicon-
dyle becomes joined to it.
Epiphysial line
Fig. 209. — Longitudinal section of head of
left humerus.
Epiphyses of head and
tubercles blend at fifth
year, and unite with
body at twentieth
year
Unites with body\
at ei<jhitenth year) t^"
Blcn3. O'f^ a\ ^^
Fig. 210. — Plan of ossification of the humerus.
Fig. 211. — Epiphysial lines of humerus in a young
adult. Anterior aspect. The lines of attachment of
the articular capsules are in blue.
214
OSTEOLOGY
Olecranon
The Ulna (Elbow Bone).i
The ulna (Figs. 212, 213) is a long bone, prismatic in form, placed at the medial
side of the forearm, parallel with the radius. It is divisible into a body and
two extremities. Its upper extremity, of great thickness and strength, forms
a large part of the elbow-joint; the bone diminishes in size from above downward,
its lower extremity being very small, and excluded
from the wrist-joint by the interposition of an
articular disk.
The Upper Extremity (proximal extremity) (Fig.
212). — The upper extremity presents two curved
processes, the olecranon and the coronoid process;
and two concave, articular cavities, the semilunar
and radial notches.
The Olecranon [olecranon process). — The olecra-
non is a large, thick, curved eminence, situated
at the upper and back part of the ulna. It is bent
forward at the summit so as to present a promi-
nent lip which is received into the olecranon fossa
of the himierus in extension of the forearm. Its
base is contracted where it joins the body and the
narrowest part of the upper end of the ulna. Its
posterior surface, directed backward, is triangular,
smooth, subcutaneous, and covered by a bursa.
Its superior surface is of quadrilateral form, marked
behind by a rough impression for the insertion of
the Triceps brachii; and in front, near the margin,
by a slight transverse groove for the attachment
of part of the posterior ligament of the elbow -joint.
Its anterior surface is smooth, concave, and forms
the upper part of the semilunar notch. Its borders
present continuations of the groove on the margin
of the superior surface ; they serve for the attach-
ment of ligaments, viz., the back part of the ulnar
collateral ligament medially, and the posterior
ligament laterally. From the medial border a part
of the Flexor carpi ulnaris arises; while to the
lateral border the Anconseus is attached.
The Coronoid Process (processus coronoideus) . —
The coronoid process is a triangular eminence
projecting forward from the upper and front part
of the ulna. Its base is continuous with the body
of the bone, and of considerable strength. Its
apex is pointed, slightly curved upward, and in
flexion of the forearm is received into the coronoid
fossa of the humerus. Its upper surface is smooth, concave, and forms the lower
part of the semilunar notch. Its antero-inferior surface is concave, and marked by
a rough impression for the insertion of the Brachialis. At the junction of this
surface with the front of the body is a rough eminence, the tuberosity of the ulna,
which gives insertion to a part of the Brachialis; to the lateral border of this
tuberosity the oblique cord is attached. Its lateral surface presents a narrow,
oblong, articular depression, the radial notch. Its medial surface, by its prominent,
Fia. 212. — Upper extremity of left ulna.
Lateral aspect.
' In the anatomical position, the forearm is placed in extension and supination with the palm looking forward
and the thumb on the outer side.
THE ULNA 215
free margin, serves for the attachment of part of the ulnar collateral ligament.
At the front part of this surface is a small rounded eminence for the origin
of one head of the Flexor digitorum sublimis; behind the eminence is a depression
for part of the origin of the Flexor digitorum profundus; descending from the
eminence is a ridge which gives origin to one head of the Pronator teres. Fre-
quently, the Flexor pollicis longus arises from the lower part of the coronoid
process by a rounded bundle of muscular fibers.
The Semilunar Notch {incisiira semilunnris; greater sigmoid cavity). — The semi-
lunar notch is a large depression, formed by the olecranon and the coronoid process,
and serving for articulation with the trochlea of the humerus. About the middle
of either side of this notch is an indentation, which contracts it somewhat, and
indicates the junction of the olecranon and the coronoid process. The notch is
concave from above downward, and divided into a medial and a lateral portion by
a smooth ridge running from the summit of the olecranon to the tip of the coronoid
process. The medial portion is the larger, and is slightly concave transversely;
the lateral is convex above, slightly concave below.
The Radial Notch {incisura radialis; lesser sigmoid cavity).— The radial notch
is a narrow, oblong, articular depression on the lateral side of the coronoid process;
it receives the circumferential articular surface of the head of the radius. It is
concave from before backward, and its prominent extremities serve for the attach-
ment of the annular ligament.
The Body or Shaft {corpus idnce). — The body at its upper part is prismatic
in form, and curved so as to be convex behind and lateralward; its central part
is straight; its lower part is rounded, smooth, and bent a little lateralward. It
tapers gradually from above downward, and has three borders and three surfaces.
Borders. — The volar border {margo volaris; anterior border) begins above at the
prominent medial angle of the coronoid process, and ends below in front of the
styloid process. Its upper part, well-defined, and its middle portion, smooth and
rounded, give origin to the Flexor digitorum profundus; its lower fourth serves
for the origin of the Pronator quadratus. This border separates the volar from
the medial surface.
The dorsal border (margo dorsalis; posterior border) begins above at the apex of
the triangular subcutaneous surface at the back part of the olecranon, and ends
below at the back of the styloid process; it is well-marked in the upper three-
fourths, and gives attachment to an aponeurosis which affords a common origin to
the Flexor carpi ulnaris, the Extensor carpi ulnaris, and the Flexor digitorum pro-
fundus; its lower fourth is smooth and rounded. This border separates the medial
from the dorsal surface.
The interosseous crest {crista interossea; external or interosseous border) begins
above by the union of two lines, which converge from the extremities of the radial
notch and enclose between them a triangular space for the origin of part of the
Supinator; it ends below at the head of the ulna. Its upper part is sharp, its lower
fourth smooth and rounded. This crest gives attachment to the interosseous mem-
brane, and separates the volar from the dorsal surface.
Surfaces. — The volar surface {fades volaris; anterior surface), much broader
above than below, is concave in its upper three-fourths, and gives origin to the
Flexor digitorum profundus; its lower fourth, also concave, is covered by the
Pronator quadratus. The lower fourth is separated from the remaining portion
by a ridge, directed obliquely downward and medialward, which marks the extent
of origin of the Pronator quadratus. At the junction of the upper with the
middle third of the bone is the nutrient canal, directed obliquely upward.
The dorsal surface {fades dorsalis; posterior surface) directed backward and
lateralward, is broad and concave above; convex and somewhat narrower in the
middle; narrow, smooth, and rounded below. On its upper part is an oblique
216
OSTEOLOGY
tTLNA
Articular capsule
BADIUS
Flexor digitorum
sublimis
Pronator
teres
Occasional ori
of Flexor ■pollicis lo
Articular
capsule
\^ Radial origin of
I Flexor digitorum
I sublimis
Styloid -process
^"a^c&J^i^^^
Brack iorad ia lis
Groove for Abductor
pollicis longus and
Extensor pollicis brevis
Styloid process
FiQ. 213. — Bones of left forearm. Anterior aspect.
THE ULNA
217
ULNA
For\
(Abductor pollicis
I longus
Extensor pollicis
brevis
RADIUS
For Ext. carpi radialis longus
For Extensor carpi radialis brevis
For Extensor pollicis loiigus
Articular capsule
Flexor digitorum sublimis
Articxdur capsule
For Extensor carpi ^dnaris
For Extensor digiti quinti proprius
P (Extensor indicis proprius
\Extensor digitorum comm
communis
Fia 214. — Bones of left forearm. Posterior aspect.
218
OSTEOLOGY
ridge, which runs from the dorsal end of the radial notch, downward to the dorsal
border; the triangular surface above this ridge receives the insertion of the
Anconanis, while the upper part of the ridge affords attachment to the Supinator.
Below this the surface is subdivided by a longitudinal ridge, sometimes called the
perpendicular line, into two parts: the medial part is smooth, and covered by the
Extensor carpi ulnaris; the lateral portion, wider and rougher, gives origin from
above downward to the Supinator, the Abductor pollicis longus, the Extensor poUicis
longus, and the Extensor indicis proprius.
The medial surface {fades medialis; internal surface) is broad and concave
above, narrow and convex below. Its upper three-fourths give origin to the
Flexor digitorum profundus; its lower fourth is subcutaneous.
Appears at
tenth year
Olecranon
Joins body at
sixteenth year
Appears at
fourth year
Joins body at
twentieth year
Inferior extremity
Fia.
215. — Plan of ossification of the ulna.
From three centers.
Fig. 216. — Epiphysial lines of ulna in a young adult.
Lateral aspect. The lines of attachment of the articular
capsules are in blue.
The Lower Extremity {distal extremity). — The lower extremity of the ulna is
small, and presents two eminences; the lateral and larger is a rounded, articular
eminence, termed the head of the ulna; the medial, narrower and more projecting,
is a non-articular eminence, the styloid process. The head presents an articular
surface, part of which, of an oval or semilunar form, is directed downward, and
articulates with the upper surface of the triangular articular disk which separates it
from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex,
and received into the ulnar notch of the radius. The styloid process projects from
the medial and back part of the bone; it descends a little lower than the head,
and its rounded end affords attachment to the ulnar collateral ligament of the
wrist-joint. The head is separated from the styloid process by a depression for
the attachment of the apex of the triangular articular disk, and behind, by a shallow
groove for the tendon of the Extensor carpi ulnaris.
THE RADIUS 219
Structure.— The long, narrow medullary cavity is enclosed in a strong wall of compact tissue
which is thickest along the interosseous border and dorsal surface. At the extremities the compact
layer thins. The compact layer is continued onto the back of the olecranon as a plate of close
spongy bone with lamella? parallel. From the inner surface of this plate and the compact layer
below it trabecule arch forward toward the olecranon and coronoid and cross other trabecular,
passing backward over the medullary cavity from the upper part of the shaft below the coronoid.
Below the coronoid process there is a small area of compact bone from which trabecule curve
upward to end obliquely to the surface of the semilunar notch which is coated with a thin layer of
compact bone. The trabecular at the lower end have a more longitudinal direction.
Ossification (Figs. 215, 216).— The ulna is ossified from three centers: one each for the body, the
inferior extremity, and the top of the olecranon. Ossification begins near the middle of the body,
about the eighth week of fetal life, and soon extends through the greater part of the bone. At birth
the ends are cartilaginous. About the fourth year, a center appears in the middle of the head,
and soon extends into the styloid process. About the tenth year, a center appears in the olecranon
near its extremity, the chief part of this process being formed by an upward extension of the body.
The upper epiphysis joins the body about the sixteenth, the lower about the twentieth year.
Articulations. — The ulna articulates with the humerus and radius.
The Radius.
The radius (Figs. 213, 214) is situated on the lateral side of the ulna, which
exceeds it in length and size. Its upper end is small, and forms only a small part
of the elbow-joint ; but its lower end is large, and forms the chief part of the wrist-
joint. It is a long bone, prismatic in form and slightly curved longitudinally. It
has a body and two extremities.
The Upper Extremity (proximal extremity). — The upper extremity presents a
head, neck, and tuberosity. The head is of a cylindrical form, and on its upper
surface is a shallow cup or fovea for articulation with the capitulum of the humerus.
The circumference of the head is smooth; it is broad medially where it articulates
with the radial notch of the ulna, narrow in the rest of its extent, which is embraced
by the annular ligament. The head is supported on a round, smooth, and con-
stricted portion called the neck, on the back of which is a slight ridge for the inser-
tion of part of the Supinator. Beneath the neck, on the medial side, is an eminence,
the radial tuberosity; its surface is divided into a posterior, rough portion, for the
insertion of the tendon of the Biceps brachii, and an anterior, smooth portion, on
which a bursa is interposed between the tendon and the bone.
The Body or Shaft (corpus radii). — The body is prismoid in form, narrower
above than below, and slightly curved, so as to be convex lateralward. It presents
three borders and three surfaces.
Borders. — The volar border (mar go volaris; anterior border) extends from the lower
part of the tuberosity above to the anterior part of the base of the styloid process
below, and separates the volar from the lateral surface. Its upper third is promi-
nent, and from its oblique direction has received the name of the oblique line of the
radius ; it gives origin to the Flexor digitorum sublimis and Flexor poUicis longus ; the
surface above the line gives insertion to part of the Supinator. The middle third of
the volar border is indistinct and rounded. The lower fourth is prominent, and gives
insertion to the Pronator quadratus, and attachment to the dorsal carpal ligament;
it ends in a small tubercle, into which the tendon of the Brachioradialis is inserted.
The dorsal border (margo dorsalis; posterior border) begins above at the back of
the neck, and ends below at the posterior part of the base of the styloid process;
it separates the posterior from the lateral surface. It is indistinct above and below,
but well-marked in the middle third of the bone.
The interosseous crest (crista interossea; internal or interosseous border) begins
above, at the back part of the tuberosity, and its upper part is rounded and indis-
tinct; it becomes sharp and prominent as it descends, and at its lower part divides
into two ridges which are continued to the anterior and posterior margins of the
ulnar notch. To the posterior of the two ridges the lower part of the interosseous
220 OSTEOLOGY
membrane is attached, while the triangular surface between the ridges gives inser-
tion to part of the Pronator quadratus. This crest separates the volar from the
dorsal surface, and gives attachment to the interosseous membrane.
Surface.^ — The volar surface (fades volaris; anterior surface) is concave in its
upper three-fourths, and gives origin to the Flexor pollicis longus; it is broad and fiat
in its lower fourth, and affords insertion to the Pronator quadratus. A prominent
ridge limits the insertion of the Pronator quadratus below, and between this and
the inferior border is a triangular rough surface for the attachment of the volar
radiocarpal ligament. At the junction of the upper and middle thirds of the
volar surface is the nutrient foramen, which is directed obliquely upward.
The dorsal surface {fades dorsalis; posterior surface) is convex, and smooth in
the upper third of its extent, and covered by the Supinator. Its middle third is
broad, slightly concave, and gives origin to the Abductor pollicis longus above,
and the Extensor pollicis brevis below. Its lower third is broad, convex, and
covered by the tendons of the muscles which subsequently run in the grooves on
the lower end of the bone.
The lateral surface {fades lateralis; external surface) is convex throughout its
entire extent. Its upper third gives insertion to the Supinator. About its center is
a rough ridge, for the insertion of the Pronator teres. Its lower part is narrow, and
covered by the tendons of the Abductor pollicis longus and Extensor pollicis brevis.
The Lower Extremity. — The lower extremity is large, of quadrilateral form,
and provided with two articular surfaces — one below, for the carpus, and another
at the medial side, for the ulna. The carpal articular surface is triangular, concave,
smooth, and divided by a slight antero-posterior ridge into two parts. Of these,
the lateral, triangular, articulates with the navicular bone; the medial, quadri-
lateral, with the lunate bone. The articular surface for the ulna is called the ulnar
notch {sigmoid cavity) of the radius; it is narrow, concave, smooth, and articulates
with the head of the ulna. These two articular surfaces are separated by a promi-
nent ridge, to which the base of the triangular articular disk is attached; this disk
separates the wrist-joint from the distal radioulnar articulation. This end of the
bone has three non-articular surfaces — volar, dorsal, and lateral. The volar surface,
rough and irregular, affords attachment to the volar radiocarpal ligament. The
dorsal surface is convex, affords attachment to the dorsal radiocarpal ligament,
and is marked by three grooves. Enumerated from the lateral side, the first
groove is broad, but shallow, and subdivided into two by a slight ridge; the lateral
of these two transmits the tendon of the Extensor carpi radialis longus, the medial
the tendon of the Extensor carpi radialis brevis. The second is deep but 'narrow,
and bounded laterally by a sharply defined ridge; it is directed obliquely from above
downward and lateralward, and transmits the tendon of the Extensor pollicis
longus. The third is broad, for the passage of the tendons of the Extensor indicis
proprius and Extensor digitorum communis. The lateral surface is prolonged
obliquely downward into a strong, conical projection, the styloid process, which
gives attachment by its base to the tendon of the Brachioradialis, and by its apex
to the radial collateral ligament of the wrist-joint. The lateral surface of this
process is marked by a flat groove, for the tendons of the Abductor pollicis longus
and Extensor pollicis brevis.
Structure. — The long narrow medullary cavity is enclosed in a strong wall of compact tissue
which is thickest along the interosseous border and thinnest at the extremities except over the
cup-shaped articular surface (fovea) of the head where it is thickened. The trabeculae of the
spongy tissue are somewhat arched at the upper end and pass upward from the compact layer of
the shaft to the fovea capituli; they are crossed by others parallel to the surface of the fovea.
The arrangement at the lower end is somewhat similar.
Ossification (Figs. 217, 218). — The radius is ossified from three centers: one for the body,
and one for either extremity. That for the body makes its appearance near the center of the bone,
during the eighth week of fetal hfe. About the end of the second year, ossification commences
THE CARPUS
221
in the lower end; and at the fifth year, in the upper end. The upper epiphysis fuses with the
body at the age of seventeen or eighteen years, the lower about the age of twenty. An additional
center sometimes found in the radial tuberosity, appears about the fourteenth or fifteenth year.
Appears ai_
fifth year
Bend
■fa^ \ Unites with body
about pvherty
u
Body
I
Appears "'^'C*^^^ T\ Unites with body
second year I ^^^^^ ai)out twentieth
year
Lower extremity
Fig. 217. — -Plan of ossification of the radius.
From three centers.
Fig. 218. — Epiphysial lines of radius in a young
adult. Anterior aspect. The line of attachment of the
articular capsule of the wrist-joint is in blue.
THE HAND.
The skeleton of the hand (Fijjs. 219, 220) is subdivided into three segments: the
carpus or wrist bones; the metacarpus or bones of the palm; and the phalanges or
bones of the digits.
The Carpus (Ossa Carpi).
The carpal bones, eight in number, are arranged in two rows. Those of the
proximal row, from the radial to the ulnar side, are named the navicular, limate,
triangular, and pisiform; those of the distal row, in the same order, are named the
greater multangular, lesser multangular, capitate, and hamate.
Common Characteristics of the Carpal Bones. — Each bone (excepting the pisi-
form) presents six surfaces. Of these the volar or anterior and the dorsal or jmsterior
surfaces are. rough, for ligamentous attachment; the dorsal surfaces being the
broader, except in the navicular and lunate. The superior or yroximal, and inferior
or distal surfaces are articular, the superior generally convex, the inferior concave;
the medial and lateral surfaces are also articular where they are in contact with
contiguous bones, otherwise they are rough and tuberculated. The structure :n
all is similar, viz., cancellous tissue enclosed in a layer of compact bone.
Bones of the Proximal Row (upper row). — The Navicular Bone (os naviculare manus;
scaphoid hone) (Fig. 221).^ — The navicular bone is the largest bone of the proximal
row, and has received its name from its fancied resemblance to a boat. It is situated
at the radial side of the carpus, its long axis being from above downward, lateralward,
and forward. The superior surface is convex, smooth, of triangular shape, and artic-
222
OSTEOLOGY
ulates with the lower end of the radius. The inferior surface, directed downward,
lateralward, and backward, is also smooth, convex, and triangular, and is divided
by a slight ridge into two parts, the lateral articulating with the greater multangu-
lar, the medial with the lesser multangular. On the dorsal surface is a narrow,
rough groove, which runs the entire length of the bone, and serves for the attach-
ment of ligaments. The volar surface is concave above, and elevated at its lower
and lateral part into a rounded projection, the tubercle, which is directed forward
Carfiis
Flexor carpi ulnakis
Flexor digiti quinti brevis
Opponess digiti quinti
Groove for tendon of
Flexor carpi radialis
Opposexs pollicis
Flexor pollicis brevis
y Abductor pollicis
■ LONGDs
Metacarpus
Plexor brevis "\
axd I
Abductor f
digiti quisti. )
Sesamoid
bones
Abductor
pollicis
brevis
FU:X0R DIGITORUM SUBLIMIS
Flexor digitoruii profundus
Fig. 219. — Bones of the left hand. Volar surface.
THE CARPUS
223
and gives attachment to the transverse carpal Hgament and sometimes origin to
a few fibers of the Abductor pollicis brevis. The lateral surface is rough and narrow,
and gives attachment to the radial collateral ligament of the wrist. The medial
siirface presents two articular facets; of these, the superior or smaller is flattened
of semilunar form, and articulates with the lunate bone; the inferior or larger is
concave, forming with the lunate a concavity for the head of the capitate bone.
^<*^^iM;^^
\r- Carptia
Ext. carpi rapialis
LOSGCS
Ext. carpi radialis
BREVIS "7^
Ext. carpi itlnaris
Metacarpus
Ext.
POLLICI?
10NGC3
TTialanges
i'^ Bow
Z^rttm
Ext. diqitorum
coMMrNis and
Ext. indicis
PROPRirS.
i'^Rove
FiQ. 220. — Bones of the left hand. Dorsal surface.
224
OSTEOLOGY
Articulations. — The navicular articulates with five bones: the radius proximally, greater and
lesser multangulars distally, and capitate and lunate medially.
The Lunate Bone {os lunatum; semilunar bone) (Fig. 222). — The lunate bone may
be distinguished by its deep concavity and crescentic outHne. It is situated in
the center of the proximal row of the carpus, between the navicular and triangular.
The superior surface, convex and smooth, articulates with the radius. The inferior
surface is deeply concave, and of greater extent from before backward than trans-
For radius
For lunate
Tubercle
For greater
multangular
For capitate
For lesser multangular
Fig. 221. — The left navicular bone.
versely: it articulates with the head of the capitate, and, by a long, narrow facet
(separated by a ridge from the general surface), with the hamate. The dorsal
and volar surfaces are rough, for the attachment of ligaments, the former being
the broader, and of a somewhat rounded form. The lateral surface presents a
For triangular
For radius
For navicular
For Iiamate For capitate
FiQ. 222.— The left lunate bone.
narrow, flattened, semilunar facet for articulation with the navicular. The medial
surface is marked by a smooth, quadrilateral facet, for articulation with the
triangular.
Articulations. — The lunate articulates witli five bones: the radius proximally, capitate and
hamate distally, navicular laterally, and triangular medially.
Fof pisiform
For lunate
For triangular
Fig. 224. — The left pisiform bone.
For hamate
Fig. 223.— The left triangular bone.
The Triangular Bone (os triquetum; cuneiform hone) (Fig. 223).- — The triangular
bone may be distinguished by its pyramidal shape, and by an oval isolated facet
for articulation with the pisiform bone. It is situated at the upper and ulnar side
of the carpus. The superior surface presents a medial, rough, non-articular portion,
and a lateral convex articular portion which articulates with the triangular articular
disk of the wrist. The inferior surface, directed lateralward, is concave, sinuously
curved, and smooth for articulation with the hamate. The dorsal surface is rough
for the attachment of ligaments. The volar surface presents, on its medial part,
THE CARPUS
225
an oval facet, for articulation with the pisiform; its lateral part is rough for liga-
mentous attachment. The lateral surface, the base of the pyramid, is marked by a
flat, quadrilateral facet, for articulation with the lunatel The medial surface,
the summit of the pyramid, is pointed and roughened, for the attachment of the
ulnar collateral ligament of the wrist.
Articulations.— The triangular articulates with three bones: the lunate laterally, the pisiform
in front, the hamate distally; and with the triangular articular disk which separates it from the
lower end of the ulna.
The Pisiform Bone {os pisiforme) (Fig. 224).— The pisiform bone may be known
by its small size, and by its presenting a single articular facet. It is situated on a
plane anterior to the other carpal bones and is spheroidal in form. Its dorsal
surface presents a smooth, oval facet, for articulation with the triangular: this facet
approaches the superior, but not the inferior border of the bone. The volar surface
is rounded and rough, and gives attachment to the transverse carpal ligament,
and to the Flexor carpi ulnaris and Abductor digiti quinti. The lateral and medial
surfaces are also rough, the former being concave, the latter usually convex.
Articulation. — The pisiform articulates with one bone, the triangular.
Bones of the Distal Row [lower row). — The Greater Multangular Bone {os mul-'
tangulum majus; trapezium) (Fig. 225).— The greater multangular bone may be
distinguished by a deep groove on its volar surface. It is situated at the radial
side of the carpus, between the navicular and the first metacarpal bone. The
superior surface is directed upward and medialward; medially it is smooth, and
articulates with the navicular; laterally it is rough and continuous with the lateral
surface. The inferior surface is oval, concave from side to side, convex from before
backward, so as to form a saddle-shaped surface for articulation with the base
For lesser
multangular
Groove
For 2nd
metacarpal
For navicular
Ridge
For \st metacarpal
Fig. 225. — The left greater multangular bone
For lesser
multangular
For 2iui metacarpal
of the first metacarpal bone. The dorsal surface is rough. The volar surface is
narrow and rough. At its upper part is a deep groove, running from above obliquely
downward and medialward; it transmits the tendon of the Flexor carpi radialis,
and is bounded laterally by an oblique ridge. This surface gives origin to the
Opponens pollicis and to the Abductor and Flexor pollicis brevis; it also affords
attachment to the transverse carpal ligament. The lateral surface is broad and
rough, for the attachment of ligaments. The medial surface presents two facets;
the upper, large and concave, articulates with the lesser multangular; the lower,
small and oval, with the base of the second metacarpal.
Articulations. — -The greater multangular articulates with four bones : the navicular proximally,
the first metacarpal distally, and the lesser multangular and second metacarpal medially.
The Lesser Multangular Bone {os multangulum minus; trapezoid bone) (Fig. 226).
— The lesser multangular is the smallest bone in the distal row. It may be known
by its wedge-shaped form, the broad end of the wedge constituting the dorsal,
the narrow end the volar surface; and by its having four articular facets touching
each other, and separated by sharp edges. The superior surface, quadrilateral,
15
226
OSTEOLOGY
For navicular
Volar
surface
For greater
multan/fular
smooth, and slightly concave, articulates with the navicular. The inferior surface
articulates with the proximal end of the second metacarpal bone; it is convex from
side to side, concave from before backward and subdivided by an elevated ridge into
two unequal facets. The dorsal and volar
surfaces are rough for the attachment of
ligaments, the former being the larger
of the two. The lateral surface, convex
and smooth, articulates with the greater
multangular. The medial surface is con-
cave and smooth in front, for artic-
ulation with the capitate; rough behind,
for the attachment of an interosseous
Dorsal For
surface capitate
Fig. 226. — The left lesser multangular bone
For 2ndr
metacarpal
ligament.
Articulations. — The lesser multangular articulates with four bones : the navicular proximally,
second metacarpal distally, greater multangular laterally; and capitate medially.
The Capitate Bone {os capitatum; os magnum) (Fig. 227). — The capitate bone
is the largest of the carpal bones, and occupies the center of the wrist. It presents,
above, a rounded portion or head, which is received into the concavity formed by
For lunate
Far
navicular
For lesser
multangular
For
hamate '-j^
For 3rd
For 2nd metacarpal
metacarpal
For 4:th metacarpal Volar surface
Fig. 227. — The left capitate bone.
the navicular and lunate; a constricted portion or neck; and below this, the body.
The superior surface is round, smooth, and articulates with the lunate. The inferior
surface is divided by two ridges into three facets, for articulation with the second,
third, and fourth metacarpal bones, that for the third being the largest. The
dorsal surface is broad and rough. The volar surface is narrow, rounded, and rough,
for the attachment of ligaments and a part of the Adductor pollicis obliquus.
For lunai&
For capitate
For triangular
For 4th metacarpal
For 5th metacarpal Hamulus
Fig. 228. — The left hamate bone.
For 5th metacarpal
The lateral surface articulates with the lesser multangular by a small facet at
its anterior inferior angle, behind which is a rough depression for the attach-
ment of an interosseous ligament. Above this is a deep, rough groove, forming
part of the neck, and serving for the attachment of ligaments; it is bounded supe-
riorly by a smooth, convex surface, for articulation with the navicular. The medial
THE METACARPUS 227
surface articulates with the hamate by a smooth, concave, oblong facet, which
occupies its posterior and superior parts; it is rough in front, for the attachment
of an interosseous ligament.
Articulations. — The capitate articulates with seven bones: the navicular and lunate proximally,
the second, third, and fourth metacarpals distally, the lesser multangular on the radial side, and
the hamate on the ulnar side.
The Hamate Bone {os hamaium; unciform bone) (Fig. 228). — The hamate bone
may be readily distinguished by its wedge-shaped form, and the hook-like process
which projects from its volar surface. It is situated at the medial and lower angle
of the carpus, with its base downward, resting on the fourth and fifth metacarpal
bones, and its apex directed upward and lateralward. The superior surface, the
apex of the wedge, is narrow, convex, smooth, and articulates with the lunate.
The inferior surface articulates with the fourth and fifth metacarpal bones, by
concave facets which are separated by a ridge. The dorsal surface is triangular
and rough for ligamentous attachment. The volar surface presents, at its lower
and ulnar side, a curved, hook-like process, the hamulus, directed forward and
lateralward. This process gives attacliment, by its apex, to the transverse carpal
ligament and the Flexor carpi ulnaris; by its medial surface to the Flexor brevis
and Opponens digiti quinti; its lateral side is grooved for the passage of the Flexor
tendons into the palm of the hand. It is one of the four eminences on the front
of the carpus to which the transverse carpal ligament of the wrist is attached;
the others being the pisiform medially, the oblique ridge of the greater multangular
and the tubercle of the navicular laterally. The medial surface articulates with
the triangular bone by an oblong facet, cut obliquely from above, downward
and medialward. The lateral surface articulates with the capitate by its upper
and posterior part, the remaining portion being rough, for the attachment of
ligaments.
Articulations. — The hamate articulates with five bones: the lunate proximally, the fourth
and fifth metacarpals distally, the triangular medially, the capitate laterally.
The Metacarpus.
The metacarpus consists of five cylindrical bones which are numbered from the
lateral side {ossa metacarpalia I-V); each consists of a body and two extremities.
Common Characteristics of the Metacarpal Bones. — The Body (corpus; shaft). —
The body is prismoid in form, and curved, so as to be convex in the longitudinal
direction behind, concave in front. It presents three surfaces: medial, lateral,
and dorsal. The medial and lateral surfaces are concave, for the attachment of
the Interossei, and separated from one another by a prominent anterior ridge.
The dorsal siu-face presents in its distal two-thirds a smooth, triangular, flattened
area which is covered in the fresh state, by the tendons of the Extensor muscles.
This surface is bounded bv two lines, which commence in small tubercles situated
on either side of the digital extremity, and, passing upward, converge and meet
some distance above the center of the bone and form a ridge which runs along the
rest of the dorsal surface to the carpal extremity. This ridge separates two
sloping surfaces for the attachment of the Interossei dorsales. To the tubercles
on the digital extremities are attached the collateral ligaments of the metacarpo-
phalangeal joints.
The Base or Carpal Extremity (baMs) is of a cuboidal form, and broader behind
than in front: it articulates with the carpus, and with the adjoining metacarpal
bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.
The Head or Digital Extremity (capitulwn) presents an oblong surface markedly
convex from before backward, less so transversely, and flattened from side to side;
it articulates with the proximal phalanx. It is broader, and extends farther up-
228
OSTEOLOGY
For greater
mvltangular
For greater
mxdtangvlar
Fig. 229. — The first metacarpal.
(Left.)
ward, on the volar than on the dorsal aspect, and is longer in the antero-posterior
than in the transverse diameter. On either side of the head is a tubercle for the
attachment of the collateral ligament of the metacarpophalangeal joint. The
dorsal surface, broad and flat, supports the Extensor tendons; the volar surface
is grooved in the middle line for the passage of the Flexor tendons, and marked
on either side by an articular eminence continuous with the terminal articular
surface.
Characteristics of the Individual Metacarpal Bones. — The First Metacarpal
Bone ips metacarpale I; metacarpal bone of the thumb) (Fig. 229) is shorter and
stouter than the others, diverges to a greater degree
from the carpus, and its A'olar surface is directed
toward the palm. The body is flattened and broad
on its dorsal surface, and does not present the ridge
which is found on the other metacarpal bones; its
volar surface is concave from above downward. On
its radial border is inserted the Opponens pollicis;
its ulnar border gives origin to the lateral head of
the first Interosseus dorsalis. The base presents a
concavo-convex surface, for articulation with the
greater multangular; it has no facets on its sides, but
on its radial side is a tubercle for the insertion of the
Abductor pollicis longus. The head is less convex
than those of the other metacarpal bones, and is
broader from side to side than from before backward.
On its volar surface are two articular eminences, of
which the lateral is the larger, for the two sesamoid
bones in the tendons of the Flexor pollicis brevis.
The Second Metacarpal Bone {os metacarpale II; metacarpal bone of the index
finger) (Fig. 230) is the longest, and its base the largest, of the four remaining
bones. Its base is prolonged upward and medialward, forming a prominent ridge.
It presents four articular facets: three on the upper surface and one on the ulnar
side. Of the facets on the upper surface the intermediate is the largest and is
concave from side to side, convex from before backward for articulation with the
lesser multangular ; the lateral is small, flat and oval for articulation with the greater
multangular; the medial, on the summit of the ridge, is long and narrow for articu-
lation with the capitate. The facet on the ulnar side articulates with the third
metacarpal. The Extensor carpi radialis longus is inserted on the dorsal surface
and the Flexor carpi radialis on the volar surface of the base.
The Third Metacarpal Bone {os metacarpale III; metacarpal bone of the middle
finger) (Fig. 231) is a little smaller than the second. The dorsal aspect of its
base presents on its radial side a pyramidal eminence, the styloid process, which
extends upward behind the capitate; immediately distal to this is a rough surface
for the attachment of the Extensor carpi radialis brevis. The carpal articular
facet is concave behind, flat in front, and articulates with the capitate. On the
radial side is a smooth, concave facet for articulation with the second metacarpal,
and on the ulnar side two small oval facets for the fourth metacarpal.
The Fourth Metacarpal Bone {os metacarpale IV; metacarpal bone of the ring
finger) (Fig. 232) is shorter and smaller than the third. The base is small and
quadrilateral; its superior surface presents two facets, a large one medially for
articulation with the hamate, and a small one laterally for the capitate. On the
radial side are two oval facets, for articulation with the third metacarpal ; and on
the ulnar side a single concave facet, for the fifth metacarpal.
The Fifth Metacarpal Bone {os metacarpale V; metacarpal bone of the little finger)
(Fig. 233) presents on its base one facet on its superior surface, which is concavo-
THE METACARPUS
229
convex and articulates with the hamate, and one on its radial side, which articuhates
with the fourth metacarpal. On its ulnar side is a prominent tubercle for the inser-
tion of the tendon of the Extensor carpi ulnaris. The dorsal surface of the body
For greater
For le.iser multangular
multangular
For 6rd
metacarpal For For lesser
capitate mult-
angular
Fio. 230. — The second metacarpal. (Left.)
Styloid For 2nd For For ^ih
process meta- capitate metacarpal
carpal
Fig. 231. — The third metacarpal. (Left.)
is divided by an oblique ridge, which extends from near the ulnar side of the base
to the radial side of the head. The lateral part of this surface serves for the attach-
ment of the fourth Interosseus dorsalis; the medial part is smooth, triangular, and
covered by the Extensor tendons of the little finger.
For ^ / ^'or 5th
capitate ^("' '^''^ ^or meta-
metacarjMl hamate carpal
Fig. 232. — The fourth metacarpal. (Left.)
For 4th
metacarpal
For hamate
Fig. 233. — The fifth metacarpal. (Left.)
Articulations. — Besides their phalangeal articulations, the metacarpal bones articulate as
follows: the first with the greater multangular; the second with the greater multangular, lesser
multangular, capitate and third metacarpal; the third with the capitate and second and fourth
metacarpals; the fourth with the capitate, hamate, and third and fifth metacarpals; and the
fifth with the hamate and fourth metacarpal.
230
OSTEOLOGY
The Phalanges of the Hand (Phalanges Digitorum Manus).
The phalanges are fourteen in number, three for each finger, and two for the
thumb. Each consists of a body and two extremities. The body tapers from above
downward, is convex posteriorly, concave in front from above downward, fiat
from side to side; its sides are marked by rough ridges which give attachment
to the fibrous sheaths of the Flexor tendons. The proximal extremities of the bones
of the first row present oval, concave articular surfaces, broader from side to side
than from before backward. The proximal extremity of each of the bones of the
second and third rows presents a double concavity separated by a median ridge.
The distal extremities are smaller than the proximal, and each ends in two condyles
separated by a shallow groove; the articular surface extends farther on the volar
than on the dorsal surface, a condition best marked in the bones of the first row.
The ungual phalanges are convex on their dorsal and flat on their volar surfaces;
they are recognized by their small size, and by a roughened, elevated surface of
a horseshoe form on the volar surface of the distal extremity of each which serves
to support the sensitive pulp of the finger.
CARPUS
One center for each bone :
All curlilaginous at birth
METACARI'ALS OF FINGERS
Tivo centers for each bone .
One for body
One for head
PHALANGES
Two centers for each bone
One for body
One for proximal
extremity
^~.p-\ tini/f 18 20'ty^
lip I Sl*;vk
Off
S'.'iujS
Js
Pia. 234. — Plan of ossification of the hand.
Articulations. — In the four fingers the phalanges of the first row articulate with those of the
second row and with the metacarpals; the phalanges of the second row with those of the first
and third rows, and the ungual phalanges with those of the second row. In the thumb, which
has only two phalanges, the first phalanx articulates by its proximal extremity with the meta-
carpal bone and by its distal with the ungual phalanx.
Ossification of the Bones of the Hand.- — The carpal bones are each ossified from a single center,
and ossification proceeds in the following order (Fig. 2 34): in the capitate and hamate, during
THE HIP BONE 231
the first year, the former preceding the latter; in the triangular, during the third year; in the
lunate and greater multangular, during the fifth year, the former preceding the latter; in the
navicular, during the sixth year; in the lesser multangular, during the eighth year; and in
the pisiform, about the twelfth year
Occasionally an additional bone, the os centrale, is found on the back of the carpus, lying
between the navicular, lesser multangular, and capitate. During the second month of fetal hfe
it is represented by a small cartilaginous nodule, which usually fuses with the cartilaginous navic-
ular. Sometimes the styloid process of the third metacarpal is detached and forms an additional
ossicle.
The metacarpal bones are each ossified from two centers: one for the body and one for the
distal extremity of each of the second, third, fourth, and fifth bones; one for the body and one
for the base of the first metacarpal bone.^ The first metacarpal bone is therefore ossified in the
same manner as the phalanges, and this has led some anatomists to regard the thumb as being
made up of three phalanges, and not of a metacarpal bone and two phalanges. Osssification com-
mences in the middle of the body about the eighth or ninth week of fetal hfe, the centers for the
second and third metacarpals being the first, and that for the first metacarpal, the last, to appear;
about the third year the distal extremities of the metacarpals of the fingers, and the base of the
metacarpal of the thumb, begin to ossify; they unite with the bodies about the twentieth year.
The phalanges are each ossified from two centers: one for the body, and one for the proximal
extremity. Ossification begins in the body, about the eighth week of fetal life. Ossification of
the proximal extremity commences in the bones of the first row between the third and fourth
years, and a year later in those of the second and third rows. The two centers become united
in each row between the eighteenth and twentieth years.
In the ungual phalanges the centers for the bodies appear at the distal extremities of the
phalanges, instead of at the middle of the bodies, as in the other phalanges. Moreover, of all
the bones of the hand, the ungual phalanges are the first to ossify.
THE BONES OF THE LOWER EXTREMITY (OSSA EXTREMITATIS INFERIORIS).
The Hip Bone (Os Coxse; Innominate Bone).
The hip bone is a large, flattened, irregularly shaped bone, constricted in the
center and expanded above and below. It meets its fellow on the opposite side
in the middle line in front, and together they form the sides and anterior wall of
the pelvic cavity. It consists of three parts, the ilium, ischium, and pubis, which
are distinct from each other in the young subject, but are fused in the adult;
the union of the three parts takes place in and around a large cup-shaped articular
cavity, the acetabulum, which is situated near the middle of the outer surface of the
bone. The ilium, so-called because it supports the flank, is the superior broad and
expanded portion which extends upward from the acetabulum. The ischium is the
lowest and strongest portion of the bone; it proceeds downward from the acetab-
ulum, expands into a large tuberosity, and then, curving forward, forms, with
the pubis, a large aperture, the obturator foramen. The pubis extends medialward
and downward from the acetabulum and articulates in the middle line with the
bone of the opposite side : it forms the front of the pelvis and supports the external
organs of generation.
The lUum (os ilii). — The ilium is divisible into two parts, the body and the
ala ; the separation is indicated on the internal surface by a curved line, the arcuate
line, and on the external surface by the margin of the acetabulum.
The Body {corpus oss. ilii). — The body enters into the formation of the acetab-
ulum, of which it forms rather less than two-fifths. Its external surface is partly
articular, partly non-articular; the articular segment forms part of the lunate
surface of the acetabulum, the non-articular portion contributes to the acetabular
fossa. The internal surface of the body is part of the wall of the lesser pelvis and
gives origin to some fibers of the Obturator internus. Below, it is continuous with
the pelvic surfaces of the ischium and pubis, only a faint line indicating the place
of union.
' Allen Thomson demonstrated the fact that the first metacarpal bone is often developed from three o_enters: that is
to say, there is a separate nucleus for the distal end, forming a distinct epiphysis visible at the age of seven or eight
years. He also stated that there are traces of a proximal epiphysis in the second metacarpal bone. Journal of Anatomy
and Physiology, 1869.
232
OSTEOLOGY
The Ala {ala oss. ilii). — The ala is the large expanded portion which bounds
the greater pelvis laterally. It presents for examination two surfaces — ^an external
and an internal — a crest, and two borders- — an anterior and a posterior. The
external surface (Fig. 235), known as the dorsum ilii, is directed backward and lateral-
ward behind, and downward and lateralward in front. It is smooth, convex in front,
Ant. superior
spine
Posterior
superior
spine
— Anterior inferior spine
Posterior
inferior
spine
Articular capsule
Ligament um teres
Gemellus superior
Spine of ischium—
Gemellus inferior
Rectus
abdominis
Pyramidalis
Adductor
longus
Fig. 235. — Right hip bone. External surface.
deeply concave behind; bounded above by the crest, below by the upper border
of the acetabulum, in front and behind by the anterior and posterior borders.
This surface is crossed in an arched direction by three lines — the posterior, anterior,
and inferior gluteal lines. The posterior gluteal line (superior curved line), the short-
est of the three, begins at the crest, about 5 cm. in front of its posterior ex-tremity;
it is at first distinctly marked, but as it passes downward to the upper part of the
THE HIP BONE
233
greater sciatic notch, where it ends, it becomes less distinct, and is often altogether
lost. Behind this line is a narrow semilunar surface, the upper part of which
is rough and gives origin to a portion of the Gluteus maximus; the lower part is
smooth and has no muscular fibers attached to it. The anterior gluteal Une (middle
curved line), the longest of the three, begins at the crest, about 4 cm. behind its
anterior extremity, and, taking a curved direction downward and backward, ends
Levator ani
Constrictor vrethroe
Transversus perinoei superfic,
Crus penis Ischiocavernosus
FiQ. 236. — Right hip bone. Internal surface.
at the upper part of the greater sciatic notch. The space between the anterior
and posterior gluteal lines and the crest is concave, and gives origin to the Glutseus
medius. Xear the middle of this line a nutrient foramen is often seen. The
inferior gluteal line {inferior curved line), the least distinct of the three, begins in
front at the notch on the anterior border, and, curving backward and downward,
ends near the middle of the greater sciatic notch. The surface of bone included
234 OSTEOLOGY
between the anterior and inferior gluteal lines is concave from above downward,
convex from before backward, and gives origin to the Glutfeus minimus. Between
the inferior gluteal line and the upper part of the acetabulum is a rough, shallow
g^oo^•e, from which the reflected tendon of the Rectus femoris arises.
The internal surface (Fig. 236) of the ala is bounded above by the crest, below,
by the arcuate line; in front and behind, by the anterior and posterior borders.
It presents a large, smooth, concave surface, called the iliac fossa, which gives
origin to the Iliacus and is perforated at its inner part by a nutrient canal; and
below this a smooth, rounded border, the arcuate line, which runs downward, for-
ward, and medialward. Behind the iliac fossa is a rough surface, divided into two
portions, an anterior and a posterior. The anterior surface (auricular surface),
so called from its resemblance in shape to the ear, is coated with cartilage in the
fresh state, and articulates with a similar surface on the side of the sacrum.
The posterior portion, known as the iliac tuberosity, is elevated and rough, for
the attachment of the posterior sacroiliac ligaments and for the origins of the
Sacrospinalis and ]Multifidus. Below and in front of the auricular surface is the
preauricular sulcus, more commonly present and better marked in the female
than in the male; to it is attached the pelvic portion of the anterior sacroiliac
ligament.
The crest of the ilium is convex in its general outline but is sinuously curved,
being concave inward in front, concave outward behind. It is thinner at the center
than at the extremities, and ends in the anterior and posterior superior iliac spines.
The surface of the crest is broad, and divided into external and internal lips,
and an intermediate line. About 5 cm. behind the anterior superior iliac spine
there is a prominent tubercle on the outer lip. To the external lip are attached
the Tensor' fasciae latse, Obliquus externus abdominis, and Latissimus dorsi, and
along its whole length the fascia lata ; to the intermediate line the Obliquus internus
abdominis; to the internal lip, the fascia iliaca, the Transversus abdominis,
Quadratus lumborum, Sacrospinalis, and Iliacus.
The anterior border of the ala is concave. It presents two projections, separated
by a notch. Of these, the uppermost, situated at the junction of the crest and
anterior border, is called the anterior superior iliac spine; its outer border gives
attachment to the fascia lata, and the Tensor fasciie lattv, its inner border, to the
Iliacus; while its extremity affords attachment to the inguinal ligament and gives
origin to the Sartorius. Beneath this eminence is a notch from which the Sartorius
takes origin and across which the lateral femoral cutaneous nerve passes. Below
the notch is the anterior inferior iliac spine, which ends in the upper lip of the
acetabulum; it gives attachment to the straight tendon of the Rectus femoris and
to the iliofemoral ligament of the hip-joint. Medial to the anterior inferior spine
is a broad, shallow groove, over which the Iliacus and Psoas major pass. This
groove is boimded medially by an eminence, the iliopectineal eminence, which
marks the point of union of the ilium and pubis.
The posterior border of the ala, shorter than the anterior, also presents two
projections separated by a notch, the posterior superior iliac spine and the posterior
inferior iliac spine. The former serves for the attachment of the oblique portion
of the posterior sacroiliac ligaments and the Multifidus; the latter corresponds
with the posterior extremity of the auricular surface. Below the posterior inferior
spine is a deep notch, the greater sciatic notch.
The Ischium (os ischii). — The ischium forms the lower and back part of the
hip bone. It is divisible into three portions — a body and two rami.
The Body (corpus oss. ischii). — The body enters into and constitutes a little
more than two-fifths of the acetabulum. Its external surface forms part of the
lunate surface of the acetabulum and a portion of the acetabular fossa. Its internal
surface is part of the wall of the lesser pelvis; it gives origin to some fibers of the
THE HIP BONE 235
Obturator internus. Its anterior border projects as the posterior obturator tubercle;
from its posterior border there extends backward a thin and pointed triangular
eminence, the ischial spine, more or less elongated in different subjects. The
external surface of the spine gives attachment to the Gemellus superior, its internal
surface to the Coccygeus, Levator ani, and the pelvic fascia; while to the pointed
extremity the sacrospinous ligament is attached. Above the spine is a large notch,
the greater sciatic notch, converted into a foramen by the sacrospinous ligament;
it transmits the Piriformis, the superior and inferior gluteal vessels and nerves,
the sciatic and posterior femoral cutaneous nerves, the internal pudendal vessels,
and nerve, and the nerves to the Obturator internus and Quadratus femoris. Of
these, the superior gluteal vessels and nerve pass out above the Piriformis, the
other structures below it. Below the spine is a smaller notch, the lesser sciatic
notch; it is smooth, coated in the recent state with cartilage, the surface of which
presents two or three ridges corresponding to the subdivisions of the tendon of
the Obturator internus, which winds over it. It is converted into a foramen by
the sacrotuberous and sacrospinous ligaments, and transmits the tendon of the
Obturator internus, the nerve which supplies that muscle, and the internal
pudendal vessels and nerve.
The Superior Ramus (ramus superior oss. ischii; descending ramus). — The
superior ramus projects downward and backward from the body and presents
for examination three surfaces: external, internal, and posterior. The external
surface is quadrilateral in shape. It is bounded above by a groove which lodges
the tendon of the Obturator externus; below, it is continuous with the inferior
ramus; in front it is limited by the posterior margin of the obturator foramen;
behind, a prominent margin separates it from the posterior surface. • In front of
this margin the surface gives origin to the Quadratus femoris, and anterior to this
to some of the fibers of origin of the Obturator externus; the lower part of the sur-
face gives origin to part of the Adductor magnus. The internal surface forms part
of the bony wall of the lesser pelvis. In front it is limited by the posterior margin
of the obturator foramen. Below, it is bounded by a sharp ridge which gives
attachment to a falciform prolongation of the sacrotuberous ligament, and, more
anteriorly, gives origin to the Transversus perina^i and Ischiocavernosus. Poste-
riorly the ramus forms a large swelling, the tuberosity of the ischium, which is divided
into two portions: a lower, rough, somewhat triangular part, and an upper, smooth,
quadrilateral portion. The lower portion is subdivided by a prominent longitudinal
ridge, passing from base to apex, into two parts; the outer gives attachment to
the Adductor magnus, the inner to the sacrotuberous ligament. The upper portion
is subdivided into two areas by an oblique ridge, which runs downward and out-
ward; fiom the upper and outer area the Semimembranosus arises; from the lower
and inner, the long head of the Biceps femoris and the Semitendinosus.
The Inferior Ramus (ramus inferior oss. ischii; ascending ramus).- — The inferior
ramus is the thin, flattened part of the ischium, which ascends from the superior
ramus, and joins the inferior ramus of the pubis — the junction being indicated in
the adult by a raised line. The outer siu:f ace is uneven for the origin of the Obturator
externus and some of the fibers of the Adductor magnus; its inner surface forms
part of the anterior wall of the pelvis. Its medial border is thick, rough, slightly
everted, forms part of the outlet of the pelvis, and presents two ridges and an
intervening space. The ridges are continuous with similar ones on the inferior
ramus of the pubis: to the outer is attached the deep layer of the superficial peri-
neal fascia (fascia of Colles), and to the inner the inferior fascia of the urogenital
diaphragm. If these two ridges be traced downward, they will be found to join
with each other just behind the point of origin of the Transversus perina^i; here
the two layers of fascia are continuous behind the posterior border of the muscle.
To the intervening space, just in front of the point of junction of the ridges, the
236 OSTEOLOGY
Transversus perineal is attached, and in front of this a portion of the cms penis
vel cHtoridis and the Ischiocavernosus. Its lateral border is thin and sharp, and
forms part of the medial margin of the obturator foramen.
The Pubis {os jyubis). — The pubis, the anterior part of the hip bone, is divisible
into a body, a superior and an inferior ramus.
The Body {corpus oss. pubis). — The body forms one-fifth of the acetabulum,
contributing by its external surface both to the lunate surface and the acetabular
fossa. Its internal surface enters into the formation of the wall of the lesser pelvis
and gives origin to a portion of the Obturator internus.
The Superior Ramus (ramus superior oss. pubis; ascending ramus). — The superior
ramus extends from the body to the median plane where it articulates with its
fellow of the opposite side. It is conveniently described in two portions, viz., a
medial flattened part and a narrow lateral prismoid portion.
The Medial Portion of the superior ramus, formerly described as the body of
the pubis, is somewhat quadrilateral in shape, and presents for examination two
surfaces and three borders. The anterior surface is rough, directed downward and
outward, and serves for the origin of various muscles. The Adductor longus arises
from the upper and medial angle, unmediately below the crest; lower down, the
Obturator externus, the Adductor brevis, and the upper part of the Gracilis take
origin. The posterior surface, convex from above downward, concave from side
to side, is smooth, and forms part of the anterior wall of the pelvis. It gives origin
to the Levator ani and Obturator internus, and attachment to the puboprostatic
ligaments and to a few muscular fibers prolonged from the bladder. The upper
border presents a prominent tubercle, the pubic tubercle (pubic spine), which pro-
jects forward; the inferior cms of the subcutaneous inguinal ring (external abdominal
ring), and the inguinal ligament (Pouparfs ligament) are attached to it. Passing
upward and lateralward from the pubic tubercle is a well-defined ridge, forming
a part of the pectineal line which marks the brim of the lesser pelvis: to it are
attached a portion of the inguinal falx (conjoined tendon of Obliquus internus
and Transversus), the lacunar ligament (Gimbernafs ligament), and the reflected
inguinal ligament (triangular fascia). Medial to the pubic tubercle is the crest,
which extends from this process to the medial end of the bone. It affords attach-
ment to the inguinal falx, and to the Rectus abdominis and Pyramidalis. The
point of junction of the crest with the medial border of the bone is called the angle;
to it, as well as to the symphysis, the superior cms of the subcutaneous inguinal
ring is attached. The medial border is articular; it is oval, and is marked by eight
or nine transverse ridges, or a series of nipple-like processes arranged in rows,
separated by grooves; they serve for the attachment of a thin layer of cartilage,
which intervenes between it and the interpubic fibrocartilaginous lamina. The
lateral border presents a sharp margin, the obtinator crest, which forms part of the
circumference of the obturator foramen and affords attachment to the obturator
membrane.
The Lateral Portion of the ascending ramus has three surfaces: superior, inferior,
and posterior. The superior surface presents a continuation of the pectineal line,
already mentioned as commencing at the pubic tubercle. In front of this line, the
surface of bone is triangular in form, wider laterally than medially, and is covered
by the Pectineus. The surface is bounded, laterally, by a rough eminence, the
iliopectineal eminence, which serves to indicate the point of junction of the ilium
and pubis, and below by a prominent ridge which extends from the acetabular
notch to the pubic tubercle. The inferior surface forms the upper boundary of
the obturator forailien, and presents, laterally, a broad and deep, oblique groove,
for the passage of the obturator vessels and nerve; and medially, a sharp margin,
the obturator crest, forming part of the circumference of the obturator foramen,
and giving attachment to the obturator membrane. The posterior surface consti-
I
THE HIP BONE 237
tutes part of the anterior boundary of the lesser pelvis. It is smooth, convex from
above downward, and affords origin to some fibers of the Obturator intornus.
The Inferior Ramus {ramus infer ior oss. pubis; descending rmnus) .—The inferior
ramus is thin and flattened. It passes lateralward and downward from the medial
end of the superior ramus; it becomes narrower as it descends and joins with the
inferior ramus of the ischium below the obturator foramen. Its anterior surface
is rough, for the origin of muscles — the Gracilis along its medial border, a portion
of the Obturator externus where it enters into the formation of the obturator
foramen, and between these two, the Adductores brevis and magnus, the former
being the more medial. The posterior surface is smooth, and gives origin to the
Obturator internus, and, close to the medial margin, to the Constrictor urethrjp.
The medial border is thick, rough, and everted, especially in females. It presents
two ridges, separated by an intervening space. The ridges extend downward, and
are continuous with similar ridges on the inferior ramus of the ischium; to the
external is attached the fascia of Colles, and to the internal the inferior fascia of
the urogenital diaphragm. The lateral border is thin and sharp, forms part of the
circumference of the obturator foramen, and gives attachment to the obturator
membrane.
The Acetabulum {cotyloid cavity). — The acetabulum is a deep, cup-shaped, hemi-
spherical depression, directed downward, lateralward, and forward. It is formed
medially by the pubis, above by the ilium, laterally and below by the ischium;
a little less than two-fifths is contributed bv the ilium, a little more than two-
fifths by the ischium, and the remaining fifth by the pubis. It is bounded by a
prominent uneven rim, which is thick and strong above, and serves for the attach-
ment of the glenoidal labrum (cotyloid ligament), which contracts its orifice, and
deepens the surface for articulation. It presents below a deep notch, the acetabular
notch, which is continuous with a circular non-articular depression, the acetabular
fossa, at the bottom of the cavity: this depression is perforated by numerous
apertures, and lodges a mass of fat. The notch is converted into a foramen by
the transverse ligament; through the foramen nutrient vessels and nerves enter
the joint; the margins of the notch serve for the attachment of the ligamentum
teres. The rest of the acetabulum is formed by a curved articular surface, the
lunate surface, for articulation with the head of the femur.
The Obturator Foramen {foramen obturatum; thyroid foramen). — The obturator
foramen is a large aperture, situated between the ischium and pubis. In the male
it is large and of an oval form, its longest diameter slanting obliquely from before
backward; in the female it is smaller, and more triangular. It is bounded by a
thin, uneven margin, to which a strong membrane is attached, and presents,
superiorly, a deep groove, the obturator groove, which runs from the pelvis obliquely
medialward and downward. This groove is converted into a canal by a ligamentous
band, a specialized part of the obturator membrane, attached to two tubercles:
one, the posterior obturator tubercle, on the medial border of the ischium, just in
front of the acetabular notch; the other, the anterior obturator tubercle, on the
obturator crest of the superior ramus of the pubis. Through the canal the
obturator vessels and nerve pass out of the pelvis.
Structure.— The thicker parts of the bone consist of cancellous tissue, enclosed between two
layers of compact tissue; the thinner parts, as at the bottom of the acetabulum and center of
the iliac fossa, are usually semitransparent, and composed entirely of compact tissue.
Ossification (Fig. 237).— The hip bone is ossified from eight centers: three primary— one each
for the ihum, ischium, and pubis; and five secondary — one each for the crest of the ilium, the
anterior inferior spine (said to occur more frequently in the male than in the female), the tuberosity
of the ischium, the pubic symphysis (more frequent in the female than in the male), and one or
more for the Y-shaped piece at the bottom of the acetabulum. The centers appear in the follow-
ing order: in the lower part of the ihum, immediately above the greater sciatic notch, about
the eighth or ninth week of fetal life; in the superior ramus of the ischium, about the third month;
238
OSTEOLOGY
in the superior ramus of the pubis, between the fourth and fifth months. At birth, the three
primary centers are quite separate, the crest, the bottom of the acetabulum, the ischial tuberosity,
and the inferior rami of the ischium and pubis being still cartilaginous. By the seventh or eighth
year, the inferior rami of the pubis and ischium are almost completely united by bone. About
the thirteenth or fourteenth year, the three primary centers have extended their growth into the
bottom of the acetabulum, and are there separated from each other by a Y-shaped portion of
cartilage, which now presents traces of ossification, often by two or more centers. One of these,
the OS acetabuli, appears about the age of twelve, between the ilium and pubis, and fuses with them
about the age of eighteen; it forms the pubic part of the acetabulum. The iUum and ischium
then become joined, and lastly the pubis and ischium, through the intervention of this Y-shaped
portion. At about the age of puberty, ossification takes place in each of the remaining portions,
and they join with the rest of the bone between the twentieth and twenty-fifth years. Separate
centers are frequently found for the pubic tubercle and the ischial spine, and for the crest and
angle of the pubis.
Articulations. — The hip bone articulates with its fellow of the opposite side, and with the
sacrum and femur.
By eight centers \ ^J"'^^ Wirmry {Ilium. Ischium, and Pubis)
" •' I Five secondary
C '-c^^
7Tuh
Fig. 237. — Plao of ossification of the hip bone. The three primary centers unite through a Y-shaped piece about
puberty. Epiphyses appear about puberty, and unite about twenty-fifth year.
The Pelvis.
The pelvis, so called from its resemblance to a basin, is a bony ring, interposed
between the movable vertebrae of the vertebral column which it supports, and the
lower limbs upon which it rests; it is stronger and more massively constructed
than the wall of the cranial or thoracic cavities, and is composed of four bones:
the two hip bones laterally and in front and the sacrum and coccyx behind.
The pelvis is divided by an oblique plane passing through the prominence of
the sacrum, the arcuate and pectineal lines, and the upper margin of the symphysis
pubis, into the greater and the lesser pelvis. The circumference of this plane is
termed the linea terminalis or pelvic brim.
The Greater or False Pelvis {yehis major). — The greater pelvis is the expanded
portion of the cavity situated above and in front of the pelvic brim. It is bounded
on either side by the ilium; in front it is incomplete, presenting a wide interval
between the anterior borders of the ilia, which is filled up in the fresh state by
THE PELVIS
239
the parietes of the abdomen; behind is a deep notch on either side between the ilium
and the base of the sacrum. It supports the intestines, and transmits part of their
weight to the anterior wall of the abdomen.
The Lesser or True Pelvis (pelvis minor)— The lesser pelvis is that part of the
pelvic cavity which is situated below and behind the pelvic brim. Its bony walls
are more complete than those of the greater pelvis. For convenience of descrip-
tion, it is divided into an_ inlet bounded by tlie superior circumference, and outlet
bounded by the inferior circumference, and a cavity.
The Superior Circumference.— The superior circumference forms the brim of the
pelvis, the included space being called the superior aperture or inlet (apertura pelvis
[minoris] superior) (Fig. 238). It is formed laterally by the pectineal and arcuate
lines, in front by the crests of the pubes, and behind by the anterior margin of the
base of the sacrum and sacrovertebral angle. The superior aperture is somewhat
heart-shaped, obtusely pointed in front, diverging on either side, and encroached
upon behind by the projection forward of the promontory of the sacrum. It has
three principal diameters: antero-posterior, transverse, and oblique. The antero-
posterior or conjugate diameter extends from the sacrovertebral angle to the sym-
Fig. 238. — Diameters of .superior aperture of lesser pelvis (female).
physis pubis; its average measurement is about 110 mm. in the female. The
transverse diameter extends across the greatest width of the superior aperture,
from the middle of the brim on one side to the same point on the opposite; its aver-
age measurement is about 135 mm. in the female. The oblique diameter extends
from the iliopectineal eminence of one side to the sacroiliac articulation of the
opposite side; its average measurement is about 125 mm. in the female.
The cavity of the lesser pehis is bounded in front and below b}'- the pubic sym-
physis and the superior rami of the pubes ; above and behind, by the pelvic surfaces
of the sacrum and coccyx, which, curving forward above and below, contract
the superior and inferior apertures of the cavity; laterally, by a broad, smooth,
quadrangular area of bone, corresponding to the inner surfaces of the body and
superior ramus of the ischium and that part of the ilium which is below the arcuate
line. From this description it will be seen that the cavity of the lesser pelvis
is a short, curved canal, considerably deeper on its posterior than on its anterior
wall. It contains, in the fresh subject, the pelvic colon, rectum, bladder, and some
of the organs of generation. The rectum is placed at the back of the pelvis, in
the curve of the sacrum and coccyx; the bladder is in front, behind the pubic sym-
physis. In the female the uterus and vagina occupy the interval between these viscera.
240
OSTEOLOGY
The Lower Circumference.^The lower circumference of the pelvis is very irregular;
the space enclosed by it is named the inferior aperture or outlet (apertura pelvis
[minoris] inferior) (Fig. 239), and is bounded behind by the point of the coccjtc,
and laterally by the ischial tuberosities. These eminences are separated by three
notches: one in front, the pubic arch, formed by the convergence of the inferior
Fig. 239. — Diameters of inferior aperture of lesser pelvis (female).
rami of the ischium and pubis on either side. The other notches, one on either
side, are formed by the sacrum and coccyx behind, the ischium in front, and
the ilium above; they are called the sciatic notches; in the natural state they are
converted into foramina by the sacrotuberous and sacrospinous ligaments. When
the ligaments are in situ, the inferior aperture of the pelvis is lozenge-shaped,
bounded, in front, by the pubic arcuate ligament
and the inferior rami of the pubes and ischia; later-
ally, by the ischial tuberosities; and behind, by the
sacrotuberous ligaments and the tip of the coccyx.
The diameters of the outlet of the pelvis are two,
antero-posterior and transverse. The antero-posterior
diameter extends from the tip of the coccyx to the
lower part of the pubic symphysis; its measurement
is from 90 to 115 mm. in the female. It varies with
the length of the coccyx, and is capable of increase
or diminution, on account of the mobility of that
bone. The transverse diameter, measured between
the posterior parts of the ischial tuberosities, is about
115 mm. in the female. ^
Axes (P'ig. 240). — A line at right angles to the plane
of the superior aperture at its center would, if prolonged,
pass through the umbilicus above and the middle
of the coccyx below ; the axis of the superior aperture
is therefore directed downward and backward. The
axis of the inferior aperture, produced upward, would
touch the base of the sacrum, and is also directed
downward, and slightly backward. The axis of the cavity — i. e., an axis at right
angles to a series of planes between those of the superior and inferior apertures
1 The measurements of the pehns given above are fairly accurate, but different figures are given by various authors
no doubt due mainly to differences in the physique and stature of the population from whom the measurements have
been taken.
Fio.
240. — Median sagittal section of
pelvis.
THE PELVIS
241
— is curved like the cavity itself: this curve corresponds to the concavity of the
sacrum and coccyx, the extremities being indicated by the central points of the
superior and inferior apertures. A knowledge of the direction of these axes
serves to explain the course of the fetus in its passage through the pelvis during
parturition.
Position of the Pelvis (Fig. 240).— In the erect posture, the pelvis is placed
obliquely with regard to the trunk: the plane of the superior aperture forms an
angle of from 50° to 60°, and that of the inferior aperture one of about 15° with
the horizontal plane. The pelvic surface of the symphysis pubis looks upward
and backward, the concavity of the sacrum and coccyx downward and forward.
The position of the pelvis in the erect posture may be indicated by holding it so
that the anterior superior iliac spines and the front of the top of the symphysis
pubis are in the same vertical plane.
Fia. 241. — Male pelvis.
Differences between the Male and Female Pelves. — The female pelvis (Fig.
242) is distinguished from that of the male (Fig. 241) by its bones being more
delicate and its depth less. The whole pehis is less massive, and its muscular
impressions are slightly marked. The ilia are less sloped, and the anterior iliac
spines more widely separated; hence the greater lateral prominence of the hips.
The preauricular sulcus is more commonly present and better marked. The supe-
rior aperture of the lesser pelvis is larger in the female than in the male; it is more
nearly circular, and its obliquity is greater. The cavity is shallower and wider;
the sacrum is shorter Avider, and its upper part is less curved; the obturator
foramina are triangular in shape and smaller in size than in the male. The inferior
aperture is larger and the coccyx more movable. The sciatic notches are wider
and shallower, and the spines of the ischia project less inward. The acetabula
are smaller and look more distinctly forward (Derry^). The ischial tuberosities
and the acetabula are wider apart, and the former are more everted. The pubic
symphysis is less deep, and the pubic arch is wider and more rounded than in the
male, Avhere it is an angle rather than an arch.
> Journal of .\natomy and Physiology, vol. xliii.
16
242
OSTEOLOGY
The size of the pelvis varies not only in the two sexes, but also in different
members of the same sex, and does not appear to be influenced in any way by the
height of the individual. Women of short stature, as a rule, have broad pelves.
Occasionally the pelvis is equally contracted in all its dimensions, so much so
that all its diameters measure 12.5 mm. less than the average, and this even in
well-formed women of average height. The principal divergences, however, are
found at the superior aperture, and affect the relation of the antero-posterior
to the transverse diameter. Thus the superior aperture may be elliptical either
in a transverse or an antero-posterior direction, the transverse diameter in the
former, and the antero-posterior in the latter, greatly exceeding the other diameters;
in other instances it is almost circular.
Fig. 242. — Female pelvis.
In the fetus, and for several years after birth, the pelvis is smaller in proportion
than in the adult, and the projection of the sacrovertebral angle less marked.
The characteristic differences between the male and female pelvis are distinctly
indicated as early as the fourth month of fetal life.
Abnormalities. — There is arrest of development in the bones of the pelvis in cases of extro-
version of the bladder; the anterior part of the pelvic girdle is deficient, the superior rami of
the pubes are imperfectly developed, and the symphysis is absent. "The pubic bones are sepa-
rated to the extent of from two to four inches, the superior rami shortened and directed forward,
and the obturator foramen diminished in size, narrowed, and turned outward. The iliac bones
are straightened out more than normal. The sacrum is very peculiar. The lateral curve, instead
of being concave, is flattened out or even convex, with the iliosacral facets turned more outward
than normal, while the vertical curve is straightened."^
The Femur (Thigh Bone).
The femur (Figs. 244, 245), the longest and strongest bone in the skeleton, is
almost perfectly cylindrical in the greater part of its extent. In the erect posture
it is not vertical, being separated above from its fellow by a considerable interval,
which corresponds to the breadth of the pelvis, but inclining gradually downward
and medialward, so as to approach its fellow toward its lower part, for the purpose
of bringing the knee-joint near the line of gravity of the body. The degree of this
inclination varies in different persons, and is greater in the female than in the male,
> Wood, Heath's Dictionary of Practical Surgery, i, 426.
THE FEMUR
243
on account of the greater breadth of the pelvis. The femur, like other long bones,
is divisible into a body and two extremities.
The Upper Extremity (proxiinal extremity, Fig. 243).— The upper extremity
presents for examination a head, a neck, a greater and a lesser trochanter.
The Head {caput femoris) .—The head which is globular and forms rather more
than a hemisphere, is directed upward, medialward, and a little forward, the greater
part of its convexity being above and in front. Its surface is smooth, coated with
cartilage in the fresh state, except over an ovoid depression, the fovea capitis
femoris, which is situated a little below and behind the center of the head, and gives
attaclmient to the ligamentum teres.
The Neck {collum femoris).— The neck is a flattened pyramidal process of bone,
connecting the head with the body, and forming with the latter a wide angle open-
ing medialward. The angle is wildest in infancy, and becomes lessened during
growth, so that at puberty it forms a gentle curve from the axis of the body of the
bone. In the adult, the neck forms an angle of about 125° with the body, but this
varies in inverse proportion to the development of the pelvis and the stature. In
Obturator internus and Oemelli
Piriformis
Insertion of Obturator
Fovea capitis,
Jor lig, teres
, t, j^^ T-r ■ Cheater trochanter
externus
Lesser trochanter
Fio. 243. — Upper extremity of right femur viewed from behind and above.
the female, in consequence of the increased width of the pelvis, the neck of the
femur forms more nearly a right angle with the body than it does in the male.
The angle decreases during the period of growth, but after full growth has been
attained it does not usually undergo any change, even in old age; it varies con-
siderably in different persons of the same age. It is smaller in short than in long
bones, and when the pelvis is wide. In addition to projecting upward and medial-
ward from the body of the femur, the neck also projects somewhat forward ; the
amount of this forw^ard projection is extremely variable, but on an average is from
12° to 14°.
The neck is flattened from before backward, contracted in the middle, and
broader laterally than medially. The vertical diameter of the lateral half is in-
creased by the obliquity of the lower edge, which slopes downward to join the
body at the level of the lesser trochanter, so that it measures one-third more
than the antero-posterior diameter. The medial half is smaller and of a more
circular shape. The anterior sm-face of the neck is perforated by numerous vascular
foramina. Along the upper part of the line of junction of the anterior surface
with the head is a shallow groove, best marked in elderly subjects; this
244
OSTEOLOGY
Obturator internus
and Gemelli
Piriformis
Tubercle
Articular capsule
Artictdar capsule
Adductor
tubercle
Medial
ejncondylc
""^ Con<ll}^
"'^^l/Je
Fig. 244. — Right femur. Anterior surface.
groove lodges the orbicular fibers
of the capsule of the hip-joint.
The posterior surface is smooth, and
is broader and more concave than
the anterior: the posterior part of
the capsule of the hip-joint is
attached to it about 1 cm. above
the intertrochanteric crest. The
superior border is short and thick,
and ends laterally at the greater
trochanter; its surface is perforated
by large foramina. The inferior
border, long and narrow, curves a
little backward, to end at the lesser
trochanter.
The Trochanters. — The trochan-
ters are prominent processes which
afford leverage to the muscles that
rotate the thigh on its axis. They
are two in number, the greater and
the lesser.
The Greater Trochanter {trochanter
major; great trochanter) is a large,
irregular, quadrilateral eminence,
situated at the junction of the neck
with the upper part of the body. It
is directed a little lateralward and
backward, and, in the adult, is about
1 cm. lower than the head. It has
two surfaces and four borders. The
lateral surface, quadrilateral in form,
is broad, rough, convex, and marked
by a diagonal impression, which
extends from the postero-superior
to the antero-inferior angle, and
serves for the insertion of the ten-
don of the Cilutteus medius. Above
the impression is a triangular sur-
face, sometimes rough for part of
the tendon of the same muscle,
sometimes smooth for the inter-
position of a bursa between the
tendon and the bone. Below and
behind the diagonal impression is
a smooth, triangular surface, over
which the tendon of the Gluteus
maximus plays, a bursa being inter-
posed. The medial surface, of much
less extent than the lateral, pre-
sents at its base a deep depression,
the trochanteric fossa {digital fossa) ,
for the insertion of the tendon of
the Obturator externus, and above
and in front of this an impression
for the insertion of the Obtura-
THE FEMUR
245
tor internus and Gemelli. The
superior border is free ; it is thick
and irregular, and marked near
the center by an impression for
the insertion of the Piriformis.
The inferior border corresponds
to the Hne of junction of the
base of the trochanter with the
lateral surface of the body; it is
marked by a rough, prominent,
slightly curved ridge, which gives
origin to the upper part of the
Vastus lateralis. The anterior
border is prominent and some-
what irregular; it afl'ords inser-
tion at its lateral part to the
Glutieus minimus. The posterior
border is very prominent and
appears as a free, rounded edge,
which bounds the back part of
the trochanteric fossa.
The Lesser Trochanter (tro-
chanter minor; small trochanter)
is a conical eminence, which
varies in size in different sub-
jects; it projects from the lower
and back part of the base of the
neck. From its apex three well-
marked borders extend; two of
these are above — a medial con-
tinuous with the lower border
of the neck, a lateral with the
intertrochanteric crest; the in-
ferior border is continuous with
the middle division of the linea
aspera. The summit of the tro-
chanter is rough, and gives in-
sertion to the tendon of the
Psoas major.
A prominence, of variable size,
occurs at the junction of the
upper part of the neck with the
greater trochanter, and is called
the tubercle of the femur; it is
the point of meeting of five
muscles: the Glut^-us minimus
laterally, the Vastus lateralis
below, and the tendon of the
Obturator internus and two
Gemelli above. Running ob-
liquely downward and medial-
ward from the tubercle is the
intertrochanteric line {spiral line
of the femur); it winds around
the medial side of the body of
the bone, below the lesser tro-
Articular
capsule
Lateral
epicoiidyle
Groove for
tendon of
Popliteus
TTrt^
Fig. 245.
Articular
capsule
-Right femur.
Posterior surface.
246 OSTEOLOGY
chanter, and ends about 5 cm. below this eminence in the linea aspera. Its upper
half is rough, and affords attachment to the iliofemoral ligament of the hip-joint;
its lower half is less prominent, and gives origin to the upper part of the Vastus
medialis. Running obliquely downward and medialward from the summit of the
greater trochanter on the posterior surface of the neck is a prominent ridge, the
intertrochanteric crest. Its upper half forms the posterior border of the greater tro-
chanter, and its lower half runs downward and medialward to the lesser trochanter.
A slight ridge is sometimes seen commencing about the middle of the intertrochan-
teric crest, and reaching vertically downward for about 5 cm. along the back part
of the body: it is called the linea quadrata, and gives attachment to the Quad-
ratus femoris and a few fibers of the Adductor magnus. Generally there is merely
a slight thickening about the middle of the intertrochanteric crest, marking the
attachment of the upper part of the Quadratus femoris.
The Body or Shaft (cor pm femoris). — The body, almost cylindrical in form, is
a little broader above than in the center, broadest and somewhat flattened from
before backward below. It is slightly arched, so as to be convex in front, and con-
cave behind, where it is strengthened by a prominent longitudinal ridge, the linea
aspera. It presents for examination three borders, separating three surfaces. Of
the borders, one, the linea aspera, is posterior, one is medial, and the other, lateral.
The linea aspera (Fig. 245) is a prominent longitudinal ridge or crest, on the
middle third of the bone, presenting a medial and a lateral lip, and a narrow
rough, intermediate line. Above, the linea aspera is prolonged by three ridges.
The lateral ridge is very rough, and runs almost vertically upward to the base of
the greater trochanter. It is termed the gluteal tuberosity, and gives attachment
to part of the Gluteus maximus : its upper part is often elongated into a roughened
crest, on which a more or less well-marked, rounded tubercle, the third trochanter,
is occasionally developed. The intermediate ridge or pectineal line is continued
to the base of the lesser trochanter and gives attachment to the Pectineus; the
medial ridge is lost in the intertrochanteric line; between these two a portion of the
Iliacus is inserted. Below, the linea aspera is prolonged into two ridges, enclosing
between them a triangular area, the popliteal surface, upon which the popliteal
artery rests. Of these two ridges, the lateral is the more prominent, and descends
to the summit of the lateral condyle. The medial is less marked, especially at its
upper part, where it is crossed by the femoral artery. It ends below at the summit
of the medial condyle, in a small tubercle, the adductor tubercle, which affords
insertion to the tendon of the Adductor magnus.
From the medial lip of the linea aspera and its prolongations above and below,
the Vastus medialis arises; and from the lateral lip and its upward prolongation,
the Vastus lateralis takes origin. The Adductor magnus is inserted into the linea
aspera, and to its lateral prolongation above, and its medial prolongation below.
Between the Vastus lateralis and the Adductor magnus two muscles are attached
— viz., the Glutams maximus inserted above, and the short head of the Biceps
femoris arising below. Betweeen the Adductor magnus and the Vastus medialis
four muscles are inserted: the Iliacus and Pectineus above; the Adductor brevis
and Adductor longus below. The linea aspera is perforated a little below its center
by the nutrient canal, which is directed obliquely upward.
The other two borders of the femur are only slightly marked: the lateral border
extends from the antero-inferior angle of the greater trochanter to the anterior
extremity of the lateral condyle; the medial border from the intertrochanteric line,
at a point opposite the lesser trochanter, to the anterior extremity of the medial
condyle.
The anterior surface includes that portion of the shaft which is situated between
the lateral and medial borders. It is smooth, convex, broader above and below
than in the center. From the upper three-fourths of this surface the ^^astus inter-
medius arises; the lower fourth is separated from the muscle by the intervention
THE FEMUR
247
of the synovial membrane of the knee-joint and a bursa; from the upper part of it
the ArticuL^ris genu takes origin. The lateral surface includes the portion between
the lateral border and the linea aspera; it is continuous above with the correspond-
ing surface of the greater trochanter, below with that of the lateral condyle: from
its upper three-fourths the Vastus intermedins takes origin. The medial surface
includes the portion between the medial border and the linea aspera; it is continu-
ous above with the lower border of the neck, below with the medial side- of the
medial condyle: it is covered by the Vastus medialis.
The Lower Extremity {distal extremity), (Fig. 246).— The lower extremity, larger
than the upper, is somewhat cuboid in form, but its transverse diameter is greater
than its antero-posterior; it consists of two oblong eminences known as the condyles.
In front, the condyles are but slightly prominent, and are separated from one another
by a smooth shallow articular depression called the patellar surface; behind, they
project considerably, and the interval between them forms a deep notch, the
intercondyloid fossa. The lateral condyle is the more prominent and is the broader
both in its antero-posterior and transverse diameters, the medial condyle is the
longer and, when the femur is held with its body perpendicular, projects to a lower
Lateral groove — «f
i
Lateral epicondyle-*^^
Medial groove
Medial epicondyle
Semilunar area
I
Fig. 246. — Lower extremity of right femur viewed from below.
level. When, however, the femur is in its natural oblique position the lower sur-
faces of the two condyles lie practically in the same horizontal plane. The condyles
are not quite parallel with one another; the long axis of the lateral is almost
directly antero-posterior, but that of the medial runs backward and medialward.
Their opposed surfaces are small, rough, and concave, and form the walls of the
intercondyloid fossa. This fossa is limited above by a ridge, the intercondyloid
line, and below by the central part of the posterior margin of the patellar surface.
The posterior cruciate ligament of the knee-joint is attached to the lower and front
part of the medial wall of the fossa and the anterior cruciate ligament to an impres-
sion on the upper and back part of its lateral wall. Each condyle is surmounted
by an elevation, the epicondyle. The medial epicondyle is a large convex eminence
to which the tibial collateral ligament of the knee-joint is attached. At its upper
part is the adductor tubercle, already referred to, and behind it is a rough impres-
sion which gives origin to the medial head of the Gastrocnemius. The lateral
epicondyle, smaller and less prominent than the medial, gives attachment to the
fibular collateral ligament of the knee-joint. Directly below it is a small depression
from which a smooth well-marked groove curves obliquely upward and backward
to the posterior extremity of the condyle. This groove is separated from the
articular surface of the condyle by a prominent lip across which a second, shallower
groove runs \'ertically downward from the depression. In the fresh state these
grooves are covered with cartilage. The Popliteus arises from the depression;
its tendon lies in the oblique groove when the knee is flexed and in the vertical
248 OSTEOLOGY
groove when the knee is extended. Above and behind the lateral epicondyle is
an area for the origin of the lateral head of the Gastrocnemius, above and to the
medial side of which the Plantaris arises.
The articular surface of the lower end of the femur occupies the anterior, inferior,
and posterior surfaces of the condyles. Its front part is named the patellar surface
and articulates with the patella; it presents a median groove which extends down-
ward to the intercondyloid fossa and two convexities, the lateral of which is broader,
more prominent, and extends farther upward than the medial. The lower and
posterior parts of the articular surface constitute the tibial surfaces for articulation
with the corresponding condyles of the tibia and menisci. These surfaces are
separated from one another by the intercondyloid fossa and from the patellar
surface by faint grooves which extend obliquely across the condyles. The lateral
groove is the better marked; it runs lateralward and forward from the front part
of the intercondyloid fossa, and expands to form a triangular depression. When
the knee-joint is fully extended, the triangular depression rests upon the anterior
portion of the lateral meniscus, and the medial part of the groove comes into con-
tact with the medial margin of the lateral articular surface of the tibia in front
of the lateral tubercle of the tibial intercondyloid eminence. The medial groove
is less distinct than the lateral. It does not reach as far as the intercondyloid
fossa and therefore exists only on the medial part of the condyle; it receives the
anterior edge of the medial meniscus when the knee-joint is extended. Where the
groove ceases laterally the patellar surface is seen to be continued backward as
a semilunar area close to the anterior part of the intercondyloid fossa; this semi-
lunar area articulates with the medial vertical facet of the patella in forced flexion
of the knee-joint. The tibial surfaces of the condyles are convex from side to side
and from before backward. Each presents a double curve, its posterior segment
being an arc of a circle, its anterior, part of a cycloid.^
The Architecture of the Femur. — Koch^ ]\v mathematical analysis has "shown that in every
part of the femur there is a remarkable adaptation of the inner structure of the bone to the machan-
ical requirements due to the load on the femur-head. The various parts of the femur taken
together form a single mechanical structure wonderfully well-adapted for the efficient, economical
transmission of the loads from the acetabulum to the tibia; a structure in which every element
contributes its modicum of strength in the manner required by theoretical mechanics for maximum
efficiency." "The internal structure is everywhere so formed as to provide in an efficient manner
for all the internal stresses which occur due to the load on the femur-head. Throughout the femur,
with the load on the femur-head, the bony material is arranged in the paths of the maximum
internal stresses, which are thereby resisted with the greatest efficiency, and hence with maximum
economy of material." "The conclusion is inevitable that the inner structure and outer form of
the femur are governed by the conditions of maximum stress to which the bone is subjected
normally by the preponderant load on the femur-head; that is, by the body weight transmitted
to the femur-head through the acetabulum." "The femur obeys the mechanical laws that govern
other elastic bodies under stress; the relation between the computed internal stresses due to the
load on the femur-head, and the internal structure of the different portions of the femur is in very
close agreement with the theoretical relations that should exist between stress and structure for
maximum economy and efficiency; and, therefore, it is believed that the following laws of bone
structure have been demonstrated for the femur:
"1. The inner structure and external form of human bone are closely adapted to the mechanical
conditions existing at every point in the bone.
"2. The inner architecture of normal bone is determined by definite and exact requirements of
mathematical and mechanical laws to produce a maximum of strength with a minimum of
material."
The Inner Architecture of the Upper Femur.— "The spongy l)one of the upper femur (to the
lower limit of the lesser trochanter) is composed of two distinct systems of trabecule arranged in
curved paths: one, which has its origin in the medial (inner) side of the shaft and curving upward
' A cycloid is a curve traced bj' a point in the circumference of a wheel when tlie wlieel is rolled along in a straight
line.
2 The Laws of Bone Architecture. Am. Jour, of .\nat., 21, 1917. The following paragraphs are taken almost ver-
batum from Koch's article in which we have the first correct mathematical analysis of the femur in support of the
theory of the functional form of bone proposed by Wolff and also by Roux.
THE FEMUR
249
in a fan-like radiation to the oppoaite side of the bone; the other, having origin in the later d
(outer) portion of the shaft and arching upward and medially to end in th! upper surface of the
^"TMT^:ur' ""' '" '.'^'^ ^)Z 'r ^^^^^"^ -^--^^ -^h other a7St angles '
; f !1 f f «^?^^^f«"t^ System of Trabeculce.~As the compact bone of fhe medial (inner)
part of the shaft nears the head of the femur it gradually becomes thinner and finally reaches the
articular surface of the head as a very thin layer. From a point at about the lower level of he
Fig. 217. — Frontal longitudinal midsection of upptr femur.
lesser trochanter, 2^ to 3 inches from the lower limit of the articular surface of the head, the
trabeculae branch off from the shaft in smooth curves, spreading radially to cross to the opposite
side in two well-defined groups: a lower, or secondary group, and an upper, or principal group.
"a. The Secondary Compressive Group. — This group of trabecular leaves the inner border of the
shaft beginning at about the level of the lesser trochanter, and for a distance of almost 2 inches
along the curving shaft, with which the separate trabeculae make an angle of about 15 degrees.
250
OSTEOLOGY
They curve outwardly and upwardly to cross in radiating smooth curves to the opposite side.
The lower filaments end in the region of the greater trochanter: the adjacent filaments above
these pursue a more nearly vertical course and end in the upper portion of the neck of the femur.
The trabecula; of this group are thin and with wide spaces between them. As they traverse
the space between the medial and lateral surfaces of the bone they cross at right angles the system
of curved trabeculae which arise from the lateral (outer) portion of the shaft. (Figs. 247 and 249.)
"b. The Principal Compressive Group. — This group of trabeculse (Figs. 247 and 249) springs
from the medial portion of the shaft just above the group above-described, and spreads upward
and in slightly radial smooth curved lines to reach the upper portion of the articular surface of
the head of the femur. These trabecule are placed very closely together and are the thickest ones
seen in the upper femur. They are a prolongation of the shaft from which they spring in straight
LOAD
Fig. 248. — Diagram of the lines of stress in the upper femur, based upon the mathematical analysis of the right
femur. These result from the combination of the different kinds of stresses at each point in the femur. (After
Koch )
lines which gradually curve to meet at right-angles the articular surface. There is no change as
they cross the epiphyseal line. They also intersect at right-angles the system of lines which rise
from the lateral side of the femur.
"This system of principal and secondary compressive trabeculse corresponds in position and in
curvature with the lines of maximum compressive stress, which were traced out in the mathematical
analysis of this portion of the femur. (Figs. 247 and 250.)
"B. Lateral (Tensile) System of Traheculce. — As the compact bone of the outer portion of the
shaft approaches the greater trochanter it gradually decreases in thickness. Beginning at a point
about 1 inch below the level of the lower border of the greater trochanter, nimierous thin trabeculse
are given off from the outer portion of the shaft. These trabeculse lie in three distinct groups. ,
"c. The Greater Trochanter Group. — These trabeculai rise from the outer part of the shaft just
below the greater trochanter and rise in thin, curving lines to cross the region of the greater
trochanter and end in its upper surface. Some of these filaments are poorly defined. This group
THE FEMUR
251
Fig. 249. — Frontal longitudinal midsection of left
femur. Taken from the same subject as the one that
was analyzed and shown in Figs. 248 and 250. i of
natural size, (.\fter Koch.)
Fig. 250. — Diagram of the computed lines of
maximum stress in the normal femur. The section
numbers 2, 4, 6 , 8, etc., show the positions of the
transverse sections analyzed. The amounts of the
maximum tensile and compressive stress at the
various sections are given for a load of 100 pounds on
the femur-head. For the standing position ("at at-
tention") these stresses are multiplied by 0.6, for
walking by 1.6 and for running by 3.2. (After Koch.)
252
OSTEOLOGY
intersects the trabeculiB of group (a) which rise from the opposite side. The trabeculse of this
group evidenth' carry small stresses, as is shown by their slenderness.
"d. The Principal Tensile Group. — This group springs from the outer part of the shaft imme-
diately below group c, and curves convexly upward and inward in nearly parallel lines across the
neck of the femur and ends in the inferior portion of the head. These trabecuiae are somewhat
thinner and more widely spaced than those of the principal compressive group (b). All the trabec-
ula? of this group cross those of groups (a) and (b) at right angles. This group is the most impor-
tant of the lateral system (tensile) and, as will be sho^NTi later, the greatest tensile stresses of the
upper femur are carried bj^ the trabecuiae of this group.
"e. The Secondary Tensile Group. — This group consists of the trabecular which spring from the
outer side of the shaft and lie below those of the preceding group. They curve upward and medially
across the axis of the femur and end more or less irregularly after crossing the midline, but a
nimiber of these filaments end in the medial portion of the shaft and neck. They cross at right
angles the trabecuiae of group (o).
Fig. 251.
O = C0MPRESSI0N
• = TENS10N
C=COMP. & TENSION
NEUTRAL AXTS
-Intensity of the maximum tensile and compressive stresses in the upper femur. Computed for the load of
100 pounds on the right femur. Corresponds to the upper part of Fig. 250. (After Koch.)
"In general, the trabecula? of the tensile system are lighter in structure than those of the com-
pressive system in corresponding positions. The significance of the difference in thickness of these
two systems is that the thickness of the trabecuiae varies with the intensity of the stresses at any
given point. Comparison of Fig. 247 with Fig. 251 will show that the trabecular of the com-
pressive system carry heavier stresses than those of the tensile sj'stem in corresponding positions.
For example, the maximum tensile stress at section 8 (Fig. 251) in the outermost fiber is 771
pounds per square inch, and at the corresponding point on the compressive side the compressive
stress is 954 pounds per square inch. Similar comparisons may be made at other points, which
confirm the conclusion that the thickness and closeness of spacing of the trabecuiae varies in
proportion to the intensity of the stresses carried by them.
"It will be seen that the trabecuiae lie exactly in the paths of the maximum tensile and com-
pressive stresses (compare Figs. 247, 248 and 251), and hence these trabecula? carry these stresses
in the most economical manner. This is in accordance with the well-recognized principle of
mechanics that the most direct manner of transmitting stress is in the direction in which the stress
acts.
THE FEMUR 253
"Fig. 249 shows a longitudinal frontal section through the left femur, which is the mate of the
right femur on which the mathematical analysis was made. In this midsection the sy.stom of
tensile trabecule, which rises from the lateral (outer) part of the shaft and crosses over the central
area to end in the medial portion of the shaft, neck and head, is clearly shown. This figun* also
shows the compressive system of trabecular which rises on the medial portion of the shaft and
crosses the central area to end in the head, neck and greater trochanter. By comparing th(; posi-
tion of these two systems of trabecule shown in Fig. 249 with the lines of maximum and minimum
stresses shown in Figs. 248 and 250 it is seen that the tensile system of trabecuUe corresjwnds
exactly with the position of the lines of maximum and minimum tensile stresses which were
determined by mathematical analysis. In a similar manner, the compressive system of trabecuhe
in Fig. 249 corresponds exactly with the lines of maximum and minimum compressive stresses
computed by mathematical analysis.
"The amount of vertical shear varies almost uniformly from a maximum of 90 pounds (90 per
cent, of the load on the femur-head) midway between sections 4 and 6, to a minimum of — 5.7
pounds at section 18" (Fig. 251). There is a gradual diminution of the spongy bone from section
6 to section 18 parallel with the diminished intensities of the vertical shear.
1. The trabecuke of the upper femur, as shown in frontal sections, are arranged in two general
systems, compressive and tensile, which correspond in position with the lines of maximum and
minimum stres.ses in the femur determined by the mathematical analysis of the femur as a mechan-
ical structiu-e.
2. The thickness and spacing of the trabeculse vary with the intensity of the maximum stresses
at various points in the upjier femur, being thickest and most closely spaced in the regions where
the greatest stresses occur.
3. The amount of bony material in the spongy bone of the upper femur varies in proportion to
the intensity of the shearing force at the various sections.
4. The arrangement of the trabeculse in the positions of maximum stresses is such that the
greatest strength is secured with a minimum of material.
Significance of the Inner Architecture of the Shaft. — 1. Economy for resisting shear. The shearing
stresses are at a minimum in the shaft. "It is clear that a minimum amount of material will be
required to resist the shearing stresses." As horizontal and vertical shearing stresses are most
efficiently resisted by material placed near the neutral plane, in this region a minimum amount
of material wiU be needed near the neutral axis. In the shaft there is very little if any material
in the central space, practically the only material near the neutral plane being in the compact
bone, but lying at a distance from the neutral axis. This conforms to the requirement of mechanics
for economy, as a minimum of material is provided for resisting shearing stresses where these
stresses are a minimum.
2. Economy for resisting bending moment. "The bending moment increases from a minimum
at section 4 to a maximum between sections 16 and 18, then gradually decreases almost uniformly
to 0 near section 75." "To resist bending moment stresses most effectively the material should
be as far from the neutral axis as possible." It is evident that the hollow shaft of the femur is
an efficient structure for resisting bending moment stresses, all of the material in the shaft being
relatively at a considerable distance from the neutral axis. It is evident that the hollow shaft
provides efficiently for resisting bending moment not only due to the load on the femur-head, but
from any other loads tending to produce bending in other planes.
3. Economy for resisting axial stress.
The inner architecture of the shaft is adapted to resist in the most efficient manner the com-
bined action of the minimal shearing forces and the axial and maximum bending stresses.
The structure of the shaft is such as to secure great strength with a relatively small amount of
material.
The Distal Portion of the Femur. — In frontal section (Fig. 249) in the distal 6 inches of the
femur "there are to be seen two main systems of trabecular, a longitudinal and a transverse
system. The trabeculip of the former ri.se from the inner wall of the shaft and continue in per-
fectly straight lines parallel to the axis of the shaft and proceed to the epiphyseal line, whence
they continue in more or less curved lines to meet the articular surface of the knee-joint at right
angles at every point. Near the center there are a few thin, delicate, longitudinal trabeculse
which spring from the longitudinal trabeculse just described, to which they are joined by fine
transverse filaments that lie in planes parallel to the sagittal plane.
"The trabeculse of the transverse system are somewhat lighter in structure than those of the
longitudinal .system, and consist of numerous trabeculie at right angles to the latter.
"As the distal end of the femur is approached the shaft gradually becomes thinner until the
articular surface is reached, where there remains only a thin shell of compact bone. With the
gradual thinning of the compact bone of the shaft, there is a simultaneous increase in the amount
of the spongy bone, and a gradual flaring of the femur which gives this portion of the bone a
gradually increasing gross area of cross-section.
"There is a marked thickening of the shell of bone in the region of the intercondyloid fo.ssa
where the anterior and posterior crucial ligaments are attached. This thickened area is about
254
OSTEOLOGY
Appears at
ith year ;
joins body
about 18th yr. ^
Appears at
9th month of
fetal life
Appears at
end of 1st yr. ;
joins body
about l%th yr.
Appears IWi-l^th
year ; joins body
about 18th year
Joins body at
20th year
Lower extremity
Fig. 252. — Plan of ossification of the femur,
five centers.
From
0.4 inch in diameter and consists of compact
bone from which a nimiber of thick trabeculse
pass at right angles to the main longitudinal
system. The inner structm-e of the bone is here
e\'idently adajited to the efficient distribution of
the stresses arising from this ligamentary at-
tachment.
"Near the distal end of the femur the longi-
tudinal trabecular gradually assume curved
paths and end perpendicularly to the articular
surface at every point. Such a structure is in
accordance with the principles of mechanics,
as stresses can be communicated through a
frictionless joint only in a direction perpendic-
ular to the joint surface at every point.
"With practically no increase in the amount
of bony material used, there is a greatly increased
stability produced by the expansion of the lower
femur from a hollow shaft of compact bone to a
structure of much larger cross-section almost
entirely composed of spongy bone.
"Significance of the Inner Architecture of the
Distal Port of the Femur. — The function of the
lower end of the femur is to transmit through a
hinged joint the loads carried by the femur. For
stability the width of the bearing on which the
hinge action occurs should be relatively large.
For economy of material the expansion of the end
bearing should be as lightly constructed as is
consistent with proper strength. In accordance
with the ])rinciples of mechanics ,
Fig. 253. — Epiphysial lines of femur in a young
adult. Anterior aspect. The lines of attachment of
the articular capsules are in blue.
Fig. 254. — Epiphysial lines of femur in a young adult.
Posterior aspect. The lines of attachment of the articular
capsules are in blue.
THE PATELLA
255
A
the most efficient manner in which stresses are transmitted is by the arrangement of the resist-
mg material m Imes parallel to the direction in which the stresses occur and in the paths taken
by the stresses. Theoretically the most efficient manner to attain these objects would be to pro-
long the innermost filaments of the bone as straight lines parallel to the longitudinal axis of
the bone, and gradually to flare the outer shell of compact bone outward, and continuing to give
off filaments of bone parallel to the longitucUnal axis as the distal end of the femur is approached
These filaments shoiUd be well-braced transversely and each should carry its proportionate
part of the total load, parallel to the longitudinal axis, transmitting it eventually to the
articular surface, and in a direction perpendicular to that surface."
Referring to I^g. 249, it is seen that the large expansion of the bone is produced by the gradual
transition of the hollow shaft of compact bone to cancellated bone, resulting in the production
• of a much larger volume. The trabecule are given off from the shaft in lines parallel to the
longitudinal axis, and are braced transversely by two series of trabecule at right angles to
each other, in the same manner as required theoretically for economy.
Although the action of the muscles exerts an appreciable effect on the stresses in the femur,
it is relatively small and very complex to analyze and has not been considered in the aliove analysis!
Ossification (Figs. 252, 253, 254).— The femur is ossified from five centers: one for the bodyj
one for the head, one for each trochanter, and one for the lower extremity. Of all the long bones,'
except the clavicle, it is the first to show traces of ossification ; this commences in the middle of
the body, at about the seventh week of fetal life, and rapidly extends upward and downward.
The centers in the epiphyses appear in the following order: in the lower end of the bone, at the
ninth month of fetal Hfe (from this center the condyles and epicondyles are formed) ; in the head,
at the end of the first year after birth; in the greater trochanter, during the fourth year; and
in the lesser trochanter, between the thirteenth and fourteenth years. The order in which the
epiphyses are joined to the body is the reverse of that of their appearance; they are not united
until after puberty, the lesser trochanter being first joined, then the greater, then the head, and,
lastly, the inferior extremity, which is not united until the twentieth year.
Fig. 255. — Right patella.
Anterior surface.
Fig. 256.^Right patella.
Posterior surface.
The Patella (Knee Cap).
The patella (Figs. 255, 256) is a flat, triangular bone, situated on the front of
the knee-joint. It is usually regarded as a sesamoid bone, developed in the
tendon of the Quadriceps femoris,
and resembles these bones (1) in
being developed in a tendon ; (2) in
its center of ossification presenting
a knotty or tuberculated outline;
(3) in being composed mainly of
dense cancellous tissue. It serves
to protect the front of the joint,
and increases the leverage of the
Quadriceps femoris by making it
act at a greater angle. It has an
anterior and a posterior surface
three borders, and an apex.
Surfaces. — The anterior stirface is convex, perforated by small apertures for the
passage of nutrient vessels, and marked by numerous rough, longitudinal stride.
This surface is covered, in the recent state, by an expansion from the tendon of
the Quadriceps femoris, which is continuous below with the superficial fibers of
the ligamentum patella\ It is separated from the integument by a bursa. The
posterior surface presents above a smooth, oval, articular area, di\ided into two
facets by a vertical ridge; the ridge corresponds to the groove on the patellar
surface of the femur, and the facets to the medial and lateral parts of the same
surface; the lateral facet is the broader and deeper. Below the articular surface
is a rough, convex, non-articular area, the lower half of which gives attachment
to the ligamentum patellae; the upper half is separated from the head of the tibia
by adipose tissue.
Borders. — The base or superior border is thick, and sloped from behind, down-
ward, and forward: it gives attachment to that portion of the Quadriceps femoris
256
OSTEOLOGY
which is derived from the Rectus femoris and Vastus intermedius. The medial and
lateral borders are thinner and converge below: they give attachment to those
portions of the Quadriceps femoris which are derived from the Vasti lateralis and
medialis.
Apex. — The apex is pointed, and gives attachment to the ligamentum patelhe.
Structure. — The patella consists of a nearly uniform dense cancellous tissue, covered by a
thin compact lamina. The canceUi immediately beneath the anterior surface are arranged
parallel with it. In the rest of the bone they radiate from the articular surface toward the other
parts of the bone.
Ossification. — The patella is ossified from a single center, which usually makes its appearance
in the second or third year, but may be delayed until the sixth year. More rarely, the bone is
developed by two centers, placed side by side. Ossification is completed about the age of puberty.
Articulation. — The patella articulates with the femur.
Inter condyloid eminence
Fig. 257. — Upper surface of right tibia.
The Tibia (Shin Bone).
The tibia (Figs. 25S, 259) is situated at the medial side of the leg, and,
excepting the femur, is the longest bone of the skeleton. It is prismoid in form,
expanded above, where it enters into the
Tuberosity knee-joint, contracted in the lower third,
and again enlarged but to a lesser extent
below. In the male, its direction is vertical,
and parallel with the bone of the opposite
side; but in the female it has a slightly
oblique direction downward and lateralward,
to compensate for the greater ol)liquity of
the femur. It has a body and two extremities.
The Upper Extremity {proximal extremity).
— The upper extremity is large, and expanded
into two eminences, the medial and lateral
condyles. The superior articular surface pre-
sents two smooth articular facets (Fig. 257).
The medial facet, oval in shape, is slightly
concave from side to side, and from before
backward. The lateral, nearly circular, is
concave from side to side, but slightly convex from before backward, especially
at its posterior part, where it is prolonged on to the posterior surface for a
short distance. The central portions of these facets articulate with the con-
dyles of the femur, while their peripheral portions support the menisci of the
knee-joint, which here intervene between the two bones. Between the artic-
ular facets, but nearer the posterior than the anterior aspect of the l)one, is the
intercondyloid eminence {spine of tibia), surmounted on either side by a prominent
tubercle, on to the sides of which the articular facets are prolonged; in front of
and behind the intercondyloid eminence are rough depressions for the attachment
of the anterior and posterior cruciate ligaments and the menisci. The anterior
surfaces of the condyles are continuous with one another, forming a large somewhat
flattened area; this area is triangular, broad above, and perforated by large vascular
foramina; narrow below where it ends in a large oblong elevation, the tuberosity of
the tibia, which gives attachment to the ligamentum patellte; a bursa intervenes
between the deep surface of the ligament and the part of the bone immediately
above the tuberosity. Posteriorly, the condyles are separated from each other by
a shallow depression, the posterior intercondyloid fossa, which gives attachment to
part of the posterior cruciate ligament of the knee-joint. The medial condyle
presents posteriorly a deep transverse groove, for the insertion of the tendon of
THE TIBIA
257
the Semimembranosus. Its medial
surface IS convex, rough, and promi-
nent; it gives attachment to the
tibial collateral ligament. The lat-
eral condyle presents posteriorly a
flat articular facet, nearly circular
in form, directed downward, back-
ward, and lateralward, for articu-
lation with the head of the fibula.
Its lateral surface is convex, rough,
and prominent in front: on it is
an eminence, situated on a level
with the upper border of the tuber-
osity and at the junction of its
anterior and lateral surfaces, for
the attachment of the iliotibial
band. Just below this a part of
the Extensor digitorum longus
takes origin and a slip from the
tendon of the Biceps femoris is
inserted.
The Body or Shaft {corjms tibia') .
— The body has three borders and
three surfaces.
Borders. — The anterior crest or
border, the most prominent of the
three, commences above at the
tuberosity, and ends below at the
anterior margin of the medial
malleolus. It is sinuous and
prominent in the upper two-thirds
of its extent, but smooth and
rounded below; it gives attach-
ment to the deep fascia of the leg.
The medial border is smooth and
rounded above and below, but
more prominent in the center; it
begins at the back part of the
medial condyle, and ends at the
posterior border of the medial
malleolus; its uj^per part gives
attachment to the tibial collat-
eral ligament of the knee-joint
to the extent of about 5 cm.,
and insertion to some fibers of
the Popliteus; from its middle
third some fibers of the Soleus
and Flexor digitorum longus take
origin.
The interosseous crest or lateral
border is thin and prominent, espe-
cially its central part, and gives at-
tachment to the interosseous mem-
brane; it commences above in front
of the fibular articular facet, and
17
Articular capsule
.Vr^o'^-f/r,,
-'"'Lr.
■> (Ti/le
J^eat
Styloid process "
Fibular
collateral'
ligament
^^
01'
i;,H:l""«»^tf^
i"iMv.:'»i/,„.
J eVoji
/
*V^
^^^.
.igamemt/
Ipatell
FIBULA liC ]
0
'II
Articular
capsule
Medial ■malleolus
Lateral malleolus
Fia. 258. — Bones of the right leg. Anterior surface.
258
OSTEOLOGY
Articular
cap;
Articular
capsule
Styloid
process
FIBULA
bifurcates below, to form the boundaries of a triangular rough surface, for the
attachment of the interosseous ligament connecting the tibia and fibula.
Surfaces. — The medial surface
is smooth, convex, and broader
above than below; its upper
third, directed forward and
medialward, is covered by the
aponeurosis derived from the
tendon of the Sartorius, and by
the tendons of the Gracilis and
Semitendinosus, all of which
are inserted nearly as far for-
ward as the anterior crest; in
the rest of its extent it is sub-
cutaneous.
The lateral surface is narrower
than the medial ; its upper two-
thirds present a shallow groove
for the origin of the Tibialis
anterior; its lower third is
smooth, convex, curves grad-
ually forward to the anterior
aspect of the bone, and is
covered by the tendons of the
Tibialis anterior. Extensor hal-
lucis longus, and Extensor digi-
torum longus, arranged in this
order from the medial side.
The posterior surface (Fig. 259)
presents, at its upper part, a
prominent ridge, the popliteal
line, which extends obliquely
downward from the back part of
the articular facet for the fibula
to the medial border, at the
junction of its upper and middle
thirds; it marks the lower limit
of the insertion of the Popliteus,
serves for the attachment of the
fascia covering this muscle, and
gives origin *to part of the
Soleus, Flexor digitorum longus,
and Tibialis posterior. The
triangular area, above this line,
gives insertion to the Popliteus.
The middle third of the poste-
rior surface is divided by a ver-
tical ridge into two parts; the
ridge begins at the popliteal line
and is well-marked above, but
indistinct below; the medial and
broader portion gives origin to
the Flexor digitorum longus,
the lateral and narrower to part
of the Tibialis posterior. The
Articulates with talu^
Fia.
Articula\r capsule
259. — Bones of the right leg. Posterior surface.
THE TIBIA
259
remaining part of the posterior surface is smooth and covered by the Tibialis
posterior, Flexor digitorum longus, and Flexor hallucis longus. Immediately below
the popliteal line is the nutrient foramen, which is large and directed oblicjuely
downward.
The Lower Extremity {distal extremity) .—The lower extremity, much smaller
than the upper, presents five surfaces; it is prolonged downward on its medial
side as a strong process, the medial malleolus.
Surfaces. — The inferior articular surface is quadrilateral, and smooth for articu-
lation with the talus. It is concave from before backward, broader in front than
behind, and traversed from before backward by a slight elevation, separating
two depressions. It is continuous with that on the medial malleolus.
Upper extremily
Appears before or
shortly after birth
Appears at 2nd ,
year
Joins body
about 20th year
Joins body about
\9.th year
Lower extremity
FlG. 260. — Plan of ossification of the tibia,
centers.
From three
Fig.
261. — Epiphysial lines of tibia and fibula
in a young adult. Anterior aspect.
The anterior surface of the lower extremity is smooth and rounded above, and
covered by the tendons of the Extensor muscles ; its lower margin presents a rough
transverse depression for the attachment of the articular capsule of the ankle-
joint.
The posterior surface is traversed by a shallow groove directed obliquely down-
ward and medialward, continuous with a similar groove on the posterior surface
of the talus and serving for the passage of the tendon of the Flexor hallucis longus.
The lateral surface presents a triangular rough depression for the attachment
of the inferior interosseous ligament connecting it with the fibula; the loMcr part
of this depression is smooth, covered with cartilage in the fresh state, and articu-
lates with the fibula. The surface is bounded by two prominent borders, con-
tinuous above with the interosseous crest; they afford attachment to the anterior
and posterior ligaments of the lateral malleolus.
The medial surface is prolonged downward to form a strong pyramidal process,
flattened from without inward — the medial malleolus. The medial surface of this
process is convex and subcutaneous; its lateral or articular surface is smooth and
slightly concave, and articulates with the talus; its anterior border is rough, for
260 OSTEOLOGY
the attachment of the anterior fibers of the deltoid Kgament of the ankle-joint;
its 'posterior border presents a broad groove, the malleolar sulcus, directed obliquely
downward and medialward, and occasionally double; this sulcus lodges the tendons
of the Tibialis posterior and Flexor digitorum longus. The summit of the medial
malleolus is marked by a rough depression behind, for the attachment of the
deltoid ligament.
Structure. — -The structure of the tibia is like that of the other long bones. The compact waU
of the body is thickest at the junction of the middle and lower thirds of the bone.
Ossification. — The tibia is ossified from three centers (Figs. 260, 2G1): one for the body and
one for either extremity. Ossification begins in the center of the body, about the seventh week
of fetal life, and gradually extends toward the extremities. The center for the upper epiphysis
appears before or shortly after birth; it is flattened in form, and has a thin tongue-shaped process
in front, which forms the tuberosity (Fig. 260) ; that for the lower epiphysis appears in the second
year. The lower epiphj^sis joins the body at about the eighteenth, and the upper one joins about
the twentieth year. Two additional centers occasionally exist, one for the tongue-shaped process
of the upper epiphysis, which forms the tuberosity, and one for the medial malleolus.
The Fibula (Calf Bone).
The fibula (Figs. 258, 259) is placed on the lateral side of the tibia, with which
it is connected above and below. It is the smaller of the two bones, and, in
proportion to its length, the most slender of all the long bones. Its upper
extremity is small, placed toward the back of the head of the tibia, below the level
of the knee-joint, and excluded from the formation of this joint. Its lower extremity
inclines a little forward, so as to be on a plane anterior to that of the upper end;
it projects below the tibia, and forms the lateral part of the ankle-joint. The
bone has a body and two extremities.
The Upper Extremity or Head {capitulum fihid<E; proximal extremity). — The
upper extremity is of an irregular quadrate form, presenting above a flattened
articular surface, directed upward, forward, and medialward, for articulation with
a corresponding surface on the lateral condyle of the tibia. On the lateral side
is a thick and rough prominence continued behind into a pointed eminence, the
apex {styloid process), which projects upward from the posterior part of the head.
The prominence, at its upper and lateral part, gives attachment to the tendon of
the Biceps femoris and to the fibular collateral ligament of the knee-joint, the liga-
ment dividing the tendon into two parts. The remaining part of the circumference
of the head is rough, for the attachment of muscles and ligaments. It presents in
front a tubercle for the origin of the upper and anterior fibers of the Perona^us
longus, and a surface for the attachment of the anterior ligament of the head;
and behind, another tubercle, for the attachment of the posterior ligament of the
head and the origin of the upper fibers of the Soleus.
The Body or Shaft {corpus fihulce). — The body presents four borders — the
antero-lateral, the antero-medial, the postero-lateral, and the postero-medial ; and
four surfaces — anterior, posterior, medial, and lateral.
Borders. — The antero-lateral border begins above in front of the head, runs ver-
tically downward to a little below the middle of the bone, and then curving some-
what lateralward, bifurcates so as to embrace a triangular subcutaneous surface
immediately above the lateral malleolus. This border gives attachment to an
intermuscular septum, which separates the Extensor muscles on the anterior
surface of the leg from the Perona>i longus and brevis on the lateral surface.
The antero-medial border, or interosseous crest, is situated close to the medial
side of the preceding, and runs nearly parallel with it in the upper third of its
extent, but diverges from it in the lower two-thirds. It begins above just beneath
the head of the bone (sometimes it is quite indistinct for about 2.5 cm. below the
head), and ends at the apex of a rough triangular surface immediately above the
THE FIBULA
261
articular facet of the lateral malleolus. It serves for the attachment of the inter-
osseous membrane, which separates the Extensor muscles in front from the Flexor
muscles l)ehin(l.
The postero-lateral border is prominent; it begins above at the apex, and ends
below in the posterior border of the lateral malleolus. It is directed lateralward
above, backward in the middle of its course, backward, and a little medialward
below, and gives attachment to an aponeurosis which separates the Perona'i on
the lateral surface from the Flexor muscles on the posterior surface.
The postero-medial border, sometimes called the oblique line, begins above at the
medial side of the head, and ends by becoming continuous with the interosseous
crest at the lower fourth of the bone. It is well-marked and prominent at the upper
and middle parts of the bone. It gives attachment to an aponeurosis which sep-
arates the Tibialis posterior from the Soleus and Flexor hallucis longus.
For talus
Upper extremity
Interosseous
crest
Appears about
ith year
Unites about
25th year
For posterior
talofibular ligt.
Appears at
2nd' year
Unites about
20th year
Lower extremity
Fig. 262. — Lower extremity of right fibula.
Medial aspect.
Fig. 263. — Plan of ossification of the
fibula. From three centers.
Surfaces. — The anterior surface is the interval between the antero-lateral and
antero-medial borders. It is extremely narrow and flat in the upper third of its
extent; broader and grooved longitudinally in its lower third; it serves for the
origin of three muscles: the Extensor digitorum longus. Extensor hallucis longus,
and Peronjvus tertius.
The posterior surface is the space included between the postero-lateral and the
postero-medial borders; it is contiiuious below with the triangular area above
the articular surface of the lateral malleolus; it is directed backward above, back-
ward and medialward at its middle, directly medialward below. Its upper third
is rough, for the origin of the Soleus; its lower part presents a triangular surface,
connected to the tibia by a strong interosseous ligament; the intervening part of
the surface is covered by the fibers of origin of the Flexor hallucis longus. Near
the middle of this surface is the nutrient foramen, which is directed downward.
The medial surface is the interval included between the antero-medial and the
postero-medial borders. It is grooved for the origin of the Tibialis posterior.
262
OSTEOLOGY
The lateral surface is the space between the antero-lateral and postero-lateral
borders. It is broad, and often deeply grooved; it is directed lateralward in the
upper two-thirds of its course, backward in the lower third, where it is continuous
with the posterior border of the lateral malleolus. This surface gives origin to
the Peronpei longus and brevis.
The Lower Extremity or Lateral Malleolus {malleolus lateralis; distal extremity;
external malleolus). — The lower extremity is of a pyramidal form, and somewhat
flattened from side to side; it descends to a lower level than the medial malleolus.
The lateral surface is convex, subcutaneous, and continuous with the triangular,
subcutaneous surface on the lateral side of the body. The medial surface (Fig.
262) presents in front a smooth triangular surface, convex from abo^•e downward,
which articulates with a corresponding surface on the lateral side of the talus.
Behind and beneath the articular surface is a rough depression, which gives attach-
ment to the posterior talofibular ligament. The anterior border is thick and rough,
and marked below by a depression for the attachment of the anterior talofibular
ligament. The posterior border is broad and presents the shallow malleolar sulcus,
for the passage of the tendons of the Perona?i longus and brevis. . The summit
is rounded, and give attachment to the calcaneofibular ligament.
Ossification. — The fibula is ossified from three centers (Fig. 263) : one for the body, and one
for either end. Ossification begins in the body about the eighth week of fetal life, and extends
toward the extremities. At birth the ends are cartilaginous. Ossification commences in the
lower end in the second year, and in the upper about the fourth year. The lower epiphysis,
the first to ossify, unites with the body about the twentieth year; the upper epiphysis joins
about the twenty-fifth year.
Groove for Peronoeus longus
Trochlear process
Middle articular surface
Anterior artic. surface
Post, artic. surface
Trochlear process
For cuboid bone
For attachment
of plantar calcaneo-
cuboid ligament
Sustentaculum
tali
Sustentaculum
tali
.j*[jff Sulcus calcanei
Tuberosity
Fig. 264. — Left calcaneus, superior surface.
Sulcus for Flexor
haUucis longus
Medial process
Tuberosity
Lateral process
Fig. 265. — Left calcaneus, inferior surface.
THE FOOT.
The skeleton of the foot (Figs. 268 and 269) consists of three parts: the tarsus,
metatarsus, and phalanges.
THE TARSUS
263
The Tarsus (Ossa Tarsi).
The tarsal bones are seven in numl)er, viz., the calcaneus, talus, cuboid, navicular,
and the first, second, and third cuneiforms.
The Calcaneus (o5 calcis) (Figs. 264 to 267).— The calcaneus is the largest of the
tarsal bones. It is situated at the lower and back part of the foot, serving to
transmit the weight of the body to the ground, and forming a strong lever for
the muscles of the calf. It is irregularly cuboidal in form, having its long axis
directed forward and lateralward; it presents for examination six surfaces.
Sulcus calcanei
Middle articular surface for talus
Posterior articular surface for talus
Trochlear process
Groove for Peronceus longus
Lateral process
Tuberosity
Fig. 266. — Left calcaneus, lateral surface.
Middle articular surface for talus
. Sustentaculum tali
Posterior articular surface for talus
Tuberosity
Anterior articular surface
for talus
Sulcus for Flexor
hallucis longy^
Medial process
Fig. 267. — Left calcaneus, medial surface.
For cuboid bone
Surfaces. — The superior surface extends behind on to that part of the bone which
projects backward to form the heel. This varies in length in different individuals,
is convex from side to side, concave from before backward, and supports a mass of
fat placed in front of the tendo calcaneus. In front of this area is a large usually
somewhat oval-shaped facet, the posterior articular surface, which looks upward
and forward; it is convex from behind forward, and articulates with the posterior
calcaneal facet on the under surface of the talus. It is bounded anteriorl}' by a
deep depression w^hich is continued backward and medialward in the form of a
groove, the calcaneal sulcus. In the articulated foot this sulcus lies below a similar
one on the under surface of the talus, and the two form a canal (sinus tarsi) for the
264
OSTEOLOGY
Groove J'or tendon of
Peron^us longus
Groove for tendon of
PERON^fS BREVIS
PERONiETJS TERTITTS
PeRONjEUB BREVIS
Groove for tendon of
Flexor hallucis longus
Tarsus
Metatarsus
-Ext. digitorcm bretis
Phalanges
Ext. hallccis longps
Fig. 268. — Bonea of the right foot. Dorsal surface.
THE TARSUS
265
Abductor hallucis
Medial head of
Lateral head of quadratus
PLAKT^
Flexor hallccis brkvis
Tubercle of
naviczdar
Tibialis anterior -(
Two sesamoid
bones
Flexor brevis
and abductor
DIGITI t(UINTI
Flexor digitorum
BREVIS
Flexor digitorum
LONGUS
Fig. 269. — Bones of the right foot. Plantar surface.
266 OSTEOLOGY
lodgement of the interosseous talocalcaneal ligament. In front and to the medial
side of this groove is an elongated facet, concave from behind forward, and with its
long axis directed forward and lateralward. This facet is frequently divided into
two by a notch : of the two, the posterior, and larger is termed the middle articular
surface; it is supported on a projecting process of bone, the sustentaculum tali,
and articulates with the middle calcaneal facet on the under surface of the talus;
the anterior articular surface is placed on the anterior part of the body, and articu-
lates with the anterior calcaneal facet on the talus. The upper surface, anterior
and lateral to the facets, is rough for the attachment of ligaments and for the origin
of the Extensor digitorum brevis.
The inferior or plantar surface is uneven, wider behind than in front, and con\ex
from side to side; it is bounded posteriorly by a transverse elevation, the calcaneal
tuberosity, which is depressed in the middle and prolonged at either end into a
process; the lateral process, small, prominent, and rounded, gives origin to part
of the Abductor digiti quinti; the medial process, broader and larger, gives attach-
ment, by its prominent medial margin, to the Abductor hallucis, and in front
to the Flexor digitorum brevis and the plantar aponeurosis; the depression between
the processes gives origin to the Abductor digiti quinti. The rough surface in
front of the processes gives attachment to the long plantar ligament, and to the
lateral head of the Quadratus plantse; while to a prominent tubercle nearer the
anterior part of this surface, as well as to a transverse groove in front of the tubercle,
is attached the plantar calcaneocuboid ligament.
The lateral surface is broad behind and narrow in front, flat and almost sub-
cutaneous; near its center is a tubercle, for the attachment of the calcaneofibular
ligament. At its upper and anterior part, this surface gives attachment to the
lateral talocalcaneal ligament; and in front of the tubercle it presents a narrow
surface marked by two oblique grooves. The grooves are separated by an elevated
ridge, or tubercle, the trochlear process {^peroneal tubercle), which varies much in
size in different bones. The superior groove transmits the tendon of the Peronaeus
brevis; the inferior groove, that of the Peronseus longus.
The medial surface is deeply' concave; it is directed obliquely downward and
forward, and serves for the transmission of the plantar vessels and nerves into the
sole of the foot; it affords origin to part -of the Quadratus plantae. At its upper
and forepart is a horizontal eminence, the sustentaculum tali, which gives attach-
ment to a slip of the tendon of the Tibialis posterior. This eminence is concave
above, and articulates with the middle calcaneal articular surface of the talus;
below, it is grooved for the tendon of the Flexor hallucis longus; its anterior margin
gives attachment to the plantar calcaneonavicular ligament, and its medial,
to a part of the deltoid ligament of the ankle-joint.
The anterior or cuboid articular surface is of a somewhat triangular form. It is
concave from above downward and lateralward, and convex in a direction at right
angles to this. Its medial border gives attachment to the plantar calcaneonavicular
ligament.
The posterior surface is prominent, convex, wider below than above, and divisible
into three areas. The lowest of these is rough, and covered by the fatty and fibrous
tissue of the heel; the middle, also rough, gives insertion to the tendo calcaneus
and Plantaris; while the highest is smooth, and is covered by a bursa which inter-
venes between it and the tendo calcaneus.
Articulations. — The calcaneus articulates with two bones: the talus and cuboid.
The Talus {astragalus; ankle hone) (Figs. 270 to 273).— The talus is the second
largest of the tarsal bones. It occupies the middle and upper part of the tarsus,
supporting the tibia above, resting upon the calcaneus below, articulating on
either side with the malleoli, and in front with the navicular. It consists of a
body, a neck, and a head
THE TARSUS
267
The Body (corpus tali).~The superior surface of the bodv presents, behind, a
smooth trochlear surface, the trochlea, for articulation with the tihia. The trochlea
is broader in front than behind, convex from before backward, slightlv concave
from side to side: in front it is continuous with the upper surface of the neck of
the bone.
For medial malleolus
Head
Neck
For lateral malleolu
For inferior transverse ligament
n
Medial tubercle
Sulcus for Flexor hallucis longus
Trochlea, for tihia
Lateral tubercle
Fig. 270. — Left talus, from above.
For plantar calcaneonavicular ligament
For navicular bone
Anterior calcaneal articular surface
Sulcus tali
^Posterior calcaneal articular
surface
Lateral tubercle
Sulcus for Flexor hallucis longus
Middle calcaneal articular surface
Fig. 271. — Left talus, from below.
The inferior surface presents two articular areas, the posterior and middle cal-
caneal surfaces, separated from one another by a deep groove, the sulcus tali.
The groove runs obliquely forward and lateralward, becoming gradually broader
and deeper in front: in the articulated foot it lies above a similar groove upon
the upper surface of the calcaneus, and forms, with it, a canal (sinus tarsi) filled
268
OSTEOLOGY
up in the fresli state by the interosseous talocalcaneal ligament. The posterior
calcaneal articular surface is large and of an oval or oblong form. It articulates
with the corresponding facet on the upper surface of the calcaneus/ and is deeply
concave in the direction of its long axis which runs forward and lateralward at
an angle of about 45° with the median plane of the body. The middle calcaneal
articular surface is small, oval in form and slightly convex; it articulates with the
upper surface of the sustentaculum tali of the calcaneus.
The medial surface presents at its upper part a pear-shaped articular facet for
the medial malleolus, continuous above with the trochlea; below the articular
surface is a rough depression for the attachment of the deep portion of the deltoid
ligament of the ankle-joint.
Trochlea for tibia
Sulcus for Flex, hallucis longus
For medial malleolus
Neck
For navicular bone
For plantar calcaneonavicular ligament
Fig. 272. — Left talus, medial surface.
For lateral malleolus
Sulcus tali
Anterior calcaneal articular surface
For navicular bone
Fig. 273. — Left talus, lateral surface.
Posterior calcaneal articular
surface
The lateral surface carries a large triangular facet, <3oncave from above downward,
for articulation with the lateral malleolus; its anterior half is continuous above with
the trochlea; and in front of it is a rough depression for the attachment of the ante-
rior talofibular ligament. Between the posterior half of the lateral border of the
trochlea and the posterior part of the base of the fibular articular surface is a tri-
angular facet (Fawcett^) which comes into contact with the transverse inferior
tibiofibular ligament during flexion of the ankle-joint; below the base of this facet
is a groove which affords attachment to the posterior talofibular ligament.
The posterior surface is narrow, and traversed by a groove running obliquely
' Sewell (Journal of Anatomy and Physiology, vol. xxxviii) pointed out that in about 10 per cent, of bones a small
triangular facet, continuous with the posterior calcaneal facet, is present at the junction of the lateral surface of the
body with the posterior wall of the sulcus tali.
2 Edinburgh Medical Journal, 1895.
THE TARSUS
269
downward and medialward, and transmitting the tendoa of the Flexor hallucis
longus. Lateral to the groove is a prominent tubercle, the posterior process, to
which the posterior talofibular ligament is attached; this process is sometimes
separated from the rest of the talus, and is then known as the os trigonum. Medial
to the groove is a second smaller tubercle.
The Neck (collum tali) .—The neck is directed forward and medialward, and
comprises the constricted portion of the bone between the body and the oval head.
Its upper and medial surfaces are rough, for the attachment of ligaments; its lateral
surface is concave and is continuous below with the deep groove for the inter-
osseous talocalcaneal ligament.
The Head (cajyut tali). — The head looks forward and medialward; its anterior
articular or navicular surface is large, oval, and convex. Its inferior surface has two
facets, which are best seen in the fresh condition. The medial, situated in front
of the middle calcaneal facet, is convex, triangular, or semi-oval in shape, and
rests on the plantar calcaneonavicular ligament; the lateral, named the anterior
calcaneal articular surface, is somewhat flattened, and articulates with the facet on
the U])per surface of the anterior part of the calcaneus.
Articulations. — The talus articulates with four bones: tibia, fibula, calcaneus, and navicular.
The Cuboid Bone (os cuboideum) (Figs. 274, 275).— The cuboid bone is placed on
the lateral side of the foot, in front of the calcaneus, and behind the fourth and fifth
metatarsal bones. It is of a pyramidal shape, its base being directed medialward.
For 3rd cuneiform For Ath metatarsal
Occasional facet
for navicular
For 5th
metatarsal
Peronceal Tuberosity For calcaneus
sulcus
Fig. 274. — The left cuboid. Antero-medial view.
Fig. 275. — The left cuboid. Postero-lateral view.
Surfaces.^ — The dorsal surface, directed upward and lateralward, is rough, for the
attachment of ligaments. The plantar surface presents in front a deep groove,
the peroneal sulcus, which runs obliquely forward and medialward; it lodges the
tendon of the Peronseus longus, and is bounded behind by a prominent ridge,
to which the long plantar ligament is attached. The ridge ends laterally in an
eminence, the tuberosity, the surface of which presents an oval facet; on this facet
glides the sesamoid bone or cartilage frequently found in the tendon of the Pero-
nseus longus. The surface of bone behind the groove is rough, for the attachment
of the plantar calcaneocuboid ligament, a few fibers of the Flexor hallucis brevis,
and a fasciculus from the tendon of the Tibialis posterior. The lateral surface
presents a deep notch formed by the commencement of the peroneal sulcus. The
posterior surface is smooth, triangular, and concavo-convex, for articulation with
the anterior surface of the calcaneus; its infero-medial angle projects backward
as a process which underlies and supports the anterior end of the calcaneus. The
anterior surface, of smaller size, but also irregularly triangular, is divided by a
vertical ridge into two facets: the medial, quadrilateral in form, articulates with
the fourth metatarsal; the lateral, larger and more triangular, articulates with the
fifth. The medial surface is broad, irregularly quadrilateral, and presents at
its middle and upper part a smooth oval facet, for articulation with the third
270
OSTEOLOGY
cuneiform; and behind this (occasionally) a smaller facet, for articulation with
the navicular; it is rough in the rest of its extent, for the attachment of strong
interosseous ligaments.
Articulations. — The cuboid articulates with four bones: the calcaneus, third cuneiform, and
fourth and fifth metatarsals; occasionally with a fifth, the navicular.
The Navicular Bone {os naviculare pedis; scaphoid hone) (Figs. 276, 277). — The
navicular bone is situated at the medial side of the tarsus, between the talus
behind and the cuneiform bones in front.
For 2nd cuneiform
For 1st cuneiform
For 3rd
cuneiform
Fig. 27G. — The left navicular.
Occasional
acet for
cuboid
Antero-lateral view.
\^
For talus Tuberosity
Fig. 277. — Theleft navicular. Postero-medialview.
Surfaces. — The anterior surface is convex from side to side, and subdivided by two
ridges into three facets, for articulation with the three cuneiform bones. The
posterior surface is oval, concave, broader laterally than medially, and articulates
with the rounded head of the talus. The dorsal surface is convex from side to side,
and rough for the attachment of ligaments. The plantar surface is irregular, and
also rough for the attachment of ligaments. The medial surface presents a rounded
tuberosity, the lower part of which
For 2nd For gives attachment to part of the
For 1st metatarsal metatarsal 2nd cuneiform tendon of the Tibialis posterior.
The lateral surface is rough and
irregular for the attachment of
ligaments, and occasionally pre-
sents a small facet for articula-
tion with the cuboid bone.
Articulations. — Thenavicular articu-
lates with four bones: the talus and
the three cuneiforms; occasionally with
a fifth, the cuboid.
For tendon of
Tibialis atiterior
For Tvavicvlar
Fig. 278.— The left fir.st cunei-
form. Antero-niedial view.
Fig. 279. — The left first cunei-
form. Postero-lateral view.
The First Cuneiform Bone {os
cuneiform primum; intcrnalcunci-
form) (Figs. 278, 279) .—The first
cuneiform bone is the largest of
the three cuneiforms. It is situated at the medial side of the foot, between the
navicular behind and the base of the first metatarsal in front.
Surfaces. — The medial surface is subcutaneous, broad, and quadrilateral; at its
anterior plantar angle is a smooth oval impression, into which part of the tendon
of the Tibialis anterior is inserted; in the rest of its extent it is rough for the
attachment of ligaments. The lateral surface is concave, presenting, along its
superior and posterior borders a narrow L-shaped surface, the vertical limb and
posterior part of the horizontal limb of which articulate with the second cuneiform,
while the anterior part of the horizontal limb articulates with the second metatarsal
THE TARSUS
271
bone: the rest of this surface is rough for the attachment of ligaments and part
of the tendon of the Peronjieus longus. The anterior surface, kidney-shaped and
much larger than the posterior, articulates with the first metatarsal bone. The
posterior surface is triangular, concave, and articulates with the most medial and
largest of the three facets on the anterior surface of the navicular. The plantar
surface is rough, and forms the base of the wedge; at its back part is a tuberosity
for the insertion of part of the tendon of the Tibialis posterior. It also gives
insertion in front to part of the tendon of the Tibialis anterior. The dorsal surface
is the narrow end of the wedge, and is directed upward and lateralward; it is
rough for the attachment of ligaments.
Articulations. — The first cuneiform articulates with /our bones: the navicular, second cunei-
form, and first and second metatarsals.
The Second Cuneiform Bone {os cuneiforme secundum; middle cuneiform) (Figs.
280, 281). — The second cuneiform bone, the smallest of the three, is of very reg-
ular wedge-like form, the thin end being directed downward. It is situated between
the other two cuneiforms, and articulates with the navicular behind, and the
second metatarsal in front.
Surfaces. — The anterior surface, triangular in form, and narrower than the pos-
terior, articulates with the base of the second metatarsal bone. The posterior sur-
face, also triangular, articulates with the intermediate facet on the anterior surface
of the navicular. The medial surface carries an L-shaped articular facet, runnmg
along the superior and posterior borders, for articulation with the first cuneiform,
and is rough in the rest of its extent for the attachment of ligaments. The lateral
For 1st cuneiform
For navicular
For 2nd metatarsal For Zrd cuneiform
Fig. 280.-
cuneiform,
view.
—The left second
An t e r o-m e d i a 1
Fig. 281. — The left
second cuneiform. Pos-
tero-lateral view.
surface presents posteriorly a smooth
facet for articulation with the third
cuneiform bone. The dorsal surface
forms the base of the wedge; it is
quadrilateral and rough for the at-
tachment of ligaments. The plantar
surface, sharp and tuberculated, is
also rough for the attachment of
ligaments, and for the insertion of a
slip from the tendon of the Tibialis
posterior.
Articulations. — The second cuneiform articulates with four bones: the navicular, first and
third cuneiforms, and second metatarsal.
The Third Cuneiform Bone {os cuneiforme tertium; external cuneiform) (Figs. 282,
283). — -The third cuneiform bone, intermediate in size between the two preceding,
is wedge-shaped, the base being uppermost. It occupies the center of the front row
of the tarsal bones, between the second cuneiform medially, the cuboid laterally,
the navicular behind, and the third metatarsal in front.
Surfaces. — The anterior surface, triangular in form, articulates with the third
metatarsal bone. The posterior surface articulates with the lateral facet on the
anterior surface of the navicular, and is rough below for the attachment of liga-
mentous fibers. The medial surface presents an anterior and a posterior articular
facet, separated by a rough depression: the anterior, sometimes divided, articulates
with the lateral side of the base of the second metatarsal bone ; the posterior skirts
the posterior border, and articulates with the second cuneiform; the rough depres-
sion gives attachment to an interosseous ligament. The lateral surface also pre-
sents two articular facets, separated by a rough non-articular area; the anterior
facet, situated at the superior angle of the bone, is small and semi-oval in shape,
and articulates with the medial side of the base of the fourth metatarsal bone;
272
OSTEOLOGY
the posterior and larger one is triangular or oval, and articulates with the cuboid;
the rough, non-articular area serves for the attachment of an interosseous ligament.
The three facets for articulation with the three metatarsal bones are continuous
with one another; those for articulation with the second cuneiform and na\icular
are also continuous, but that for articulation with the cuboid is usually separate.
The dorsal surface is of an oblong form, its postero-lateral angle being prolonged
backward. The plantar sixrface is a rounded margin, and serves for the attachment
of part of the tendon of the Tibialis posterior, part of the Flexor hallucis brevis,
and ligaments.
Articulations. — The third cuneiform articulates with six bones: the navicular, second cunei-
form, cuboid, and second, third, and fourth metatarsals.
For navicular For 2nd cuneiform
Fig. 2S2.-
-The left third cuneiform.
\"iew.
For 2nd
metatarsal
Postero-medial
For ith
tnclaiarsal
For cuboid
Fig.
ForZrd
metatarsal
283. — The third left cuneiform,
lateral view.
Antero-
The Metatarsus.
The metatarsus consists of five bones which are numbered from the medial
side {ossa metatarsalia I.-V.); each presents for examination a body and two
extremities.
Common Characteristics of the Metatarsal Bones. — The body is prismoid in
form, tapers gradually from the tarsal to the phalangeal extremity, and is curved
longitudinally, so as to be concave below, slightly convex above. The base or
posterior extremity is wedge-shaped, articulating proximally with the tarsal bones,
and by its sides with the contiguous metatarsal bones: its dorsal and plantar
surfaces are rough for the attachment of ligaments. The head or anterior extremity
presents a convex articular surface, oblong from above downward, and extend-
ing farther backward below than above. Its sides are flattened, and on each is a
depression, surmounted by a tubercle, for ligamentous attachment. Its plantar
surface is grooved antero-posteriorly for the passage of the Flexor tendons, and
marked on either side bv an articular eminence continuous with the terminal
articular surface.
Characteristics of the Individual Metatarsal Bones. — The First Metatarsal
Bone {os metatarsale I; metatarsal bone of the great toe) (Fig. 284). — The first
metatarsal bone is remarkable for its great thickness, and is the shortest of
the metatarsal bones. The body is strong, and of well-marked prismoid form.
The base presents, as a rule, no articular facets on its sides, but occasionally
on tlie lateral side there is an oval facet, by which it articulates with the second
metatarsal. Its proximal articular surface is of large size and kidney-shaped; its
circumference is grooved, for the tarsometatarsal ligaments, and medially gives
insertion to part of the tendon of the Tibialis anterior; its plantar angle presents
a rough oval prominence for the insertion of the tendon of the Peronieus longus.
The head is large; on its plantar surface are two grooved facets, on which glide
sesamoid bones; the facets are separated by a smooth elevation.
THE METATARSUS
273
The Second Metatarsal Bone {os metatarsale II) (Fig. 285).— The second meta-
tarsal bone is the longest of the metatarsal bones, being prolonged backward
For sesamoid bones
For 1st For Peroncsus
cuneiform longus
Fig. 284. — The first metatarsal. (Left.)
For 3rd
metatarsal
For 1st
cuneiform For 2nd For Hnl
cuneiform cuneiform
FiQ. 285. — The second metatarsal. (Left.)
F(yr 2nd
metatarsal
For
Brd
cuneiform
Fig. 286. — The third metatarsal. (Left.)
'or 2tld
meta-
tarsal
For Uh
metatarsal
For 3ra
metatarsal
For cuboid J
Far %rd cuneiform For 5th metatarsal
Fig. 287. — The fourth metatarsal. (Left.)
into the recess formed by the three cuneiform bones. Its base is broad above,
narrow and rough below. It presents four articular surfaces: one behind, of a
triangular form, for articulation with the second cuneiform; one at the upper part
18
274
OSTEOLOGY
of its medial surface, for articulation with the first cuneiform ; and two on its lateral
surface, an upper and lower, separated by a rough non-articular interval. Each
of these lateral articular surfaces is divided into two by a vertical ridge; the two
anterior facets articulate with the third metatarsal; the two posterior (sometimes
continuous) with the third cuneiform. A fifth facet is occasionally present for
articulation with the first metatarsal; it is oval in shape, and is situated on the
medial side of the body near the base.
The Third Metatarsal Bone {os metatarsale III) (Fig. 286). — The third meta-
tarsal bone articulates proximally, by means of a triangular smooth surface,
with the third cuneiform; medially, by two facets, with the second metatarsal;
and laterally, by a single facet, with the fourth metatarsal. This last facet is
situated at the dorsal angle of the base.
;n
For 4:th
metatarsal For cuboid Tvberosity
Fig. 288.— The fifth metatarsal. (Left.)
The Fourth Metatarsal Bone {os metatarsale IV) (Fig. 287). — The fourth meta-
tarsal bone is smaller in size than the preceding; its base presents an oblique
quadrilateral surface for articulation with the cuboid ; a smooth facet on the medial
side, divided by a ridge into an anterior portion for articulation with the third
metatarsal, and a posterior portion for articulation with the third cuneiform; on
the lateral side a single facet, for articulation with the fifth metatarsal.
The Fifth Metatarsal Bone {os metatarsale V) (Fig. 288).— The fifth metatarsal
bone is recognized by a rough eminence, the tuberosity, on the lateral side of its
base. The base articulates behind, by a triangular surface cut obliquely in a trans-
verse direction, with the cuboid; and medially, with the fourth metatarsal. On
the medial part of its dorsal surface is inserted the tendon of the Peronseus tertius
and on the dorsal surface of the tuberosity that of the Peronaeus brevis. A strong
band of the plantar aponeurosis connects the projecting part of the tuberosity
with the lateral process of the tuberosity of the calcaneus. The plantar surface
of the base is grooved for the tendon of the Abductor digiti quinti, and gives origin
to the Flexor digiti quinti brevis.
Articulations. — The base of each metatarsal bone articulates with one or more of the tarsal
bones, and the head with one of the first row of phalanges. The first metatarsal articulates with
the first cuneiform, the second with all three cuneiforms, the third with the third cuneiform, the
fourth with the third cuneiform and the cuboid, and the fifth with the cuboid.
THE PHALANGES OF THE FOOT
275
The Phalanges of the Foot (Phalanges Digitorum Pedis).
The phalanges of the foot correspond, in number and general arrangement,
with those of the hand; there are two in the great toe, and three in each of the
other toes. They differ from them, however, in their size, the bodies being much
reduced in length, and, especially in the first row, laterally compressed.
First Row. — The body of each is compressed from side to side, convex above,
concave below. The base is concave; and the head presents a trochlear surface
for articulation with the second phalanx.
Second Row. — The phalanges of the second row are remarkably small and short,
but rather broader than those of the first row.
The ungual phalanges, in form, resemble those of the fingers; but they are smaller
and are flattened from above downward; each presents a broad base for articula-
tion with the corresponding bone of the second row, and an expanded distal
extremity for the support of the nail and end of the toe.
TARSUS.
One center for each bone,
except calcaneus
OUTER FOUR METATARSALS.
Tv)o centers for each bone .
One for body
One for head
PHALANGES.
Two centers for each bone :
One for body
One for metatarsal
extremity
Appears 10th year;
unites after puberty
Appears 3rd year
Unite I8th-20th year
Appears 7th week
Apps. Ith wk. —
Unite 18-20 yr. | m
Apps. 3rd yr.
App. 4th yr
Unite 17-18 yr. >
^S)
f:::^*
App. 2-4 mo. — '
App. 6-7th yr. .
Unite 17-18 rjr. I \
App. 2-4 »no.
App. 6th yr. ^
Unite 17-18 yr. ] I
App. 7th wk. — W|:
CD
Fig. 289. — Plan of ossification of the foot.
Articulations.— In the second, third, fourth, and fifth toes the phalanges of the first row articu-
late behind with the metatarsal bones, and in front with the second phalanges, which in their
turn articulate with the first and third: the ungual phalanges articulate with the second.
Ossification of the Bones of the Foot (Fig. 289).— The tarsal bones are each ossified from a
dngle center, excepting the calcaneus, which has an epiphysis for its posterior extremity, ihe
centers make their appearance in the following order: calcaneus at the sixth month ot tetal lile,
276 OSTEOLOGY
talus, about the seventh month; cuboid, at the ninth month; third cuneiform, during the first
year; first cuneiform, in the third year; second cuneiform and navicular, in the fourth year.
The epiphysis for the posterior extremity of the calcaneus appears at the tenth year, and unites
with the rest of the bone soon after puberty. The posterior process of the talus is sometimes
ossified from a separate center, and may remain distinct from the main mass of the bone, when
it is named the os trigonum.
The metatarsal bones are each ossified from Iwo centers: one for the body, and one for the
head, of the second, third, fourth, and fifth metatarsals; one for the body, and one for the base,
of the first metatarsal.^ Ossification commences in the center of the body about the ninth week,
and extends toward either extremity. The center for the base of the first metatarsal appears
about the third year; the centers for the heads of the other bones between the fifth and eighth
years; they join the bodies between the eighteenth and twentieth years.
The phalanges are each ossified from two centers: one for the body, and one for the base.
The center for the body appears about the tenth week, that for the base between the fourth and
tenth years; it joins the body about the eighteenth year.
Comparison of the Bones of the Hand and Foot.
The hand and foot are constructed on somewhat similar principles, each con-
sisting of a proximal part, the carpus or the tarsus, a middle portion, the meta-
carpus, or the metatarsus, and a terminal portion, the phalanges. The proximal
part consists of a series of more or less cubical bones which allow a slight amount
of gliding on one another and are chiefly concerned in distributing forces transmitted
to or from the bones of the arm or leg. The middle part is made up of slightly
movable long bones which assist the carpus or tarsus in distributing forces and
also give greater breadth for the reception of such forces. The separation of the
individual bones from one another allows of the attachments of the Interossei and
protects the dorsi-palmar and dorsi-plantar vascular anastomoses. The terminal
portion is the most movable, and its separate elements enjoy a varied range of
movements, the chief of which are flexion and extension.
Fig. 290. — Skeleton of foot. Medial aspect.
The function of the hand and foot are, however, very different, and the general
similarity between them is greatly modified to meet these requirements. Thus the
foot forms a firm basis of support for the body in the erect posture, and is there-
fore more solidly built up and its component parts are less movable on each other
than those of the hand. In the case of the phalanges the difference is readily
noticeable; those of the foot are smaller and their movements are more limited
than those of the hand. Very much more marked is the difference between the
metacarpal bone of the thumb and the metatarsal bone of the great toe. The meta-
carpal bone of the thumb is constructed to permit of great mobility, is directed at
an acute angle from that of the index finger, and is capable of a considerable range
1 As was noted in the first metacarpal (see footnote, page 231), so in the first metatarsal, there is often a second
epiphysis for its head.
THE SESAMOID BONES
277
of movements at its articulation with the carpus. The metatarsal bone of the
great toe assists in supporting the weight of the body, is constructed with great
solidity, lies parallel with the other metatarsals, and has a very limited degree of
mobility. The carpus is small in proportion to the rest of the hand, is placed
in line with the forearm, and forms a transverse arch, the concavity of which
constitutes a bed for the Flexor tendons and the palmar vessels and nerves. The
tarsus forms a considerable part of the foot, and is placed at right angles to the
leg, a position which is almost peculiar to man, and has relation to his erect pos-
ture. In order to allow of their supporting the weight of the body with the least
expenditure of material the tarsus and a part of the metatarsus are constructed
in a series of arches (Figs. 290, 291), the disposition of which will be considered
after the articulations of the foot have been described.
Fig. 291. — Skeleton of foot. Lateral aspect.
The Sesamoid Bones (Ossa Sesamoidea).
Sesamoid bones are small more or less rounded masses embedded in certain
tendons and usually related to joint surfaces. Their functions probably are to
modify pressure, to diminish friction, and occasionally to alter the direction of a
muscle pull. That they are not developed to meet certain physical requirements
in the adult is evidenced by the fact that they are present as cartilaginous nodules
in the fetus, and in greater numbers than in the adult. They must be regarded,
according to Thilenius, as integral parts of the skeleton phylogenetically inherited.^
Physical necessities probably come into play in selecting and in regulating the
degree of development of the original cartilaginous nodules. Nevertheless, irreg-
ular nodules of bone may appear as the result of intermittent pressure in certain
regions, e. g., the "rider's bone," which is occasionally developed in the Adductor
muscles of the thigh.
Sesamoid bones are invested by the fibrous tissue of the tendons, except on the
surfaces in contact with the parts over which they glide, where they present
smooth articular facets.
In the upper extremity the sesamoid bones of the joints are found only on the
palmar surface of the hand. Two, of which the medial is the the larger, are constant
at the metacarpophalangeal joint of the thumb; one is frequently present in the
corresponding joint of the little finger, and one (or two) in the same joint of the
index finger. Sesamoid bones are also found occasionally at the metacarpopha-
langeal joints of the middle and ring fingers, at the interphalangeal joint of the
thumb and at the distal interphalangeal joint of the index finger.
In the lower extremity the largest sesamoid bone of the joints is the patella,
developed in the tendon of the Quadriceps femoris. On the plantar aspect of the
foot, two, of which the medial is the larger, are always present at the metatar-
> Morpholog. Arbeiten, 1906, v, 309.
278 OSTEOLOGY
sophalangeal joint of the great toe; one sometimes at the metatarsophalangeal
joints of the second and fifth toes, one occasionally at the corresponding joint of
the third and fourth toes, and one at the interphalangeal joint of the great toe.
Sesamoid bones apart from joints are seldom found in the tendons of the upper
limb; one is sometimes seen in the tendon of the Biceps brachii opposite the radial
tuberosity. They are, however, present in several of the tendons of the lower
limb, viz., one in the tendon of the Peronseus longus, where it glides on the cuboid;
one, appearing late in life, in the tendon of the Tibialis anterior, opposite the smooth
facet of the first cuneiform bone ; one in the tendon of the Tibialis posterior, oppo-
site the medial side of the head of the talus; one in the lateral head of the Gastroc-
nemius, behind the lateral condyle of the femur; and one in the tendon of the Psoas
major, where it glides over the pubis. Sesamoid bones are found occasionally
in the tendon of the Glutaeus maximus, as it passes over the greater trochanter,
and in the tendons which wind around the medial and lateral malleoli.
SYNDESMOLOGY.
rjIHE bones of the skeleton are joined to one another at different parts of their
J- surfaces, and such connections are termed Joints or Articulations. ^Yhe^e
the joints are immomble, as in the articulations between practically all the bones
of the skull, the adjacent margins of the bones are almost in contact, being separated
merely by a thin layer of fibrous membrane, named the sutural ligament. In certain
regions at the base of the skull this fibrous membrane is replaced by a layer of car-
tilage. ^Yhe^e sligJit movement combined with great strength is required, the osseous
surfaces are united by tough and elastic fibrocartilages, as in the joints between the
vertebral bodies, and in the interpubic articulation. In the freely movable joints
the surfaces are completely separated; the bones forming the articulation are ex-
panded for greater convenience of mutual connection, covered by cartilage and
enveloped by capsules of fibrous tissue. The cells lining the interior of the fibrous
capsule form an imperfect membrane — the synovial membrane — which secretes
a lubricating fluid. The joints are strengthened by strong fibrous bands called
ligaments, which extend betw^een the bones forming the joint.
Bone. — Bone constitutes the fundamental element of all the joints. In the
long bones, the extremities are the parts which form the articulations; they are
generally somewhat enlarged; and consist of spongy cancellous tissue with a thin
coating of compact substance. In the flat bones, the articulations usually take
place at the edges; and in the short bones at various parts of their surfaces. The
layer of compact bone which forms the joint surface, and to which the articular
cartilage is attached, is called the articular lamella. It differs from ordinary
bone tissue in that it contains no Haversian canals, and its lacunae are larger
and have no canaliculi. The vessels of the cancellous tissue, as they approach
the articular lamella, turn back in loops, and do not perforate it; this layer is con-
sequently denser and firmer than ordinary bone, and is evidently designed to form
an unyielding support for the articular cartilage.
Cartilage. — Cartilage is a non-vascular structure which is found in various
parts of the body — in adult life chiefly in the joints, in the parietes of the thorax,
and in various tubes, such as the trachea and bronchi, nose, and ears, which require
to be kept permanently open. In the fetus, at an early period, the greater part
of the skeleton is cartilaginous; as this cartilage is afterward replaced by bone,
it is called temporary, in contradistinction to that which remains unossified during
the whole of life, and is called permanent.
Cartilage is divided, according to its minute structure, into hyaline cartilage,
white fibrocartilage, and yellow or elastic fibrocartilage.
Hyaline Cartilage. — Hyaline cartilage consists of a gristly mass of a firm consist-
ence, but of considerable elasticity and pearly bluish color. Except where it coats
the articular ends of bones, it is covered externally by a fibrous membrane, the
perichondrium, from the vessels of which it imbibes its nutritive fluids, being itself
destitute of bloodvessels. It contains no nerves. Its intimate structure is very
simple. If a thin slice be examined under the microscope, it will be found to consist
of cells of a rounded or bluntly angular form, lying in groups of two or more in
a granular or almost homogeneous matrix (Fig. 292). The cells, when arranged
in groups of two or more, have generallv straight outlines where they are in contact
(279)
280
SYNDESMOLOGY
with each other, and in the rest of their circumference are rounded. They con-
sist of clear translucent protoplasm in which fine interlacing filaments and minute
granules are sometimes present; imbedded in this are one or two round nuclei,
having the usual intranuclear network. The cells are contained in cavities in
the matrix, called cartilage lacunae; around these the matrix is arranged in con-
centric lines, as if it had been formed in successive portions around the cartilage
cells. This constitutes the so-called capsule of the space. Each lacuna is generally
occupied by a single cell, but dur-
ing the division of the cells it may
contain two, four, or eight cells.
The matrix is transparent and
apparently without structure, or
else presents a dimly granular ap-
pearance, like ground glass. Some
observers ha\'e shown that the
matrix of hyaline cartilage, and
especially of the articular variety,
after prolonged maceration, can
be broken up into fine fibrils.
These fibrils are probably of the same nature, chemically, as the white fibers
of connective tissue. It is believed by some histologists that the matrix is per-
meated by a number of fine channels, which connect the lacunae with each other,
and that these canals communicate with the lymphatics of the perichondrium,
and thus' the structure is permeated by a current of nutrient fluid.
Articular cartilage, costal cartilage, and temporary cartilage are all of the hyaline
variety. They present dift'erences in the size, shape, and arrangement of their
cells.
Fig. 292. — Human cartilage cells from the cricoid cartilage.
X 350
I Superficial flattened cells
^^^^^t 'ffsvQl \ Vertical rows of cells
' Calcified matrix
Jr- BoTie
Fig. 293. — Vertical section of articular cartilage.
Fig. 294. — Costal cartilage from a man, aged
seventy-six years, showing the development of
fibrous structure in the matrix. In several por-
tions of the specimen two or three generations of
cells are seen enclosed in a parent cell wall.
Highly magnified.
In Articular Cartilage (Fig. 293), which shows no tendency to ossification, the
matrix is finely granular; the cells and nuclei are small, and are disposed parallel
to the surface in the superficial part, while nearer to the bone they are arranged in
vertical rows. Articular cartilages have a tendency to split in a vertical direction ;
in disease this tendency becomes very manifest. The free surface of articular
cartilage, where it is exposed to friction, is not covered by perichondrium, although
a layer of connective tissue continuous with that of the synovial membrane can be
CARTILAGE
281
traced iu the adult over a small part of its circumference, and here the cartilage
cells are more or less branched and pass insensibly into the branched connective
tissue corpuscles of the synovial membrane. Articular cartilage forms a thin
incrustation upon the joint surfaces of the bones, and its elasticity enables it to
break the force of concussions, while its smoothness affords ease and freedom of
movement. It varies in thickness according to the shape of the articular surface
on which it lies; where this is convex the cartilage is thickest at the center, the
reverse being the case on concave articular surfaces. It appears to derive its
nutriment partly from the vessels of the neighboring synovial membrane and
partly from those of the bone upon which it is implanted. Toynbee has shown
that the minute vessels of the cancellous tissue as they approach the articular
lamella dilate and form arches, and then return into the substance of the bone.
In Costal Cartilage the cells and nuclei are large, and the matrix has a tendency
to fibrous striation, especially in old age (Fig. 294). In the thickest parts of the
costal cartilages a few large vascular channels may be detected. This appears,
at first sight, to be an exception to the statement that cartilage is a non-vascular
tissue, but is not so really, for the vessels give no branches to the cartilage sub-
stance itself, and the channels may rather be looked upon as involutions of the
perichondrium. The xiphoid process and the cartilages of the nose, larynx, and
trachea (except the epiglottis and corniculate cartilages of the larynx, which are
composed of elastic fibrocartilage) resemble the costal cartilages in microscopic
characteristics. The arvtenoid cartilage of the larvnx shows a transition from
hyaline cartilage at its base to elastic cartilage at the apex.
The hyaline cartilages, especially in adult and advanced life, are prone to calcify
— that is to say, to have their matrix permeated by calcium salts without any
appearance of true bone. The process of calcification occurs frequently, in such
cartilages as those of the trachea and in the costal cartilages, where it may be
succeeded by conversion into true bone.
White Fibrocartilage. — White fibrocartilage consists of a mixture of white fibrous
tissue and cartilaginous tissue in various proportions; to the former of these con-
stituents it owes its flexibility and
toughness, and to the latter its
elasticity. When examined under
the microscope it is found to be
made up of fibrous connective
tissue arranged in bundles, with
cartilage cells between the bundles;
the cells to a certain extent re-
semble tendon cells, but may be
distinguished from them by being
surrounded by a concentrically
striated area of cartilage matrix
and by being less flattened (Fig.
295) . The white fibrocartilages ad-
mit of arrangement into four
groups — interarticular, connecting,
circumferential, and stratiform. ,
1. The Interarticular Fibrocartilages {menisci) are flattened fibrocartilagmous
plates, of a round, oval, triangular, or sickle-like form, interposed between the
articular cartilages of certain joints. They are free on both surfaces, usually
thinner toward the center than at the circumference, and held m position by the
attachment of their margins and extremities to the surrounding ligaments, ihe
synovial membranes of the joints are prolonged over them. They are found
in the temporomandibular, sternoclavicular, acromioclavicular, wrist, and knee
Fig. 29o. — White fibrocartilage from an intervertebral
fibrocartilage.
282 SYNDESMOLOGY
joints — i. e., in those joints which are most exposed to violent concussion and
subject to frequent movement. Their uses are to obHterate the intervals between
opposed surfaces in their various motions; to increase the depths of the articular
surfaces and give ease to the gliding movements; to moderate the effects of great
pressure and deaden the intensity of the shocks to which the parts may be sub-
jected. Humphry has pointed out that these interarticular fibrocartilages serve
an important purpose in increasing the varieties of movement in a joint. Thus
in the knee joint there are two kinds of motion, viz., angular movement and rota-
tion, although it is a hinge joint, in which, as a rule, only one variety of motion
is permitted; the former movement takes place between the condyles of the femur
and the interarticular cartilages, the latter between the cartilages and the head
of the tibia. So, also, in the temporomandibular joint, the movements of opening
and shutting the mouth take place between the fibrocartilage and the mandible,
the grinding movement between the mandibular fossa and the fibrocartilage, the
latter moving with the mandible.
2. The Connecting Fibrocartilages are interposed between the bony surfaces of
those joints which admit of only slight mobility, as between the bodies of the
vertebrae. They form disks which are closely adherent to the opposed surfaces.
Each disk is composed of concentric rings of fibrous tissue, 'with cartilaginous
laminae interposed, the former tissue predominating toward the circumference,
the latter toward the center.
3. The Circumferential Fibrocartilages consist of rims of fibrocartilage, which
surround the margins of some of the articular cavities, e. g., the glenoidal labrum
of the hip, and of the shoulder; they serve to deepen the articular cavities and to
protect their edges.
4. The Stratiform Fibrocartilages are those which form a thin coating to osseous
grooves through which the tendons of certain muscles glide. Small masses of fibro-
cartilage are also developed in the tendons of some muscles, where they glide
over bones, as in the tendons of the Perona^us longus and Tibialis posterior.
The distinguishing feature of cartilage chemically is that it yields on boiling a
substance called chondrin, very similar to gelatin, but differing from it in several
of its reactions. It is now believed that chondrin is not a simple body, but a
mixture of gelatin with mucinoid substances, chief among which, perhaps, is a
compound termed chondro-mucoid.
Ligaments. — Ligaments are composed mainly of bundles of white fibrous tissue
placed parallel with, or closely interlaced with one another, and present a white,
shining, silvery appearance. They are pliant and flexible, so as to allow perfect
freedom of movement, but strong, tough, and inextensible, so as not to yield
readily to applied force. Some ligaments consist entirely of yellow elastic tissue,
as the ligamenta flava which connect together the laminae of adjacent vertebrae,
and the ligamentum nuchae in the lower animals. In these cases the elasticity of
the ligament is intended to act as a substitute for muscular power.
The Articular Capsules. — The articular capsules form complete envelopes for the
freely movable joints. Each capsule consists of two strata — an external {stratum
fibrosum) composed of white fibrous tissue, and an internal (stratum synoviale)
which is a secreting layer, and is usually described separately as the synovial
membrane.
The fibrous capsule is attached to the whole circumference of the articular end
of each bone entering into the joint, and thus entirely surrounds the articulation.
The synovial membrane invests the inner surface of the fibrous capsule, and is
reflected over any tendons passing through the joint cavity, as the tendon of the
Popliteus in the knee, and the tendon of the Biceps brachii in the shoulder. It is
composed of a thin, delicate, connective tissue, with branched connective-tissue
corpuscles. Its secretion is thick, viscid, and glairy, like the white of an egg, and
DEVELOPMENT OF THE JOINTS 283
is hence termed synovia. In the fetus this membrane is said, by Toynbee, to be
continued over the surfaces of the cartilages; but in the adult such a continuation
is wanting, excepting at the circumference of the cartilage, upon which it encroaches
for a short distance and to which it is firmly attached! In some of the joints the
synovial membrane is thrown into folds which pass across the cavity; they are
especially distinct in the knee. In other joints there are flattened folds, subdivided
at their margins into fringe-like processes which contain convoluted vessels.
These folds generally project from the synovial membrane near the margin of the
cartilage, and lie flat upon its surface. They consist of connective tissue, covered
with endothelium, and contain fat cells in variable quantities, and, more rarely,
isolated cartilage cells; the larger folds often contain considerable quantities of fat.
Closely associated with synovial membrane, and therefore conveniently described
in this section, are the mucous sheaths of tendons and the mucous bursoe.
Mucous sheaths (vagina; mucosos) serve to facilitate the gliding of tendons in
fibroosseous canals. Each sheath is arranged in the form of an elongated closed
sac, one layer of which adheres to the wall of the canal, and the other is reflected
upon the surface of the enclosed tendon. These sheaths are chiefly found surround-
ing the tendons of the Flexor and Extensor muscles of the fingers and toes as they
pass through fibroosseous canals in or near the hand and foot.
Bursse mucosae are interposed between surfaces which glide upon each other.
They consist of closed sacs containing a minute quantity of clear viscid fluid, and
may be grouped, according to their situations, under the headings subcutaneous,
submuscular, subfacial, and subtendinous.
DEVELOPMENT OF THE JOINTS.
The mesoderm from which the different parts of the skeleton are formed shows
at first no dilTerentiation into masses corresponding with the individual bones.
Thus continuous cores of mesoderm form the axes of the limb-buds and a continu-
ous column of mesoderm the future vertebral column. The first indications of the
bones and joints are circumscribed condensations of the mesoderm; these condensed
parts become chondrified and finally ossified to form the bones of the skeleton.
The intervening non-condensed portions consist at first of undift'erentiated meso-
derm, which may develop in one of three directions. It may be converted into
fibrous tissue as in the case of the skull bones, a synarthrodial joint being the
result, or it may become partly cartilaginous, in which case an amphiarthrodial
joint is formed. Again, it may become looser in texture and a cavity ultimately
appear in its midst; the cells lining the sides of this cavity form a synovial mem-
brane and thus a diarthrodial joint is developed.
The tissue surrounding the original mesodermal core forms fibrous sheaths for
the developing bones, /. c., periosteum and perichondrium, which are continued
between the ends of the bones over the synovial membrane as the capsules of the
joints. These capsules are not of uniform thickness, so that in them may be
recognized especially strengthened bands which are described as ligaments. This,
however, is not the only method of formation of ligaments. In some cases by
modification of, or derivations from, the tendons surrounding the joint, additional
ligamentous bands are provided to further strengthen the articulations.
In several of the movable joints the mesoderm which originally existed between
the ends of the bones does not become completely absorbed — a portion of it
persists and forms an articular disk. These disks may be intimately associated in
their development with the muscles surrounding the joint, e. g., the menisci of the
knee-joint, or with cartilaginous elements, representatives of skeletal structures,
which are vestigial in human anatomy, e. g., the articular disk of the sterno-
clavicular joint.
284
SYNDESMOLOGY
CLASSIFICATION OF JOINTS.
The articulations are divided into three classes: synarthroses or immovable,
amphiarthroses or slightly movable, and diarthroses or freely movable, joints.
Synarthroses (immovable articulations). — Synarthroses include all those articu-
lations in which the surfaces of the bones are in almost direct contact, fastened
together by intervening connective tissue or hyaline cartilage, and in which there
is no appreciable motion, as in the joints between the bones of the skull, excepting
those of the mandible. There are four varieties of synarthrosis : sutura, schindylesis,
gomphosis, and synchondrosis.
Sutura.^ — Sutura is that form of articulation where the contiguous margins of the
bones are united by a thin layer of fibrous tissue; it is met wdth only in the skull
(Fig. 296) . When the margins of the bones are connected by a series of processes,
and indentations interlocked together, the articulation is termed a true suture
(sutura vera); and of this there are three varieties: sutura dentata, serrata, and
limbosa. The margins of the bones are not in direct contact, being separated by a
thin layer of fibrous tissue, continuous externally with the pericranium, internally
with the dura mater. The sutura dentata is so called from the tooth-like form of
the projecting processes, as in the suture between the parietal bones. In the
Periosteum
Suturai ligament
Cartilage
Fig. 296.— Section across the sagittal suture.
Fig. 297.
Perichondrium
Periosteum
—Section through occipitosphenoid synchon-
drosis of an infant.
sutura serrata the edges of the bones are serrated like the teeth of a fine saw, as
between the two portions of the frontal bone. In the sutura limbosa, there is besides
the interlocking, a certain degree of bevelling of the articular surfaces, so that the
bones overlap one another, as in the suture between the parietal and frontal bones.
When the articulation is formed by roughened surfaces placed in apposition with
one another, it is termed a false suture (sutura notha), of which there are two kinds:
the sutura squamosa, formed by the overlapping of contiguous bones by broad
bevelled margins, as in the squamosal suture between the temporal and parietal,
and the sutura harmonia, where there is simple apposition of contiguous rough
surfaces, as in the articulation between the maxillae, or between the horizontal
parts of the palatine bones.
Schindylesis. — Schindylesis is that form of articulation in which a thin plate
of bone is received into a cleft or fissure formed by the separation of two lamiuEe in
another bone, as in the articulation of the rostrum of the sphenoid and perpendicular
plate of the ethmoid with the vomer, or in the reception of the latter in the fissure
between the maxillae and between the palatine bones.
Gomphosis. — Gomphosis is articulation by the insertion of a conical process into
a socket; this is not illustrated by any articulation between bones, properly so
called, but is seen in the articulations of the roots of the teeth with the alveoli
of the mandible and maxillse.
Synchondrosis. — Where the connecting medium is cartilage the joint is termed
a synchondrosis (Fig. 297). This is a temporary form of joint, for the cartilage
is converted into bone before adult life. Such joints are found between the
epiphyses and bodies of long bones, between the occipital and the sphenoid at,
and for some years after, birth, and between the petrous portion of the temporal
and the jugular process of the occipital.
CLASSIFICATION OF JOINTS
285
Ligament^ jy^iy'^X'r^fS'-.fv/^^t/i
Disc of
fibrocartilage
Articular cartilage
Amphiarthroses (slightb/ movable articulations).— In these articulations the
contiguous bony surfaces are either connected by broad flattened disks of fibro-
cartilage, of a more or less complex struc-
ture, as in the articulations between the
bodies of the vertebrae; or are united by an
interosseous ligament, as in the inferior
tibiofibular articulation. The first form is
termed a symphysis (P'ig. 298), the second
a syndesmosis.
Diarthroses {freely movable articulations).
— This class includes the greater number
of the joints in the body. In a diarthrodial joint the contiguous bony surfaces
are covered with articular cartilage, and connected by ligaments lined by synovial
membrane (Fig. 299). The joint may be divided, completely or incomjpletely,
by an articular di'sk or meniscus, the periphery of which is continuous with
the fibrous capsule while its free surfaces are covered by synovial membrane
(Fig. 300).
Fio. 298. — Diagrammatic section of a symphysis.
Articular cartilage
Synovial '
stratum \ Articular
Fibrosis I capsule
stratum .
Fig. 299. — Diagrammatic section of a diarthrodial joint.
Fig.
Synovial stratum
Articular cartilage
Articular disk
Fibrous stratum
300. — Diagrammatic section of a diarthrodial
joint, with an articular disk.
The varieties of joints in this class have been determined by the kind of motion
permitted in each. There are two varieties in which the movement is uniaxial, that
is to say, all movements take place around one axis. In one form, the ginglymus,
this axis is, practically speaking, transverse; in the other, the trochoid or pivot-
joint, it is longitudinal. There are two varieties where the movement is biaxial,
or around two horizontal axes at right angles to each other, or at any intervening
axis between the two. These are the condyloid and the saddle-joint. There is
one form where the movement is polyaxial, the enarthrosis or ball-and-socket joint;
and finally there are the arthrodia or gliding joints.
Ginglymus or Hinge-joint. — In this form the articular surfaces are moulded
to each other in such a manner as to permit motion only in one plane, forward
and backward, the extent of motion at the same time being considerable. The
direction which the distal bone takes in this motion is seldom in the same plane
as that of the axis of the proximal bone; there is usually a certain amount of devia-
tion from the straight line during flexion. The articular surfaces are connected
together by strong collateral ligaments, w^hich form their chief bond of union.
The best examples of ginglymus are the interphalangeal joints and the joint between
the humerus and ulna; the knee- and ankle-joints are less typical, as they allow
a Slight degree of rotation or of side-to-side movement in certain positions of the
limb.
Trochoid or Pivot-joint (articulatio trochoidea; rotary joint) . — "VMiere the movement
is limited to rotation, the joint is formed by a pivot-like process turning within
286 SYNDESMOLOGY
a ring, or a ring on a pivot, the ring being formed partly of bone, partly of ligament.
In the proximal radioulnar articulation, the ring is formed by the radial notch
of the ulna and the annular ligament; here, the head of the radius rotates within
the ring. In the articulation of the odontoid process of the axis with the atlas
the ring is formed in front by the anterior arch, and behind by the transverse
ligament of the atlas; here, the ring rotates around the odontoid process.
Condyloid Articulation {articulatio ellipsoidea) .■ — In this form of joint, an ovoid
articular surface, or condyle, is received into an elliptical cavity in such a manner
as to permit of flexion, extension, adduction, abduction, and circumduction, but
no axial rotation. The wrist-joint is an example of this form of articulation.
Articulation by Reciprocal Reception (articulatio sellaris; saddle-joint).- — In this
variety the opposing surfaces are reciprocally concavo-convex. The movements
are the same as in the preceding form; that is to say, flexion, extension, adduction,
abduction, and circumduction are allowed ; but no axial rotation. The best example
of this form is the carpometacarpal joint of the thumb.
Enarthrosis {hall-and-socket joints) . — Enarthrosis is a joint in which the distal
bone is capable of motion around an indefinite number of axes, which have one
common center. It is formed by the reception of a globular head into a cup-like
cavity, hence the name "ball-and-socket." Examples of this form of articulation
are found in the hip and shoulder.
Arthrodia (gliding joints) is a joint which admits of only gliding movement; it
is formed by the apposition of plane surfaces, or one slightly concave, the other
slightly convex, the amount of motion between them being limited by the ligaments
or osseous processes surrounding the articulation. It is the form present in the
joints between the articular processes of the vertebrae, the carpal joints, except
that of the capitate with the navicular and lunate, and the tarsal joints with the
exception of that between the talus and the navicular.
THE KINDS OF MOVEMENT ADMITTED IN JOINTS.
The movements admissible in joints may be divided into four kinds: gliding
and angular movements, circumduction, and rotation. These movements are often,
however, more or less combined in the various joints, so as to produce an infinite
variety, and it is seldom that only one kind of motion is found in any particular
joint.
Gliding Movement.- — Gliding movement is the simplest kind of motion that can
take place in a joint, one surface gliding or moving over another without any
angular or rotatory movement. It is common to all movable joints; but in some,
as in most of the articulations of the carpus and tarsus, it is the only motion per-
mitted. This movement is not confined to plane surfaces, but may exist between
any two contiguous surfaces, of whatever form.
Angular Movement. — Angular movement occurs only between the long bones,
and by it the angle , between the two bones is increased or diminished. It may
take place: (1) forward and backward, constituting flexion and extension; or (2)
toward and from the median plane of the body, or, in the case of the fingers or
toes, from the middle line of the hand or foot, constituting adduction and abduction.
The strictly ginglymoid or hinge-joints admit of flexion and extension only. Abduc-
tion and adduction, combined with flexion and extension, are met with in the more
movable joints; as in the hip, the shoulder, the wrist, and the carpometacarpal
joint of the thumb.
Circumduction. — Circumduction is that form of motion which takes place between
the head of a bone and its articular cavity, when the bone is made to circumscribe
a conical space; the base of the cone is described by the distal end of the bone.
ARTICULATIONS OF THE VERTEBRAL COLUMN 287
the apex is in the articular cavity; this kind of motion is best seen in the shoulder-
and hip-joints.
Rotation.— Rotation is a form of movement in which a bone moves around a
central axis without undergoing any displacement from this axis; the axis of rota-
tion may lie in a separate bone, as in the case of the 'pivot formed by the odontoid
process of the axis yertebrse around which the atlas turns; or a bone may rotate
around its own longitudinal axis, as in the rotation of the humerus at the shoulder-
joint; or the axis of rotation may not be quite parallel to the long axis of the
bone, as in the movement of the radius on the ulna during pronation and supina-
tion of the hand, where it is represented by a line connecting the center of the
head of the radius above with the center of the head of the ulna below.
Ligamentous Action of Muscles.— The movements of the different joints of a hmb are combined
by means of the long muscles passing over more than one joint. These, when relaxed and stretched
to their greatest extent, act as elastic hgaments in restraining certain movements of one joint,
except when combined with corresponding movements of the other— the latter movements being
usually in the opposite direction. Thus the shortness of the hamstring muscles prevents com-
plete flexion of the hip, unless the knee-joint is also flexed so as to bring their attachments nearer
together. The uses of this arrangement are threefold: (1) It coordinates the kinds of move-
ments which are the most habitual and necessary, and enables them to be performed with the
least expenditure of power. (2) It enables the short muscles which pass over only one joint to
act upon more than one. (3) It provides the joints with hgaments which, while they are of very
great power in resisting movements to an extent incompatible with the mechanism of the joint,
at the same time spontaneously yield when necessary.
The articulations may be grouped into those of the trunk, and those of the upper
and lower extremities.
ARTICULATIONS OF THE TRUNK.
These may be divided into the following groups, viz.:
I. Of the Vertebral Column. VI. Of the Cartilages of the Ribs with the
II. Of the Atlas with the Axis. Sternum, and with Each Other.
III. Of the Vertebral Column with VII. Of the Sternum.
the Cranium. VIII. Of the Vertebral Column with the
IV. Of the Mandible. Pelvis.
V. Of the Ribs with the Vertebra. IX. Of the Pelvis.
I. Articulations of the Vertebral Column.
The articulations of the vertebral column consist of (1) a series of amphi-
arthrodial joints between the vertebral bodies, and (2) a series of diathrodial
joints between the vertebral arches.
1. Articulations of Vertebral Bodies {intercentral ligaments). — The articulations
between the bodies of the vertebrae are amphiarthrodial joints, and the individual
vertebrae move only slightly on each other. When, however, this slight degree
of movement between the pairs of bones takes place in all the joints of the vertebral
column, the total range of movement is very considerable. The ligaments of these
articulations are the following:
The Anterior Longitudinal. The Posterior Longitudinal.
The Intervertebral Fibrocartilages.
The Anterior Longitudinal Ligament {ligamentum longitudinale anterius; anterior
common ligament) (Figs. 301, 312). — The anterior longitudinal ligament is a broad
and strong band of fibers, which extends along the anterior surfaces of the bodies
of the vertebrae, from the axis to the sacrum. It is broader below than above,
288
SYNDESMOLOGY
thicker in the thoracic than in the cervical and kimbar regions, and somewhat
thicker opposite the bodies of the vertebrae than opposite the intervertebral fibro-
cartilages. It is attached, above, to the body of the axis, where it is continuous
with the anterior atlantoaxial ligament, and extends down as far as the upper
part of the front of the sacrum. It consists of dense longitudinal fibers, which
are intimately adherent to the intervertebral fibrocartilages and the prominent
margins of the vertebrae, but not to the middle parts of the bodies. In the latter
situation the ligament is thick and serves to fill up the concavities on the anterior
surfaces, and to make the front of the vertebral column more even. It is composed
of several layers of fibers, which vary in length, but are closely interlaced with
each other. The most superficial fibers are the longest and extend between four
or five vertebrae. A second, subjacent set extends between two or three vertebrae;
while a third set, the shortest and deepest, reaches from one vertebra to the next.
At the sides of the bodies the ligament consists of a few short fibers which pass
from one vertebra to the next, separated from the concavities of the vertebral
bodies by oval apertures for the passage of vessels.
Fia. 301. — Median sagittal section of two lumbar vertebrae and their ligaments.
The Posterior Longitudinal Ligament {ligameutiim longitudinale posterius; posterior
common ligament) (Figs. 801, 302).— The posterior longitudinal ligament is situated
within the vertebral canal, and extends along the posterior surfaces of the bodies
of the vertebrae, from the body of the axis, where it is continuous with the membrana
tectoria, to the sacrum. It is broader above than below, and thicker in the thoracic
than in the cervical and lumbar regions. In the situation of the intervertebral
fibrocartilages and contiguous margins of the vertebrae, where the ligament is more
intimately adherent, it is broad, and in the thoracic and lumbar regions presents
a series of dentations with intervening concave margins ; but it is narrow and thick
over the centers of the bodies, from which it is separated by the basivertebral
veins. This ligament is composed of smooth, shining, longitudinal fibers, denser
and more compact than those of the anterior ligament, and consists of superficial
layers occupying the interval between three or four vertebrae, and deeper layers
which extend between adjacent vertebrae.
ARTICULATIONS OF THE VERTEBRAL COLUMN
289
Pedicle (cul)
Intervertebral
fibrocartilage
The Intervertebral Fibrocartilages {fihrocartilagines intervertebrales; intervertebral
disks) (Figs. ;^()1, 313) .—The intervertebral fibrocartilages are interposed between
the adjacent snrfaces of the bodies of the vertebne, from the axis to the sacrum,
and form the chief bonds of connection between the vertebrae. They vary in shape,
size, and thickness, in different parts of the vertebral column. In shape and size
they correspond with the surfaces of the bodies between which they are placed,
except in the cervical region, where they are slightly smaller from side to side than
the corresponding bodies. In thickness they vary not only in the difi'erent regions
of the column, but in different parts of the same fibrocartilage; they are thicker
in front than behind in the cervical and lumbar
regions, and thus contribute to the anterior con-
vexities of these parts of the column ; while they
are of nearly uniform thickness in the thoracic
region, the anterior concavity of this part of
the column being almost entirely owing to the
shape of the vertebral bodies. The interverte-
bral fibrocartilages constitute about one-fourth
of the length of the vertebral column, exclusive
of the first two vertebrae; but this amount is
not equally distributed between the various
bones, the cervical and lumbar portions having,
in proportion to their length, a much greater
amount than the thoracic region, with the result
that these parts possess greater pliancy and
freedom of movement. The intervertebral
fibrocartilages are adherent, by their surfaces,
to thin layers of hyaline cartilage which cover
the upper and under surfaces of the bodies of
the vertebrae; in the lower cervical vertebrae,
however, small joints lined by synovial membrane are occasionally present between
the upper surfaces of the bodies and the margins of the fibrocartilages on either
side. By their circumferences the intervertebral fibrocartilages are closely con-
nected in front to the anterior, and behind to the posterior, longitudinal liga-
ments. In the thoracic region they are joined laterally, by means of the inter-
articular ligaments, to the heads of those ribs which articulate with two vertebrae.
Fig. 302. — Posterior longitudinal ligament, in
the thoracic region.
Structure of the Intervertebral Fibrocartilages. — Each is composed, at its circumference, of
laminae of fibrous tissue and fibrocartilage, forming the annulus fibrosus; and, at its center, of
a soft, pulpy, highly elastic substance, of a yellowish color, which projects considerably above
the surrounding level when the disk is divided horizontally. This pulpy substance {nucleus
pulposus), especially well-developed in the lumbar region, is the remains of the notochord. The
laminae are arranged concentrically; the outermost consist of ordinary fibrous tissue, the others
of white fibrocartilage. The laminae are not quite vertical in their direction, those near the cir-
cumference being curved outward and closely approximated; while those nearest the center
curve in the opposite direction, and are somewhat more widely separated. The fibers of which
each lamina is composed are directed, for the most part, obliquely from above downward, the
fibers of adjacent laminae passing in opposite directions and varying in every layer; so that the
fibers of one layer are directed across those of another, Uke the hmbs of the letter X. This laminar
arrangement belongs to about the outer half of each fibrocartilage. The pulpy substance presents
no such arrangement, and consists of a fine fibrous matrix, containing angular cells united to
form a reticular structure.
The intervertebral fibrocartilages are important shock absorbers. Under pressure the highly
elastic nucleus pulposus becomes flatter and broader and pushes the more resistant fibrous laminae
outward in all directions.
2. Articulations of Vertebral Arches. — The joints between the articular pro-
cesses of the vertebrae belong to the arthrodial variety and are enveloped by
19
290
SYNDESMOLOGY
capsules lined by synovial membranes; while the laminae, spinous and transverse
processes are connected by the following ligaments:
The Ligamenta Flava.
The Supraspinal.
The Ligamentum Nuchae.
The Interspinal.
The Intertransverse.
Pedicle {cut)
The Articular Capsules (capsular articulares; capsular ligamerits) (Fig. 301).- — ■
The articular capsules are thin and loose, and are attached to the margins of the
articular processes of adjacent vertebrae. They are longer and looser in the cervical
than in the thoracic and lumbar regions.
The Ligamenta Flava {ligamenta suhflara, Fig. 303).- — The ligamenta flava connect
the laminae of adjacent vertebrae, from the axis to the first segment of the sacrum.
They are best seen from the interior of the vertebral canal; when looked at from the
outer surface they appear short, being overlapped by the laminae. Each ligament
consists of two lateral portions which commence one on either side of the roots
of the articular processes, and extend backward to the point where the laminae
meet to form the spinous process ; the posterior margins of the two portions are in
contact and to a certain extent united, slight intervals being left for the passage
of small vessels. Each consists of yellow elastic tissue, the fibers of which, almost
perpendicular in direction, are at-
tached to the anterior surface of
the lamina above, some distance
from its inferior margin, and to the
posterior surface and upper margin
of the lamina below. In the cervical
region the ligaments are thin, but
broad and long; they are thicker in
the thoracic region, and thickest in
the lumbar region. Their marked
elasticity serves to preserve the up-
right posture, and to assist the
vertebral column in resuming it
after flexion.
The Supraspinal Ligament {liga-
mentum supraspinaJe; supraspinous
ligament) (Fig. 301). — The supra-
spinal ligament is a strong fibrous
cord, which connects together the
apices of the spinous processes from
the seventh cervical vertebra to the sacrum; at the points of attachment to the
tips of the spinous processes fibrocartilage is developed in the ligament. It is
thicker and broader in the lumbar than in the thoracic region, and intimately
blended, in both situations, with the neighboring fascia. The most superficial
fibers of this ligament extend over three or four vertebrae; those more deeply
seated pass between two or three vertebrae ; while the deepest connect the spinous
processes of neighboring vertebrae. Between the spinous processes it is continuous
with the interspinal ligaments. It is continued upward to the external occipital
protuberance and median nuchal line, as the ligamentum nuchae.
The Ligamentum Nuchas. — The ligamentum nuchae is a fibrous membrane, which,
in the neck, represents the supraspinal ligaments of the lower vertebrae. It extends
from the external occipital protuberance and median nuchal line to the spinous
process of the seventh cervical vertebra. From its anterior border a fibrous lamina
is given off, which is attached to the posterior tubercle of the atlas, and to the
spinous processes of the cervical vertebrae, and forms a septum between the muscles
Lamina
FiQ. 303. — Vertebral arches of three thoracic vertebrae
viewed from the front.
ARTICULATIONS OF THE VERTEBRAL COLUMN 291
on either side of the neck. In man it is merely the rudiment of an important elastic
ligament, which, in some of the lower animals, serves to sustain the weight of the
head.
The Interspinal Ligaments {ligamenta inter syinalia; interspinous ligaments)
(Fig. 301).— The interspinal ligaments thin and membranous, connect adjoining
spinous processes and extend from the root to the apex of each process. They
meet the ligamenta flava in front and the supraspinal ligament behind. They
are narrow and elongated in the thoracic region; broader, thicker, and quadrilateral
in form in the lumbar region; and only slightly developed in the neck.
The Intertransverse Ligaments {ligamenta intertransversaria) . — The intertransverse
ligaments are interposed between the transverse processes. In the cervical region
they consist of a few irregular, scattered fibers; in the thoracic region they are
rounded cords intimately connected with the deep muscles of the back; in the
lumbar region they are thin and membranous.
Movements.— The movements permitted in the vertebral column are: flexion, extension,
lateral movement, circumduction, and rotation.
In flexion, or movement forward, the anterior longitudinal Hgament is relaxed, and the inter-
vertebral fibrocartilages are compressed in front; while the posterior longitudinal ligament, the
ligamenta flava, and the inter- and supraspinal ligaments are stretched, as well as the posterior
fibers of the intervertebral fibrocartilages. The interspaces between the laminje are widened,
and the inferior articular processes ghde upward, upon the superior articular processes of the
subjacent vertebra?. Flexion is the most extensive of all the movements of the vertebral column,
and is freest in the lumbar region.
In extension, or movement backward, an exactly opposite disposition of the parts takes place.
This movement is limited by the anterior longitudinal Ugament, and by the approximation of
the spinous processes. It is freest in the cervical region.
In lateral movement, the sides of the intervertebral fibrocartilages are compressed, the extent
of motion being Umited by the resistance offered by the surrounding hgaments. This movement
may take place in any part of the column, but is freest in the cervical and lumbar regions.
Circumduction is very limited, and is merely a succession of the preceding movements.
Rotation is produced by the twisting of the intervertebral fibrocartilages; this, although only
shght between any two vertebrae, allows of a considerable extent of movement when it takes place
in the whole length of the column, the front of the upper part of the column being turned to one
or other side. This movement occurs to a slight extent in the cervical region, is freer in the upper
part of the thoracic region, and absent in the lumbar region.
The extent and variety of the movements are influenced by the shape and direction of the
articular surfaces. In the cervical region the upward incHnation of the superior articular surfaces
allows of free flexion and extension. Extension can be carried farther than flexion; at the upper
end of the region it is checked by the locking of the posterior edges of the superior atlantal facets
in the condyloid fossae of the occipital bone; at the lower end it is limited by a mechanism whereby
the inferior articular processes of the seventh cervical vertebra slip into grooves behind and
below the superior articular processes of the first thoracic. Flexion is arrested just beyond the
point where the cervical convexity is straightened; the movement is checked by the apposition
of the projecting lower lips of the bodies of the vertebrae with the shelving surfaces on the bodies
of the subjacent vertebrae. Lateral flexion and rotation are free in the cervical region; they are,
however, always combined. The upward and medial incUnations of the superior articular surfaces
impart a rotatory movement during lateral flexion, while pure rotation is prevented by the slight
medial slope of these surfaces.
In the thoracic region, notably in its upper part, all the movements are Hmited in order to
reduce interference with respiration to a minimum. The almost complete absence of an upward
incUnation of the superior articular surfaces prohibits any marked fle.xion, while extension is
checked by the contact of the inferior articular margins with the laminae, and the contact of the
spinous processes with one another. The mechanism between the seventh cervical and the first
thoracic vertebrae, which limits extension of the cervical region, will also serve to limit flexion of
the thoracic region when the neck is extended. Rotation is free in the thoracic region: the
superior articular processes are segments of a cylinder whose axis is in the mid-ventral line of the
vertebral bodies. The direction of the articular facets would allow of free lateral flexion, but
this movement is considerably limited in the upper part of the region by the resistance of the
ribs and sternum.
In the lumbar region flexion and extension are free. Flexion can be carried farther than exten-
sion, and is possible to just beyond the straightening of the lumbar curve; it is, therefore, greatest
at the lowest part where the curve is sharpest. The inferior articular facets are not in close appo-
292
SYNDESMOLOGY
sition with the superior facets of the subjacent vertebrae, and on this account a considerable
amount of lateral flexion is permitted. For the same reason a shght amount of rotation can be
carried out, but this is so soon checked by the interlocking of the articular surfaces that it is
neghgible.
The principal muscles which produce flexion are the Sternocleidomastoideus, Longus capitis,
and Longus coUi; the Scaleni; the abdominal muscles and the Psoas major. Extension is produced
by the intrinsic muscles of the back, assisted in the neck bj- the Splenius, Semispinales dorsi and
cervicis, and the Miiltifidus. Lateral motion is produced by the intrinsic muscles of the back
by the Splenius, the Scaleni, the Quadratus lumborum, and the Psoas major, the muscles of one
side only acting; and rotation by the action of the following muscles of one side only, viz., the
Sternocleidomastoideus, the Longus capitis, the Scaleni, the Multifidus, the Semispinalis capitis,
and the abdominal muscles.
II. Articulation of the Atlas with the Epistropheus or Axis (Articulatio
Atlantoepistrophica) .
The articulation of the atlas with the axis is of a complicated nature, com-
prising no fewer than four distinct joints. There is a pivot articulation between
the odontoid process of the axis and the ring formed by the anterior arch and
the tranverse ligament of the atlas (see Fig. 306); here there are two joints: one
between the posterior surface of the anterior arch of the atlas and the front of
the odontoid process; the other between the anterior surface of the ligament and
the back of the process. Between the articular processes of the two bones there
is on either side an arthrodial or gliding joint. The ligaments connecting these
bones are:
Two Articular Capsules.
The Anterior Atlantoaxial.
The Posterior Atlantoaxial.
The Transverse.
Atlanto-
occipital C -Articular capsule
■[ and
\iiynovial membrane
Articular capsule
and
synodal membrane
Fig. 304. — Anterior atlantooccipital membrane and atlantoaxial ligament.
The Articular Capsules {capsultr articulares ; capsular ligamenfs). — The articular
capsules are thin and loose, and connect the margins of the lateral masses of the
atlas with those of the posterior articular surfaces of the axis. Each is strength-
ened at its posterior and medial part by an accessory ligament^ which is attached
ARTICULATIOX OF THE ATLAS WITH THE EPISTROPHEUS OR AXIS 293
below to the body of the axis near the base of the odontoid process, and above
to the lateral mass of the atlas near the transverse ligament.
The Anterior Atlantoaxial Ligament (Fig. 304).— This ligament is a strong mem-
brane, fixed, above, to the lower border of the anterior arch of the atlas; below,
to the front of the body of the axis. It is strengthened in the middle line bv a
Arch for passage of
vertebral artery
and first cervical
nerve
Fig. 305. — Posterior atlantooccipital membrane and atlantoaxial ligament.
rounded cord, which connects the tubercle on the anterior arch of the atlas to the
body of the axis, and is a continuation upward of the anterior longitudinal liga-
ment. The ligament is in relation, in front, with the Longi capitis.
Fig. 300. — Articulation between odontoid process and atlas.
The Posterior Atlantoaxial Ligament (Fig. 305). — This ligament is a broad, thin
membrane attached, above, to the lower border of the posterior arch of the atlas;
heloic, to the upper edges of the lamimie of the axis. It supplies the place of
the ligamenta flava, and is in relation, behind, with the Obliqui capitis inferiores.
The Transverse Ligament of the Atlas {ligamentum transversum ailantis) (Figs.
306, 307, 30S).— The transverse ligament of the atlas is a thick, strong band, which
294
SYNDESMOLOGY
Apical odontoid
ligament
Atlanta. (^'^''''^""'"P^'^'
occipital I gu^Q^iai membrane
. , . , Artindar capsule
Atlanta-} „,,^
axial y synovial membrane
Fig. 307. — Membrana tectoria, transverse, and alar ligaments.
Anterior atlanto-
occipital membrane
3Iembrana tectoriu
Crus superiws of
transverse ligament
Apical odont. lig
Ant. arch of atlas
Odontoid process
of axis
Articidar cavi
Transverse ligament
Anterior atlanto-
axial ligament
Superficial layer of membrana. tectoria
Canalis hypoglossi
Posterior atlanto-
occipital membrane
Posterior arch
of atlas
iuboccipital nerve
Intervertebral
fbrocartilage
Anterior longitudinal
ligament
Posterior longitudinal ligament
Fig. 308 —Median sagittal section through the occipital bone and first three cervical vertebrae. (Spalteholz.)
ARTICULATIONS OF THE VERTEBRAL COLUMN WITH THE CRANIUM 295
arches across the ring of the atlas, and retains the odontoid process in contact with
the anterior arch. It is concave in front, convex behind, broader and thicker in
the middle than at the ends, and firmly attached on either side to a small tubercle
on the medial surface of the lateral mass of the atlas. As it crosses the odontoid
process, a small fasciculus (cms superius) is prolonged upward, and another (cms
injerius) downward, from the superficial or posterior fibers of the ligament. The
former is attached to the basilar part of the occipital bone, in close relation with
the membrana tectoria; the latter is fixed to the posterior surface of the l)ody
of the axis; hence, the whole ligament is named the cruciate ligament of the atlas.
The transverse ligament divides the ring of the atlas into two unequal parts:
of these, the posterior and larger ser\'es for the tcansmission of the medulla spinalis
and its membranes and the accessory nerves; the anterior and smaller contains
the odontoid process. The neck of the odontoid process is constricted where it is
embraced posteriorly by the transverse ligament, so that this ligament suffices
to retain the odontoid process in position after all the other ligaments have been
divided.
Synovial Membranes. — There is a sjTiovial membrane for each of the four joints; the joint
cavity between the odontoid i)rocess and the transverse ligament is often continuous with those
of the atlantooccipital articulations.
Movements. — The opposed articular surfaces of the atlas and axis are not reciprocally curved;
both surfaces are convex in their long axes. When, therefore, the upper facet glides forward
on the lower it also descends; the fibers of the articular capsule are relaxed in a vertical direc-
tion, and will then permit of movement in an antero-posterior direction. By this means a
shorter capsule suffices and the strength of the joint is materially increased.^
This joint allows the rotation of the atlas (and, with i., the skull) upon the axis, the extent
of rotation being limited by the alar ligaments.
The principal muscles by which these movements are produced are the Sternocleidomastoideus
and Semispinalis capitis of one side, acting with the Longus capitis, Splenius, Longissimus capitis,
Rectus capitis posterior major, and ObUqui capitis superior and inferior of the other side.
III. Articulations of the Vertebral Column with the Cranium.
The ligaments connecting the vertebral column with the cranium may be
divided into two sets: those uniting the atlas with the occipital bone, and those
connecting the axis with the occipital ])one.
Articulation of the Atlas with the Occipital Bone {articulatio atlantodccipitalis) .
— The articulation between the atlas and the occipital bone consists of a pair of
condyloid joints. The ligaments connecting the bones are:
Two Articular Capsules. The Posterior Atlantooccipital
The Anterior Atlantooccipital membrane.
membrane. • Two Lateral Atlantooccipital.
The Articular Capsules (capsidop articulares; capsular ligaments). — The articular
capsules surround the condyles of the occipital bone, and connect them with the
articular processes of the atlas: they are thin and loose.
The Anterior Atlantooccipital Membrane {memhrana atlantooccipitalis anterior;
anterior atlantooccipital ligament) (Fig. 304).— The anterior atlantooccipital mem-
brane is broad and composed of densely woven fibers, which pass between the
anterior margin of the foramen magnum above, and the upper border of the
anterior arch" of the atlas below; laterally, it is continuous with the articular
capsules; in front, it is strengthened in the middle line by a strong, rounded
» Corner ("The Phvsiologv of the Atlanto-axial Joints." Journal of Anatomy and Physiology, vol xli) states that
the movements whicVl take place at these articulations are of a complex nature. The hrst part of the movement is
an eccentric or asvmmetrical one; the atlanto-axial joint of the side to which the head is moved is faxed, or practically
fixed, by the muscles of the neck, and forms the center of the movement, while the opposite atlantal facet is carried
downward and forward on the corresponding axial facet. The second part of the movement is centric and symmetrical,
the odontoid process forming the axis of the movement
296 SYNDESMOLOGY
cord, which connects the basilar part of the occipital bone to the tubercle on the
anterior arch of the atlas. This membrane is in relation in front with the Recti
capitis anteriores, hehind with the alar ligaments.
The Posterior Atlantooccipital Membrane (membrana atlantodccipitalis posterior;
posterior atlaniooccipital ligament) (Fig. 305). — The posterior atlantooccipital mem-
brane, broad but thin, is connected above, to the posterior margin of the foramen
magnum; below, to the upper border of the posterior arch of the atlas. On either
side this membrane is defective below, over the groove for the vertebral artery,
and forms with this groove an opening for the entrance of the artery and the
exit of the suboccipital nerve. The free border of the membrane, arching over
the artery and nerve, is sometimes ossified. The membrane is in relation, behind,
with the Recti capitis posteriores minores and Obliqui capitis superiores; in /ro/z^,
with the dura mater of the vertebral canal, to which it is intimately adherent.
The Lateral Ligaments. — The lateral ligaments are thickened portions of the
articular capsules, reinforced by bundles of fibrous tissue, and are directed obliquely
upward and medialward; they are attached above to the jugular processes of the
occipital bone, and below, to the bases of the transverse processes of the atlas.
Ssmovial Membranes. — There are two synovial membranes: one lining each of the articular
capsules. The joints frequently communicate with that between the posterior surface of the
odontoid process and the transverse hgament of the atlas.
Movements. — The movements permitted in this joint are (a) flexion and extension, which
give rise to the ordinary forward and backward nodding of the head, and (b) slight lateral motion
to one or other side. Flexion is produced mainly by the action of the Longi capitis and Recti
capitis anteriores; extension by the Recti capitis posteriores major and minor, the Obliquus su-
perior, the Semispinahs capitis, Splenius capitis, Sternocleidomastoideus, and upper fibers of the
Trapezius. The Recti laterales are concerned in the lateral movement, assisted bj' the Trapezius,
Splenius capitis, Semispinalis capitis, and the Sternocleidomastoideus of the same side, all acting
together.
Ligaments Connecting the Axis with the Occipital Bone. —
The INIembrana Tectoria. Two Alar. The Apical Odontoid.
The Membrana Tectoria (occipitoaxial ligament) (Figs. 307, 308). — The mem-
brana tectoria is situated within the vertebral canal. It is a broad, strong bands
which covers the odontoid process and its ligaments, and appears to be a prolon-
gation upward of the posterior longitudinal ligament of the vertebral column. It
is fixed, below, to the posterior surface of the body of the axis, and, expanding as
it ascends, is attached to the basilar groove of the occipital bone, in front of the
foramen magnum, where it blends with the cranial dura mater. Its anterior sur-
face is in relation with the transverse ligament of the atlas, and its posterior
surface with the dura mater.
The Alar Ligaments {Ugamenta alaria; odontoid ligaments) (Fig. 307).- — The alar
ligaments are strong, rounded cords, which arise one on either side of the upper
part of the odontoid process, and, passing obliquely upward and lateralward, are
inserted into the rough depressions on the medial sides of the condyles of the occipi-
tal bone. In the triangular interval between these ligaments is another fibrous
cord, the apical odontoid ligament (Fig. 308), which extends from the tip of the odon-
toid process to the anterior margin of the foramen magnum, being intimately
blended with the deep portion of the anterior atlantooccipital membrane and
superior crus of the transverse ligament of the atlas. It is regarded as a rudimentary
intervertebral fibrocartilage, and in it traces of the notochord may persist. The
alar ligaments limit rotation of the cranium and therefore receive the name of
check ligaments.
In addition to the ligaments which unite the atlas and axis to the skull,
the ligamentum nucha? (page 290) must be regarded as one of the ligaments
connecting the vertebral column with the cranium.
ARTICULATION OF THE MANDIBLE
297
IV. Articulation of the Mandible (Articulatio Mandibularis ; Temporo-
mandibular Articulation).
This is a ginglymo-arthrodial joint; the parts entering into its formation on
either side are: the anterior part of the mandibular fossa of the temporal bone
and the articular tubercle above; and the condyle of the man(Uble below. The
ligaments of the joint are the following:
The Articular Capsule. The Sphenomandibular.
The Temporomandibular. ^ The Articular Disk.
The Stylomandibular.
The Articular Capsule (capsida articularis; cajysular ligament) .—The articular
capsule is a thin, loose envelope, attached above to the circumference of the
mandibular fossa and the articular tubercle immediately in front; below, to the
neck of the condyle of the mandible.
V \
Fia. 309. — Articulation of the mandible. Lateral aspect.
The Temporomandibular Ligament (ligamentum temporomandihidare: external
lateral ligament) (Fig. ;^)09). — The temporomandibular ligament consists of two
short, narrow fasciculi, one in front of the other, attached, above, to the lateral
surface of the zygomatic arch and to the tubercle on its lower border; below,
to the lateral surface and posterior border of the neck of the mandible. It is broader
above than below, and its fibers are directed obliquely downward and backward.
It is covered by the parotid gland, and by the integument.
The Sphenomandibular Ligament {ligamentum sphenomandibulare; internal lateral
ligament) (Fig. 310). — The sphenomandibular ligament is a flat, thin band which is
attached above to the spina angularis of the sphenoid bone, and, becoming broader
as it descends, is fixed to the lingula of the mandibular foramen. Its lateral surface
is in relation, above, with the Pterygoideus externus; lower down, it is separated
from the neck of the condyle by the internal maxillary vessels; still lower, the
inferior alveolar vessels and nerve and a lobule of the parotid gland lie between
it and the ramus of the mandible. Its medial surface is in relation with the Ptery-
goideus internus.
298
SYNDESMOLOGY
The Articular Disk (discus articularis; interarticnlar fihrocartilage ; articular menis-
cus) (Fig. 311). — The articular disk is a thin, oval plate, placed between the
condyle of the mandible and the mandibular fossa. Its upper surface is concavo-
convex from before backward, to accommodate itself to the form of the man-
dibular fossa and the articular tubercle. Its under surface, in contact with the
condyle, is concave. Its circumference is connected to the articular capsule; and in
front to the tendon of the Pterygoideus externus. It is thicker at its periphery,
especially behind, than at its center. The fibers of which it is composed have a
concentric arrangement, more apparent at the circumference than at the center.
It divides the joint into two cavities, each of which is furnished with a synovial
membrane.
Fig. 310. — Articulation of the mandible. Medial aspect.
Fig.
311. — Sagittal section of the articulation of the
mandible.
The Synovial Membranes. — The synovial membranes, two in number, are placed one above,
and the other below, the articular disk. The upper one, the larger and looser of the two, is
continued from the margin of the cartilage covering the mandibular fossa and articular tubercle
on to the upper surface of the disk. The lower one passes from the under surface of the disk
to the neck of the condyle, being prolonged a little farther downward behind than in front. The
articular disk is sometimes perforated in its center, and the two cavities then communicate with
each other.
The Stylomandibular Ligament {ligamentum stylomandibular e) ; stylomaxillary
ligament (Fig. 310). — The stylomandibular ligament is a specialized band of the
cervical fascia, which extends from near the apex of the styloid process of the
temporal bone to the angle and posterior border of the ramus of the mandible,
between the Masseter and Pterygoideus internus. This ligament separates the
parotid from the submaxillary gland, and from its deep surface some fibers of the
Styloglossus take origin. Although classed among the ligaments of the temporo-
mandibular joint, it can only be considered as accessory to it.
The nerves of the temporomandibular joint are derived from the auriculotemporal and masse-
teric branches of the mandibular nerve, the arteries from the superficial temporal branch of the
external carotid.
Movements. — The movements permitted in this articulation are extensive. Thus, the mandible
may be depressed or elevated, or carried forward or backward; a slight amount of side-to-side
movement is also permitted. It must be borne in mind that there are two distinct joints in this
articulation — one between the condyle and the articular disk, and another between the disk and
the mandibular fossa. When the mouth is but slightly opened, as during ordinary conversation.
COSTOVERTEBRAL ARTICULATIONS 299
the movement is confined to the lower of the two joints. On the other hand, when the mouth
IS opened more widely, both jomts are concerned in the movement; in the lower joint the move-
ment is of a hinge-Uke character, the condyle movmg around a transverse axis on the disk, while
m the upper jomt the movement is of a gUding character, the disk, together with the condyle,
gUding forward on to the articular tubercle, around an axis which passes through the mandibular
foramma. These two movements take place simultaneously, the condyle and disk move for-
ward on the eminence, and at the same time the condyle revolves on the disk. In shutting the
mouth the reverse action takes place; the disk glides back, carrying the condyle with it, and this
at the same tune moves-back to its former position. When the mandible is carried horizontally
forward, as in protruding the lower incisor teeth in front of the upper, the movement takes place
principally m the upper joint, the disk and the condyle ghding forward on the mandibular fossa
and articular tubercle. The grinding or chewing movement is produced by one condyle, with
its disk, ghding alternately forward and backward, while the other condyle moves simultaneously
in the opposite direction; at the same time the condyle undergoes a vertical rotation on the disk.
One condyle advances and rotates, the other condyle recedes and rotates, in alternate succession.
The mandible is depressed by its own weight, assisted by the Platysma, the Digastricus, the
Mylohyoideus, and the Geniohyoideus. It is elevated by the Masseter, Pterygoideus internus,
and the anterior part of the Temporalis. It is drawn forward by the simultaneous action of the
Pterygoidei internus and externus, the superficial fibers of the Masseter and the anterior fibers
of the Temporalis; and backward by the deep fibers of the Masseter and the posterior fibers of the
Temporahs. The grinding movement is caused by the alternate action of the Pterygoidei of
either side.
V. Costovertebral Articulations (Articulationes Costovertebrales).
The articulations of the ribs with the vertebral cokimn may be divided into two
sets, one connecting the heads of the ribs with the bodies of the vertebrae, another
uniting the necks and tubercles of the ribs with the transverse processes.
1. Articulations of the Heads of the Ribs {articulationes capitulorum; costocentral
articulations) (Fig. 312). — These constitute a series of gliding or arthrodial joints,
and are formed by the articulation of the heads of the typical ribs with the facets
on the contiguous margins of the bodies of the thoracic vertebrae and with the
intervertebral fibrocartilages between them ; the first, tenth, eleventh, and twelfth
ribs each articulate with a single vertebra. The ligaments of the joints are:
The Articular Capsule. The Radiate. The Interarticular.
The Articular Capsule (capsula articularis; capsular ligament).- — The articular
capsule surrounds the joint, being composed of short, strong fibers, connecting
the head of the rib with the circumference of the articular cavitv formed bv the
intervertebral fibrocartilage and the adjacent vertebrae. It is most distinct at
the upper and lower parts of the articulation; some of its upper fibers pass through
the intervertebral foramen to the back of the intervertebral fibrocartilage, while
its posterior fibers are continuous with the ligament of the neck of the rib.
The Radiate Ligament (ligamentum capituli costw radiatum; anterior costoverte-
bral or stellate ligament). — The radiate ligament connects the anterior part of the
head of each rib with the side of the bodies of two vertebrae, and the interverte-
bral fibrocartilage between them. It consists of three flat fasciculi, which are
attached to the anterior part of the head of the rib, just beyond the articular sur-
face. The superior fasciculus ascends and is connected with the body of the verte-
bra above ; the inferior one descends to the body of the vertebra below ; the middle
one, the smallest and least distinct, is horizontal and is attached to the interver-
tebral fibrocartilage. The radiate ligament is in relation, in front, w^th the thoracic
ganglia of the sympathetic trunk, the pleura, and, on the right side, with the azygos
vein; behind, with the interarticular ligament and synovial membranes.
In the case of the first rib, this ligament is not divided into three fasciculi, but
its fibers are attached to the body of the last cervical vertebra, as well as to that
of the first thoracic. In the articulations of the heads of the tenth, eleventh, and
twelfth ribs, each of which articulates with a single vertebra, the triradiate arrange-
T
\
300
SYNDESMOLOGY
ment does not exist; but the fibers of the ligament in each case are connected to
the vertebra above, as well as to that with which the rib articulates.
The Interarticular Ligament {ligamentum capituli coster interarticulare) .■ — The in-
terarticular ligament is situated in the interior of the joint. It consists of a short
band of fibers, flattened from above downward, attached by one extremity to the
crest separating the two articular facets on the head of the rib, and by the other
to the intervertebral fibrocartilage ; it divides the joint into two cavities. In the
joints of the first, tenth, eleventh, and twelfth ribs, the interarticular ligament does
not exist; consequently, there is but one cavity in each of these articulations.
This ligament is the homologue of the ligamentum conjugale present in some
mammals, and uniting the heads of opposite ribs, across the back of the inter-
vertebral fibrocartilage.
Anterior
costotransverse
ligaments
i
Interarticular ligament Intervertebral fibrocartilage
Fig. 312. — Costovertebral articulations. Anterior view.
Synovial Membranes. — There are two synovial membranes in each of the articulations where
an interarticular ligament exists, one above and one below this structure; but only one in those
joints where there are single cavities.
2. Costotransverse Articulations {articulationes costotransversaricB) (Fig. ;U3). —
The articular portion of the tubercle of the rib forms with the articular surface
on the adjacent transverse process an arthrodial joint.
In the eleventh and twelfth ribs this articulation is wanting.
The ligaments of the joint are :
The Articular Capsule. The Posterior Costotransverse.
The Anterior Costotransverse. The Ligament of the Neck of the Rib.
The Ligament of the Tubercle of the Rib.
COSTOVERTEBRAL ARTICULATIONS
301
The Articular Capsule (capsula articularis; capsular ligament). — The articular cap-
sule is a thin membrane attached to the circumferences of the articular surfaces,
and lined by a synovial membrane.
ynovial cavity
Anterior costotransverse
ligament divided
Ligament of the neck
Ligament of the
tubercle
Articular capsule
Fia. 313. — Costotransverse articulation. Seen from above.
The Anterior Costotransverse Ligament {liga-
mentum costotransversarimn anterius; anterior
superior ligament).- — The anterior costotrans-
verse ligament is attached below to the sharp
crest on the upper border of the neck of the
rib, and passes obliquely upward and lateral-
ward to the lower border of the transverse
process immediately above. It is in relation,
in front, with the intercostal vessels and
nerves; its medial border is thickened and
free, and bounds an aperture which transmits
the posterior branches of the intercostal vessels
and nerves; its lateral border is continuous
with a thin aponeurosis, which covers the
Intercostalis externus.
The first rib has no anterior costotransverse
ligament. A band of fibers, the lumbocostal
ligament, in series with the anterior costotrans-
verse ligaments, connects the neck of the
twelfth rib to the base of the transverse pro-
cess of the first lumbar vertebra; it is merely
a thickened portion of the posterior layer of
the lumbodorsal fascia.
The Posterior Costotransverse Ligament {liga-
mentum costotransversarium, posterius). ■ — The
posterior costotransverse ligament is a feeble
band which is attached below to the neck of
the rib and passes upward and medialward to the base of the transverse process
and lateral border of the inferior articular process of the vertebra above.
Fig. 314. — Seotion of the costotransverse
joints from the third to the ninth inclusive.
Contrast the concave facets on the upper with
the flattened facets on the lower transverse
processes.
302 SYNDESMOLOGY
The Ligament of the Neck of the Rib {ligamentum colli costw; middle costotransverse
or interosseous ligament). — The ligament of the neck of the rib consists of short
but strong fibers, connecting the rough surface on the back of the neck of the rib
with the anterior surface of the adjacent transverse process. A rudimentary
Hgament may be present in the case of the eleventh and twelfth ribs.
The Ligament of the Tubercle of the Rib {ligamentum tuberculi costcp; posterior
costotransverse ligament). — The ligament of the tubercle of the rib is a short but
thick and strong fasciculus, which passes obliquely from the apex of the transverse
process to the rough non-articular portion of the tubercle of the rib. The ligaments
attached to the upper ribs ascend from the transverse processes; they are shorter
and more oblique than those attached to the inferior ribs, which descend slightly.
Movements. — The heads of the ribs are so closely connected to the bodies of the vertebrae
by the radiate and interarticular hgaments that only slight gUding movements of the articular
surfaces on one another can take place. Similarly, the strong Hgaments binding the necks and
tubercles of the ribs to the transverse processes limit the movements of the costotransverse
joints to sUght gliding, the nature of which is determined by the shape and direction of the articular
surfaces (Fig. 314). In the upper six ribs the articular surfaces on the tubercles are oval in shape
and convex from above do-«Tiward; they fit into corresponding concavities on the anterior sur-
faces of the transverse processes, so that upward and downward movements of the tubercles are
associated with rotation of the rib neck on its long a.xis. In the seventh, eighth, ninth, and tenth
ribs the articular surfaces on the tubercles are flat, and are directed obliquely downward, medial-
ward, and backward. The surfaces with which they articulate are placed on the upper margins
of the transverse processes; when, therefore, the tubercles are drawn up they are at the same
time carried backward and medialward. The two joints, costocentral and costotransverse, move
simultaneously and in the same directions, the total effect being that the neck of the rib moves
as if on a single joint, of which the costocentral and costotransverse articulations form the ends.
In the upper six ribs the neck of the rib moves but slightly upward and downward; its chief
movement is one of rotation around its own long axis, rotation backward being associated with
depression, rotation forward with elevation. In the seventh, eighth, ninth, and tenth ribs the
neck of the rib moves upward, backward, and medialward, or downward, forward, and lateral-
ward; very slight rotation accompanies these movements.
VI. Sternocostal Articulations (Articulationes Sternocostales ; Costosternal
Articulations) (Fig. 315).
The articulations of the cartilages of the true ribs with the sternum are
arthrodial joints, with the exception of the first, in which the cartilage is directly
united with the sternum, and which is, therefore, a synarthrodial articulation.
The ligaments connecting them are:
The Articular Capsules. The Interarticular Sternocostal.
The Radiate Sternocostal. The Costoxiphoid.
The Articular Capsules (capsulce articulares; capsular ligaments). — The articular
capsules surround the joints between the cartilages of the true ribs and the
sternum. They are very thin, intimately blended with the radiate sternocostal
ligaments, and strengthened at the upper and lower parts of the articulations by a
few fibers, which connect the cartilages to the side of the sternum.
The Radiate Sternocostal Ligaments (ligamenta sternocostalia radiata; chondro-
sternal or sternocostal ligaments) .■ — These ligaments consist of broad and thin mem-
branous bands that radiate from the front and back of the sternal ends of the
cartilages of the true ribs to the anterior and posterior surfaces of the sternum.
They are composed of fasciculi which pass in different directions. The superior
fasciculi ascend obliquely, the inferior fasciculi descend obliquely, and the middle
fasciculi run horizontally. The superficial fibers are the longest; they intermingle
with the fibers of the ligaments above and below them, with those of the opposite
side, and in front with the tendinous fibers of origin of the Pectoralis major, form-
STERNOCOSTAL ARTICULATIONS
303
ing a thick fibrous membrane (membrana sterni) which envelopes the sternum.
This is more distinct at tlie lower than at the upper part of the bone.
The Interarticular Sternocostal Ligament (ligamentum stcrnocostale interarticularc ;
interarticular chondr aster mil I ic/ament).— This Hgament is found constantly onlv
between the second costal cartilages and the sternum. The cartilage of the second
The synovial cavities are exposed by
a coronal section of the sternum and cartilages
Cartilage continuous with
sternum
Interarticular ligament and
two synovial rnembranes
Single synovial
membrane
FiQ. 315. — Sternocostal and interchondral articulations. Anterior view.
rib is connected with the sternum by means of an interarticular ligament, attached
by one end to the cartilage of the rib, and by the other to the fibrocartilage which
unites the manubrium and body of the sternum. This articulation is provided
with two synovial membranes. Occasionally the cartilage of the third rib is con-
nected with the first and second pieces of the body of the sternum by an interartic-
ular ligament. Still more rarely, similar ligaments are found in the other four
304 SYNDESMOLOGY
joints of the series. In the lower two the ligament sometimes completely obliterates
the cavity, so as to convert the articulation into an amphiarthrosis.
The Costoxiphoid Ligaments {ligamenta costoxiphoidea; chondroxiphoid ligaments).
— These ligaments connect the anterior and posterior surfaces of the seventh
costal cartilage, and sometimes those of the sixth, to the front and back of the
xiphoid process. They vary in length and breadth in different subjects; those on
the back of the joint are less distinct than those in front.
Synovial Membranes. — There is no s>Tiovial membrane between the first costal cartilage and
the sternum, as this cartilage is directly continuous with the manubrium. There are two in the
articulation of the second costal cartilage and generally one in each of the other joints; but those
of the sixth and seventh sternocostal joints are sometimes absent; where an interarticular liga-
ment is present, there are two synovial cavities. After middle life the articular surfaces lose their
poUsh, become roughened, and the synovial membranes apparently disappear. In old age, the
cartilages of most of the ribs become continuous with the sternum, and the joint cavities are
consequently obliterated.
Movements. — SUght gliding movements are permitted in the sternocostal articulations.
Interchondral Articulations {articulationes interchondrales; articulations of the
cartilages of the ribs with each other) (Fig. 315). — ^The contiguous borders of the sixth,
seventh, and eighth, and sometimes those of the ninth and tenth, costal cartilages
articulate with each other by small, smooth, oblong facets. Each articulation
is enclosed in a thin articular capsule, lined by synovial membrane and strengthened
laterally and medially by ligamentous fibers (interchondral ligaments) which pass
from one cartilage to the other. Sometimes the fifth costal cartilages, more rarely
the ninth and tenth, articulate by their lower borders with the adjoining cartilages
by small oval facets; more frequently the connection is by a few ligamentous fibers.
Costochondral Articulations. — The lateral end of each costal cartilage is received
into a depression in the sternal end of the rib, and the two are held together by the
periosteum.
Vn. Articulation of the Manubrium and Body of the Sternum.
The manubrium is imited to the bodv of the sternum either bv an amphiarthrodial
joint — a piece of fibrocartilage connecting the segments — or by a diarthrodial
joint, in which the articular surface of each bone is clothed with a lamina of car-
tilage. In the latter case, the cartilage covering the body is continued without
interruption on to the cartilages of the facets for the second ribs. Rivington
found the diarthrodial form of joint in about one-third of the specimens examined
by him, INIaisonneuve more frequently. It appears to be rare in childhood, and
is formed, in Rivington's opinion, from the amphiarthrodial form, by absorption.
The diarthrodial joint seems to have no tendency to ossify, while the amphiar-
throdial is more liable to do so, and has been found ossified as earlv as thirtv-four
years of age. The two segments are further connected by anterior and posterior
interstemal ligaments consisting of longitudinal fibers.
Mechanism of the Thorax. — Each rib possesses its own range and variety of movements, but
the movements of all are combined in the respiratory excursions of the thorax. Each rib may
be regarded as a lever the fulcrum of which is situated immediately outside the costotransverse
articulation, so that when the body of the rib is elevated the neck is depressed and vice versa;
from the disproportion in length of the arms of the lever a shght movement at the vertebral end
of the rib is greatly magnified at the anterior extremity.
The anterior ends of the ribs he on a lower plane than the posterior; when therefore the body
of the rib is elevated the anterior extremity is thrust also forward. Again, the middle of the body
of the rib hes in a plane below that passing through the two extremities, so that when the body
is elevated relatively to its ends it is at the same time carried outward from the median plane
of the thorax. Further, each rib forms the segment of a curve which is greater than that of the
rib immediately above, and therefore the elevation of a rib increases the transverse diameter
of the thorax in the plane to which it is raised. The modifications of the rib movements at their
vertebral ends have already been described (page 302). Further modifications result from the
ARTICULATION OF THE MANUBRIUM AND BODY OF STERNUM 305
attachments of their anterior extremities, and it is convenient therefore to consider separately
the movements of the ribs of the three groups— vertebrosternal, vertebrochondral, and vertebral.
Vertebrosternal Ribs (Figs. 316,
3 17). — The first rib differs from the
others of this group in that its at-
tachment to the sternum is a rigid
one; this is counterbalanced to some
extent by the fact that its head
possesses no interarticular hgament,
and is therefore more movable. The
first pair of ribs with the manu-
brium sterni move as a single piece,
the anterior portion being elevated
by rotatory movements at the
vertebral extremities. In normal
quiet respiration the movement of
this arc is practically 7dl; when it
does occur the anterior part is
raised and cari'ied forward, increas-
ing the antero-posterior and trans-
verse diameters of this region of the
chest. The movement of the second
rib is also slight in normal respira-
tion, as its anterior extremity is
fixed to the manubrium, and pre-
vented therefore from moving up-
ward. The sternocostal articulation,
however, allows the middle of the
body of the rib to be drawn up, and
in this way the transverse thoracic diameter is increased. Elevation of the third, fourth, fifthi
and sixth ribs raises and thrusts forward their anterior extremities, the greater part of the move-
ment being effected by the rotation of the rib neck backward. The thrust of the anterior
extremities carries forward and upward the body of the sternum, which moves on the joint
c \^V^
A
_\Vv\\
1 J'- •'
Fig. 310. — Lateral view of first and seventh ribs in position, show-
ing the movements of the sternum and ribs in A, ordinary expiration;
B, quiet inspiration; C, deep inspiration.
FiQ. 317. — Diagram showing the axes of movement
(A B and C D) oi a vertebrosternal rib. The inter-
rupted lines indicate the position of the rib in
inspiration.
Fio. 3l8. — Diagram showing the axis of movement
(A B) of a vertebrochondral rib. The interrupted Jinea
indicate the position of the rib in inspiration.
between it and the manubrium, and thus the antero-posterior thoracic diameter is increased.
This movement is, however, soon arrested, and the elevating force is then expended in raising
the middle part of the body of the rib and everting its lower border; at the same time the
20
306 SYNDESMOLOGY
costochondral angle is opened out. By these latter movements a considerable increase in the
transverse diameter of the thorax is effected.
Vertebrochondral Ribs (Fig. 318). — The seventh rib is included with this group, as it conforms
more closely to their type. While the movements of these ribs assist in enlarging the thorax
for respiratory purposes, they are also concerned in increasing the upper abdominal space for
viscera displaced by the action of the diaphragm. The costal cartilages articulate with one
another, so that each pushes up that above it, the final thrust being directed to pushing forward
and upward the lower end of the body of the sternum. The amount of elevation of the .anterior
extremities is limited on account of the very slight rotation of the rib neck. Elevation of the
shaft is accompanied b}'^ an outward and backward movement; the outward movement everts
the anterior end of the rib and opens up the subcostal angle, while the backward movement
pulls back the anterior extremity and counteracts the forward thrust due to its elevation; this
latter is most noticeable in the lower ribs, which are the shortest. The total result is a consider-
able increase in the transverse and a diminution in the median antero-posterior diameter of the
upper part of the abdomen; at the same time, however, the lateral antero-posterior diameters of
the abdomen are increased.
Vertebral Ribs. — Since these ribs have free anterior extremities and only costocentral articula-
tions with no interarticular ligaments, they are capable of sUght movements in all directions.
When the other ribs are elevated these are depressed and fixed to form points of action for the
diaphragm.
Vin. Articulation of the Vertebral Column with the Pelvis.
The ligaments connecting the fifth lumbar vertebra with the sacrum are similar
to those which join the movable segments of the vertebral column with each other
— viz.: 1. The continuation downward of the anterior and posterior longitudinal
ligaments. 2. The intervertebral fibrocartilage, connecting the body of the fifth
lumbar to that of the first sacral vertebra and forming an amphiarthrodial joint.
3. Ligamenta flava, uniting the laminae of the fifth lumbar vertebra with those
of the first sacral. 4. Capsules connecting the articular processes and forming
a double arthrodia. 5. Inter- and supraspinal ligaments.
On either side an additional ligament, the iliolumbar, connects the pelvis with
the vertebral column.
The Iliolumbar Ligament iligamentum iliolumhale) (Fig. 319). — The iliolumbar
ligament is attached above to the lower and front part of the transverse process
of the fifth lumbar vertebra. It radiates as it passes lateralward and is attached
by two main bands to the pelvis. The lower bands run to the base of the sacrum,
blending with the anterior sacroiliac ligament; the upper is attached to the crest
of the ilium immediately in front of the sacroiliac articulation, and is continuous
above with the lumbodorsal fascia. In front, it is in relation with the Psoas major;
behind, with the muscles occupying the vertebral groove; above, with the Quadratus
lumborum.
DC. Articulations of the Pelvis.
The ligaments connecting the bones of the pelvis with each other may be divided
into four groups: 1. Those connecting the sacrum and ilium. 2. Those passing
between the sacrum and ischium. 3. Those uniting the sacrum and coccyx. 4.
Those between the two pubic bones.
1. Sacroiliac Articulation (articulatio sacroiliaca). — The sacroiliac articulation
is an amphiarthrodial joint, formed between the auricular surfaces of the sacrum
and the ilium. The articular surface of each bone is covered with a thin plate
of cartilage, thicker on the sacrum than on the ilium. These cartilaginous plates
are in close contact with each other, and to a certain extent are united together
by irregular patches of softer fibrocartilage, and at their upper and posterior part
by fine interosseous fibers. In a considerable part of their extent, especially in
advanced life, they are separated by a space containing a synovia-like fluid, and
hence the joint presents the characteristics of a diarthrosis. The ligaments of the
joint are:
The Anterior Sacroiliac. The Posterior Sacroiliac.
The Interosseous.
ARTICULATION OF THE PELVIS
307
The Anterior Sacroiliac Ligament {ligamentum sacroiliacum anterius) (Fig. 319).—
The anterior sacroiliac ligament consists of numerous thin bands, which connect
the anterior surface of the lateral part of the sacrum to the margin of the auricul
surface ot the ilium and to the preauricular sulcus
ar
Anterior sacroiliac lig.
Iliolumbar ligament Lumbosacral ligament
/ Anterior longitudinal lig.
Inguinal ligament^
Sacrospinous ligament -f
Sacrotuberous ligament /
Fig. 319.- — Articulations ot pelvis. Anterior view. (Quain.)
Intcrpubic fibrocart.
The Posterior Sacroiliac Ligament (ligamentum sacroiliacum posterius) (Fig. 320).
— The posterior sacroiliac ligament is situated in a deep depression between the
sacrum and ilium behind; it is strong and forms the chief bond of union between
the bones. It consists of numerous fasciculi, which pass between the bones in
308
SYNDESMOLOGY
various directions. The upper part (short posterior sacroiliac ligament) is nearly
horizontal in direction, and passes from the first and second transverse tubercles
on the back of the sacrum to the tuberosity of the ilium. The lower part (long
posterior sacroiliac ligament) is oblique in direction; it is attached by one extremity
1
Iliolumbar ligament
Supraspinal ligament I
Short post, sacroiliac lig. \
"- -Long post, sacroiliac lig
Sacrospinous ligament
Superficial post, sacrococ
cygeal ligament
Sacrotuberous ligament
Fig. 320. — Articulations of pelvis. Posterior view. (Quain )
to the third transverse tubercle of the back of the sacrum, and by the other to the
posterior superior spine of the ilium.
The Interosseous Sacroiliac Ligament (ligamentum sacroiliacum interosseum) . — ■
This ligament lies deep to the posterior ligament, and consists of a series of short,
strong fibers connecting the tuberosities of the sacrum and ilium.
ARTICULATIONS OF THE PELVIS 309
2. Ligaments Connecting the Sacrum and Ischium (Fig. 320).
The Sacrotuberous. The Sacrospinous.
The Sacrotuberous Ligament (ligamentum sacrotuherosum; great or posterior
sacrosciatic ligament) .—lYie sacrotuberous ligament is situated at the lower and
back part of the pelvis. It is flat, and triangular in form; narrower in the middle
than at the ends; attached by its broad base to the posterior inferior spine of the
ilium, to the fourth and fifth transverse tubercles of the sacrum, and to the lower
part of the lateral margin of that bone and the coccyx. Passing obliquely downward,
forward, and lateralward, it becomes narrow and thick, but at its insertion into
the inner margin of the tuberosity of the ischium, it increases in breadth, and is
prolonged forward along the inner margin of the ramus, as the falciform process,
the free concave edge of which gives attachment to the obturator fascia; one of its
surfaces is turned toward the perineum, the other toward the Obturator internus.
The lower border of the ligament is directly continuous with the tendon of origin
of the long head of the Biceps femoris, and by many is believed to be the proximal
end of this tendon, cut off by the projection of the tuberosity of the ischium.
Relations. — The posterior surface of this ligament gives origin, by its whole extent, to the
Glutseus maximus. Its anterior surface is in part united to the sacrospinous ligament. Its upper
border forms, above, the posterior boundary of the greater sciatic foramen, and, below, the pos-
terior boundary of the lesser sciatic foramen. Its lower border forms part of the boundary of the
perineum. It is pierced by the coccygeal nerve and the coccygeal branch of the inferior gluteal
artery.
The Sacrospinous Ligament {ligamentum sacrospinosum; small or anterior sacro-
sciatic ligament). — The sacrospinous ligament is thin, and triangular in form;
it is attached by its apex to the spine of the ischium, and medially, by its broad
base, to the lateral margins of the sacrum and coccyx, in front of the sacrotuberous
ligament with which its fibers are intermingled.
Relations. — It is in relation, anteriorly, with the Coccygeus muscle, to which it is closely con-
nected; posteriorly, it is covered by the sacrotuberous ligament, and crossed by the internal
pudendal vessels and nerve. Its upper border forms the lower boimdary of the greater sciatic
foramen; its lower border, part of the margin of the lesser sciatic foramen.
These two ligaments convert the sciatic notches into foramina. The greater sciatic foramen
is bounded, in front and above, by the posterior border of the hip bone; behind, by the sacrotuberous
ligament;" and below, by the sacrospinous hgament. It is partially filled up, in the recent state,
by the Piriformis which leaves the pelvis through it. Above this muscle, the superior gluteal
vessels and nerve emerge from the pelvis; and below it, the inferior gluteal vessels and nerve,
the internal pudendal vessels and nerve, the sciatic and posterior femoral cutaneous nerves, and
the nerves to the Obturator internus and Quadratus femoris make their exit from the pelvis.
The lesser sciatic foramen is bounded, in front, by the tuberosity of the ischium; above, by the
spine of the ischium and sacrospinous ligament; behind, by the sacrotuberous hgament. It trans-
mits the tendon of the Obturator internus, its nerve, and the internal pudendal vessels and nerve.
3. Sacrococcygeal Symphysis {symphysis sacrococcygea; articulation of the sacrum
and coccyx). — This articulation is an amphiarthrodial joint, formed between the
oval surface at the apex of the sacrum, and the base of the coccyx. It is homol-
ogous with the joints between the bodies of the vertebrae, and is connected by
similar ligaments. They are:
The Anterior Sacrococcygeal. The Lateral Sacrococcygeal.
The Posterior Sacrococcygeal. The Interposed Fibrocartilage.
The Interarticular.
The Anterior Sacrococcygeal Ligament {ligamentum sacrococcygeum anterius). —
This consists of a few irregular fibers, which descend from the anterior surface
of the sacrum to the front of the coccyx, blending with the periosteum.
The Posterior Sacrococcygeal Ligament {ligamentum sacrococcygeum posterius). —
This is a flat band, which arises from the margin of the lower orifice of the sacral
310 SYNDESMOLOGY
canal, and descends to be inserted into the posterior surface of the coccyx. This
ligament completes the lower and back part of the sacral canal, and is divisible
into a short deep portion and a longer superficial part. It is in relation, behind,
with the Gluta^us maximus.
The Lateral Sacrococcygeal Ligament {ligamentum sacrococcygeum laterale; inter-
transverse ligament). — The lateral sacrococcygeal ligament exists on either side
and connects the transverse process of the coccyx to the lower lateral angle of the
sacrum; it completes the foramen for the fifth sacral nerve.
A disk of fibrocartilage is interposed between the contiguous surfaces of the
sacrum and coccyx; it differs from those between the bodies of the vertebrae in
that it is thinner, and its central part is firmer in texture. It is somewhat thicker
in front and behind than at the sides. Occasionally the coccjtc is freely movable
on the sacrum, most notably during pregnancy ; in such cases a synovial membrane
is present.
The Interarticular Ligaments are thin bands, which unite the cornua of the two
bones.
The different segments of the coccyx are connected together by the extension
downward of the anterior and posterior sacrococcygeal ligaments, thin annular
disks of fibrocartilage being interposed between the segments. In the adult male,
all the pieces become ossified together at a comparatively early period ; but in the
female, this does not commonly occur until a later period of life. At more advanced
age the joint between the sacrum and coccyx is obliterated.
Movements. — The movements which take place between the sacrum and coccyx, and between
the different pieces of the latter bone, are forward and backward; they are very limited. Their
extent increases during pregnancy.
4. The Pubic Symphysis {symphysis ossium pubis; articulation of the pubic
bones) (Fig. 321). — The articulation between the pubic bones is an amphiarthro-
dial joint, formed between the two oval articular surfaces of the bones. The
ligaments of this articulation are:
The Anterior Pubic. The Superior Pubic.
The Posterior Pubic. • The Arcuate Pubic.
The Interpubic Fibrocartilaginous Lamina.
The Anterior Pubic Ligament (Fig. 319). — The anterior pubic ligament consists
of several superimposed layers, which pass across the front of the articulation.
The superficial fibers pass obliquely from one bone to the other, decussating and
forming an interlacement with the fibers of the aponeuroses of the Obliqui externi
and the medial tendons of origin of the Recti abdominis. The deep fibers pass
transversely across the symphysis, and are blended with the fibrocartilaginous
lamina.
The Posterior Pubic Ligament. — The posterior pubic ligament consists of a few
thin, scattered fibers, which unite the two pubic bones posteriorly.
The Superior Pubic Ligament (ligamentum pubicum superius). — The superior
pubic ligament connects together the two pubic bones superiorly, extending later-
ally as far as the pubic tubercles.
The Arcuate Pubic Ligament {ligamentum arcuatum pubis; inferior pubic or
subpubic ligament). — The arcuate pubic ligament is a thick, triangular arch of
ligamentous fibers, connecting together the two pubic bones below, and forming
the upper boundary of the pubic arch. Above, it is blended with the interpubic
fibrocartilaginous lamina; laterally, it is attached to the inferior rami of the
pubic bones; below, it is free, and is separated from the fascia of the urogenital
diaphragm by an opening through which the deep dorsal vein of the penis passes
into the pelvis.
ARTICULATIONS OF THE PELVIS
311
The Interpubic Fibrocartilaginous Lamina {lamina fibrocartilaginea interpubica;
inter pubic disk). —The interpubic fibrocartilaginous lamina connects the opposed
surfaces of the pubic bones. Each of these surfaces is covered by a thin layer of
hyaline cartilage firmly joined to the bone by a series of nipple-like processes which
accurately fit into corresponding depressions on the osseous surfaces. These
opposed cartilaginous surfaces are connected together by an intermediate lamina
of fibrocartilage which varies in thickness in different subjects. It often contains
a cavity in its interior, probably formed by the softening and absorption of the
fibrocartilage, since it rarely appears before the tenth year of life and is not lined
by synovial membrane. This cavity is larger in the female than in the male, but
it is very doubtful whether it enlarges, as was formerly supposed, during pregnancy.
It is most frequently limited to the upper and back part of the joint; it occasion-
ally reaches to the front, and may extend the entire length of the cartilage. It may
be easily demonstrated when present by making a coronal section of the symphysis
pubis near its posterior surface (Fig. 321).
Ant. sup. iliac spine-
Obturator canal
Lacunar ligament
Pubic tubercle \
Interpubic
fibro- _.
cartilagiiioiis
lamina
ansverse acetabular
ligament
Fig. 321. — Symphysis pubis exposed by a coronal section.
Mechanism of the Pelvis. — The pelvic girdle supports and protects the contained viscera and
affords surfaces for the attachments of the trunk and lower limb muscles. Its most important
mechanical function, however, is to transmit the weight of the trunk and upper limbs to the
lower extremities.
It may be divided into two arches by a vertical plane passing through the acetabular cavities;
the posterior of these arches is the one chiefly concerned in the fimction of transmitting the
weight. Its essential parts are the upper three sacral vertebrae and two strong pillars of bone
running from the sacroihac articulations to the acetabular cavities. For the reception and diffu-
sion of the weight each acetabular cavity is strengthened by two additional bars running toward
the pubis and ischium. In order to lessen concussion in rapid changes of distribution of the
weight, joints (sacroiliac articulations) are interposed between the sacrum and the ihac bones;
an accessory joint (pubic symphysis) exists in the middle of the anterior arch. The sacrum forms
the summit of the posterior arch; the weight transmitted faUs on it at the lumbosacral articula-
tion and, theoretically, has a component in each of two directions. One component of the force
is expended in driving the sacrum downward and backward between the ihac bones, while the
other thrusts the upper end of the sacrum downward and forward toward the pelvic cavity.
312
SYXDESMOLOGY
The movements of the sacrum are regulated by its form. Viewed as a whole, it presents the
shape of a wedge with its base upward and forward. The first component of the force is there-
Fig. 322. — Coronal section of anterior sacral segment.
fore acting against the resistance of the wedge, and its tendency to separate the iUac bones is
resisted by the sacroiliac and iliolumbar ligaments and by the ligaments of the pubic sj'mphysis.
Fia. 323. — Coronal section of middle sacra segment
If a series of coronal sections of the sacroiliac joints be made, it will be found possible to cfivide
the articular portion of the sacrum into three segments: anterior, middle, and posterior. In
the anterior segment (Fig. 322), which involves the first sacral vertebra, the articular surfaces
show slight sinuosities and are almost parallel
to one another; the distance between their
dorsal margins is, however, slightly greater
than that between their ventral marginsr-
This segment therefore presents a sUght
wedge shape with the truncated apex down-
ward. The middle segment (Fig. 323) is a
narrowband across the centers of the articu-
lations. Its dorsal width is distinctly
greater than its ventral, so that the segment
is more definitely wedge-shaped, the trun-
cated apex being again directed downward.
Each articular surface presents in the center
a marked concavity from above downward,
and into this a corresponding convexity of the ihac articular surface fits, forming an interlocking
mechanism. In the posterior segment (Fig. 324) the ventral width is greater than the dorsal,
so that the wedge form is the reverse of those of the other segments — i. e., the truncated apex
is directed upward. The articular surfaces are only shghtly concave.
Dislocation downward and forward of the sacrum by the second component of the force applied
to it is prevented therefore by the middle segment, which interposes the resistance of its wedge
Fig. 324. — Coronal section of posterior sacral segment.
STERNOCLAVICULAR ARTICULATION 313
shape and that of the interlocking mechanism on its surfaces; a rotatory movement, however,
is produced by which the anterior segment is tilted downward and the posterior upward; the axis
of this rotation passes through the dorsal part of the middle segment. The movement of the
anterior segment is slightly limited by its wedge form, but chiefly by the posterior and inter-
osseous sacroiliac ligaments; that of the posterior segment is checked to a slight extent by its
wedge form, but the chief limiting factors are the sacrotuberous and sacrospinous ligaments.
In all these movements the efifect of the sacroiliac and iholumbar ligaments and the ligaments
of the symphysis pubis in resisting the separation of the ihac bones must be recognized.
During pregnancy the pelvic joints and hgaments are relaxed, and capable therefore of more
extensive movements. When the fetus is being expelled the force is applied to the front of the
sacrum. Upward dislocation is again prevented by the interlocking mechanism of the middle
segment. As the fetal head passes the anterior segment the latter is carried upward, enlarging
the antero-posterior diameter of the pelvic inlet; when the head reaches the posterior segment
this also is pressed upward against the resistance of its wedge, the movement only being possible
by the laxity of the joints and the stretching of the sacrotuberous and sacrospinous ligaments.
ARTICULATIONS OF THE UPPER EXTREMITY.
The articulations of the Upper Extremity may be arranged as follows:
I. Sternoclavicular. VI. Wrist.
II. Acromioclavicular. VII. Intercarpal.
III, Shoulder. VIII. Carpometacarpal.
IV. Elbow. IX. Intermetacarpal.
V. Radioulnar. X. INIetacarpophalangeal.
XL Articulations of the Digits.
I. Sternoclavicular Articulation (Articulatio Sternoclavicularis) (Fig. 325).
The sternoclavicular articulation is a double arthrodial joint. The parts entering
into its formation are the sternal end of the clavicle, the upper and lateral part
of the manubrium sterni, and the cartilage of the first rib. The articular surface
of the clavicle is much larger than that of the sternum, and is invested with a layer
of cartilage,^ which is considerably thicker than that on the latter bone. The
ligaments of this joint are:
The Articular Capsule. The Interclavicular.
The Anterior Sternoclavicular. The Costoclavicular.
The Posterior Sternoclavicular. The Articular Disk.
The Articular Capsule (capsula articiilaris; capsular ligament). — The articular
capsule surrounds the articulation and varies in thickness and strength. In front
and behind it is of considerable thickness, and forms the anterior and posterior
sternoclavicular ligaments; but above, and especially below, it is thin and par-
takes more of the character of areolar than of true fibrous tissue.
The Anterior Sternoclavicular Ligament {ligamentum sternoclavicular e anterior). —
The anterior sternoclavicular ligament is a broad band of fibers, covering the
anterior surface of the articulation; it is attached above to the upper and front part
of the sternal end of the clavicle, and, passing obliquely downward and medialward,
is attached below to the front of the upper part of the manubrium sterni. This
ligament is covered by the sternal portion of the Sternocleidomastoideus and the
integument; behind, it is in relation with the capsule, the articular disk, and the
two synovial membranes.
The Posterior Sternoclavicular Ligament {ligamentum sternoclaviculare posterius) . —
The posterior sternoclavicular ligament is a similar band of fibers, covering the
posterior surface of the articulation ; it is attached above to the upper and back
' According to Bruch, the sternal end of the clavicle is covered by a tissue which is fibrous rather than cartilaginous
in structure.
314
SYNDESMOLOGY
part of the sternal end of the clavicle, and, passing obliquely downward and
medialward, is fixed below to the back of the upper part of the manubrium sterni.
It is in relation, in fro7it, wuth the articular disk and synovial membranes; behind,
with the Sternohyoideus and Sternothyreoideus.
The Interclavicular Ligament (ligamentum interclaviculare) .■ — This ligament is a
flattened band, which varies considerably in form and size in different individuals,
it passes in a curved direction from the upper part of the sternal end of one clavicle
to that of the other, and is also attached to the upper margin of the sternum. It
is in relation, in front, with, the integurtient and Sternocleidomastoidei ; behind,
with the Sternothyreoidei.
The Costoclavicular Ligament {ligamentum costoclavicular e; rhomboid ligament). —
This ligament is short, fiat, strong, and rhomboid in form. Attached below to
the upper and medial part of the cartilage of the first rib, it ascends obliquely
backward and lateralward, and is fixed above to the costal tuberosity on the under
surface of the clavicle. It is in relation, in front, with the tendon of origin of the
Subclavius; behind, with the subclavian vein.
Fig. 325. ^Sternoclavicular articulation. An terior view.
The Articular Disk {discus articularis) . — The articular disk is flat and nearly
circular, interposed between the articulating surfaces of the sternum and clavicle.
It is attached, above, to the upper and posterior border of the articular surface of
the clavicle ; beloiv, to the cartilage of the first rib, near its junction with the sternum ;
and by its circumference to the interclavicular and anterior and posterior sterno-
clavicular ligaments. It is thicker at the circumference, especially its upper and
back part, than at its center. It divides the joint into two cavities, each of which
is furnished with a synovial membrane.
Synovial Membranes. — Of the two synovial membranes found in this articulation, the lateral
is reflected from the sternal end of the clavicle, over the adjacent surface of the articular disk,
and around the margin of the facet on the cartilage of the first rib; the medial is attached to the
margin of the articular surface of the sternum and clothes the adjacent surface of the articular
disk ; the latter is the larger of the two.
Movements. — This articulation admits of a limited amount of motion in nearly every direc-
tion— upward, downward, backward, forward, as well as circumduction. When these move-
ments take place in the joint, the clavicle in its motion carries the scapula with it, this bone
gliding on the outer surface of the chest. This joint therefore forms the center from which all
movements of the supporting arch of the shoulder originate, and is the only point of articulation
of the shoulder girdle with the trunk. The movements attendant on elevation and depression of
the shoulder take place between the clavicle and the articular disk, the bone rotating upon the
ligament on an axis drawn from before backward through its own articular facet; when the shoulder
is moved forward and backward, the clavicle, with the articular disk rolls to and fro on the
ACROMIOCLAVICULAR ARTICULATION 315
articular surface of the sternum, revolving, with a shding movement, around an axis drawn nearly
vertically through the sternum; in the circumduction of the shoulder, which is compounded of
these two movements, the clavicle revolves upon the articular disk and the latter, with the clavicle,
rolls upon the sternum.* Elevation of the shoulder is hmited principally by the costoclavicular
ligament; depression, by the interclavicular hgament and articular disk. The muscles which
raise the shoulder are the upper fibers of the Trapezius, the Levator scapula, and the clavicular
head of the Sternocleidomastoideus, assisted to a certain extent by the lihomboidci, which pull
the vertebral border of the scapula backward and upward and so raise the shoulder. The depres-
sion of the shoulder is principally effected by gravity assisted by the Subclavius, Pectoralis minor
and lower fibers of the Trapezius. The shoulder is drawn backward by the Rhomboidei and the
middle and lower fibers of the Trapezius, and forward by the Serratus anterior and Pectoralis
minor.
II. Acromioclavicular Articulation (Articulatio Acromioclavicularis ; Scapulo-
clavicular Articulation) (Fig. 326).
The acromioclavicular articulation, is an arthrodial joint between the acromial
end of the clavicle and the medial margin of the acromion of the scapula. Its
ligaments are:
The Articular Capsule. The Articular Disk.
The Superior Acromioclavicular. m. /-^ i • i (Trapezoid and
The Inferior Acromioclavicular. ^he Coracoclavicular \ ^^^^jj
The Articular Capsule {cajjsula articularis; capsular ligament). — The articular
capsule completely surrounds the articular margins, and is strengthened above
and below by the superior and inferior acromioclavicular ligaments.
The Superior Acromioclavicular Ligament (ligamentuni acromioclaviculare) . —
This ligament is a quadrilateral band, covering the superior part of the articula-
tion, and extending between the upper part of the acromial end of the clavicle
and the adjoining part of the upper surface of the acromion. It is composed
of parallel fibers, which interlace with the aponeuroses of the Trapezius and
Deltoideus; helow, it is in contact M'ith the articular disk when this is present.
The Inferior Acromioclavicular Ligament. — This ligament is somewhat thinner
than the preceding; it covers the under part of the articulation, and is attached to
the adjoining surfaces of the two bones. It is in relation, above, in rare cases with
the articular disk; below, with the tendon of the Supraspinatus.
The Articular Disk (discus articularis). — The articular disk is frequently absent
in this articulation. When present, it generally only partially separates the artic-
ular surfaces, and occupies the upper part of the articulation. More rarely, it
completely divides the joint into two cavities.
The Synovial Membrane. — There is usually only one synovial membrane in this articulation,
but when a complete articular disk is present, there are two.
The Coracoclavicular Ligament {ligamentuni coracoclaviculare) (Fig. 326). — This
ligament serves to connect the clavicle with the coracoid process of the scapula.
It does not properly belong to this articulation, but is usually described with it,
since it forms a most efficient means of retaining the clavicle in contact with the
acromion. It consists of two fasciculi, called the trapezoid and conoid ligaments.
The Trapezoid Ligament iligamentum trapezoideum) , the anterior and lateral fas-
ciculus, is broad, thin, and quadrilateral: it is placed obliquely between the cora-
coid process and the clavicle. It is attached, below, to the upper surface of the
coracoid process; above, to the oblique ridge on the under surface of the clavicle.
Its anterior border is free; its posterior border is joined with the conoid ligament,
t'he two forming, by their junction, an angle projecting backward.
The Conoid Ligament (ligamentum conoideum), the posterior and medial fasciculus,
is a dense band of fibers, conical in form, with its base directed upward. It is
1 Humphry, On the Human Skeleton, page 402.
316
SYNDESMOLOGY
attached by its apex to a rough impression at the base of the coracoid process,
medial to the trapezoid Hgament; above, by its expanded base, to the coracoid
tuberosity on the under surface of the clavicle, and to a line proceeding medial-
ward from it for 1.25 cm. These ligaments are in relation, in front, with the
Subclavius and Deltoideus; behind, with the Trapezius.
Fio. 326. — The left shoulder and acromioclavicular joints, and the proper ligaments of the scapula.
Movements. — ^The movements of this articulation are of two kinds: (1) a gliding motion of
the articular end of the clavicle on the acromion; (2) rotation of the scapula forward and back-
ward upon the clavicle. The extent of this rotation is limited by the two portions of the coraco-
clavicular hgament, the trapezoid limiting rotation forward, and the^ conoid backward.
The acromioclavicular joint has important functions in the movements of the upper extremity.
It has been well pointed out by Humphry, that if there had been no joint between the clavicle
and scapula, the circular movement of the scapula on the ribs (as in throwing the shoulders back-
ward or forward) would have been attended with a greater alteration in the direction of the
shoulder than is consistent with the free use of the arm in such positions, and it would have been
impossible to give a blow straight forward with the full force of the arm; that is to say, with the
combined force cf the scapula, arm, and forearm. "This joint," as he happily says, "is so adjusted
as to enable either bone to turn in a hinge-hke manner upon a vertical axis drawn through the
other, and it permits the surfaces of the scapula, like the baskets in a roundabout swing, to look
the same way in every position, or nearly so." Again, when the whole arch formed by the clavicle
and scapula rises and falls (in elevation or depression of the shoulder), the joint between these
two bones enables the scapula still to maintain its lower part in contact with the ribs.
THE LIGAMENTS OF THE SCAPULA.
The ligaments of the scapula (Fig. 32G) are:
Coracoacromial, Superior and Inferior Transverse.
The Coracoacromial Ligament {ligamentum coracoacromiale) .■ — This ligament is a
strong triangular band, extending between the coracoid process and the acromion.
HUMERAL ARTICULATION OR SHOULDER-JOINT 317
It is attached, by its apex, to the summit of the acromion just in front of the
articular surface for the clavicle; and by its broad base to the whole length of the
lateral border of the coracoid process. This ligament, together with the coracoid
process and the acromion, forms a vault for the protection of the head of the
humerus. It is in relation, above, with the clavicle and under surface of the Del-
toideus; hehw, with the tendon of the Supraspinatus, a bursa being interposed.
Its lateral border is continuous with a dense lamina that passes beneath the Del-
toideus upon the tendons of the Supraspinatus and Infraspinatus. The ligament
is sometimes described as consisting of two marginal bands and a thinner inter-
vening portion, the two bands being attached respectively to the apex and the
base of the coracoid process, and joining together at the acromion. When the
Pectoralis minor is inserted, as occasionally is the case, into the capsule of the
shoulder-joint instead of into the coracoid process, it passes between these two
bands, and the intervening portion of the ligament is then deficient.
The Superior Transverse Ligament {ligamentum transversum scapulcp superius;
transverse or suprascapular ligament) .—This ligament converts the scapular notch
into a foramen. It is a thin and flat fasciculus, narrower at the middle than at the
extremities, attached by one end to the base of the coracoid process, and by the
other to the medial end of the scapular notch. The suprascapular nerve runs
through the foramen; the transverse scapular vessels cross over the ligament.
The ligament is sometimes ossified.
The Inferior Transverse Ligament (ligamentum transversum scapula' inferius;
spinoglenoid ligament). — This ligament is a weak membranous band, situated
behind the neck of the scapula and stretching from the lateral border of the spine
to the margin of the glenoid cavity. It forms an arch under which the transverse
scapular vessels and suprascapular nerve enter the infraspinatous fossa.
III. Humeral Articulation or Shoulder- joint (Articulatio Humeri) (Fig. 326).
The shoulder-joint is an enarthrodial or ball-and-socket joint. The bones
entering into its formation are the hemispherical head of the humerus and the
shallow glenoid cavity of the scapula, an arrangement which permits of very
considerable movement, while the joint itself is protected against displacement
by the tendons which surround it. The ligaments do not maintain the joint sur-
faces in apposition, because when they alone remain the humerus can be separated
to a considerable extent from the glenoid cavity; their use, therefore, is to limit
the amount of movement. The joint is protected above by an arch, formed by
the coracoid process, the acromion, and the coracoacromial ligament. The artic-
ular cartilage on the head of the humerus is thicker at the center than at the cir-
cumference, the reverse being the case with the articular cartilage of the glenoid
cavity. The ligaments of the shoulder are:
The Articular Capsule. The Glenohumeral.
The Coracohumeral. The Transverse Humeral.
The Glenoidal Labrum.^
The Articular Capsule {capsula articularis; capsular ligament) (Fig. 327) .^The
articular capsule completely encircles the joint, being attached, above, to the
circumference of the glenoid cavity beyond the glenoidal labrum; below, to the
anatomical neck of the humerus, approaching nearer to the articular cartilage
above than in the rest of its extent. It is thicker above and below than elsewhere,
and is so remarkably loose and lax, that it has no action in keeping the bones in
contact, but allows them to be separated from each other more than 2.5 cm., an
' The long tendon of origin of the biceps brachii also acts as one of the hgaments of this joint. See the observations
on page 287, on the function of the muscles passing over more than one joint.
318'
SYNDESMOLOGY
evident provision for that extreme freedom of movement which is peculiar to this
articulation. It is strengthened, above, by the Supraspinatus; beloic, by the long
head of the Triceps brachii; behind, by the tendons of the Infraspinatus and Teres
minor; and in front, by the tendon of the Subscapularis. There are usually three
openings in the capsule. One anteriorly, below the coracoid process, establishes
a communication between the joint and a bursa beneath the tendon of the Sub-
scapularis. The second, which is not constant, is at the posterior part, where an
opening sometimes exists between the joint and a bursal sac under the tendon
of the Infraspinatus. The third is between the tubercles of the humerus, for the
passage of the long tendon of the Biceps brachii.
The Coracohumeral Ligament {ligamentum coracohumerale) .- — This ligament is
a broad band which strengthens the upper part of the capsule. It arises from
the lateral border of the coracoid process, and passes obliquely downward and
lateralward to the front of the greater tubercle of the humerus, blending with the
Superior transverse ligament
Transverse
humeral
ligament
Prolongation of
synovial mem-
brane on tendon
of Biceps brachii
Bursa
U)ider
Subscapularis
Fig. 327. — Capsule of shoulder-joint (distended), .\nterior aspect.
tendon of the Supraspinatus. This ligament is intimately united to the capsule
by its hinder and lower border; but its anterior and upper border presents a free
edge, which overlaps the capsule.
Glenohumeral Ligaments, — In addition to the coracohumeral ligament, three
supplemental l)ands, which are named the glenohumeral ligaments, strengthen
the capsule. These may be best seen by opening the capsule at the back of the
joint and removing the head of the humerus. One on the medial side of the joint
passes from the medial edge of the glenoid cavity to the lower part of the lesser
tubercle of the humerus. A second at the lower part of the* joint extends from
the under edge of the glenoid cavity to the under part of the anatomical neck of
the humerus. A third at the upper part of the joint is fixed above to the apex
of the glenoid cavity close to the root of the coracoid process, and passing down-
ward along the medial edge of the tendon of the Biceps brachii, is attached below
to a small depression above the lesser tubercle of the humerus. In addition to
HUMERAL ARTICULATION OR SHOULDER-JOINT
319
CONOID LIGAMENT
RACOID
OCESS
these, the capsule is strengthened in front by two bands derived from the tendons
of the Pectoralis major and Teres major respectively.
The Transverse Humeral Ligament (Fig. 327) is a broad band passing from the
lesser to the greater tubercle of the humerus, and always limited to that portion
of the bone which lies above the epiphysial line. It converts the intertubercular
groove into a canal, and is the homologue of the strong process of bone which
connects the summits of the two tubercles in the musk ox.
The Glenoidal Labrum {labrium glenoidale: glenoid ligavient) is a fibrocartihaginous
rim attached around the margin of the glenoid cavity. It is triangular on section,
the base being fixed to the circumference of the cavity, while the free edge is thin
and sharp. It is continuous above with the tendon of the long head of the Biceps
brachii, which gives off two fasciculi to blend with the fibrous tissue of the labrum.
It deepens the articular cavity, and protects the edges of the bone.
Synovial Membrane. — The synovial membrane is reflected from the margin of the glenoid
cavity over the labrum; it is then reflected over the inner surface of the capsule, and covers
the lower part and sides of the anatomical neck of the
humerus as far as the articular cartilage on the head of
the bone. The tendon of the long head of the Biceps
brachii passes through the capsule and is enclosed in a
tubular sheath of synovial membrane, which is reflected
upon it from the summit of the glenoid cavity and is
continued around the tendon into the intertubercular
groove as far as the surgical neck of the humerus (Fig.
327). The tendon thus traverses the articulation, but it
is not contained within the synovial cavity.
Bursse. — The bursa3 in the neighborhood of the
shoulder-joint are the following: (1) A constant bursa
is situated between the tendon of the Subscapularis
muscle and the capsule; it communicates with the
synovial cavity through an opening in the front of the
capsule; (2) a bursa which occasionally communicates
with the joint is sometimes found between the tendon
of the Infraspinatus and the capsule; (3) a large bursa
exists between the under surface of the Deltoideus and
the capsule, but does not communicate with the joint;
thi.« bursa is prolonged under the acromion and coraco-
acromial ligament, and intervenes between these structures and the capsule; (4) a large bursa
is situated on the summit of the acromion; (5) a bursa is frequently found between the cora-
coid process and the capsule; (6) a bursa exists beneath the Coracobrachialis; (7) one lies
between the Teres major and the long head of the Triceps brachii; (8) one is placed in front of,
and another behind, the tendon of the Latissimus dorsi.
The muscles in relation with the joint are, above, the Supraspinatus; below, the long head of
the Triceps brachii; in front, the Subscapularis; behind, the Infraspinatus and Teres minor; luithin,
the tendon of the long head of the Biceps brachii. The Deltoideus covers the articulation in
front, behind, and laterally.
The arteries supplying the joint are articular branches of the anterior and posterior humeral
circumflex, and transverse scapular.
The nerves are derived from the axillary and suprascapular.
Movements. — The shoulder-joint is capable of every variety of movement, flexion, extension,
abduction, adduction, circumduction, and rotation. The humerus is flexed (drawn forward)
by the Pectorahs major, anterior fibers of the Deltoideus, Coracobrachialis, and when the fore-
arm is flexed, by the Biceps brachii; extended (drawn backward) by the Latissimus dorsi, Teres
major, posterior fibers of the Deltoideus, and, when the forearm is extended, by the Triceps
brachii; it is abducted by the Deltoideus and Supraspinatus; it is adducted by the Subscapularis,
Pectorahs major, Latissimus dorsi, and Teres major, and by the weight of the hmb; it is rotated
outward by the Infraspinatus and Teres minor; and it is rotated inward by the SuKscapularis,
Latissimus dorsi. Teres major, Pectorahs major, and the anterior fibers of the Deltoideus.
The most striking pecuharities in this joint are: (1) The large size of the head of the humerus
in comparison with the depth of the glenoid cavity, even when this latter is supplemented by the
glenoidal labrum. (2) The looseness of the capsule of the joint. (3) The intimate connection of
the capsule with the muscles attached to the head of the humerus. (4) The pecuhar relation of
the tendon of the long head of the Biceps brachii to the joint.
Fig. 328. — Glenoid fossa of right side.
320 SYNDESMOLOGY
It is in consequence of the relative sizes of the two articular surfaces, and the looseness of
the articular capsule, that the joint enjoys such free movement in all directions. When these
movements of the arm are arrested in the shoulder-joint by the contact of the bony surfaces,
and by the tension of the fibers of the capsule, together with that of the muscles acting as accessory
ligaments, the arm can be carried considc-ably farther by the movements of the scapula, involv-
ing, of coui'se, motion at the acromio- and sternoclavicular joints. These joints are therefore
to be regarded as accessory structures to the shoulder-joint (see pages 314 and 316). The extent
of the scapular movements is very considerable, especially in extreme elevation of the arm, a
movement best accomplished when the arm is thrown somewhat forward and outward, because
the margin of the head of the humerus is by no means a true circle; its greatest diameter is from
the intertubercular groove, downward, medialward, and backward, and the greatest elevation
of the arm can be obtained by rolling its articular surface in the direction of this measurement.
The great width of the central portion of the humeral head also allows of very free horizontal
movement when the arm is raised to a right angle, in which movement the arch formed by the
acromion, the coracoid process and the coracoacromial ligament, constitutes a sort of supple-
mental articular cavity for the head of the bone.
The looseness of the capsule is so great that the arm will fall about 2.5 cm. from the scapula
when the muscles are dissected from the capsule, and an opening made in it to counteract the
atmospheric pressure. The movements of the joint, therefore, are not regulated by the capsule
so much as by the surrounding muscles and by the pressure of the atmosphere, an arrangement
which "renders the jnovements of the joint much more easy than they would otherwise have
been, and permits a swinging, pendulum-Uke vibration of the limb when the muscles are at rest"
(Humphry). The fact, also, that in all ordinary positions of the joint the capsule is not put on
the stretch, enables the arm to move freely in all directions. Extreme movements are checked
by the tension of appropriate portions of the capsule, as well as by the interlocking of the bones.
Thus it is said that "abduction is checked by the contact of the great tuberosity with the upper
edge of the glenoid cavity; adduction by the tension of the coracohumeral ligament" (Beaunis
et Bouchard). Cleland' maintains that the limitations of movement at the shoulder-joint are
due to the structure of the joint itself, the glenoidal labrum fitting, in different positions of the
elevated arm, into the anatomical neck of the humerus.
The scapula is capable of being moved upward and downward, forward and backward, or, by
a combination of these movements, circumducted on the wall of the chest. The muscles which
raise the scapula are the upper fibers of the Trapezius, the Levator scapula-, and the Rhomboidei;
those which depress it are the lower fibers of the Trapezius, the Pectoralis minor, and, through
the clavicle, the Subclavius. The scapula is drawn backward by the Rhomboidei and the middle
and lower fibers of the Trapezius, and forward by the Serratus anterior and Pectoralis minor,
assisted, when the arm is fixed, by the Pectoralis major. The mobility of the scapula is very
considerable, and greatly assists the movements of the arm at the shoulder-joint. Thus, in
raising the arm from the side, the Deltoideus and Supraspinatus can only lift it to a right angle
with the trunk, the further elevation of the limb being effected by the Trapezius and Serratus
anterior moving the scapula on the wall of the chest. This mobihty is of special importance in
ankylosis of the shoulder-joint, the movements of this bone compensating to a very great extent
for the immobility of the joint.
Cathcart- has pointed out that in abducting the arm and raising it above the head, the scapula
rotates throughout the whole movement with the exception of a short space at the beginning
and at the end; that the humerus moves on the scapula not only while passing from the hanging
to the horizontal position, but also in travelling upward as it approaches the vertical above;
that the clavicle moves not only during the second half of the movement but in the first as well,
though to a less extent — i. e., the scapula and clavicle are concerned in the first stage as well
as in the second; and that the humerus is partly involved in the second as well as chiefly in the
first.
The intimate union of the tendons of the Supraspinatus, Infraspinatus, Teres minor and
Subscapularis with the capsule, converts these muscles into elastic and spontaneously acting
ligaments of the joint.
The peculiar relations of the tendon of the long head of the Biceps brachii to the shoulder-
joint appear to subserve various purposes. In the first place, by its connection with both the
shoulder and elbow the muscle harmonizes the action of the two joints, and acts as an elastic
ligament in all positions, in the manner previously discussed (see page 287). It strengthens the
upper part of the articular cavity, and prevents the head of the humerus from being pressed up
against the acromion, when the Deltoideus contracts; it thus fixes the head of the humerus as
the center of motion in the glenoid cavity. By its passage along the intertubercular groove it
assists in steadying the head of the humerus in the various movements of the arm. When the
arm is raised from the side it assists the Supraspinatus and Infraspinatus in rotating the head
of the humerus in the glenoid cavity. It also holds the head of the bone firmly in contact with
the glenoid cavity, and prevents its slipping over its lower edge, or being displaced by the action
of the Latissimus dorsi and Pectoralis major, as in climbing and many other movements.
' Journal of Anatomy and Physiology, 1S67, i, 85. ^Ibid., 1SS4, vol. xviii.
ELBOW-JOINT
321
IV.
Elbow-joint (Articulatio Cubiti) (Pigs.
329, 330).
The elbow-joint is a ginglymus or hinge-joint. The trochlea of the humerus is
received into the semilunar notch of the ulna, and the capitulum of the humerus
articulates with the fovea on the head of the radius. The articular surfaces are
connected together by a capsule, which is thickened medially and laterally, and,
to a less extent, in front and behind. These thickened portions are usually described
as distinct ligaments under the following names :
The Anterior. The Ulnar Collateral.
The Posterior. The Radial Collateral.
FiQ. 329. — Left elbow-joint, showing anterior and
ulnar collateral ligaments.
FiQ. 330. — Left elbow-joint, showing posterior and
radial collateral ligaments.
The Anterior Ligament (Fig. 329).- — The anterior ligament is a broad and thin
fibrous layer covering the anterior surface of the joint. It is attached to the front
of the medial epicondyle and to the front of the humerus immediately above the
coronoid and radial fossae; below, to the anterior surface of the coronoid process
of the ulna and to the annular ligament (page 324), being continuous on either
side with the collateral ligaments. Its superficial fibers pass obliquely from the
medial epicondyle of the humerus to the annular ligament. The middle fibers,
vertical in direction, pass from the upper part of the coronoid depression and
become partly blended with the preceding, but are inserted mainly into the anterior
surface of the coronoid process. The deep or transverse set intersects these at
right angles. This ligament is in relation, in front, with the Brachialis, except
at its most lateral part.
21
322 SYNDESMOLOGY
The Posterior Ligament (Fig. 330). — This posterior ligament is thin and mem-
branous, and consists of transverse and oblique fibers. Above, it is attached to
the humerus* immediately behind the capitulum and close to the medial margin
of the trochlea, to the margins of the olecranon fossa, and to the back of the lateral
epicondyle some little distance from the trochlea. Below, it is fixed to the upper
and lateral margins of the olecranon, to the posterior part of the annular ligament,
and to the ulna behind the radial notch. The transverse fibers form a strong band
which bridges across the olecranon fossa; under cover of this band a pouch of
synovial membrane and a pad of fat project into the upper part of the fossa when
the joint is extended. In the fat are a few scattered fibrous bundles, which pass
from the deep surface of the transverse band to the upper part of the fossa. This
ligament is in relation, behind, with the tendon of the Triceps brachii and the
Ancona?us.
The Ulnar Collateral Ligament (ligamentum collaterale ulnare; internal lateral
ligament) (Fig. 329). — This ligament is a thick triangular band consisting of two
portions, an anterior and posterior united by a thinner intermediate portion. The
anterior portion, directed obliquely forward, is attached, above, by its apex, to the
front part of the medial epicondyle of the humerus; and, below, by its broad base
to the medial margin of the coronoid process. The posterior portion, also of trian-
gular form, is attached, above, by its apex, to the lower and back part of the medial
epicondyle; below, to the medial margin of the olecranon. Between these two
bands a few intermediate fibers descend from the medial epicondyle to blend with
a transverse band which bridges across the notch between the olecranon and the
coronoid process. This ligament is in relation with the Triceps brachii and Flexor
carpi ulnaris and the ulnar nerve, and gives origin to part of the Flexor digitorum
sublimis.
The Radial Collateral Ligament (ligamentum collaterale radiale; external lateral
ligament) (Fig. 330). — This ligament is a short and narrow fibrous band, less dis-
tinct than the ulnar collateral, attached, above, to a depression below the lateral
epicondyle of the humerus; below, to the annular ligament, some of its most pos-
terior fibers passing over that ligament, to be inserted into the lateral margin of
the ulna. It is intimately blended with the tendon of origin of the Supinator.
Synovial Membrane (Figs. 331, 332). — The synovial membrane is very extensive. It extends
from the margin of the articular surface of the humerus, and lines the coronoid, radial and olec-
ranon"fossse on that bone; it is reflected over the deep surface of the capsule and forms a pouch
between the radial notch, the deep surface of the annular ligament, and the circumference of the
head of the radius. Projecting between the radius and ulna into the cavity is a crescentic fold of
synovial membrane, suggesting the division of the joint into two; one the humeroradial, the
other the humeroulnar.
Between the capsule and the synovial membrane are three masses of fat: the largest, over
the olecranon fossa, is pressed into the fossa by the Triceps brachii during the flexion ; the second,
over the coronoid fossa, and the third, over the radial fossa, are pressed by the Brachialis into
their respective fossae during extension.
The muscles in relation with the joint are, in front, the Brachialis; behind, the Triceps brachii
and Anconams; laterally, the Supinator, and the common tendon of origin of the Extensor muscles;
medially, the common tendon of origin of the Flexor muscles, and the Flexor carpi ulnaris.
The arteries supplying the joint are derived from the anastomosis between the profunda and
the superior and inferior ulnar collateral branches of the brachial, with the anterior, posterior,
and interosseous recurrent branches of the uhiar, and the recurrent branch of the radial. These
vessels form a complete anastomotic network around the joint.
The nerves of the joint are a twig from the ulnar, as it passes between the medial condyle and
the olecranon; a filament from the musculocutaneous, and two from the median.
Movements.— The elbow-joint comprises three different portions — viz., the joint between
the ulna and humerus, that between the head of the radius and the humerus, and the proximal
radioulnar articulation, described below. All these articular surfaces are enveloped by a common
synovial membrane, and the movements of the whole joint should be studied together. The com-
bination of the movements of flexion and extension of the forearm with those of pronation and
supination of the hand, which is ensured by the two being performed at the same joint, is essential
to the accm-acy of the various minute movements of the hand.
ELBOW-JOINT
323
The portion of the joint between the ulna and humerus is a simple hinge-joint, and allows of
movements of flexion and extension only. Owing to the obliquity of the trochlea of the humerus,
this movement does not take place in the antero-posterior plane of the body of the humerus.
When the forearm is extended and supinated, the axes of the arm and forearm are not in the same
Une; the arm forms an obtuse angle with the forearm, the hand and forearm being directed lateral-
ward. During flexion, however, the forearm and the hand tend to approach the middle line of
the body, and thus enable the hand to be easily carried to the face. The accurate adaptation
of the trochlea of the humerus, with its prominences and depressions, to the semilunar notch of
the uhia, prevents any lateral movement. Flexion is produced by the action of the Biceps brachii
and Brachialis, assisted by the Brachioradialis and the muscles arismg from the medial condyle
of the humerus; extension, by the Triceps brachii and Ancona;us, assisted by the Extensors of
the wrist, the Extensor digitorum communis, and the Extensor digiti quinti proprius.
Fig. 331. — Capsule of elbow-joint (distended).
Anterior aspect.
FiQ. 332. — Capsule of elbow-joint (distended).
Posterior aspect.
The joint between the head of the radius and the capitulum of the humerus is an arthrodial
joint. The bony surfaces would of themselves constitute an enarthrosis and allow of movement
in all directions, were it not for the annular ligament, by which the head of the radius is bound
to the radial notch of the ulna, and which prevents any separation of the two bones laterally.
It is to the same ligament that the head of the radius owes its security from dislocation, which
would otherwise tend to occur, from the shallowness of the cup-like surface on the head of the
radius. In fact, but for this ligament, the tendon of the Biceps brachii would be hable to pull
the head of the radius out of the joint. The head of the radius is not in complete contact with
the capitulum of the humerus in all positions of the joint. The capitulum occupies only the
anterior and inferior surfaces of the lower end of the humerus, so that in complete extension a
part of the radial head can be plainly felt projecting at the back of the articulation. In full
flexion the movement of the radial head is hampered by the compression of the surrounding soft
parts, so that the freest rotatory movement of the radius on the humerus (pronation and supina-
tion) takes place in semiflexion, in which position the two articular surfaces are in most intimate
324
SYNDESMOLOGY
contact. Flexion and extension of the elbow-joint are limited by the tension of the structures
on the front and back of the joint; the limitation of flexion is also aided by the soft structures of
the arm and forearm coming into contact.
In any position of flexion or extension, the radius, carrying the hand with it, can be rotated in
the proximal radioulnar joint. The hand is directly articulated to the lower surface of the radius
only, and the ulnar notch on the lower end of the radius travels around the lower end of the ulna.
The latter bone is excluded from the wrist -joint by the articular disk. Thus, rotation of the head
of the radius aroimd an axis passing through the center of the radial head of the humerus imparts
circular movement to the hand through a very considerable arc.
V. Radioulnar Articulations (Articulatio Radioulnaris).
The articulation of the radius with the ulna is effected by ligaments which con-
nect together the extremities as well as the bodies of these bones. The ligaments
may, consequently, be subdivided into three sets: 1, those of the proximal radio-
ulnar articulation; 2, the middle radioulnar ligaments; 3, those of the distal radio-
ulnar articulation.
Proximal Radioulnar Articulation {articulatio radioulnaris proximalis; superior
radioulnar joint). — This articulation is a trochoid or pivot-joint between the
circumference of the head of the radius and the ring formed by the radial notch
of the ulna and the a?mular ligament.
Head of radius Quadrate Semilunar
(cut) ligament notch
Annular ligament
Radial notch
Fig. 333.-
Olecranon {cut)
-Annular ligament of radius, from above. The head of the radius has been sawn off and the bone
dislodged from the ligament.
The Annular Ligament {ligamentum annulare radii; orbicular ligament) (Fig. 333).
— This ligament is a strong band of fibers, which encircles the head of the radius,
and retains it in contact with the radial notch of the ulna. It forms about four-
fifths of the osseo-fibrous ring, and is attached to the anterior and posterior margins
of the radial notch; a few of its lower fibers are continued around below the cavitv
and form at this level a complete fibrous ring. Its upper border blends with the
anterior and posterior ligaments of the elbow, while from its lower border a thin
loose membrane passes to be attached to the neck of the radius; a thickened band
which extends from the inferior border of the annular ligament below the radial
notch to the neck of the radius is known as the quadrate ligament. The superficial
surface of the annular ligament is strengthened by the radial collateral ligament
of the elbow, and affords origin to part of the Supinator. Its deep surface is smooth,
and lined by synovial membrane, which is continuous with that of the elbow-joint.
RADIOULNAR ARTICULATIONS 325
Movements.— The movements allowed in this articulation are limited to rotatory movements
of the head of the radius within the ring formed by the annular ligament and the radial notch
of the ulna; rotation forward being called pronation; rotation backward, supination. Supination
is performed by the Biceps brachii and Supinator, assisted to a shght extent by the Extensor
muscles of the thumb. Pronation is performed by the Pronator teres and Pronator quadratus.
Middle Radioulnar Union.— The shafts of the radius and uhia are connected
by the Oblique Cord and the Interosseous Membrane.
The Oblique Cord {chorda obliqua; oblique ligament) (Fig. 829). — The oblique
cord is a small, flattened band, extending downward and lateralward, from the
lateral side of the tubercle of the ulna at the base of the coronoid process to the
radius a little below the radial tuberosity. Its fibers run in the opposite direction
to those of the interosseous membrane. It is sometimes wantins:.
The Interosseous Membrane {memhrana interossea antebrachii). — ^The interosseous
membrane is a broad and thin plane of fibrous tissue descending obliquely down-
ward and medialward, from the interosseous crest of the radius to that of the ulna;
the lower part of the membrane is attached to the posterior of the two lines into
which the interosseous crest of the radius divides. It is deficient above, commencing
about 2.5 cm. beneath the tuberosity of the radius; is broader in the middle than
at either end; and presents an oval aperture a little above its lower margin for the
passage of the volar interosseous vessels to the back of the forearm. This mem-
brane serves to connect the bones, and to increase the extent of surface for the
attachment of the deep muscles. Between its upper border and the oblique cord
is a gap, through which the dorsal interosseous vessels pass. Two or three fibrous
bands are occasionallv found on the dorsal surface of this membrane; thev descend
obliquely from the idna toward the radius, and have consequently a direction
contrary to that of the other fibers. The membrane is in relation, in front, by
its upper three-fourths, with the Flexor pollicis longus on the radial side, and with
the Flexor digitorum profundus on the ulnar, lying in the interval between which
are the volar interosseous vessels and nerve; by its lower fourth with the Pronator
quadratus; behind, with the Supinator, Abductor pollicis longus. Extensor pollicis
brevis. Extensor pollicis longus. Extensor indicis proprius; and, near the wrist,
with the volar interosseous artery and dorsal interosseous nerve.
Distal Radioulnar Articulation {articulatio radioulnaris distalis; inferior radio-
ulnar joint). — This is a pivot-joint formed between the head of the ulna and the
ulnar notch on the lower end of the radius. The articular surfaces are connected
together by the following ligaments:
The Volar Radioulnar. The Dorsal Radioulnar.
The Articular Disk.
The Volar Radioulnar Ligament {anterior radioulnar ligament) (Fig. 334). — This
ligament is a narrow band of fibers extending from the anterior margin of the ulnar
notch of the radius to the front of the head of the ulna.
The Dorsal Radioulnar Ligament {posterior radioulnar ligament) (Fig. 335). —
This ligament extends between corresponding surfaces on the dorsal aspect of the
articulation.
The Articular Disk {discus articularis; triangular fibrocariilage) (Fig. 336).— The
articular disk is triangular in shape, and is placed transversely beneath the head
of the ulna, binding the lower ends of the ulna and radius firmly together. Its
periphery is thicker than its center, which is occasionally perforated. It is attached
by its apex to a depression between the styloid process and the head of the ulna;
and by its base, which is thin, to the prominent edge of the radius, which separates
the ulnar notch from the carpal articular surface. Its margins are united to the
ligaments of the wrist-joint. Its upper surface, smooth and concave, articulates
with the head of the ulna, forming an arthrodial joint; its under surface, also con-
326
SYXDESMOLOGY
cave and smooth, forms part of the wrist-joint and articulates with the triangular
bone and medial part of the lunate. Both surfaces are clothed by synovial mem-
brane; the upper, by that of the distal radioulnar articulation, the under, by that
of the wrist.
Distal radio-ulnar
articulation
' * " ^^^ " / if-^'^^'Wi ^ ntercarpal art tcvlat ions
Pisohamate hgarrve^it
Pisometacarpal ligament
Carpometacarpal
nrticidatioiis
Fig. 334. — Ligaments of wrist. Anterior view
Synovial Membrane (Fig. 336). — The synovial membrane of this articulation is extremely
loose, and extends upward as a recess {recessus sacciformis) between the radius and the ulna.
Distal radio-ulnar,
articulation
Wrist-joint
Iniercarpal articulations
Carpometacarpal ,«j,:
articulations
Fig. 335. — Ligaments of wrist. Posterior \new.
Movements. — The movements in the distal radioulnar articulation consist of rotation of the
lower end of the radius around an axis which passes through the center of the head of the ulna.
When the radius rotates forward, pronation of the forearm and hand is the result; and when back-
ward, supination. It will thus be seen that in pronation and supination the radius describes the
RADIOCARPAL ARTICULATION OR WRIST-JOINT
327
segment of a cone, the axis of which extends from the center of the head of the radius to the
middle of the head of the uhia. In this movement tlie head of the ulna is not stationary, but
describes a curve in a direction opposite to that taken by the head of the radius. This, however,
is not to be regarded as a rotation of the ulna— the curve which the liead of this bone describes
is due to a combined antero-posterior and rotatory movement, the former taking place almost
entirely at the elbow-joint, the latter at the shoulder-joint. ,
Wrist- joint -
Radial collateral
ligament
> J '-' ''
Pisiform
Distal radioulnar
articulation
Articular disc
Ulnar collateral ligament
Fig. 336. — \ertical section through the articulatioas at the wrist, showing the synovial cavities.
.VI. Radiocarpal Articulation or Wrist-joint (Articulatio Radiocarpea)
(Figs. 334, 335).
The wTist-joint is a condyloid articulation. The parts forming it are the lower
end of the radius and under surface of the articular disk above; and the navicular,
lunate, and triangular bones below. The articular surface of the radius and the
under surface of the articular disk form together a transversely elliptical concave
surface, the receiving cavity. The superior articular surfaces of the navicular,
lunate, and triangidar form a smooth con^'ex surface, the condyle, which is received
into the concavity. The joint is surrounded by a capsule, strengthened by the
following ligaments:
The Volar Radiocarpal.
The Dorsal Radiocarpal.
The Ulnar Collateral.
The Radial Collateral.
The Volar Radiocarpal Ligament (ligamentum radiocarpeum volare; anterior liga-
ment) (Fig. 334). — This ligament is a broad membranous band, attached above
to the anterior margin of the lower end of the radius, to its styloid process, and to
the front of the lower end of the ulna; its fibers pass downward and medialward
to be inserted into the volar surfaces of the navicular, lunate, and triangular
bones, some being continued to the capitate. In addition to this broad mem-
brane, there is a rounded fasciculus, superficial to the rest, which reaches from the
base of the styloid process of the ulna to the lunate and triangular bones. The
ligament is perforated by apertures for the passage of vessels, anj is in relation,
in front, with the tendons of the Flexor digitorum profundus and Flexor pollicis
328 SYNDESMOLOGY
longus; behind, it is closely adherent to the anterior border of the articular disk
of the distal radioulnar articulation.
The Dorsal Radiocarpal Ligament {ligamentum radiocarpeum dorsale; posterior
ligament) (Fig. 335). — The dorsal radiocarpal ligament less thick and strong than
the volar, is attached, above, to the posterior border of the lower end of the radius;
its fibers are directed obliquely downward and medialward, and are fixed, below,
to the dorsal surfaces of the navicular, lunate, and triangular, being continuous
with those of the dorsal intercarpal ligaments. It is in relation, behind, with the
Extensor tendons of the fingers; \n front, it is blended with the articular disk.
The , Ulnar Collateral Ligament {ligamentum coUaterale carpi idnare; internal
lateral ligament) (Fig. 334). — The ulnar collateral ligament is a rounded cord,
attached above to the end of the styloid process of the ulna, and dividing below
into two fasciculi, one of which is attached to the medial side of the triangular
bone, the other to the pisiform and transverse carpal ligament.
The Radial Collateral Ligament {ligamentum coUaterale carpi radiale; external
lateral ligament) (Fig. 335). — The radial collateral ligament extends from the tip
of the styloid process of the radius to the radial side of the navicular, some of its
fibers being prolonged to the greater multangular bone and the transverse carpal
ligament. It is in relation with the radial artery, which separates the ligament
from the tendons of the Abductor pollicis longus and Extensor pollicis brevis.
Synovial Membrane (Fig. 330). — The synovial membrane lines the deep surfaces of the hga-
ments above described, extending from the margin of the lower end of the radius and articular
disk above to the margins of the articular surfaces of the carpal bones below. It is loose and
lax, and presents numerous folds, especially behind.
The wrist-joint is covered in front by the Flexor, and behind by the Extensor tendons.
The arteries supplying the joint are the volar and dorsal carpal branches of the radial and
ulnar, the volar and dorsal metacarpals, and some ascending branches from the deep volar arch.
The nerves are derived from the ulnar and dorsal interosseous.
Movements. — The movements permitted in this joint are flexion, extension, abduction, adduc-
tion, and circumduction. They will be studied with those of the carpus, with which they are
combined.
Vn. Intercarpal Articulations (Articulationes Intercarpeae ; Articulations
of the Carpus).
These articulations may be subdivided into three sets:
1. The Articulations of the Proximal Row of Carpal Bones.
2. The Articulations of the Distal Row of Carpal Bones.
3. The Articulations of the Two Rows with each Other.
Articulations of the Proximal Row of Carpal Bones. — These are arthrodial
joints. The navicular, lunate, and triangular are connected by dorsal, volar, and
interosseous ligaments.
The Dorsal Ligaments {ligamenta intercarpea dorsalia) .—The dorsal ligaments,
two in number, are placed transversely behind the bones of the first row; they
connect the navicular and lunate, and the lunate and triangular.
The Volar ligaments {ligamenta intercarpea volaria; palmar ligaments). — The volar
ligaments, also two, connect the navicular and lunate, and the lunate and trian-
gular; they are less strong than the dorsal, and placed very deeply behind the
Flexor tendons and the volar radiocarpal ligament.
The Interosseous Ligaments {ligamenta intercarpea interossea) (Fig. 336). — The
interosseous ligaments are two narrow bundles, one connecting the lunate with
the navicular, the other joining it to the triangular. They are on a level with the
superior surfaces of these bones, and their upper surfaces are smooth, and form
part of the convex articular surface of the wrist-joint.
INTERCARPAL ARTICULATIONS 329
The ligaments connecting the pisiform bone are the articular capsule and the
two volar ligaments.
The articular capsule is a thin membrane which connects the pisiform to the
triangular; it is lined by synovial membrane.
The two volar ligaments are strong fibrous bands; one, the pisohamate ligament,
connects the pisiform to the hamate, the other, the pisometacarpal ligament, joins
the pisiform to the base of the fifth metacarpal bone (Fig. l^'M). These ligaments
are, in reality, prolongations of the tendon of the Flexor carpi ulnaris.
Articulations of the Distal Row of Carpal Bones.— These also are arthrodial
joints; the bones are connected by dorsal, volar, and interosseous ligaments. •
The Dorsal Ligaments (ligamenta intercarpea dorsalia). — The dorsal ligaments,
three in number, extend transversely from one bone to another on the dorsal
surface, connecting the greater with the lesser multangular, the lesser multangular
with the capitate, and the capitate with the hamate.
The Volar Ligaments {ligamenta intercarpea volaria; palmar ligaments). — The
volar ligaments, also three, have a similar arrangement on the volar surface.
The Interosseous Ligaments {ligamienta intercarpea interossea). — The three inter-
osseous ligaments are much thicker than those of the first row; one is placed be-
tween the capitate and the hamate, a second betw^een the capitate and the lesser
multangular, and a third between the greater and lesser multangulars. The first
is much the strongest, and the third is sometimes wanting.
Articulations of the Two Rows of Carpal Bones with Each Other. — The joint
between the navicular, lunate, and triangular on the one hand, and the second
row of carpal bones on the other, is named the midcarpal joint, and is made up of
three distinct portions: in the center the head of the capitate and the superior
surface of the hamate articulate with the deep cup-shaped cavity formed by the
navicular and lunate, and constitute a sort of ball-and-socket joint. On the
radial side the greater and lesser multangulars articulate with the navicular, and
on the ulnar side the hamate articulates with the triangular, forming gliding joints.
The ligaments are: volar, dorsal, ulnar and radial collateral.
The Volar Ligaments {ligamenta intercarpea volaria; anterior or palmar ligaments) .
— The volar ligaments consist of short fibers, which pass, for the most part, from
the volar surfaces of the bones of the first row to the front of the capitate.
The Dorsal Ligaments {ligamenta intercarpea dorsalia; posterior ligaments). —
The dorsal ligaments consist of short, irregular bundles passing between the dorsal
surfaces of the bones of the first and second rows.
The Collateral Ligaments {lateral ligaments). — The collateral ligaments are very
short; one is placed on the radial, the other on the ulnar side of the carpus; the
former, the stronger and more distinct, connects the navicular and greater mul-
tangular, the latter the triangular and hamate; they are continuous with the
collateral ligaments of the wrist-joint. In addition to these ligaments, a slender
interosseous band sometimes connects the capitate and the navicular.
Synovial Membrane. — The synovial membrane of the carpus is very extensive (Fig. 336),
and bounds a synovial cavity of very irregular shape. The upper portion of the cavity inter-
venes between the under surfaces of the navicular, lunate, and triangular bones and the upper
surfaces of the bones of the second row. It sends two prolongations upward — between the navic-
ular and lunate, and the lunate and triangular— and three prolongations downward between
the four bones of the second row. The prolongation between the greater and lesser multangulars,
or that between the lesser multangular and capitate, is, owing to the absence of the interosseous
Ugament, often continuous with the cavity of the carpometacarpal joints, sometimes of the
second, third, fourth, and fifth metacarpal bones, sometimes of the second and third only. In
the latter condition the joint between the hamate and the fourth and fifth metacarpal bones
has a separate sjoiovial membrane. The synovial cavities of these joints are prolonged for a
short distance between the bases of the metacarpal bones. There is a separate synovial mem-
brane between the pisiform and triangular.
330 SYNDESMOLOGY
Movements. — The articulation of the hand and wi-ist considered as a whole involves four
articular surfaces: (a) the inferior surfaces of the radius and articular disk; (b) the superior
surfaces of the navicular, lunate, and triangular, the pisiform having no essential part in the
movement of the hand; (c) the S-shaped surface formed by the inferior suifaces of the navicular,
lunate, and triangular; {d) the reciprocal surface formed by the upper surfaces of the bones of
the second row. These four surfaces form two joints: (1) a proximal, the wrist-joint proper;
and (2) a distal, the mid-carpal joint.
1. The wTist-joint proper is a true condyloid articulation, and therefore all movements but
rotation are permitted. Flexion and extension are the most free, and of these a greater amoxmt
of extension than of flexion is permitted, since the articulating surfaces extend farther on the dorsal
than on the volar surfaces of the carpal bones. In tliis movement the carpal bones rotate on a
transv«rse axis drawn between the tips of the stj'loid processes of the radius and ulna. A certain
amount of adduction (or ulnar flexion) and abduction (or radial flexion) is also permitted. The
former is considerably greater in extent than the latter on accomit of the shortness of the styloid
process of the ulna, abduction being soon limited by the contact of the styloid process of the
radius with the greater multangular. In this movement the carpus revolves upon an antero-
posterior axis drawn through the center of the WTist.^ Finallj', circumduction is permitted by
the combined and consecutive movements of adduction, extension, abduction, and flexion. No
rotation is possible, but the effect of rotation is obtained bj- the pronation and supination of the
radius on the ulna. • The movement oi flexion is performed by the Flexor carpi radialis, the Flexor
carpi ulnaris, and the Palmaris longus; extension by the Extensores carpi radiales longus and
brevis and the Extensor carpi ulnaris; adduction (ulnar flexion) by the Flexor carpi ulnaris and
the Extensor carpi ulnaris; and abduction (radial flexion) by the Abductor polhcis longus, the
Extensors of the thumb, and the Extensores carpi radiales longus and brevis and the Flexor carpi
radiahs. When the fingers are extended, flexion of the wrist is performed by the Flexores carpi
radialis and uhiaris and extension is aided by the Extensor digitorum communis. When the
fingers are flexed, flexion of the wrist is aided by the Flexores digitorum sublimis and profundus,
and extension is performed by the Extensores carpi radiales and uhiaris.
2. The chief movements permitted in the mid-carpal joint are flexion and extension and a
slight amount of rotation. In flexion ajid extension, which are the movements most freely enjoj'ed,
the greater and lesser multangulars on the radial side and the hamate on the ulnar side glide
forward and backward on the navicular and triangular respectively, while the head of the capitate
and the superior surface of the hamate rotate in the cup-shaped cavity of the navicular and
lunate. Flexion at this joint is freer than extension. A very trifling amount of rotation is also
permitted, the head of the capitate rotating around a vertical axis drawn through its own center,
while at the same time a shght ghding movement takes place in the lateral and medial portions
of the joint.
Vni. Carpometacarpal Articulations (Articulationes Carpometacarpeae).
Carpometacarpal Articulation of the Thumb {articulatio carpometacarpea poUicis).
— This is a joint of reciprocal reception between the first metacarpal and the
greater multangular; it enjoys great freedom of movement on accoimt of the
configuration of its articular surfaces, which are saddle-shaped. The joint is sur-
rounded by a capsule, which is thick but loose, and passes from the circumference
of the base of the metacarpal bone to the rough edge bounding the articular surface
of the greater multangular; it is thickest laterally and dorsally, and is lined by
synovial membrane.
Movements. — In this articulation the movements permitted are flexion and extension in the
plane of the palm of the hand, abduction and adduction in a plane at right angles to the palm,
circumduction, and opposition. It is by the movement of opposition that the tip of the thumb
i3 brought into contact with the volar surfaces of the slightly flexed fingers. This movement is
effected through the medium of a small sloping facet on the anterior Hp of the saddle-shaped
articular surface of the greater multangular. The Flexor muscles pull the corresponding part
of the articular surface of the metacarpal bone on to this facet, and the movement of opposition
is then carried out by the Adductors.
Flexion of this joint is produced by the Flexores polhcis longus and brevis, assisted by the
Opponens poUicis and the Adductor poUicis. Extension is effected mainly by the abductor
pollicis longus, assisted by the Extensores poUicis longus and brevis. Adduction is carried out
by the Adductor; abduction mainly by the Abductores poUicis longus and brevis, assisted by the
Extensors.
' H. M. Johnston (Journal of Anatomy and Physiology, vol. xli) maintains that n ulnar and radial flexion only
slight lateral movement occurs at the radiocarpal joint, and that in coinplete flexion and extension of the hand there
is a small degree of ulnar flexion at the radiocarpal joint.
INTERMETACARPAL ARTICULATIONS 331
Articulations of the Other Four Metacarpal Bones with the Carpus (articulationes
car pometacar pea). —The joints between the carpus and the second, third, fourth,
and fifth metacarpal bones are arthrodial. The bones are united by dorsal, volar,
and interosseous ligaments.
The Dorsal Ligaments (ligamenta carpometacarpea dorsalia). — The dorsal ligaments,
the strongest and most distinct, connect the carpal and metacarpal bones on their
dorsal surfaces. The second metacarpal bone receives two fasciculi, one from the
greater, the other from the lesser multangular; the third metacarpal receives two,
one each from the lesser multangular and capitate; the fourth two, one each from
the capitate and hamate; the fifth receives a single fasciculus from the hamate,
and this is continuous with a similar ligament on the volar surface, forming an
incomplete capsule.
• The Volar Ligaments {ligamenta carpometacarpea volaria; palmar ligaments). —
The volar ligaments have a somewhat similar arrangement, with the exception
of those of the third metacarpal, which are three in number: a lateral one from the
greater multangular, situated superficial to the sheath of the tendon of the Flexor
carpi radialis; and intermediate one from the capitate; and a medial one from
the hamate.
The Interosseous Ligaments. — The interosseous ligaments consist of short, thick
fibers, and are limited to one part of the carpometacarpal articulation; they con-
nect the contiguous inferior angles of the capitate and hamate with the adjacent
surfaces of the third and fourth metacarpal bones.
S3movial Membrane. — The synovial membrane is a continuation of that of the intercarpal
joints. Occasionally, the joint between the hamate and the fourth and fifth metacarpal bones
has a separate synovial membrane.
The synovial membranes of the wrist and carpus (Fig. 3.36) are thus seen to be five in number.
The first passes from the lower end of the ulnar to the ulnar notch of the radius, and lines the upper
surface of the articular disk. The second passes from the articular disk and the lower end of the
radius above, to the bones of the first row below. The third, the most extensive, passes between
the contiguous margins of the two rows of carpal bones, and sometimes, in the event of one of
the interosseous ligaments being absent, between the bones of the second row to the carpal extremi-
ties of the second, third, fourth, and fifth metacarpal bones. The /our//i extends from the margin
of the greater multangular to the metacarpal bone of the thumb. The fifth runs between the
adjacent margins of the triangular and pisiform bones. Occasional!}' the fourth and fifth carpo-
metacarpal joints have a separate synovial membrane.
Movements. — The movements permitted in the carpometacarpal articulations of the fingers
are limited to shght gliding of the articular surfaces upon each other, the extent of which varies
in the different joints. The metacarpal bone of the little finger is most movable, then that of
the ring finger; the metacarpal bones of the index and middle fingers are almost immovable.
K. Intermetacarpal Articulations (Articulationes Intermetacarpese ; Articulations
of the Metacarpal Bones with Each Other).
The bases of the second, third, fourth and fifth metacarpal bones articulate
with one another by small surfaces covered with cartilage, and are connected
together by dorsal, volar, and interosseous ligaments.
The dorsal {ligamenta basium oss. metacarp. dorsalia) and volar ligam'ents {liga-
menta hasium oss. metacarp. volaria; palmar ligaments) pass transversely from
one bone to another on the dorsal and volar surfaces. The interosseous hgaments
{ligamenta basium oss. metacarp. interossea) connect their contiguous surfaces,
just distal to their collateral articular facets.
The synovial membrane for these joints is continuous with that of the carpometacarpal
articulations.
The Transverse Metacarpal Ligament {ligamentum capitulorum [oss. metacarpalium]
transversum) (Fig. 337).— This ligament is a narrow fibrous band, which runs across
the volar surfaces of the heads of the second, third, fourth and fifth meta-
carpal bones, connecting them together. It is blended with the volar (glenoid)
332
SYNDESMOLOGY
ligamehts of the metacarpophalangeal articulations. Its volar surface is concave
where the Flexor tendons pass over it ; behind it the tendons of the Interossei pass
to their insertions.
X. Metacarpophalangeal Articulations (Articulationes Metacarpophalangese ;
Metacarpophalangeal Joints) (Figs. 337, 338).
These articulations are of the condyloid kind, formed by the reception of the
rounded heads of the metacarpal bones into shallow cavities on the proximal ends
of the first phalanges, with the exception of that of the thumb, which presents
more of the characters of a ginglymoid joint. Each joint has a volar and two
collateral ligaments.
Metacarpal hone ■
Transverse
nietacarpal — ^^5
ligament
Groove for
Flexor tendons
1st phalanx
Volar ligament
Volar ligament
i\ ,
,\VM
Metacarpal
bone \
3rd phalanx
Collateral
ligament
Collateral
ligament
2nd phalanx
Collateral
ligament
Fig. 337. — Metacarpophalangeal articulation and
articulations of digit. Volar aspect.
Fig.
338. — Metacarpophalangeal articulation
articulations of digit. Ulnar aspect.
and
The Volar Ligaments {glenoid ligaments of Criiveilhier; palmar or vaginal ligaments).
-^The volar ligaments are thick, dense, fibrocartilaginous structures, placed upon
the volar surfaces of the joints in the intervals between the collateral ligaments, to
which they are connected ; they are loosely united to the metacarpal bones, but are
very firmly attached to the bases of the first phalanges. Their volar surfaces are
intimately blended with the transverse metacarpal ligament, and present grooves
for the passage of the Flexor tendons, the sheaths surrounding which are connected
to the sides of the grooves. Their deep surfaces form parts of the articular facets
for the heads of the metacarpal bones, and are lined by synovial membranes.
The Collateral Ligaments {ligamenta collateralia; lateral ligaments). — The col-
lateral ligaments are strong, rounded cords, placed on the sides of the joints;
COXAL ARTICULATION OR HIP- JOINT 333
each is attached by one extremity to the posterior tubercle and adjacent depres-
sion on the side of the head of the metacarpal bone, and by the other to the
contiguous extremity of the phalanx.
The dorsal surfaces of these joints are covered by the expansions of the Extensor
tendons, together with some loose areolar tissue which connects the deep surfaces
of the tendons to the bones.
Movements. — The movements which occur in these joints are flexion, extension, adduction,
abduction, and circumduction; the movements of abduction and adduction are very Umited,
and cannot be performed when the fingers are flexed.
XI. Articulations of the Digits (Articulationes Digitorum Manus ; Interphalangeal
Joints) (P'igs. ;:i;37, ;33cS).
The interphalangeal articulations are hinge-joints; each has a volar and two
collateral ligaments. The arrangement of these ligaments is similar to those in
the metacarpophalangeal articulations. The Extensor tendons supply the place
of posterior ligaments.
Movements, — The only movements permitted in the interphalangeal joints are flexion and
extension; these movements are more extensive between the first and second phalanges than
between the second and third. The amoimt of flexion is very considerable, but extension is
limited by the volar and collateral ligaments.
Muscles Acting on the Joints of the Digits. — Flexion of the metacarpophalangeal joints of the
fingers is effected by the Flexores digitorum subUmis and profundus, Lumbricales, and Interossei,
assisted in the case of the little finger by the Flexor digiti quinti brevis. Extension is produced
by the Extensor digitorum communis, Extensor indicis proprius, and Extensor digiti quinti pro-
prius.
Flexion of the interphalangeal joints of the fingers is accomphshed by the Flexor digitorum
profundus acting on the proximal and distal joints and by the Flexor digitorum sublimis acting
on the proximal joints. Extension is effected mainly by the Lumbricales and Interossei, the
long Extensors having httle or no action upon these joints.
Flexion of the metacarpophalangeal joint of the thumb is effected by the Flexores polTlcis
longus and brevis; extension by the Extensores pollicis longus and brevis. Flexion of the inter-
phalangeal joint is accomplished by the Flexor pollicis longus, and extension by the Extensor
pollicis longus.
ARTICULATIONS OF THE LOWER EXTREMITY.
The articulations of the Lower Extremity comprise the following:
I. Hip. V. Intertarsal.
II. Knee. VI. Tarsometatarsal.
III. Tibiofibular. VII. Intermetatarsal.
IV. Ankle. VIII. Metatarsophalangeal.
IX. Articulations of the Digits.
I. Coxal Articulation or Hip-joint (Articulatio Coxae).
This articulation is an enarthrodial or ball-and-socket joint, formed by the
reception of the head of the femur into the cup-shaped cavity of the acetabulum.
The articular cartilage on the head of the femur, thicker at the center than at the
circumference, covers the entire surface with the exception of the fovea capitis
femoris, to which the ligamentum teres is attached; that on the acetabulum forms
an incomplete marginal ring, the lunate surface. Within the lunate surface there
is a circular depression devoid of cartilage, occupied in the fresh state by a mass
of fat, covered by synovial membrane. The ligaments of the joint are:
The Articular Capsule. The Pubocapsular.
The Iliofemoral. The Ligamentum Teres Femoris.
The Ischiocapsular. The Glenoidal Labrum.
The Transverse Acetabular
334
SYNDESMOLOGY
The Articular Capsule (capsula articularis; capsular ligament) (Figs. 339, 340). —
The articular capsule is strong and dense. Above, it is attached to the margin
of the acetabulum 5 to 6 mm. beyond the glenoidal labrum behind; but in front,
it is attached to the outer margin of the labrum, and, opposite to the notch where
the margin of the cavity is deficient, it is connected to the transverse ligament,
and by a few fibers to the edge of the obturator foramen. It surrounds the neck
of the femur, and is attached, in front, to the intertrochanteric line; above, to the
base of the neck; behind, to the neck, about 1.25 cm. above the intertrochanteric
crest; beloiv, to the lower part of the neck, close to the lesser trochanter. From
its femoral attachment some of the fibers are reflected upward along the neck
as longitudinal bands, termed retinacula. The capsule is much thicker at the upper
and forepart of the joint, where the greatest amount of resistance is required;
Ani. inf. iliac spine —
Intertrochanteric
line
Pig. 339. — Right hip-joint from the front. (Spalteholz.)
behind and below, it is thin and loose. It consists of two sets of fibers, circular
and longitudinal. The circular fibers, zona orbicularis, are most abundant at the
lower and back part of the capsule (Fig. 342), and form a sling or collar around the
neck of the femur. Anteriorly they blend with the deep surface of the iliofemoral
ligament, and gain an attachment to the anterior inferior iliac spine. The longi-
tudinal fibers are greatest in amount at the upper and front part of the capsule,
where they are reinforced by distinct bands, or accessory ligaments, of which the
most important is the iliofemoral ligament. The other accessory bands are known
as the pubocapsular and the ischiocapsular ligaments. The external surface of the
capsule is rough, covered by numerous muscles, and separated in front from the
Psoas major and Iliacus by a bursa, which not infrequently commimicates by a
circular aperture with the cavity of the joint.
COXAL ARTICULATION OR HIP-JOINT 335
The mofemoral Ligament (/.:^amen^um iliofemorale; Y -ligament; ligament of
Bigeloic) (Fig «9).-lhe iliofemoral ligament is a band of great s rength which
hes m front of the jomt; it is mtimately connected with the capsule, and ser es
to strengthen It m this situation. It is attached, above, to the lower part of the
anterior inferior ilmc spine; 6./oz., it divides into two bands, one of which passes
downward a^nd is fixed to the lower part of the intertrochanteric line; the other
IS directed downward and lateralward and is attached to the upper part of the
same line. Between the two bands is a thinner part of the capsule. In some
cases there IS no division, and the ligament spreads out into a flat triangular band
which IS attached o the whole length of the intertrochanteric line. This ligament
IS frequently called the \ -shaped ligament of Bigelow; and its upper band is some-
times named the iliotrochanteric ligament.
Horizontal fibers
Ischiofemoral ligament
Fig 340 — The hip-joint from behind. (Quain.)
The Pubocapsular Ligament {Ugamentuvi p^ibocapsulare; 'piihofevtoral ligament). —
This ligament is attached, above, to the obturator crest and the superior ramus
of the pubis; beloio, it blends with the capsule and with the deep surface of the
vertical band of the iliofemoral ligament.
The Ischiocapsular Ligament {ligamentum iscJiiocapsnlare; ischiocapsular band;
ligament of Bertin). — The ischiocapsular ligament consists of a triangular band of
strong fibers, which spring from the ischium below and behind the acetabulum,
and blend with the circular fibers of the capsule (Fig. 340).
330
SYNDESMOLOGY
The Ligamentum Teres Femoris (Fig. 341). — The ligamentum teres femoris is a
triangular, somewhat flattened band implanted by its apex into the antero-superior
part of the fovea capitis femoris ; its base is attached by two bands, one into either
side of the acetabular notch, and between these bony attachments it blends with the
transverse ligament. It is ensheathed by the synovial membrane, and varies greatly
in strength in different subjects; occasionally only the synovial fold exists, and in
rare cases even this is absent. The ligament is made tense M'hen the thigh is
semiflexed and the limb then adducted or rotated outward; it is, on the other
hand, relaxed when the limb is abducted. It has, however, but little influence as a
ligament.
Spine of
ischimu
Ant. inf.
"^ iliac spine
■Fovea capitis
Iliofemoral ligament
Lesser trochanter
Fig. 341. — Left hipHJoint, opened by removiug the llour of the acetabulum from within the pelvis.
The Glenoidal Labnim {labrum glenoidalc; cotyloid ligament). — The glenoidal
labrum is a fibrocartilaginous rim attached to the margin of the acetabulum, the
cavity of which it deepens ; at the same time it protects the edge of the bone, and
fills up the inequalities of its surface. It bridges over the notch as the transverse
ligament, and thus forms a complete circle, which closely surrounds the head of the
femur and assists in holding it in its place. It is triangular on section, its base being
attached to the margin of the acetabulum, while its opposite edge is free and
sharp. Its two surfaces are invested by synovial membrane, the external one
being in contact with the capsule, the internal one being inclined inward so as
to narrow the acetabulum, and embrace the cartilaginous surface of the head of
the femur. It is much thicker above and behind than below and in front, and
consists of compact fibers.
The Transverse Acetabular Ligament (ligamentum transversum acetabuli; transverse
ligament). — This ligament is in reality a portion of the glenoidal labrum, though
differing from it in having no cartilage cells among its fibers. It consists of strong,
COXAL ARTICULATION OR HIP-JOINT
337
%::!mt'\: '
Fig. 342. — Hip-joint, front view. The capsular ligament has been largely removed.
Spine of
ischium
Capsule
Greater trochanter
Fig. 343. — Capsule of hip-joint (distended). Posterior aspect.
22
338
SYNDESMOLOGY
flattened fibers, which cross the acetabular notch, and convert it into a foramen
through which the nutrient vessels enter the joint.
Synovial Membrane (Fig. 343). — The synovial membrane is very extensive. Commencing
at the margin of the cartilaginous surface of the head of the femur, it covers the portion of the
neck which is contained within the joint; from the neck it is reflected on the internal surface of
the capsule, covers both surfaces of the glenoidal labrum and the mass of fat contained in the
depression at the bottom of the acetabulum, and ensheathes the ligamentum teres as far as the
head of the femur. The joint ca\-ity sometimes communicates through a hole in the capsule
between the vertical band of the ihofemoral ligament and the pubocapsular ligament with a bursa
situated on the deep surfaces of the Psoas major and Ihacus.
The muscles in relation with the joint are, in front, the Psoas major and Ihacus, separated
from the capsule by a bursa; above, the reflected head of the Rectus femoris and Gluta^us minimus,
the latter being closely adherent to the capsule; medially, the Obturator extemus and Pectineus;
behind, the Piriformis, Gemellus superior, Obturator internus, Gemellus inferior, Obturator
extemus, and Quadratus femoris (Fig. 344).
Femoral artery
Femoral nerve j Femoral vein,
Iliofevwral ligament I | i Ligamentum teres
Rectus femoris ( ( / Obturator n-erve
Piriformis I Sciatic nerve
Obturator internus
Fig. 344. — Structures surrounding right hip-joint.
The arteries supplying the joint are derived from the obturator, medial femoral circumflex,
and superior and inferior gluteals.
The nerves are articular branches from the sacral plexus, sciatic, obturator, accessory obtm'ator,
and a filament from the branch of the femoral supplying the Rectus femoris.
Movements. — The movements of the hip are very extensive, and consist of flexion, extension,
adduction, abduction, circumduction, and rotation.
The length of the neck of the femur and its inclinations to the body of the bone have the
effect of converting the angular movements of flexion, extension, adduction, and abduction par-
tially into rotatory movements in the joint. Thtis when the thigh is flexed or extended, the
head of the femtir, on account of the medial inclination of the neck, rotates within the acetabulum
with only a shght amount of gliding to and fro. The forward slope of the neck similarly affects
the movements of adduction and abduction. Conversely rotation of the thigh which is permitted
by the upward inclination of the neck, is not a simple rotation of the head of the femvir in the
acetabulum, but is accompanied by a certain amount of gliding.
THE KNEE-JOINT 339
The hip-joint presents a very striking contrast to the shoulder-joint in the much more com-
plete mechanical arrangements for its security and for the limitation of its movements. In the
shoulder, as has been seen, the head of the humerus is not adapted at all in size to the glerioid
cavity, and is hardly restrained in any of its ordinary movements by the capsule. In the hip-
joint, on the contrary, the head of the femur is closely fitted to the acetabulum for an area extend-
ing over nearly half a sphere, and at the margin of the bony cup it is still more closely embraced
by the glenoidal labrum, so that the head of the femur is held in its place by that ligament even
when the fibers of the capsule have been quite divided. The iliofemoral ligament is the strongest
of all the ligaments in the body, and is put on the stretch by any attempt to extend the femur
beyond a straight line with the trunk. That is to say, this ligament is the chief agent in main-
taining the erect position without muscular fatigue; for a vertical hne passing through the center
of gravity of the trunk falls behind the centers of rotation in the hip-joints, and therefore the
pelvis tends to fall backward, but is prevented by the tension of the ihofemoral ligaments. The
security of the joint may be provided for also by the two bones being directly united through the
ligamentum teres; but it is doubtful whether this ligament has much influence upon the mechanism
of the joint. When the knee is flexed, flexion of the hip-joint is arrested by the soft parts of the
thigh and abdomen being brought into contact, and when the knee is extended, by the action of
the hamstring muscles; extension is checked by the tension of the iliofemoral hgament; adduc-
tion by the thighs coming into contact; adduction with flexion by the lateral band of the ilio-
femoral hgament and the lateral part of the capsule; abduction by the medial band of the
iliofemoral ligament and the pubocapsular Hgament; rotation outward by the lateral band of the
ihofemoral ligament; and rotation inward by the ischiocapsular hgament and the hinder part of
the capsule. The muscles which /ex the femur on the pelvis are the Psoas major, Ihacus, Rectus
femoris, Sartorius, Pectineus, Adductores longus and brevis, and the anterior fibers of the Gluta?i
medius and minimus. Extension is mainly performed by the Glutaeus maximus, assisted by the
hamstring muscles and the ischial head of the Adductor magnus. The thigh is adduded by the
Adductores magnus, longus, and brevis, the Pectineus, the Gracihs, and lower part of the Glutaeus
maximus, and abducted by the Gluta>i medius and minimus, and the upper part of the Glutceus
maximus. The muscles which rotate the thigh inward are the Gluta>us minimus and the anterior
fibers of the Glutaeus medius, the Tensor fasciae latse and the lUacus and Psoas major; while
those which rotate it outward are the posterior fibers of the Gluteus medius, the Piriformis,
Obturatores externus and intemus, Gemelli superior and inferior, Quadratus femoris, Glutajus
maximus, the Adductores longus, brevis, and magnus, the Pectineus, and the Sartorius.
n. The Knee-joint (Articulatio Genu).
The knee-joint was formerly described as a ginglymus or hinge-joint, but is
really of a much more complicated character. It must be regarded as consisting
of three articulations in one: two condyloid joints, one between each condyle
of the femur and the corresponding meniscus and condyle of the tibia; and a third
between the patella and the femur, partly arthrodial, but not completely so,
since the articular surfaces are not mutually adapted to each other, so that the
movement is not a simple gliding one. This view of the construction of the knee-
joint receives confirmation from the study of the articulation in some of the lower
mammals, where, corresponding to these three subdivisions, three synovial cavities
are sometimes found, either entirely distinct or only connected together by small
communications. This view is further rendered probable by the existence in the
middle of the joint of the two cruciate ligaments, which must be regarded as
the collateral ligaments of the medial and lateral joints. The existence of the
patellar fold of synovial membrane would further indicate a tendency to separa-
tion of the synovial cavity into two minor sacs, one corresponding to the lateral
and the other to the medial joint.
The bones are connected together by the following ligaments:
The Articular Capsule. The Anterior Cruciate.
The Ligamentum Patellae. The Posterior Cruciate.
The Oblique Popliteal. The Medial and Lateral Menisci.
The Tibial Collateral. The Transverse.
The Fibular Collateral. The Coronary.
340
SYNDESMOLOGY
The Articular Capsule {capmla articularis; capsular UgamenT) (Fig. 345). — The
articular capsule consists of a thin, but strong, fibrous membrane ^vhich is strength-
ened in almost its entire extent by bands inseparably connected with it. Above
and in front, beneath the tendon of the Quadriceps femoris, it is represented only
by the synovial membrane. Its chief strengthening bands are derived from the
fascia lata and from the tendons surrounding the joint. In front, expansions
from the Vasti and from the fascia lata and its iliotibial band fill in the intervals
between the anterior and collateral ligaments, constituting the medial and lateral
patellar retinacula. Behind the capsule consists of vertical fibers which a'-ise
from the condyles and from the sides of the intercondyloid fossa of the femur;
the posterior part of the capsule is therefore
situated on the sides of and in front of the
cruciate ligaments, which are thus excluded from
the joint cavity. Behind the cruciate ligaments
is the oblique popliteal ligament which is aug-
mented by fibers derived from the tendon of the
Semimembranosus. Laterally, a prolongation
from the iliotibial band fills in the interval be-
tween the oblique popliteal and the fibular collat-
eral ligaments, and partly covers the latter.
Medially, expansions from the Sartorius and
Semimembranosus pass upward to the tibial
collateral ligament and strengthen the capsule.
The Ligamentimi Patellae {anterior ligament)
(Fig. 345) . — The ligamentum patelli^ is the cen-
tral portion of the common tendon of the Quad-
riceps femoris, which is continued from the
patella to the tuberosity of the tibia. It is a
strong, flat, ligamentous band, about 8 cm. in
length, attached, above, to the apex and adjoin-
ing margins of the patella and the rough depres-
sion on its posterior surface; below, to the
tuberosity of the tibia; its superficial fibers are
continuous over the front of the patella with
those of the tendon of the Quadriceps femoris.
The medial and lateral portions of the tendon
of the Quadriceps pass down on either side of
the patella, to be inserted into the upper extremity
of the tibia on either side of the tuberosity ; these
portions merge into the capsule, as stated above,
forming the medial and lateral patellar retinacula. The posterior surface of the
ligamentum patella is separated from the synovial membrane of the joint by a
large infrapatellar pad of fat, and from the tibia by a bursa.
The Oblique Popliteal Ligament {ligamentum popliteum obliquum; posterior liga-
merit) (Fig. 346). — This ligament is a broad, flat, fibrous band, formed of fasciculi
separated from one another by apertures for the passage of vessels and nerves.
It is attached above to the upper margin of the intercondyloid fossa and posterior
surface of the femur close to the articular margins of the condyles, and below to
the posterior margin of the head of the tibia. Superficial to the main part of the
ligament is a strong fasciculus, derived from the tendon of the Semimembranosus
and passing from the back part of the medial condyle of the tibia obliquely upward
and lateralward to the back part of the lateral condyle of the femur. The oblique
popliteal ligament forms part of the floor of the popliteal fossa, and the popliteal
artery rests upon it.
Fig. 345. — Right knee-joint,
view.
Anterior
THE KNEE-JOINT
341
The Tibial Collateral Ligament (ligamentum coUaierale tibiale; internal lateral liga-
ment) (Fig. 345). — The tibial collateral is a broad, flat, membranous band, situated
nearer to the back than to the front of the joint. It is attached, above, to the medial
condyle of the femur immediately below the adductor tubercle; hclow, to the medial
condyle and medial surface of the body of the tibia. The fibers of the posterior
part of the ligament are short and incline backward as they descend; they are
inserted into the tibia above the groove for the Semimembranosus. The anterior
part of the ligament is a flattened band, about 10 cm. long, which inclines forward
as it descends. It is inserted into the medial surface of the body of the tibia about
2.5 cm. below the level of the condyle. It is crossed, at its lower part, by the
tendons of the Sartorius, Gracilis, and Semitendinosus, a bursa being interposed.
Its deep surface covers the inferior medial genicular vessels and nerve and the
anterior portion of the tendon of the Semimembranosus, with which it is connected
by a few fibers; it is intimately adherent to the medial meniscus.
Fig. 346. — Right knee-joint. Posterior view.
Fig. 347- — Right knee-joint, from the front,
showing interior ligaments.
The Fibular Collateral Ligament ijlgamentum coUaierale fihidare; external lateral or
long external lateral ligament) (Fig. 348) .-The fibular collateral is a strong rounded
fibrous cord, attached, above, to the back part of the lateral condyle of the emi^
immediatelv above the groove for the tendon of the Popliteus; Mow, to the latera
side of the head of the fibula, in front of the styloid process. The greater part of
its lateral surface is covered by the tendon of the Biceps Temoris; th^ tendon,
however, divides at its insertion into two parts, which are separated by the liga-
ment. Deep to the ligament are the tendon of the Popliteus, ^"d the infer o
lateral genicular vessels and nerve. The ligament has no attachment to the lateral
meniscus.
342
SYNDESMOLOGY
An inconstant bundle of fibers, the short fibular collateral ligament, is placed behind and
parallel with the preceding, attached, above, to the lower and back part of the lateral condyle
of the femur; below, to the summit of the stjdoid process of the fibula. Passing deep to it are
the tendon of the Popliteus, and the inferior lateral genicular vessels and nerve.
The Cruciate Ligaments {ligamenta cruciaia genu; crucial ligaments). — The cru-
ciate ligaments are of considerable strength, situated in the middle of the joint,
nearer to its posterior than to its anterior surface. They are called cruciate because
they cross each other somewhat like the lines of the letter X; and have received
the names anterior and posterior, from the position of their attachments to the
tibia.
■ The Anterior Cruciate Ligament {ligamentum cruciatum anterius; external crucial
ligament) (Fig. 347) is attached to the depression in front of the intercondyloid
eminence of the tibia, being blended with the anterior extremity of the lateral
meniscus; it passes upward, backward, and lateralward, and is fixed into the medial
and back part of the lateral condyle of the femur.
Ant. cniciateligament
Tendon of Po'pliteus
Lateral meniscus
Fibular collateral
ligament
Ligament of
Wrisberg
Medial me7iiscu3
Tibial collateral
ligament
Fig. 348. — l^eft knee-joint from behind, showing interior ligaments.
The Posterior Cruciate Ligament {ligamentum cruciatum jMsterius; internal crucial
ligament) (Fig. 348) is stronger, but shorter and less oblique in its direction, than
the anterior. It is attached to the posterior intercondyloid fossa of the tibia, and
to the posterior extremity of the lateral meniscus; and passes upward, forward,
and medialward, to be fixed into the lateral and front part of the medial condyle
of the femur.
The Menisci (semilunar fihrocartilages) (Fig. 349). — The menisci are two crescentic
lamellse, which serve to deepen the surfaces of the head of the tibia for articulation
with the condyles of the femur. The peripheral border of each meniscus is thick,
convex, and attached to the inside of the capsule of the joint ; the opposite border
THE KNEE-JOINT
343
is thin, concave, and free. The upper surfaces of the menisci are concave, and
in contact with the condyles of the femur; their lower surfaces are flat, and rest
upon the head of the tibia; both surfaces are smooth, and in\ested by synovial
membrane. Each meniscus covers approximately the peripheral two-thirds of
the corresponding articular surface of the tibia.
The medial meniscus {meniscus medialis; internal semilunar fihrocartilage) is
nearly semicircular in form, a little elongated from before backward, and broader
behind than in front; its anterior end, thin and pointed, is attached to the anterior
intercondyloid_ fossa of the tibia, in front of the anterior cruciate ligament; its
posterior end is fixed to the posterior intercondyloid fossa of the tibia, between
the attachments of the lateral meniscus and the posterior cruciate ligament.
Anterior cruciate ligament
Transverse ligament
Ligament of Wrisberg
Posterior cruciate ligament
F^G. 349. — Head of right tibia seen from above, showing menisci and attachments of ligaments.
The lateral meniscus {meniscus lateralis; external semilunar fihrocartilage) is nearly
circular and covers a larger portion of the articular surface than the medial one.
It is grooved laterally for the tendon of the Popliteus, Avhich separates it from the
fibular collateral ligament. Its anterior end is attached in front of the intercon-
dyloid eminence of the tibia, lateral to, and behind, the anterior cruciate ligament,
with which it blends; the posterior end is attached behind the intercondyloid
eminence of the tibia and in front of the posterior end of the medial meniscus.
The anterior attachment of the lateral meniscus is twisted on itself so that its
free margin looks backward and upward, its anterior end resting on a sloping
shelf of bone on the front of the lateral process of the intercondyloid eminence.
Close to its posterior attachment it sends off a strong fasciculus, the ligament of
Wrisberg (Figs. 348, 349), which passes upward and medialward, to be inserted
into the medial condyle of the femur, immediately behind the attachment of the
posterior cruciate ligament. Occasionally a small fasciculus passes forward to
be inserted into the lateral part of the anterior cruciate ligament. The lateral
meniscus gives off from its anterior convex margin a fasciculus which forms the
transverse ligament.
The Transverse Ligament {ligamentiim transversum genu). — The transverse liga-
ment connects the anterior convex margin of the lateral meniscus to the anterior
end of the medial meniscus; its thickness varies considerably in different subjects,
and it is sometimes absent.
The coronary ligaments are merely portions of the capsule, which connect the
periphery of each meniscus with the margin of the head of the tibia.
344
SYNDESMOLOGY
Synovial Membrane. — The synovial membrane of the knee-joint is the largest and most exten-
sive in the bod}\ Commencing at the upper border of the patella, it forms a large cul-de-sac
beneath the Quadriceps femoris (Figs. 350, 351) on the lower part of the front of the femur,
and frequently communicates with a bursa interposed between the tendon and the front of the
femur. The pouch of synovial membrane between the Quadriceps and front of the femur is
supported, during the movements of the knee, by a small muscle, the Articularis genu, which
is inserted into it. On either side of the pateUa, the synovial membrane extends beneath the
aponeuroses of the Vasti, and more especially beneath that of the Vastus medialis. Below the
patella it is separated from the ligamentum pateUse by a considerable quantity of fat, known as
Oblique popliteal
ligament
Medial meniscus
Adipose tissue
Bursa under Quadriceps
ffl.maris
Medial meniscus
Ligamentum patellae
Bursa between tibia and
ligamentum patelloB
Fio. 350. — Sagittal section of right knee-joint.
the infrapatellar pad. From the medial and lateral borders of the articular surface of the patella,
reduplications of the synovial membrane project into the interior of the joint. These form two
fringe-like folds termed the alar folds ; below, these folds converge and are continued as a single
band, the patellar fold (ligamentum mucosum), to the front of the intercondyloid fossa of the femur.
On either side of the joint, the synovial membrane passes downward from the femm-, lining the
capsule to its point of attachment to the menisci; it may then be traced over the upper surfaces
of these to their free borders, and thence along their under surfaces to the tibia (Figs. 351, 352).
At the back part of the lateral meniscus it forms a cul-de-sac between the groove on its surface
and the tendon of the PopUteus; it is reflected across the front of the cruciate ligaments, which
are therefore situated outside the synovial cavity.
THE KNEE-JOINT
345
Bursse.— The bursae near the knee-joint are the following: In front there ViVo. four bursa;- a
large one is interposed between the patella and the skin, a small one between the upper part of
the tibia and the hgartientum patella-, a third between the lower part of the tuberosity of the
tibia and the skin, and a fourth between the anterior surface of the lower part of the femur and
the deep surface of the Quadriceps femoris, usually communicating with the knee-joint. Laterally
there are four bursa;: (1) one (which sometimes communicates with the joint) between the
lateral head of the Gastrocnemius and the capsule; (2) one between the fibular collateral ligament
and the tendon of the Biceps; (3) one between the fibular collateral ligament and the tendon of
the Pophteus (tins is sometimes only an expansion from the next bursa) ; (4) one between the
tendon of the Popliteus and the lateral condyle of the femur, usually an extension from the
synovial membrane of the joint. Medially, there are five bursa;: (1) one between the medial
head of the Gastrocnemius and the capsule; this sends a prolongation between the tendon of the
Quadriceps
Jemoria
Fibular collateral
ligament
Tendon of Popliteus
Lateral meniscus
,„ — Ligamentum
'M patella-
FiQ. 351. — Capsule of right knee-joint (distended). Lateral aspect.
medial head of the Gastrocnemius and the tendon of the Semimembranosus and often communi-
cates with the joint; (2) one superficial to the tibial collateral ligament, between it and the tendons
of the Sartorius, Gracilis, and Semitendinosus; (3) one deep to the tibial collateral Ugament,
between it and the tendon of the Semimembranosus (this is sometimes only an expansion
from the next bursa) ; (4) one between the tendon of the Semimembranosus and the head of
the tibia; (5) occasionally there is a bursa between the tendons of the Semimembranosus and
Semitendinosus.
Structures Around the Joint. — In front, and at the sides, is the Quadriceps femoris; laterally
the tendons of the Biceps femoris and Popliteus and the common peroneal nerve; medially,
the Sartorius, Gracilis, Semitendinosus, and Semimembranosus; behind, the popUteal vessels
and the tibial nerve, Popliteus, Plantaris, and medial and lateral heads of the Gastrocnemius,
some lymph glands, and fat.
The arteries supplying the joint are the highest genicular (anastomotica magna), a branch
346
SYNDESMOLOGY
of the femoral, the genicular branches of the popliteal, the recurrent branches of the anterior
tibial, and the descending branch from the lateral femoral circumflex of the profunda femoris.
The nerves are derived from the obturator, femoral, tibial, and common peroneal.
Movements. — The movements which take place at the knee-joint are flexion and extension,
and, in certain positions of the joint, internal and external rotation. The movements of flexion
and extension at this joint differ from those in a typical hinge-joint, such as the elbow, in that
(a) the axis around which motion take^ place is not a fixed one, but shifts forward during extension
and backward during flexion; (b) the commencement of flexion and the end of extension are
accompanied by rotatory movements associated with the fixation of the limb in a position of
great stability. The movement from full flexion to full extension may therefore be described
in three phases:
1, In the fully flexed condition the posterior parts of the femoral condyles rest on the corre-
sponding portions of the meniscotibial surfaces, and in this position a sUght amount of simple
rolling movement is allowed.
Posterior cruciate
ligament
Medial meniscus
Tibial collateral
ligament
Anterior cruciate
ligament
Lateral meniscus
ibular collateral
ligament
Fia. 352. — Capsule of right knee-joint (distended). Posterior aspect.
2. During the passage of the limb from the flexed to the extended position a gliding movement
is superposed on the rolling, so that the axis, which at the commencement is represented by a
line through the inner and outer condyles of the femur, gradually shifts forward. In this part
of the movement, the posterior two-thirds of the tibial articular sm-faces of the two femoral
condyles are involved, and as these have similar curvatures and are parallel to one another, they
move forward equally.
3. The lateral condyle of the femur is brought almost to rest by the tightening of the anterior
cruciate ligament; it moves, however, slightly forward and medialward, pushing before it the
anterior part of the lateral meniscus. The tibial surface on the medial condyle is prolonged
farther forward than that on the lateral, and this prolongation is directed lateralward. When,
therefore, the movement forward of the condyles is checked by the anterior cruciate hgament,
continued muscular action causes the medial condyle, dragging with it the meniscus, to travel
backward and medialward, thus producing an internal rotation of the thigh on the leg. When
the position of full extension is reached the lateral part of the groove on the lateral condyle is
pressed against the anterior part of the corresponding meniscus, while the medial part of the
ARTICULATIONS BETWEEN THE TIBIA AND FIBULA 347
groove rests on the articular margin in front of the lateral process of the tibial intercondyloid
eminence. Into the groove on the medial condyle is fitted the anterior part of the medial meniscus,
while the anterior cruciate hgament and the articular margin in front of the medial process of
the tibial intercondyloid eminence are received into the forepart of the intercondyloid fossa of
the femur. This third phase by which all these parts are brought into accurate apposition is
known as the "screwing home," or locking movement of the joint.
The complete movement of flexion is the converse of that described above, and is therefore
preceded by an external rotation of the femur which unlocks the extended joint.
The axes around which the movements of flexion and extension take place are not precisely
at right angles to either bone; in flexion, the femur and tibia are in the same plane, but in exten-
sion the one bone forms an angle, opening lateralward with the other.
In addition to the rotatory movements associated with the completion of extension and the
initiation of flexion, rotation inward or outward can be effected when the joint is partially flexed;
these movements take place mainly between the tibia and the menisci, and are freest when the
leg is bent at right angles with the thigh.
Movements of Patella. — The articular surface of the patella is indistinctly divided into seven
facets — upper, middle, and lower horizontal pairs, and a medial perpendicular facet (Fig. 353).
When the knee is forcibly flexed, the medial perpendicular
facet is in contact with the semilunar surface on the lateral
part of the medial condyle; this semilunar surface is a pro-
longation backward of the medial part of the patellar surface.
As the leg is carried from the flexed to the extended position,
first the highest pair, then the middle pair, and lastly the
lowest pair of horizontal facets is successively brought into
contact with the patellar surface of the femur. In the ex-
tended position, when the Quadriceps femoris is relaxed, the
patella lies loosely on the front of the lower end of the femur.
During flexion, the ligamentum patellae is put upon
the stretch, and in extreme flexion the posterior cruciate
hgament, the obUque popliteal, and collateral Ugaments, ^ „ . , , ,
T , r Ui i i i-u J. ■ • X 1 • i Fig. 353— Posterior surface of the
and, to a slight extent, the anterior cruciate hgament, right patella, showing diagrammaticaUy
are relaxed. Flexion is checked during hfe by the contact ^}}% areas of contact with the femur in
f ,, , -,, ,, ,!.• 1 TTT. .1 1 • ■ i • r 11 different position? of the knee,
of the leg with the thigh. When the knee-joint is fuUy
extended the obhque pophteal and collateral ligaments,
the anterior cruciate ligament, and the posterior cruciate ligament, are rendered tense;
in the act of extending the knee, the ligamentum patella; is tightened by the Quadriceps
femoris, but in full extension with the heel supported it is relaxed. Rotation inward is checked
by the anterior cruciate ligament; rotation outward tends to uncross and relax the cruciate hga-
ments, but is checked by the tibial collateral hgament. The main function of the cruciate liga-
ment is to act as a direct bond between the tibia and femur and to prevent the former bone from
being carried too far backward or forward. They also assist the collateral hgaments in resisting
any bending of the joint to either side. The menisci are intended, as it seems, to adapt the surfaces
of the tibia to the shape of the femoral condj'les to a certain extent, so as to fill up the intervals
which would otherwise be left in the varying positions of the joint, and to obviate the jars which
would be so frequently transmitted up the hmb in jumping or by falls on the feet; also to permit
of the two varieties of motion, flexion and extension, and rotation, as explained above. The
patella is a great defence to the front of the knee-joint, and distributes upon a large and tolerably
even surface, during kneeling, the pressure which would otherwise fall upon the prominent ridges
of the condyles; it also affords leverage to the Quadriceps femoris.
When standing erect in the attitude of "attention," the weight of the body falls in front of
a line carried across the centers of the knee-joints, and therefore tends to produce overextension
of the articulations; this, however, is prevented by the tension of the anterior cruciate, oblique
pophteal, and collateral ligaments.
Extension of the leg on the thigh is performed by the Quadriceps femoris; flexion by the Biceps
femoris, Semitendinosus, and Semimembranosus, assisted by the GraciUs, Sartorius, Gastroc-
nemius, Pophteus, and Plantaris. Rotation outward is effected by the Biceps femoris, and rota-
tion inward by the Popliteus, Semitendinosus, and, to a shght extent, the Semimembranosus, the
Sartorius, and the GraciHs. The Pophteus comes into action especially at the commencement
of the movement of flexion of the knee; by its contraction the leg is rotated inward, or, if the
tibia be fixed, the thigh is rotated outward, and the knee-joint is unlocked.
in. Articulations between the Tibia and Fibula.
The articulations between the tibia and fibula are effected by ligaments which
connect the extremities and bodies of the bones. The ligaments may consequently
34S ' SYNDESMOLOGY
be subdivided into three sets: (1) those of the Tibiofibular articulation; (2) the
interosseous membrane; (3) those of the Tibiofibular syndesmosis.
Tibiofibular Articulation (articulatio Ubiofibidaris; superior tibiofibular articula-
tion).— This articulation is an arthrodial joint between the lateral condyle of the
tibia and the head of the fibula. The contiguous surfaces of the bones present
flat, oval facets covered with cartilage and connected together by an articular
capsule and by anterior and posterior ligaments.
The Articular Capsule (capsula articularis; capsular ligament). — The articular
capsule surrounds the articulation, being attached around the margins of the
articular facets on the tibia and fibula; it is much thicker in front than
behind.
The Anterior Ligament {anterior superior ligament). — The anterior ligament of
the head of the fibula (Fig. 347) consists of two or three broad and flat bands,
which pass obliquely upward from the front of the head of the fibula to the front
of the lateral condyle of the tibia.
The Posterior Ligament {posterior superior ligament). — The posterior ligament of
the head of the fibula (Fig. 348) is a single thick and broad band, which passes
obliquely upward from the back of the head of the fibula to the back of the lateral
condyle of the tibia. It is covered by the tendon of the Popliteus.
Synovial Membrane. — A sjmovial membrane lines the capsule; it is continuous with that of
the knee-joint in occasional cases when the two joints communicate.
Interosseous Membrane {membrana interossea cruris; middle tibiofibular liga-
ment).— An interosseous membrane extends between the interosseous crests of the
tibia and fibula, and separates the muscles on the front from those on the back
of the leg. It consists of a thin, aponeurotic lamina composed of oblique fibers,
which for the most part run downward and lateralward; some few fibers, however,
pass in the opposite direction. It is broader above than below. Its upper margin
does not quite reach the tibiofibular joint, but presents a free concave border,
above which is a large, oval aperture for the passage of the anterior tibial vessels
to the front of the leg. In its lower part is an opening for the passage of the anterior
peroneal vessels. It is continuous below with the interosseous ligament of the tibio-
fibular syndesmosis, and presents numerous perforations for the passage of small
vessels. It is in relation, in front, with the Tibialis anterior. Extensor digitorum
longus. Extensor hallucis proprius, Perona^us tertius, and the anterior tibial
vessels and deep peroneal nerve; behind, with the Tibialis posterior and Flexor
hallucis longus.
Tibiofibular Syndesmosis {syndesmosis tibiofibularis; inferior tibiofibular articu-
lation).— This syndesmosis is formed by the rough, convex surface of the medial
side of the lower end of the fibula, and a rough concave surface on the lateral side
of the tibia. Below, to the extent of about 4 mm. these surfaces are smooth, and
covered with cartilage, which is continuous with that of the ankle-joint. The
ligaments are: anterior, posterior, inferior transverse, and interosseous.
The Anterior Ligament {ligamentum malleoli lateralis anterius; anterior inferior
ligament). — The anterior ligament of the lateral malleolus (Fig. 355) is a flat,
triangular band of fibers, broader below than above, which extends obliquely
downward and lateralward between the adjacent margins of the tibia and fibula,
on the front aspect of the syndesmosis. It is in relation, in front, with the Peronseus
tertius, the aponeurosis of the leg, and the integument ; behind, with the interosseous
ligament; and lies in contact with the cartilage covering the talus.
The Posterior Ligament {ligamentum malleoli lateralis posterius; posterior inferior
ligament). — The posterior ligament of the lateral malleolus (Fig. 355), smaller
than the preceding, is disposed in a similar manner on the posterior surface of
the svndesmosis.
TALOCRURAL ARTICULATION OR ANKLE-JOINT
349
The Inferior Transverse Ligament. — The inferior transverse ligament lies in front
of the posterior ligament, and is a Strong, thick band, of yellowish fibers which
passes transversely across the back of the joint, from the lateral malleolus to the
posterior border of the articular surface of the tibia, almost as far as its malleolar
process. This ligament projects below the margin of the bones, and forms part
of the articulating surface for the talus.
The Interosseous Ligament. — The interosseous ligament consists of numerous
short, strong, fibrous bands, which pass between the contiguous rough surfaces of
the tibia and fibula, and constitute the chief bond of union between the bones.
It is continuous, above, with the interosseous membrane (Fig. 35G).
Synovial Membrane. — The synovial membrane associated with the small arthrodial part of
this joint is continuous with that of the ankle-joint.
IV. Talocrural Articulation or Ankle-joint (Articulatio Talocruralis ; Tibiotarsal
Articulation) .
The ankle-joint is a ginglymus, or hinge-joint. The structures entering into its
formation are the lower end of the tibia and its malleolus, the malleolus of the
^' Post, talotibial ligament
Medial talpcalcaneal lig.
Post, talocalcaneal lig.
1
1 !.
Articular capsule Medial cuneonavic. lig.
Calcaneocuboid ligament
Plantar calcaneonaoic.
liaarnent
Long plantar ligament
Fig. 354. — tigaments of the medial aspect of the foot. (Quain.)
fibula, and the transverse ligament, which together form a mortise for the recep-
tion of the upper convex surface of the talus and its medial and lateral facets.
The bones are connected by the following ligaments:
The Articular Capsule.
The Deltoid.
The Anterior Talofibular.
The Posterior Talofibular.
The Calcaneofibular.
350
SYNDESMOLOGY
The Articular Capsule (capsula articidaris; capsular ligament). — The articular cap-
sule surrounds the joints, and is attached, above, to the borders of the articular
surfaces of the tibia and malleoli; and below, to the talus around its upper articular
surface. The anterior part of the capsule {anterior ligament) is a broad, thin,
membranous layer, attached, above, to the anterior margin of the lower end of
the tibia; below, to the talus, in front of its superior articular surface. It is in
relation, in front, with the Extensor tendons of the toes, the tendons of the Tibialis
anterior and Peronj^tus tertius, and the anterior tibial vessels and deep peroneal
nerve. The posterior part of the capsule (posterior ligament) is very thin, and
consists principally of transverse fibers. It is attached, above, to the margin of the
articular surface of the tibia, blending with the transverse ligament; below, to the
talus behind its -superior articular facet. Laterally, it is somewhat thickened, and
is attached to the hollow on the medial surface of the lateral malleolus.
Ant. lat. jnalleol. lig
Post. lat. malleol. lig._
Dorsal talonavic. lia.
XCalcaneonaiic. Tparl\^.. , ,.
, I Calcaneocuboid part]^'^'^'"^^^ ^^^
j I I Dorsal cuboideonavic. lig.
Dorsal navicular cuneif. lig. ■
/ Dorsal cuneocuboid lig.
' \Dorsal intercuneif. lig.
/^/ Dorsal tarsometat. lia
Post, talofibular lig. _
J plantar Hi,,
jinteros. talocalcan. lig.
Ant. talofibular lig.
Dorsal intermet. lig.
Dorsal tarsomet. lig.
Calcaneo fibular lig.
Fig. 355. — The ligaments of the foot from the lateral aspect, (t^uain.)
The Deltoid Ligament (ligameninm deltoideum; internal lateral ligament)
(Fig. 331). — The deltoid ligament is a strong, flat, triangular band, attached,
above, to the apex and anterior and posterior borders of the medial malleolus.
It consists of two sets of fibers, superficial and deep. Of the superficial fibers the
most anterior {tibionavicular) pass forward to be inserted into the tuberosity of
the navicular bone, and immediately behind this they blend with the medial margin
of the plantar calcaneonavicular ligament; the middle {calcaneotibial) descend
almost perpendicidarly to be inserted into the whole length of the sustentaculum
tali of the calcaneus; the posterior fibers {posterior talotibial) pass backward and
lateralward to be attached to the inner side of the talus, and to the prominent
TALOCRURAL ARTICULATION OR ANKLE-JOINT
351
tubercle on its posterior surface, medial to the groove for the tendon of the Flexor
hallucis longus. The deep fibers {anterior talotibial) are attached, above, to the
tip of the medial malleolus, and, beloiv, to the medial surface of the talus. The
deltoid ligament is covered by the tendons of the Tibialis posterior and Flexor
digitorum longus.
The anterior and posterior talofibular and the calcaneofibular ligaments were
formerly described as the three fasciculi of the external lateral ligament of the
ankle-joint.
The Anterior Talofibular Ligament {ligamentum talofibulare anterius) (Fig. 355).
— The anterior talofibular ligament, the shortest of the three, passes from the
anterior margin of the fibular malleolus, forward and medially, to the talus, in
front of its lateral articular facet.
The Posterior Talofibular Ligament {ligamentum talofibulare jjosterius) (Fig. 355).
— The posterior talofibular ligament, the strongest and most deeply seated, runs
almost horizontally from the depression at the medial and back part of the fibular
malleolus to a prominent tubercle on the posterior surface of the talus immediately
lateral to the groove for the tendon of the Flexor hallucis longus.
The Calcaneofibular Ligament {ligamentum calcaneofibulare) (Fig. 355). — The
calcaneofibular ligament, the longest of the three, is a narrow, rounded cord, run-
ning from the apex of the fibular malleolus downward and slightly backward to a
tubercle on the lateral surface of the calcaneus. It is covered by the tendons of
the Peronffii longus and brevis.
Anterior talofibular lifjament
Posterior talofibular ligament
Calcaneofibular ligamrnt
Lateral talocalcaneal ligament
Anterior
talocalcaneal
ligament
Fig. 356. — Capsule of left talocrura articulation (distended). Lateral aspect.
Synovial Membrane (Fig. 356). — The synovial membrane invests the deep surfaces of the
ligaments, and sends a small process upward between the lower ends of the tibia and fibula.
Relations.— The tendons, vessels, and nerves in connection with the joint are, in front, from the
medial side, the Tibiahs anterior. Extensor hallucis proprius, anterior tibial vessels, deep peroneal
nerve. Extensor digitorum longus, and Peronseus tertius; behind, from the medial side, the Tibialis
posterior, Flexor digitorum longus, posterior tibial vessels, tibial nerve, Flexor haUucis longus;
and, in the groove behind the fibular malleolus, the tendons of the Perona^i longus and brevis.
The arteries supplying the joint are derived from the malleolar branches of the anterior tibial
and the peroneal.
The nerves are derived from the deep peroneal and tibial.
Movements.— When the body is in the erect position, the foot is at right angles to the leg.
The movements of the joint are those of dorsiflexion and extension; dorsiflexion consists in the
352 SYNDESMOLOGY
approximation of the dorsum of the foot to the front of the leg, while in extension the heel is
drawn up and the toes pointed downward. The range of movement varies in different individuals
from about 50° to 90°. The transverse axis about which movement takes place is slightly oblique.
The malleoli tightly embrace the talus in all positions of the joint, so that any slight degree of
side-to-side movement which may exist is simply due to stretching of the hgaments of the talo-
fibular syndesmosis, and slight bending of the body of the fibula. The superior articular surface
of the talus is broader in front than behind. In doisiflexion, herefore, greater space is required
between the two malleoli. This is obtained by a slight outward rotatory movement of the lower
end of the fibula and a stretching of the ligaments of the syndesmosis ; this lateral movement is
facilitated by a slight ghding at the tibiofibular articulation, and possibly also by the bending of
the body of the fibula. Of the ligaments, the deltoid is of very great power — so much so, that
it usually resists a force which fractures the process of bone to which it is attached. Its middle
portion, together with the calcaneofibular hgament, binds the bones of the leg firmly to the
foot, and resists displacement in every direction. Its anterior and posterior fibers limit extension
and flexion of the foot respectively, and the anterior fibers also limit abduction. The posterior
talofibular ligament assists the calcaneofibular in resisting the displacement of the foot back-
ward, and deepens the cavity for the reception of the talus. The anterior talofibular is a
security against the displacement of the foot forward, and hmits extension of the joint.
The movements of inversion and eversion of the foot, together with the minute changes in
form by which it is applied to the ground or takes hold of an object in climbing, etc., are mainly
effected in the tarsal joints; the joint which enjoys the greatest amount of motion being that be-
tween the talus and calcaneus behind and the navicular and cuboid in front. This is often called
the transverse tarsal joint, and it can, with the subordinate joints of the tarsus, replace the ankle-
joint in a great measure when the latter has become ankylosed.
Extension of the foot upon the tibia and fibula is produced by the Gastrocnemius, Soleus,
Plantaris, Tibialis posterior, Perona-i longus and brevis. Flexor digitorum longus, and Flexor
hallucis longus; dorsiflexion, by the Tibialis anterior, Peronaius tertius. Extensor digitorum longus,
and Extensor hallucis proprius.^
V. Intertarsal Articulations (Articulationes Intertarseae ; Articulations
of the Tarsus).
Talocalcaneal Articulation {articulatio talocalcanea; articulation of the calcaneus
and astragalus; calcaneo-astragaloid articulation). — The articulations between the
calcaneus and talus are two in number^ — anterior and posterior. Of these, the
anterior forms part of the talocalcaneonavicular joint, and will be described with
that articulation. The posterior or talocalcaneal articulation is formed between
the posterior calcaneal facet on the inferior surface of the talus, and the posterior
facet on the superior surface of the calcaneus. It is an arthrodial joint, and the
two bones are connected by an articular capsule and by anterior, posterior, lateral,
medial, and interosseous talocalcaneal ligaments.
The Articular Capsule (capsula articularis) .■ — The articular capsule envelops
the joint, and consists for the most part of short fibers, which are split up into
distinct slips; between these there is only a weak fibrous investment.
The Anterior Talocalcaneal Ligament {lig amentum talocalcaneum anterius; anterior
calcaneo-astragaloid ligament) (Figs. 356, 359). — The anterior talocalcaneal liga-
ment extends from the front and lateral surface of the neck of the talus to
the superior surface of the calcaneus. It forms the posterior boundary of the
talocalcaneonavicular joint, and is sometimes described as the anterior interosseous
ligament.
The Posterior Talocalcaneal Ligament {ligamentum talocalcaneum posterius;
posterior calcaneo-astragaloid ligament) (Fig. 354). — The posterior talocalcaneal
ligament connects the lateral tubercle of the talus with the upper and medial part
of the calcaneus; it is a short band, and its fibers radiate from their narrow attach-
ment to the talus.
The Lateral Talocalcaneal Ligament {ligamentum talocalcaneum laterale; external
calcaneo-astragaloid ligament) (Figs. 356, 359). — The lateral talocalcaneal ligament
1 The student must bear in mind that the Extensor digitorum longus and Extensor hallucis proprius are extensors
of the toes, but flexors of the ankle; and that the Flexor digitorum longus and Flexor hallucis longus are flexors of the
toes, but extensors of the ankle.
INTERTARSAL ARTICULATIONS
353
is a short, strong fasciculus, passing from the lateral surface of the talus, imme-
diately beneath its fibular facet to the lateral surface of the calcaneus. It is placed
in front of, but on a deeper plane than, the calcaneofibular ligament, with the fibers
of which it is parallel.
The Medial Talocalcaneal Ligament (ligamentum talocalcaneum mediale; internal
calcaneo-astragaloid ligament) .—The medial talocalcaneal ligament connects the
medial tubercle of the back of the talus with the back of the sustentaculum tali.
Its fibers blend with those of the plantar calcaneonavicular ligament (Fig. 354).
Medial matleolus
Deltoid ligament
Tibialis posterior
flexor digitorum longus'
Flexor hallucis lotigus
Med. plantar nerve and vessel
Quadratus plantce
Abductor hallucis
Lat. plantar nerve and vessels
Flexor digitorum brevis
Interosseous ligament of tibio
fibular syndesmosis
Lateral malleolus
Calcaneofibular ligament
Interosseous talocalcaneal
ligament
Peronoeus brevis
Peronceus longtis
Abductor digiti quinti
Fio. .357. — Coronal section through right talocrural and talocalcaneal joints.
The Interosseous Talocalcaneal Ligament {ligamentum talocalcaneum inierosseum)
(Figs. 357, 359). — The interosseous talocalcaneal ligament forms the chief bond
of union between the bones. It is, in fact, a portion of the united capsules of the
talocalcaneonavicular and the talocalcaneal joints, and consists of two partially
united layers of fibers, one belonging to the former and the other to the latter joint.
It is attached, above, to the groove between the articular facets of the under surface
of the talus; below, to a corresponding depression on the upper surface of the cal-
caneus. It is very thick and strong, being at least 2.5 cm. in breadth from side
to side, and serves to bind the calcaneus and talus firmly together.
Synovial Membrane (Fig. 360). — The synovial membrane lines the capsule of the joint, and
is distinct from the other synovial membranes of the tarsus.
Movements. — The movements permitted between the talus and calcaneus are limited to glid-
ing of the one bone on the other backward and forward and from side to side.
Talocalcaneonavicular Articulation (articulatio talocalcnneonancularis). — This
articulation is an arthrodial joint: the rounded head of the talus being received
into the concavity formed by the posterior surface of the navicular, the anterior
articular surface of the calcaneus, and the upper surface of the plantar calcaneo-
23
354 SYXDESMOLOGY
navicular ligament. There are two ligaments in this joint: the articular capsule
and the dorsal talonavicular.
The Articular Capsule {capsula ariicularis) . — The articular capsule is imperfectly
developed except posteriorly, where it is considerably thickened and forms, with
a part of the capsule of the talocalcaneal joint, the strong interosseous ligament
which fills in the canal formed by the opposing grooves on the calcaneus and talus,
as above mentioned.
The Dorsal Talonavicular Ligament {ligamentum talonaviculare dorsale; superior
astragalonavicular ligament) (Fig. 354). — This ligament is a broad, thin band, which
connects the neck of the talus to the dorsal surface of the navicular bone; it is
covered by the Extensor tendons. The plantar calcaneonavicular supplies the
place of a plantar ligament for this joint.
Synovial Membrane. — The synovial membrane lines all parts of the capsule of the joint.
Movements. — Tliis articulation permits of a considerable range of gliding movements, and some
rotation; its feeble construction allows occasionally of dislocation of the other bones of the tarsus
from the talus.
Calcaneocuboid Articulation {articulatio calcaneocuboidea; articulation of the
calcaneus with the cuboid). — The ligaments connecting the calcaneus with the
cuboid are five in number, viz., the articular capsule, the dorsal calcaneocuboid,
part of the bifurcated, the long plantar, and the plantar calcaneocuboid.
The Articular Capsule (capsula articularis). — The articular capsule is an imper-
fectly developed investment, containing certain strengthened bands, which form
the other ligaments of the joint.
The Dorsal Calcaneocuboid Ligament (ligamentum calcaneocuhoideum dorsale; supe-
rior calcaneocuboid ligament) (Fig. 355). — The dorsal calcaneocuboid ligament is
a thin but broad fasciculus, which passes between the contiguous surfaces of the
calcaneus and cuboid, on the dorsal surface of the joint.
The Bifurcated Ligament (ligamentum bifurcatum; ijiternal calcaneocuboid; inter-
osseous ligament) (Fig. 355, 359). — The bifurcated ligament is a strong band,
attached behind to the deep hollow on the upper surface of the calcaneus and divid-
ing in front in a Y-shaped manner into a calcaneocuboid and a calcaneonavicular
part. The calcaneocuboid part is fixed to the medial side of the cuboid and forms
one of the principal bonds between the first and second rows of the tarsal bones.
The calcaneonavicular part is attached to the lateral side of the navicular.
The Long Plantar Ligament (ligamentum plantare longum; long calcaneocuboid
ligament; superficial long plantar ligament) (Fig. 358). — The long plantar ligament
is the longest of all the ligaments of the tarsus: it is attached behind to the plantar
surface of the calcaneus in front of the tuberosity, and in front to the tuberosity
on the plantar surface of the cuboid bone, the more superficial fibers being con-
tinued forward to the bases of the second, third, and fourth metatarsal bones.
This ligament converts the groove on the plantar surface of the cuboid into a
canal for the tendon of the Peronteus longus.
The Plantar Calcaneocuboid Ligament (ligamentum calcaneocuboideum plantare;
short calca)ieocuboid ligament; short plantar ligament) (Fig. 358).- — The plantar
calcaneocuboid ligament lies nearer to the bones than the preceding, from which
it is separated by a little areolar tissue. It is a short but wide band of great strength,
and extends from the tubercle and the depression in front of it, on the forepart
of the plantar surface of the calcaneus, to the plantar surface of the cuboid behind
the peroneal groove.
Synovial Membrane. — The synovial membrane lines the inner surface of the capsule and is
distinct from that of the other tarsal articulations (Fig. 360).
Movements. — The movements permitted between the calcaneus and cuboid are limited to
slight gliding movements of the bones upon each other.
The transverse tarsal joint is formed by the articulation of the calcane.is with the cuboid, and
INTERTARSAL ARTICULATIONS
355
the articulation of the talus with the navicular. The movement which takes place in this joint
is more extensive than that in the other tarsal joints, and consists of a sort of rotation by means
of which the foot may be slightly flexed or extended, the sole being at the same time carried
medially (.inverted) or laterally (everted).
The Ligaments Connecting the Calcaneus and Navicular.— Though the calcaneus
and na^•icula^ do not directly articulate, they are connected by two ligaments:
the calcaneonavicular part of the bifurcated, and the plantar calcaneonavicular.
The calcaneonavicular part of the bifurcated ligament is described on page 354.
Plantar intcrmetatar. lig-.-M-X.
Plantar calcaneocub. lig. — ;
Tendon peroncms longus
muscle
Long plantar ligament
Tendon peronceus
^ longus muscle
^-■'Plantar tarsometatar . lig.
Tendon tibialis anticus
muscle
Plantar cuneonavic. lig.
Plantar cuhoideonavic.
ligament
Plantar calcaneonavic.
ligament
Tendon tibialis posticus
muscle
Fig. 358.— Ligaments of the sole of the foot, with the tendons of tlie.Peronaeus longus, Tibialis posterior and Tibialis
anterior muscles. (Quain.)
The Plantar Calcaneonavicular Ligament {ligamentum calcaneonaviculare flantare;
inferior or internal calcaneonavicular ligament; calcaneonavicular ligament) (Figs.
354, 35<S).— The plantar calcaneonavicular ligament is a broad and thick band of
fibers, which connects the anterior margin of the sustentaculum tali of the calca-
neus to the plantar surface of the navicular. This ligament not only serves to
connect the calcaneus and navicular, but supports the head of the talus, formmg
35G
SYNDESMOLOGY
part of the articular cavity in which it is received. The dorsal surface of the
ligament presents a fibrocartilaginous facet, lined by the synovial membrane,
and upon this a portion of the head of the talus rests. Its plantar surface is
supported by the tendon of the Tibialis posterior; its medial border is blended with
the forepart of the deltoid ligament of the ankle-joint.
Lateral
ialocalcaneal
ligament
Anterior
talocnlcaneal
ligament
Tibialis
'posterior
Interosseous
ialocalcaneal
ligament
Fig. 359. — Talocalcaneal and talocalcaneonavicular articulations exposed from above by removing the talus.
The plantar calcaneonavicular ligament, by supporting the head of the talus, is principally
concerned in maintaining the arch of the foot. When it yields, the head of the talus is pressed
downward, medialward, and forward by the weight of the body, and the foot becomes flattened,
expanded, and turned lateralward, and exhibits the condition known as flat-foot. This ligament
contains a considerable amount of elastic fibers, so as to give elasticity to the arch and spring
to the foot; hence it is sometimes called the "spring" ligament. It is supported, on its plantar
surface, by the tendon of the Tibialis posterior, which spreads out at its insertion into a number
of fasciculi, to be attached to most of the tarsal and metatarsal bones. This prevents undue
stretching of the ligament, and is a protection against the occurrence of flat-foot; hence muscular
weakness is, in most cases, the primary cause of the deformity.
Cuneonayicular Articulation (articidatio cuneonavicularis ; articulation of the
navicular with the cuneiform hones). — The navicular is connected to the three
cuneiform bones by dorsal and plantar ligaments.
The Dorsal Ligaments {ligamenta navicularicuneijormia dorsalia). — The dorsal
ligaments are three small bundles, one attached to each of the cuneiform bones.
The bundle connecting the navicular with the first cuneiform is continuous around
the medial side of the-articulation with the plantar ligament which unites these
two bones (Figs. 354, 355) .
The Plantar Ligaments (ligamenta navicularicuneiformia plantaria). — The plantar
ligaments have a similar arrangement to the dorsal, and are strengthened by slips
from the tendon of the Tibialis posterior (Fig. 358).
Synovial Membrane. — The synovial membrane of these joints is part of the great tarsal synovial
membrane (Fig. 360).
Movements. — Mere gUding movements are permitted between the navicular and cuneiform
bones.
Cuboideonavicular Articulation. — The navicular bone is connected with the
cuboid by dorsal, plantar, and interosseous ligaments.
INTERTARSAL ARTICULATIONS
357
The Dorsal Ligament {ligameutum cuboideonaviculare dorsale) .—The dorsal ligament
extends obliquely forward and lateralward from the navicular to the cuboid bone
(Fig. 355).
The Plantar Ligament {ligamentum cuboideonaoiculare plantare) .—The plantar
ligament passes nearly transversely between these two bones (Fig. 358).
The Interosseous Ligament.— The interosseous ligament consists of strong trans-
verse fibers, and connects the rough non-articular portions of the adjacent surfaces
of the two bones Fig. 360).
Synovial Membrane.— The synovial membrane of this joint is part of the great tarsal synovial
membrane (Fig. 360).
Movements.— The movements pel-mitted betvsreen the navicular and cuboid bones are limited
to a shght gliding upon each other.
Deltoid
ligament
'/M^J^' Talofibular
^^"^^^ .^k ligament
j| Tnterosseous
talocalcaneal
ligament
Metatarsals
Fig. 360. — Oblique section of left intertarsal and tarsometatarsal articulations, showing the synovial cavities.
Intercuneiform and Cuneocuboid Articulations. — The three cuneiform bones and
the cuboid are connected together by dorsal, plantar, and interosseous ligaments.
The Dorsal Ligaments (ligamenta intercuneiformia dorsalia). — The dorsal liga-
ments consist of three transverse bands: one connects the first with the second
cuneiform, another the second with the third cuneiform, and another the third
cuneiform with the cuboid.
The Plantar Ligaments {ligamenta intercuneiformia plantaria). — The plantar liga-
ments have a similar arrangement to the dorsal, and are strengthened by slips
from the tendon of the Tibialis posterior.
The Interosseous Ligaments {ligamenta intercuneiformia interossea). — The inter-
osseous ligaments consist of strong transverse fibers which pass between the rough
non-articular portions of the adjacent surfaces of the bones (Fig. 300).
358 SYNDESMOLOGY
Sjmovial Membrane. — The synovial membrane of these joints is part of the great tarsal synovial
membrane (Fig. 360).
Movements. — The movements permitted between these bones are limited to a slight gliding
upon each other.
VI. Tarsometatarsal Articulations (Articulationes Tarsometatarsese) .
These are arthrodial joints. The bones entering into their formation are the
first, second, and third cuneiforms, and the cuboid, which articulate with the bases
of the metatarsal bones. The first metatarsal bone articulates with the first cunei-
form; the second is deeply wedged in between the first and third cuneiforms
articulating by its base with the second cuneiform; the third articulates with the
third cuneiform; the fourth, with the cuboid and third cuneiform; and the fifth,
with the cuboid. The bones are connected by dorsal, plantar, and interosseous
ligaments.
The Dorsal Ligaments (ligamenta tarsometatarsea dorsalia) . — The dorsal ligaments
are strong, flat bands. The first metatarsal is joined to the first cuneiform by a
broad, thin band; the second has three, one from each cuneiform bone; the third
has one from the third cuneiform; the fourth has one from the third cuneiform
and one from the cuboid; and the fifth, one from the cuboid (Figs. 354, 355).
The Plantar Ligaments {ligamenta tarsometatarsea plantaria). — The plantar liga-
ments consist of longitudinal and oblique bands, disposed with less regularity
than the dorsal ligaments. Those for the first and second metatarsals are the
strongest; the second and third metatarsals are joined by oblique bands to the
first cuneiform; the fourth and fifth metatarsals are connected by a few fibers
to the cuboid (Fig. 358).
The Interosseous Ligaments {ligamenta cuneometatarsea interossia). — The inter-
osseous ligaments are three in number. The first is the strongest, and passes from
the lateral surface of the first cuneiform to the adjacent angle of the second meta-
tarsal. The second connects the third cuneiform with the adjacent angle of the
second metatarsal. The third connects the lateral angle of the third cuneiform
with the adjacent side of the base of the third metatarsal.
Sjmovial Membrane (Fig. 360). — The synovial membrane between the first cuneiform and
the first metatarsal forms a distinct sac. The synovial membrane between the second and third
cuneiforms behind, and the second and third metatarsal bones in front, is part of the great tarsal
sjTiovial membrane. Two prolongations are sent forward from it, one between the adjacent sides
of the second and third, and another between those of the third and fourth metatarsal bones.
The synovial membrane between the cuboid and the fourth and fifth metatarsal bones forms a
distinct sac. From it a prolongation is sent forward between the fomlh and fifth metatarsal bones.
Movements. — The movements permitted between the tarsal and metatarsal bones are hmited
to shght gliding of the bones upon each other.
Nerve Supply. — The intertarsal and tarsometatarsal joints are suppUed by the deep peroneal
nerve.
Vn. Intermetatarsal Articulations (Articulationes Intermetatarseae) .
The base of the first metatarsal is not connected with that of the second by any
ligaments; in this respect the great toe resembles the thumb.
The bases of the other four metatarsals are connected by the dorsal, plantar,
and interosseous ligaments.
The Dorsal Ligaments {ligamenta barium [oss. metatars.] dorsalia) pass transversely
between the dorsal surfaces of the bases of the adjacent metatarsal bones.
The Plantar Ligaments {ligamenta basiiim [oss. metatars] plantaria).- — The plantar
ligaments have a similar arrangement to the dorsal.
The Literosseous Ligaments {ligamenta barium [oss. metatars.] interossea). — The
interosseous ligaments consist of strong transverse fibers which connect the rough
non-articular portions of the adjacent surfaces.
ARTICULATIONS OF THE DIGITS 359
Synovial Membranes (Fig. 360).— The synovial membranes between the second and third,
and the third and fourth metatarsal bones are part of the great tarsal synovial membrane; that
between the fourth and fifth is a prolongation of the synovial membrane of the cuboideometatarsal
joint.
Movements.— The movement permitted between the tarsal ends of the metatarsal bones
is hmited to a slight gliding of the articular surfaces upon one another.
The heads of all the metatarsal bones are connected together by the transverse
metatarsal ligament.
The Transverse Metatarsal Ligament.— The transverse metatarsal ligament is a
narrow band which runs across and connects together the heads of all the meta-
tarsal bones; it is blended anteriorly with the plantar (glenoid) ligaments of the
metatarsophalangeal articulations. Its plantar surface is concave where the
Flexor tendons run below it; above it the tendons of the Interossei pass to their
insertions. It differs from the transverse metacarpal ligament in that it connects
the metatarsal to the others.
The Synovial Membranes in the Tarsal and Tarsometatarsal Joints (Fig. 360). — The synovial
membranes foinul in the articulations of the tarsus and metatarsus are six in number: one for
the talocalcaneal articulation; a second for the talocalcaneonavicular articulation; a third for
the calcaneocuboid aiticulation; and a fourth for the cuneonavicular, intercuneiform, and cuneo-
cuboid articulations, the articulations of the second and third cuneiforms with the bases of the
second and third metatarsal bones, and the adjacent surfaces of the bases of the second, third,
and fourth metatarsal bones; a fifth for the first cuneiform with the metatarsal bone of the great
toe; and a sixth for the articulation of the cuboid with the fourth and fifth metatarsal bones.
A small synovial cavity is sometimes found between the contiguous surfaces of the navicular
and cuboid bones.
VIII. Metatarsophalangeal Articulations (Articulationes Metatarsophalangeae) .
The metatarsophalangeal articulations are of the condyloid kind, formed by
the reception of the rounded heads of the metatarsal bones in shallow cavities
on the ends of the first phalanges.
The ligaments are the plantar and two collateral.
The Plantar Ligaments (ligamenta accessoria plantaria; glenoid ligaments of Cru-
veilhier). — The plantar ligaments are thick, dense, fibrous structures. They are
placed on the plantar surfaces of the joints in the intervals between the collateral
ligaments, to which they are connected; they are loosely united to the metatarsal
bones, but very firmly to the bases of the first phalanges. Their plantar surfaces
are intimately blended with the transverse metatarsal ligament, and grooved for
the passage of the Flexor tendons, the sheaths surrounding which are connected
to the sides of the grooves. Their deep surfaces form part of the articular facets
for the heads of the metatarsal bones, and are lined by synovial membrane.
The Collateral Ligaments (ligamenta collateralia; lateral ligaments). — The collat-
eral ligaments are strong, rounded cords, placed one on either side of each joint,
and attached, by one end, to the posterior tubercle on the side of the head of the
metatarsal bone, and, by the other, to the contiguous extremity of the phalanx.
The place of dorsal ligaments is supplied by the Extensor tendons on the dorsal
surfaces of the joints.
Movements. — The movements permitted in the metatarsophalangeal articulations are flexion,
extension, abduction, and adduction.
IX. Articulations of the Digits (Articulationes Digitorum Pedis; Articulations of
the Phalanges).
The interphalangeal articulations are ginglymoid joints, and each has a plantar
and two collateral ligaments.
The arrangement of these ligaments is similar to that in the metatarsophalangeal
articulations; the Extensor tendons supply the places of dorsal ligaments.
360 SYNDESMOLOGY
Movements. — The only movements permitted in the joints of the digits are flexion and exten-
sion; these movements are more extensive between the first and second phalanges than between
the second and third. The amoimt of flexion is very considerable, but extension is Umited by the
plantar and collateral ligaments.
Arches of the Foot.
In order to allow it to support the weight of the body in the erect posture with
the least expenditure of material, the foot is constructed of a series of arches
formed by the tarsal and metatarsal bones, and strengthened by the ligaments
and tendons of the foot.
The main arches are the antero-posterior arches, which may, for descriptive
purposes, be regarded as divisible into two types — a medial and a lateral. The
medial arch (see Fig. 290, page 276) is made up by the calcaneus, the talus, the
navicular, the three cuneiforms, and the first, second, and third metatarsals. Its
summit is at the superior articular surface of the talus, and its two extremities or
piers, on which it rests in standing, are the tuberosity on the plantar surface of
the calcaneus posteriorly and the heads of the first, second, and third metatarsal
bones anteriorly. The chief characteristic of this arch is its elasticity, due to its
height and to the number of small joints between its component parts. Its weakest
part, i. e., the part most liable to yield from overpressure, is the joint between
the talus and navicular, but this portion is braced by the plantar calcaneonavicular
ligament, which is elastic and is thus able to quickly restore the arch to its pristine
condition when the disturbing force is removed. The ligament is strengthened
medially by blending with the deltoid ligament of the ankle-joint, and is supported
inferiorly by the tendon of the Tibialis posterior, which is spread out in a fan-
shaped insertion and prevents undue tension of the ligament or such an amount
of stretching as would permanently elongate it. The arch is further supported by
the plantar aponeurosis, by the small muscles in the sole of the foot, by the tendons
of the Tibialis anterior and posterior and PeroUtTeus longus, and by the ligaments
of all the articulations involved. The lateral arch (see Fig. 291, page 277) is com-
posed of the calcaneus, the cuboid, and the fourth and fifth metatarsals. Its
summit is at the talocalcaneal articulation, and its chief joint is the calcaneocuboid,
which possesses a special mechanism for locking, and allows only a limited move-
ment. The most marked features of this arch are its solidity and its slight eleva-
tion; two strong ligaments, the long plantar and the plantar calcaneocuboid,
together with the Extensor tendons and the short muscles of the little toe, preserve
its integrity.
While these medial and lateral arches may be readily demonstrated as the
component antero-posterior arches of the foot, yet the fundamental longitudinal
arch is contributed to by both, and consists of the calcaneus, cuboid, third cunei-
form, and third metatarsal : all the other bones of the foot may be removed without
destroying this arch.
In addition to the longitudinal arches the foot presents a series of transverse
arches. At the posterior part of the metatarsus and the anterior part of the tarsus
the arches are complete, but in the middle of the tarsus they present more the
characters of half-domes the concavities of which are directed downward and
medialward, so that when the medial borders of the feet are placed in apposition
a complete tarsal dome is formed. The transverse arches are strengthened by the
interosseous, plantar, and dorsal ligaments, by the short muscles of the first and
fifth toes (especially the transverse head of the Adductor hailucis), and by the
Peronseus longus, whose tendon stretches across between the piers of the arches.
BIBLIOGRAPHY.
R. Fick: Handbuch der Anatomie und Mechanik der Gelenke (Bardeleben 's Handbuch der
Anatomie).
myology;
rpHE Muscles are connected with the bones, cartilages, ligaments, and skin,
J- either directly, or through the intervention of fibrous' structures called tendons
or aponeuroses. Where a muscle is attached to bone or cartilage, the fibers end
in blunt extremities upon the periosteum or perichondrium, and do not come into
direct relation with the osseous or cartilaginous tissue. Where muscles are con-
nected with its skin, they lie as a flattened layer beneath it, and are connected
with its areolar tissue by larger or smaller bundles of fibers, as in the muscles of
the face.
The muscles vary extremely in their form. In the limbs, they are of considerable
length, especially the more superficial ones; they surround the bones, and constitute
an important protection to the various joints. In the trunk, they are broad,
flattened, and expanded, and assist in forming the walls of the trunk cavities.
Hence the reason of the terms, long, broad, short, etc,, used in the description of a
muscie.
There is considerable variation in the arrangement of the fibers of certain muscles
with reference to the tendons to which they are attached. In some muscles the
fibers are parallel and run directly from their origin to their insertion; these are
quadrilateral muscles, such as the Thyreohyoideus. A modification of these is
found in the fusiform muscles, in which the fibers are not quite parallel, but slightly
curved, so that the muscle tapers at either end; in their actions, however, they
resemble the quadrilateral muscles. Secondly, in other muscles the fibers are
convergent; arising by a broad origin, they converge to a narrow or pointed inser-
tion. This arrangement of fibers is found in the triangular muscles — e. g., the
Temporalis. In some muscles, which otherwise would belong to the quadrilateral
or triangular type, the origin and insertion are not in the same plane, but the plane
of the line of origin intersects that of the line of insertion; such is the case in the
Pectineus. Thirdly, in so^ae muscles {e. g., the Peronei) the fibers are oblique and
converge, like the plumes of a quill pen, to one side of a tendon which runs the entire
length of the muscle; such muscles are termed unipennate. A modification of this
condition is found where oblique fibers converge to both sides of a central tendon;
these are called bipennate, and an example is afforded in the Rectus femoris.
Finally, there are muscles in which the fibers are arranged in curved bundles in
one or more planes, as in the Sphincters. The arrangement of the fibers is of con-
siderable importance in respect to the relative strength and range of movement
of the muscle. Those muscles where the fibers are long and few in number have
great range, but diminished strength; where, on the other hand, the fibers are
short and more numerous, there is great power, but lessened range.
The names applied to the various muscles have been derived: (1) from their
situation, as the Tibialis, Radialis, Ulnaris, Peronwus; (2) from their direction, as
the Rectus abdominis, Obliqui capitis, Transversus abdominis; (3) from their uses,
as Flexors, Extensors, Abductors, etc.; (4) from their shape, as the Deltoideus,
' The muscles and fascise are described conjointly, in order that the student may consider the arrangement of the
latter in his dissection of the former. It is rare for the student of anatomy in this country to have tlie opportunity
of dissecting the fasciae separately; and it is for this reason, as well as from the close connection that exists between
the muscles and their investing sheaths, that they are considered together. Some general observations are first made
on the anatomy of the muscles and fasciae, the special descriptions being given in connection with the dififerent regions
(361)
362 MYOLOGY
Rhomboideus; (5) from the number of their divisions, as the Biceps and Triceps;
(G) from theirpointsof attachment, as the Sternocleidomastoideus, Sternohyoideus,
Sternothyreoideus.
In the description of a muscle, the term origin is meant to imply its more fixed
or central attachment; and the term insertion the movable point on which the force
of the muscle is applied ; but the origin is absolutely fixed in only a small number
of muscles, such as those of the face which are attached by one extremity to immov-
able bones, and by the other to the movable integument; in the greater number,
the muscle can be made to act from either extremity.
In the dissection of the muscles, attention should be directed to the exact origin,
insertion, and actions of each, and to its more important relations with surrounding
parts. AVhile accurate knowledge of the points of attachment of the muscles is
of great importance in the determination of their actions, it is not to be regarded
as conclusive. The action of the muscle deduced from its attachments, or even
by pulling on it in the dead subject, is not necessarily its action in the living. By
pulling, for example, on the Brachioradialis in the cadaver the hand may be slightly
supinated when in the prone position and slightly pronated when in the supine
position, but there is no evidence that these actions are performed by the muscle
during life. It is impossible for an individual to throw into action any one muscle;
in other words, movements, not muscles, are represented in the central nervous
system. To carry out a movement a definite combination of muscles is called into
play, and the individual has no power either to leave out a muscle from this com-
bination or to add one to it. One (or more) muscle of the combination is the chief
moA'ing force; when this muscle passes over more than one joint other muscles
(synergic muscles) come into play to inhibit the movements not required; a third
set of muscles (fixation muscles) fix the limb — i. e., in the case of the limb-movements
■ — and also prevent disturbances of the equilibrium of the body generally. As an
example, the movement of the closing of the fist may be considered: (1) the prime
movers are the Flexores digitorum. Flexor pollicis longus, and the small muscles
of the thumb; (2) the synergic muscles are the Extensores carpi, which prevent
flexion of the wrist; while (3) the fixation muscles are the Biceps and Triceps
brachii, which steady the elbow and shoulder. A further point which must be
borne in mind in considering the actions of muscles is that in certain positions
a movement can be effected by gravity, and in such a case the muscles acting are
the antagonists of those which might be supposed to be in action. Thus in flexing
the trunk when no resistance is interposed the Sacrospinales contract to regulate
the action of gravity, and the Recti abdominis are relaxed.^
By a consideration of the action of the muscles, the surgeon is able to explain
the causes of displacement in various forms of fracture, and the causes which pro-
duce distortion in various deformities, and, consequently, to adopt appropriate
treatment in each case. The relations, also, of some of the muscles, especially
those in immediate apposition with the larger bloodvessels, and the surface mark-
ings they produce, should be remembered, as they form useful guides in the
application of ligatures to those vessels.
MECHANICS OF MUSCLE.^
In studying the mechanical action of muscles the individual muscle cannot
always be treated as a single unit, since different parts of the same muscle may
have entirely different actions, as with the Pectoralis major, the Deltoid, and the
Trapezius where the ner\e mipulses control and stimulate different portions of the
1 Consult in this connection the Croonian Lectures (1903) on "Muscular Movements and Their RepresentMion in
.the Central Nervous System," by Charles E. Beevor, M.D.
- R Fick. Bd ii, iu Bardeleben's Handbuch der Anatomic des Menschen.
MECHANICS OF MUSCLE
363
muscle ill succession or at different times. Most muscles are, however, in a mechanical
sense units. But in either case the muscle fibers constitute the elementary motor
elements.
Fig. 361
The Direction of the Muscle Pull. — In those muscles where the fibers always run
in a straight line from origin to insertion in all positions of the joint, a straight line
joining the middle of the surface of origin with the middle of the insertion surface
Fig. 362
will give the direction of the pull (Fig. 361). If, however, the muscle or its tendon
is bent out of a straight line by a bony process or ligament so that it runs over a
pulley-like arrangement, the direction of the muscle pull is naturally bent out of
\
Fig. 363
line. The direction of the pull in such cases is from the middle point of insertion
to the middle point of the pulley where the muscle or tendon is bent. ISIuscles or
tendons of muscles which pass o^•e^ more than one joint and pass through more than
364
MYOLOGY
y"
one pulley may be resolved, so far as the direction of the pull is concerned, into two
or more units or single-joint muscles (Fig. 362). The tendons of the Flexor pro-
fundus digitorum, for example, pass through several pulleys formed by fibrous
sheaths. The direction of the pull is different for each joint and varies for each
joint according to the position of the bones. The direction is determined in each
case, however, by a straight line between the centers of the pulleys on either side of
the joint (Fig. 363). The direction of the pull in any of the segments would not
be altered by any change in the position or origin of the muscle belly above the
proximal pulley.
The Action of the Muscle Pull on the Tendon. — Where the muscle fibers are parallel
or nearly parallel to the direction of the tendon the entire strength of the muscle
contraction acts in the direction of the tendon.
In pinnate muscles, however, only a portion of the strength of contraction is effi-
cient in the direction of the tendon, since a portion of the pull would tend to draw
the tendon to one side, this is mostly annulled by pressure of surrounding parts.
In bipiimate muscles this lateral pull is counterbalanced. If, for example, the muscle
fibers are inserted into the tendon at an angle of 60
degrees (Fig. 364), it is easy to determine by the
parallelogram of forces that the strength of the pull
along the direction of the tendon is equal to one-half
the muscle pull.
T = tendon, m — strength and direction of muscle
pull.
t — component acting in the direction of the
tendon.
^ = angle of insertion of muscle fibers into tendon.
/
cos 0
0.5 = —
If
The more acute the angle <A, that is the smaller
the angle, the greater the component acting in the
direction of the tendon pull. At 41° 20' three-fourths
of the pull would be exerted in the direction of the
tendon and at 0° the entire strength. On the other
hand, the greater the angle the smaller the tendon component; at 72° 30' one-third
the muscle strength would act in the direction of the tendon and at 90° the tendon
component would be nil.
The Strength of Muscles. — The strength of a muscle depends upon the number of
fibers in what is knowTi as the physiological cross-section, that is, a section which
passes through practically all of the fibers. In a muscle with parallel or nearly
parallel fibers which have the same direction as the tendon this corresponds to the
anatomical cross-section, but in unipinnate and bipinnate muscles the physiological
cross-section may be nearly at right angles to the anatomical cross-section as shown
in Fig. 365. wSince Huber has showm that muscle fibers in a single fasciculus of a
given muscle vary greatly in length, in some fasciculi from 9 mm. to 30.4 mm., it
is unlikely that the physiological cross-section will pass through all the fibers.
Estimates have been made of the strength of muscles and it is probable that coarse-
fibered muscles are somewhat stronger per square centimeter of physiological
m
cos
z
G0° = 0.50000
t
m
t = h
VI
Z cl> =
72° 30'
cos = 1
Z 0 =
41° 20'
cos = f
Z 0 =
90°
cos = 0
Z (l> =
0°
cos = 1
Fig. 364
MECHANICS OF MUSCLE
365
cross-section than are the fine-fibered muscles. Fick estimates the average strength
as about 10 kg. per square cm. This is known as the absolute muscle strength.
The total strength of a muscle Avoukl be equal to the number of square centimeters
in its physiological cross-section X 10 kg.
Ml//.
—PCS
PCS
B C
Fig. 365. — A, fusiform; B, unipinnate; C, bipinnate; P.C.S., physiological cross-section.
The Work Accomplished by Muscles. — For practical uses this should be expressed
in kilogranuneters. In order to reckon the amount of work which a muscle can
perform under the most favorable conditions it is necessary to know (1) its physio-
logical cross-section (2) the maximum shortening, and (3) the position of the joint
when the latter is obtained.
Work = lifted weight X height through which the weight is lifted; or
Work = tension X distance; tension = physiological cross-section X absolute
muscle strength.
If a muscle has a physiological cross-section of 5 sq. cm. its tension strength =
5X10 or 50 kg. If it shortens 5 cm. the work = 50 X .05 = 2.5 kilogrammeters.
If one determines then the physiological cross-section and multiplies the absolute
muscle strength, 10 kg. by this, the amount of tension is easily obtained. Then
one must determine only the amount of shortening of the muscle for any particular
position of the joint in order to determine the amount of work the muscle can do,
since work = tension X distance.
The tension of a muscle is, howev?r, not constant during the course of contraction
but is continually decreasing during contraction. It is at a maximmn at the begin-
ning and gradually decreases.
This can be illustrated by the work diagram P'ig. 366.
A M D (ordinate) = tension.
A V X (abscissa) = shortening.
A D = tension of muscle in extended or antagonistic position.
A V ^ amount of actual shortening.
A M = tension in midposition = absolute muscle strength.
D V ^ shows how the tension sinks from maximum (in the extended position of
the muscle) where it is about double that in the midposition (M) to
nothing on complete contraction.
366
MYOLOGY
A -I D V = work diagram, in reality the hypothenose is not straight but has a
concave curve. The A has the same area as the rectangle .4 M M' V.
A M = the average tension.
Work = .1 M X A V kilogrammeters if the size of the ordinate as expressed in
kilograms and the abscissa in meters.
^ SHORTENfNG
Fig. 366
Although the muscle works with a changing tension, yet the accomplishment is
the same as if it were contracting with the tension of- the midposition.
In reality the amount of work is somewhat greater since even in extreme con-
traction the muscle still retains a certain amount of tension so that the maximum
amount of work is more nearly like .1 D X. We know that a muscle may have
an extreme actual shortening of about SO per cent, of its length when the tendon
of insertion is cut.
The trapezoid A D S V represents more nearly the amount of work, but since
there are only approximate values and ADS T"is not much larger than A M M' T,
we ma\' use the latter.
Only the tension and amount of shortening are needed to determine the amount
of work of the vmsde. Neither the lever arm nor t\ie fiber angle in pinnate muscles
need be considered.
The diagram Fig. 307 shows that the lerer arm is of no importance for deter-
mining the amount of work the muscle performs.
J B and J B^ — two bones jointed at J. CD and E F = the direction of the pull
of two muscles of equal cross-section, each having a muscle tension of lOlM) gms.
The centers of the attachments are such that perpendiculars J c and J c to
C D and E F are equal to 40 and 23 mm. respectively, J c = 40 mm. and J e =
23 mm. The static moments are equal to 1000 X 40 and 1000 X 23, therefore the
first muscle can hold a much larger load {D on the bone J B^ at W (,100 mm. from
J) than the second muscle whose load can be designated as D.
Equilibrium exists for the first muscle if
i X 100 = 1000 X 40 or i = ^^^i!^ "^^^ = 400 gms.
100
For the second muscle D XlOO = 1000 X 23.
1000 X 23
D =
100
= 230 gms.
If we suppose J £ to be fixed and J B^ to move in the plane of the paper about
J and the muscle C D to shorten 5 mm. C d = C D — o mm. and with the tension
of 1000 gms., J B^ will take the position J B- and the load {L) will be lifted from
H' to H'-.
MECHANICS OF MUSCLE
367
If the second muscle likewise shortens 5 mm. then E f = E F — ') mm., and
with the tension of 1000 gms. the bone J B^ will take the position J B^ and the
weight or load (D) will be lifted from W to H^. The question now is to prove
that the work done is the same in both cases, namelv, 5 X 1000 grammillimeters.
If so. 400 X H' H- = 230 X H' W ^ 5000 grammillimeters.
Since the two radii C d and C d' are very long as compared with the arc d d' we
may consider this short arc as a line J_ to C D at d', likewise the arc//' may be
considered as a straight line J_toEF. In the same manner we can consider the
short arcs F f, D d, H' IP and W W \_ to the line J B\ The sides B d' and Ff
of the A D d d' and F ff are each 5 mm.
The lever arm D J = GO mm. and J F = SO mm.
Fig. 367
The A D d d' is similar to the A D c J
hence D d
60 : 40
Dd =
also H'lP : Dd :: 100 : 60
300
H'H-
100 : 60 W H- =
300
40
300
40 •• ^ "" " " 24
The A Fff is similar to F e J
150
hence F /
30 : 23
also IFH' -.Ff :: 100 : 30
WH':^:: 100: 30 IF H' =
23
23
1500
69
300 1500 .,,,,,,
.'. 400 X -TT = -'30 X -775- = oOOO
24 69 ...
Thus we see that the work of the two muscles depends on the size ot the contrac-
tion and on the tension and not on the lever arm in very small contractions or m
368
MYOLOGY
the summation of such contractions and therefore for large contractions. In the
first muscle a large load is moved through a short distance and in the second muscle
a lighter load is moved through a greater distance.
The amount of work accomplished by pinnate muscles is not dependent upon
the angle of insertion of the muscle fibers into the tendon, as will be seen by the
following diagram Fig. 368.
direction of the tendon pull,
direction of muscle fiber before con-
traction.
= direction of muscle fiber after contrac-
tion.
= amount of contraction.
= tension of the muscle.
<j) = angle of insertion of muscle fiber,
t = tendon component = m X cos (j) =
the weight carried by the tendon
to balance the muscle tension.
d = distance tendon is drawn up.
(!) m X V = work done by the muscle fiber.
(2) / X d = work done by the movement of
the tendon.
If we consider the distance v as being very
short then the line b c can be dealt with as
though it were perpendicular to a c.
7 7 ^
= a X cos (f) or a =
r T
IV a
m'
V
m
then
V
since / = m X cos </> or m
t
cos 4>
t
m X V =
cos 4>
X d X cos cj) = t X d
o
Fig. 368
COS z 60° = ^; hence /
cos <f>
If this is true for very minute contractions it
is likewise true for a series of such contraction
and hence for larger contractions.
If we assume that 0 = 60°, m = 10 kg. and v
= 5 mm., the work done by the contracting
muscle fiber = m v or 10 X 5 kilogrammilli-
meters.
§ m; and d = ^ == 2 v; ^ m = 5 kg.; and 2 v = 10 mm.
hence / rf = 50 kilogrammillimeters or the work done by the movement of the
tendon in lifting the load of 5 kg. a distance of 10 mm., and is exactly the same as
that done by the muscle fiber. The load on the tendon is but one-half the tension
of the muscle, but the distance through which the load is lifted is twice that of the
amount of shortening of the muscle.
If <^ = 41° 20' then cos <^ = f
hence t = f ?7i and d = ^ v and t d = m v
In pinnate muscles, then, we have the rather unexpected condition in which
the same amount of movement of the tendon can be accomplished with less contrac-
tion of the muscle than in muscles where the fibers have the same direction as the
tendon.
The Action of Muscles on Joints. — If we consider now the action of a single muscle
extending over a single joint in which one bone is fixed and the other movable, we
MECHANICS OF MUSCLE
369
will find that muscle pull can be resolved into two components, a turninf; com-
ponent and a friction or pressure component as showai in Fig. 369.
K
Fig. 369
D F == the fixed bone from which the muscle takes its origin.
D K = the movable bone.
01 = a line from the middle of origin to the middle of insertion.
I M = size and direction of the muscle pull.
If the parallelogram is constructed with / t and M b j_to D K, then I I = the
turning component and I h = the component which acts against the joint.
The size of the two components depends upon the insertion angle (/>. The smaller
this angle the smaller the turning component, and the nearer this angle <*) is to
90° the larger the turning component.
I / = 7 J/ X sin </>
7 6 = 7 .1/ X cos (^
If <t> = 90°
hence I b = 0
If 0 = 0°
hence 7 6 = 1
cos <^ = 0, sine 4>
and 1 1 = I m
cos 4> — 1, sine <t>
and 7^ = 0
= 1
= 0
With movements of the bone 7) K the angle of insertion is continually changing,
and hence the two components are changing in value.
Fig
If, for example, the distance from origin 0 to the joint 7) is greater than from
7) to 7, as in the Brachialis or Biceps muscles, the turning component increases until
the insertion angle 0 = 90°, which is the optimum angle for muscle action, while
the pressure: component gradually decreases. If the movement continues beyond
24
370
MYOLOGY
this point the turning component gradually decreases and the pressure component
changes into a component which tends to draw the two bones apart and which
gradually increases as shoA^ni in Fig. 370.
AVhen the bone D K is in such a position that the insertion angle <^ = 41° 20'
the pressure component = ^ I m and the turning component I I m, at 60° the two
components are equal, at 90° the pressure component = 0 and the turning com-
ponent = / M and at 131° 21' the pressure component has been converted into a
pulling component = I I M and the turning component = | / M.
If, for example, the distance from the origin 0 to the joint D is less than the dis-
tance from the insertion / to the joint D, as in the Brachioradialis muscle, the
insertion angle increases with the flexion but never reaches 90°. The turning
component gradually increases to a certain point and then slowly decreases as shown
in Fig. 371, while the pressure component gradually decreases and then slowly
increases. It always remains large and its action is always in the direction of the
joint.
Levers.^ — The majority of the muscles of the body act on bones as the power on
levers. Levers of the III class are the most common, as the action of the Biceps,
and the Brachialis muscles on the forearm bones. Levers of the I Class are found
in movements of the head where the occipito-atlantal joint acts as the fulcrum and
the muscles on the back of the neck as the power. Another conuuon example is
w
n
A
S
w
:k
w
n
n
lU
Fig. 372
the foot when one raises the body by contracting the Gastrocnemius and Soleus.
Here the ankle-joint acts as the fulcrum and the pressure of the toes on the ground
as the weight. This is frequently, thougli wTongly, considered a lever of the II Class.
If one were to stand on one's head with the legs up and with a weight on the plantar
surface of the toes, it is easy to see that we would have a lever of the I Class if the
weight were raised by contraction of the Gastrocnemius muscle. The confusion
has arisen by not considering the fact that the fulcrum and the power in all three
classes of levers must have a common basis of action, as showni in Fig. 3*2.
DEVELOPMENT OF THE MUSCLES ' 371
If the fulcrum rests on the earth the power must either directly or indirectly
push from the earth or be attached to the earth either by jjravity or otherwise if it
pulls toward the earth. If the power were attached to the weight no lever action
could be obtained.
There are no levers of the II Class represented in the body.
DEVELOPMENT OF THE MUSCLES.
Both the cross-striated and smooth muscles, with the exception of a few that are
of ectodermal origin, arise from the mesoderm. The intrinsic muscles of the trunk
are derived from the myotomes while the muscles of the head and limbs differentiate
directly from the mesoderm.
The Myotomic Muscles. — The intrinsic muscles of the trunk which are derived
directly from the myotomes are conveniently treated in two groups, the deep
muscles of the back and the thoraco-abdominal muscles.
The deep muscles of the back extend from the sacral to the occipital region and
vary much in length and size. They act chiefly on the vertebral cohnnn. The
shorter muscles, such as the Interspinales, Intertransversarii, the deeper layers of
the ]Multifidus, the Rotatores, Levatores costarum, Obliquus capitis inferior,
Obliquus capitis superior and Rectus capitis posterior minor which extend between
adjoining vertebra?, retain the primitive segmentation of the myotomes. Other
muscles, such as the Splenius capitis, Splenius cervicis, Sacrospinalis, Semispinalis,
Multifidus, Iliocostalis, Longissimus, Spinales, Semispinales, and Rectus capitis
posterior major, which extend over several vertebrae, are formed by the fusion of
successive myotomes and the splitting into longitudinal columns.
The fascia lumbo-dorsalis de^'elops between the true myotomic muscles and the
more superficial ones which migrate over the back such as the Trapezius, Rhom-
boideus, and Latissimus.
The anterior vertebral muscles, the Longus colli, Longus capitis. Rectus capitis
anterior and Rectus capitis lateralis are derived from the ventral part of the cervical
myotomes as are probably also the Scaleni.
The thoraco-abdominal muscles arise through the ventral extension of the
thoracic myotomes into the body wall. This process takes place coincident with the
ventral extension of the ribs. In the thoracic region the primitive myotomic
segments still persist as the intercostal muscles, but over the abdomen these ventral
myotomic processes fuse into a sheet which splits in various ways to form the
Rectus, the Obliquus externus and internus, and the Transversalis. Such muscles
as the Pectoralis major and minor and the Serratus anterior do not belong to the
above group.
The Ventrolateral Muscles of the Neck. — The intrinsic muscles of the tongue, the
Infrahyoid muscles and the diaphragm are derived from a more or less continuous
premuscle mass which extends on each side from the tongue into the lateral region
of the upper half of the neck and into it early extend the hypoglossal and branches
of the upper cervical nerA'cs. The two halves which form the Infrahyoid muscles
and the diaphragm are at first widely separated from each other by the heart.
As the latter descends into the thorax the diaphragmatic portion of each lateral
mass is carried with its nerve down into the thorax and the laterally placed Infra-
hyoid muscles move toward the midventral line of the neck.
Muscles of the Shoulder Girdle and Arm.— The Trapezius and Sternocleidomas-
toideus arise from a common premuscle mass in the occipital region just caudal to
the last branchial arch; as the mass increases in size it spreads downward to the
shoulder girdle to which it later becomes attached. It also spreads backward and
downward to the spinous processes, gaining attachment at a still later period.
372 MYOLOGY
The Levator scapulfe, Serratiis anterior and the Rhomboids arise from premuscle
tissue in the lower cervical region and undergo extensive migration.
The Latissimus dorsi and Teres major are associated in their origin from the
premuscle sheath of the arm as are also the two Pectoral muscles when the arm
bud lies in the lower cervical region.
The intrinsic muscles of the arm develop in situ from the mesoderm of the arm
bud and probably do not receive cells or buds from the myotomes. The ner\es
enter the arm bud when it still lies in the cervical region and as the arm shifts
caudally over the thorax the lower cervical nerves which unite to form the brachial
plexus, acquire a caudal direction.
The Muscles of the Leg. — The muscles of the leg like those of the arm develop
in situ from the mesoderma of the leg bud, the myotomes apparently taking no
part in their formation.
The Muscles of the Head. — The muscles of the orbit arise from the mesoderm over
the dorsal and caudal sides of the optic stalk.
The muscles of mastication arise from the mesoderm of the mandibular arch.
The mandibular division of the trigeminal nerve enters this premuscle mass before
it splits into the Temporal, IMasseter and Pterygoideus.
The facial muscles (muscles of expression) arise from the mesoderm of the hyoid
arch. The facial ner^'e enters this mass before it begins to split, and as the muscle
mass spreads out over the face and head and neck it splits more or less incompletely
into the various muscles.
The early differentiation of the muscular system apparently goes on independ-
ently of the nervous system and only later does it appear that muscles are dependent
on the functional stimuli of the nerves for their continued existence and growth.
Although the nervous system does not influence muscle differentiation, the nerves,
owing to their early attachments to the muscle rudiments, are in a general way
indicators of the position of origin of many of the muscles and likewise in many
instances the nerves indicate the paths along which the developing muscles have
migrated during development. The muscle of the diaphragm, for example, has its
origin in the region of the fourth and fifth cervical segments. The phrenic nerve enters
the muscle mass Avhile the latter is in this region and is drawn out as the diaphragm
migrates through the thorax. The Trapezius and Sternocleidomastoideus arise
in the lateral occipital region as a common muscle mass, into which at a very early
period the nervus accessorius extends and as the muscle mass migrates and extends
caudally the nerve is carried with it. The Pectoralis major and minor arise in the
cervical region, receive their nerves while in this position and as the muscle mass
migrates and extends caudally over the thorax the nerves are carried along. The
Latissimus dorsi and Serratus anterior are excellent examples of migrating muscles
whose nerve supply indicates their origin in the cervical region. The Rectus
abdominis and the other abdominal muscles migrate or shift from a lateral to a
ventrolateral or abdominal position, carrying with them the nerves.
The facial nerve, which early enters the common facial muscle mass of the second
branchial or hyoid arch, is dragged about with the muscle as it spreads over the head
and face and neck, and as the muscle splits into the various muscles of expression,
the nerve is correspondingly split. The mandibular division of the trigeminal nerve
enters at an early time the muscle mass in the mandibular arch and as this mass
splits and migrates apart to form the muscles of mastication the nerve splits into
its various branches.
The nerve supply then serves as a key to the common origin of certain groups of
muscles. The muscles supplied by the oculomotor nerve arise from a single mass
in the eye region; the lingual muscles arise from a common mass supplied by the
hypoglossal nerve.
DEVELOPMENT OF THE MUSCLES
373
Striped or Voluntary Muscle. — Striped or voluntary muscle is composed of bundles
of fibers each enclosed in a delicate web called the perimysium in contradistinction
to the sheath of areolar tissue Avhich invests the entire muscle, the epimysium.
The bundles are termed fasciculi; they are prismatic in shape, of different sizes
in different muscles, and are for the most part placed parallel to one another,
though they have a tendency to converge toward their tendinous attachments.
Each fasciculus is made up of a strand of fibers, which also run parallel with each
other, and are separated from one another by a delicate connective tissue derived
from the perimysium and termed endomysium. This does not form the sheath
of the fibers, but serves to support the bloodvessels and nerves ramifying between
them.
A muscular fiber may be said to consist of a soft contractile substance, enclosed
in a tubular sheath named by Bowman the sarcolemma. The fibers are cylindrical
or prismatic in shape (Fig. 373), and are of no great length, not exceeding, as a rule,
40 mm. Huber' has recently found that the muscle fibers in the adductor muscle
of the thigh of the rabbit vary greatly in length even in the same fasciculus. In a
fasciculus 40 mm. in length the fibers varied from 30.4 mm. to 9 mm. in length.
Their breadth varies in man from 0.01 to 0.1 mm. As a rule, the fibers do not
Fig. 373. — Transverse section of human striped muscle fibers.
X 2.55.
Fig 374. — Striped muscle fibers from tongue of
cat. X 250.
divide or anastomo.se; but occasionally, especially in the tongue and facial mus-
cles, they may be seen'to divide into several branches. In the substance of the
muscle, the fibers end by tapering extremities which are joined to the ends of
other fibers by the sarcolemma. At the tendinous end of the muscle the sarco-
lemma appears to blend with a small bundle of fibers, into which the tendon
becomes subdivided, while the muscular substance ends abruptly and can be
readily made to retract from the point of junction. The areolar tissue between
the fibers appears to be prolonged more or less into the tendon, so as to form a kind
of sheath around the tendon bundles for a longer or shorter distance. When
muscular fibers are attached to skin or mucous membranes, their fibers become
continuous with those of the areolar tissue.
The sarcolemma, or tubular sheath of the fiber, is a transparent, elastic, and
apparently homogeneous membrane of considerable toughness, so that it some-
times remains entire when the included substance is ruptured. On the mternal
surface of the sarcolemma in mammalia, and also in the substance of the fiber
in frogs, elongated nuclei are seen, and in connection with these is a little granular
protoplasm. . , ,. ,
Upon examination of a voluntary muscular fiber by transmitted light, it is
lAnat. Rec, 1916, 11.
374
MYOLOGY
found to be marked by alternate light and dark bands or striae, which pass trans-
versely across the fiber (Fig. 374). When examined by polarized light the
dark bands are found to be doubly refracting (anisotropic), while the clear
stripes are singly refracting (isotropic) . The dark and light bands are of nearly
equal breadth, and alternate with great regularity; they vary in breadth from about
1 to 2/i. If the surface be carefully
focussed, rows of granules will be de-
tected at the points of junction of the
dark and light bands, and very fine
longitudinal lines may be seen run-
ning through the dark bands and
joining these granules together. By
treating the specimen with certain
reagents (e. g., chloride of gold) fine
lines may be seen running transversely
between the granules and uniting them
together. This appearance is believed
to be due to a reticulum or network
of interstitial substance lying between
the contractile portions of the muscle.
The longitudinal striation gives the
fiber the appearance of being made
up of a bundle of fibrils which have
been termed sarcostyles or muscle
columns, and if the fiber be hardened
in alcohol, it can be broken up longitu-
dinally and the sarcostyles separated
from each other (Fig. 375.) The retic-
ulum, with its longitudinal and trans-
verse meshes, is called sarcoplasm.
In a transverse section, the muscular fiber is seen to be divided into a number
of areas, called the areas of Cohnheim, more or less polyhedral in shape and con-
sisting of the transversely divided sarcostyles, surrounded by transparent sarco-
plasm (Fig. 373).
Fig. 375. — A. Portion of a medium-sized human muscular
fiber. Magnified nearl.v 800 diameters. B. Separated bundles
of fibrils, equally magnified, a. a. Larger, and b. h, smaller
collections, c. Still smaller, d, d. The smallest which could
be detached.
--H
S.E.
B
Fia. 376. — Diagram of a sarcomere, (.\fter Schafer.) A. In moderately extended condition. B. In a contracted
condition, k, k. Membranes of Krause. H. Line or jilane of Hensen. S.E. Poriferous sarcous element.
Upon closer examination, and by somewhat altering the focus, the appearances
become more complicated, and are susceptible of various interpretations. The
transverse striation, which in Fig. 374 appears as a mere alternation of dark and
light bands, is resolved into the appearance seen in Fig. 375, which shows a series
of broad dark bands, separated by light bands, each of which is divided into two
t
1
:>
ij
DEVELOPMENT OF THE MUSCLES 375
by a dark dotted line. This line is termed Dobie's line or Krause's membrane
(Fig. 370, k), because it was believed by Krause to be an actual membrane, con-
tinuous with the sarcolemma, and dividing the light band into two compartments.
In addition to the membrane of Krause, fine clear lines may be made out, with a
sufficiently high power, crossing the center of the dark band; these are known as
the lines of Hensen (Fig. 376, H).
Schafer has worked out the minute anatomy of muscular fiber, particularly in
the wing muscles of insects, which are peculiarly adapted for this purpose on
account of the large amount of interstitial sarcoplasm which separates the sarco-
styles. In the following description that given by Schafer will be closely followed.
A sarcostyle may be said to be made up of successive portions, each of which
is termed a sarcomere. The sarcomere is situated between two membranes of Krause
and consists of (1) a central dark part, which forms a portion of the dark band
of the whole fiber, and is named a sarcous element. This sarcous element really
consists of two parts, superimposed one on the top of the other, and when the fiber
is stretched these two parts become separated from each other at the line of Hensen
(Fig. 376, A). (2) On either side of this central dark portion is a clear layer, most
visible when the fiber is extended; this is situated between the dark center and the
membrane of Krause, and when the sarcomeres are joined together to form the
sarcostyle, constitutes the light band of the striated muscular fiber.
When the sarcostyle is extended, the clear intervals are well-marked and plainly
to be seen; when, on the other hand, the sarcostyle is contracted, that is to say,
when the muscle is in a state of contraction, these clear portions are very small
or they may have disappeared altogether (Fig. 376, B). When the sarcostyle is
stretched to its full extent, not only is the clear portion well-marked, but the dark
portion — the sarcous element — is separated into its two constituents along the
line of Hensen. The sarcous element does not lie free in the sarcomere, for when
the sarcostyle is stretched, so as to render the clear portion visible, very fine
lines, which are probably septa, may be seen running through it from the sarcous
element to the membrane of Krause.
Schafer explains these phenomena in the following way: He considers that each
sarcous element is made up of a number of longitudinal channels, which open
into the clear part toward the membrane of Krause but are closed at the line of
Hensen. When the muscular fiber is contracted the clear part of the muscular
substance is driven into these channels or tubes, and is therefore hidden from
sight, but at the same time it swells up the sarcous element and widens and shortens
the sarcomere. When, on the other hand, the fiber is extended, this clear sub-
stance is driven out of the tubes and collects between the sarcous element and
the membrane of Krause, and gives the appearance of the light part between
these two structures; by this means it elongates and narrows the sarcomere.
If this view be true, it is a matter of great interest, and, as Schafer has shown,
harmonizes the contraction of muscle with the ameboid action of protoplasm.
I In an ameboid cell, there is a framework of spongioplasm, which stains with
hematoxylin and similar reagents, enclosing in its meshes a clear substance, hyalo-
plasm, which will not stain with these reagents. Under stimulation the hyaloplasm
passes into the pores of the spongioplasm; without stimulation it tends to pass
out as in the formation of pseudopodia. In muscle there is the same thing, viz.,
a framework of spongioplasm staining with hematoxylin — the substance of the
sarcous element — and this encloses a clear hyaloplasm, the clear substance of
the sarcomere, which resists staining with this reagent. During contraction of the
muscle — i. e., stimulation — this clear substance passes into the pores of the spongio-
plasm; while during extension of the muscle — i. e., when there is no stimulation —
it tends to pass out of the spongioplasm.
In this way the contraction is brought about: under stimulation the proto-
378 MYOLOGY
plasmic material (the clear substance of the sarcomere) recedes into the sarcous
element, causing the sarcomere to widen out and shorten. The contraction of the
muscle is merely the sum total of this widening out and shortening of these bodies.
Vessels and Nerves of Striped Muscle. — ^The capillaries of striped muscle are
very abundant, and form a sort of rectangular network, the branches of which run
longitudinally in the endomysium between the muscular fibers, and are joined at
short intervals by transverse anastomosing branches. In the red muscles of the
rabbit dilatations occur on the transverse branches of the capillary network. The
larger vascular channels, arteries and veins, are found only in the perimysium,
between the muscular fasciculi. Nerves are profusely distributed to striped muscle.
Their mode of termination is described on page 730. The existence of Ijnnphatic
vessels in striped muscle has not been ascertained, though they have been found in
tendons and in the sheaths of the muscles.
Ossification of muscular tissue as a result of repeated strain or injury is not infrequent. It
is oftenest found about the tendon of the Adductor longus and Vastus medialis in horsemen,
or in the Pectoralis major and Deltoideus of soldiers. It may take the form of exostoses firmlj'
fixed to the bone — e. g., "rider's bone" on the femur — or of layers or spicules of bone lying in
the muscles or their fasciae and tendons. Busse states that these bony deposits are preceded
by a hemorrhagic myositis due to injury, the effused blood organizing and being finally converted
into bone. In the rarer disease, progressive myositis ossificans, there is an unexplained tendency
for practically any of the voluntary muscles to become converted into soUd and brittle bony
masses which are completely rigid.
TENDONS, APONEUROSES, AND FASCLS.
Tendons are white, glistening, fibrous cords, varying in length and thickness,
sometimes round, sometimes flattened, and devoid of elasticity. They consist
almost entirely of white fibrous tissue, the fibrils of which have an undulating
course parallel with each other and are firmly united together. ^Yhen boiled in
water tendon is almost completely converted into gelatin, the white fibers being
composed of the albuminoid collagen, which is often regarded as the anhydride of
gelatin. They are very sparingly supplied with blood\essels, the smaller tendons
presenting in their interior no trace of them. Nerves supplying tendons have special
modifications of their terminal fibers, named organs of Golgi.
Aponeuroses are flattened or ribbon-shaped tendons, of a pearly white color,
iridescent, glistening, and similar in structure to the tendons. They are only
sparingly supplied with bloodvessels.
The tendons and aponeuroses are connected, on the one hand, with the muscles,
and, on the other hand, with the movable structures, as the bones, cartilages liga-
ments, and fibrous membranes (for instance, the sclera). ^Yhere the muscular fibers
are in a direct line with those of the tendon or aponeurosis, the two are directly
continuous. But where the muscular fibers join the tendon or aponeurosis at an
oblique angle, they end, according to Kolliker, in rounded extremities which are
received into corresponding depressions on the surface of the latter, the connective
tissue between the muscular fibers being continuous with that of the tendon. The
latter mode of attachment occurs in all the penniform and bipenniform muscles,
and in those muscles the tendons of which commence in a membranous form,
as the Gastrocnemius and Soleus.
The fasciae are fibroareolar or aponeurotic laminae, of variable thickness and
strength, found in all regions of the body, investing the softer and more delicate
organs. During the process of development many of the cells of the mesoderm
are differentiated into bones, muscles, vessels, etc.; the cells of the mesoderm which
are not so utilized form an investment for these structures and are differentiated
into the true skin and the fasciae of the body. They have been subdivided, from
the situations in which they occur, into superficial and deep.
TENDONS, APONEUROSES, AND FASCIJE
377
The superficial fascia is found immediately beneath the integument over almost the
entire surface of the body. It connects the skin with the deep fascia, and consists
of fibroareolar tissue, containing in its meshes pellicles of fat in varying quantity.
Fibro-areolar tissue is composed of white fibers and yellow elastic fibers intercrossing
in all directions, and united together by a homogeneous cement or ground substance,
the matrix.
The cells of areolar tissue are of four principal kinds: (1) Flattened lamellar
cells, which may be either branched or un branched. The branched lamellar cells
are composed of clear cytoplasm, and contain oval nuclei; the processes of these
cells may unite so as to form an open network, as in the cornea. The unbranched
cells are joined edge to edge like the cells of an epithelium ; the " tendon cells," pres-
ently to be described, are examples of this variety. (2) Clasmatocytes, large irregular
cells characterized by the presence of granules or vacuoles in their protoplasm.
White
'fibres
_ Elastic
fibres
Fibrillated
cell
Fig. 377.
Lamellar cell
-Subcutaneous tissue from a young rabbit.
Highly magnified. (Schafer.)
and containing oval nuclei. (3) Granule cells (Mastzellen), which are ovoid or
spheroidal in shape. They are formed of a soft protoplasm, containing granules
which are basophil in character. (4) Plasma cells of Waldeyer, usually spheroidal
and distinguished by containing a vacuolated protoplasm. The vacuoles are filled
with fluid, and the protoplasm between the spaces is clear, with occasionally a few
scattered basophil granules.
In addition to these four typical forms of connective-tissue corpuscles, areolar
tissue may be seen to possess wandering cells, i. e., leucocytes which have emigrated
from the neighboring vessels; in some instances, as in the choroid coat of the eye
cells filled with granules of pigment (pigment cells) are found.
The cells lie in spaces in the ground substance between the bundles of fibers,
and these spaces may be brought into view by treating the tissue with nitrate of
silver and exposing it to the light. This will color the ground substance and leave
the cell-spaces unstained.
378 MYOLOGY
Fat is entirely absent in the subcutaneous tissue of the eyelids, of the penis
and scrotum, and of the labia minora. It varies in thickness in different parts of
the body; in the groin it is so thick that it may be subdivided into several laminae.
Beneath the fatty layer there is generally another layer of superficial fascia, com-
paratively devoid of adipose tissue, in which the trunks of the subcutaneous vessels
and nerves are found, as the superficial epigastric vessels in the abdominal region,
the superficial veins in the forearm, the saphenous veins in the leg and thigh, and the
superficial lymph glands. Certain cutaneous muscles also are situated in the super-
ficial fascia, as the Platysma in the neck, and the Orbicularis oculi around the eyelids.
This fascia is most distinct at the lower part of the abdomen, perineum, and extremi-
ties; it is very thin in those regions where muscular fibers are inserted into the
integument, as on the side of the neck, the face, and around the margin of the anus.
It is very dense in the scalp, in the palms of the hands, and soles of the feet, forming a
fibro-fatty layer, which binds the integument firmly to the underlying structures.
The superficial fascia connects the skin to the subjacent parts, facilitates the
movement of the skin, serves as a soft nidus for the passage of vessels and nerves
to the integument, and retains the warmth of the body, since the fat contained in
its areolae is a bad conductor of heat.
The deep fascia is a dense, inelastic, fibrous membrane, forming sheaths for the
muscles, and in some cases affording them broad surfaces for attachment. It
consists of shining tendinous fibers, placed parallel with one another, and connected
together by other fibers disposed in a rectilinear manner. It forms a strong invest-
ment which not only binds down collectively the muscles in each region, but gives a
separate sheath to each, as well as to the vessels and nerves. The fasciae are thick
in unprotected situations, as on the lateral side of a limb, and thinner on the medial
side. The deep fascite assist the muscles in their actions, by the degree of tension
and pressure they make upon their surfaces; the degree of tension and pressure
is regulated by the associated muscles, as, for instance, by the Tensor fasciae latae
and Gluta^us maximus in the thigh, by the Biceps in the upper and lower extremi-
ties, and Palmaris longus in the hand. In the limbs, the fasciae not only invest
the entire limb, but give off septa which separate the various muscles, and are
attached to the periosteum: these prolongations of fasciae are usually spoken of as
intermuscular septa.
The Fasciae and Muscles may be arranged, according to the general division
of the body, into those of the head and neck ; of the trunk ; of the upper extremity ;
and of the lower extremity.
THE FASCLffi AND MUSCLES OF THE HEAD.
I. THE MUSCLE OF THE SCALP.
Epicranius.
The Skin of the Scalp. — This is thicker than in any other part of the body. It is intimately
adherent to the superficial fascia, which attaches it firmly to the underlying aponeurosis and
muscle. Movements of the muscle move the skin. The hair follicles are very closely set together,
and extend throughout the whole thickness of the skin. It also contains a number of sebaceous
glands.
The superficial fascia in the cranial region is a firmi, dense, fibro-fatty layer,
intimately adherent to the integument, and to the Epicranius and its tendinous
aponeurosis; it is continuous, behind, with the superficial fascia at the back of the
neck; and, laterally, is continued over the temporal fascia. It contains between
its layers the superficial vessels and nerves and much granular fat.
The Epicranius (Occipitofrontalis) (Fig. 378) is a broad, musculofibrous layer.
THE MUSCLE OF THE SCALP
379
which covers the whole of one side of the vertex of the skull, from the occipital
bone to the eyebrow. It consists of two parts, the Occipitalis and the Frontalis,
connected by an intervening tendinous aponeurosis, the galea aponeurotica.
The Occipitalis, thin and quadrilateral in form, arises by tendinous fibers from
the lateral two-thirds of the superior nuchal line of the occipital bone, and from
the mastoid part of the temporal. It ends in the galea aponeurotica.
Corrugator
Dilatator nans ant.
Dilatator 7iaris post
Xasaliti '■
Depressor septi
Fig. 378. — Muscles of the head, face, and neck.
The Frontalis is thin, of a quadrilateral form, and intimately adherent to the
superficial fascia. It is broader than the Occipitalis and its fibers are longer and
paler in color. It has no bony attachments. Its medial fibers are continuous with
those of the Procerus; its immediate fibers blend with the Corrugator and Orbicu-
laris oculi; and its lateral fibers are also blended with the latter muscle over
the zygomatic process of the frontal bone. From these attachments the fibers
are directed upward, and join the galea aponeurotica below the coronal suture.
380 MYOLOGY
The medial margins of the Frontales are joined together for some distance above
the root of the nose; but between the Occipitales there is a considerable, though
variable, interval, occupied by the galea aponeurotica.
The galea aponeurotica (epicranial aponeurosis) covers the upper part of the
cranium; behind, it is attached, in the interval between its union with the Occipi-
tales, to the external occipital protuberance and highest nuchal lines of the occipital
bone; in front, it forms a short and narrow prolongation between its union with
the Frontales. On either side it gives origin to the Auriculares anterior and supe-
rior; in this situation it loses its aponeurotic character, and is continued over the
temporal fascia to the zygomatic arch as a layer of laminated areolar tissue. It
is closely connected to the integument by the firm, dense, fibro-fatty layer which
forms the superficial fascia of the scalp : it is attached to the pericranium by loose
cellular tissue, which allows the aponeurosis, carrying with it the integument to
move through a considerable distance.
Variations. — Both Frontalis and Occipitalis vary considerably in size and in extent of attach-
ment; either may be absent; fusion of Frontalis to skin has been noted.
Nerves. — The Frontalis is supplied by the temporal branches of the facial nerve, and the
Occipitalis by the posterior auricular branch of the same nerve.
Actions. — The Frontales raise the eyebrows and the skin over the root of the nose, and at the
same time draw the scalp forward, throwing the integument of the forehead into transverse
wrinkles. The Occipitales draw the scalp backward. By bringing alternately into action the
Frontales and Occipitales the entire scalp may be moved forward and backward. In the ordinary
action of the muscles, the eyebrows are elevated, and at the same time the aponeurosis is fixed
by the Occipitales, thus giving to the face the expression of surprise; if the action be exaggerated,
the eyebrows are still further raised, and the skin of the forehead thrown into transverse wrinkles,
as in the expression of fright or horror.
A thin muscular slip, the Transversus nuchae, is present in a considerable pro-
portion (25 per cent.) of cases; it arises from the external occipital protuberance
or from the superior nuchal line, either superficial or deep to the Trapezius; it
is frequently inserted with the Auricularis posterior, but may join the posterior
edge of the Sternocleidomastoideus.
II. THE MUSCLES OF THE EYELIDS.
The muscles of the eyelids are:
Levator palpebrse superioris. Orbicularis oculi. Corrugator.
The Levator palpebral superioris is described with the Anatomy of the Eye.
The Orbicularis oculi {Orbicularis palpebrarum) (Fig. 379) arises from the nasal
part of the frontal bone, from the frontal process of the maxilla in front of the
lacrimal groove, and from the anterior surface and borders of a short fibrous band,
the medial palpebral ligament. From this origin, the fibers are directed lateral-
ward, forming a broad and thin layer, which occupies the eyelids or palpebrte,
surrounds the circumference of the orbit, and spreads over the temple, and down-
ward on the cheek. The palpebral portion of the muscle is thin and pale; it arises
from the bifurcation of the medial palpebral ligament, forms a series of concentric
curves, and is inserted into the lateral palpebral raphe. The orbital portion is thicker
and of a reddish color; its fibers form a complete ellipse without interruption at
the lateral palpebral commissure; the upper fibers of this portion blend with the
Frontalis and Corrugator. The lacrimal part ( Tensor tarsi) is a small, thin muscle,
about 6 mm. in breadth and 12 mm. in length, situated behind the medial palpebral
ligament and lacrimal sac (Fig. 379) . It arises from the posterior crest and adjacent
part of the orbital surface of the lacrimal bone, and passing behind the lacrimal
sac, divides into two slips, upper and lower, which are inserted into the superior
aiid inferior tarsi medial to the puncta lacrimalia; occasionally it is very indistinct.
THE MUSCLES OF THE EYELIDS
381
The medial palpebral ligament (tendo oculi), about 4 mm. in length and 2 mm.
in breadth, is attached to the frontal process of the maxilla in front of the lacrimal
groove. Crossing the lacrimal sac, it divides into two parts, upper and lower,
each attached to the medial end of the corresponding tarsus. As the ligament
crosses the lacrimal sac, a strong aponeurotic lamina is given off from its posterior
surface; this expands over the sac, and is attached to the posterior lacrimal crest.
The lateral palpebral raphe is a much weaker structure than the medial palpebral
ligament. It is attached to the margin of the frontosphenoidal process of the
zygomatic bone,^ and passes medialward to the lateral commissure of the eyelids,
where it divides into two slips, which are attached to the margins of the respective
tarsi.
Probe in frontal sinus
I
Probe in ant. eth-
moidal cells
Crista iia'.li
— • Lacrimal part of
Orbicularis oculi
Probe in lacrimal sac
( Probes from frontal
\si}ius and ant. eth-
moidal cells
Middle meatus
Septum of nose
Probe in nasolacrimal
duct
Infraorbital nerve and artery
Fig. 379. — Left orbicularis oculi, seen from behind.
The Comigator^ (Corrugator suyercilii) is a small, narrow, pyramidal muscle,
placed at the medial end of the eyebrow, beneath the PVontalis and Orbicularis
oculi. It arises from the medial end of the superciliary arch; and its fibers pass
upward and lateralward, between the palpebral and orbital portions of the Orbicu-
laris oculi, and are inserted into the deep surface of the skin, above the middle of
the orbital arch.
Nerves. — The Orbicularis oculi and Corrugator are supplied by the facial nerve.
Actions. — The Orbicularis ocuU is the sphincter muscle of the eyehds. The palpebral portion
acts involuntarily, closing the lids gently, as in sleep or in blinking; the orbital portion is subject
to the will. When the entire muscle is brought into action, the skin of the forehead, temple,
and cheek is drawn toward the medial angle of the orbit, and the eyelids are firmly closed, as in
photophobia. The skin thus drawn upon is throwTi into folds, especially radiating from the
lateral angle of the eyelids; these folds become permanent in old age, and form the so-called
"crows' feet." The Levator palpebra; superioris is the direct antagonist of this muscle; it raises
the upper eyelid and exposes the front of the bulb of the eye. Each time the eyehds are closed
through the action of the Orbicularis, the medial palpebral ligament is tightened, the wall of
the lacrimal sac is thus drawn lateralward and forward, so that a vacuum is made in it and the
* The corrugator is not recognized as a separate muscle in the Basle Nomenclature.
382 MYOLOGY
tears are sucked along the lacrimal canals into it. The lacrimal part of the Orbicularis oculi
draws the eyelids and the ends of the lacrimal canals medialward and compresses them against
the surface of the globe of the eye, thus placing them in the most favorable situation for receiving
the tears; it also compresses the lacrimal sac. The Corrugator draws the eyebrow downward
and medialward, producing the vertical wrinkles of the forehead. It is the "frowning" muscle,
and may be regarded as the principal muscle in the expression of suffering.
m. THE MUSCLES OF THE NOSE (Fig. 378).
The muscles of the nose comprise:
Procerus. Depressor septi.
Nasahs. Dilatator naris posterior.
Dilatator naris anterior.
The Procerus (Pyramidalis nasi) is a small pyramidal slip arising by tendinous
fibers from the fascia covering the lower part of the nasal bone and upper part
of the lateral nasal cartilage; it is inserted into the skin over the lower part of
the forehead between the two eyebrows, its fibers decussating with those of the
Frontalis.
The NasaUs (Compressor naris) consists of two parts, transverse and alar. The
transverse part arises from the maxilla, above and lateral to the incisive fossa;
its fibers proceed upward and medialward, expanding into a thin aponeurosis
which is continuous on the bridge of the nose with that of the muscle of the oppo-
site side, and with the aponeurosis of the Procerus. The alar part is attached by
one end to the greater alar cartilage, and by the other to the integument at the
point of the nose.
The Depressor septi {Depressor ala^ nasi) arises from the incisive fossa of the
maxilla; its fibers ascend to be inserted into the septum and back part of the ala
of the nose. It lies between the mucous membrane and muscular structure of
the lip.
The Dilatator naris posterior is placed partly beneath the Quadratus labii
superioris. It arises from the margin of the nasal notch of the maxilla, and from
the lesser alar cartilages, and is inserted into the skin near the margin of the
nostril.
The Dilatator naris anterior is a delicate fasciculus, passing from the greater
alar cartilage to the integument near the margin of the nostril; it is situated in
front of the preceding.
Variations. — These muscles vary in size and strength or may be absent.
Nerves. — All the muscles of this group are supplied bj- the facial nerve.
Actions. — The Procerus draws do\\Ti the medial angle of the eyebrows and produces transverse
wrinkles over the bridge of the nose. The two Dilatatores enlarge the aperture of the nares.
Their action in ordinary breathing is to resist the tendency of the nostrils to close from atmos-
pheric pressure, but in difficult breathing, as well as in some emotions, such as anger, they con-
tract strongly. The Depressor septi is a direct antagonist of the other muscles of the nose, drawing
the ala of the nose downward, and thereby constricting the aperture of the nares. The Nasalis
depresses the cartilaginous part of the nose and draws the ala toward the septum.
IV. THE MUSCLES OF THE MOUTH.
The muscles of the mouth are :
Quadratus labii superioris. Quadratus labii inferioris.
Caninus. Triangularis.
Zygomaticus. Buccinator.
Mentalis. Orbicularis oris.
Risorius.
THE MUSCLES OF THE MOUTH 383
The Quadratus labii superioris is a broad sheet, the origin of which extends
from the side of the nose to the zygomatic bone. Its medial fibers form the angular
head, which arises l\\- a pointed extremity from the upper part of the frontal process
of the maxilla and passing obliquely downward and lateralward divides into two
slips. One of these is inserted into the greater alar cartilage and skin of the nose;
the other is prolonged into the lateral part of the upper lip, blending with the
infraorbital head and with the Orbicularis oris. The intermediate portion or
infraorbital head arises from the lower margin of the orbit immediately above the
infraorbital foramen, some of its fibers being attached to the maxilla, others to the
zygomatic bone. Its fibers converge, to be inserted into the muscular substance
of the upper lip between the angular head and the Caninus. The lateral fibers,
forming the zygomatic head, arise from the malar surface of the zygomatic bone
immediately behind the zygomaticomaxillary suture and pass downward and
medialward to the upper lip.
The Caninus (Levator angidi oris) arises from the canine fossa, immediately
below the infraorbital foramen ; its fibers are inserted into the angle of the mouth,
intermingling with those of the Zygomaticus, Triangularis, and Orbicularis oris.
The Zygomaticus {Zygomaticus major) arises from the zygomatic bone, in front
of the zygomaticotemporal suture, and descending obliquely with a medial inclina-
tion, is imerted into the angle of the mouth, where it blends with the fibers of the
Caninus, Orbicularis oris, and Triangularis.
Nerves. — This group of muscles is supplied by the facial nerve.
Actions. — The Quadratus labii superioris is the proper elevator of the upper lip, carrying it
at the same time a little forward. Its angular head acts as a dilator of the naris; the infraorbital
and zygomatic heads assist in forming the nasolabial furrow, which passes from the side of the
nose to the upper lip and gives to the face an expression of sadness. When the whole muscle
is in action it gives to the countenance an expression of contempt and disdain. The Quad-
ratus labii superioris raises the angle of the mouth and assists the Caninus in producing the
nasolabial furrow. The Zygomaticus draws the angle of the mouth backward and upward, as
in laughing.
The Mentalis {Levator menti) is a small conical fasciculus, situated at the side
of the frenulum of the lower lip. It arises from the incisive fossa of the mandible,
and descends to be inserted into the integument of the chin.
The Quadratus labii inferioris {Depressor labii inferioris; Quadratus menti) is
a small quadrilateral muscle. It arises from the oblique line of the mandible,
between the symphysis and the mental foramen, and passes upward and medial-
ward, to be inserted into the integument of the lower lip, its fibers blending with
the Orbicularis oris, and with those of its fellow of the opposite side. At its origin
it is continuous with the fibers of the Platysma. Much yellow fat is intermingled
with the fibers of this muscle.
The Triangularis {Depressor angidi oris) arises from the oblique line of the
mandible, whence its fibers converge, to be inserted, by a narrow fasciculus, into
the angle of the mouth. At its origin it is continuous with the Platysma, and at
its insertion with the Orbicularis oris and Risorius; some of its fibers are directly
continuous with those of the Caninus, and others are occasionally found crossing
from the muscle of one side to that of the other; these latter fibers constitute
the Transversus menti.
Nerves. — This group of muscles is supplied by the facial nerve.
Actions.— The Mentahs raises and protrudes the lower Hp, and at the same time wrinkles the
skin of the chin, expressing doubt or disdain. The Quadratus labii inferioris draws the lower
lip directly downward and a little lateralward, as in the expression of irony. The Triangularis
depresses lihe angle of the mouth, being the antagonist of the Caninus and Zygomaticus; acting
with the Caninus, it will draw the angle of the mouth medialward. The Platysma which retracts
and depresses the angle of the mouth belongs with this group.
384
^MYOLOGY
The Buccinator (Fig. 380) is a thin quadrilateral muscle, occupying the interval
between the maxilla and the mandible at the side of the face. It arises from the
outer surfaces of the alveolar processes of the maxilla and mandible, corresponding
to the three molar teeth; and behind, from
the anterior border of the pterygomandib-
ular raphe which separates it from the
Constrictor pharyngis superior. The fibers
converge toward the angle of the mouth,
where the central fibers intersect each
other, those from below being continuous
with the upper segment of the Orbicu-
laris oris, and those from above with the
lower segment ; the upper and lower fibers
are continued forward into the corre-
sponding lip without decussation.
CANINU9
'BUCCINATOR
Fig. 380. — Muscles of the pharynx and cheek.
TRIANGULARJS
Fig. 3S1. — Scheme showing arrangement of fibers of
Orbicularis oris.
Relations. — The Buccinator is covered by the buccopharj-ngeal fascia, and is in relation by
its superficial surface, behind, with a large mass of fat, which separates it from the ramus of the
mandible, the IVIasseter, and a small portion of the Temporalis; this fat has been named the
suctorial pad, because it is supposed to assist in the act of sucking. The parotid duct pierces the
Buccinator opposite the second molar tooth of the maxiUa. The deep surface is in relation with
the buccal glands and mucous membrane of the mouth.
The pterygomandibular raphe {pterygomandibular ligament) is a tendinous band
of the buccopharyngeal fascia, attached by one extremity to the hamulus of the
medial pterygoid plate, and by the other to the posterior end of the mylohyoid
line of the mandible. Its medial surface is covered by the mucous membrane of
the mouth. Its lateral surface is separated from the ramus of the mandible by a
quantity of adipose tissue. Its posterior border gives attachment to the Constrictor
pharyngis superior; its anterior border, to part of the Buccinator (Fig. 3S0).
The Orbicularis oris (Fig. 381) is not a simple sphincter muscle like the Orbic-
ularis oculi; it consists of numerous strata of muscular fibers surrounding the
orifice of the mouth but having difterent direction. It consists partly of fibers
derived from the other facial muscles which are inserted into the lips, and partly
of fibers proper to the lips. Of the former, a considerable number are derived from
the Buccinator and form the deeper stratum of the Orbicularis. Some of the
Buccinator fibers — namely, those near the middle of the muscle — decussate at
the angle of the mouth, those arising from the maxilla passing to the lower lip,
and those from the mandible to the upper lip. The uppermost and lowermost
fibers of the Buccinator pass across the lips from side to side without decussation.
Superficial to this stratum is a second, formed on either side by the Caninus and
THE MUSCLES OF MASTICATION 385
Triangularis, which cross each other at the angle of the mouth; those from the
Caninus passing to the lower lip, and those from the Triangularis to the upper lip,
along which they run, to be inserted into the skin near the median line. In addi-
tion to these there are fibers from the Quadratus labii superioris, the Zygomaticus,
and the Quadratus labii inferioris; these intermingle with the transverse fibers
above described, and have principally an oblique direction. The proper fibers
of the lips are oblique, and pass from the under surface of the skin to the mucous
membrane, through the thickness of the lip. Finally there are fibers by which the
muscle is connected wath the maxillse and the septum of the nose above and with
the mandible below. In the upper lip these consist of two bands, lateral and medial,
on either side of the middle line; the lateral band (m. incisivus labii superioris)
arises from the alveolar border of the maxilla, opposite the lateral incisor tooth,
and arching lateralward is continuous with the other muscles at the angle of the
mouth; the medial band (m. nasolabialis) connects the upper lip to the back of the
septum of the nose. The interval between the two medial bands corresponds
with the depression, called the philtrum, seen on the lip beneath the septum of the
nose. The additional fibers for the lower lip constitute a slip {m. incisivus labii
inferioris) on either side of the middle line; this arises from the mandible, lateral
to the Mentalis, and intermingles with the other muscles at the angle of the
mouth.
The Risorius arises in the fascia over the Masseter and, passing horizontally
forward, superficial to the Platysma, is inserted into the skin at the angle of the
mouth (Fig. 378). It is a narrow bundle of. fibers, broadest at its origin, but varies
much in its size and form.
Variations. — The zygomatic head of the Quadratus labii superioris and Risorius are frequently
absent and more rarely the Zygomaticus. The Zygomaticus and Risorius may be doubled or the
latter greatly enlarged or blended with the Platysma.
Nerves. — The muscles in this group are all suppUed by the facial nerve.
Actions. — The Orbicularis oris in its ordinary action effects the direct closure of the hps; by
its deep fibers, assisted by the oblique ones, it closely applies the lips to the alveolar arch. The
superficial part, consisting principally of the decussating fibers, brings the hps together and also
protrudes them forward. The Buccinators compress the cheeks, so that, during the process of
mastication, the food is kept under the immediate pressure of the teeth. When the cheeks have
been previously distended with air, the Buccinator muscles expel it from between the lips, as in
blowing a trumpet; hence the name {buccina, a trumpet). The Risorius retracts the angle of
the mouth, and produces an unpleasant grinning expression.
For more extensive consideration of the facial muscles, see Charles Darwin,
Expression of the Emotions in Man and Animals.
IV. THE MUSCLES OF MASTICATION.
The chief muscles of mastication are:
Masseter. Pterygoideus externus.
Temporalis. Pterygoideus internus.
Parotideomasseteric Fascia {masseteric fascia) . — Covering the Masseter, and firmly
connected with it, is a strong layer of fascia derived from the deep cervical fascia.
Above, this fascia is attached to the lower border of the zygomatic arch, and behind,
it invests the parotid gland.
The Masseter (Fig. 378) is a thick, somewhat quadrilateral muscle, consisting
of two portions, superficial and deep. The superiacial portion, the larger, arises
by a thick, tendinous aponeurosis from the zygomatic process of the maxilla, and
from the anterior two-thirds of the lower border of the zygomatic arch : its fibers
pass downward and backward, to be inserted into the angle and lower half of the
lateral surface of the ramus of the mandible. The deep portion is much smaller,
25
386
MYOLOGY
and more muscular in texture; it arises from the posterior third of the lower border
and from the whole of the medial surface of the zygomatic arch; its fibers pass
downward and forward, to be inserted into the upper half of the ramus and the
lateral surface of the coronoid process of the mandible. The deep portion of the
muscle is partly concealed, in front, by the superficial portion; behind, it is covered
by the parotid gland. The fibers of the two portions are continuous at their
insertion.
Temporal Fascia. — ^The temporal fascia covers the Temporalis muscle. It is a
strong, fibrous investment, covered, laterally, by the Auricularis anterior and supe-
rior, by the galea aponeurotica, and by part of the Orbicularis oculi. The super-
ficial temporal vessels and the auriculotemporal nerve cross it from below upward.
Above, it is a single layer, attached to the entire extent of the superior temporal
line; but below, where it is fixed to the zygomatic arch, it consists of two layers, one
of which is inserted into the lateral, and the other into the medial border of the
arch. A small quantity of fat, the orbital branch of the superficial temporal artery,
and a filament from the zygomatic branch of the maxillary nerve, are contained
between these two layers. It aft'ords attachment by its deep surface to the super-
ficial fibers of the Temporalis.
Fig. 382. — The Temporalis; the zygomatic arch and Masseter have been removed.'
The Temporalis {Temporal vmscJe) (Fig. 382) is a broad, radiating muscle,
situated at the side of the head. It arises from the whole of the temporal fossa
(except that portion of it which is formed by the zygomatic bone) and from the
deep surface of the temporal fascia. Its fibers converge as they descend, and end
in a tendon, which passes deep to the zygomatic arch and is inserted into the medial
surface, apex, and anterior border of the coronoid process, and the anterior border
of the ramus of the mandible nearly as far forward as the last molar tooth.
The Pterygoideus extemus (External pterygoid muscle) (Fig. 383) is a short, thick
muscle, somewhat conical in form, which extends almost horizontally between the
infratemporal fossa and the condyle of the mandible. It arises by two heads;
an upper from the lower part of the lateral surface of the great wing of the sphenoid
and from the infratemporal crest; a lower from the lateral surface of the lateral
pterygoid plate. Its fibers pass horizontally backward and lateralward, to be
THE SUPERFICIAL CERVICAL MUSCLE
387
imerted into a depression in front of the neck of the condyle of the mandible, and
into the front margin of the articular disk of the temporomandibular articulation.
The Pterygoideus internus {Internal pterygoid muscle) (Fig. 3S3) is a thick, quad-
rilateral muscle. It arises from the medial surface of the lateral pterygoid plate
and the grooved surface of the pyramidal process of the palatine bone; it has a
second slip of origin from the lateral surfaces of the pyramidal process of the pala-
tine and tuberosity of the maxilla. Its fibers pass downward, lateralward, and
backward, and are inserted, by a strong tendinous lamina, into the lower and back
part of the medial surface of the ramus and angle of the mandible, as high as the
mandibular foramen.
Fig. 383. — The Pterygoidei ; the zygomatic arch and a portion of the ramus of the mandible have been removed.
Nerves. — The muscles of mastication are supplied by the mandibular nerve.
Actions. — The Temporalis, Masseter, and Pterygoideus internus raise the mandible against
the maxillae with great force. The Pterygoideus externus assists in opening the mouth, but its
main action is to draw forward the condyle and articular disk so that the mandible is protruded
and the inferior incisors projected in front of the upper; in this action it is assisted by the Ptery-
goideus internus. The mandible is retracted by the posterior fibers of the Temporalis. If the
Pterygoidei internus and externus of one side act, the corresponding side of the mandible is
drawn forward while the opposite condyle remains comparatively fixed, and side-to-side move-
ments, such as occur during the trituration of food, take place.
THE FASCI-ffi AND MUSCLES OF THE ANTERO-LATERAL REGION
OF THE NECK.
The antero-lateral muscles of the neck may be arranged into the following
groups :
I. Superficial Cervical. III. Supra- and Infrahyoid.
II. Lateral Cervical. IV. Anterior Vertebral,
V. Lateral Vertebral.
I. THE SUPERFICIAL CERVICAL MUSCLE.
Platysma.
The Superficial Fascia of tlte neck is a thin lamina investing the Platysma,
and is hardly demonstrable as a separate membrane.
388 MYOLOGY
The Platysma (Fig. 378) is a broad sheet arising from the fascia covering the
upper parts of the Pectoralis major and Deltoideus; its fibers cross the clavicle,
and proceed obliquely upward and medialward along the side of the neck. The
anterior fibers interlace, below and behind the symphysis menti, with the fibers
of the muscle of the opposite side; the posterior fibers cross the mandible, some
being inserted into the bone below the oblique line, others into the skin and sub-
cutaneous tissue of the lower part of the face, many of these fibers blending with
the muscles about the angle and lower part of the mouth. Sometimes fibers can
be traced to the Zygomaticus, or to the margin of the Orbicularis oculi. Beneath
the Platysma, the external jugular vein descends from the angle of the mandible
to the clavicle.
Variations occur in the extension over the face and over the clavicle and shoulder; it may
be absent or interdigitate with the muscle of the opposite side in front of the neck; attachment
to clavicle, mastoid process or occipital bone occurs. A more or less independent fasciculus, the
Occipitalis minor, may extend from the fascia over the Trapezius to fascia over the insertion of
the Sternocleidomastoideus.
Nerve. — The Platysma is supplied by the cervical branch of the facial nerve.
Actions. — When the entire Platysma is in action it produces a slight wrinkling of the surface
of the skin of the neck in an oblique direction. Its anterior portion, the thickest part of the
muscle, depresses the lower jaw; it also serves to draw down the lower lip and angle of the mouth
in the expression of melancholy.
II. THE LATERAL CERVICAL MUSCLES.
The lateral muscles are :
Trapezius and Sternocleidomastoideus.
The Trapezius is described on page 432.
The Fascia Colli {deep cervical fascia) (Fig. 384). — The fascia colli lies under cover
of the Platysma, and invests the neck; it also forms sheaths for the carotid vessels,
and for the structures situated in front of the vertebral column.
The investing portion of the fascia is attached behind to the ligamentum nuchse
and to the spinous process of the seventh cervical vertebra. It forms a thin in-
vestment to the Trapezius, and at the anterior border of this muscle is continued
forward as a rather loose areolar layer, covering the posterior triangle of the neck,
to the posterior border of the Sternocleidomastoideus, where it begins to assume
the appearance of a fascial membrane. Along the hinder edge of the Sterno-
cleidomastoideus it divides to enclose the muscle, and at the anterior margin again
forms a single lamella, which covers the anterior triangle of the neck, and reaches
forward to the middle line, where it is continuous with the corresponding part from
the opposite side of the neck. In the middle line of the neck it is attached to the
symphysis menti and the body of the hyoid bone.
Above, the fascia is attached to the superior nuchal line of the occipital, to the
mastoid process of the temporal, and to the whole length of the inferior border
of the body of the mandible. Opposite the angle of the mandible the fascia is very
strong, and binds the anterior edge of the Sternocleidomastoideus firmly to that
bone. Between the mandible and the mastoid process it ensheathes the parotid
gland — the layer which covers the gland extends upward under the name of the
parotideomasseteric fascia and is fixed to the zygomatic arch. From the part which
passes under the parotid gland a strong band extends upward to the styloid process,
forming the stylomandibular ligament. Two other bands may be defined: the
sphenomandibular (page 297) and the pterygospinous ligaments. The pterygospinous
ligament stretches from the upper part of the posterior border of the lateral ptery-
goid plate to the spinous process of the sphenoid. It occasionally ossifies, and in
such cases, between its upper border and the base of the skull, a foramen is formed
which transmits the branches of the mandibular nerve to the muscles of mastication.
THE LATERAL CERVICAL MUSCLES
389
Below, the fascia is attached to the acromion, the clavicle, and the manubrium
sterni. Some little distance above the last it splits into two layers, superficial
and deep. The former is attached to the anterior })()rder of the manubrium, the
latter to its posterior border and to the interclavicular ligament. Between these
two layers-is a slit-like interval, the suprasternal space (space of Burns) ; it contains
a small quantity of areolar tissue; the lower portions of the anterior jugular veins
and their transverse connecting branch, the sternal heads of the Sternocleido-
mastoidei, and sometimes a lymph gland.
Omohyoideus
Thyroid gland
\
\
N
Common carotid ariery
Int. jugular vein
Stemocleidoma sto ideus
^~-J/.
Vagus nerve
Ext. jugular vein-
Scalenus anterioi'-iu
Scalenus medius-
Sphnius colli'
Levator scapidcs'
Trapezius'
" Ant. jugular vein
Sternohyoidev^
Sternothyreoideus
Trachea
■■ -Esopha.gus
- 6th cervical vertebra
■ Vertebral vessels
— • Semispinalis colli
Semispinalis capitis
- - Splenius capitis
Fig. 384. — Section of the neck at about the level of the sixth cervical vertebra. Showing the arrangement of the
fascia coll.
The fascia which lines the deep surface of the Sternocleidomastoideus gives off
the following processes: (1) A process envelops the tendon at the Omohyoideus,
and binds it down to the sternum and first costal cartilage. (2) A strong sheath,
the carotid sheath, encloses the carotid artery, internal jugular vein, and vagus
nerve. (3) The prevertebral fascia extends medialward behind the carotid vessels,
where it assists in forming their sheath, and passes in front of the prevertebral
muscles. It forms the posterior limit of a fibrous compartment, which contains
the larynx and trachea, the thyroid gland, and the pharynx and esophagus. The
390 MYOLOGY
prevertebral fascia is fixed above to the base of the skull, and below is continued
into the thorax in front of the Longus colli muscles. Parallel to the carotid sheath
and along its medial aspect the prevertebral fascia gives off a thin lamina, the
buccopharyngeal fascia, which closely invests the Constrictor muscles of the pharynx,
and is continued forward from the Constrictor pharyngis superior on to the Buc-
cinator. It is attached to the prevertebral layer by loose connecti^'e tissue only,
and thus an easily distended space, the retropharsmgeal space, is found between
them. This space is limited above by the base of the skull, while below it extends
behind the esophagus into the posterior mediastinal cavity of the thorax. The pre-
vertebral fascia is prolonged downward and lateralward behind the carotid vessels
and in front of the Scaleni, and forms a sheath for the brachial nerves and sub-
clavian vessels in the posterior triangle of the neck; it is continued under the clavicle
as the axillary sheath and is attached to the deep surface of the coracoclavicular
fascia. Immediately above and behind the clavicle an areolar space exists between
the investing layer and the sheath of the subclavian vessels, and in this space are
found the lower part of the external jugular vein, the descending clavicular nerves,
the transverse scapular and transverse cervical vessels, and the inferior belly of the
Omohyoideus muscle. This space is limited below by the fusion of the coraco-
clavicular fascia with the anterior wall of the axillary sheath. (4) The pretrachial
fascia extends medially in front of the carotid vessels, and assists in forming the
carotid sheath. It is continued behind the depressor muscles of the hyoid bone,
and, after enveloping the thyroid gland, is prolonged in front of the trachea to
meet the corresponding layer of the opposite side. Above, it is fixed to the hyoid
bone, while below it is carried downward in front of the trachea and large vessels
at the root of the neck, and ultimately blends with the fibrous pericardium. This
layer is fused on either side with the prevertebral fascia, and Avith it completes the
compartment containing the larynx and trachea, the thyroid gland, and the pharynx
and esophagus.^
The Sternocleidomastoideus {Sternomastoid muscle) (Fig. 385) passes obliquely
across the side of the neck. It is thick and narrow at its central part, but broader
and thinner at either end. It arises from the sternum and clavicle by two heads.
The jnedial or sternal head is a rounded fasciculus, tendinous in front, fleshy behind,
which arises from the upper part of the anterior surface of the manubrium sterni,
and is directed upward, lateralward, and backward. The lateral or clavicular head,
composed of fleshy and aponeurotic fibers, arises from the superior border and
anterior surface of the medial third of the clavicle; it is directed almost vertically
upward. The two heads are separated from one another at their origins by a
triangular interval, but gradually blend, below the middle of the neck, into a thick,
rounded muscle which is inserted, by a strong tendon, into the lateral surface of
the mastoid process, from its apex to its superior border, and by a thin aponeurosis
into the lateral half of the superior nuchal line of the occipital bone.
Variations. — The Sternocleidomastoideus varies much in the extent of its origin from the clavicle:
in some cases the clavicular head may be as narrow as the sternal; in others it may be as much
as 7.5 cm. in breadth. When the clavicular origin is broad, it is occasionally subdivided into
several slips, separated by narrow intervals. More rarely, the adjoining margins of the Sterno-
cleidomastoideus and Trapezius have been found in contact. The Supraclaincidaris muscle arises
from the manubrium behind the Sternocleidomastoideus and passes behind the Sternocleido-
mastoideus to the ui)per surface of the clavicle.
Triangles of the Neck. — This muscle divides the quadrilateral area of the side of the neck
into two triangles, an anterior and a posterior. The boundaries of the anterior triangle are, in
front, the median line of the neck; above, the lower border of the body of the mandible, and an
imaginary line drawn from the angle of the mandible to the Sternocleidomastoideus; behind,
the anterior border of the Sternocleidomastoideus. The apex of the triangle is at the upper
' F. G. Parsons (Journal of Anatomy and Physiology, vol. xliv) regards the carotid sheath and the fascial planes
in the neck as structures which are artificially produced by dissection.
THE SUPRA- AND INFRAHYOID MUSCLES
391
border of the sternum. The boundaries of the posterior triangle are, in front, the posterior border
of the Sternocleidonriastoideus; below, the middle third of the clavicle; behind, the anterior margin
of the Trapezius. The apex corresponds with the meeting of the Sternocleidomastoideus and
Trapezius on the occipital bone. The anatomy of these triangles will be more fully described
with that of the vessels of the neck (p. 562).
Nerves.— The Sternocleidomastoideus is suppHed by the accessory nerve and branches from
the anterior divisions of the second and third cervical nerves.
Actions.— When only one Sternocleidomastoideus acts, it draws the head toward the shoulder
of the same side, assisted by the Splenius and the Obhquus capitis inferior of the opposite side
At the same time it rotates the head so as to carry the face toward the opposite side. Acting
together from their sternoclavicular attachments the muscles will flex the cervical part of the
vertebral column. If the head be fixed, the two muscles assist in elevating the thorax in forced
inspiration.
Fig. 385. — Muscles of the neck. Lateral view.
m. THE SUPRA- AND INFRAHYOID MUSCLES (Figs. 385, 386).
The suprahyoid muscles are :
Digastricus.
Stylohyoideus.
Mylohyoideus.
Geniohvoideus.
The Digastricus (Digastric muscle) consists of two fleshy belHes united by an
intermediate rounded tendon. It lies below the body of the mandible, and extends,
in a curved form, from the mastoid process to the symphysis menti. The posterior
belly, longer than the anterior, arises from the mastoid notch of the temporal
bone and passes downward and forward. The anterior belly arises from a depression
on the inner side of the lower border of the mandible, close to the symphysis, and
passes downward and backward. The two bellies end in an intermediate tendon
which perforates the Stylohyoideus muscle, and is held in connection with the side
of the body and the greater cornu of the hyoid bone by a fibrous loop, which is
392
MYOLOGY
sometimes lined by a mucous sheath. A broad aponeurotic layer is given off
from the tendon of the Digastricus on either side, to be attached to the body
and greater cornu of the hyoid bone; this is termed the suprahyoid aponeurosis.
Variations are numerous. The posterior belly may arise partly or entirely from the stj'loid
process, or be connected by a slip to the middle or inferior constrictor; the anterior belly may
be double or extra slips from this belh^ may pass to the jaw or Mylohyoideus or decussate with
a similar slip on opposite side; anterior belly may be absent and posterior belly inserted into the
middle of the jaw or hyoid bone. The tendon may pass in front, more rarely behind the Stylo-
hoideus. The Mentohyoideus ituiscle passes from the body of hyoid bone to chin.
The Digastricus divides the anterior triangle of the neck into three smaller triangle (1) the
submaxillary triangle, bounded above by the lower border of the body of the mandible, and
a line drawn from its angle to the Sternocleidomastoideus, below by the posterior belly of the
Digastricus and the Stylohyoideus, in front by the anterior belly of the Digastricus; (2) the
carotid triangle, bounded above by the posterior belly of the Digastricus and Stylohyoideus,
behind by the Sternocleidomastoideus, below by the Omohyoideus; (3) the suprahyoid or sub-
mental triangle, bounded laterally by the anterior belly of the Digastricus, medially by the
middle hne of the neck from the hyoid bone to the symphysis menti, and inferiorly by the body
of the hyoid bone.
Scajmla
Fia. 386. — Muscles of the neck. Anterior view.
The Stylohyoideus (SfyJuhyoid muscle) is a slender muscle, lying in front of, and
above, the posterior belly of the Digastricus. It arises from the back and lateral
surface of the styloid process, near the base; and, passing downward and forward,
is inserted into the body of the hyoid bone, at its junction with the greater cornu,
and just abo^•e the Omohyoideus. It is perforated, near its insertion, by the tendon
of the Digastricus.
Variations. — It may be absent or doubled, lie beneath the carotid artery, or be inserted into
the Omohyoideus, Thyreohyoideus, or Mylohyoideus.
The Stylohyoid Ligament (ligamentum stylohyoideus). — In connection with the
Stylohyoideus muscle a ligamentous band, the stylohyoid ligament, may be
THE SUPRA- AND INFRAHYOID MUSCLES 393
described. It is a fibrous cord, which is attached to the tip of the styloid process
of the temporal and the lesser cornu of the hyoid bone. It frequently contains a
little cartilage in its center, is often partially ossified, and in many animals forms
a distinct bone, the epihyal.
The Mylohyoideus (Mylohyoid muscle), flat and triangular, is situated imme-
diately above the anterior belly of the Digastricus, and forms, with its fellow of the
opposite side, a muscular floor for the cavity of the mouth. It arises from the whole
length of the mylohyoid line of the mandible, extending from the symphysis in
front to the last molar tooth behind. The posterior fibers pass medialward and
slightly downward, to be inserted into the body of the hyoid bone. The middle and
anterior fibers are inserted into a median fibrous raphe extending from the sym-
physis menti to the hyoid bone, where they join at an angle with the fibers of the
opposite muscle. This median raphe is sometimes wanting; the fibers of the two
muscles are then continuous.
Variations. — It may be united to or replaced by the anterior belly of the Digastricus; accessory
slips to other hyoid muscles are frequent.
The Geniohyoideus ( Geniohyoid muscle) is a narrow muscle, situated above the
medial border of the Mylohyoideus. It arises from the. inferior mental spine on
the back of the symphysis menti, and runs backward and slightly downward, to
be inserted into the anterior surface of the body of the hyoid bone; it lies in con-
tact with its fellow of the opposite side.
Variations. — It may be blended with the one on opposite side or double; slips to greater
cornu of hyoid bone nnd Genioglossus occur.
Nerves. — The Mylohyoideus and anterior belly of the Digastricus are supphed by the mjdo-
hyoid branch of the inferior alveolar; the Stylohyoideus and posterior belly of the Digastricus,
by the facial; the Geniohyoideus, by the hj^poglossal.
Actions. — These muscles perform two very important actions. During the act of deglutition
they raise the hyoid bone, and with it the base of the tongue; when the hyoid bone is fixed by its
depressors and those of the larynx, they depress the mandible. During the first act of degluti-
tion, when the mass of food is being driven from the mouth into the pharynx, the hyoid bone
and with it the tongue, is carried upward and forward by the anterior bellies of the Digastrici,
the Mylohyoidei, and Geniohyoidei. In the second act, when the mass is passing through the
pharynx, the direct elevation of the hyoid bone takes place by the combined action of all the
muscles; and after the food has passed, the hyoid bone is carried upward and backward by the
posterior bellies of the Digastrici and the Stylohyoidei, which assist in preventing the return
of the food into the mouth.
The infrahyoid muscles are:
Sternohyoideus. Thyreohyoideus.
Sternothyreoideus. Omohyoideus.
The Sternohyoideus {Sternohyoid muscle) is a thin, narrow muscle, which arises
from the posterior surface of the medial end of the clavicle, the posterior sterno-
clavicular ligament, and the upper and posterior part of the manubrium sterni.
Passing upward and medialward, it is inserted, by short, tendinous fibers, into the
lower border of the body of the hyoid bone. Below, this muscle is separated
from its fellow by a considerable interval; but the two muscles come into contact
with one another in the middle of their course, and from this upward, lie side by
side. It sometimes presents, immediately above its origin, a transverse tendinous
inscription.
Variations. — Doubling; accessory slips (Cleidohyoideus) ; absence.
The Sternothyreoideus {Sternothyroid muscle) is shorter and wider than the
preceding muscle, beneath which it is situated. It arises from the posterior surface
of the manubrium sterni, below the origin of the Sternohyoideus, and from the edge
of the cartilage of the first rib, and sometimes that of the second rib, it is inserted
394 MYOLOGY
into the oblique line on the lamina of the thyroid cartilage. This muscle is in
close contact with its fellow at the lower part of the neck, but diverges somewhat
as it ascends; it is occasionally traversed by a transverse or oblique tendinous
inscription.
Variations. — Doubling; absence; accessory slips to Thyreohyoideus, Inferioi* constrictor, or
carotid sheath.
The Thyreohyoideus {Thyrohyoid muscle) is a small, quadrilateral muscle
appearing like an upward continuation of the Sternothyreoideus. It arises from
the oblique line on the lamina of the thyroid cartilage, and is inserted into the
lower border of the greater cornu of the hyoid bone.
The Omohyoideus (Omohyoid muscle) consists of two fleshy beliies united by
a central tendon. It arises from the upper border of the scapula, and occasionally
from the superior transverse ligament which crosses the scapular notch, its extent
of attachment to the scapula varying from a few millimetres to 2.5 cm. From
this origin, the inferior belly forms a flat, narrow fasciculus, which inclines forward
and slightly upward across the lower part of the neck, being bound down to the
clavicle by a fibrous expansion; it then passes behind the Sternocleidomastoideus,
becomes tendinous and changes its direction, forming an obtuse angle. It ends
in the superior belly, which passes almost vertically upward, close to the lateral
border of the Sternohyoideus, to be inserted into the lower border of the body
of the hyoid bone, lateral to the insertion of the Sternohyoideus. The central
tendon of this muscle varies much in length and form, and is held in position by
a process of the deep cervical fascia, which sheaths it, and is prolonged down to
be attached to the clavicle and first rib ; it is by this means that the angular form
of the muscle is maintained.
Variations. — Doubling; absence; origin from clavicle; absence or doubling of either l)elly.
The inferior belly of the Omohyoideus divides the posterior triangle of the neck into an upper
or occipital triangle and a lower or subclavian triangle, while its superior belly divides the anterior
triangle into an upper or carotid triangle and a lower or muscular triangle.
Nerves. — The Infrahyoid muscles are supplied by branches from the first three cervical nerves.
From the first two nerves the branch joins the hypoglossal trunk, runs with it some distance,
and sends olT a branch to the Thyreohyoideus; it then leaves the hypoglossal to form the descendens
hypoglossi and unites with the communicantes cervicalis from the second and third cervical nerves
to form the ansa hypoglossi from which nerves pass to the other Infrahyoid muscles.
Actions. — These muscles depress the larynx and hyoid bone, after they have been drawn up
with the pharynx in the act of deglutition. The Omohyoidei not only depress the hyoid bone,
but carry it backward and to one or the other side. They are concerned especially in prolonged
inspiratory efforts; for by rendering the lower part of the cervical fascia tense they lessen the
inward suction of the soft parts, which would otherwise compress the great vessels and the
apices of the lungs. The Thyreohyoideus may act as an elevator of the thyroid cartilage, when
the hyoid bone ascends, drawing the thyroid cartilage up behind the hyoid bone. The Sterno-
thyreoideus acts as a depressor of the thyroid cartilage.
IV. THE ANTERIOR VERTEBRAL MUSCLES (Fig. 387).
The anterior vertebral muscles are:
Longus colli. Rectus capitis anterior.
Longus capitis. Rectus capitis lateralis.
The Longus colli is situated on the anterior surface of the vertebral column,
between the atlas and the third thoracic vertebra. It is broad in the middle,
narrow and pointed at either end, and consists of three portions, a superior oblique,
an inferior oblique, and a vertical. The superior oblique portion arises from the
anterior tubercles of the transverse processes of the third, fourth, and fifth cervical
vertebrae; and, ascending obliquely with a medial inclination, is inserted by a narrow
THE ANTERIOR VERTEBRAL MUSCLES
395
tendon into the tubercle on the anterior arch of the atlas. The inferior obUque
portion, the smallest part of the muscle, arises from the front of the bodies of the
first two or three thoracic vertebrae; and, ascending obliquely in a lateral direction,
IS inserted mto the anterior tubercles of the transverse processes of the fifth and
sixth cervical vertebrae. The vertical portion arises, below, from the front of the
bodies of the upper three thoracic and lower three cervical vertebrae, and is in-
serted into the front of the bodies of the second, third, and fourth cervical vertebrae.
The Longus capitis (Redm capitis anticus major), broad and thick abo\-e,
narrow below, arises by four tendinous slips, from the anterior tubercles of the
transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and
ascends, converging toward its fellow of the opposite side, to be inserted into the
inferior surface of the basilar part of the occipital bone.
FiQ. 387. — The anterior vertebral muacles.
The Rectus capitis anterior (Rectus capitis anticus minor) is a short, flat muscle,
situated immediately behind the upper part of the Longus capitis. It arises from
the anterior surface of the lateral mass of the atlas, and from the root of its
transverse process, and passing obliquely upward and medialward, is inserted into
the inferior surface of the basilar part of the occipital bone immediately in front
of the foramen magnum.
The Rectus capitis lateralis, a short, flat muscle, arises from the upper surface
of the transverse process of the atlas, and is inserted into the under surface of the
jugular process of the occipital bone.
Nerves. ^The Rectus capitis anterior and the Rectus capitis lateralis are supplied from the
loop between the first and second cervical nerves; the Longus capitis, by branches from the
396 MYOLOGY
first, second, and third cervical; the Longus colli, by branches from the second to the seventh
cervical nerves.
Actions. — The Longus capitis and Rectus capitis anterior are the direct antagonists of the
muscles at the back of the neck, serving to restore the head to its natural position after it has
been drawn backward. These muscles also flex the head, and from their obUquity, rotate it,
so as to turn the face to one or the other side. The Rectus laterahs, acting on one side, bends
the head laterally. The Longus colli flexes and slightly rotates the cervical portion of the vertebral
column.
THE LATERAL VERTEBRAL MUSCLES (Fig. 38/
The lateral vertebral muscles are :
Scalenus anterior. Scalenus medius.
Scalenus posterior.
The Scalenus anterior {Scalenus anticus) lies deeply at the side of the neck,
behind the Sternocleidomastoideus. It arises from the anterior tubercles of the
transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and
descending, almost vertically, is inserted by a narrow, flat tendon into the scalene
tubercle on the inner border of the first rib, and into the ridge on the upper surface
of the rib in front of the subclavian groove.
The Scalenus medius, the largest and longest of the three Scaleni, arises
from the posterior tubercles of the transverse processes of the lower six cervical
vertebrae, and descending along the side of the vertebral column, is inserted by a
broad attachment into the upper surface of the first rib, between the tubercle
and the subclavian groove.
The Scalenus posterior {Scalenus posticus), the smallest and most deeply seated
of the three Scaleni, arises, by two or three separate tendons, from the posterior
tubercles of the transverse processes of the lower two or three cervical vertebrae,
and is inserted by a thin tendon into the outer surface of the second rib, behind
the attachment of the Serratus anterior. It is occasionally blended with the
Scalenus medius.
Variations. — The Scaleni muscles vary considerably in their attachments and in the arrange-
ment of their fibers. A slip from the Scalenus anticus may pass behind the subclavian artery.
The Scalenus posticus may be absent or extend to the third rib. The Scalenus pleuralis 7nuscle
extends from the transverse process of the seventh cervical vertebra to the fascia supporting the
dome of the pleura and inner border of first rib.
Nerves. — The Scaleni are supplied by branches from the second to the seventh cervical nerves.
Actions. — When the Scaleni act from above, they elevate the first and second ribs, and are,
therefore, inspiratory muscles. Acting from below, they bend the vertebral column to one or
other side; if the muscles of both sides act, the vertebral column is slightly flexed.
THE FASCI-ffi AND MUSCLES OF THE TRUNK.
The muscles of the trunk may be arranged in six groups:
I. Deep jMuscles of the Back. IV. Muscles of the Abdomen. |
II. Suboccipital ^Muscles. V. JMuscles of the Pelvis.
III. INIuscles of the Thorax. VI. Muscles of the Perineum.
I. THE DEEP MUSCLES OF THE BACK (Fig. 388).
The deep or intrinsic muscles of the back consist of a complex group of muscles
extending from the pelvis to the skull. They are:
Splenius capitis. Multifidus.
Splenius cervicis. Rotatores.
Sacrospinalis. Interspinales.
Semispinalis. Intertransversarli.
I
THE DEEP MUSCLES OF THE BACK 397
The Lumbodorsal Fascia (fascia lumbodorsalis; lumbar aponeurosis and vertebral
fascia).— The lumbodorsal fascia is a deep investing membrane which covers the
deep muscles of the back of the trunk. Abow, it passes in front of the Serratus
posterior superior and is continuous with a similar investing layer on the back of
the neck — the nuchal fascia.
In the thoracic region the lumbodorsal fascia is a thin fibrous lamina which
serves to bind down the Extensor muscles of the vertebral column and to separate
them from the muscles connecting the vertebral column to the upper extremity.
It contains both longitudinal and transverse fibers, and is attached, medially, to
the spinous processes of the thoracic vertebrae; laterally to the angles of the ribs.
In the lumbar region the fascia {lumbar aponeurosis) is in two layers, anterior
and posterior (Figs. 388, 409). The posterior layer is attached to the spinous
processes of the lumbar and sacral vertebrae and to the supraspinal ligament; the
anterior layer is attached, medially, to the tips of the transverse processes of the
lumbar vertebrae and to the intertransverse ligaments, below, to the iliolumbar
ligament, and above, to the lumbocostal ligament. The two layers unite at the
lateral margin of the Sacrospinalis, to form the tendon of origin of the Transversus
abdominis. The aponeurosis of origin of the Serratus posterior inferior and the
Latissimus dorsi are intimately blended with the lumbodorsal fascia.
^Obliquus exlernus
Obliquus intemus
Transversus
Fascia on
Quad. Lumb.
Lumbodorsall^'^^^''^'' ^"^^
\ Posterior layer
Fig. 388. — Diagram of a transverse section of the posterior abdominal wall, to show the disposition of the
lumbodorsal fascia.
The Splenius capitis (Fig. 409) arises from the lower half of the ligamentum
nucha?, from the spinous process of the seventh cervical vertebra, and from the
spinous processes of the upper three or four thoracic vertebrae. The fibers of
the muscle are directed upward and lateralward and are inserted, under cover of
the Sternocleidomastoideus, into the mastoid process of the temporal bone, and
into the rough surface on the occipital bone just below the lateral third of the
superior nuchal line.
The Splenius cervicis {Splenius colli) (Fig. 409) arises by a narrow tendinous
band from the spinous processes of the third to the sixth thoracic vertebrae; it is
inserted, by tendinous fasciculi, into the posterior tubercles of the transverse
processes of the upper two or three cervical vertebrae.
Variations. — The origin is frequently moved up or down one or two vertebrse. Accessory slips
are occasionally found.
Nerves. — The Splenii are supplied by the lateral branches of the posterior divisions of the
middle and lower cervical nerves.
Actions. — The Splenii of the two sides, acting together, draw the head directly backward.
assisting the Trapezius and Semispinalis capitis; acting separately, they draw the head to one
side, and slightly rotate it, turning the face to the same side. They also assist in supporting the
head in the erect position.
The Sacrospinalis {Erector spince) (Fig. 389), and its prolongations in the
thoracic and cervical regions, lie in the groove on the side of the vertebral column.
398
MYOLOGY
They are covered in the kimbar and thoracic regions by the lumbodorsal fascia,
and in the cervical region by the nuchal fascia. This large muscular and tendinous
Occipital bone
Midtmdiis
First thoracic vertebra
First lumbar vertebra
First sacral vertebra
t'
)■;
Fig. 389. — Deep muscles of the back.
THE DEEP MUSCLES OF THE BACK 399
mass varies in size and structure at different parts of the vertebral column. In
the sacral region it is narrow and pointed, and at its origin chiefly tendinous in
structure. In the lumbar region it is larger, and forms a thick fleshy mass which,
on being followed upward, is subdivided into three columns; these gradually
diminish in size as they ascend to be inserted into the vertebrae and ribs.
The Sacrospinalis arises from the anterior surface of a broad and thick tendon,
which is attached to the medial crest of the sacrum, to the spinous processes of
the lumbar and the eleventh and twelfth thoracic vertebrae, and the supraspinal
ligament, to the back part of the inner lip of the iliac crests and to the lateral
crests of the sacrum, where it blends with the sacrotuberous and posterior sacro-
iliac ligaments. Some of its fibers are continuous with the fibers of origin of the
Glutasus maximus. The muscular fibers form a large fleshy mass which splits,
in the upper lumbar region into three columns, viz., a lateral, the Iliocostalis, an
intermediate, the Longissimus, and a medial, the Spinalis. Each of these consists
from below upward, of three parts, as follows:
Lateral Column. Intermediate Column. Medial Column.
Iliocostalis. Longissimus. Spinalis.
(a) I. lumborum. {a) L. dorsi. (a) S. dorsi.
(6) I. dorsi. (6) L. cervicis. {h) S. cervicis.
(c) I. cervicis. (c) L. capitis. (c) S. capitis.
The Iliocostalis lumborum (Iliocostalis muscle; Sacrolumbalis muscle) is inserted,
by six or seven flattened tendons, into the inferior borders of the angles of the lower
six or seven ribs.
The Iliocostalis dorsi (Musculus accessorius) arises by flattened tendons from
the upper borders of the angles of the lower six ribs medial to the tendons of
insertion of the Iliocostalis lumborum; these become muscular, and are inserted
into the upper borders of the angles of the upper six ribs and into the back of the
transverse process of the seventh cervical vertebra.
The Iliocostalis cervicis (Cervicalis ascendens) arises from the angles of the third,
fourth, fifth, and sixth ribs, and is inserted into the posterior tubercles of the trans-
verse processes of the fourth, fifth, and sixth cervical vertebrse.
The Longissimus dorsi is the intermediate and largest of the continuations of
the Sacrospinalis. In the lumbar region, where it is as yet blended with the Ilio-
costalis lumborum, some of its fibers are attached to the whole length of the pos-
terior surfaces of the transverse processes and the accessory processes of the lumbar
vertebrae, and to the anterior layer of the lumbodorsal fascia. In the thoracic
region it is inserted, by rounded tendons, into the tips of the transverse processes
of all the thoracic vertebrae, and by fleshy processes into the lower nine or ten ribs
between their tubercles and angles.
The Longissimus cervicis {Transversalis cervicis), situated medial to the Longis-
simus dorsi, arises by long thin tendons from the summits of the transverse pro-
cesses of the upper four or five thoracic vertebrae, and is inserted by similar tendons
into the posterior tubercles of the transverse processes of the cervical vertebrae
from the second to the sixth inclusive.
The Longissimus capitis ( Trachelomastoid muscle) lies medial to the Longissimus
cervicis, between it and the Semispinalis capitis. It arises by tendons from the
transverse processes of the upper four or five thoracic vertebrae, and the artic-
ular processes of the lower three or four cervical vertebrae, and is inserted into the
posterior margin of the mastoid process, beneath the Splenius capitis and Sterno-
cleidomastoideus. It is almost always crossed by a tendinous intersection near
its insertion.
The Spinalis dorsi, the medial continuation of the Sacrospinalis, is scarcely
separable as a distinct muscle. It is situated at the medial side of the Longissimus
400 MYOLOGY
dorsi, and is intimately blended with it; it arises by three or four tendons from the
spinous processes of the first two lumbar and the last two thoracic vertebrae : these,
uniting, form a small muscle which is inserted by separate tendons into the spinous
processes of the upper thoracic vertebrae, the number varying from four to eight.
It is intimately united with the Semispinalis dorsi, situated beneath it.
The Spinalis cervicis {Spinalis colli) is an inconstant muscle, which arises from
the lower part of the ligamentum nuchae, the spinous process of the seventh cer-
vical, and sometimes from the spinous processes of the first and second thoracic
vertebrae, and is inserted into the spinous process of the axis, and occasionally into
the spinous processes of the two vertebrae below it.
The Spinalis capitis {Biventer cervicis) is usually inseparably connected with the
Semispinalis capitis (see below).
The Semispinalis dorsi consists of thin, narrow, fleshy fasciculi, interposed
between tendons of considerable length. It arises by a series of small tendons
from the transverse processes of the sixth to the tenth thoracic vertebrae, and is
inserted, by tendons, into the spinous processes of the upper four thoracic and lower
two cervical vertebrae.
The Semispinalis cervicis (Semispinalis colli), thicker than the preceding,
arises by a series of tendinous and fleshy fibers from the transverse processes of
the upper five or six thoracic vertebrae, and is inserted into the cervical spinous
processes, from the axis to the fifth inclusive. The fasciculus connected with the
axis is the largest, and is chiefly muscular in structure.
The Semispinalis capitis iComplexus) is situated at the upper and back part
of the neck, beneath the Splenius, and medial to the Longissimus cervicis and
capitis. It arises by a series of tendons from the tips of the transverse processes
of the upper six or seven thoracic and the seventh cervical vertebrae, and from the
articular processes of the three cervical above this. The tendons, uniting, form
a broad muscle, which passes upward, and is inserted between the superior and
inferior nuchal lines of the occipital bone. The medial part, usually more or less
distinct from the remainder of the muscle, is frequently termed the Spinalis capitis;
it is also named the Biventer cervicis since it is traversed by an imperfect tendinous
inscription.
The Multifidus {Mnltifidus spina) consists of a number of fleshy and tendinous
fasciculi, which fill up the groove on either side of the spinous processes of the ver-
tebrae, from the sacrum to the axis. In the sacral region, these fasciculi arise from
the back of the sacrum, as low as the fourth sacral foramen, from the aponeu-
rosis of origin of the Sacrospinalis, from the medial surface of the posterior superior
iliac spine, and from the posterior sacroiliac ligaments; in the lumbar region,
from all the mamillary processes; in the thoracic region, from all the transverse
processes; and in the cervical region, from the articular processes of the lower
four vertebrae. Each fasciculus, passing obliquely upward and medialward, is
inserted into the whole length of the spinous process of one of the vertebrae above.
These fasciculi vary in length: the most superficial, the longest, pass from one
vertebra to the third or fourth above; those next in order run from one vertebra
to the second or third above; while the deepest connect two contiguous vertebrae.
The Rotatores {Rotatores spinas) lie beneath the Multifidus and are found only
in the thoracic region; they are eleven in number on either side. Each muscle is
small and somewhat quadrilateral in form; it arises from the upper and back part of
the transverse process, and is inserted into the lower border and lateral surface of
the lamina of the vertebra above, the fibers extending as far as the root of the spinous
process. The first is found between the first and second thoracic vertebrae; the
last, between the eleventh and twelfth. Sometimes the number of these muscles
is diminished by the absence of one or more from the upper or lower end.
The Interspinales are short muscular fasciculi, placed in pairs between the
THE SUBOCCIPITAL MUSCLES 401
spinous processes of the contiguous vertebrae, one on either side of the interspinal
ligament. In the cervical region they are most distinct, and consist of six pairs,
the first being situated between the axis and third vertebra, and the last between
the seventh cervical and the first thoracic. They are small narrow bundles,
attached, above and below, to the apices of the spinous processes. In the thoracic
region, they are found between the first and second vertebra, and sometimes be-
tween the second and third, and between the eleventh and twelfth. In the lumbar
region there are four pairs in the intervals between the five lumbar vertebrse.
There is also occasionally one between the last thoracic and first lumbar, and one
between the fifth lumbar and the sacrum.
The Extensor coccygis is a slender muscular fasciculus, which is not always present; it extends
over the lower part of the posterior surface of the sacrum and coccyx. It arises by tendinous
fibers from the last segment of the sacrum, or first piece of the coccyx, and passes downward to
be inserted into the lower part of the coccyx. It is a rudiment of the Extensor muscle of the
caudal vertebrse of the lower animals.
The Intertransversarii (Intertransversales) are small muscles placed between
the transverse processes of the vertebrse. In the cervical region they are best
developed, consisting of rounded muscular and tendinous fasciculi, and are placed
in pairs, passing between the anterior and the posterior tubercles respectively of
the transverse processes of two contiguous vertebrse, and separated from one
another by an anterior primary division of the cervical nerve, which lies in the
groove between them. The muscles connecting the anterior tubercles are termed
the Intertransversarii anteriores; those between the posterior tubercles, the Inter-
transversarii posteriores; both sets are supplied by the anterior divisions of the
spinal nerves (Lickley^). There are seven pairs of these muscles, the first pair
being between the atlas and axis, and the last pair between the seventh cervical
and first thoracic vertebrse. In the thoracic region they are present between the
transverse processes of the lower three thoracic vertebrse, and between the trans-
verse processes of the last thoracic and the -first lumbar. In the lumbar region
they are arranged in pairs, on either side of the vertebral column, one set occupy-
ing the entire interspace between the transverse processes of the lumbar vertebrse,
the Intertransversarii laterales; the other set, Intertransversarii mediales, passing
from the accessory process of one vertebra to the mammillary of the vertebra below.
The Intertransversarii laterales are supplied by the anterior divisions, and the
Intertransversarii mediales by the posterior divisions of the spinal nerves (Lichley,
op. cit.).
n. THE SUBOCCIPITAL MUSCLES (Fig. 389).
The suboccipital group comprises:
Rectus capitis posterior major. Obliquus capitis inferior.
Rectus capitis posterior minor. Obliquus capitis superior.
The Rectus capitis posterior major {Rectus capitis posticus major) arises by a
pointed tendon from the spinous process of the axis, and, becoming broader as
it ascends, is inserted into the lateral part of the inferior nuchal line of the occipital
bone and the surface of the bone immediately below the line. As the muscles of
the two sides pass upward and lateralward, they leave between them a triangular
space, in which the Recti capitis posteriores minores are seen.
The Rectus capitis posterior minor (Rectus capitis posticus minor) arises by a
narrow pointed tendon from the tubercle on the posterior arch of the atlas, and,
widening as it ascends, is inserted into the medial part of the inferior nuchal line
of the occipital bone and the surface between it and the foramen magnum.
' Journal of Anatomy and Physiology, 1904, vol. xxxix.
26
402 MYOLOGY
The Obliquus capitis inferior {Ohliquus inferior), the larger of the two Oblique
muscles, arises from the apex of the spinous process of the axis, and passes lateral-
ward and slightly upward, to be inserted into the lower and back part of the
transverse process of the atlas.
The Obliquus capitis superior {Ohliquus superior), narrow below, wide and
expanded above, arises by tendinous fibers from the upper surface of the transverse
process of the atlas, joining with the insertion of the preceding. It passes upward
and medialward, and is inserted into the occipital bone, between the superior and
inferior nuchal lines, lateral to the Semispinalis capitis.
The Suboccipital Triangle. — Between the Obliqui and the Rectus capitis posterior major is
the suboccipital triangle. It is bounded, above and medially, by the Rectus capitis posterior
major; above and laterally, by the ObUquus capitis superior; below and laterally, by the Obhquus
capitis inferior. It is covered by a layer of dense fibro-fatty tissue, situated beneath the Semi-
spinalis capitis. The floor is formed by the posterior occipito-atlantal membrane, and the posterior
arch of the atlas. In the deep groove on the upper surface of the posterior arch of the atlas are
the vertebral artery and the first cervical or suboccipital nei've.
Nerves. — The deep muscles of the back and the suboccipital muscles are supplied by the
posterior primary divisions of the spinal nerves.
Actions. — The Sacrospinalis and its upward continuations and the Spinales serve to main-
tain the vertebral column in the erect posture; they also serve to bend the trunk backward when
it is required to counterbalance the influence of any weight at the front of the body — as, for
instance, when a heavy weight is suspended from the neck, or when there is any great abdominal
distension, as in pregnancy or dropsy; the peculiar gait under such circumstances depends upon
the vertebral column being drawn backward, by the counterbalancing action of the Sacrospinales.
The muscles which form the continuation of the Sacrospinales on to the head and neck steady
those parts and fix them in the upright position. If the Iliocostalis lumborum and Longissimus
dorsi of one side act, they serve to draw down the chest and vertebral column to the correspond-
ing side. The lUocostales cervicis, taking their fixed points from the cervical vertebrae, elevate
those ribs to which they are attached; taking their fixed points from the ribs, both muscles help
to extend the neck; wliile one muscle bends the neck to its own side. When both Longissimi
cervicis act from below, they bend the neck backward. When both Longissimi capitis act from
below, they bend the head backward; while, if only one muscle acts, the face is turned to the
side on which the muscle is acting, and then the head is bent to the shoulder. The two Recti
draw the head backward. The Rectus capitis posterior major, owing to its obliquity, rotates
the skull, with the atlas, around the odontoid process, turning the face to the same side. The
Multifidus acts successively upon the different parts of the column; thus, the sacrum furnishes
a fixed point from which the fasciculi of this muscle acts upon the lumbar region; which in turn
becomes the fixed point for the fasciculi moving the thoracic region, and so on throughout the
entire length of the column. The Multifidus also serves to rotate the column, so that the front
of the trunk is turned to the side opposite to that from which the muscle acts, this muscle being
assisted in its action by the Obliquus externus abdominis. The Obliquus capitis superior draws
the head backward and to its own side. The Obliquus inferior rotates the atlas, and with it the
skull, around the odontoid process, turning the face to the same side. When the Semispinales of
the two sides act together, they help to extend the vertebral column; when the muscles of only
one side act, they rotate the thoracic and cervical parts of the column, turning the body to the
opposite side. The Semispinales capitis draw the head directly backward; if one muscle acts,
it draws the head to one side, and rotates it so that the face is turned to the opposite side. The
Interspinales by approximating the spinous processes help to extend the column. The Inter-
transversarii approximate the transverse processes, and help to bend the column to one side.
The Rotatores assist the Multifidus to rotate the vertebral column, so that the front of the trunk
is turned to the side opposite to that from which the muscles act.
III. THE MUSCLES OF THE THORAX.
The muscles belonging to this group are the
Intercostales externi. Levatores costarum.
Intercostales interni. Serratus posterior superior.
Subcostales. Serratus posterior inferior.
Transversus thoracis. Diaphragm.
Intercostal Fasciae. — In each intercostal space thin but firm layers of fascia
cover the outer surface of the Intercostalis externus and the inner surface of the
THE MUSCLES OF THE THORAX 403
Intercostalis internus; and a third, more delicate layer, is interposed between the
two planes of muscular fibers. They are best marked in those situations where
the muscular fibers are deficient, as between the Intercostales externi and sternum
in front, and between the Intercostales interni and vertebral column behind.
The Intercostales (Intercostal muscles) (Fig. 411) are two thin planes of muscular
and tendinous fibers occupying each of the intercostal spaces. They are named
external and internal from their surface relations— the external being superficial
to the internal.
The Intercostales externi {External intercostals) are eleven in number on either
side.^ They extend from the tubercles of the ribs behind, to the cartilages of the
ribs in front, where they end in thin membranes, the anterior intercostal membranes,
which are continued forward to the sternum. Each arises from the lower border
of a rib, and is inserted into the upper border of the rib below. In the two lower
spaces they extend to the ends of the cartilages, and in the upper two or three
spaces they do not quite reach the ends of the ribs. They are thicker than the
Intercostales interni, and their fibers are directed obliquely downward and lateral-
ward on the back of the thorax, and downward, forward, and medialward on the front.
Variations.— Continuation with the Obhquus externus or Serratus anterior: A Supracostnlis
muscle, from the anterior end of the first rib down to the second, third or fourth ribs occasionally
occurs.
The Intercostales interni {Internal intercostals) are also eleven in number on
either side. They commence anteriorly at the sternum, in the interspaces between
the cartilages of the true ribs, and at the anterior extremities of the cartilages of
the false ribs, and extend backward as far as the angles of the ribs, whence they
are continued to the \'ertebral column by thin aponeuroses, the posterior intercostal
membranes. Each arises from the ridge on the inner surface of a rib, as well as
from the corresponding costal cartilage, and is inserted into the upper border
of the rib below. Their fibers are also directed obliquely, but pass in a direction
opposite to those of the Intercostales externi.
The Subcostales {Infracostaks) consist of muscular and aponeurotic fasciculi,
which are usually w^ll-developed only in the lower part of the thorax; each arises
from the inner surface of one rib near its angle, and is inserted into the inner
surface of the second or third rib below. Their fibers run in the same direction
as those of the Intercostales interni.
The Transversus thoracis {Triangidaris sterni) is a thin plane of muscular and
tendinous fibers, situated upon the inner surface of the front wall of the chest
(Fig. 390). It arises on either side from the lower third of the posterior surface
of the body of the sternum, from the posterior surface of the xiphoid process,
and from the sternal ends of the costal cartilages of the lower three or four true
ribs. Its fibers diverge upward and lateralward, to be inserted by slips into the
lower borders and inner surfaces of the costal cartilages of the second, third, fourth,
fifth, and sixth ribs. The lowest fibers of this muscle are horizontal in their direc-
tion, and are continuous with those of the Transversus abdominis; the intermediate
fibers are oblique, while the highest are almost vertical. This muscle varies in its
attachments, not only in different subjects, but on opposite sides of the same
subject.
The Levatores costarum (Fig. 389), twelve in number on either side, are small
tendinous and fleshy bundles, which arise from the ends of the transverse pro-
cesses of the seventh cervical and upper eleven thoracic vertebrae; they pass
obliquely downward and lateralward, like the fibers of the Intercostales externi,
and each is inserted into the outer surface of the rib immediately below the
vertebra from which it takes origin, between the tubercle and the angle (Levatores
costarum breves) . Each of the four lower muscles divides into two fasciculi, one
404
MYOLOGY
of which is inserted as above described; the other passes down to the second
rib below its origin (Levatores costanim longi) .
The Serratus posterior superior {Serraius posticus superior) is a thin, quadri-
lateral muscle, situated at the upper and back part of the thorax. It arises by
a thin and broad aponeurosis from the lower part of the ligamentum nuchae,
from the spinous processes of the seventh cervical and upper two or three thoracic
vertebrae and from the supraspinal liga-
ment. Inclining downward and lateral-
ward it becomes muscular, and is in-
serted, by four fleshy digitations, into
the upper borders of the second, third,
fourth, and fifth ribs, a little beyond
their angles.
Variations. — Increase or decrease in size and
number of slips or entire absence.
The Serratus posterior inferior {Ser-
ratus yosticus inferior) (Fig. 409) is sit-
uated at the junction of the thoracic
and lumbar regions: it is of an irreg-
ularly quadrilateral form, broader than
the preceding, and separated from it by
a wide interval. It arises bv a thin
aponeurosis from the spinous processes
of the lower two thoracic and upper two
or three lumbar vertebrae, and from
the supraspinal ligament. Passing
obliquely upward and lateralward, it
becomes fleshy, and divides into four
flat digitations, which are inserted into
the inferior borders of the lower four
ribs, a little beyond their angles. The
thin aponeurosis of origin is intimately
blended with the lumbodorsal fascia,
and aponeurosis of the Latissimus dorsi.
Sternal
origin of
Diaphragm
Fig. 390. — Posterior surface of sternum and costal
cartilages, showing Transversus thoracis.
Variations. — Increase or decrease in size and number of slips or entire absence.
Nerves. — The muscles of this group are supplied by the intercostal nerves.
The Diaphragm (Fig. 391) is a dome-shaped musculofibrous septum which
separates the thoracic from the abdominal cavity, its convex upper surface forming
the floor of the former, and its concave under surface the roof of the latter. Its
peripheral part consists of muscular fibers which take origin from the circumference
of the thoracic outlet and converge to be inserted into a" central tendon.
The muscular fibers may be grouped according to their origins into three parts
— sternal, costal, and lumbar. The sternal part arises by two fleshy slips from
the back of the xiphoid process; the costal part from the inner surfaces of the car-
tilages and adjacent portions of the lower six ribs on either side, interdigitating
with the Transversus abdominis; and the lumbar part from aponeurotic arches,
named the lumbocostal arches, and from the lumbar vertebrae by two pillars or
crura. There are two lumbocostal arches, a medial and a lateral, on either side.
The Medial Lumbocostal Arch (arcus lumhocostalis mediaUs [Ilalleri]; internal
arcuate ligament) is a tendinous arch in the fascia covering the upper part of the
Psoas major; medially, it is continuous with the lateral tendinous margin of the
corresponding crus, and is attached to the side of the body of the first or second
THE MUSCLES OF THE THORAX
405
lumbar vertebra; laterally, it is fixed to the front of the transverse process of the
first and, sometimes also, to that of the second lumbar vertebra.
The Lateral Lumbocostal Arch (arcus lumbocostalis lateralis [Ilalleri]; external
arcuate ligament)^ arches across the upper part of the Quadratus lumborum, and
is attached, medially, to the front of the transverse process of the first lumbar
vertebra, and, laterally, to the tip and lower margin of the twelfth rib.
The Crura. — At their origins the crura are tendinous in structure, and blend
with the anterior longitudinal ligament of the vertebral column. The right cms,
larger and longer than the left, arises from the anterior surfaces of the bodies and
intervertebral fibrocartilages of the upper three lumbar vertebra, while the left
crus arises from the corresponding parts of the upper two only. The medial ten-
dinous margins of the crura pass forward and medial ward, and meet in the middle
line to form an arch across the front of the aorta; this arch is often poorly defined.
Xiphoid process
Opening for Lesser Splanchnic
FiQ. 391. — The diaphragm. Under surface.
From this series of origins the fibers of the diaphragm converge to be inserted
into the central tendon. The fibers arising from the xiphoid process are very short,
and occasionally aponeurotic; those from the medial and lateral lumbocostal
arches, and more especially those from the ribs and their cartilages, are longer,
and describe marked curves as they ascend and converge to their insertion. The
fibers of the crura diverge as they ascend, the most lateral being directed upward
and lateralward to the central tendon. The medial fibers of the right crus ascend
on the left side of the esophageal hiatus, and occasionally a fasciculus of the left
crus crosses the aorta and runs obliquely through the fibers of the right crus toward
the vena caval foramen (Low^.
' Journal of Anatomy and Physiology, vol xlii
406 MYOLOGY
The Central Tendon. — The central tendon of the diaphragm is a thin but strong
aponeurosis situated near the center of the vault formed by the muscle, but some-
what closer to the front than to the back of the thorax, so that the posterior muscu-
lar fibers are the longer. It is situated immediately below the pericardium, with
which it is partially blended. It is shaped somewhat like a trefoil leaf, consisting
of three div' isions^ or leaflets separated from one another by slight indentations.
The right leaflet is the largest, the middle, directed toward the xiphoid process,
the next in size, and the left the smallest. In structure the tendon is composed
of several planes of fibers, which intersect one another at various angles and unite
into straight or curved bundles — an arrangement which gives it additional strength.
Openings in the Diaphragm. — The diaphragm is pierced by a series of apertures
to permit of the passage of structures between the thorax and abdomen. Three
large openings — the aortic, the esophageal, and the vena caval — and a series of
smaller ones are described.
The aortic hiatus is the low^est and most posterior of the large apertures; it lies
at the level of the twelfth thoracic vertebra. Strictly speaking, it is not an aperture
in the diaphragm but an osseoaponeurotic opening between it and the vertebral
column, and therefore behind the diaphragm; occasionally some tendinous fibers
prolonged across the bodies of the vertebrae from the medial parts of the lower ends
of the crura pass behind the aorta, and thus convert the hiatus into a fibrous ring.
The hiatus is situated slightly to the left of the middle line, and is bounded in front
by the crura, and behind by the body of the first lumbar vertebra. Through it
pass the aorta, the azygos vein, and the thoracic duct; occasionally the azygos
vein is transmitted through the right crus.
The esophageal hiatus is situated in the muscular part of the diaphragm at
the level of the tenth thoracic vertebra, and is elliptical in shape. It is placed
above, in front, and a little to the left of the aortic hiatus, and transmits the
esophagus, the vagus nerves, and some small esophageal arteries.
The vena caval foramen is the highest of the three, and is situated about the level
of the fibrocartilage between the eighth and ninth thoracic vertebrae. It is quad-
rilateral in form, and is placed at the junction of the right and middle leaflets
of the central tendon, so that its margins are tendinous. It transmits the inferior
vena cava, the wall of which is adherent to the margins of the opening, and some
branches of the right phrenic nerve.
Of the lesser apertures, two in the right crus transmit the greater and lesser
right splanchnic nerves; three in the left crus give passage to the greater and lesser
left splanchnic nerves and the hemiazygos vein. The gangliated trunks of the
sympathetic usually enter the abdominal cavity behind the diaphragm, under
the medial lumbocostal arches.
On either side two small intervals exist at which the muscular fibers of the
diaphragm are deficient and are replaced by areolar tissue. One between the
sternal and costal parts transmits the superior epigastric branch of the internal
mammary artery and some lymphatics from the abdominal wall and convex
surface of the liver. The other, between the fibers springing from the medial and
lateral lumbocostal arches, is less constant; when this interval exists, the upper
and back part of the kidney is separated from the pleura by areolar tissue only.
Variations. — The sternal portion of the muscle is sometimes wanting and more rarely defects
occur in the lateral part of the central tendon or adjoining muscle fibers.
Nerves. — The diaphragm is supphed by the phrenic and lower intercostal nerves.
Actions. — -The diaphragm is the principal muscle of inspiration, and presents the form of
a dome concave toward the abdomen. The central part of the dome is tendinous, and the peri-
cardium is attached to its upper surface; the circumference is muscular. During inspiration the
lowest ribs are fixed, and from these and the crura the muscular fibers contract and draw dowTi-
ward and forward the central tendon with the attached pericardium. In this movement the
curvature of the diaphragm is scarcely altered, the dome moving downward nearly parallel
THE MUSCLES OF THE THORAX 407
to its original position and pushing before it the abdominal viscera. The descent of the abdominal
viscera is permitted by the elasticity of the abdominal wall, but the hmit of this is soon reached.
The central tendon apphed to the abdominal viscera then becomes a fixed point for the action
of the diaphragm, the effect of which is to elevate the lower ribs and through them to push
forward the body of the sternum and the upper ribs. The right cupola of the diaphragm,
lying on the liver, has a greater resistance to overcome than the left, which lies over the stomach,
but to compensate for this the right crus and the fibers of the right side generally are stronger
than those of the left.
In a,ll expulsive acts the diaphragm is called into action to give additional power to each
expulsive effort. Thus, before sneezing, coughing, laughing, crying, or vomiting, and previous
to the expulsion of urine or feces, or of the fetus from the uterus, a deep inspiration takes place.
The height of the diaphragm is constantly varying during respiration; it also varies with the
degree of distension of the stomach and intestines and with the size of the liver. After a forced
expiration the right cupola is on a level in front with the fourth costal cartilage, at the side with
the fifth, sixth, and seventh ribs, and behind with the eighth rib; the left cupola is a little lower
than the right. Halls Dally' states that the absolute range of movement between deep inspira-
tion and deep expiration averages in the male and female 30 mm. on the right side and 28 mm.
on the left; in quiet respiration the average movement, is 12.5 mm. on the right side and 12 mm.
on the left.
Skiagraphy shows that the height of the diaphragm in the thorax varies considerably with
the position of the body. It stands highest when the body is horizontal and the jxatient on his
back, and in this position it performs the largest respiratory excursions with normal breathing.
When the body is erect the dome of the diaphragm falls, and its respiratory movements become
smaller. The dome falls still lower when the sitting posture is assumed, and in this position its
respiratory excursions are smallest. These facts may, perhaps, exjjlain why it is that patients
suffering from severe dyspnoea are most comfortable and least short of breath when they sit up.
When the body is horizontal and the patient on his side, the two halves of the diaphragm do
not behave alike. The uppermost half sinks to a level lower even than when the patient sits,
and moves httle with respiration; the lower half rises higher in the thorax than it does when the
patient is supine, and its respiratory excursions are much increased. In unilateral disease of the
pleura or lungs analogous interference with the position or movement of the diaphragm can
generally be observed skiagraphically.
It appears that the position of the diaphragm in the thorax depends upon three main factors,
viz.: (1) the elastic retraction of the lung tissue, tending to pull it upward; (2) the pressure
exerted on its under surface by the viscera; this naturally tends to be a negative pressure, or down-
ward suction, when the patient sits or stands, and positive, or an upward pressure, when he lies;
(3) the intra-abdominal tension due to the abdominal muscles. These are in a state of contrac-
tion in the standing position and not in the sitting; hence the diaphragm, when the patient
stands, is pushed up higher than when he sits.
The Intercostales interni and extcrni have probably no action in moving the ribs. They con-
tract simultaneously and form strong elastic supports which prevent the intercostal spaces being
pushed out or drawn in during respiration. The anterior portions of the Intercostales interni
probably have an additional function in keeping the sternocostal and interchondral joint sur-
faces in apposition, the posterior parts of the Intercostales externi performing a similar function
for the costovertebral articulations. The Levatores costarum being inserted near the fulcra of
the ribs can have little action on the ribs ; they act as rotators and lateral flexors of the vertebral
column. The Transversus thoracis draws down the costal cartilages, and is therefore a muscle
of expiration.
The Serrati are respiratory muscles. The Serratus posterior superior elevates the ribs and
is therefore an inspiratory muscle. The Serratus posterior inferior draws the lower ribs down-
ward and backward, and thus elongates the thorax; it also fixes the lower ribs, thus assisting
the inspiratory action of the diaphragm and resisting the tendency it has to draw the lower
ribs upward and forward. It must therefore be regarded as a muscle of inspiration.
Mechanism of Respiration. — ^The respiratory movements must be examined during (a) quiet
respiration, and (6) deep respiration.
Quiet Respiration. — -The first and second pairs of ribs are fixed by the resistance of the cervical
structures; the last pair, and through it the eleventh, by the Quadratus lumborum. The other
ribs are elevated, so that the first two intercostal spaces are diminished while the others are
increased in width. It has already been shown (p. 304) that elevation of the third, fourth, fifth,
and sixth ribs leads to an increase in the antero-posterior and transverse diameters of the thorax;
the vertical diameter is increased by the descent of the diaphragmatic dome so that the lungs
are expanded in all directions except backward and upward. Elevation of the eighth, ninth,
and tenth ribs is accompanied by a lateral and backward movement, leading to an increase in
the transverse diameter of the upper part of the abdomen; the elasticity of the anterior abdominal
' Journal of Anatomy and Physiology, 1908, vol. xliii.
408 MYOLOGY
wall allows a slight increase in the antero-posterior diameter of this part, and in this waj- the
decrease in the vertical diameter of the abdomen is compensated and space provided for its
displaced viscera. Expiration is effected bj- the elastic recoil of its walls and by the action of
the abdominal muscles, which push back the viscera displaced downward by the diaphragm.
Deep Respiration. — All the movements of quiet respiration are here carried out, but to a
greater extent. In deep inspiration the shoulders and the vertebral borders of the scapulae are
fixed and the limb muscles, Trapezius, Serratus anterior, Pectorales, and Latissimus dorsi, are
called into play. The Scaleni are in strong action, and the Sternocleidomastoidei also assist
when the head is fixed by drawing up the sternum and by fixing the clavicles. The first rib is
therefore no longer stationary, but, with the sternum, is raised; with it all the other ribs except
the last are raised to a higher level. In conjunction with the increased descent of the diaphragm
this provides for a considerable augmentation of all the thoracic diameters. The anterior abdomi-
nal muscles come into action so that the umbihcus is drawn upward and backward, but this
allows the diaphragm to exert a more powerful influence on the lower ribs; the transverse diam-
eter of the upper part of the abdomen is greatly increased and the subcostal angle opened out.
The deeper muscles of the back, e. g., the Serrati posteriores superiores and the Sacrospinales
and their continuations, are also brought into action; the thoracic ciu-ve of the vertebral cohmin
is partially straightened, and the whole column, above the lower lumbar vertebrae, drawn back-
ward. This increases the antero-posterior diameters of the thorax and upper part of the abdomen
and widens the intercostal spaces. Deep ex-piration is effected bj- the recoil of the waUs and by
the contraction of the antero-lateral muscles of the abdominal wall, and the Serrati posteriores
inferiores and Transversus thoracis.
Halls Dally (op. cit.) gives the following figures as representing the average changes which
occur during deepest possible respiration. The manubriimi sterni moves 30 mm. in an upward
and 14 mm. in a forward direction; the width of the subcostal angle, at a level of 30 mm. below
the articulation between the body of the sternum and the xiphoid process, is increased bj' 26
mm,; the umbilicus is retracted and drawn upward for a distance of 13 mm.
IV. THE MUSCLES AND FASCLE OF THE ABDOMEN.
The muscles of the abdomen may be divided into two groups: (1) the antero-
lateral muscles; (2) the posterior muscles.
1. The Antero-lateral Muscles of the Abdomen.
The muscles of this group are:
Obliquus externus. Transversus.
Obliquus internus. Rectus.
Pyramidalis.
The Superficial Fascia. — The superficial fascia of the abdomen consists, over the
greater part of the abdominal wall, of a single layer containing a variable amount
of fat; but near the groin it is easily divisible into two layers, between which are
found the superficial vessels and nerves and the superficial inguinal lymph glands.
The superficial layer {fascia of Camper) is thick, areolar in texture, and contains
in its meshes a varying quantity of adipose tissue. Below, it passes over the
inguinal ligament, and is continuous with the superficial fascia of the thigh. In
the male. Camper's fascia is continued over the penis and outer surface of the
spermatic cord to the scrotum, where it helps to form the dartos. As it passes to
the scrotum it changes its characteristics, becoming thin, destitute of adipose tissue,
and of a pale reddish color, and in the scrotum it acquires some involuntary
muscular fibers. From the scrotum it may be traced backward into continuity
with the superficial fascia of the perineum. In the female. Camper's fascia is
continued from the abdomen into the labia majora.
The deep layer (fascia of Scarpa) is thinner and more membranous in character
than the superficial, and contains a considerable quantity of yellow elastic fibers.
It is loosely connected by areolar tissue to the aponeurosis of the Obliquus externus
abdominis, but in the middle line it is more intimately adherent to the linea alba
and to the s^^nphysis pubis, and is prolonged on to the dorsum of the penis, form-
THE ANTERO-LATERAL MUSCLES OF THE ABDOMEN 409
ing the fundiform ligament; above, it is continuous with the superficial fascia
over the rest of the trunk; below and laterally, it blends with the fascia lata of
the thigh a little below the inguinal ligament; medially and below, it is continued
over the penis and spermatic cord to the scrotum, where it helps to form the dartos.
From the scrotum it may be traced backward into continuity with the deep laver
of the superficial fascia of the perineum (fascia of Colles). In the female, it is con-
tinued into the labia majora and thence to the fascia of Colles.
Stihcuta-Mous
inffuinal ring —
Lacimar
ligament
Fig. 392. — The Obliquus extemus abdominia.
The Obliquus externus abdominis {External or descending oblique muscle) (Fig.
392), situated on the lateral and anterior parts of the abdomen, is the largest and
the most superficial of the three flat muscles in this region. It is broad, thin, and
irregularly quadrilateral, its muscular portion occupying the side, its aponeurosis
the anterior wall of the abdomen. It arises, by eight fleshy digitations, from the
external surfaces and inferior borders of the lower eight ribs; these digitations
are arranged in an oblique line which runs dowjiward and backward, the upper
410 MYOLOGY
ones being attached close to the cartilages of the corresponding ribs, the lowest
to the apex of the cartilage of the last rib, the intermediate ones to the ribs at
some distance from their cartilages. The five superior serrations increase in size
from above downward, and are received between corresponding processes of the
Serratus anterior; the three lower ones diminish in size from above dow^nward
and receive between them corresponding processes from the Latissimus dorsi.
From these attachments the fleshy fibers proceed in various directions. Those
from the lowest ribs pass nearly vertically downward, and are inserted into the
anterior half of the outer lip of the iliac crest ; the middle and upper fibers, directed
downward and forward, end in an aponeurosis, opposite a line drawn from the
prominence of the ninth costal cartilage to the anterior superior iliac spine.
The aponeurosis of the Obliquus externus abdominis is a thin but strong mem-
branous structure, the fibers of which are directed downward and medialward.
It is joined with that of the opposite muscle along the middle line, and covers
the whole of the front of the abdomen; above, it is covered by and gives origin
to the lower fibers of the Pectoralis major; below, its fibers are closely aggregated
together, and extend obliquely across from the anterior superior iliac spine to
the pubic tubercle and the pectineal line. In the middle line, it interlaces with
the aponeurosis of the opposite muscle, forming the linea alba, which extends from
the xiphoid process to the symphysis pubis.
That portion of the aponeurosis which extends between the anterior superior
iliac spine and the pubic tubercle is a thick band, folded inward, and continuous
below with the fascia lata; it is called the inguinal ligament. The portion which
is reflected from the inguinal ligament at the pubic tubercle is attached to the
pectineal line and is called the lacunar ligament. From the point of attachment
of the latter to the pectineal line, a few fibers pass upward and medialward, behind
the medial crus of the subcutaneous inguinal ring, to the linea alba; they diverge
as they ascend, and form a thin triangular fibrous band which is called the reflected
inguinal ligament.
In the aponeurosis of the Obliquus externus, immediately above the crest of
the pubis, is a triangular opening, the subcutaneous inguinal ring, formed by a
separation of the fibers of the aponeurosis in this situation.
The following structures require further description, viz., the subcutaneous
inguinal ring, the intercrural fibers and fascia, and the inguinal, lacunar, and reflected
inguinal ligaments.
The Subcutaneous Inguinal Ring {annulus inguinalis subcutaneiis; external
abdominal ring) (Fig. 393). — The subcutaneous inguinal ring is an interval in the
aponeurosis of the Obliquus externus, just above and lateral to the crest of the
pubis. The aperture is oblique in direction, somewhat triangular in form, and
corresponds with the course of the fibers of the aponeurosis. It usually measures
from base to apex about 2.5 cm., and transversely about 1.25 cm. It is bounded
below by the crest of the pubis; on either side by the margins of the opening in the
aponeurosis, which are called the crura of the ring; and above, by a series of curved
■ intercrural fibers. The inferior crus {external lyillar) is the stronger and is formed by
that portion of the inguinal ligament which is inserted into the pubic tubercle;
it is curved so as to form a kind of groove, upon which, in the male, the spermatic
cord rests. The superior crus {internal pillar) is a broad, thin, flat band, attached to
the front of the symphysis pubis and interlacing with its fellow of the opposite side.
The subcutaneous inguinal ring gives passage to the spermatic cord and ilio-
inguinal nerve in the male, and to the round ligament of the uterus and the
ilioinguinal nerve in the female; it is much larger in men than in women, on
account of the large size of the spermatic cord.
The Intercrural Fibers {fibro' intercrurales; intercolumnar fibers). — The intercrural
fibers are a series of curved tendinous fibers, which arch across the lower part of
THE ANTERO-LATERAL MUSCLES OF THE ABDOMEN
411
the aponeurosis of the Obliquus externus, describing curves with the convexities
downward. They have received their name from stretching across between the
two crura of the subcutaneous inguinal ring, and the}- are much thicker and stronger
at the inferior crus, where they are connected to the inguinal ligament, than supe-
riorly, where they are inserted into the linea alba. The intercrural fibers increase
the strength of the lower part of the aponeurosis, and prevent the divergence of
the crura from one another; they are more strongly developed in the male than in
the female.
As they pass across the subcutaneous inguinal ring, they are connected togetlier
by delicate fibrous tissue, forming a fascia, called the intercrural fascia. This inter-
Superficial iliac
circumflex vein
Subcutaneous inguinal
ring
Superficial epigastric vein
Fig. 393. — The subcutaneous inguinal ring.
crural fascia is continued down as a tubular prolongation around the spermatic
cord and testis, and encloses them in a sheath ; hence it is also called the external
spermatic fascia. The subcutaneous inguinal ring is seen as a distinct aperture
only after the intercrural fascia has been removed.
The Inguinal Ligament {ligamentwn inguinale [Pouparti] ; Poupart's ligament)
(Fig. 394). — The inguinal ligament is the lower border of the aponeurosis of the
Obliquus externus, and extends from the anterior superior iliac spine to the pubic
tubercle. From this latter point it is reflected backward and lateralward to be
attached to the pectineal line for about 1.25 cm., forming the lacunar ligament.
Its general direction is convex downward toward the thigh, where it is continuous
with the fascia lata. Its lateral half is rounded, and oblique in direction; its
412
MYOLOGY
medial half gradually widens at its attachment to the pubis, is more horizontal
in direction, and lies beneath the spermatic cord.
The Lacunar Ligament (ligamentum lacunare [Gimhernati] ; Gimbernafs ligament)
(Fig. 394). — The lacunar ligament is that part of the aponeurosis of the Obliquus
externus which is reflected backward and lateral ward, and is attached to the pecti-
neal line. It is about 1.25 cm. long, larger in the male than in the female, almost
horizontal in direction in the erect posture, and of a triangular form with the base
directed lateralward. Its base is concave, thin, and sharp, and forms the medial
boundary of the femoral ring. Its apex corresponds to the pubic tubercle. Its
posterior margin is attached to the pectineal line, and is continuous with the
pectineal fascia. Its anterior margin is attached to the inguinal ligament. Its
surfaces are directed upward and downward.
A)it. sup. iliac spine.
Obturator can/jl
Lacunar ligament
Pvhic tubercle
Symphysis
jjubis
Transverse acetabular
ligament
Fig. 394. — The inguinal and lacunar ligaments.
The Reflected Inguinal Ligament [ligamentum inguinale reflexum [Collesi] ; triari-
gular fascia). — The reflected inguinal ligament is a layer of tendinous fibers of a
triangular shape, formed by an expansion from the lacunar ligament and the inferior
crus of the subcutaneous inguinal ring. It passes medialward behind the spermatic
cord, and expands into a somewhat fan-shaped band, lying behind the superior
crus of the subcutaneous inguinal ring, and in front of the inguinal aponeurotic
falx, and interlaces with the ligament of the other side of the linea alba (Fig. 396).
Ligament of Cooper. — This is a strong fibrous band, which was first described by Sir Astley
Cooper. It extends lateralward from the base of the lacunar ligament (Fig. 39-1) along the
pectineal hne, to which it is attached. It is strengthened by the pectineal fascia, and by a
lateral expansion from the lower attachment of the linea alba {adminiculum linea; alhce).
Variations. — The Obliquus externus may show decrease or doubling of its attachments to the
ribs; addition slips from lumbar aponeurosis; doubling between lower ribs and ilium or inguinal
ligament. Rarely tendinous inscriptions occur.
The Obliquus intemus abdominis (Internal or ascending oblique muscle) (Fig.
395), thinner and smaller than the Obliquus externus, beneath which it lies, is of
THE ANTERO-LATERAL MUSCLES OF THE ABDOMEN
413
an irregularly quadrilateral form, and situated at the lateral and anterior parts
of the abdomen. It arises, by fleshy fibers, from the lateral half of the grooved
upper surface of the inguinal ligament, from the anterior two-thirds of the middle
lip of the iliac crest, and from the posterior lamella of the lumbodorsal fascia.
From this origin the fibers diverge; those from the inguinal ligament, few in number
and paler in color than the rest, arch downward and medialward across the sper-
matic cord in the male and the round ligament of the uterus in the female, and,
becoming tendinous, are inserted, conjointly with those of the Transversus, into
the crest of the pubis and medial part of the pectineal line behind the lacunar
ligament, forming what is known as the inguinal aponeurotic falx. Those from the
Inguinal apo-
murotic falx
Cremaster
Fig. 395. — The Obliquua internus abdominis.
anterior third of the iliac origin are horizontal in their direction, and, becoming
tendinous along the lower fourth of the linea semilunaris, pass in front of the Rectus
abdominis to be inserted into the linea alba. Those arising from the middle third
of the iliac origin run obliquely upward and medialward, and end in an aponeurosis;
this divides at the lateral border of the Rectus into two lamellae, which are con-
tinued forward, one in front of and the other behind this muscle, to the linea alba:
the posterior lamella has an attachment to the cartilages of the seventh, eighth,
and ninth ribs. The most posterior fibers pass almost vertically upward, to be
inserted into the inferior borders of the cartilages of the three lower ribs, being
continuous with the Intercostales interni.
414
MYOLOGY
Variations. — Occasionally, tendinous inscriptions occur from the tips of the tenth or eleventh
cartilages or even from the ninth; an additional slip to the ninth cartilage is sometimes found;
separation between ihac and inguinal parts may occur.
The Cremaster (Fig. 396) is a thin muscular layer, composed of a number of
fasciculi which arise from the middle of the inguinal ligament where its fibers
are continuous with those of the
Obliquus internus and also occasion-
ally with the Transversus. It passes
along the lateral side of the spermatic
cord, descends with it through the sub-
cutaneous'inguinal ring upon the front
and sides of the cord, and forms a series
of loops which differ in thickness and
length in different subjects. At the
upper part of the cord the loops are
short, but they become in succession
longer andJonger, the longest reaching
down as low as the testis, where a few
are inserted into the tunica vaginalis.
These loops are united together by
areolar tissue, and form a thin cover-
ing over the cord and testis, the cremas-
teric fascia. The fibers ascend along
the medial side of the cord, and are
inserted by a small pointed tendon
into the tubercle and crest of the
pubis and into the front of the sheath
of the Rectus abdominis.
The Transversus abdominis {Trans-
versalis iiniscle) (Fig. 397), so called
from the direction of its fibers, is the
most internal of the flat muscles of
the abdomen, being placed imme-
diately beneath the Obliquus internus. It arises, by fleshy fibers, from the
lateral third of the inguinal ligament, from tlie anterior three-fourths of the inner
lip of the iliac crest, from the inner surfaces of the cartilages of the lower six
ribs, interdigitating with the diaphragm, and from the lumbodorsal fascia.
The muscle ends in front in a broad aponeurosis, the lower fibers of which
curve downward and medialward, and are inserted, together with those of the
Obliquus internus, into the crest of the pubis and pectineal line, forming the ingui-
nal aponeurotic falx. Throughout the rest of its extent the aponeurosis passes
horizontally to the middle line, and is inserted into the linea alba; its upper
three-fourths lie behind the Rectus and blend with the posterior lamella of the
aponeurosis of the Obliquus internus; its lower fourth is in front of the Rectus.
Variations. — It may be more or less fused with the Obliquus internus or absent. The
spermatic cord may pierce its lower border. Slender muscle slips from the ileopectineal line to
transversalis fascia, the aponeurosis of the Transversus abdominis, or the outer end of the linea
semicircularis and other slender slips are occasionally found.
The inguinal aponeurotic falx {falx aponeurotica inguinalis; conjoined tendon of
Internal oblique and Transversalis muscle) of the Obliquus internus and Trans-
versus is mainly formed by the lower part of the tendon of the Transversus, and
is inserted into the crest of the pubis and pectineal line immediately behind
the subcutaneous inguinal ring, serving to protect what would otherwise be a
•^^
Fig. 396. — The Cremaster.
THE ANTERO-LATERAL MUSCLES OF THE ABDOMEN
415
weak point in the abdominal Mall. Lateral to the falx is a ligamentous band con-
nected with the lower margin of the Transversus and extending down in front of the
inferior epigastric artery to the superior ramus of the pubis; it is termed the inter-
foveolar ligament of Hesselbach (Fig. 398) and sometimes contains a few muscular
fibers.
Ltnea alba — m~]
Fig. 397. — The Transversus abdominis, Rectus abdominis, and Pyramidalis.
The Rectus abdominis (Fig. 397) is a long flat muscle, which extends along
the whole length of the front of the abdomen, and is separated from its fellow
of the opposite side by the linea alba. It is much broader, but thinner, above than
below, and arises by two tendons; the lateral or larger is attached to the crest
of the pubis, the medial interlaces with its fellow of the opposite side, and is con-
nected with the ligaments covering the front of the symphysis pubis. The muscle
is inserted by three portions of unequal size into the cartilages of the fifth, sixth,
and seventh ribs. The upper portion, attached principally to the cartilage of the
416
MYOLOGY
fifth rib, usually has some fibers of insertion into the anterior extremity of the rib
itself. Some fibers are occasionally connected with the costoxiphoid ligaments,
and the side of the xiphoid process.
The Rectus is crossed by fibrous bands, three in number, which are named the
tendinous inscriptions; one is usually situated opposite the umbilicus, one at the
extremity of the xiphoid process, and the third about midway between the xiphoid
process and the umbilicus. These inscriptions pass transversely or obliquely
across the muscle in a zigzag course; they rarely extend completely through its
substance and may pass only halfway across it; they are intimately adherent in
front to the sheath of the muscle. Sometimes one or two additional inscriptions,
generally incomplete, are present below the umbilicus.
Linea
semicircularis
Transversus
Reetus
abdominis
Inferior epigastric
artery and vein
Obliquus
internus
Inguinal ajmne^irotic fulx Interjoveolar ligament
Fig. 398. — The interfoveolar ligament, seen from in front. (Modified from Braune.)
The Rectus is enclosed in a sheath (Fig. 399) formed by the aponeuroses of the
Obliqui and Transversus, which are arranged in the following manner. At the lateral
margin of the Rectus, the aponeurosis of the Obliquus internus divides into two
lamellae, one of which passes in front of the Rectus, blending with the aponeurosis
of the Obliquus externus, the other, behind it, blending with the aponeurosis of
the Transversus, and these, joining again at the medial border of the Rectus,
are inserted into the linea alba. This arrangement of the aponeurosis exists from
the costal margin to midway between the umbilicus and symphysis pubis, where
the posterior wall of the sheath ends in a thin curved margin, the linea semicircu-
laris, the concavity of which is directed downward : below this level the aponeuroses
of all three muscles pass in front of the Rectus. The Rectus, in the situation where
its sheath is deficient below, is separated from the peritoneum by the transversalis
fascia (Fig. 400). Since the tendons of the Obliquus internus and Transversus
only reach as high as the costal margin, it follows that above this level the sheath
of the Rectus is deficient behind, the muscle resting directly on the cartilages of
the ribs, and being covered merely by the tendon of the Obliquus externus.
The Pyramidalis (Fig. 397) is a small triangular muscle, placed at the lower
part of the abdomen, in front of the Rectus, and contained in the sheath of that
THE ANTERO-LATERAL MUSCLES OF THE ABDOMEN
417
muscle. It arises by tendinous fibers from the front of the pubis and the anterior
pubic ligament; the fleshy portion of the muscle passes, upward, diminishing
in size as it ascends, and ends by a pointed extremity which is inserted into the
linea alba, midway between the umbilicus and pubis. This muscle may be wanting
on one or both sides; the lower end of the Rectus then becomes proportionately
increased in size. Occasionally it is double on one side, and the muscles of the two
sides are sometimes of unequal size. It may extend higher than the level stated.
Peritoneum
Transversalis fascia
Linea alba
Transversus
Fig. 399. — Diagram of sheath of Rectus.
Besides the Rectus and Pyramidalis, the sheath of the Rectus contains the superior and inferior
epigastric arteries, and the lower intercostal nerves.
Variations.— The Rectus may insert as high as the fourth or third rib or may fail to reach the
fifth. Fillers may spring from the lower part of the linea allia.
Nerves. — -The abdominal muscles are suppUed by the lower intercostal nerves. The Obliquus
internus and Transversus also receive filaments from the anterior branch of the iliohypogastric
and sometimes from the iUoinguinal. The Cremaster is supplied by the external spermatic branch
of the genitofemoral and the PjTamidaUs usually by the twelfth thoracic.
The Linea Alba. — The linea alba is a tendinous raphe in the middle line of the abdomen,
stretching between the xiphoid process and the symphysis pubis. It is placed between the medial
borders of the Recti, and is formed by the blending of the aponeuroses of the Obliqui and Trans-
versi. It is narrow below, corresponding to the Unear interval existing between the Recti; but
broader above, where these muscles diverge from one another. At its lower end the linea alba
has a double attachment — its superficial fibers passing in front of the medial heads of the Recti
to the symphysis pubis, while its deeper fibers form a triangular lamella, attached behind the
Recti to the posterior lip of the crest of the pubis, and named the adminiculum linese albae.
It presents apertures for, the passage of vessels and nerves; the umbilicus, which in the fetus
exists as an aperture and transmits the umbilical vessels, is closed in the adult.
Peritoneum , ObUqum exteryius .
Transversalis fascia
,1 Obliquus intermis ■
Linea alba
Transversus y
Fig. 400. — Diagram of a transverse section through the anterior abdomina wall, below the linea semicircularis
The Linese Semilunares. — -The linese semilimares are two curved tendinous lines placed one
on either side of the linea alba. Each corresponds with the lateral border of the Rectus, extends
from the cartilage of the ninth rib to the pubic tubercle, and is formed by the aponeurosis of the
Obliquus internus at its line of division to enclose the Rectus, reinforced in front by that of the
Obliquus externus, and behind by that of the Transversus.
Actions. — When the pelvis and thorax are fixed, the abdominal muscles compress the abdominal
viscera by constricting the cavity of the abdomen, in which action they are materially assisted
by the descent of the diaphragm. By these means assistance is given in expelling the feces
from the rectum, the urine from the bladder, the fetus from the uterus, and the contents of the
stomach in vomiting.
If the pelvis and vertebral column be fixed, these muscles compress the lower part of the thorax,
materially assisting e.xpiration. If the pelvis alone be fixed, the thorax is bent directly forward,
when the muscles of both sides act; when the muscles of only one side contract, the trunk is bent
toward that side and rotated toward the opposite side.
27
418 MYOLOGY
If the thorax be fixed, the muscles, acting together, draw the pelvis upward, as in climbing;
or, acting singly, they draw the pelvis upward, and bend the vertebral column to one side or the
other. The Recti, acting from below, depress the thorax, and consequently flex the vertebral
column; when acting from above, they flex the pelvis upon the vertebral column. The Pyramidales
are tensors of the linea alba.
The Transversalis Fascia. — The transversalis fascia is a thin aponeurotic membrane
which lies between the inner surface of the Transversus and the extraperitoneal
fat. It forms part of the general layer of fascia lining the abdominal parietes, and
is directly continuous with the iliac and pelvic fasciae. In the inguinal region,
the transversalis fascia is thick and dense in structure and is joined by fibers from
the aponeurosis of the Transversus, but it becomes thin as it ascends to the dia-
phragm, and blends with the fascia covering the under surface of this muscle.
BeJiind, it is lost in the fat which covers the posterior surfaces of the kidneys.
Below, it has the folloAving attachments : posteriorly, to the whole length of the iliac
crest, between the attachments of the Transversus and Iliacus; between the ante-
rior superior iliac spine and the femoral vessels it is connected to the posterior
margin of the inguinal ligament, and is there continuous with the iliac fascia.
Medial to the femoral vessels it is thin and attached to the pubis and pectineal
line, behind the inguinal aponeurotic falx, with which it is united; it descends in
front of the femoral vessels to form the anterior wall of the femoral sheath. Beneath
the inguinal ligament it is strengthened by a band of fibrous tissue, which is only
loosely connected to the ligament, and is specialized as the deep crural arch. The
spermatic cord in the male and the round ligament of the uterus in the female
pass through the transversalis fascia at a spot called the abdominal inguinal ring.
This opening is not visible externally, since the transversalis fascia is prolonged on
these structures as the infundibuliform fascia.
The Abdominal Inguinal Ring {annuhis inguinalis abdominis; internal or deep
abdominal ring). — The abdominal inguinal ring is situated in the transversalis
fascia, midway between the anterior superior iliac spine and the symphysis pubis,
and about 1.25 cm. above the inguinal ligament (Fig. 401). It is of an oval form,
the long axis of the oval being vertical; it varies in size in different subjects, and
is much larger in the male than in the female. It is bounded, above and laterally,
by the arched lower margin of the Transversus ; 6e/oii^' and medially, by the inferior
epigastric vessels. It transmits the spermatic cord in the male and the round
ligament of the uterus in the female. From its circumference a thin funnel-shaped
membrane, the infundibuliform fascia, is continued around the cord and testis,
enclosing them in a distinct covering.
The Inguinal Canal (canalis inguinalis; spermatic canal). — The inguinal canal
contains the spermatic cord and the ilioinguinal nerve in the male, and the round
ligament of the uterus and the ilioinguinal nerve in the female. It is an oblique
canal about 4 cm. long, slanting downward and medialward, and placed parallel
with and a little above the inguinal ligament; it extends from the abdominal
inguinal ring to the subcutaneous inguinal ring. It is bounded, in front, by the
integument and superficial fascia, by the aponeurosis of the Obliquus externus
throughout its whole length, and by the Obliquus internus in its lateral third;
behind, hy the reflected inguinal ligament, the inguinal aponeurotic falx, the trans-
versalis fascia, the extraperitoneal connective tissue and the peritoneum; above,
by the arched fibers of Obliquus internus and Transversus abdominis; below, by
the union of the transversalis fascia with the inguinal ligament, and at its medial
end by the lacunar ligament.
Extraperitoneal Connective Tissue. — Between the inner surface of the general
layer of the fascia which lines the interior of the abdominal and pelvic cavities,
and the peritoneum, there is a considerable amount of connective tissue, termed
the extraperitoneal or subperitoneal connective tissue.
THE POSTERIOR MUSCLES OF THE ABDOMEN
419
The parietal portion lines the cavity in varying quantities in diflPerent situations.
It IS especially abundant on the posterior wall of the abdomen, and particularly
around the kidneys, where it contains much fat. On the anterior wall of the abdo-
men, except in the pubic region, and on the lateral wall above the iliac crest,
It IS scanty, and here the transversalis fascia is more closely connected with the
peritoneum. There is a considerable amount of extraperitoneal connective tissue
in the pelvis.
The visceral portion follows the course of the branches of the abdominal aorta
betweeri the layers of the mesenteries and other folds of peritoneum which connect
the various viscera to the abdominal wall. The two portions are directly con-
tinuous with each other.
Abdominal inguinal
ring
Inf. epigastric artery
Fig. 401. — The abdominal inguinal ring.
The Deep Crural Arch. — Curving over the external iliac vessels, at the spot where
they become femoral, on the abdominal side of the inguinal ligaments and loosely
connected with it, is a thickened band of fibers called the deep crural arch. It
is apparently a thickening of the transversalis fascia joined laterally to the center
of the lower margin of the inguinal ligament, and arching across the front of
the femoral sheath to be inserted by a broad attachment into the pubic tubercle
and pectineal line, behind the inguinal aponeurotic falx. In some subjects this
structure is not very prominently marked, and not infrequently it is altogether
wanting.
2. The Posterior Muscles of the Abdomen.
Psoas major.
Psoas minor.
Iliacus.
Quadratus lumborum.
The Psoas major, the Psoas minor, and the Iliacus, with the fasciae covering
them, will be described with the muscles of the lower extremity (see page 466).
The Fascia Covering the Quadratus Lumborum.— This is a thin layer attached,
medially, to the bases of the transverse processes of the lumbar vertebrae; below,
420 MYOLOGY
to the iliolumbar ligament; above, to the apex and lower border of the last rib.
The upper margin of this fascia, which extends from the transverse process of the
first lumbar vertebra to the apex and lower border of the last rib, constitutes the
lateral lumbocostal arch (page 405). Laterally, it blends with the lumbodorsal
fascia, the anterior layer of which intervenes between the Quadratus lumborum
and the Sacrospinalis.
The Quadratus lumborum (Fig. 389, page 398) is irregularly quadrilateral in
shape, and broader below than above. It arises by aponeurotic fibers from the
iliolumbar ligament and the adjacent portion of the iliac crest for about 5 cm.,
and is inserted into the lower border of the last rib for about half its length, and
by four small tendons into the apices of the transverse processes of the upper four
lumbar vertebrae. Occasionally a second portion of this muscle is found in front
of the preceding. It arises from the upper borders of the transverse processes of
the lower three or four lumbar vertebrae, and is inserted into the lower margin of
the last rib. In front of the Quadratus lumborum are the colon, the kidney, the
Psoas major and minor, and the diaphragm; between the fascia and the muscle
are the twelfth thoracic, ilioinguinal, and iliohypogastric nerves.
Variations. — The number of attachments to the vertebrae and the extent of its attachment to
the last rib vary.
Nerve Supply. — The twelfth thoracic and first and second lumbar nerves supply this muscle.
Actions. — The Quadratus lumborum draws down the last rib, and acts as a muscle of inspira-
tion by helping to fix the origin of the diaphragm. If the thorax and vertebral column are
fixed, it may act upon the pelvis, raising it toward its own side when only one muscle is put in
action; and when both muscles act together, either from below or above, they flex the trunk.
V. THE MUSCLES AND FASCIA OF THE PELVIS.
Obturator internus. Levator ani.
Piriformis. Coccygeus.
The muscles within the pelvis may be divided into two groups: (1) the Obturator
internus and the Piriformis, which are muscles of the lower extremity, and will be
described with these (pages 476 and 477) ; (2) the Levator ani and the Coccygeus,
which together form the pelvic diaphragm and are associated with the pelvic viscera.
The classification of the two groups under a common heading is convenient in
connection with the fasciae investing the muscles. These fasciae are closely related
to one another and to the deep fascia of the perineum, and in addition have special
connections with the fibrous coverings of the pelvic viscera ; it is customary there-
fore to describe them together under the term pelvic fascia.
Pelvic Fascia. — The fascia of the pelvis may be resolved into: (o) the fascial
sheaths of the Obturator internus, Piriformis, and pelvic diaphragm; (6) the
fascia associated with the pelvic viscera.
The fascia of the Obturator internus covers the pelvic surface of, and is attached
around the margin of the origin of, the muscle. Above, it is loosely connected to
the back part of the arcuate line, and here it is continuous with the iliac fascia.
In front of this, as it follows the line of origin of the Obturator internus, it gradually
separates from the iliac fascia and the continuity between the two is retained only
through the periosteum. It arches beneath the obturator vessels and nerve, com-
pleting the obturator canal, and at the front of the pelvis is attached to the back
of the superior ramus of the pubis. Below, the obturator fascia is attached to the
falciform process of the sacrotuberous ligament and to the pubic arch, where it
becomes continuous with the superior fascia of the urogenital diaphragm. Behind,
it is prolonged into the gluteal region.
The internal pudendal vessels and pudendal nerve cross the pelvic surface of
THE MUSCLES AND FASCIA OF THE PELVIS
421
enclosed in a special canal— Alcock's canal-
the Obturator interniis and are
formed by the obturator fascia.
The fascia of the Piriformis is very thin and is attached to the front of the sacrum
and the sides of the greater sciatic foramen; it is prolonged on the muscle into
the gluteal region. At its sacral attachment around the margins of the anterior
sacral foramina it comes into intimate association with and ensheathes the
nerves emerging from these foramina. Hence the sacral nerves are frequently
described as lying behind the fascia. The internal iliac vessels and their branches,
on the other hand, lie in the subperitoneal tissue in front of the fascia, and the
branches to the gluteal region emerge in special sheaths of this tissue, above and
below the Piriformis muscle.
{Superior
Dmphragmatic layer
part of pelvic i
fascia \ Inferior
y layer
Tendinous arch
Fascia endopelvina
Vesicula seminalis /
Ductus deferens
Rectovesical layer
Fig 402. — Coronal section of pelvis, showing arrangement of fasciae. Viewed from behind. (Diagrammatic.)
The diaphragmatic part of the pelvic fascia (Fig. 402) covers both surfaces of the
Levatores ani. The inferior layer is known as the anal fascia; it is attached above
to the obturator fascia along the line of origin of the Levator ani, while below it
is continuous with the superior fascia of the urogenital diaphragm, and with the
fascia on the Sphincter ani internus. The layer covering the upper surface of the
pelvic diaphragm follows, above, the line of origin of the Levator ani and is there-
fore somewhat variable. In front it is attached to the back of the symphysis
pubis about 2 cm. above its lower border. It can then be traced laterally across
the back of the superior ramus of the pubis for a distance of about 1.25 cm., when
it reaches the obturator fascia. It is attached to this fascia along a line which
pursues a somewhat irregular course to the spine of the ischium. The irregularity
of this line is due to the fact that the origin of the Levator ani, which in lower
forms is from the pelvic brim, is in man lower down, on the obturator fascia.
Tendinous fibers of origin of the muscle are therefore often found extending up
toward, and in some cases reaching, the pelvic brim, and on these the fascia is
carried.
It will be evident that the fascia covering that part of the Obturator internus
which lies above the origin of the Levator ani is a composite fascia and includes
the following: (a) the obturator fascia; (6) the fascia of the Levator ani; (c)
degenerated fibers of origin of the Levator ani.
422
MYOLOGY
The lower margin of the fascia covering the upper surface of the pelvic diaphragm
is attached along the line of insertion of the Levator ani.
At the level of a line extending from the lower part of the symphysis pubis
to the spine of the ischium is a thickened whitish band in this upper layer of the
diaphragmatic part of the pelvic fascia. It is termed the tendinous arch or white
line of the pelvic fascia, and marks the line of attachment of the special fascia
(pars endopelvina fascicB pelvis) which is associated with the pelvic viscera.
Peritoneum
Vesical layer
urogenital^ /„/•.,•»
diaphragm y ^^^^^
Vesicula
~seminalis
Rectovesical layer
Capsule of
prostate
Rectal layer
Transversus 2)erincei superficialig
Colles' fascia
Urogenital diaphragm
Fig. 403. — Median sagittal section of pelvis, showing arrangement of fascise.
The endopelvic part of the pelvic fascia is continued over the various pelvic
viscera (Fig. 403) to form for them fibrous coverings which will be described later
(see section on Splanchnology). It is attached to the diaphragmatic part of the
pelvic fascia along the tendinous arch, and has been subdivided in accordance
with the viscera to which it is related. Thus its anterior part, known as the vesical
layer, forms the anterior and lateral ligaments of the bladder. Its middle part
crosses the floor of the pelvis between the rectum and vesicula^ seminales as the
rectovesical layer; in the female this is perforated by the vagina. Its posterior
portion passes to the side of the rectum; it forms a loose sheath for the rectum,
but is firmly attached around the anal canal ; this portion is known as the rectal
layer.
The Levator ani (Fig. 404) is a broad, thin muscle, situated on the side of the
pelvis. It is attached to the inner surface of the side of the lesser pelvis, and unites
THE MUSCLES AND FASCIA OF THE PELVIS
423
with its fellow of the opposite side to form the greater part of the floor of the pelvic
cavity. It supports the viscera in this cavity, and surrounds the various structures
which pass through it. It arises, in front, from the posterior surface of the superior
ramus of the pubis lateral to the symphysis; behind, from the inner surface of the
spine of the ischium; and between these two points, from the obturator fascia.
Posteriorly, this fascial origin corresponds, more or less closely, with the tendinous
arch of the pelvic fascia, but in front, the muscle arises from^he fascia at a vary-
ing distance above the arch, in some cases reaching nearly as high as the canal
Superior glutceal vessels
Obturator nerve
and vessels
Left lobe of prostate (cut)
Anococcygeal raphe
Fig. 404. — Left Levator ani from within.
for the obturator vessels and nerve. The fibers pass downward and backward
to the middle line of the floor of the pelvis; the most posterior are inserted into the
side of the last two segments of the coccyx; those placed more anteriorly unite
with the muscle of the opposite side, in a median fibrous raphe (anococcygeal
raphe), which extends between the coccyx and the margin of the anus. The middle
fibers are inserted into the side of the rectum, blending with the fibers of the
Sphincter muscles; lastly, the anterior fibers descend upon the side of the prostate
to unite beneath it with the muscle of the opposite side, joining with the fibers of
the Sphincter ani externus and Transversus perinsei, at the central tendinous point
of the perineum.
424 MYOLOGY
The anterior portion is occasionally separated from the rest of the muscle by
connective tissue. From this circumstance, as well as from its peculiar relation
with the prostate, which it supports as in a sling, it has been described as a distinct
muscle, under the name of Levator prostatae. In the female the anterior fibers of
the Levator ani descend upon the side of the vagina.
The Levator ani may be divided into iliococcygeal and pubococcj'geal parts.
The Iliococcygeus arises from the ischial spine and from the posterior part of the tendinous
arch of the pelvic fascia, and is attached to the coccyx and anococcj-geal raph^; it is usually thin,
and may fail entirely, or be largely replaced by fibrous tissue. An accessor}- slip at its posterior
part is sometimes named the Iliosacralis. The Pubococcygeus arises from the back of the pubis
and from the anterior part of the obturator fascia, and "is directed backward almost horizontally
along the side of the anal canal toward the coccyx and sacrum, to which it finds attachment.
Between the termination of the vertebral column and the anus, the two Pubococcj'gei muscles
come together and form a thick, fibromuscular layer lj"ing.on the raphe formed by the Ihococcj-gei"
(Peter Thompson). The greater part of this muscle is inserted into the coccj'x and into the last
one or two pieces of the sacrmn. This insertion into the vertebral column is, however, not
admitted by all observers. The fibers which form a shng for the rectum are named the Pubo-
rectalis or Sphincter recti. They arise from the lower part of the sjTnphysis pubis, and from the
superior fascia of the urogenital diaphragm. They meet with the corresponding fibers of the
opposite side around the lower part of the rectum, and form for it a strong sUng.
Nerve Supply. — The Levator ani is supplied b\- a branch from the fourth sacral nerve and
by a branch which is sometimes derived from the perineal, sometimes from the inferior hemor-
rhoidal division of the pudendal nerve.
The Coccygeus (Fig. 404) is situated behind the preceding. It is a triangular
plane of muscular and tendinous fibers, arising by its apex from the spine of the
ischium and sacrospinous ligament, and inserted by its base into the margin of the
coccyx and into the side of the lowest piece of the sacrum. It assists the Levator
ani and Piriformis in closing in the back part of the outlet of the pelvis.
Nerve Supply. — The Coccygeus is supplied by a branch from the fourth and fifth sacral ner\'es.
Actions. — The Levatores ani constrict the lower end of the rectum and vagina. They elevate
and invert the lower end of the rectum after it has been protruded and everted during the expul-
sion of the feces. They are also muscles of forced expiration. The Coccygei pull forward and
support the coccyx, after it has been pressed backward during defecation or parturition. The
Levatores ani and Coccygei together form a muscular diaphragm which supports the pelvic
viscera.
VI. THE MUSCLES AND FASCLS: OF THE PERINEUM.
The perineum corresponds to the outlet of the pelvis. Its deep boundaries
are — m front, the pubic arch and the arcuate ligament of the pubis; behind, the tip
of the cocc^'x; and on either side the inferior rami of the pubis and ischium, and the
sacrotuberous ligament. The space is somewhat lozenge-shaped and is limited
on the surface of the body by the scrotum in front, by the buttocks behind, and
laterally by the medial side of the thigh. A line drawn transversely across in
front of the ischial tuberosities divides the space into two portions. The pos-
terior contains the termination of the anal canal and is known as the anal region;
the anterior, which contains the external urogenital organs, is termed the urogenital
region.
The muscles of the perineum may therefore be divided into two groups:
1. Those of the anal region.
2. Those of the urogenital region: a, In the male; b, In the female.
1. The Muscles of the Anal Region.
Corrugator cutis ani. Sphincter ani externus. Sphincter ani internus.
The Superficial Fascia. — The superficial fascia is very thick, areolar in texture,
and contains much fat in its meshes. On either side a pad of fatty tissue extends
THE MUSCLES OF THE ANAL REGION
425
deeply between the Levator ani and Obturator internus into a space known as the
ischiorectal fossa.
The Deep Fascia.— The deep fascia forms the lining of the ischiorectal fossa;
It comprises the anal fascia, and the portion of obturator fascia below the origin
of Levator ani.
Ischiorectal Fossa (fossa ischioredalis) (Fig. 405).— The fossa is somewhat pris-
matic in shape, with its base directed to the surface of the perineum, and its apex
at the line of meeting of the obturator and anal fasciae. It is bounded medially
by the Sphincter ani externus and the anal fascia; laterally, bv the tuberosity of
the ischium and the obturator fascia; anteriorly, by the fascia of Colles covering
the Transversus perina:'i superficialis, and by the inferior fascia of the urogenital
diaphragm; posteriorly, by the Gluta-us maximus and the sacrotuberous ligament.
Crossing the space transversely are the inferior hemorrhoidal vessels and nerves;
Fig. 405. — The perineum. The integument and superficial layer of superficial fascia reflected.
at the back part are the perineal and perforating cutaneous branches of the
pudendal plexus; while from the forepart the posterior scrotal (or labial) vessels
and nerves emerge. The internal pudendal vessels and pudendal nerve lie in
Alcock's canal on the lateral wall. The fossa is filled with fatty tissue across
which numerous fibrous bands extend from side to side.
The Corrugator Cutis Am, — Around the anus is a thin stratum of involuntary
muscular fiber, which radiates from the orifice. Medially the fibers fade off into
the submucous tissue, while laterally they blend with the true skin. By its contrac-
tion it raises the skin into ridges around the margin of the anus.
The Sphincter ani externus (External sphincter ani) (Fig 405) is a flat plane
of muscular fibers, elliptical in shape and intimately adherent to the integument
surrounding the margin of the anus. It measures about 8 to 10 cm. in length, from
its anterior to its posterior extremity, and is about 2.5 cm. broad opposite the
anus. It consists of two strata, superficial and deep. The superficial, constituting
426 MYOLOGY
the main portion of the muscle, arises from a narrow tendinous band, the anococcy-
geal raphe, which stretches from the tip of the coccyx to the posterior margin of
the anus; it forms two flattened planes of muscular tissue, which encircle the anus
and meet in front to be inserted into the central tendinous point of the perineum,
joining with the Transversus perina?i superficialis, the Levator ani, and the Bul-
bocavernosus. The deeper portion forms a complete sphincter to the anal canal.
Its fibers surround the canal, closely applied to the Sphincter ani interniis, and in
front blend with the other muscles at the central point of the perineum. In a
considerable proportion of cases the fibers decussate in front of the anus, and are
continuous with the Transversi perina^i superficiales. Posteriorly, they are not
attached to the cocc\'x, but are continuous with those of the opposite side behind
the anal canal. The upper edge of the muscle is ill-defined, since fibers are given
off from it to join the Levator ani.
Nerve Supply. — A branch from the fourth sacral and twigs from the inferior hemorrhoidal
branch of the pudendal supply the muscle.
Actions. — The action of this muscle is pecuhar. (1) It is, like other muscles, always in a state
of tonic contraction, and having no antagonistic muscle it keeps the anal canal and orifice closed.
(2) It can be put into a condition of greater contraction under the influence of the will, so as
ipore firmly to occlude the anal aperture, in expiratory efforts unconnected with defecation.
(3) Taking its fixed point at the coccyx, it helps to fi.x the central point of the perineum, so that
the Bulbocavernosus may act from this fixed point.
The Sphincter ani intemus (Internal sphincter ani) is a muscular ring which
surrounds about 2.5 cm. of the anal canal; its inferior border is in contact with,
but quite separate from, the Sphincter ani externus. It is about 5 mm. thick, and
is formed by an aggregation of the involuntary circular fibers of the intestine.
Its lower border is about 6 mm. from the orifice of the anus.
Actions. — Its action is entirely involuntarj-. It helps the Sphincter ani externus to occlude
the anal aperture and aids in the expulsion of the feces.
2. A. The Muscles of the Urogenital Region in the Male (Fig. 406).
Transversus perin?ei superficialis. Ischiocavernosus.
Bulbocavernosus. Transversus periniei profundus.
Sphincter urethrse membranaceae.
Superficial Fascia. — The superficial fascia of this region consists of two layers,
superficial and deep.
The superficial layer is thick, loose, areolar in texture, and contains in its meshes
much adipose tissue, the amount of which varies in different subjects. In front,
it is continuous with the dartos tunic of the scrotum; behind, with the subcuta-
neous areolar tissue surrounding the anus; and, on either side, with the same fascia
on the inner sides of the thighs. In the middle line, it is adherent to the skin on
the raphe and to the deep layer of the superficial fascia.
The deep layer of superficial fascia (fascia of Colles) (Fig. 405) is thin, aponeurotic
in structure, and of considerable strength, serving to bind down the muscles of
the root of the penis. It is continuous, in front, with the dartos tunic, the deep
fascia of the penis, the fascia of the spermatic cord, and Scarpa's fascia upon the
anterior wall of the abdomen; on either side it is firmly attached to the margins
of the rami of the pubis and ischium, lateral to the crus penis and as far back as
the tuberosity of the ischium ; posteriorly, it curves around the Transversi perina?i
superficiales to join the lower margin of the inferior fascia of the urogenital dia-
phragm. In the middle line, it is connected with the superficial fascia and with the
median septum of the Bulbocavernosus. This fascia not only covers the muscles
in this region, but at its back part sends upward a vertical septum from its deep
surface, which separates the posterior portion of the subjacent space into two.
i
THE MUSCLES OF THE UROGENITAL REGION IN THE MALE 427
The Central Tendinous Point of the Perineum.— This is a fibrous point in the middle
hne of the perineum, between the urethra and anus, and about 1.25 cm. in front
of the latter. At this point six muscles converge and are attached: viz., the
Sphincter ani externus, the Bulbocavernosus, the two Transversi perina?i super-
ficiales, and the anterior fibers of the Levatores ani.
Fig. 406. — Muscles of male perineum.
The Transversus perinaei superficialis ( Transversus perincei; Superficial transterse
perineal muscle) is a narrow muscular slip, which passes more or less transversely
across the perineal space in front of the anus. It arises by tendinous fibers from
the inner and forepart of the tuberosity of the ischium, and, running medialward,
is inserted into the central tendinous point of the perineum, joining in this situa-
tion with the muscle of the opposite side, with the Sphincter ani externus behind,
and with the Bulbocavernosus in front. In some cases, the fibers of the deeper
layer of the Sphincter ani externus decussate in front of the anus and are con-
tinued into this muscle. Occasionally it gives oft' fibers, which join with the
Bulbocavernosus of the same side.
Variations are numerous. It may be absent or double, or insert into Bulbocavernosus or
External sphincter.
428 MYOLOGY
Actions. — The simultaneous contraction of the two muscles serves to fix the central tendinous
point of the perineum.
The Bulbocavernosus (Ejacidator urinoe; Accelerator urince) is placed in the
middle line of the perineum, in front of the anus. It consists of two symmetrical
parts, united along the median line by a tendinous raphe. It arises from the cen-
tral tendinous point of the perineum and from the median raphe in front. Its
fibers diverge like the barbs of a quill-pen; the most posterior form a thin layer,
which is lost on the inferior fascia of the urogenital diaphragm; the middle fibers
encircle the bulb and adjacent parts, of the corpus cavernosum urethrae, and join
with the fibers of the opposite side, on the upper part of the corpus cavernosum
urethrie, in a strong aponeurosis; the anterior fibers, spread out over the side
of the corpus cavernosum penis, to be inserted partly into that body, anterior to
the Ischiocavernosus, occasionally extending to the pubis, and partly ending in a
tendinous expansion which covers the dorsal vessels of the penis. The latter
fibers are best seen by dividing the muscle longitudinally, and reflecting it from
the surface of the corpus cavernosum urethrse.
Actions. — This muscle serves to empty the canal of the urethra, after the bladder has expelled
its contents; during the greater part of the act of micturition its fibers are relaxed, and it only
comes into action at the end of the process. The middle fibers are supposed by Krause to assist
in the erection of the corpus cavernosum urethra-, by compressing the erectile tissue of the bulb.
The anterior fibers, according to Tyrrel, also contribute to the erection of the penis by compressing
the deep dorsal vein of the penis as they are inserted into, and continuous with, the fascia of the
penis.
The Ischiocavernosus (Erector penis) covers the crus penis. It is an elongated
muscle, broader in the middle than at either end, and situated on the lateral bound-
ary of the perineum. It arises by tendinous and fleshy fibers from the inner sur-
face of the tuberosity of the ischium, behind the crus penis; and from the rami of
the pubis and ischium on either side of the crus. From these points fleshy fibers
succeed, and end in an aponeurosis which is inserted into the sides and imder
surface of the crus penis.
Action. — The Ischiocavernosus compresses the crus penis, and retards the return of the blood
through the veins, and thus serves to maintain the organ erect.
Between the muscles just examined a triangular space exists, bounded medially by the Bulbo-
cavernosus, laterally by the Ischiocavernosus, and behind by the Transversus perinaei super-
ficialis; the floor is formed by the inferior fascia of the urogenital diaphragm. Running from
behind forward in the space are the posterior scrotal vessels and nerves, and the perineal branch
of the posterior femoral cutaneous nerve; the transverse perineal artery courses along its posterior
boundary on the Transversus perina-i superficialis.
The Deep Fascia.- — The deep fascia of the urogenital region forms an investment
for the Transversus perinaei profundus and the Sphincter urethra? membranacea^,
but within it lie also the deep vessels and nerves of this part, the whole forming a
transverse septum which is known as the urogenital diaphragm. From its shape
it is usually termed the triangular ligament, and is stretched almost horizontally
across the pubic arch, so as to close in the front part of the outlet of the pelvis.
It consists of two dense membranous laminfe (Fig. 407), which are united along
their posterior borders, but are separated in front by intervening structures. The
superficial of these two layers, the inferior fascia of the urogenital diaphragm, is tri-
angular in shape, and about 4 cm. in depth. Its apex is directed forward, and is
separated from the arcuate pubic ligament by an oval opening for the transmission
of the deep dorsal vein of the penis. Its lateral margins are attached on either side
to the inferior rami of the pubis and ischium, above the crus penis. Its base is
directed toward the rectum, and connected to the central tendinous point of the
perineum. It is continuous with the deep layer of the superficial fascia behind the
Transversus perinaei superficialis, and with the inferior layer of the diaphragmatic
THE MUSCLES OF THE UROGENITAL REGION IN THE MALE 429
part of the pelvic fascia. It is perforated, about 2.5 cm. below the symphysis
pubis, by the urethra, the aperture for which is circular and about 6 mm. in diameter
by the arteries to the bulb and the ducts of the bulbourethral glands close to the
urethral orifice; by the deep arteries of the penis, one on either side close to the
pubic arch and about halfway along the attached margin of the fascia; bv the dorsal
arteries and nerves of the penis near the apex of the fascia. Its base is also perfor-
ated by the perineal vessels and nerves, while between its apex and the arcuate
pubic ligament the deep dorsal vein of the penis passes upward into the pelvis.
If the inferior fascia of the urogenital diaphragm be detached on either side,
the follo\ying structures will be seen between it and the superior fascia: the deep
dorsal vein of the penis; the membranous portion of the urethra; the Transversus
penn-^i profundus and Sphincter urethra membranaceai muscles; the bulbo-
urethral glands and their ducts; the pudendal vessels and dorsal nerves of the penis;
the arteries and nerves of the urethral bulb, and a plexus of veins.
Fascia of i^y'''^'
urogenital} J^V''
I schiocavernosus
diaphragm
Inferior
layer
Bulbocavernosus
Fig 407. — Coronal section of anterior part of pelvis, through the pubic arch. Seen from in front. (Diagrammatic.)
The superior fascia of the urogenital diaphragm is continuous with the obturator
fascia and stretches across the pubic arch. If the obturator fascia be traced medially
after leaving the Obturator internus muscle, it will be found attached by some of
its deeper or anterior fibers to the inner margin of the pubic arch, while its super-
ficial or posterior fibers pass over this attachment to become continuous with the
superior fascia of the urogenital diaphragm. Behind, this layer of the fascia is
continuous with the inferior fascia and with the fascia of Colles; in front it is con-
tinuous with the fascial sheath of the prostate, and is fused with the inferior fascia
to form the transverse ligament of the pelvis.
The Transversus perinaei profundus arises from the inferior rami of the ischium
and runs to the median line, where it interlaces in a tendinous raphe with its fellow
of the opposite side. It lies in the same plane as the Sphincter urethrje membran-
aceae; formerly the two muscles were described together as the Constrictor urethrae.
The Sphincter urethrae membranacese surrounds the whole length of the mem-
branous portion of the urethra, and is enclosed in the fasciae of the urogenital dia-
phragm. Its external fibers arise from the junction of the inferior rami of the pubis
430 MYOLOGY
and ischium to the extent of 1.25 to 2 cm., and from the neighboring fasciae.
They arch across the front of the urethra and bulbourethral glands, pass around
the urethra, and behind it unite with the muscle of the opposite side, by means
of a tendinous raphe. Its innermost fibers form a continuous circular investment
for the membranous urethra.
Nerve Supply. — The perineal branch of the pudendal nerve supplies this group of muscles.
Actions. — The muscles of both sides act together as a sphincter, compressing the membranous
portion of the urethra. During the transmission of fluids they, hke the Bulbocavernosus, are
relaxed, and only come into action at the end of the process to eject the last drops of the fluid.
2. B. The Muscles of the Urogenital Region in the Female (Fig. 408).
Transversus perinsei superficialis. Ischiocavernosus.
Bulbocavernosus. Transversus perinjei profundus.
Sphincter urethrae membranacea?.
The Transversus perinaei superficialis {Transversus perincpi; Superficial trans-
verse perineal muscle) in the female is a narrow muscular slip, which arises by a
small tendon from the inner and forepart of the tuberosity of the ischium, and
is inserted into the central tendinous point of the perineum, joining in this situa-
tion with the muscle of the opposite side, the Sphincter ani externus behind, and
the Bulbocavernosus in front.
Action. — The simultaneous contraction of the two muscles serves to fix the central tendinous
point of the perineum.
The Bulbocavernosus {Sphincter vagina) surrounds the orifice of the vagina.
It covers the lateral parts of the vestibular bulbs, and is attached posteriorly
to the central tendinous point of the perineum, where it blends with the Sphincter
ani externus. Its fibers pass forward on either side of the vagina to be inserted
into the corpora cavernosa clitoridis, a fasciculus crossing over the body of the
organ so as to compress the deep dorsal vein.
Actions. — The Bulbocavernosus diminishes the orifice of the vagina. The anterior fibers
contribute to the erection of the clitoris, as they are inserted into and are continuous with the
fascia of the clitoris, compressing the deep dorsal vein during the contraction of the muscle.
The Ischiocavernosus {Erector clitoridis) is smaller than the corresponding
muscle in the male. It covers the unattached surface of the crus clitoridis. It is
an elongated muscle, broader at the middle than at either end, and situated on
the side of the lateral boundary of the perineum. It arises by tendinous and fleshy
fibers from the inner surface of the tuberosity of the ischium, behind the crus
clitoridis; from the surface of the crus; and from the adjacent portion of the ramus
of the ischium. From these points fleshy fibers succeed, and end in an aponeurosis,,
which is inserted into the sides and under surface of the crus clitoridis.
Actions. — The Ischiocavernosus compresses the crus clitoridis and retards the return of blood
through the veins, and thus serves to maintain the organ erect.
The fascia of the urogenital diaphragm in the female is not so strong as in the
male. It is attached to the pubic arch, its apex being connected with the arcuate
pubic ligament. It is divided in the middle line by the aperture of the vagina,
with the external coat of which it becomes blended, and in front of this is perfor-
ated by the urethra. Its posterior border is continuous, as in the male, with the
deep layer of the superficial fascia around the Transversus perintiei superficialis.
Like the corresponding fascia in the male, it consists of two layers, between
which are to be found the following structures: the deep dorsal vein of the clitoris,
a portion of the urethra and the Constrictor urethra muscle, the larger vestibular
THE MUSCLES AND FASCIA OF THE UPPER EXTREMITY 431
glands and their ducts; the internal pudendal vessels and the dorsal nerves of the
clitoris; the arteries and nerves of the bulbi vestibuli, and a plexus of veins.
The Transversus perinaei profundus arises from the inferior rami of the ischium
and runs across to the side of the vagina. The Sphincter urethra^ membranacea?
(Constrictor urethra), like the corresponding muscle on the male, consists of external
Clitoris
Urethra
Vagina
Sphincter ani externus
Fig. 408. — Muscles of the female perineum. (Modified from a drawing by Peter Thompson.)
and internal fibers. The external fibers arise on either side from the margin of the
inferior ramus of the pubis. They are directed across the pubic arch in front of
the urethra, and pass around it to blend with the muscular fibers of the opposite
side, between the urethra and vagina. The innermost fibers encircle the lower end
of the urethra.
Nerve Supply. — The muscles of this group are supplied by the perineal branch of the pudendal.
THE MUSCLES AND FASCI-ffi OF THE UPPER EXTREMITY.
The muscles of the upper extremity are divisible into groups, corresponding
with the different regions of the limb.
I. Muscles Connecting the Upper Extremity to the Vertebral Column.
II. Muscles Connecting the Upper Extremity to the Anterior and Lateral
Thoracic Walls.
III. IMuscles of the Shoulder. V. Muscles of the Forearm.
IV. IMuscles of the Arm. VI. Muscles of the Hand.
432 MYOLOGY
I. THE MUSCLES CONNECTING THE UPPER EXTREMITY TO THE
VERTEBRAL COLUMN.
The muscles of this group are :
Trapezius. Rhomboideus major.
Latissimus dorsi. Rhomboideus minor.
Levator scapulse.
Superficial Fascia. — The superficial fascia of the back forms a layer of con-
siderable thickness and strength, and contains a quantity of granular fat. It is
continuous with the general superficial fascia.
Deep Fascia. — The deep fascia is a dense fibrous layer, attached above to the
superior nuchal line of the occipital bone; in the middle line it is attached to the
ligamentum nuchse and supraspinal ligament, and to the spinous processes of all
the vertebrae below the seventh cervical; laterally, in the neck it is continuous with
the deep cervical fascia; over the shoulder it is attached to the spine of the scapula
and to the acromion, and is continued downward over the Deltoideus to the arm;
on the thorax it is continuous with the deep fascia of the axilla and chest, and on
the abdomen with that covering the abdominal muscles; below, it is attached to
the crest of the ilium
The Trapezius (Fig. 409) is a flat, triangular muscle, covering the upper and
back part of the neck and shoulders. It arises from the external occipital protu-
berance and the medial third of the superior nuchal line of the occipital bone, from
the ligamentum nuchje, the spinous process of the seventh cervical, and the spinous
processes of all the thoracic vertebrae, and from the corresponding portion of the
supraspinal ligament. From this origin, the superior fibers proceed downward
and lateralward, the inferior upward and lateralward, and the middle horizontally;
the superior fibers are inserted into the posterior border of the lateral third of the
clavicle ; the middle fibers into the medial margin of the acromion, and into the supe-
rior lip of the posterior border of the spine of the scapula; the inferior fibers con-
verge near the scapula, and end in an aponeurosis, which glides over the smooth
triangular surface on the medial end of the spine, to be inserted into a tubercle
at the apex of this smooth triangular surface. At its occipital origin, the Trapezius
is connected to the bone by a thin fibrous lamina, firmly adherent to the skin.
At the middle it is connected to the spinous processes by a broad semi-elliptical
aponeurosis, which reaches from the sixth cervical to the third thoracic vertebrae,
and forms, with that of the opposite muscle, a tendinous ellipse. The rest of the
muscle arises by numerous short tendinous fibers. The two Trapezius muscles
together resemble a trapezium, or diamond-shaped quadrangle: two angles corre-
sponding to the shoulders; a third to the occipital protuberance; and the fourth
to the spinous process of the twelfth thoracic vertebra.
Variations. — The attachments to the dorsal vertebrae are often reduced and the lower ones are
often wanting; the occipital attachment is often wanting; separation between cervical and dorsal
portions is frequent. Extensive deficiencies and complete absence occur.
The clavicular insertion of this muscle varies in extent; it sometimes reaches
as far as the middle of the clavicle, and occasionally may blend with the posterior
edge of the Sternocleidomastoideus, or overlap it.
The Latissimus dorsi (Fig. 409) is a triangular, flat muscle, which covers the
lumbar region and the lower half of the thoracic region, and is gradually con-
tracted into a narrow fasciculus at its insertion into the humerus. It arises by
tendinous fibers from the spinous processes of the lower six thoracic vertebrae
and from the posterior layer of the lumbodorsal fascia (see page 397), by which
it is attached to the spines of the lumbar and sacral vertebrae, to the supraspinal
ligament, and to the posterior part of the crest of the ilium. It also arises by
MUSCLES OF THE UPPER EXTREMITY
433
Lumbar triangle
FiQ 409. — Muscles connecting the upper extremity to the vertebral column.
28
434 MYOLOGY
muscular fibers from the external lip of the crest of the ilium lateral to the margin
of the Sacrospinalis, and from the three or four lower ribs by fleshy digitations,
which are interposed between similar processes of the Obliquus abdominis externus
(Fig. 392, page 409). From this extensive origin the fibers pass in different direc-
tions, the upper ones horizontally, the middle obliquely upward, and the lower
vertically upward, so as to converge and form a thick fasciculus, which crosses the
inferior angle of the scapula, and usually receives a few fibers from it. The muscle
curves around the lower border of the Teres major, and is twisted upon itself, so
that the superior fibers become at first posterior and then inferior, and the vertical
fibers at first anterior and then superior. It ends in a quadrilateral tendon, about
7 cm. long, which passes in front of the tendon of the Teres major, and is inserted
into the bottom of the intertubercular groove of the humerus ; its insertion extends
higher on the humerus than that of the tendon of the Pectoralis major. The lower
border of its tendon is united with that of the Teres major, the surfaces of the two
being separated near their insertions by a bursa; another bursa is sometimes inter-
posed between the muscle and the inferior angle of the scapula. The tendon of
the muscle gives off an expansion to the deep fascia of the arm.
Variations. — The number of dorsal vertebrae to which it is attached vary from four to seven or
eight; the number of costal attachments varies; muscle fibers may or may not reach the crest of
the ilium.
A muscular slip, the axillary arch, varying from 7 to 10 cm. in length, and from 5 to 15 mm.
in breadth, occasionally springs from the upper edge of the Latissimus dorsi about the middle
of the posterior fold of the axilla, and crosses the axilla in front of the axillary vessels and nerves,
to join the under surface of the tendon of the Pectoralis major, the Coracobrachiahs, or the fascia
over the Biceps brachii. This axillary arch crosses the axillary artery, just above the spot usually
selected for the apphcation of a ligature, and may mislead the surgeon during the operation. It
is present in about 7 per cent, of subjects and may be easily recognized by the transverse direction
of its fibers.
A fibrous slip usually passes from the lower border of the tendon of the Latissimus dorsi, near
its insertion, to the long head of the Triceps brachii. This is occasionally muscular, and is the
representative of the Dorsoepitrochlearis brachii of apes.
The lateral margin of the Latissimus dorsi is separated below from the Obliquus
externus abdominis by a small triangular interval, the lumbar triangle of Petit,
the base of which is formed by the iliac crest, and its floor by the Obliquus internus
abdominis. Another triangle is situated behind the scapula. It is bounded above
by the Trapezius, below by the Latissimus dorsi, and laterally by the vertebral
border of the scapula; the floor is partly formed by the Rhomboideus major.
If the scapula be drawn forward by folding the arms across the chest, and the
trunk bent forward, parts of the sixth and seventh ribs and the interspace between
them become subcutaneous and available for auscultation. The space is there-
fore known as the triangle of auscultation.
Nerves. — The Trapezius is supplied by the accessory nerve, and by branches from the third
and fourth cervical nerves; the Latissimus dorsi by the sixth, seventh, and eighth cervical nerves
through the thoracodorsal (long subscapular) nerve.
The Rhomboideus major (Fig. 409) arises by tendinous fibers from the spinous
processes of the second, third, fourth, and fifth thoracic vertebrae and the supra-
spinal ligament, and is inserted into a narrow tendinous arch, attached above to
the lower part of the triangular surface at the root of the spine of the scapula;
below to the inferior angle, the arch being connected to the vertebral border by a
thin membrane. When the arch extends, as it occasionally does, only a short
distance, the muscular fibers are inserted directly into the scapula.
The Rhomboideus minor (Fig. 409) arises from the lower part of the ligamentum
nuchtie and from the spinous processes of the seventh cervical and first thoracic
vertebrae. It is inserted into the base of the triangular smooth surface at the root
of the spine of the scapula, and is usually separated from the Rhomboideus major
MUSCLES OF THE UPPER EXTREMITY 435
by a slight interval, but the adjacent margins of the two muscles are occasionally
united.
Variations.— The vertebral and scapular attachments of the two muscles vary in extent. A
small slip from the scayoula to the occipital bone close to the minor occasionally occurs, the Rhom-
boideus occipitalis muscle.
The Levator scapulae. {Levator angv.li scapula') (Fig. 409) is situated at the
back and side of the neck. It arises by tendinous slips from the transverse pro-
cesses of the atlas and axis and from the posterior tubercles of the transverse
processes of the third and fourth cervical vertebrae. It is inserted into the verte-
bral border of the scapula, between the medial angle and the triangular smooth
surface at the root of the spine.
Variations. — The number of vertebral attachments varies; a slip may extend to the occipital or
mastoid, to the Trapezius, Scalene or Serratus anterior, or to the first or second rib. The muscle
may be subdivided into several distinct parts from origin to insertion. Levator claviculan from the
transverse processes of one or two upper cervical vertebra; to the outer end of the clavicle corre-
sponds to a muscle of lower animals. More or less union with the Serratus anterior.
Nerves. — The Rhomboidei are supplied by the dorsal scapular nerve from the fifth cervical;
the Levator scapuke by the third and fourth cervical nerves, and frequently by a branch from
the dorsal scapular.
Actions. — The movements effected by the preceding muscles are numerous, as may be con-
ceived from their extensive attachments. When the whole Trapezius is in action it retracts the
scapula and braces back the shoulder; if the head be fixed, the upper part of the muscle will elevate
the point of the shoulder, as in supporting weights; when the lower fibers contract they assist
in depressing the scapula. The middle and lower fibers of the muscle rotate the scapula, causing
elevation of the acromion. If the shoulders be fixed, the Trapezii, acting together, will draw
the head directly backward; or if only one act, the head is drawn to the corresponding side.
When the Latissimus dorsi acts upon the humerus, it depresses and draws it backward, and
at the same time rotates it inward. It is the muscle which is principally employed in giving a
downward blow, as in felling a tree or in sabre practice. If the arm be fixed, the muscle may
act in various ways upon the trunk; thus, it may raise the lower ribs and assist in forcible inspira-
tion; or, if both arms be fixed, the two muscles may assist the abdominal muscles and Pectorales
in suspending and drawing the trunk forward, as in climbing.
If the head be fixed, the Levator scapula; raises the medial angle of the scapula; if the shoulder
be fixed, the muscle inclines the neck to the corresponding side and rotates it in the same direc-
tion. The Rhomboidei carry the inferior angle backward and upward, thus producing a slight
rotation of the scapula upon the side of the chest, the Rhomboideus major acting especially on
the inferior angle of the scapula, through the tendinous arch by which it is inserted. The Rhom-
boidei, acting together with the middle and inferior fibers of the Trapezius, will retract the
scapula.
n. THE MUSCLES CONNECTING THE UPPER EXTREMITY TO THE
ANTERIOR AND LATERAL THORACIC WALLS.
The muscles of the anterior and lateral thoracic regions are:
Pectoralis major. Subclavius.
Pectoralis minor. Serratus anterior.
Superficial Fascia.— The superficial fascia of the anterior thoracic region is con-
tinuous with that of the neck and upper extremity above, and of the abdomen
below. It encloses the mamma and gives off numerous septa which pass into the
gland, supporting its various lobes. From the fascia over the front of the mamma,
fibrous processes pass forward to the integument and papilla; these were called
by Sir A. Cooper the ligamenta suspensoria.
Pectoral Fascia.— The pectoral fascia is a thin lamina, covering the surface of
the Pectoralis major, and sending numerous prolongations between its fasciculi:
it is attached, in the middle line, to the front of the sternum ; above, to the clavicle;
laterally and below it is continuous with the fascia of the shoulder, axilla, and
thorax. It is very thin over the upper part of the Pectoralis major, but thicker
436
MYOLOGY
in the interval between it and the Latissimus dorsi, where it closes in the axillary-
space and forms the axillary fascia; it divides at the lateral margin of the Latis-
simus dorsi into two layers, one of which passes in front of, and the other behind
it; these proceed as far as the spinous processes of the thoracic vertebrse, to which
they are attached. As the fascia leaves the lower edge of the Pectoralis major to cross
the floor of the axilla it sends a layer upward under cover of the muscle; this lamina
splits to envelop the Pectoralis minor, at the upper edge of which it is continuous
with the coracoclavicular fascia. The hollow of the armpit, seen when the arm
is abducted, is produced mainly by the traction of this fascia on the axillary floor,
and hence the lamina is sometimes named the suspensory ligament of the axilla.
At the lower part of the thoracic region the deep fascia is well-developed, and is
continuous with the fibrous sheaths of the Recti abdominis.
Fia. 410. — Superficial muscles of the chest and front ot the arm.
The Pectoralis major (Fig. 410) is a thick, fan-shaped muscle, situated at the
upper and forepart of the chest. It arises from the anterior surface of the sternal
half of the clavicle; from half the breadth of the anterior surface of the sternum,
as low down as the attachment of the cartilage of the sixth or seventh rib; from the
MUSCLES OF THE UPPER EXTREMITY 437
cartilages of all the true ribs, with the exception, frequently, of the first or seventh,
or both, and from the aponeurosis of the Obliquus externus abdominis. From this
extensive origin the fibers converge toward their insertion; those arising from the
clavicle pass obliquely downward and lateralward, and are usually separated from
the rest by a slight interval; those from the lower part of the sternum, and the
cartilages of the lower true ribs, run upward and lateralward; while the middle
fibers pass horizontally. They all end in a flat tendon, about 5 cm. broad, which
is inserted into the crest of the greater tubercle of the humerus. This tendon con-
sists of two laminae, placed one in front of the other, and usually blended together
below. The anterior lamina, the thicker, receives the clavicular and the uppermost
sternal fibers; they are inserted in the same order as that in which they arise:
that is to say, the most lateral of the clavicular fibers are inserted at the upper
part of the anterior lamina; the uppermost sternal fibers pass down to the lower
part of the lamina which extends as low as the tendon of the Deltoideus and joins
with it. The posterior lamina of the tendon receives the attachment of the greater
part of the sternal portion and the deep fibers, i. e., those from the costal cartilages.
These deep fibers, and particularly those from the lower costal cartilages, ascend
the higher, turning backward successively behind the superficial and upper ones,
so that the tendon appears to be twisted. The posterior lamina reaches higher
on the humerus than the anterior one, and from it an expansion is given off which
covers the intertubercular groove and blends with the capsule of the shoulder-
joint. From the deepest fibers of this lamina at its insertion an expansion is given
off which lines the intertubercular groove, while from the lower border of the tendon
a third expansion passes downward to the fascia of the arm.
Variations. — The more frequent variations are greater or less extent of attachment to the ribs
and sternum, varying size of the abdominal part or its absence, greater or less extent of separation
of sternocostal and cla\'icular parts, fusion of cla\'icular part wnth deltoid, decussation in front of
the sternum. Deficiency or absence of the sternocostal part is not uncommon. Absence of the
clavicular part is less frequent. Rarely the whole muscle is wanting.
Costocoracoideus is a muscular band occasionally found arising from the ribs or aponeurosis of the
External oblique between the Pectoralis major and Latissimus dorsi and inserted into the coracoid
process.
Chondro-epitrochlearis is a muscular slip occasionally found arising from the costal cartilages or
from the aponeurosis of the External oblique below the Pectoralis major or from the Pectoralis
major itself. The insertion is variable on the inner side of the arm to fascia, intermuscular septum
or internal condyle.
Siernalis, in front of the sternal end of the Pectoralis major parallel to the margin of the sternum.
It is supplied by the anterior thoracic nerves and is probably a misplaced part of the pectoralis.
Coracoclavicular Fascia {fascia coracoclavicularis; costocoracoid membrane; clavi-
pectoral fascia). — The coracoclavicular fascia is a strong fascia situated under
cover of the clavicular portion of the Pectoralis major. It occupies the interval
between the Pectoralis minor and Subclavius, and protects the axillary vessels
and nerves. Traced upward, it splits to enclose the Subclavius, and its two layers
are attached to the clavicle, one in front of and the other behind the muscle; the
latter layer fuses with the deep cervical fascia and with the sheath of the axillary
vessels. Medially, it blends with the fascia covering the first two intercostal
spaces, and is attached also to the first rib medial to the origin of the Subclavius.
Laterally, it is very thick and dense, and is attached to the coracoid process.
The portion extending from the first rib to the coracoid process is often whiter and
denser than the rest, and is sometimes called the costocoracoid ligament. Below
this it is thin, and at the upper border of the Pectoralis minor it splits into two
layers to invest the muscle; from the lower border of the Pectoralis minor it is
continued downward to join the axillary fascia, and lateralward to join the fascia
over the short head of the Biceps brachii. The coracoclavicular fascia is pierced
by the cephalic vein, thoracoacromial artery and vein, and external anterior
thoracic nerve.
438
MYOLOGY
The Pectoralis minor (Fig. 411) is a thin, triangular muscle, situated at the
upper part of the thorax, beneath the Pectoralis major. It arises from the upper
margins and outer surfaces of the third, fourth, and fifth ribs, near their cartilage
and from the aponeuroses covering the Intercostalis; the fibers pass upward and
lateralward and converge to form a flat tendon, which is inserted into the medial
border and upper surface of the coracoid process of the scapula.
Variations. — Origin from second, third and fourth or fifth ribs. The tendon of insertion may
extend over the coracoid process to the greater tubercle. May be split into several parts. Absence
rare.
Pectoralis minimus, first rib-cartilage to coracoid process. Rare.
Hadius
Fig. 411. — Deep muscles of the chest and front of the arm, with the boundaries of the axilla.
The Subclavius (Fig. 411) is a small triangular muscle, placed between the
clavicle and the first rib. It arises by a short, thick tendon from the first rib and
its cartilage at their junction, in front of the costoclavicular ligament; the fleshy
fibers proceed obliquely upward and lateralward, to be inserted into the groove
on the under surface of the clavicle between the costoclavicular and conoid
ligaments.
Variations. — Insertion into coracoid process instead of clavicle or into both clavicle and coracoid
process. Sternoscapuhr fasciculus to the upper border of scapula. Stenwclai'icularis from manu-
brium to clavicle between Pectoralis major and coracoclavicular fascia.
The Serratus anterior (Serratus magnus) (Fig. 411) is a thin muscular sheet,
situated between the ribs and the scapula at the upper and lateral part of
THE MUSCLES AND FASCIA OF THE SHOULDER 439
the chest. It arises by fleshy digitations from the outer surfaces and superior
borders of the upper eight or nine ribs, and from the aponeuroses covering the
intervening Intercostales. Each digitation (except the first) arises from the
corresponding rib ; the first springs from the first and second ribs; and from the fascia
covering the first intercostal space. From this extensive attachment the fibers
pass backward, closely applied to the chest-wall, and reach the vertebral border
of the scapula, and are inserted into its ventral surface in the following manner.
The first digitation is inserted into a triangular area on the ventral surface of the
medial angle. The next two digitations spread out to form a thin, triangular
sheet, the base of which is directed backward and is inserted into nearly the whole
length of the ventral surface of the vertebral border. The lower five or six digita-
tions converge to form a fan-shaped mass, the apex of which is inserted, by muscular
and tendinous fibers, into a triangular impression on the ventral surface of the
inferior angle. The lower four slips interdigitate at their origins with the upper
five slips of the Obliquus externus abdominis.
Variations. — Attachment to tenth rib. Absence of attachments to first rib, to one or more of
the lower rit)s. Division into three parts; absence, or defect of middle part. Union with Levator
scapuIiP, External intercostals or External oblique.
Nerves. — The Pectoralis major is suppUed by the medial and lateral anterior thoracic nerves;
through these nerves the muscle receives filaments from all the spinal nerves entering into the
formation of the brachial plexus; the Pectorahs minor receives its fibers from the eighth cervical
and first thoracic nerves through the medial anterior thoracic nerve. The Subclavius is suplied
by a filament from the fifth and sixth cervical nerves; the Serratus anterior is supphed by the
long thoracic, which is derived from the fifth, sixth, and seventh cervical nerves.
Actions. — If the arm has been raised by the Deltoideus, the Pectorahs major will, conjointly
with the Latissimus dorsi and Teres major, depress it to the side of the chest. If acting alone,
it adducts and draws forward the arm, bringing it across the front of the chest, and at the same
time rotates it inward. The Pectoralis minor depresses the point of the shoulder, drawing the
scapula dowTiward and medialward toward the thorax, and throwing the inferior angle back-
ward. The Subcb-vius depresses the shoulder, carrying it downward and forward. When the
arms are fixed, all three of these muscles act upon the ribs; drawing them upward and expand-
ing the chest, and thus becoming very important agents in forced inspiration. The Serratus
anterior, as a whole, carries the scapula forward, and at the same time raises the vertebral border
of the bone. It is therefore concerned in the action of pushing. Its lower and stronger fibers
move forward the lower angle and assist the Trapezius in rotating the bone at the sternoclavicular
joint, and thus assist this muscle in raising the acromion and supporting weights upon the shoulder.
It is also an assistant to the Deltoideus in raising the arm, inasmuch as during the action of this
latter muscle it fixes the scapula and so steadies the glenoid cavity on which the head of the
humerus rotates. After the Deltoideus has raised the arm to a right angle with the trunk, the
Serratus anterior and the Trapezius, by rotating the scapula, raise the arm into an ahnost vertical
position. It is possible that when the shoulders are fixed the lower fibers of the Serratus anterior
may assist in raising and everting the ribs; but it is not the important inspiratory muscle it was
formerly beheved to be.
m. THE MUSCLES AND FASCIA OF THE SHOULDER.
In this group are included:
Deltoideus. Infraspinatus.
Subscapularis. Teres minor.
Supraspinatus. Teres major.
Deep Fascia. — The deep fascia covering the Deltoideus invests the muscle, arid
sends numerous septa between its fasciculi. In front it is continuous with the fascia
covering the Pectoralis major; behind, where it is thick and strong, with that
covering the Infraspinatus; above, it is attached to the clavicle, the acromion,
and the spine of the scapula; below, it is continuous with the deep fascia of the
' arm.
The Deltoideus (Deltoid muscle) (Fig. 410) is a large, thick, triangular muscle, which
covers the shoulder-joint in front, behind, and laterally. It arises from the anterior
440 MYOLOGY
border and upper surface of the lateral third of the clavicle ; from the lateral margin
and upper surface of the acromion, and from the lower lip of the posterior border
of the spine of the scapula, as far back as the triangular surface at its medial end.
From this extensive origin the fibers converge toward their insertion, the middle
passing vertically, the anterior obliquely backward and lateralward, the posterior
obliquely forward and lateralward ; they unite in a thick tendon, which is inserted
into the deltoid prominence on the middle of the lateral side of the body of the
humerus. At its insertion the muscle gives off an expansion to the deep fascia of
the arm. This muscle is remarkably coarse in texture, and the arrangement of
its fibers is somewhat peculiar; the central portion of the muscle — that is to say,
the part arising from the acromion — consists of oblique fibers; these arise in a
bipenniform manner from the sides of the tendinous intersections, generally four
in number, which are attached above to the acromion and pass downward parallel
to one another in the substance of the muscle. The oblique fibers thus formed are
inserted into similar tendinous intersections, generally three in number, which
pass upward from the insertion of the muscle and alternate with the descending
septa. The portions of the muscle arising from the clavicle and spine of the scapula
are not arranged in this manner, but are inserted into the margins of the inferior
tendon.
Variations. — Large variations uncommon. More or less splitting common. Continuation into
the Trapezius; fusion with the Pectoralis major; additional slips from the vertebral border of the
scapula, infraspinous fascia and axillary border of scapula not uncommon. Insertion varies in
extent or rarely is prolonged to origin of Bracliioradialis.
Nerves. — The Deltoideus is supplied by the fifth and sixth cervical through the axillary nerve.
Actions. — The Deltoideus raises the arm from the side, so as to bring it at right angles with
the trunk. Its anterior fibers, assisted by the Pectoralis major, draw the arm forward; and its
posterior fibers, aided by the Teres major and Latissimus dorsi, draw it backward.
Subscapular Fascia (fascia subscapular is) . — The subscapular fascia is a thin
membrane attached to the entire circumference of the subscapular fossa, and
affording attachment by its deep surface to some of the fibers of the Sub-
scapularis.
The Subscapularis (Fig. 411) is a large triangular muscle which fills the sub-
scapular fossa, and arises from its medial two-thirds and from the lower two-
thirds of the groove on the axillary border of the bone. Some fibers arise from
tendinous laminae which intersect the muscle and are attached to ridges on the
bone; others from an aponeurosis, which separates the muscle from the Teres
major and the long head of the Triceps brachii. The fibers pass lateralward,
and, gradually converging, end in a tendon which is inserted into the lesser tubercle
of the humerus and the front of the capsule of the shoulder-joint. The tendon
of the muscle is separated from the neck of the scapula by a large bursa, which
communicates with the cavity of the shoulder-joint through an aperture in the
capsule.
Nerves. — The Subscapularis is supphed by the fifth and sixth cervical nerves through the
upper and lower subscapular nerves.
Actions. — The Subscapularis rotates the head of the humerus inward; when the arm is raised,
it draws the humerus forward and downward. It is a powerful defence to the front of the shoulder-
joint, preventing displacement of the head of the humerus.
Supraspinatous Fascia (fascia supraspinata). — The supraspinatous fascia com-
pletes the osseofibrous case in which the Supraspinatus muscle is contained; it
affords attachment, by its deep surface, to some of the fibers of the muscle. It is
thick medially, but thinner laterally under the coracoacromial ligament.
The Supraspinatus (Fig. 412) occupies the whole of the supraspinatous fossa,
arising from its medial two-thirds, and from the strong supraspinatous fascia.
The muscular fibers converge to a tendon, which crosses the upper part of the
THE MUSCLES AND FASCIA OF THE SHOULDER
441
shoulder-joint, and is inserted into the highest of the three impressions on the
greater tubercle of the humerus; the tendon is intimately adherent to the capsule
of the shoulder-joint.
Infraspinatous Fascia {fascia infraspinata) .—The infraspinatous fascia is a dense
fibrous membrane, covering the Infraspinatous muscle and fixed to the circum fer-
ence of the infraspinatous fossa; it affords attachment, by its deep surface, to some
fibers of that muscle. It is intimately attached to the deltoid fascia along the over-
lapping border of the Deltoideus.
Fig. 412. — Muscles on the dorsum of the scapula, and the Triceps brachii.
The Infraspinatus (Fig. 412) is a thick triangular muscle, which occupies the
chief part of the infraspinatous fossa; it arises by fleshy fibers from its medial two-
thirds, and by tendinous fibers from the ridges on its surface; it also arises from
the infraspinatous fascia which covers it, and separates it from the Teretes major
and minor. The fibers converge to a tendon, which glides over the lateral border
of the spine of the scapula, and, passing across the posterior part of the capsule of
the shoulder-joint, is inserted into the middle impression on the greater tubercle
of the humerus. The tendon of this muscle is sometimes separated from the
capsule of the shoulder-joint by a bursa, which may communicate with the joint
cavity.
The Teres minor (Fig. 412) is a narrow, elongated muscle, which arises from
the dorsal surface of the axillary border of the scapula for the upper two-thirds of
its extent, and from two aponeurotic laminae, one of which separates it from the
Infraspinatus, the other from the Teres major. Its fibers run obliquely upward
and lateralward; the upper ones end in a tendon which is inserted into the lowest
of the three impressions on the greater tubercle of the humerus; the lowest fibers
are inserted directly into the humerus immediately below this impression. The
442 MYOLOGY
tendon of this muscle passes across, and is united with, the posterior part of the
capsule of the shoulder-joint.
Variations. — It is sometimes inseparable from the Infraspinatus.
The Teres major (Fig. 412) is a thick but somewhat flattened muscle, which
arises from the oval area on the dorsal surface of the inferior angle of the scapula,
and from the fibrous septa interposed between the muscle and the Teres minor
and Infraspinatus; the fibers are directed upward and lateralward, and end in a
flat tendon, about 5 cm. long, which is inserted into the crest of the lesser tubercle
of the humerus. The tendon, at its insertion, lies behind that of the Latissimus
dorsi, from which it is separated by a bursa, the two tendons being', however,
united along their lower borders for a short distance.
Nerves. — The Supraspinatus and Infraspinatus are suppUed by the fifth and sixth cervical
nerves through the suprascapular nerve; the Teres minor, by the fifth cervical, through the
axillary; and the Teres major, by the fifth and sixth cervical, through the lowest subscapular.
Actions. — The Supraspinatus assists the Deltoideus in raising the arm from the side of the
trunk and fixes the head of the humerus in the glenoid cavity. The Infraspinatus and Teres
minor rotate the head of the humerus outward; they also assist in carrying the arm backward.
One of the most important uses of these three muscles is to protect the shoulder-joint, the Supra-
spinatus supporting it above, and the Infraspinatus and Teres minor behind. The Teres major
assists the Latissimus dorsi in drawing the previously raised humerus downward and backward,
and in rotating it inward; when the arm is fixed it may assist the Pectorales and the Latissimus
dorsi in drawing the trunk forward.
IV. THE MUSCLES AND FASCIA OF THE ARM.
The muscles of the arm are :
Coracobrachialis. Brachialis.
Biceps brachii. Triceps brachii.
Brachial Fascia (fascia brachii; deep fascia of the arm). — The brachial fascia is
continuous with that covering the Deltoideus and the Pectoralis major, by means
of which it is attached, above, to the clavicle, acromion, and spine of the scapula;
it forms a thin, loose, membranous sheath for the muscles of the arm, and sends
septa between them; it is composed of fibers disposed in a circular or spiral direc-
tion, and connected together by vertical and oblique fibers. It differs in thickness
at different parts, being thin over the Biceps brachii, but thicker where it covers
the Triceps brachii, and over the epicondyles of the humerus: it is strengthened
by fibrous aponeuroses, derived from the Pectoralis major and Latissimus dorsi
medially, and from the Deltoideus laterally. On either side it gives off a strong
intermuscular septum, which is attached to the corresponding supracondylar
ridge and epicondyle of the humerus. The lateral intermuscular septum extends
from the lo\ver part of the crest of the greater tubercle, along the lateral supra-
condylar ridge, to the lateral epicondyle; it is blended with the tendon of the Del-
toideus, gives attachment to the Triceps brachii behind, to the Brachialis, Brachio-
radialis, and Extensor carpi radialis longus in front, and is perforated by the radial
nerve and profunda branch of the brachial artery. The medial intermuscular
septum, thicker than the preceding, extends from the lower part of the crest of
the lesser tubercle of the humerus below the Teres major, along the medial supra-
condylar ridge to the medial epicondyle; it is blended with the tendon of the
Coracobrachialis, and affords attachment to the Triceps brachii behind and the
Brachialis in front. It is perforated by the ulnar nerve, the superior ulnar
collateral artery, and the posterior branch of the inferior ulnar collateral artery.
At the elbow, the deep fascia is attached to the epicondyles of the humerus and
the olecranon of the ulna, and is continuous with the deep fascia of the forearm.
THE MUSCLES AND FASCIA OF THE ARM
443
Just below the middle of the arm, on its medial side, is an oval opening in the deep
fascia, which transmits the basilic vein and some lymphatic vessels.
The Coracobrachialis (Fig. 41 1), the smallest of the three muscles in this region,
is situated at the upper and medial part of the arm. It arises from the apex of
the coracoid process, in common with the short head of the Biceps brachii, and from
the intermuscular septum between the two muscles; it is inserted by means of a flat
tendon into an impression at the middle of the medial surface and border of the
body of the humerus between the origins of the Triceps brachii and Brachialis.
It is perforated by the musculocutaneous nerve.
Biceps brachii M
Cephalic vein-
Lateral antibrachial
cutaneous nerve
Brachial artery and veins
Aledioji nerve
Medial antibrachial
uianeous nerve
■■^■Basilic vein
... Ulnar nerve
Brachialis M-
Radial nerve-
Dorsal antibrachial
cutaneous nerve
Radial collateral artery'
Lateral intermuscular
septum of liumeru
Superior ulnar
collateral artery
Medial intermuscular
septum of humerus
-•Humerus
Triceps brachii M.
Fig. 413. — Cross-section through the middle of upper arm. (Eycleshymer and Schoemaker.')
Variations. — A laony head may reach the medial epicondyle; a short head more rarely found
may insert into the lesser tubercle.
The Biceps brachii {Biceps; Biceps flexor ciibiti) (Fig. 411) is a long fusiform
muscle, placed on the front of the arm, and arising by two heads, from which
circumstance it has received its name. The short head arises bv a thick flattened
tendon from the apex of the coracoid process, in common with the Coracobrachialis.
The long head arises from the supraglenoid tuberosity at the upper margin of the
glenoid cavity, and is continuous with the glenoidal labrum. This tendon, enclosed
in a special sheath of the synovial membrane of the shoulder-joint, arches over
the head of the humerus; it emerges from the capsule through an opening close
to the humeral attachment of the ligament, and descends in the intertubercular
groove; it is retained in the groove by the transverse humeral ligament and by a
fibrous prolongation from the tendon of the Pectoralis major. Each tendon is
succeeded by an elongated muscular belly, and the two bellies, although closely
applied to each other, can readily be separated until within about 7.5 cm. of the
elbow-joint. Here they end in a flattened tendon, which is inserted into the rough
posterior portion of the tuberosity of the radius, a bursa being interposed between
the tendon and the front part of the tuberosity. As the tendon of the muscle
approaches the radius it is twisted upon itself, so that its anterior surface becomes
' A Cross-section Anatomy, New York, 1911.
444 MYOLOGY
lateral and is applied to the tuberosity of the radius at its insertion. Opposite
the bend of the elbow the tendon gives off, from its medial side, a broad aponeu-
rosis, the lacertus fibrosus (bicipital fascia) which passes obliquely downward and
medialward across the brachial artery, and is continuous with the deep fascia
covering the origins of the Flexor muscles of the forearm (Fig. 410).
Variations. — A third head (10 per cent.) to the Biceps brachii is occasionally found, arising at
the upper and medial part of the Brachialis, with the fibers of which it is continuous, and inserted
into the lacertus fibrosus and medial side of the tendon of the muscle. In most cases this additional
slip lies behind the brachial artery in its coarse down the arm. In some instances the tlurd head
consists of two shps, which pass down, one in front of and the other behind the artery, concealing
the vessel in the lower half of the arm. More rarely a fourth head occurs arising from the outer
side of the humerus, from the intertubercular groove, or from the greater tubercle. Other heads
are occasionally found. Slips sometimes pass from the inner border of the muscle over the brachial
artery to the medial intermuscular septum, or the medial epicondyle; more rarely to the Pronator
teres or Brachialis. The long head may be absent or arise from the intertubercular groove.
The Brachialis (Brachialis anticus) (Fig. 411) covers the front of the elbow-joint
and the lower half of the humerus. It arises from the lower half of the front
of the humerus, commencing above at the insertion of the Deltoideus, which it
embraces by two angular processes. Its origin extends below to within 2.5 cm.
of the margin of the articular surface. It also arises from the intermuscular septa,
but more extensively from the medial than the lateral; it is separated from the
lateral below by the Brachioradialis and Extensor carpi radialis longus. Its fibers
converge to a thick tendon, which is inserted into the tuberosity of the ulna and
the rough depression on the anterior surface of the coronoid process.
Variations. — Occasionally doubled; additional slips to the Supinator, Pronator teres, Biceps,
lacertus filjrosus, or radius are more rarely foimd.
Nerves. — The Coracobrachialis, Biceps brachii and Brachialis are supplied by the musculo-
cutaneous nerve; the BrachiaUs usually receives an additional filament from the radial. The
Coracobrachialis receives its supply primarily from the seventh cervical, the Biceps brachii and
Brachiahs from the fifth and sixth cervical nerves.
Actions. — The Coracobrachiahs draws the humerus forward and medialward, and at the
same time assists in retaining the head of the bone in contact with the glenoid cavity. The
Biceps brachii is a flexor of the elbow and, to a less extent, of the shoulder; it is also a powerful
supinator, and serves to render tense the deep fascia of the forearm by means of the lacertus
fibrosus given off from its tendon. The Brachiahs is a flexor of the forearm, and forms an impor-
tant defence to the elbow-joint. When the forearm is fixed, the Biceps brachii and Brachialis
flex the arm upon the forearm, as in efforts of cUmbing.
The Triceps brachii (Triceps; Triceps exteyisor cuhiti) (Fig. 412) is situated on
the back of the arm, extending the entire length of the dorsal surface of the humerus.
It is of large size, and arises by three heads (long, lateral, and medial), hence its
name.
The long head arises by a flattened tendon from the infraglenoid tuberosity
of the scapula, being blended at its upper part with the capsule of the shoulder-
joint; the muscular fibers pass downward between the two other heads of the
muscle, and join with them in the tendon of insertion.
The lateral head arises from the posterior surface of the body of the humerus,
between the insertion of the Teres minor and the upper part of the groove for the
radial nerve, and from the lateral border of the humerus and the lateral intermus-
cular septum; the fibers from this origin converge toward the tendon of insertion.
The medial head arises from the posterior surface of the body of the humerus,
below the groove for the radial nerve; it is narrow and pointed above, and extends
from the insertion of the Teres major to within 2.5 cm. of the trochlea: it also
arises from the medial border of the humerus and from the back of the whole
length of the medial intermuscular septum. Some of the fibers are directed
downward to the olecranon, while others converge to the tendon of insertion.
The tendon of the Triceps brachii begins about the middle of the muscle : it con-
THE VOLAR ANTIBRACHIAL MUSCLES 445
sists of two aponeurotic laminae, one of which is subcutaneous and covers the back
of the lower half of the muscle; the other is more deeply seated in the substance
of the muscle. After receiving the attachment of the muscular fibers, the two
lamellae join together above the elbow, and are inserted, for the most part, into
the posterior portion of the upper surface oi' the olecranon; a band of fibers is,
however, continued downward, on the lateral side, over the Anconeus, to blend
with the deep fascia of the forearm.
The long head of the Triceps brachii descends between the Teres minor and Teres major,
dividing the triangular space between these two muscles and the humerus into two smaller spaces,
one triangular, the other quadrangular (Fig. 412). The triangular space contains the scapular
circumflex vessels; it is bounded by the Teres minor above, the Teres major below, and the
scapular head of the Triceps laterally. The quadrangular space transmits the posterior humeral
circumflex vessels and the axillary nerve; it is bounded by the Teres minor and capsule of the
shoulder-joint above, the Teres major below, the long head of the Triceps brachii medially, and
the humerus laterally.
Variations.— A fourth head from the inner part of the humerus; a slip between Triceps and
Latissimus dorsi corresponding to the Dorso-ejntrochlearis.
The SubanconaBUS is the name given to a few fibers which spring from the deep surface of
the lower part of the Triceps brachii, and are inserted into the posterior ligament and synovial
membrane of the elbow-joint.
Nerves. — The Triceps brachii is supplied by the seventh and eighth cervical nerves through
the radial nerve.
Actions. — The Triceps brachii is the great extensor muscle of the forearm, and is the direct
antagonist of the Biceps brachii and Brachialis. When the arm is extended, the long head of
the muscle may assist the Teres major and Latissimus dorsi in drawing the humerus backward
and in adducting it to the thorax. The long head supports the under part of the shoulder-joint.
The SubanconaBUS draws up the synovial membrane of the elbow-joint during extension of the
forearm.
V. THE MUSCLES AND FASCLffi OF THE FOREARM.
Antibrachial Fascia {fascia antibrachU; deep fascia of the forearm). — The anti-
brachial fascia continuous above with the brachial fascia, is a dense, membranous
investment, which forms a general sheath for the muscles in this region; it is at-
tached, behind, to the olecranon and dorsal border of the ulna, and gives off from its
deep surface numerous intermuscular septa, which enclose each muscle separately.
Over the Flexor tendons as they approach the wrist it is especially thickened, and
forms the volar carpal ligament. This is continuous with the transverse carpal liga-
ment, and forms a sheath for the tendon of the Palmaris longus which passes over
the transverse carpal ligament to be inserted into the palmar aponeurosis. Behind,
near the wrist-joint, it is thickened by the addition of many transverse fibers, and
forms the dorsal carpal ligament. It is much thicker on the dorsal than on the volar
surface, and at the lower than at the upper part of the forearm, and is strengthened
above by tendinous fibers derived from the Biceps brachii in front, and from the
Triceps brachii behind. It gives origin to muscular fibers, especially at the upper
part of the medial and lateral sides of the forearm, and forms the boundaries of
a series of cone-shaped cavities, in which the muscles are contained. Besides the
vertical septa separating the individual muscles, transverse septa are given off
both on the volar and dorsal surfaces of the forearm, separating the deep from the
superficial layers of muscles. Apertures exist in the fascia for the passage of
vessels and nerves; one of these apertures of large size, situated at the front of the
elbow, serves for the passage of a communicating branch between the superficial
and deep veins.
The antibrachial or forearm muscles may be divided into a volar and a dorsal
group.
1. The Volar Antibrachial Muscles.
These muscles are divided for convenience of description into two groups,
superficial and deep.
446 MYOLOGY
The Superficial Group (Fig. 414),
Pronator teres. Palmaris longus.
Flexor carpi radialis. Flexor carpi ulnaris.
Flexor digitorum sublimis.
The muscles of this group take origin from the medial epicondyle of the humerus
by a common tendon; they receive additional fibers from the deep fascia of the fore-
arm near the elboAv, and from the septa which pass from this fascia between the
individual muscles.
The Pronator teres has two heads of origin — humeral and ulnar. The humeral
head, the larger and more superficial, arises immediately above the medial epi-
condyle, and from the tendon common to the origin of the other muscles; also
from the intermuscular septum between it and the Flexor carpi radialis and from
the antibrachial fascia. The ulnar head is a thin fasciculus, which arises from the
medial side of the coronoid process of the ulna, and joins the preceding at an acute
angle. The median nerve enters the forearm between the two heads of the muscle,
and is separated from the ulnar artery by the ulnar head. The muscle passes ob-
liquely across the forearm, and ends in a flat tendon, which is inserted into a rough
impression at the middle of the lateral surface of the body of the radius. The
lateral border of the muscle forms the medial boundarv of a triangular hollow
situated in front of the elbow-joint and containing the brachial artery, median
nerve, and tendon of the Biceps brachii.
Variations.— Absence of ulnar head; additional slips from the medial intermuscular septum,
from the Biceps and from the Brachialis anticus occasionalh' occur.
The Flexor carpi radialis lies on the medial side of the preceding muscle. It
arises from the medial epicondyle by the common tendon; from the fascia of the
forearm; and from the intermuscular septa between it and the Pronator teres
laterally, the Palmaris longus medially, and the Flexor digitorum sublimis beneath.
Slender and aponeurotic in structure at its commencement, it increases in size,
and ends in a tendon which forms rather more than the lower half of its length.
This tendon passes through a canal in the lateral part of the transverse carpal
ligament and runs through a groove on the greater multangular bone; the groove
is converted into a canal by fibrous tissue, and lined by a mucous sheath. The ten-
don is inserted into the base of the second metacarpal bone, and sends a slip to
the base of the third metacarpal bone. The radial artery, in the lower part of the
forearm, lies between the tendon of this muscle and the Brachioradialis.
Variations. — Slips from the tendon of the Biceps, the lacertus fibrosus. the coronoid, and the
radius have been found. Its insertion often varies and may be mostly into the annular ligament,
the trapezium, or the fourth metacarpal as weU as the second or third. The muscle may be
absent .
The Palmaris longus is a slender, fusiform muscle, lying on the medial side
of the preceding. It arises from the medial epicondyle of the humerus by the
common tendon, from the intermuscular septa between it and the adjacent
muscles, and from the antibrachial fascia. It ends in a slender, flattened tendon,
which passes over the upper part of the transverse carpal ligament, and is inserted
into the central part of the transverse carpal ligament and lower part of the
palmar aponeurosis, frequently sending a tendinous slip to the short muscles of
the thumb.
Variations. — One of the most variable muscles in the body. Tins muscle is often absent about
(10 per cent.), and is subject to many variations; it may be tendinous above and muscular below;
or it may be muscular in the center with a tendon above and below ; or it may present two muscular
bundles with a central tendon; or finally it may consist solely of a tendinous band. The muscle
may be double. Slips of origin from the coronoid process or from the radius have been seen.
THE VOLAR ANTIBRACHIAL MUSCLES
447
Partial or complete insertion into the fascia
of the forearm, into the tendon of the Flexor
carpi iilnaris and pisiform bone, into the
na^•icula^, and into the muscles of the little
finger have been observed.
The Flexor carpi ulnaris lies along
the ulnar side of the forearm. It
arises by two heads, humeral and
ulnar, connected by a tendinous arch,
beneath which the ulnar nerve and
posterior ulnar recurrent artery pass.
The humeral head arises from the
Fig. 414. — Front of the left forearm. Superficial
muscles.
Fig. 415. — Front of the left forearm. Deep
muscles.
448 MYOLOGY
medial epicondyle of the humerus by the common tendon; the ulnar bead
arises from the medial margin of the olecranon and from the upper two-thirds
of the dorsal border of the ulna by an aponeurosis, common to it and the Extensor
carpi ulnaris and Flexor digitorum profundus; and from the intermuscular septum
between it and the Flexor digitorum sublimis. The fibers end in a tendon, which
occupies the anterior part of the lower half of the muscle and is inserted into the
pisiform bone, and is prolonged from this to the hamate and fifth metacarpal
bones by the pisohamate and pisometacarpal ligaments; it is also attached by a
few fibers to the transverse carpal ligament. The ulnar vessels and nerve lie on
the lateral side of the tendon of this muscle, in the lower two-thirds of the forearm.
Variations. — Slips of origin from the coronoid. The Epitrochleo-anconceus, a small muscle often
present runs from the back of the inner condyle to the olecranon, over the ulnar nerve.
The Flexor digitorum sublimis is placed beneath the previous muscle; it is
the largest of the muscles of the superficial group, and arises by three heads —
humeral, ulnar, and radial. The humeral head arises from the medial epicondyle
of the humerus by the common tendon, from the ulnar collateral ligament of the
elbow-joint, and from the intermuscular septa between it and the preceding
muscles. The ulnar head arises from the medial side of the coronoid process,
above the ulnar origin of the Pronator teres (see Fig. 213, page 216). The radial
head arises from the oblique line of the radius, extending from the radial tuberosity
to the insertion of the Pronator teres. The muscle speedily separates into two
planes of muscular fibers, superficial and deep: the superficial plane divides into
two parts which end in tendons for the middle and ring fingers; the deep plane
gives off a muscular slip to join the portion of the superficial plane which is asso-
ciated with the tendon of the ring finger, and then divides into two parts, which
end in tendons for the index and little fingers. As the four tendons thus formed
pass beneath the transverse carpal ligament into the palm of the hand, they are
arranged in pairs, the superficial pair going to the middle and ring fingers, the deep
pair to the index and little fingers. The tendons diverge from one another in the
palm and form dorsal relations to the superficial volar arch and digital branches
of the median and ulnar nerves. Opposite the bases of the first phalanges each
tendon divides into two slips to allow of the passage of the corresponding tendon
of the Flexor digitorum profundus; the two slips then reunite and form a grooved
channel for the reception of the accompanying tendon of the Flexor digitorum
profundus. Finally the tendon divides and is inserted into the sides of the second
phalanx about its middle.
Variations. — Absence of radial head, of little finger portion; accessory slips from ulnar tuberosity
to the index and middle finger portions; from the inner head to the Flexor profundus; fi-om the
ulnar or annular ligament to the little finger.
The Deep Group (Fig. 415).
Flexor digitorum profundus. Flexor pollicis longus.
Pronator quadratus.
The Flexor digitorum profundus is situated on the ulnar side of the forearm,
immediately beneath the superficial Flexors. It arises from the upper three-
fourths of the volar and medial surfaces of the body of the ulna, embracing the
insertion of the Brachialis above, and extending below to within a short distance
of the Pronator quadratus. It also arises from a depression on the medial side of
the coronoid process; by an aponeurosis from the upper three-fourths of the dorsal
border of the ulna, in common with the Flexor and Extensor carpi ulnaris; and
from the ulnar half of the interosseous membrane. The muscle ends in four tendons
which run under the transverse carpal ligament dorsal to the tendons of the Flexor
THE VOLAR ANTIBRACHIAL MUSCLES 449
digitorum sublimis. Opposite the first phalanges the tendons pass through the
openings in the tendons of the Flexor digitorum sublimis, and are finally inserted
into the bases of the last phalanges. The portion of the muscle for the index finger
is usually distinct throughout, but the tendons for the middle, ring, and little
fingers are connected together by areolar tissue and tendinous slips, as far as the
palm of the hand.
Fibrous Sheaths of the Flexor Tendons.— After leaving the palm, the tendons
of the Flexores digitorum sublimis and profundus lie in osseo-aponeurotic canals
(Fig. 427), formed behind by the phalanges and in front by strong fibrous bands,
which arch across the tendons, and are attached on either side to the margins of
the phalanges. Opposite the middle of the proximal and second phalanges the
bands (digital vaginal ligaments) are very strong, and the fibers are transverse;
but opposite the joints they are much thinner, and consist of annular and cruciate
ligamentous fibers. Each canal contains a mucous sheath, which is reflected on
the contained tendons.
Within each canal the tendons of the Flexores digitorum sublimis and profundus
are connected to each other, and to the phalanges, by slender, tendinous bands,
called vincula tendina (Fig. 416). There are two sets of these; (a) the vincula
brevia, which are two in number in each finger, and consist of triangular bands
of fibers, one connecting the tendon of the Flexor digitorum sublimis to the front
of the first interphalangeal joint and head of the first phalanx, and the other the
tendon of the Flexor digitorum profundus to the front of the second interphalan-
geal joint and head of the second phalanx; (6) the vincula longa, which connect
the under surfaces of the tendons of the Flexor digitorum profundus to those of the
subjacent Flexor sublimis after the tendons of the former have passed through
the latter.
Variations. — The index finger portion may arise partly from the upper part of the radius. Slips
from the inner head of the Flexor sublimis, medial epicondyle, or the coronoid are found. Connec-
tion with the Flexor pollicis longus.
Four small muscles, the Lumbricales, are connected with the tendons of the
Flexor profundus in the palm. They will be described with the muscles of the
hand (page 464).
The Flexor pollicis longus is situated on the radial side of the forearm, lying
in the same plane as the preceding. It arises from the grooved volar surface of
the body of the radius, extending from immediately below the tuberosity and
oblique line to within a short distance of the Pronator quadratus. It arises also
from the adjacent part of the interosseous membrane, and generally by a fleshy
slip from the medial border of the coronoid process, or from the medial epicondyle
of the humerus. The fibers end in a flattened tendon, which passes beneath the
transverse carpal ligament, is then lodged between the lateral head of the Flexor
pollicis brevis and the oblique part of the Adductor pollicis, and, entering an osseo-
aponeurotic canal similar to those for the Flexor tendons of the fingers, is inserted
into the base of the distal phalanx of the thumb. The volar interosseous nerve
and vessels pass downward on the front of the interosseous membrane between
the Flexor pollicis longus and Flexor digitorum profundus.
Variations. — Slips may connect with Flexor sublimis, or Profundus, or Pronator teres. An addi-
tional tendon to the index finger is sometimes found.
The Pronator quadratus is a small, flat, quadrilateral muscle, extending across
the front of the lower parts of the radius and ulna. It arises from the pronator
ridge on the lower part of the volar surface of the body of the ulna; from the medial
part of the volar surface of the lower fourth of the ulna ; and from a strong apon-
eurosis which covers the medial third of the muscle. The fibers pass lateral ward
29
450
MYOLOGY
and slightly downward, to be inserted into the lower fourth of the lateral border
and the volar surface of the body of the radius. The deeper fibers of the muscle
are inserted into the triangular area above the ulnar notch of the radius — an
attachment comparable with the origin of the Supinator from the triangular area
below the radial notch of the ulna.
Tendon of Ext.
carpi rad. longus
Tendon of Ext.
digitorum communis
Tendon of Extensor indicis
proprius
wm 7
'k^iW/''^ ' CV\ — Tendon of Ext. poinds hrevis
First Lumbricalis
Vinculo brevia
Tendon of Abductor
pollicis longus
Greater multangidar hone
Radial artery
^^r — Tendon of Ext. pollicis longu
Flexor digitorum snhlimis
lexor digitorum, profundus
Vincida longa
Fia. 416. — Tendons of forefinger and vincula tendina
Variations. — Rarely absent; split into two or three layers; increased attachment upward or
downward.
Nerves. — All the muscles of the superficial layer are supplied by the median nerve, excepting
the Flexor carpi ulnaris, which is supplied by the ulnar. The Pronator teres, the Flexor carpi
radialis, and the Palmaris longus derive their supply primarily from the sixth cervical nerve;
the Flexor digitorum sublimis from the seventh and eighth cervical and first thoracic nerves,
and the Flexor carpi ulnaris from the eighth cervical and first thoracic. Of the deep layer, the
Flexor digitorum profundus is supplied by the eighth cervical and first thoracic through the
■ ulnar, and the volar interosseous branch of the median. The Flexor pollicis longus and Pronator
quadratus are supplied by the eighth cervical and first thoracic through the volar interosseous
branch of the median.
Actions.— These muscles act upon the forearm, the wrist, and hand. The Pronator teres
rotates the radius upon the ulna, rendering the hand prone; when the radius is fixed, it assists
in flexing the forearm. The Flexor carpi radialis is a flexor and abductor of the wrist; it also
assists in pronating the hand, and in bending the elbow. The Flexor carpi ulnaris is a flexor and
adductor of the wrist; it also assists in bending the elbow. The Palmaris longus is a flexor of the
wrist-joint; it also assists in flexing the elbow. The Flexor digitorum subhmis flexes first the
middle and then the proximal phalanges; it also assists in flexing the wrist and elbow. The
Flexor digitorum profundus is one of the flexors of the phalanges. After the Flexor subhmis
has bent the second phalanx, the Flexor profundus flexes the terminal one; but it cannot do so
until after the contraction of the superficial muscle. It also assists in flexing the wrist. The
THE DORSAL ANTIBRACHIAL MUSCLES
451
Flexor pollicis longus is a flexor of the phalanges of the thumb; when the thumb is fixed, it assists
in flexing the wrist. The Pronator quadratus rotates the radius upon the ulna, rendering the
hand prone.
Flexor carpi radialis M.
Antibrachial inter os-
seoiis membrane
Lateral antibrachial
cutaneous nerve\
Radial artery
and nervc'\
Median nerve
Palmaris longus M.
Medial antibrachial
cutaneous nerve
[volar branch]
Flexor digitorum
sublimis M.
Cephalic vein.,
Brachioradialis M...
Flexor pollicis
longus M.
Radius ~.L.,
Tendo m. pronatoris _,\- ■ ■
tcrctis
Extensorcs carpi radiales,-
longus and breiis Mm
Extensor digitorum,
communis M.
Ulnar artery and nerve
Flexor digitorum
profundus M.
-Flexor carpi ulnaris
-Basilic vein
Ulna
Abductor pollicis
longus M. •
Volar interosseous artery
and volar antibrachial
interosseous nerve
Extensor carpi
ulnaris M.
Extensor pollicis
longus M.
Extensor digiti quinti
proprius M. and dor-
sal interosseous artery
Fig. 417. — Cross-section through the middle of the forearm. (Eycleshymer and Schoemaker.)
2. The Dorsal Antibrachial Muscles.
These muscles are divided for convenience of description into two groups,
superficial and deep.
The Superficial Group (Fig. 418).
Brachioradialis. Extensor digitorum communis.
Extensor carpi radialis longus. . Extensor digiti quinti proprius.
Extensor carpi radialis brevis. Extensor carpi ulnaris.
Anconseus.
The Brachioradialis (Suinnator longus) is the most superficial muscle on the
radial side of the forearm. It arises from the upper two-thirds of the lateral
supracondylar ridge of the humerus, and from the lateral intermuscular septum,
being limited above by the groove for the radial nerve. Interposed between it
and the Brachialis are the radial nerve and the anastomosis between the anterior
branch of the profunda artery and the radial recurrent. The fibers end above
the middle of the forearm in a flat tendon, which is inserted into the lateral side
of the base of the styloid process of the radius. The tendon is crossed near its
insertion by the tendons of the Abductor pollicis longus and Extensor pollicis
brevis; on its ulnar side is the radial artery.
Variations. — Fasion with the Brachialis; tendon of insertion may be divided into two or three
shps; insertion partial or complete into the middle of the radius, fasciculi to the tendon of the
Biceps, the tuberosity or oblique line of the radius; slips to the Extensor carpi radialis longus or
Abductor poUicis longus; absence; rarely doubled.
452 MYOLOGY
The Extensor carpi radialis longus {Extensor carpi radialis longior) is placed partly
beneath the Brachioradialis. It arises from the lower third of the lateral supracon-
dylar ridge of the humerus, from the lateral intermuscular septum, and by a few
fibers from the common tendon of origin of the Extensor muscles of the forearm.
The fibers end at the upper third of the forearm in a flat tendon, which runs along
the lateral border of the radius, beneath the Abductor pollicis longus and Extensor
pollicis brevis; it then passes beneath the dorsal carpal ligament, where it lies in a
groove on the back of the radius common to it and the Extensor carpi radialis brevis,
immediately behind the styloid process. It is inserted into the dorsal surface of
the base of the second metacarpal bone, on its radial side.
The Extensor carpi radialis brevis {Extensor carpi radialis brerior) is shorter and
thicker than the preceding muscle, beneath which it is placed. It arises from the
lateral epicondyle of the humerus, by a tendon common to it and the three following
muscles; from the radial collateral ligament of the elbow-joint; from a strong
aponeurosis which covers its surface; and from the intermuscular septa between it
and the adjacent muscles. The fibers end about the middle of the forearm in a
flat tendon, which is closely connected with that of the preceding muscle, and
accompanies it to the wrist; it passes beneath the Abductor pollicis longus and
Extensor pollicis brevis, then beneath the dorsal carpal ligament, and is inserted
into the dorsal surface of the base of the third metacarpal bone on its radial side.
Under the dorsal carpal ligament the tendon lies on the back of the radius in
a shallow groove, to the ulnar side of that which lodges the tendon of the Extensor
carpi radialis, longus, and separated from it by a faint ridge.
The tendons of the two preceding muscles pass through the same compartment
of the dorsal carpal ligament in a single mucous sheath.
Variations. — Either muscle may split into two or three tendons of insertion to the second and
third or even the fourth metacarpal. The two muscles may unite into a single beUy with two
tendons. Cross slips between the two muscles may occur. The Extensor carpi radialis inter-
medins rarely arises as a distinct muscle from the humerus, but is not uncommon as an accessory
slip from one or both muscles to the second or third or both metacarpals. The Exiensar carpi
radialis accessorius is occasionallj- foimd arising from the humerus wth or below the Extensor carpi
radialis longus and inserted into the first metacarpal, the Abductor pollicis brevis, the First dorsal
interosseous, or elsewhere.
The Extensor digitorum communis arises from the lateral epicondyle of the
humerus, by the common tendon; from the intermuscular septa between it and the
adjacent muscles, and from the antibrachial fascia. It divides below into four
tendons, which pass, together with that of the Extensor indicis proprius, through
a separate compartment of the dorsal carpal ligament, within a mucous sheath.
The tendons then diverge on the back of the hand, and are inserted into the second
and third phalanges of the fingers in the following manner. Opposite the meta-
carpophalangeal articulation each tendon is bound by fasciculi to the collateral
ligaments and serves as the dorsal ligament of this joint; after having crossed the
joint, it spreads out into a broad aponeurosis, which covers the dorsal surface of
the first phalanx and is reinforced, in this situation, by the tendons of the Inter-
ossei and Lumbricalis. Opposite the first interphalangeal joint this aponeurosis
divides into three slips ; an intermediate and two collateral : the former is inserted
into the base of the second phalanx; and the two collateral, which are continued
onward along the sides of the second phalanx, unite by their contiguous margins,
and are inserted into the dorsal surface of the last phalanx. As the tendons cross
the interphalangeal joints, they furnish them with dorsal ligaments. The tendon
to the index finger is accompanied by the Extensor indicis proprius, which lies
on its ulnar side. On the back of the hand, the tendons to the middle, ring, and
little fingers are connected by two obliquely placed baruds, one from the third
tendon passing downward and lateralward to the second tendon, and the other
THE DORSAL ANTIBRACHIAL MUSCLES
453
Abdtictor
poUici^
lonfjiis
Ext. 2>ollicis
b re vis
Ext. poinds
lunyus
Fig. 418. — Posterior surface of the forearm.
Superficial muscles.
Fia. 419. — Posterior surface of the forearm,
muscles.
Deep
454 MYOLOGY
passing from the same tendon downward and medialward to the fourth. Occa-
sionally the first tendon is connected to the second by a thin transverse band.
Variations. — An increase or decrease in the number of tendons is common; an additional slip
to the thumb is sometimes present.
The Extensor digiti quinti proprius {Extensor minimi digiti) is a slender muscle
placed on the medial side of the Extensor digitorum communis, with which it is
generally connected. It arises from the common Extensor tendon by a thin
tendinous slip, from the intermuscular septa between it and the adjacent muscles.
Its tendon runs through a compartment of the dorsal carpal ligament behind the
distal radio-ulnar joint, then divides into two as it crosses the hand, and finally
joins the expansion of the Extensor digitorum communis tendon on the dorsum
of the first phalanx of the little finger.
Variations. — An additional fibrous slip from the lateral epicondyle; the tendon of insertion may
not divide or may send a slip to the ring finger. Absence of muscle rare; fusion of the belly with
the Extensor digitorum communis not uncommon.
The Extensor carpi ulnaris lies on the ulnar side of the forearm. It arises
from the lateral epicondyle of the humerus, by the common tendon; by an aponeu-
rosis from the dorsal border of the ulna in common with the Flexor carpi ulnaris
and the Flexor digitorum profundus; and from the deep fascia of the forearm.
It ends in a tendon, which runs in a groove between the head and the styloid
process of the ulna, passing through a separate compartment of the dorsal carpal
ligament, and is inserted into the prominent tubercle on the ulnar side of the base
of the fifth metacarpal bone.
Variations. — Doubling; reduction to tendinous band; insertion partiallj^ into fourth metacarpal.
In many cases (52 per cent.) a slip is continued from the insertion of the tendon anteriorly
over the Opponens digiti quinti, to the fascia covering that muscle, the metacarpal bone, the
capsule of the metacarpoj)halangeal articulation, or tb.e first phalanx of the little finger. This slip
may be replaced by a muscular fasciculus arising from or near the pisiform.
The Anconseus is a small triangular muscle which is placed on the back of the
elbow-joint, and appears to be a continuation of the Triceps brachii. It arises
by a separate tendon from the back part of the lateral epicondyle of the humerus ;
its fibers diverge and are inserted into the side of the olecranon, and upper fourth
of the dorsal surface of the body of the ulna.
The Deep Group (Fig. 419).
Supinator. Extensor pollicis brevis.
Abductor pollicis longus. Extensor pollicis longus.
Extensor indicis proprius.
The Supinator (Supinator hrevis) (Fig. 420) is a broad muscle, curved around
the upper third of the radius. It consists of two planes of fibers, between which
the deep branch of the radial nerve lies. The two planes arise in common — the
superficial one by tendinous and the deeper by muscular fibers— from the lateral
epicondyle of the humerus; from the radial collateral ligament of the elbow-joint,
and the annular ligament; from the ridge on the ulna, which runs obliquely down-
ward from the dorsal end of the radial notch; from the triangular depression below
the notch; and from a tendinous expansion which covers the surface of the muscle.
The superficial fibers surround the upper part of the radius, and are inserted into
the lateral edge of the radial tuberosity and the oblique line of the radius, as low
down as the insertion of the Pronator teres. The upper fibers of the deeper plane
THE DORSAL ANTIBRACHIAL MUSCLES
455
the neck of the radius above the tuber-
its medial surface; the greater part of
the dorsal and lateral surfaces of the
oblique line and the head of the bone.
form a sling-like fasciculus, which encircles
osity and is attached to the back part of
this portion of the muscle is inserted into
body of the radius, midway between the
The Abductor pollicis longus (Ex-
tensor OSS. metacarpi pollicis) lies im-
mediately below the Supinator and
is sometimes united with it. It
arises from the lateral part of the
dorsal surface of the body of the ulna
below the insertion of the Anco-
nseus, from the interosseous mem-
brane, and from the middle third of
the dorsal surface of the body of the
radius. Passing obliquely downward
and lateralward, it ends in a tendon,
which runs through a groove on the
lateral side of the lower end of the
radius, accompanied by the tendon
of the Extensor pollicis brevis, and
is inserted into the radial side of the
base of the first metacarpal bone.
It occasionally gives off two slips
near its insertion: one to the greater
multangular bone and the other to
blend with the origin of the Abduc-
tor pollicis brevis.
Variations. — • More or loss doubling of
muscle and tendon with insertion of the
extra tendon into the first metacarpal, the
greater multangular, or into the Abductor
pollicis brevis or Opponens pollicis.
The Extensor pollicis brevis (Ex-
tensor primi internodii pollicis) lies
on the medial side of, and is closely
connected with, the Abductor pollicis
longus. It arises from the dorsal surface of the body of the radius below that
muscle, and from the interosseous membrane. Its direction is similar to that of
the Abductor pollicis longus, its tendon passing through the same groove on the
lateral side of the lower end of the radius, to be inserted into the base of the first
phalanx of the thumb.
Lateral epicondyle
Radial collateral I ig.
Annular ligament
Deep branch of radial
nerve
Interosseous recurrent
art.
Deep branch of radial
nerve
Dorsal interosseous
art.
Fm. 420. — The Supinator.
Variations. — Absence; fusion of tendon with that of the Extensor pollicis longus.
The Extensor pollicis longus (Extensor secundi internodii pollicis) is much larger
than the preceding muscle, the origin of which it partly covers. It arises from
the lateral part of the middle third of the dorsal surface of the body of the ulna
below the origin of the Abductor pollicis longus, and from the interosseous mem-
brane. It ends in a tendon, which passes through a separate compartment in the
dorsal carpal ligament, lying in a narrow, oblique groove on the back of the lower
end of the radius. It then crosses obliquely the tendons of the Extensores carpi
radialis longus and brevis, and is separated from the Extensor brevis pollicis by a
triangular interval, in which the radial artery is found; and is finally inserted into
the base of the last phalanx of the thumb. The radial artery is crossed by the
456 MYOLOGY
tendons of the Abductor pollicis longus and of the Extensores pollicis longus and
brevis.
The Extensor indicis proprius (Extensor indicis) is a narrow, elongated muscle,
placed medial to, and parallel with, the preceding. It arises, from the dorsal sur-
face of the body of the ulna below the origin of the Extensor pollicis longus, and
from the interosseous membrane. Its tendon passes under the dorsal carpal
ligament in the same compartment as that which transmits the tendons of the
Extensor digitorum communis, and opposite the head of the second metacarpal
bone, joins the ulnar side of the tendon of the Extensor digitorum communis
which belongs to the index finger.
Variations. — Doubling; the ulnar part may pass beneatli the dorsal carpal ligament with the
Extensor digitorum communis; a slip from the tendon may pass to the index finger.
Nerves. — The Brachioradialis is supphed by the fifth and sixth, the Extensores carpi radialis
longus and brevis by the sixth and seventh, and the Anconeus by the seventh and eighth cervical
nerves, through the radial nerve; "the remaining muscles are innervated through the deep radial
nerve, the Supinator being supplied by the sixth, and all the other muscles by the seventh cervical.
Actions. — The muscles of the lateral and dorsal aspects of the forearm, which comprise all
the Extensor muscles and the Supinator, act upon the forearm, wrist, and hand; they are the
direct antagonists of the Pronator and Flexor muscles. The Ancona^us assists the Triceps in
extending the forearm. The BrachioradiaUs is a flexor of the elbow-joint, but only acts as such
when the movement of flexion has been initiated by the Biceps brachii and Brachialis. The
action of the Supinator is suggested by its name; it assists the Biceps in bringing the hand into
the supine position. The Extensor carpi radialis longus extends the wrist and abducts the hand.
It may also assist in bending the elbow-joint; at all events it serves to fix or steady this articula-
tion. The Extensor carpi radialis brevis extends the wrist, and may also act slightly as an abductor
of the hand. The Extensor carpi ulnaris extends the wrist, but when acting alone inclines the
hand toward the ulnar side; by its continued action it extends the elbow-joint. The Extensor
digitorum communis extends the phalanges, then the wTist, and finally the elbow. It acts prin-
cipally on the proximal phalanges, the middle and terminal phalanges being extended mainly
by the Interossei and Lumbricales. It tends to separate the fingers as it extends them. The
Extensor digiti quinti proprius extends the little finger, and by its continued action assists in
extending the wrist. It is owing to this muscle that the little finger can be extended or pointed
while the others are flexed. The chief action of the Abductor pollicis longus is to carry the thumb
laterally from the palm of the hand. By its continued action it helps to extend and abduct the
wrist. The Extensor poUicis brevis extends the proximal phalanx, and the Extensor pollicis
longus the terminal phalanx of the thumb; by their continued action they help to extend and
abduct the wrist. The Extensor indicis proprius extends the index finger, and by its continued
action assists in extending the wrist.
VI. THE MUSCLES AND FASCIA OF THE HAND.
The muscles of the hand are subdivided into three groups: (1) those of the
thumb, which occupy the radial side and produce the thenar eminence ; (2) those
of the little finger, which occupy the ulnar side and give rise to the hypothenar
eminence ; (3) those in the middle of the palm and between the metacarpal bones.
Volar Carpal Ligament {ligamentum carpi volare). — The volar carpal ligament
is the thickened band of antibrachial fascia which extends from the radius to the
ulna over the Flexor tendons as they enter the wrist.
Transverse Carpal Ligament (ligamentum carpi transversum; anterior annular
ligament) (Figs. 421, 422). — The transverse carpal ligament is a strong, fibrous
band, which arches over the carpus, converting the deep groove on the front of
the carpal bones into a tunnel, through which the Flexor tendons of the digits
and the median nerve pass. It is attached, medially, to the pisiform and the
hamulus of the hamate bone; laterallv, to the tuberositv of the navicular, and to
the medial part of the volar surface and the ridge of the greater multangular. It
is continuous, above, with the volar carpal ligament; and below, with the palmar
aponeurosis. It is crossed by the ulnar vessels and nerve, and the cutaneous
branches of the median and ulnar nerves. At its lateral end is the tendon of the
THE MUSCLES AND FASCIM OF THE HAND
457
Flexor carpi radialis, which lies in the groove on the greater multangular between
the attachments of the ligament to the bone. On its volar surface the tendons of
the Palmaris longus and Flexor carpi ulnaris are partly inserted; below, it gives
origin to the short muscles of the thumb and little finger
Median nerve
Palmaris longus
Flex. poll. long.
Flex. carp. rod.
Radial artery
Abd. poll. long.
Ext. poll brev.
Ext. carp. rad. long.
Ext. carp. rad. brev. i
Ext. poll. long.
Flexor dig. sublimis
Ulnar artery
I Ulnar nerve
Flex. carp. uln.
Flex. dig. profundus.
Ext. carp, uln.
Distal radio-ulnar artic.
Ext. indicia, prop. \ Ext. dig. quinti jnop.
Ext. dig. commun.
Fig. 421. — Transverse section across distal ends of radius and ulna.
The Mucous Sheaths of the Tendons on the Front of the Wrist. — Two sheaths envelop
the tendons as they pass beneath the transverse carpal ligament, one for the
Flexores digitorum sublimis and profundus, the other for the Flexor pollicis
longus (Fig. 423). They extend into the forearm for about 2.5 cm. above the
transverse carpal ligament, and occasionally communicate with each other under
Abd. pott, long,
Ext. poll. brev.
Median nerve Transverse carpal ligament
Flex. poll. long. \ \ Palmaris longus
Flex. dig. sublimis
Ulnar art, and nerve
Muscles of little finger
Flex, carpi rad.
Muscles of thumb
Ext. carp. rad. long.
Radial artery
Ext. carp, rad. brev.
Ext, poll, long.
Flex, dig, profundus
Ext. carp. uln.
Ext, dig. quinti prop.
Ext. dig. communis
Ext. indicis prop.
Fig, 422. — Transverse section across the wrist and digits.
the ligament. The sheath which surrounds the Flexores digitorum extends down-
ward about half-way along the metacarpal bones, where it ends in blind diverticula
around the tendons to the index, middle, and ring fingers. It is prolonged on
the tendons to the little finger and usually communicates with the mucous
458
MYOLOGY
sheath of these tendons. The sheath of the tendon of the Flexor polHcis longus
is continued along the thumb as far as the insertion of the tendon. The mucous
sheaths enveloping the terminal parts of the tendons of the Flexores digitorum
have been described on page 449.
Sheaths of terminal
parts of Flexores
digitorum
Muscles of thenar
eminence
Sheath of Flexor
pollicis longus
Sheath of Flexor carpi
radial is
Muscles of hypo-
thenar eminence
Common sheath of
Flexores digitorum
sublimis and
profundus
Flexor carpi vltuxris
\ mm \
Fig. 423. — The mucous sheaths of the tendons on the front of the wrist and digits.
Dorsal Carpal Ligament {Ugamentum carpi dorsale; posterior aftnidar ligament)
(Figs. 421, 422). — The dorsal carpal ligament is a strong, fibrous band, extending
obliquely downward and mediahvard across the back of the wrist, and consisting
of part of the deep fascia of the back of the forearm, strengthened by the addition
of some transverse fibers. It is attached, medially, to the styloid process of the ulna
THE MUSCLES AND FASCLE OF THE HAND
459
and to the triangular and pisiform bones; laterally, to the lateral margin of the
radius; and, m its passage across the wrist, to the ridges on the dorsal surface of
the radius.
Abd. poll. long.
mr
Ext. carp. rad. long.
Ext. carp. rad. brev.
Fig. 424. — The mucous sheaths of the tendons on the back of the wrist.
The Mucous Sheaths of the Tendons on the Back of the Wrist. — Between the dorsal
carpal ligament and the bones six compartments are formed for the passage of
tendons, each compartment having a separate mucous sheath. One is found in
each of the following positions (Fig. 424) : (1) on the lateral side of the styloid pro-
cess, for the tendons of the Abductor pollicis longus and Extensor pollicis brevis;
(2) behind the styloid process, for the tendons of the Extensores carpi radialis
I
460
MYOLOGY
longus and brevis; (3) about the middle of the dorsal surface of the radius, for the
tendon of the Extensor pollicis longus; (4) to the medial side of the latter, for the
tendons of the Extensor digitorum communis and Extensor indicis proprius; (5)
opposite the interval between the radius and ulna, for the Extensor digiti quinti
proprius; (6) between the head and styloid process of the ulna, for the tendon of
the Extensor carpi ulnaris. The sheaths lining these compartments extend from
above the dorsal carpal ligament; those for the tendons of Abductor pollicis longus.
Extensor brevis pollicis, Extensores carpi radialis, and Extensor carpi ulnaris
stop immediately proximal to the bases of the metacarpal bones, while the sheaths
for Extensor communis digitorum, Extensor indicis proprius, and Extensor digiti
quinti proprius are prolonged to the junction of the proximal and intermediate
thirds of the metacarpus.
Proper digital artery and nerve
Ulnar artery and nerve
Fig. 425. — The palmar aponeurosis.
Palmar Aponeurosis {aponeurosis yalmaris; 'palmar fascia) (Fig. 425). — The
palmar aponeurosis invests the muscles of the palm, and consists of central, lateral,
and medial portions.
The central portion occupies the middle of the palm, is triangular in shape, and
of great strength and thickness. Its apex is continuous with the lower margin
of the transverse carpal ligament, and receives the expanded tendon of the Pal-
THE LATERAL VOLAR MUSCLES 461
maris longus. Its base divides below into four slips, one for each finger. Each
slip gives off superficial fibers to the skin of the palm and finger, those to the palm
joinmg the skm at the furrow corresponding to the metacarpophalangeal articula-
tions, and those to the fingers passing into the skin at the transverse fold at the
bases of the fingers. The deeper part of each slip subdivides into two processes,
which are inserted into the fibrous sheaths of the Flexor tendons. From the sides
of these processes offsets are attached to the transverse metacarpal ligament.
By this arrangement short channels are formed on the front of the heads of the
metacarpal bones; through these the Flexor tendons pass. The intervals between
the four slips transmit the digital vessels and nerves, and the tendons of the Lum-
bricales. At the points of division into the slips mentioned, numerous strong,
transverse fasciculi bind the separate processes together. The central part of the
palmar aponeurosis is intimately bound to the integument by dense fibroareolar
tissue forming the superficial palmar fascia, and gives origin by its medial margin
to the Palmaris brevis. It covers the superficial volar arch, "the tendons of the
Flexor muscles, and the branches of the median and ulnar nerves; and on either
side it gives off a septum, which is continuous with the interosseous aponeurosis,
and separates the intermediate from the collateral groups of muscles.
The lateral and medial portions of the palmar aponeurosis are thin, fibrous layers,
which cover, on the radial side, the muscles of the ball of the thumb, and, on the
ulnar side, the muscles of the little finger; they are continuous with the central
portion and with the fascia on the dorsum of the hand.
The Superficial Transverse Ligament of the Fingers is a thin band of transverse
fasciculi (Fig. 425) ; it stretches across the roots of the four fingers, and is closely
attached to the skin of the clefts, and medially to the fifth metacarpal bone,
forming a sort of rudimentary web. Beneath it the digital vessels and nerves
pass to their destinations.
1. The Lateral Volar Muscles (Figs. 426, 427).
Abductor pollicis brevis. Flexor pollicis brevis.
Opponens pollicis. Adductor pollicis (obliquus).
Adductor pollicis (transversus).
The Abductor pollicis brevis {Abductor pollicis) is a thin, flat muscle, placed
immediately beneath the integument. It arises from the transverse carpal liga-
ment, the tuberosity of the navicular, and the ridge of the greater multangular,
frequently by two distinct slips. Running lateralward and downward, it is
inserted by a thin, flat tendon into the radial side of the base of the first phalanx
of the thumb and the capsule of the metacarpophalangeal articulation.
The Opponens pollicis is a small, triangular muscle, placed beneath the pre-
ceding. It arises from the ridge on the greater multangular and from the trans-
verse carpal ligament, passes downward and lateralward, and is inserted into the
whole length of the metacarpal bone of the thumb on its radial side.
The Flexor pollicis brevis consists of two portions, lateral and medial. The
lateral and more superficial portion arises from the lower border of the transverse
carpal ligament and the lower part of the ridge on the greater multangular bone;
it passes along the radial side of the tendon of the Flexor pollicis longus, and,
becoming tendinous, is inserted into the radial side of the base of the first phalanx
of the thumb; in its tendon of insertion there is a sesamoid bone. The medial
and deeper portion of the muscle is very small, and arises from the ulnar side of the
first metacarpal bone between the Adductor pollicis (obliquus) and the lateral
head of the first Interosseous dorsalis, and is inserted into the ulnar side of the base
of the first phalanx with the Adductor pollicis (obliquus). The medial part of
the Flexor brevis pollicis is sometimes described as the first Interosseous volaris.
462
MYOLOGY
The Adductor pollicis (obliquus) (Adductor obliquus pollicis) arises by several
slips from the capitate bone, the bases of the second and third metacarpals, the
intercarpal ligaments, and the sheath of the tendon of the Flexor carpi radialis.
From this origin the greater number of fibers pass obliquely downward and con-
verge to a tendon, which, uniting with the tendons of the medial portion of the
Flexor pollicis brevis and the transverse part of the Adductor, is inserted into
the ulnar side of the base of the first phalanx of the thumb, a sesamoid bone
being present in the tendon. A considerable fasciculus, however, passes more
obliquely beneath the tendon of the Flexor pollicis longus to join the lateral portion
of the Flexor brevis and the Abductor pollicis brevis.
Pisometacarpal lig.
Fig. 426. — The muscles of the thumb.
The Adductor pollicis (transversus) (Adductor tra?isversus poUich) (Fig. 426)
is the most deeply seated of this group of muscles. It is of a triangular form
arising by a broad base from the lower two-thirds of the volar surface of the
third metacarpal bone; the fibers converge, to be inserted with the medial part of
the Flexor pollicis brevis and the Adductor pollicis (obliquus) into the ulnar side
of the base of the first phalanx of the thumb.
Variations. — The Abductor pollicis brevis is often divided into an outer and an inner part;
accessory slips from the tendon of the Abductor pollicis longus or Palmaris longus, more rarely
from the Extensor carpi radialis longus, from the styloid process or Opponens pollicis or from the
skin over the thenar eminence. The deep head of the Flexor pollicis brevis may be absent or
enlarged. The two adductors vary in their relative extent and in the closeness of their connection.
The Adductor obliquus may receive a slip from the transverse metacarpal ligament.
Nerves. — The Abductor bre\TS, Opponens, and lateral head of the Flexor pollicis brevis are
supplied b}' the sixth and seventh cervical nerves through the median nerve; the medial head
of the Flexor brevis, and the Adductor, by the eighth cervical through the ulnar nerve.
Actions. — The Abductor poUicis brevis draws the thumb forward in a plane at right angles
to that of the palm of the hand. The Adductor poUicis is the opponent of this muscle, and approxi-
mates the thumb to the palm. The Opponens poUicis flexes the metacarpal bone, i. e., draws
it medialward over the palm; the Flexor poUicis brevis flexes and adducts the proximal phalanx.
2. The Medial Volar Muscles (Figs. 426, 427).
Palmaris brevis. Flexor digiti quinti brevis.
Abductor digiti quinti.
Opponens digiti quinti.
^ THE MEDIAL VOLAR MUSCLES
463
The Palmans brevis is a thin, quadrilateral muscle, placed beneath the integu-
ment ot the ulnar side of the hand. It arises by tendinous fasciculi from the
transverse carpal ligament and palmar aponeurosis; the fleshv fibers are inserted
into the skin on the ulnar border of the palm of the hand.
FiQ. 427. — The muscles of the left hand. Palmar surface.
The Abductor digiti quinti {Abductor minimi digiti) is situated on the ulnar
border of the palm of the hand. It arises from the pisiform bone and from the
tendon of the Flexor carpi ulnaris, and ends in a flat tendon, which divides into two
slips; one is inserted into the ulnar side of the base of the first phalanx of the little
finger; the other into the ulnar border of the aponeurosis of the Extensor digiti
quinti proprius.
464 MYOLOGY
The Flexor digit! quinti brevis (Flexor brevis minimi digiti) lies on the same
plane as the preceding muscle, on its radial side. It arises from the convex surface
of the hamulus of the hamate bone, and the volar surface of the transverse carpal
ligament, and is inserted into the ulnar side of the base of the first phalanx of the
little finger. It is separated from the Abductor, at its origin, by the deep branches
of the ulnar artery and nerve. This muscle is sometimes wanting; the Abductor
is then, usually, of large size.
The Opponens digiti quinti {Opponens minimi digiti) (Fig. 426) is of a tri-
angular form, and placed immediately beneath the preceding muscles. It arises
from the convexity of the hamulus of the hamate bone, and contiguous portion
of the transverse carpal ligament; it is inserted into the whole length of the meta-
carpal bone of the little finger, along its ulnar margin.
Variations. — The Palmaris brevis varies greath' in size. The Abductor digiti quinti may be
di\'ided into two or three slips or united with the Flexor digiti quinti brevis. Accessor*' head from
the tendon of the Flexor car]3i ulnaris, the transverse carpal ligament, the fascia of the forearm
or the tendon of the Palmaris longus. A portion of the muscle may insert into the metacarpal,
or separate slijis the Pisitnetacarpus, Pisiuncuiatus or the Pisiaruuilaris muscle may exist.
Nerves. — All the muscles of this group are supplied by the eighth cer\dcal nerve through the
ulnar nerve.
Actions. — The Abductor and Flexor digiti quinti brevis abduct the little finger from the ring
finger and assist in flexing the proximal phalanx. The Opponens digiti quinti draws forward
the fifth metacarpal bone, so as to deepen the hollow of the palm. The Palmaris brevis corrugates
the skin on the ulnar side of the palm.
3. The Intermediate Muscles.
Lumbricales. Interossei.
The Lumbricales (Fig. 427) are four small fleshy fasciculi, associated with the
tendons of the Flexor digitorum profundus. The first and second ari^e from the
radial sides and volar surfaces of the tendons of the index and middle fingers
respectively; the third, from the contiguous sides of the tendons of the middle and
ring fingers; and the fourth, from the contiguous sides of the tendons of the ring
and little fingers. Each passes to the radial side of the corresponding finger, and
opposite the metacarpophalangeal articulation is inserted into the tendinous
expansion of the Extensor digitorum communis covering the dorsal aspect of the
finger.
Variations. — The Lumbricales vary in number from two to five or six and there is considerable
variation in insertions.
The Interossei (Figs. 42S, 429) are so named from occupying the intervals
between the metacarpal bones, and are divided into two sets, a dorsal and a volar.
The Interossei dorsales (Dorsal interossei) are four in number, and occupy the
intervals between the metacarpal bones. They are bipenniform muscles, each arising
by two heads from the adjacent sides of the metacarpal bones, but more exten-
, sively from the metacarpal bone of the finger into which the muscle is inserted.
They are inserted into the bases of the first phalanges and into the aponeuroses
of the tendons of the Extensor digitorum communis. Between the double origin
of each of these muscles is a narrow triangular interval ; through the first of these
the radial artery passes; through each of the other three a perforating branch from
the deep volar arch is transmitted.
The first or Abductor indicis is larger than the others. It is fiat, triangular in
form, and arises by two heads, separated by a fibrous arch for the passage of the
radial artery from the dorsum to the palm of the hand. The lateral head arises
from the proximal half of the ulnar border of the first metacarpal bone; the medial
head, from almost the entire length of the radial border of the second metacarpal
bone; the tendon is inserted into the radial side of the index finger. The second
THE MUSCLES AND FASCIA OF THE LOWER EXTREMITY 465
and third are inserted into the middle finger, the former into its radial, the latter
into its ulnar side. The fourth is inserted into the ulnar side of the ring finger.
The Interossei volares {Palmar interossei), three in number, are smaller than the
Interossei dorsales, and placed upon the volar surfaces of the metacarpal bones,
rather than between them. Each arises from the entire length of the metacarpal
bone of one finger, and is inserted into the side of the base of the first phalanx and
aponeurotic expansion of the Extensor communis tendon to the same finger.
The first arises from the ulnar side of the second metacarpal bone, and is inserted
into the same side of the first phalanx of the index finger. The second arises from
the radial side of the fourth metacarpal bone, and is inserted into the same side
of the ring finger. The third arises from the radial side of the fifth metacarpal
bone, and is inserted into the same side of the little finger. From this account
it may be seen that each finger is provided with two Interossei, with the exception
of the little finger, in which the Abductor takes the place of one of the pair.
As already mentioned (p. 461), the medial head of the Flexor pollicis brevis is
sometimes described as the toterosseus volaris primus.
Fig. 428. — The Interossei dorsales of left hand.
Fig. 429. — The Interossei volares of left hand.
Nerves. — The two lateral Lumbricales are supplied by the sixth and seventh cervical nerves,
through the third and fourth digital branches of the median nerve; the two medial Lumbricales
and aU the Interossei are supphed by the eighth cervical nerve, through the deep palmar branch
of the ulnar nerve. The third Lumbricahs frequently receives a twig from the median.
Actions. — The Interossei volares adduct the fingers to an imaginary hne drawn longitudinally
through the center of the middle finger; and the Interossei dorsales abduct the fingers from that
line. In addition to this the Interossei, in conjimction with the Lumbricales, flex the first
phalanges at the metacarpophalangeal joints, and extend the second and third phalanges in
consequence of their insertions into the expansions of the Extensor tendons. The Extensor
digitorum communis is beUeved to act almost entirely on the first phalanges.
THE MUSCLES AND FASCLflii OF THE LOWER EXTREMITY.
The muscles of the lower extremity are subdivided into groups corresponding
with the different regions of the limb.
I. Muscles of the Iliac Region.
II.
Muscles of the Thigh.
III. Muscles of the Leg.
IV. Muscles of the Foot.
30
466
MYOLOGY
V^^tl"
"W
'■rn
Sap.'
Mm
w^-
//.^^
-\i
^^
nec\T u s\
F E m\o R I ;
J J'
fc.\1
itelli
V
FiQ. 430. — Muscles of the iliac and anterior
• femoral regions.
I. THE MUSCLES AND FASCLffi OF THE
ILIAC REGION (Fig. 430).
Psoas major. Psoas minor. Iliacus.
The Fascia Covering the Psoas and Iliacus is
thin above, and becomes gradually thicker
below as it approaches the inguinal ligament.
The portion covering the Psoas is thickened
above to form the medial lumbocostal arch,
which stretches from the transverse process of
the first lumbar vertebra to the bodv of the
second. Medially, it is attached by a series of
arched processes to the intervertebral fibro-
cartilages, and prominent margins of the bodies
of the vertebrge, and to the upper part of the
sacrum; the intervals left, opposite the con-
stricted portions of the bodies, transmit the
lumbar arteries and veins and filaments of the
sympathetic trunk. Laterally, above the crest
of the ilium, it is continuous with the fascia
covering the front of the Quadratus lumborum
(see page 419), while below the crest of the
ilium it is continuous with the fascia covering
the Iliacus.
The portions investing the Iliacus [fascia iliaca;
iliac fascia) is connected, laterally to the whole
length of the inner lip of the iliac crest; and
medially, to the linea terminalis of the lesser
pelvis, where it is continuous with the peri-
osteum. At the iliopectineal eminence it re-
ceives the tendon of insertion of the Psoas
minor, when that muscle exists. Lateral to the
femoral vessels it is intimately connected to
the posterior margin of the inguinal ligament,
and is continuous with the transversalis fascia.
Immediatelv lateral to the femoral vessels the
iliac fascia is prolonged backward and medial-
ward from the inguinal ligament as a band,
the iliopectineal fascia, which is attached to
the iliopectineal eminence. This fascia divides
the space between the inguinal ligament and
the hip bone into two lacunae or compart-
ments, the medial of which transmits the
femoral vessels, the lateral the Psoas major
and Iliacus and the femoral nerve. Medial
to the vessels the iliac fascia is attached to
the pectineal line behind the inguinal apo-
neurotic falx, where it is again continuous with
the transversalis fascia. On the thigh the
fasciae of the Iliacus and Psoas form a single
sheet termed the iliopectineal fascia, ^^^le^e
the external iliac vessels pass into the thigh, the
fascia descends behind them, forming the pos-
terior wall of the femoral sheath. The portion
of the iliopectineal fascia which passes behind
THE ANTERIOR FEMORAL MUSCLES 4G7
the femoral vessels is also attached to the pectineal line beyond the limits of the
attachment of the inguinal aponeurotic falx; at this part it is continuous with
the pectineal fascia. The external iliac vessels lie in front of the iliac fascia, but
all the branches of the lumbar plexus are behind it; it is separated from the peri-
toneum by a quantity of loose areolar tissue.
The Psoas major (Psoas magniis) (Fig. 430) is a long fusiform muscle placed on
the side of the lumbar region of the vertebral column and brim of the lesser pelvis.
It arises (1) from the anterior surfaces of the bases and lower borders of the transverse
processes of all the lumbar vertebrae; (2) from the sides of the bodies and the corre-
sponding intervertebral iibrocartilages of the last thoracic and all the lumbar verte-
bra? by five slips, each of which is attached to the adjacent upper and lower margins
of two vertebra?, and to the intervertebral fibrocartilage; (3) from a series of
tendinous arches which extend across the constricted parts of the bodies of the
lumbar vertebra? between the previous slips; the lumbar arteries and veins, and
filaments from the sympathetic trunk pass beneath these tendinous arches. The
muscle proceeds downward across the brim of the lesser pelvis, and diminishing
gradually in size, passes beneath the inguinal ligament and in front of the capsule
of the hip-joint and ends in a tendon; the tendon receiAes nearly the whole of
the fibers of the Iliacus and is inserted into the lesser trochanter of the femur.
A large bursa which may communicate with the cavity of the hip-joint, separates
the tendon from the pubis and the capsule of the joint.
The Psoas minor (Psoas parvus) is a long slender muscle, placed in front of the
Psoas major. It arises from the sides of the bodies of the twelfth thoracic and first
lumbar vertebrae and from the fibrocartilage between them. It ends in a long
flat tendon which is inserted into the pectineal line and iliopectineal eminence,
and, by its lateral border, into the iliac fascia. This muscle is often absent.
The Iliacus is a flat, triangular muscle, which fills the iliac fossa. It arises from
the upper two-thirds of this fossa, and from the inner lip of the iliac crest; behind,
from the anterior sacroiliac and the iliolumbar ligaments, and base of the sacrum;
in front, it reaches as far as the anterior superior and anterior inferior iliac spines,
and the notch between them. The fibers converge to be inserted into the lateral
side of the tendon of the Psoas major, some of them being prolonged on to the body
of the femur for about 2.5 cm. below and in front of the lesser trochanter.^
Variations. — The Iliacus minor or Iliocapsularis, a small detached part of the Iliacus is frequently
present. It arises from the anterior inferior spine of the ilium and is inserted into the lower part
of the intertrochanteric line of the femur or into the iliofemoral ligament.
Nerves. — The Psoas major is suppUed by branches of the second and third lumbar nerve;
the Psoas minor by a branch of the first lumbar nerve; and the Iliacus by branches of the second
and third lumbar nerves through the femoral nerve.
Actions. — The Psoas major, acting from above, flexes the thigh upon the pelvis, being assisted
by the Ihacus; acting from below, with the femur fixed, it bends the lumbar portion of the verte-
bral column forward and to its own side, and then, in conjunction with the Iliacus, tilts the pelvis
forward. When the muscles of both sides are acting from below, they serve to maintain the
erect posture by supporting the vertebral column and pelvis upon the femora, or in continued
action bend the trunk and pelvis forward, as in raising the trunk from the recumbent posture.
The Psoas minor is a tensor of the iliac fascia.
II. THE MUSCLES AND FASCI-S; OF THE THIGH.
1. The Anterior Femoral Muscles (Fig. 430).
Rectus femoris.
^ , . Quadriceps
Vastus lateralis.
Vastus medialis.
Vastus intermedius.
Articularis genu.
1 The Psoas major and iliacus are sometimes regarded as a single muscle named the Iliopsoas.
468 MYOLOGY
Superficial Fascia.^ — The superficial fascia forms a continuous layer over the whole
of the thigh ; it consists of areolar tissue containing in its meshes much fat, and may
be separated into two or more layers, between which are found the superficial
vessels and nerves. It varies in thickness in different parts of the limb; in the groin
it is thick, and the two layers are separated from one another by the superficial
inguinal lymph glands, the great saphenous vein, and several smaller vessels.
The superficial layer is continuous above with the superficial fascia of the abdomen.
The deep layer of the superficial fascia is a very thin, fibrous stratum, best marked
on the medial side of the great saphenous vein and below the inguinal ligament.
It is placed beneath the subcutaneous vessels and nerves and upon the surface of the
fascia lata. It is intimately adherent to the fascia lata a little below the inguinal
ligament. It covers the fossa ovalis {saphenous opening), being closely united to
its circumference, and is connected to the sheath of the femoral vessels. The
portion of fascia covering this fossa is perforated by the great saphenous vein and
by numerous blood and lymphatic vessels, hence it has been termed the fascia
cribrosa, the openings for these vessels having been likened to the holes in a sieve.
A large subcutaneous bursa is found in the superficial fascia over the patella.
Deep Fascia.- — The deep fascia of the thigh is named, from its great extent,
the fascia lata; it constitutes an inyestment for the whole of this region of the limb,
but varies in thickness in diff"erent parts. Thus, it is thicker in the upper and lateral
part of the thigh, where it receives a fibrous expansion from the Glutseus maximus,
and where the Tensor fascite latte is inserted between its layers; it is very thin
behind and at the upper and medial part, where it covers the Adductor muscles,
and again becomes stronger around the knee, receiving fibrous expansions from the
tendon of the Biceps femoris laterally, from the Sartorius medially, and from the
Quadriceps femoris in front. The fascia lata is attached, above and behind, to the
back of the sacrum and coccyx; laterally, to the iliac crest; in front, to the inguinal
ligament, and to the superior ramus of the pubis; and medially, to the inferior
ramus of the pubis, to the inferior ramus and tuberosity of the ischium, and to
the lower border of the sacrotuberous ligament. From its attachment to the iliac
crest it passes down over the Gluta^us medius to the upper border of the Glutseus
maximus, where it splits into two layers, one passing superficial to and the other
beneath this muscle; at the lower border of the muscle the two layers reunite.
Laterally, the fascia lata receives the greater part of the tendon of insertion of
the Gluta?us maximus, and becomes proportionately thickened. The portion of
the fascia lata attached to the front part of the iliac crest, and corresponding to
the origin of the Tensor fasciae latje, extends down the lateral side of the thigh as
two layers, one superficial to and the other beneath this muscle ; at the lower end
of the muscle these two layers unite and form a strong band, having first received
the insertion of the muscle. This band is continued downward, under the name
of the iliotibial band {tradus iliotibialis) and is attached to the lateral condyle of
the tibia. The part of the iliotibial band which lies beneath the Tensor fascise
latse is prolonged upward to join the lateral part of the capsule of the hip-joint.
Below, the fascise lata is attached to all the prominent points around the knee-
joint, viz., the condyles of the femur and tibia, and the head of the fibula. On
either side of the patella it is strengthened by transverse fibers from the lower parts
of the Vasti, which are attached to and support this bone. Of these the lateral
are the stronger, and are continuous with the iliotibial band. The deep surface
of the fascia lata gives off two strong intermuscular septa, which are attached
to the whole length of the linea aspera and its prolongations above and below;
the lateral and stronger one, which extends from the insertion of the Glutseus
maximus to the lateral condyle, separates the Vastus lateralis in front from the
short head of the Biceps femoris behind, and gives partial origin to these mus-
cles; the medial and thinner one separates the Vastus medialis from the Adduc-
THE ANTERIOR FEMORAL MUSCLES
469
tores and Pectineiis. Besides these there are numerous smaller septa, separating
the individual muscles, and enclosing each in a distinct sheath.
The Fossa Ovalis (saphenous opening) (Fig. 4.31).— At the upper and medial
part of the thigh, a little below the medial end of the inguinal ligament, is a large
oval-shaped aperture in the fascia lata; it transmits the great saphenous vein,
and other, smaller vessels, and is termed the fossa ovaUs. The fascia cribrosa,
which is pierced by the structures passing through the opening, closes the aperture
and must be removed to expose it. The fascia lata in this part of the thigh is
described as consisting of a superficial and a deep portion.
Fig. 431. — The fossa ovalis.
The superficial portion of the fascia lata is the part on the lateral side of the fossa
ovalis. It is attached, laterally, to the crest and anterior superior spine of the ilium,
to the whole length of the inguinal ligament, and to the pectineal line in con-
junction with the lacunar ligament. From the tubercle of the pubis it is reflected
downward and lateralward, as an arched margin, the falciform margin, forming
the lateral boundary of the fossa ovalis; this margin overlies and is adherent to the
anterior layer of the sheath of the femoral vessels : to its edge is attached the fascia
cribrosa. The upward and medial prolongation of the falciform margin is named
the superior comu; its downward and medial prolongation, the inferior comu. The
latter is well-defined, and is continuous behind the great saphenous vein with the
pectineal fascia^
The deep portion is situated on the medial side of the fossa ovalis, and at the
lower margin of the fossa is continuous with the superficial portion; traced upward.
470 MYOLOGY
it covers the Pectineus, Adductor longus, and Gracilis, and, passing behind the
sheath of the femoral vessels, to which it is closely united^ is continuous with the
iliopectineal fascia, and is attached to the pectineal line.
From this description it may be observed that the superficial portion of the
fascia lata lies in front of the femoral vessels, and the deep portion behind them,
so that an apparent aperture exists between the two, through which the great
saphenous passes to join the femoral vein.
The Sartorius, the longest muscle in the body, is narrow and ribbon-like; it
arises by tendinous fibers from the anterior superior iliac spine and the upper half
of the notch below it. It passes obliquely across the upper and anterior part of
the thigh, from the lateral to the medial side of the limb, then descends vertically,
as far as the medial side of the knee, passing behind the medial condyle of the femur
to end in a tendon. This curves obliquely forward and expands into a broad apon-
eurosis, which is inserted, in front of the Gracilis and Semitendinous, into the upper
part of the medial surface of the body of the tibia, nearly as far forward as the
anterior crest. The upper part of the aponeurosis is curved backward over the
upper edge of the tendon of the Gracilis so as to be inserted behind it. An offset,
from its upper margin, blends with the capsule of the knee-joint, and another
from its lower border, with the fascia on the medial side of the leg.
Variations. — Slips of origin from the outer end of the inguinal ligament, the notch of the ilium,
the ilio-pectineal line or the pubis occur. The muscle may be split into two parts, and one part
may be inserted into the fascia lata, the femur, the ligament of the patella or the tendon of the
Semitendinosus. The tendon of insertion may end in the fascia lata, the capsule of the knee-
joint, or the fascia of the leg. The muscle may be absent.
The Quadriceps femoris {Quadriceps extetisor) includes the four remaining
muscles on the front of the thigh. It is the great extensor muscle of the leg, forming
a large fleshy mass which covers the front and sides of the femur. It is subdivided
into separate portions, which have received distinctive names. One occupying
the middle of the thigh, and connected above with the ilium, is called from its
straight course the Rectus femoris. The other three lie in immediate connection
with the body of the femur, which they cover from the trochanters to the condyles.
The portion on the lateral side of the femur is termed the Vastus lateralis; that
covering the medial side, the Vastus medialis; and that in front, the Vastus
intermedius.
The Rectus femoris is situated in the middle of the front of the thigh; it is fusi-
form in shape, and its superficial fibers are arranged in a bipenniform manner,
the deep fibers running straight down to the deep aponeurosis. It arises by two
tendons: one, the anterior or straight, from the anterior inferior iliac spine; the
other, the posterior or reflected, fro.m a groove above the brim of the acetabulum.
The two unite at an acute angle, and spread into an aponeurosis which is prolonged
downward on the anterior surface of the muscle, and from this the muscular fibers
arise. The muscle ends in a broad and thick aponeurosis which occupies the lower
two-thirds of its posterior surface, and, gradually becoming narrowed into a flat-
tened tendon, is inserted into the base of the patella.
The Vastus lateralis {Vastus externus) is the largest part of the Quadriceps
femoris. It arises by a broad aponeurosis, which is attached to the upper part of
the intertrochanteric line, to the anterior and inferior borders of the greater tro-
chanter, to the lateral lip of the gluteal tuberosity, and to the upper half of the
lateral lip of the linea aspera; this aponeurosis covers the upper three-fourths of
the muscle, and from its deep surface many fibers take origin. A few additional
fibers arise from the tendon of the Glutjeus maximus, and from the lateral inter-
muscular septum between the Vastus lateralis and short head of the Biceps femoris.
The fibers form a large fleshy mass, which is attached to a strong aponeurosis,
placed on the deep surface of the lower part of the muscle: this aponeurosis becomes
THE MEDIAL FEMORAL MUSCLES 471
contracted and thickened into a flat tendon inserted into the lateral border of the
patella, blending with the Quadriceps femoris tendon, and giving an expansion to
the capsule of the knee-joint.
The Vastus medialis and Vastus intermedins appear to be inseparably united,
but when the Rectus femoris has been reflected a narrow interval will be observed
extending upward from the medial border of the patella between the two muscles,
and the separation may be continued as far as the lower part of the intertrochan-
teric line, where, however, the two muscles are frequently continuous.
The Vastus medialis (Vastus internus) arises from the lower half of the inter-
trochanteric line, the medial lip of the linea aspera, the upper part of the medial
supracondylar line, the tendons of the Adductor longus and the Adductor magnus
and the medial intermuscular septum. Its fibers are directed downward and for-
ward, and are chiefly attached to an aponeurosis which lies on the deep surface
of the muscle and is inserted into the medial border of the patella and the Quad-
riceps femoris tendon, an expansion being sent to the capsule of the knee-joint.
The Vastus intermedius (Crureus) arises from the front and lateral surfaces of the
body of the femur in its upper two-thirds and from the lower part of the lateral
intermuscular septum. Its fibers end in a superficial aponeurosis, which forms
the deep part of the Quadriceps femoris tendon.
The tendons of the different portions of the Quadriceps unite at the lower part of the thigh,
so as to form a single strong tendon, which is inserted into the base of the patella, some few fibers
passing over it to blend with the ligamentum patellae. More properly, the patella may be regarded
as a sesamoid bone, developed in the tendon of the Quadriceps; and the hgamentum patellae,
which is continued from the apex of the patella to the tuberosity of the tibia, as the proper tendon
of insertion of the muscle, the medial and lateral patellar retinacula (see p. 338) being expan-
sions from its borders. A bursa, which usually communicates with the cavity of the knee-joint,
is situated between the femur and the portion of the Quadriceps tendon above the patella; another
is interposed between the tendon and the upper part of the front of the tibia; and a third, the
prepatellar bursa, is placed over the patella itself.
The Articularis genu (Subcrureus) is a small muscle, usually distinct from the
Vastus intermedius, but occasionally blended with it; it arises from the anterior
surface of the lower part of the body of the femur, and is inserted into the upper
parfe of the synovial membrane of the knee-joint. It sometimes consists of several
separate muscular bundles.
Nerves. — The muscles of this region are supplied by the second, third, and fourth lumbar
nerves, through the femoral nerve.
Actions. — The Sartorius flexes the leg upon the thigh, and, continuing to act, flexes the thigh
upon the pelvis; it next abducts and rotates the thigh outward. When the knee is bent, the
Sartorius assists the Semitendinosus, Semimembranosus, and Popliteus in rotating the tibia inward.
Taking its fixed point from the leg, it flexes the pelvis upon the thigh, and, if one muscle acts, assists
in rotating the pelvis. The Quadriceps femoris extends the leg upon the thigh. The Rectus
femoris assists the Psoas major and lliacus in supporting the pelvis and trunk upon the femur.
It also assists in flexing the thigh on the pelvis, or if the thigh be fixed it will flex the pelvis. The
Vastus mediaUs draws the pateUa medialward as well as upward.
2. The Medial Femoral Muscles.
Gracilis. Adductor longus. Adductor magnus.
Pectineus. Adductor brevis.
The Gracilis (Fig. 430) is the most superficial muscle on the medial side of the
thigh. It is thin and flattened, broad above, narrow and tapering below. It
arises by a thin aponeurosis from the anterior margins of the lower half of the
symphysis pubis and the upper half of the pubic arch. The fibers run vertically
downward, and end in a rounded tendon, which passes behind the medial condyle
of the femur, curves around the medial condyle of the tibia, where it becomes flat-
472
MYOLOGY
tened, and is inserted into the upper part of the medial surface of the body of the
tibia, below the condyle. A few of the fibers of the lower part of the tendon are
prolonged into the deep fascia of the leg. At its insertion the tendon is situated
immediately above that of the Semitendinosus, and its upper edge is overlapped
by the tendon of the Sartorius, with which it is in part blended. It is separated
from the tibial collateral ligament of the knee-joint, by a bursa common to it and
the tendon of the Semitendinosus.
Rectus femoris M.
Femur
Deep femoral artery
and vein
Vastus intermedin
M.:
Linea aspen i
Sartorius M.
Vastus lateralis M.
InterTnuscular septuin
of lateral femoral
Femoral vein
and artery
Intermediate
cutaneous
ngrve
^ S Great saphenous
^^ ■!{) ^ ' vein
..^Adductor
longus M.
'-Gracilis M.
'^■.Intermuscular
„ . ' septum of
i // ■ 4 '/ median femoral
^ •^^Perforating artery
and vein
SemimembranosusM .
Biceps femoris M.
[caput hrexe]
Biceps femoris M.
[caput longu7H]
^•Semitendinosus M.
Posterior femoral
cutaneous nerve
Adductor magnus M.
Fig. 432. — Cross-section through the middle of tlie thigh. (Eycleshymer and Schoemaker.)
The Pectineus (Fig. 43(^) is a flat, quadrangular muscle, situated at the anterior
part of the upper and medial aspect of the thigh. It arises from the pectineal line,
and to a slight extent from the surface of bone in front of it, between the
iliopectineal eminence and tubercle of the pubis, and from the fascia covering the
anterior surface of the muscle; the fibers pass downward, backward, and lateral-
ward, to be inserted into a rough line leading from the lesser trochanter to the
linea aspera.
The Adductor longus (Fig. 433), the most superficial of the three Adductores,
is a triangular muscle, lying in the same plane as the Pectineus. It arises by a
flat, narrow tendon, from the front of the pubis, at the angle of junction of the crest
THE MEDIAL FEMORAL MUSCLES
473
with the symphysis; and soon expands into a broad fleshy belly. This passes
downward, backward, and lateralward, and is inserted, by an aponeurosis, into the
linea aspera, between the Vastus medialis and the Adductor magnus, with both
of which it is usually blended.
The Adductor brevis (Fig. 433) is situ-
ated immediately behind the two preceding
muscles. It is somewhat triangular in form,
and arises by a narrow origin from the
outer surfaces of the superior and inferior
rami of the pubis, between the Gracilis
and Obturator externus. Its fibers, passing
backward, lateralward, and downward, are
inserted, by an aponeurosis, into the line
leading from the lesser trochanter to the
linea aspera and into the upper part of the
linea aspera, immediately behind the Pectin-
eus and upper part of the Adductor longus.
The Adductor magnus (Fig. 433) is a large
triangular muscle, situated on the medial side
of the thigh. It arises from a small part
of the inferior ramus of the pubis, from the
inferior ramus of the ischium, and from the
outer margin of the inferior part of the
tuberosity of the ischium. Those fibers
which arise from the ramus of the pubis are
short, horizontal in direction, and are inserted
into the rough line leading from the greater
trochanter to the linea aspera, medial to the
Gluta^us maximus ; those from the ramus of
the ischium are directed downward and lat-
eralward with different degrees of obliquity,
to be ijiserted, by means of a broad aponeu-
rosis, into the linea aspera and the upper
part of its medial prolongation below. The
medial portion of the muscle, composed
principally of the fibers arising from the
tuberosity of the ischium, forms a thick
fleshy mass consisting of coarse bundles
which descend almost vertically, and end
about the lower third of the thigh in a
rounded tendon which is inserted into the
adductor tubercle on the medial condyle of
the femur, and is connected by a fibrous
expansion to the line leading upward from
the tubercle to the linea aspera. At the
insertion of Ae muscle, there is a series of
osseoaponeurotic openings, formed by tendi-
nous arches attached to the bone. The
upper four openings are small, and give
passage to the perforating branches of the
profunda femoris artery. The lowest is of
large size, and transmits the femoral vessels
to the popliteal fossa.
Fig. 433.
-Deep muscles of the medial femoral
region.
474 MYOLOGY
Variations. — The Pectineus is sometimes divided into an outer part supplied by the femoral
nerve and an inner part supphed by the obturator nerve. The muscle may be attached to or
inserted into the capsule of the hip-joint. The Adductor longus may be double, may extend to the
knee, or be more or less united with the Pectineus. The Adductor breris may be divided into two
or three parts, or it maj' be united to the Adductor magnus. The Adductor 7nagnus may be more
or less segmented, the anterior and superior portion is often described as a separate muscle, the
Adductor minwius. The muscle may be fused with the Quadratus femoris.
Nerves. — The three Adductores and the Gracilis are supplied by the third and fourth lumbar
nerves through the obturator nerve; the Adductor magnus receiving an additional branch from
the sacral plexus through the sciatic. The Pectineus is supplied by the second, thu"d, and fourth
lumbar nerves through the femoral nerve, and by the third lumbar through the accessory obturator
when this latter exists. Occasionally it receives a branch from the obturator nerve.^
Actions. — The Pectineus and three Adductores adduct the thigh powerfully; they are especially
used in horse exercise, the sides of the saddle being grasped between the knees by the contraction
of these muscles. In consequence of the obhquity of their insertions into the linea aspera, thej-
rotate the thigh outward, assisting the external Rotators, and when the hmb has been abducted,
they draw it medialward, carrying the thigh across that of the opposite side. The Pectineus
and Adductores brevis and longus assist the Psoas major and Ihacus in flexing the thigh upon
the pelvis. In progression, all these muscles assist in drawing forward the lower limb. The
Gracilis assists the Sartorius in flexing the leg and rotating it inward; it is also an adductor of the
thigh. If the lower extremities be fixed, these muscles, taking their fixed points below, maj- act
upon the pelvis, serving to maintain the body in an erect posture; or, if their action be continued,
flex the pelvis forward upon the femur.
3. The Muscles of the Gluteal Region (Fig. 434).
Glutreus maximus. Obturator internus.
Gkitt^iis medius. Gemellus superior.
Gluttvus minimus. Gemellus inferior.
Tensor fasciae latae. Quadratus femoris.
Piriformis. Obturator externus.
The Glutseus maximus, the most superficial muscle in the gluteal region, is a
broad and thick fleshy mass of a quadrilateral shape, and forms the prominence
of the nates. Its large size is one of the most characteristic features of the muscular
system in man, connected as it is with the power he has of maintaining the trunk
in the erect posture. The muscle is remarkably coarse in structure, being made
up of fasciculi lying parallel with one another and collected together into large
bundles separated by fibrous septa. It arises from the posterior gluteal line of
the ilium, and the rough portion of bone including the crest, immediately above
and behind it; from the posterior surface of the lower part of the sacrum and the
side of the coccyx; from the aponeurosis of the Sacrospinalis, the sacrotuberous
ligament, and the fascia (gluteal aponeurosis) covering the Glutivus medius.
The fibers are directed obliqtiely downward and lateralward; those forming the
upper and larger portion of the muscle, together with the superficial fibers of the
lower portion, end in a thick tendinous lamina, which passes across the greater
trochanter, and is inserted into the iliotibial band of the fascia lata; the deeper
fibers of the lower portion of the muscle are inserted into the gluteal tuberosity
between the Vastus lateralis and Adductor magnus.
Bursae. — Three bursae are usuallj' found in relation with the deep surface of this muscle. One
of these, of large size, and generally multilocular, separates it from the greater trochanter; a
second, often wanting, is situated on the tuberosity of the ischium; a thii'd is found between
the tendon of the muscle and that of the Vastus laterahs.
The Glutseus medius is a broad, thick, radiating muscle, situated on the outer
surface of the pelvis. Its posterior third is covered by the Glutteus maximus, its
' The Pectineus may consist of two incompletely separated strata; the lateral or dorsal stratum, which is constant,
is supplied by a branch from the femoral nerve, or in the absence of this branch by the accessor^" obturator ner\'e;
the medial or ventral stratum, when present, is supplied by the obturator nerve. — A. ^I. Paterson. Journal of Anatomy
and Physiology, xxvi, 43.
THE MUSCLES OF THE GLUTEAL REGION
475
anterior two-thirds by the gluteal
aponeurosis, which separates it
from the superficial fascia and
integument. It arises from the
outer surface of the ilium between
the iliac crest and posterior glu-
teal line above, and the anterior
gluteal line below; it also arises
from the gluteal aponeurosis
covering its outer surface. The
fibers con\erge to a strong flat-
tened tendon, which is inserted
into the oblique ridge which runs
downward and forward on the
lateral surface of the greater tro-
chanter. A bursa separates the
tendon of the muscle from the
surface of the trochanter over
which it glides.
Variations. — The posterior border
may be more or less closely imited to
the Piriformis, or some of the fibers end
on its tendon.
The Glutaeus minimus, the small-
est of the three Gluttiei, is placed
immediately beneath the preced-
ing. It is fan-shaped, arising from
the outer surface of the iliimi,
between the anterior and inferior
gluteal lines, and behind, from
the margin of the greater sciatic
notch. The fibers converge to
the deep surface of a radiated
aponeurosis, and this ends in a
tendon which is inserted into an
impression on the anterior border
of the greater trochanter, and
gives an expansion to the capsule
of the hip-joint. A bursa is
interposed between the tendon
and the greater trochanter. Be-
tween the Gluttieus medius and
Glut;>^us minimus are the deep
branches of the superior gluteal
vessels and the superior gluteal
nerve. The deep surface of the
Gluta?us minimus is in relation
with the reflected tendon of the
Rectus femoris and the capsule
of the hip-joint.
Variations. — The muscle niay be di-
■^nded into an anterior and a posterior
part, or it may send slips to the Piri-
formis, the Gemellas superior or the
outer part of the origin of the Vastus
lateralis.
Medial
hamstring
, tendons
Sartor ius -
Gracilis
Semitendinosus
Semi-
inembraivosus
Lateral
Jmmsiring
tendon
Biceps
femoris
FiQ. 434 — Muscles of the gluteal and posterior femoral regions.
476
MYOLOGY
The Tensor fasciae latae {Tensor fascicr femoris) arises from the anterior part
of the outer lip of the iliac crest; from the outer surface of the anterior superior
iliac spine, and part of the outer border of the notch below it, between the Glutfeus
medius and Sartorius; and from the deep surface of the fascia lata. It is inserted
between the two layers of the iliotibial band of the fascia lata about the junction
of the middle and upper thirds of the thigh.
The Piriformis is a flat muscle, pyramidal in shape, lying almost parallel with
the posterior margin of the Glutseus medius. It is situated partly within the pelvis
against its posterior wall, and partly at the back of the hip-joint. It arises from
the front of the sacrum by three fleshy digitations, attached to the portions of
bone between the first, second, third, and fourth anterior sacral foramina, and to
the grooves leading from the foramina : a few fibers also arise from the margin of
the greater sciatic foramen, and from the anterior surface of the sacrotuberous
ligament. The muscle passes out of the pelvis through the greater sciatic fora-
men, the upper part of which it fills, and is inserted by a rounded tendon into
the upper border of the greater trochanter behind, but often partly blended with,
the common tendon of the Obturator internus and Gemelli.
Variations. — It is frequently pierced by the common peroneal nerve and thus divided more or
less into two parts. It may be imited with the Gluteus medius, or send fibers to the Glutseus
minimus or receive fibers from the Gemellus superior. It may have only one or two sacral attach-
ments or be inserted in to the capsule of the hip-joint. It may be absent.
Ant. sup. iliac spine.'
Symphysis
pubis
Transveme acetabular
ligament
Fig. 435. — The obturator iiieinbrane.
Obturator Membrane (Fig. 435). — The obturator membrane is a thin fibrous sheet,
which almost completely closes the obturator foramen. Its fibers are arranged
in interlacing bundles mainly transverse in direction; the uppermost bundle is
attached to the obturator tubercles and completes the obturator canal for the pas-
sage of the obturator vessels and nerve. The membrane is attached to the sharp
margin of the obturator foramen except at its lower lateral angle, where it is fixed
THE MUSCLES OF THE GLUTEAL REGION 477
to the pelvic surface of the inferior ramus of the ischium, i. e., within the margin.
Both obturator muscles are connected with this membrane.
The Obturator internus is situated partly within the lesser pelvis, and partly
at the back of the hip-joint. It arises from the inner surface of the antero-lateral
wall of the pelvis, where it surrounds the greater part of the obturator foramen,
being attached to the inferior rami of the pubis and ischium, and at the side to the
inner surface of the hip bone below and behind the pelvic brim, reaching from the
upper part of the greater sciatic foramen above and behind to the obturator fora-
men below and in front. It also arises from the pelvic surface of the obturator
membrane except in the posterior part, from the tendinous arch which completes the
canal for the passage of the obturator vessels and nerve, and to a slight extent from
the obturator fascia, which covers the muscle. The fibers converge rapidly toward
the lesser sciatic foramen, and end in four or five tendinous bands, which are found
on the deep surface of the muscle; these bands are reflected at a right angle over
the grooved surface of the ischium between its spine and tuberosity. This bony
surface is covered by smooth cartilage, which is separated from the tendon by a
bursa, and presents one or more ridges corresponding with the furrows between
the tendinous bands. These bands leave the pelvis through the lesser sciatic fora-
men and unite into a single flattened tendon, which passes horizontally across the
capsule of the hip-joint, and, after receiving the attachments of the Gemelli, is
inserted into the forepart of the medial surface of the greater trochanter above
the trochanteric fossa. A bursa, narrow and elongated in form, is usually found
between the tendon and the capsule of the hip-joint; it occasionally communicates
with the bursa between the tendon and the ischium.
The Gemelli are two small muscular fasciculi, accessories to the tendon of the
Obturator internus which is received into a groove between them.
The Gemellus superior, the smaller of the two, arises from the outer surface of
the spine of the ischium, blends with the upper- part of the tendon of the Obturator
internus, and is inserted with it into the medial surface of the greater trochanter.
It is sometimes wanting.
The Gemellus inferior arises from the upper part of the tuberosity of the ischium,
immediately below the groove for the Obturator internus tendon. It blends with
the lower part of the tendon of the Obturator internus, and is inserted with it
it into the medial surface of the greater trochanter. Rarely absent.
The Quadratus femoris is a flat, c{uadrilateral muscle, between the Gemellus
inferior and the upper margin of the Adductor magnus; it is separated from the
latter by the terminal branches of the medial femoral circumflex vessels. It arises
from the upper part of the external border of the tuberosity of the ischium, and is
inserted into the upper part of the linea quadrata — that is, the line which extends
vertically downward from the intertrochanteric crest. A bursa is often found
between the front of this muscle and the lesser trochanter. Sometimes absent.
The Obturator externus (Fig. 436) is a flat, triangular muscle, which covers
the outer surface of the anterior wall of the pelvis. It arises from the margin
of bone immediately around the medial side of the obturator foramen, viz., from
the rami of the pubis, and the inferior ramus of the ischium; it also arises from the
medial two-thirds of the outer surface of the obturator membrane, and from the
tendinous arch which completes the canal for the passage of the obturator vessels
and nerves. The fibers springing from the pubic arch extend on to the inner sur-
face of the bone, where they obtain a narrow origin between the margin of the
foramen and the attachment of the obturator membrane. The fibers converge
and pass backward, lateralward, and upward, and end in a tendon which runs
across the back of the neck of the femur and lower part of the capsule of the hip-
joint and is inserted into the trochanteric fossa of the femur. The obturator vessels
lie between the muscle and the obturator membrane; the anterior branch of the
478
MYOLOGY
obturator nerve reaches the thigh by passing in front of the muscle, and the
posterior branch by piercing it.
Nerves. — The Glutaeus maximus is supplied by the fifth lumbar and first and second sacra
nerves through the inferior ghiteal nerve; the Glutei medius and minimus and the Tensor fascise
lata? by the fourth and fifth lumbar and first sacral nerves through the superior gluteal; the Piri-
formis is supplied by the first and second sacral nerves; the Gemellus inferior and Quadratus
femoris by the last lumbar and first sacral nerves; the Gemellus superior and Obturator internas
bj' the first, second, and third sacral ner^-es, and the Obturator externus by the third and fourth
lumbar nerves through the obturator.
Head of femur
Obturator nerve
Aid. inf. iliac spine
Fig. 436. — The Obturator externus.
Actions. — When the Glutaeus maximus takes its fixed point from the pelvis, it extends the
femur and brings the bent thigh into a fine with the body. Taking its fixed point from below,
it acts upon the pelvis, supporting it and the trunk upon the head of the femur; this is especially
obvious in standing on one leg. Its most powerful action is to cause the body to regain the erect
position after stooping, by drawing the pelvis backward, being assisted in this action by the
Biceps femoris, Semitendinosus, and Semimembranosus. The Gluteus maximus is a tensor of
the fascia lata, and by its connection with the iliotibial band steadies the femur on the articular
surfaces of the tibia during standing, when the Extensor muscles are relaxed. The lower part
of the muscle also acts as an adductor and external rotator of the limb. The GlutiPi medius and
minimus abduct the thigh, when the limb is extended, and are principally called into action in
supporting the body on one limb, in conjunction with the Tensor fascine latae. Their anterior
fibers, by drawing the greater trochanter forward, rotate the thigh inward, in which action they
are also assisted by the Tensor fascia lata?. The Tensor fascislataj is a tensor of the fascia lata;
continuing its action, the oblique direction of its fibers enables it to abduct the thigh and to rotate
it inward. In the erect posture, acting from below, it will serve to steady the pelvis upon the head
of the femur; and by means of the iliotibial band it steadies the condyles of the femur on the
articular surfaces of the tibia, and assists the Glutaeus maximus in supjjorting the knee in the
extended position. The remaining muscles are powerful external rotators of the thigh. In the
sitting posture, when the thigh is flexed upon the pelvis, their action as rotators ceases, and they
become abductors, with the exception of the Obturator externus, which still rotates the femur
outward.
4. The Posterior Femoral Muscles (Hamstring Muscles) (Fig. 434).
Biceps femoris. Semitendinosus. Semimembranosus.
The Biceps femoris (Biceps) is situated on the posterior and lateral aspect of the
thigh. It has two heads of origin; one, the long head, arises from the lower and inner
THE POSTERIOR FEMORAL MUSCLES 479
impression on the back part of the tuberosity of the ischium, by a tendon common
to it and the Semitendinosus, and from the lower part of the sacrotuberous Hga-
ment; the other, the short head, arises from the lateral lip of the linea aspera,
between the Adductor magnus and Vastus lateralis, extending up almost as high
as the insertion of the Gluta^us maximus; from the lateral prolongation of the
linea aspera to within 5 cm. of the lateral condyle; and from the lateral inter-
muscular septum. The fibers of the long head form a fusiform belly, which passes
obliquely downward and lateralward across the sciatic nerve to end in an aponeu-
rosis which covers the posterior surface of the muscle, and receives the fibers of
the short head; this aponeurosis becomes gradually contracted into a tendon,
which is inserted into the lateral side of the head of the fibula, and by a small
slip into the lateral condyle of the tibia. At its insertion the tendon divides into
two portions, which embrace the fibular collateral ligament of the knee-joint.
From the posterior border of the tendon a thin expansion is given off to the fascia
of the leg. The tendon of insertion of this muscle forms the lateral hamstring;
the common peroneal nerve descends along its medial border.
Variations. — The short head may be absent; additional heads may arise from the ischial
tuberosity, the linea aspera, the medial supracondylar ridge of the femur or from various other
parts. A slip may pass to the Gastrocnemius.
The Semitendinosus, remarkable for the great length of its tendon of insertion,
is situated at the posterior and medial aspect of the thigh. It arises from the lower
and medial impression on the tuberosity of the ischium, by a tendon common
to it and the long head of the Biceps femoris; it also arises from an aponeurosis
which connects the adjacent surfaces of the two muscles to the extent of about
7.5 cm. from their origin. The muscle is fusiform and ends a little below the middle
of the thigh in a long round tendon which lies along the medial side of the popliteal
fossa; it then curves around the medial condyle of the tibia and passes over the
tibial collateral ligament of the knee-joint, from which it is separated by a bursa,
and is inserted into the upper part of the medial surface of the body of the tibia,
nearly as far forward as its anterior crest. At its insertion it gives off from its
lower border a prolongation to the deep fascia of the leg and lies behind the tendon
of the Sartorius, and below that of the Gracilis, to which it is united. A tendinous
intersection is usually observed about the middle of the muscle.
The Semimembranosus, so called from its membranous tendon of origin, is situ-
ated at the back and medial side of the thigh. It arises by a thick tendon from
the upper and outer impression on the tuberosity of the ischium, above and lateral
to the Biceps femoris and Semitendinosus. The tendon of origin expands into an
aponeurosis, which covers the upper part of the anterior surface of the muscle; from
this aponeurosis muscular fibers arise, and converge to another aponeurosis which
covers the lower part of the posterior surface of the muscle and contracts into the
tendon of insertion. It is inserted mainly into the horizontal groove on the posterior
medial aspect of the medial condyle of the tibia. The tendon of insertion gives oft'
certain fibrous expansions: one, of considerable size, passes upward and lateralward
to be inserted into the back part of the lateral condyle of the femur, forming part
of the oblique popliteal ligament of the knee-joint; a second is continued downward
to the fascia which co^•ers the Popliteus muscle; while a few fibers join the tibial
collateral ligament of the joint and the fascia of the leg. The muscle overlaps the
upper part of the popliteal vessels.
Variations. — It may be reduced or absent, or double, arising mainly from the sacrotuberous
ligament and giving a slip to the femur or Adductor magnus.
The tendons of insertion of the two preceding muscles form the medial ham-
strings.
480 MYOLOGY
Nerves. — The muscles of this region are supplied by the fourth and fifth lumbar and the first,
second, and third sacral nerves; the nerve to the short head of the Biceps femoris is derived from
the common peroneal, the other muscles are supplied through the tibial nerve.
Actions. — The hamstring muscles flex the leg upon the thigh. When the knee is semiflexed,
the Biceps femoris in consequence of its oblique direction rotates the leg slightly outward; and
the Semitendinosus, and to a slight extent the Semimembranosus, rotate the leg inward, assist-
ing the Popliteus. Taking their fixed point from below, these muscles serve to support the pelvis
upon the head of the femm*, and to draw the trunk directly backward, as in raising it fr6m the
stooping position or in feats of strength, when the body is thrown backward in the form of an
arch. As already indicated on page 285, complete flexion of the hip cannot be effected unless
the knee-joint is also flexed, on account of the shortness of the hamstring muscles.
III. THE MUSCLES AND FASCIA OF THE LEG.
The muscles of the leg may be divided into three groups: anterior, posterior,
and lateral.
1. The Anterior Crural Muscles (Fig. 437).
Tibialis anterior. Extensor digitorum longus.
Extensor hallucis longus. Perona?us tertius.
Deep Fascia (fascia cruris). — The deep fascia of the leg forms a complete invest-
ment to the muscles, and is fused with the periosteum over the subcutaneous
surfaces of the bones. It is continuous above with the fascia lata, and is attached
around the knee to the patella, the ligamentum patellse, the tuberosity and con-
dyles of the tibia, and the head of the fibula. Behind, it forms the popliteal fascia,
covering in the popliteal fossa; here it is strengthened by transverse fibers, and
perforated by the small saphenous vein. It receives an expansion from the tendon
of the Biceps femoris laterally, and from the tendons of the Sartorius, Gracilis,
Semitendinosus, and Semimembranosus medially; in front, it blends with the peri-
osteum covering the subcutaneous surface of the tibia, and with that covering
the head and malleolus of the fibula; below, it is continuous with the transverse
crural and laciniate ligaments. It is thick and dense in the upper and anterior
part of the leg, and gives attachment, by its deep surface, to the Tibialis anterior
and Extensor digitorum longus; but thinner behind, where it covers the Gastroc-
nemius and Soleus. It gives off from its deep surface, on the lateral side of the leg,
two strong intermuscular septa, the anterior and posterior peroneal septa, which
enclose the Perona'i longus and brevis, and separate them from the muscles of
the anterior and posterior crural regions, and several more slender processes which
enclose the individual muscles in each region. A broad transverse intermuscular
septum, called the deep transverse fascia of the leg, intervenes between the super-
ficial and deep posterior crural muscles.
The Tibialis anterior (Tibialis anticus) is situated on the lateral side of the tibia;
it is thick and fleshy above, tendinous below. It arises from the lateral condyle
and upper half or two-thirds of the lateral surface of the body of the tibia; from
the adjoining part of the interosseous membrane; from the deep surface of the
fascia ; and from the intermuscular septum between it and the Extensor digitorum
longus. The fibers run vertically downw\ard, and end in a tendon, which is apparent
on the anterior surface of the muscle at the lower third of the leg. After passing
through the most medial compartments of the transverse and cruciate crural
ligaments, it is inserted into the medial and under surface of the first cuneiform
bone, and the base of the first metatarsal bone. This muscle overlaps the anterior
tibial vessels and deep peroneal nerve in the upper part of the leg.
Variations. — A deep portion of the muscle is rarely inserted into the talus, or a tendinous slip
may pass to the head of the first metatarsal bone or the base of the first phalanx of the great toe.
The Tibiofasdalis anterior, a small muscle from the lower part of the tibia to the transverse or
cruciate crural ligaments or deep fascia.
THE ANTERIOR CRURAL MUSCLES
481
The Extensor hallucis longus {Extensor proprius
hallucis) is a thin muscle, situated between the
Tibialis anterior and the Extensor digitorum
longus. It arises from the anterior surface of the
fibula for about the middle two-fourths of its
extent, medial to the origin of the Extensor digi--
toruift longus; it also arises from the interosseous
membrane to a similar extent. The anterior
tibial vessels and deep peroneal nerve lie between
it and the Tibialis anterior. The fibers pass
downward, and end in a tendon, which occupies
the anterior border of the muscle, passes through
a distinct compartment in the cruciate crural
ligament, crosses from the lateral to the medial
side of the anterior tibial vessels near the bend of
the ankle, and is inserted into the base of the distal
phalanx of the great toe. Opposite the metatarso-
phalangeal articulation, the tendon gives off a thin
prolongation on either side, to cover the surface
of the joint. An expansion from the medial side
of the tendon is usually inserted into the base of
the proximal phalanx.
Variations. — Occasionally united at its origin with the
Extensor digitorum longus. Extensor ossis melatarsi hal-
lucis, a small muscle, sometimes found as a slip from the
Extensor hallucis longus, or from the Tibialis anterior, or
from the Extensor digitorum longus, or as a distinct mus-
cle; it traverses the same compartment of the transverse
ligament with the Extensor hallucis longus.
The Extensor digitorum longus is a penniform
muscle, situated at the lateral part of the front
of the leg. It arises from the lateral condyle of
the tibia; from the vipper three-fourths of the
anterior surface of the body of the fibula; from
the upper part of the interosseous membrane;
from the deep surface of the fascia ; and from the
intermuscular septa between it and the Tibialis
anterior on the medial, and the Peromvi on the
lateral side. Between it and the Tibialis anterior
are the upper portions of the anterior tibial vessels
and deep peroneal nerve. The tendon passes under
the transverse and cruciate crural ligaments in
company with the Perona^us tertius, and divides
into four slips, which run forward on the dorsum
of the foot, and are inserted into the second and
third phalanges of the four lesser toes. The ten-
dons to the second, third, and fourth toes are
each joined, opposite the metatarsophalangeal
articulation, on the lateral side by a tendon of
the Extensor digitorum brevis. The tendons are
inserted in the following manner: each receives a
fibrous expansion from the Interossei and Lum-
bricalis, and then spreads out into a broad apon-
eurosis, which covers the dorsal surface of the
31
Cruraii
^, ^lij[ Cnunate
\Nin> crural
li<ja?nent
Fig. 437. — Muscles of the front of
the leg.
482 MYOLOGY
first phalanx: this aponeurosis, at the articulation of the first with the second
phalanx, divides into three slips — an intermediate, which is inserted into the base
of the second phalanx; and two collateral slips, which, after uniting on the dorsal
surface of the second phalanx, are continued onward, to be inserted into the base
of the third phalanx.
Variations. — This muscle varies considerably in the modes of origin and the arrangement of its
varioiis tendons. The tendons to the second and fifth toes may be found doubled, or extra slips
are given off from one or more tendons to their corresponding metatarsal bones, or to the short
extensor, or to one of the interosseous muscles. A slip to the great toe from the innermost tendon
has been found.
The Peronaeus tertius is a part of the Extensor digitorum longus, and might
be described as its fifth tendon. The fibers belonging to this tendon arise from
the lower third or more of the anterior surface of the fibula; from the lower part
of the interosseous membrane; and from an intermuscular septum between it
and the Peronaeus brevis. The tendon, after passing under the transverse and
cruciate crural ligaments in the same canal as the Extensor digitorum longus,
is inserted into the dorsal surface of the base of the metatarsal bone of the little
toe. This muscle is sometimes wanting.
Nerves. — These muscles are suppUed by the fourth and fifth lumbar and first sacral nerves
through the deep peroneal nerve.
Actions. — The Tibialis anterior and Peronaeus tertius are the direct flexors of the foot at the
ankle-joint; the former muscle, when acting in conjunction with the Tibialis posterior, raises the
medial border of the foot, i. e., inverts the foot; and the latter, acting with the Peronaei brevis
and longus, raises the lateral border of the foot, i. e., everts the foot. The Extensor digitorum
longus and Extensor hallucis longus extend the phalanges of the toes, and, continuing their
action, flex the foot upon the leg. Taking their fixed points from below, in the erect posture,
all these muscles serve to fix the bones of the leg in the perpendicular position, and give increased
strength to the ankle-joint.
2. The Posterior Crural Muscles.
The muscles of the back of the leg are subdivided into two groups — superficial
and deep. Those of the superficial group constitute a powerful muscular mass,
forming the calf of the leg. Their large size is one of the most characteristic
features of the muscular apparatus in man, and bears a direct relation to his erect
attitude and his mode of progression.
The Superficial Group (Fig. 438).
Gastrocnemius. Soleus. Plantaris.
The Gastrocnemius is the most superficial muscle, and forms the greater part
of the calf. It arises bv two heads, which are connected to the condyles of the
femur by strong, flat tendons. The medial and larger head takes its origin from a
depression at the upper and back part of the medial condyle and from the adjacent
part of the femur. The lateral head arises from an impression on the side of the
lateral condyle and from the posterior surface of the femur immediately above
the lateral part of the condyle. Both heads, also, arise from the subjacent part
of the capsule of the knee. Each tendon spreads out into an aponeurosis, which
covers the posterior surface of that portion of the muscle to which it belongs.
From the anterior surfaces of these tendinous expansions, muscular fibers are
given oft"; those of the medial head being thicker and extending lower than those
of the lateral. The fibers unite at an angle in the middle line of the muscle in a
tendinous raphe, which expands into a broad aponeurosis on the anterior surface
of the muscle, and into this the remaining fibers are inserted. The aponeurosis,
gradually contracting, unites with the tendon of the Soleus, and forms with it
the tendo calcaneus.
THE POSTERIOR CRURAL MUSCLES 483
Variations. — Absence of the outer head or of the entire muscle. Extra sHps from the popliteal
surface of the femur.
The Soleus is a broad flat muscle situated immediately in front of the Gastroc-
nemius. It arises by tendinous fibers from the back of the head of the fibula,
and from the upper third of the posterior surface of the body of the bone ; from the
popliteal line, and the middle third of the medial border of the tibia; some fibers
also arise from a tendinous arch placed between the tibial and fibular origins
of the muscle, in front of which the popliteal vessels and tibial nerve run. The
fibers end in an aponeurosis which covers the posterior surface of the muscle, and,
gradually becoming thicker and narrower, joins with the tendon of the Gastroc-
nemius, and forms with it the tendo calcaneus.
Variations. — Accessory head to its lower and inner part usually ending in the tendocalcaneus, or
the calcaneus, or the laciniate ligament.
The Gastrocnemius and Soleus together form a muscular mass which is occa-
sionally described as the Triceps surae; its tendon of insertion is the tendo calcaneus,
Tendo Calcaneus {tendo Achillis). — The tendo calcaneus, the common tendon of the
Gastrocnemius and Soleus, is the thickest and strongest in the body. It is about
15 cm. long, and begins near the middle of the leg, but receives fleshy fibers on its
anterior surface, almost to its lower end. Gradually becoming contracted below,
it is inserted into the middle part of the posterior surface of the calcaneus, a bursa
being interposed between the tendon and the upper part of this surface. The ten-
don spreads out somewhat at its lower end, so that its narrowest part is about
4 cm. above its insertion. It is covered by the fascia and the integument, and is
separated from the deep muscles and vessels by a considerable interval filled up
with areolar and adipose tissue. Along its lateral side, but superficial to it, is the
small saphenous vein.
The Plantaris is placed between the Gastrocnemius and Soleus. It arises from
the lower part of the lateral prolongation of the linea aspera, and from the oblique
popliteal ligament of the knee-joint. It forms a small fusiform belly, from 7 to
10 cm. long, ending in a long sleiider tendon which crosses obliquely between the
two muscles of the calf, and runs along the medial border of the tendo calcaneus,
to be inserted with it into the posterior part of the calcaneus. This muscle is some-
times double, and at other times wanting. Occasionally, its tendon is lost in the
laciniate ligament, or in the fascia of the leg.
Nerves. — The Gastrocnemius and Soleus are supplied by the nrst and second sacral nerves,
and the Plantaris by the fourth and fifth lumbar and first sacral nerves, through the tibial nerve.
Actions. — The muscles of the calf are the chief extensors of the foot at the ankle-joint. They
possess considerable power, and are constantly called into use in standing, walking, dancing,
and leaping; hence the large size they usually present. In walking, these muscles raise the heel
from the ground; the body being thus supported on the raised foot, the opposite limb can be
carried forward. In standing, the Soleus, taking its fixed point from below, steadies the leg upon
the foot and prevents the body from faUing forward. The Gastrocnemius, acting from below,
serves to flex the femur upon the tibia, assisted by the Pophteus. The Plantaris is the rudiment
of a large muscle which in some of the lower animals is continued over the calcaneus to be inserted
into the plantar aponeurosis. In man it is an accessory to the Gastrocnemius, extending the
ankle if the foot be free, or bending the knee if the foot be fixed.
The Deep Group (Fig. 439).
Popliteus. Flexor digitorum longus.
Flexor hallucis longus. Tibialis posterior.
Deep Transverse Fascia. — The deep transverse fascia of the leg is a transversely
placed, intermuscular septum, between the superficial and deep muscles of the
back of the leg. At the sides it is connected to the margins of the tibia and
484
MYOLOGY
fibula. Ahore, where it covers the PopHteiis, it is thick and dense, and receives
an expansion from the tendon of the Semimembranosus; it is thinner in the middle
femur I
Tendons of
Peronae longus
et brevis
/m
v»
^medial J/iZateraV^
Condyle '///j ' Condyle
c\
^M
t P L I TE L Si
fPOSTE-RlOP
I
Fig. 438. — Muscles of the back of the leg.
Superficial layer.
Fig. 439. — Muscles of the back of the leg.
Deep layer.
of the leg; but below, where it covers the tendons passing behind the malleoli,
it is thickened and continuous with the laciniate ligament.
The Popliteus is a thin, flat, triangular muscle, which forms the lower part of
i;
THE POSTERIOR CRURAL MUSCLES 485
the floor of the popliteal fossa. It arises by a strong tendon about 2.5 cm. long,
from a depression at the anterior part of the groove on the lateral condyle of the
femur, and to a small extent from the oblique popliteal ligament of the knee-joint;
and is inserted into the medial two-thirds of the triangular surface above the pop-
liteal line on the posterior surface of the body of the tibia, and into the tendinous
expansion covering the surface of the muscle.
Variations. — Additional head from the sesamoid bone in the outer head of the Gastrocnemias.
PopUtcus vunor, rare, origin from femur on the inner side of the Plantaris, insertion into the pos-
terior ligament of the knee-joint. Peroneotibialis, 14 per cent., origin inner side of the head of the
fibula, insertion into the upper end of the oblique line of the tibia, it lies beneath the Popliteus.
The Flexor hallucis longus is situated on the fibular side of the leg. It arises
from the inferior two-thirds of the posterior surface of the body of the fibula, with
the exception of 2.5 cm. at its lowest part; from the lower part of the interosseous
membrane; from an intermuscular septum between it and the Peronsei, laterally,
and from the fascia covering the Tibialis posterior, medially. The fibers pass
obliquely downward and backward, and end in a tendon which occupies nearly
the whole length of the posterior surface of the muscle. This tendon lies in a groove
which crosses the posterior surface of the lower end of the tibia, the posterior
surface of the talus, and the under surface of the sustentaculum tali of the calca-
neus; in the sole of the foot it runs forward between the two heads of the Flexor
hallucis brevis, and is inserted into the base of the last phalanx of the great toe.
The grooves on the talus and calcaneus, which contain the tendon of the muscle,
are converted by tendinous fibers into distinct canals, lined by a mucous sheath.
As the tendon passes forward in the sole of the foot, it is situated above, and
crosses from the lateral to the medial side of the tendon of the Flexor digitorum
longus, to which it is connected by a fibrous slip.
Variations. — Usually a slip runs to the Flexor digitorum and frequently an additional slip runs
from the Flexor digitorum to the Flexor hallucis. Pcroneocalcaneus internus, rare, origin below
or outside the Flexor hallucis from the back of the fibula, passes over the sustentaculiun tali with
the Flexor hallucis and is inserted into the calcaneum.
The Flexor digitorum longus is situated on the tibial side of the leg. At its
origin it is thin and pointed, but it gradually increases in size as it descends. It
arises from the posterior surface of the body of the tibia, from immediately below
the popliteal line to Avithin 7 or 8 cm. of its lower extremity, medial to the tibial
origin of the Tibialis posterior; it also arises from the fascia covering the Tibialis
posterior. The fibers end in a tendon, which runs nearly the whole length of the
posterior surface of the muscle. This tendon passes behind the medial malleolus,
in a groove, common to it and the Tibialis posterior, but separated from the latter
by a fibrous septum, each tendon being contained in a special compartment lined
by a separate mucous sheath. It passes obliquely forward and lateralward, super-
ficial to the deltoid ligament of the ankle-joint, into the sole of the foot (Fig. 444),
where it crosses below the tendon of the Flexor hallucis longus, and receives from it
a strong tendinous slip. It then expands and is joined by the Quadratus plant*,
and finally divides into four tendons, which are inserted into the bases of the last
phalanges of the second, third, fourth, and fifth toes, each tendon passing through
an opening in the corresponding tendon of the Flexor digitorum brevis opposite
the base of the first phalanx.
Variations. — Flexor accessorius longus digitorum, not infrequent, origin from fibula, or tibia,
or the deep fascia and ending in a tendon which, after passing beneath the laciniate ligament,
joins the tendon of the long flexor or the Quadratus plantse.
The Tibialis posterior {Tibialis 'posticus) lies between the two preceding muscles,
and is the most deeply seated of the muscles on the back of the leg. It begins
above by two pointed processes, separated by an angular interval through w^hich
486 MYOLOGY
the anterior tibial vessels pass forward to the front of the leg. It arises from the
whole of the posterior surface of the interosseous membrane, excepting its lowest
part; from the lateral portion of the posterior surface of the body of the tibia,
between the commencement of the popliteal line above and the junction of the
middle and lower thirds of the body below; and from the upper two-thirds of the
medial surface of the fibula; some fibers also arise from the deep transverse fascia,
and from the intermuscular septa separating it from the adjacent muscles. In
the lower fourth of the leg its tendon passes in front of that of the Flexor digitorum
longus and lies with it in a groove behind the medial malleolus, but enclosed in a
separate sheath; it next passes under the laciniate and over the deltoid ligament
into the foot, and then beneath the plantar calcaneonavicular ligament. The
tendon contains a sesamoid fibrocartilage, as it runs under the plantar calcaneo-
navicular ligament. It is inserted into the tuberosity of the navicular bone, and
gives off fibrous expansions, one of which passes backward to the sustentaculum tali
of the calcaneus, others forward and lateralward to the three cuneiforms, the
cuboid, and the bases of the second, third, and fourth metatarsal bones.
Nerves. — The Popliteus is supplied by the fourth and fifth lumbar and first sacral nerves,
the Flexor digitorum longus and Tibialis posterior by the fifth lumbar and first sacral, and the
Flexor hallucis longus by the fifth lumbar and the first and second sacral nerves, through the
tibial nerve.
Actions. — The Pophteus assists in flexing the leg upon the thigh; when the leg is flexed, it will
rotate the tibia inward. It is especially called into action at the beginning of the act of bending
the knee, inasmuch as it produces the shght inward rotation of the tibia which is essential in the
early stage of this movement. The Tibialis posterior is a direct extensor of the foot at the ankle-
joint; acting in conjunction with the Tibialis anterior, it turns the sole of the foot upward and
medialward, i. e., inverts the foot, antagonizing the Peron»i, which turn it upward and lateral-
ward (evert it). In the sole of the foot the tendon of the TibiaUs posterior hes direct^ below the
plantar calcaneonavicular ligament, and is therefore an important factor in maintaining the
arch of the foot. The Flexor digitorum longus and Flexor hallucis longus are the direct flexors of
the phalanges, and, continuing their action, extend the foot upon the leg; thej- assist the Gastroc-
nemius and Soleus in extending the foot, as in the act of walking, or in standing on tiptoe. In
consequence of the oblique direction of its tendons the Flexor digitorum longus would draw the
toes medialward, were it not for the Quadratus plantre, which is inserted into the lateral side
of the tendon, and draws it to the middle line of the foot. Taking their fixed point from the
foot, these muscles serve to maintain the upright posture by steadying the tibia and fibula
perpendicularly upon the talus.
3. The Lateral Crural Muscles (Fig. 439).
Peronjcus longus. Peronseus brevis.
The Peronseus longus is situated at the upper part of the lateral side of the
leg, and is the more superficial of the two muscles. It arises from the head and
upper two-thirds of the lateral surface of the body of the fibula, from the deep
surface of the fascia, and from the intermuscular septa between it and the muscles
on the front and back of the leg; occasionally also by a few fibers from the lateral
condvle of the tibia. Between its attachments to the head and to the bodv of the
fibula there is a gap through which the common peroneal nerve passes to the front
of the leg. It ends in a long tendon, which runs behind the lateral malleolus, in
a groove common to it and the tendon of the Peronaeus brevis, behind which it
lies; the groove is converted into a canal by the superior peroneal retinaculum, and
the tendons in it are contained in a common mucous sheath. The tendon then
extends obliquely forward across the lateral side of the calcaneus, below the troch-
lear process, and the tendon of the Peronaeus brevis, and under cover of the inferior
peroneal retinaculum. It crosses the lateral side of the cuboid, and then runs on the
under surface of that bone in a groove which is converted into a canal by the long
plantar ligament; the tendon then crosses the sole of the foot obliquely, and is
inserted into the lateral side of the base of the first metatarsal bone and the lateral
THE LATERAL CRURAL MUSCLES
487
side of the first cuneiform. Occasionally it sends a slip to the base of the second
metatarsal bone. The tendon changes its direction at two points: first, behind the
lateral malleolus; secondly, on the cuboid bone; in both of these situations the ten-
don is thickened, and, in the latter, a sesamoid fibrocartilage (sometimes a bone),
is usually developed in its substance.
Tibialis anterior M
Interosseous
membrane
Extensores longi digi-
torum et hallucis Mm.
Deep peroneal nerve
and anterior tibial--,
artery and vein
Perona'i longus m i
and brevis M7n.~'"^
Superficial peroneal..-Y.'^
nerve
Tibia
Fibula'
Peroneal arter\
and vein
Flexor digitorum
longus M.
Great saphenous vein
..- ' and saphenous nerve
\ _. 'Posterior tibial vein
-'■\\ and artery
..-Tibial nerve
Soleus M.
'-■Tendo m. plantaris
^'Gastrocnemius M.
Gastrocnemius M.
'^Median cutaneous
nerve
Lateral cutaneous
nerve
Small saphenous vein
Fig. 440. — Cross-section through middle of leg. (Eycleshymer and Srhoemaker.)
The Peronseus brevis lies under cover of the Peronseus longus, and is a shorter
and smaller muscle. It arises from the lower two-thirds of the lateral surface of
the body of the fibula; medial to the Peronseus longus; and from the intermuscular
septa separating it from the adjacent muscles on the front and back of the leg.
The fibers pass vertically downward, and end in a tendon which runs behind the
lateral malleolus along with but in front of that of the preceding muscle, the two
tendons being enclosed in the same compartment, and lubricated by a common
mucous sheath. It then runs forward on the lateral side of the calcaneus, above
the trochlear process and the tendon of the Peronieus longus, and is inserted into
the tuberosity at the base of the fifth metatarsal bone, on its lateral side.
On the lateral surface of the calcaneus the tendons of the Peronsei longus and
brevis occupy separate osseoaponeurotic canals formed by the calcaneus and the
perineal retinacula; each tendon is enveloped by a forward prolongation of the
common mucous sheath.
Variations. — Fusion of the two peronsei is rare. A slip from the Feronteus longus to the base
of the third, fourth or fifth metatarsal bone, or to the Adductor hallucis is occasionally seen.
PeroncEus accessorius, origin from the fibula between the longus and brevis, joins the tendon
of the longus in the sole of the foot.
PeroncBus quinti dlgiti, rare, origin lower fourth of the fibula under the brevis, insertion into the
Extensor aponeurosis of the little toe. More common as a slip of the tendon of the Peronaeus
brevis.
Peronceus quartus, 13 per cent. (Gruber), origin back of fibula between the brevis and the Plexor
hallucis, insertion into the peroneal spine of the calcaneum, {peroneocalcaneus externum), or less
frequently into the tuberosity of the cuboid (peroneocuboideus) .
Nerves. — The Peronaei longus and brevis are supplied by the fourth and fifth lumbar and
first sacral nerves through the superficial peroneal nerve.
488
MYOLOGY
Actions. — The Peronaei longus and brevis extend the foot upon fhe leg, in conjunction with
the Tibiahs posterior, antagonizing the TibiaHs anterior and Perona^us tertius, which are flexors
of the foot. The Perona?us longus also everts the sole of the foot, and from the oblique direction
of the tendon across the sole of the foot is an important agent in the maintenance of the trans-
verse arch. Taking their fixed points below, the Peroneei serve to steady the leg upon the foot.
This is especially the case in standing upon one leg, when the tendency of the superincumbent
weight is to throw the leg medialward ; the Peronaeus longus overcomes this tendency by drawing
on the lateral side of the leg.
THE FASCIA AROUND THE ANKLE.
Fibrous bands, or thickened portions of the fascia, bind down the tendons in
front of and behind the ankle in their passage to the foot. They comprise three
Hgaments, viz., the transverse crural, the cruciate crural and the laciniate; and the
superior and inferior peroneal retinacula.
^f^^^''
^P.
Tibialis anterior
WB^^ ii''^}'\ / Extensor din, lonqus
•I ;.3("
Ext. haU. long.
Ext. dig. brevis
Tendo calcaneus
PcroncEus longus
PeroruB>is breins Perotiatta tertius
Fio. 441. — The mucous sheaths of the tendons around the ankle. Lateral aspect.
Transverse Crural Ligament (ligamentiim transversum cruris; upj)er part of anterior
annular ligament) (Fig. 441). — The transverse crural ligament binds down the
tendons of Extensor digitorum longus. Extensor hallucis longus, Perona?us tertius,
and Tibialis anterior as they descend on the front of the tibia and fibula; under
it are found also the anterior tibial vessels and deep peroneal nerve. It is attached
laterallv to the lower end of the fibula, and mediallv to the tibia; above it is con-
tinuous with the fascia of the leg.
Cruciate Crural Ligament {ligamentum cruciatum cruris; lower part of anterior
annular ligament) (Figs. 441, 442). — The cruciate crural ligament is a Y-shaped
band placed in front of the ankle-joint, the stem of the Y being attached laterally
to the upper surface of the calcaneus, in front of the depression for the interosseous
talocalcanean ligament; it is directed medialward as a double layer, one lamina
passing in front of, and the other behind, the tendons of the Peronaeus tertius
and Extensor digitorum longus. At the medial border of the latter tendon these
two layers join together, forming a compartment in which the tendons are
enclosed. From the medial extremity of this sheath the two limbs of the Y diverge :
one is directed upward and medialward, to be attached to the tibial malleolus,
passing over the Extensor hallucis longus and the vessels and nerves, but enclosing
THE FASCIA AROUND THE ANKLE
489
the Tibialis anterior by a splitting of its fibers. The other limb extends downward
and mediahvard, to be attached to the border of the plantar aponeurosis, and })asses
over the tendons of the Extensor hallucis longus and Tibialis anterior and also
the vessels and nerves.
Laciniate Ligament {ligamentum laciniatum; internal annular ligament). — The
laciniate ligament is a strong fibrous band, extending from the tibial malleolus
above to the margin of the calcaneus below, converting a series of bony grooves
in this situation into canals for the passage of the tendons of the Flexor muscles
and the posterior tibial vessels and tibial nerve into the sole of the foot. It is
continuous by its upper border with the deep fascia of the leg, and by its lower
border with the plantar aponeurosis and the fibers of origin of the Abductor
hallucis muscle. Enumerated from the medial side, the four canals which it forms
transmit the tendon of the Tibialis posterior; the tendon of the Flexor digitorum
longus; the posterior tibial vessels and tibial nerve, which run through a broad
space beneath the ligament; and lastly, in a canal formed partly by the talus, the
tendon of the Flexor hallucis longus.
Tibialis anterior
Tibialis posterior
Flexor dig. longus
Ext. hall. long.
T endocalcaneus
Fio. 442. — The mucous aheaths of the tendons around the ankle. Medial aspect.
Peroneal Retinacula. — The peroneal retinacula are fibrous bands which bind
down the tendons of the Perontei longus and brevis as they run across the lateral
side of the ankle. The fibers of the superior retinaculum {external annular ligament)
are attached above to the lateral malleolus and beloiv to the lateral surface of the
calcaneus. The fibers of the inferior retinaculum are continuous in front with those
of the cruciate crural ligament; behind they are attached to the lateral surface of
the calcaneus; some of the fibers are fixed to the peroneal trochlea, forming a septum
between the tendons of the Peroniiei longus and brevis.
The Mucous Sheaths of the Tendons Around the Ankle.^ — All the tendons crossing
the ankle-joint are enclosed for part of their length in mucous sheaths which have
an almost uniform length of about 8 cm. each. On the front of the ankle (Fig. 441)
the sheath for the Tibialis anterior extends from the upper margin of the trans-
verse crural ligament to the interval between the diverging limbs of the cruciate
ligament; those for the Extensor digitorum longus and Extensor hallucis longus
reach upward to just above the level of the tips of the malleoli, the former being
the higher. The sheath of the Extensor hallucis longus is prolonged on to the base
of the first metatarsal bone, while that of the Extensor digitorum longus reaches
490 MYOLOGY
only to the level of the base of the fifth metatarsal. On the medial side of the ankle
(Fig. 442) the sheath for the Tibialis posterior extends highest up — to about
4 cm. above the tip of the malleolus — while below it stops just short of the tuber-
osity of the navicular. The sheath for Flexor hallucis longus reaches up to the level
of the tip of the malleolus, while that for the Flexor digitorum longus is slightly
higher; the former is continued to the base of the first metatarsal, but the latter
stops opposite the first cuneiform bone.
On the lateral side of the ankle (Fig. 441) a sheath which is single for the greater
part of its extent encloses the Peronau longus and brevis. It extends upward
for about 4 cm. above the tip of the malleolus and downward and forward for
about the same distance.
IV. THE MUSCLES AND FASCLffi OF THE FOOT.
1. The Dorsal Muscle of the Foot.
Extensor digitorum brevis.
The fascia on the dorsum of the foot is a thin membranous layer, continuous
above with the transverse and cruciate crural ligaments; on either side it blends
with the plantar aponeurosis; anteriorly it forms a sheath for the tendons on the
dorsum of the foot.
The Extensor digitorum brevis (Fig. 441) is a broad, thin muscle, which arises
from the forepart of the upper and lateral surfaces of the calcaneus, in front of
the groove for the Peronaeus brevis; from the lateral talocalcanean ligament;
and from the common limb of the cruciate crural ligament. It passes obliquely
across the dorsum of the foot, and ends in four tendons. The most medial, which
is the largest, is inserted into the dorsal surface of the base of the first phalanx of
the great toe, crossing the dorsalis pedis artery; it is frequently described as a
separate muscle — the Extensor hallucis brevis. The other three are inserted into
the lateral sides of the tendons of the Extensor digitorum longus of the second,
third, and fourth toes.
Variations. — Accessory slips of origin from the tahis and navicular, or from the external cunei-
form and third metatarsal bones to the second slip of the muscle, and one from the cuboid to the
third slip have been observed. The tendons vary in number and position ; they may be reduced
to two, or one of them may be doubled, or an additional slip may pass to the little toe. A super-
numerary slip ending on one of the metatarsophalangeal articulations, or joining a dorsal inter-
osseous muscle is not uncommon. Deep slips between this muscle and the Dorsal interossei occur.
Nerves. — It is suppUed by the deep peroneal nerve.
Actions. — The Extensor digitorum brevis extends the phalanges of the four toes into which
it is inserted, but in the great toe acts only on the first phalanx. The obhquity of its direction
counteracts the oblique movement given to the toes by the long Extensor, so that when both
muscles act, the toes are evenly extended.
2. The Plantar Muscles of the Foot.
Plantar Aponeurosis (aponeurosis plantaris; plantar fascia). — The plantar apo-
neurosis is of great strength, and consists of pearly white glistening fibers, disposed,
for the most part, longitudinally: it is divided into central, lateral, and medial
portions.
The central portion, the thickest, is narrow behind and attached to the medial
process of the tuberosity of the calcaneus, posterior to the origin of the Flexor
digitorum brevis; and becoming broader and thinner in front, divides near the
heads of the metatarsal bones into five processes, one for each of the toes. Each
of these processes divides opposite the metatarsophalangeal articulation into two
strata, superficial and deep. The superficial stratum is inserted into the skin of
THE PLANTAR MUSCLES OF THE FOOT 491
the transverse sulcus which separates the toes from the sole. The deeper stratum
divides into two slips which embrace the side of the Flexor tendons of the toes,
and blend with the sheaths of the tendons, and with the transverse metatarsal
ligament, thus forming a series of arches through which the tendons of the short
and long Flexors pass to the toes. The intervals left between the five processes
allow the digital vessels and nerves and the tendons of the Lumbricales to become
superficial. At the point of division of the aponeurosis, numerous transverse
fasciculi are superadded; these serve to increase the strength of the aponeurosis
at this part by binding the processes together, and connecting them with the integu-
ment. The central portion of the plantar aponeurosis is continuous with the lateral
and medial portions and sends upward into the foot, at the lines of junction, two
strong vertical intermuscular septa, broader in front than behind, which separate
the intermediate from the lateral and medial plantar groups of muscles; from these
again are derived thinner transverse septa which separate the various layers' of
muscles in this region. The upper surface of this aponeurosis gives origin behind
to the Flexor digitorum brevis.
The lateral and medial portions of the plantar aponeurosis are thinner than
the central piece, and cover the sides of the sole of the foot.
The lateral portion covers the under surface of the Abductor digiti quinti; it is
thin in front and thick behind, where it forms a strong band between the lateral
process of the tuberosity of the calcaneus and the base of the fifth metatarsal bone;
it is continuous medially with the central portion of the plantar aponeurosis, and
laterally with the dorsal fascia.
The medial portion is thin, and covers the under surface of the Abductor hallucis;
it is attached behind to the laciniate ligament, and is continuous around the side
of the foot with the dorsal fascia, and laterally with the central portion of the plantar
aponeurosis.
The muscles in the plantar region of the foot may be divided into three groups,
in a similar manner to those in the hand. Those of the medial plantar region
are connected with the great toe, and corrrespond with those of the thumb; those
of the lateral plantar region are connected with the little toe, and correspond with
those of the little finger; and those of the intermediate plantar region are connected
with the tendons intervening between the two former groups. But in order to
facilitate the description of these muscles, it is more convenient to divide them into
four layers, in the order in which they are successively exposed.
The First Layer (Fig. 443).
Abductor hallucis. Flexor digitorum brevis.
Abductor digiti quinti.
The Abductor hallucis lies along the medial border of the foot and covers the
origins of the plantar vessels and nerves. It arises from the medial process of the
tuberosity of the calcaneus, from the laciniate ligament, from the plantar aponeu-
rosis, and from the intermuscular septum between it and the Flexor digitorum
brevis. The fibers end in a tendon, which is inserted, together with the medial
tendon of the Flexor hallucis brevis, into the tibial side of the base of the first
phalanx of the great toe.
Variations. — Slip to the base of the first phalanx of the second toe.
The Flexor digitorum brevis lies in the middle of the sole of the foot, imme-
diately above the central part of the plantar aponeurosis, with which it is firmly
united. Its deep surface is separated from the lateral plantar vessels and nerves
492
MYOLOGY
by a thin layer of fascia. It arises by a narrow tendon, from the medial process
of the tuberosity of the calcaneus, from the central part of the plantar aponeurosis,
and from the intermuscular septa between it and the adjacent muscles. It passes
forward, and divides into four tendons, one for each of the four lesser toes. Oppo-
site the bases of the first phalanges, each tendon divides into two slips, to allow of
the passage of the corresponding tendon of the Flexor digitorum longus; the two
portions of the tendon then unite and form a grooved channel for the reception
of the accompanying long Flexor tendon. Finally, it divides a second time, and
is inserted into the sides of the second phalanx
about its middle. The mode of division of the
'Hi%|% tendons of the Flexor digitorum brevis, and of
their insertion into the phalanges, is analogous
to that of the tendons of the Flexor digitorum
sublimis in the hand.
Variations. — Slip to the little toe frequentlj' wanting,
23 jjcr cent.; or it may be replaced by a small fusiform
muscle arising from the long flexor tendon or from the
Quadratus plantae.
Fibrous Sheaths of the Flexor Tendons. — The
terminal portions of the tendons of the long
and short Flexor muscles are contained in
osseoaponeurotic canals similar in their ar-
rangement to those in the fingers. These
canals are formed above by the phalanges
and below bv fibrous bands, which arch across
the tendons, and are attached on either side
to the margins of the phalanges. Opposite
the bodies of the proximal and second pha-
langes the fibrous bands are strong, and the
fibers are transverse; but opposite the joints
thev are much thinner, and the fibers are
directed obliquely. Each canal contains a
mucous sheath, which is reflected on the con-
tained tendons.
The Abductor digiti quinti (Abductor minimi
digiti) lies along the lateral border of the foot,
and is in relation by its medial margin with
the lateral plantar vessels and nerves. It arises,
by a broad origin, from the lateral process of
the tuberosity of the calcaneus, from the under
surface of the calcaneus between the two pro-
cesses of the tuberosity, from the forepart of
the medial process, from the plantar aponeu-
rosis, and from the intermuscular septum
between it and the Flexor digitorum brevis. Its
tendon, after gliding over a smooth facet on the
under surface of the base of the fifth metatarsal bone, is inserted, with the
Flexor digiti quinti brevis, into the fibular side of the base of the first phalanx
of the fifth toe.
Variations. — Slips of origin from the tuberosity at the base of the fifth metatarsal Abductor
ossis metatarsi quinti, origin external tubercle of the calcaneus, insertion into tuberosity of the
fifth metatarsal bone in common with or beneath the outer margin of the plantar fascia.
Fig. 443. — Muscles of the sole of the foot.
First laver.
THE PLANTAR MUSCLES OF THE FOOT 493
The Second Layer (Fig. 444).
Quadratus plante. Lumbricales.
The Quadratus plantae (Flexor accessorius) is separated from the muscles of
the first layer by the lateral plantar vessels and nerve. It arises by two heads,
which are separated from each other by the long plantar ligament: the medial
or larger head is muscular, and is attached to the medial concave surface of the
calcaneus, below the groove which lodges the tendon of the Flexor hallucis longus;
the lateral head, flat and tendinous, arises from the lateral border of the inferior
surface of the calcaneus, in front of the lateral process of its tuberosity, and from
the long plantar ligament. The two portions join at an acute angle, and end in a
flattened band which is inserted into the lateral margin and upper and under sur-
faces of the tendon of the Flexor digitorum longus, forming a kind of groove, in
which the tendon is lodged. It usually sends slips to those tendons of the Flexor
digitorum longus which pass to the second, third, and fourth toes.
Variations. — Lateral head often wanting; entire muscle absent. Variation in the niunber of
digital tendons to wliich fibers can be traced. Most frequent offsets are sent to the second, third
and fourth toes; in many cases to the fifth as well; occasionally to two toes only.
The Lumbricales are four small muscles, accessory to the tendons of the Flexor
digitorum longus and numbered from the medial side of the foot; they arise from
these tendons, as far back as their angles of division, each springing from two
tendons, except the first. The muscles end in tendons, which pass forward on
the medial sides of the four lesser toes, and are inserted into the expansions of
the tendons of the Extensor digitorum longus on the dorsal surfaces of the first
phalanges.
Variations. — Absence of one or more; doubling of the third or fourth. Insertion partly or wholly
into the first phalanges.
The Third Layer (Fig. 445).
Flexor hallucis brevis. Adductor hallucis.
Flexor digiti quinti brevis.
The Flexor hallucis brevis arises, by a pointed tendinous process, from the medial
part of the under surface of the cuboid bone, from the contiguous portion of the
third cuneiform, and from the prolongation of the tendon of the Tibialis posterior
which is attached to that bone. It divides in front into two portions, which are
inserted into the medial and lateral sides of the base of the first phalanx of the
great toe, a sesamoid bone being present in each tendon at its insertion. The medial
portion is blended with the Abductor hallucis previous to its insertion; the lateral
portion with the Adductor hallucis; the tendon of the Flexor hallucis longus lies
in a groove between them; the lateral portion is sometimes described as the first
Interosseous plantaris.
Variations. — Origin subject to considerable variation; it often receives fibers from the calcaneus
or long j)lantar ligament. Attachment to the cuboid sometimes wanting. Slip to first phalanx
of the second toe.
The Adductor hallucis ( Adductor obliquiis hallucis) arises by two heads — oblique
and transverse. The oblique head is a large, tliick, fleshy mass, crossing the foot
obliquely and occupying the hollow space under the first, second, third, and fourth
metatarsal bones. It arises from the bases of the second, third, and fourth meta-
tarsal bones, and from the sheath of the tendon of the Peronreus longus, and is
inserted, together with the lateral portion of the Flexor hallucis brevis, into the
lateral side of the base of the first phalanx of the great toe. The transverse head
(Transversus pedis) is a narrow, flat fasciculus which arises from the plantar meta-
494
MYOLOGY
tarsophalangeal ligaments of the third, fourth, and fifth toes (sometimes only
from the third and fourth), and from the transverse ligament of the metatarsus.
It is inserted into the lateral side of the base of the first phalanx of the great toe,
its fibers blending with the tendon of insertion of the oblique head.
Fig. 444.-
-Mu8cles of the sole of the foot.
Second layer.
FiQ. 445. — Muscles of the sole of the foot.
Third layer.
Variations. — Slips to the base of the first phalanx of the second toe. Opponens hallucis, occasional
slips from the adductor to the metatarsal bone of the great toe.
The Abductor, Flexor brevis, and Adductor of the great toe, like the similar
muscles of the thumb, give off, at their in.sertions, fibrous expansions to blend
with the tendons of the Extensor digitorum longus.
The Flexor digiti quinti brevis {Flexor brevis minimi digiti) lies under the
metatarsal bone of the little toe, and resembles one of the Interossei. It arises
from the base of the fifth metatarsal bone, and from the sheath of the Peronseus
longus; its tendon is inserted into the lateral side of the base of the first phalanx
of the fifth toe. Occasionally a few of the deeper fibers are inserted into the
lateral part of the distal half of the fifth metatarsal bone; these are described by
some as a distinct muscle, the Opponens digiti quinti.
THE PLANTAR MUSCLES OF THE FOOT
495
The Fourth Layer.
Interossei.
The Interossei in the foot are similar to those in the hand, with this exception,
that they are grouped around the middle line of the second digit, instead of that
of the third. They are seven in number, and consist of two groups, dorsal and
plantar.
The Interossei dorsales (Dorsal interossei) (Fig. 446), /owr in number, are situated
between the metatarsal bones. They are bipenniform muscles, each arising by
two heads from the adjacent sides of the metatarsal bones between which it is
placed; their tendons are inserted into the bases of the first phalanges, and into the
aponeurosis of the tendons of the Extensor digitorum longus. In the angular
interval left between the heads of each of the three lateral muscles, one of the
perforating arteries passes to the dorsum of the foot; through the space between
the heads of the first muscle the deep plantar branch of the dorsalis pedis artery
enters the sole of the foot. The first is inserted into the medial side of the second
toe; the other three are inserted into the lateral sides of the second, third, and
fourth toes.
Fig. 446. — The Interossei dorsales. Left foot.
Fio. 447. — The Interossei plantares. Left foot.
The Interossei plantares {Plantar interossei) (Fig. 447), three in number, lie
beneath rather than between the metatarsal bones, and each is connected with
but one metatarsal bone. They arise from the bases and medial sides of the bodies
of the third, fourth, and fifth metatarsal bones, and are inserted into the medial
sides of the bases of the first phalanges of the same toes, and into the aponeuroses
of the tendons of the Extensor digitorum longus.
Nerves. — The Flexor digitorum brevis, the Flexor hallucis brevis, the Abductor hallucis,
and the first Lumbricalis are suppUed by the medial plantar nerve; all the other muscles in the
sole of the foot by the lateral plantar. The first Interosseous dorsahs frequently receives an
extra filament from the medial branch of the deep peroneal nerve on the dorsum of the foot,
and the second Interosseous dorsahs a twig from the lateral branch of the same nerve.
Actions. — All the muscles of the foot act upon the toes, and may be grouped as abductors,
adductors, flexors, or extensors. The abductors are the Interossei dorsales, the Abductor hallucis.
496 MYOLOGY
and the Abductor digiti quinti. The Interossei dorsales are abductors from an imaginary line
passing through the axis of the second toe, so that the first muscle draws the second toe medial-
ward, toward the great toe, the second muscle draws the same toe lateralward, and the third
and fourth draw the third and fourth toes in the same direction. Like the Interossei in the hand,
each assists in flexing the first phalanx and extending the second and third phalanges. The
Abductor hallucis abducts the great toe from the second, and also flexes its proximal phalanx.
In the same way the action of the Abductor digiti quinti is twofold, as an abductor of this toe
from the fourth, and also as a flexor of its proximal phalanx. The adductors are the Interossei
plantares and the Adductor hallucis. The Interossei plantares adduct the third, fourth, and
fifth toes toward the imaginary line passing through the second toe, and by means of their inser-
tions into the aponeuroses of the Extensor tendons they assist in flexing the proximal phalanges
and extending the middle and terminal phalanges. The oblique head of the Adductor hallucis
is chiefly concerned in adducting the great toe toward the second one, but also assists in flexing
this toe; the transverse head approximates all the toes and thus increases the curve of the trans-
verse arch of the metatarsus. The flexors are the Flexor digitorum brevis, the Quadratus plantse,
the Flexor hallucis brevis, the Flexor digiti quinti brevis, and the Lumbricales. The Flexor
digitorum brevis flexes the second phalanges upon the first, and, continuing its action, flexes the
first phalanges also, and brings the toes together. The Quadratus planta) assists the Flexor digi-
torum longus and converts the oblique pull of the tendons of that muscle into a direct backward
puU upon the toes. The Flexor digiti quinti brevis flexes the little toe and draws its metatarsal
bone downward and medialward. The Lumbricales, like the corresponding muscles in the hand,
assist in flexing the proximal phalanges, and by their insertions into the tendons of the Extensor
digitorum longus aid that muscle in straightening the middle and terminal phalanges. The
Extensor digitorum brevis extends the first phalanx of the great toe and assists the long Extensor
in extending the next three toes, and at the same time gives to the toes a lateral direction when
they are extended.
BIBLIOGRAPHY.
Bardeen, C. R.: Development and Variation, etc., of the Inferior Extremity, etc.. Am. Jour.
Anat., 1907, vi.
Bardeen and Lewis: Development of the Back, Body Wall and Limbs in Man, Am. Jour.
Anat., 1901, i.
Eisler, p.: Die Muskein des Stammes, v. Bardeleben's Handbuch der Anatomic des Menschen,
Bd. ii, Abt. ii, Teil 1.
FiCK, R.: Anatomic und Mechanik der Gelenke unter Beriicksichtigung der bewegenden
Muskein, v. Bardeleben's Handbuch der Anatomie des Menschen, Bd. ii, Abt. i, Teil 2 and 3.
Froh.se and Frankel: Die Muskein des Menschlichcn Beines; Die Muskein des Menschlichen
Armes, Handbuch der Anatomie des Menschen, von Bardeleben, Bd. ii, Abt. ii, Teil 2, A and B.
Henle, J.: Handbuch der Systematischen Anatomie des Menschen, 1871-79.
Koch, J. C. : The Laws of Bone Architecture, Am. Jour. Anat., 1917, xxi.
Le Double: Traite des Variations du Sj'steme Musculaire de L'Homme, 1897.
Lewis, W. H.: Development of the Arm in Man, Am. Jour. Anat., 1901, i.
Lewis, W. H. : Development of the Muscular System, Keibel and Mall, Manual of Human
Embryology.
PoiRiER, P., et Charpy, a.: Traite d'Anatomie, 1899-1901.
Testut, L. : Traite d'Anatomie Humaine, 1893-94.
Wolff, J.: Das Gesetz der Transformation der Knochen, Berlin, 1892.
ANGIOLOGY.
rpHE vascular system is divided for descriptive purposes into (a) the blood
J- vascular system, which comprises the heart and bloodvessels for the circula-
tion of the blood; and (6) the lymph vascular system, consisting of lymph glands
and lymphatic vessels, through which a colorless fluid, the lymph, circulates. It
must be noted, however, that the two systems communicate with each other and
are intimately associated developmentally.
The heart is the central organ of the blood vascular system, and consists of a
hollow muscle; by its contraction the blood is pumped to all parts of the body
through a complicated series of tubes, termed arteries. The arteries undergo
enormous ramification in their course throughout the body, and end in minute
vessels, called arterioles, which in their turn open into a close-meshed network
of microscopic vessels, termed capillaries. After the blood has passed through the
capillaries it is collected into a series of larger vessels, called veins, by which it is
returned to the heart. The passage of the blood through the heart and blood-
vessels constitutes what is termed the circulation of the blood, of which the following
is an outline.
The human heart is divided by septa into right and left halves, and each half
is further divided into two cavities, an upper termed the atrium and a lower the
ventricle. The heart therefore consists of four chambers, two, the right atrium
and right ventricle, forming the right half, and two, the left atrium and left ventricle
the left half. The right half of the heart contains venous or impure blood; the left,
arterial or pure blood. The atria are receiving chambers, and the ventricles dis-
tributing ones. From the cavity of the left ventricle the pure blood is carried into
a large artery, the aorta, through the numerous branches of which it is distributed
to all parts of the body, with the exception of the lungs. In its passage through
the capillaries of the body the blood gives up to the tissues the materials necessary
for their growth and nourishment, and at the same time receives from the tissues
the waste products resulting from their metabolism. In doing so it is changed
from arterial into venous blood, which is collected by the veins and through them
returned to the right atrium of the heart. From this cavity the impure blood
passes into the right ventricle, and is thence conveyed through the pulmonary
arteries to the lungs. In the capillaries of the lungs it again becomes arterialized,
and is then carried to the left atrium by the pulmonary veins. From the left atrium
it passes into the left ventricle, from which the cycle once more begins.
The course of the blood from the left ventricle through the body generally to
the right side of the heart constitutes the greater or systemic circulation, while its
passage from the right ventricle through the lungs to the left side of the heart is
termed the lesser or pulmonary circulation.
It is necessary, however, to state that the blood which circulates through the
spleen, pancreas, stomach, small intestine, and the greater part of the large intes-
tine is not returned directly from these organs to the heart, but is conveyed by the
portal vein to the liver. In the liver this vein divides, like an artery, and ultimately
ends in capillary-like vessels (sinusoids), from which the rootlets of a series of veins,
called the hepatic veins, arise; these carry the blood into the inferior vena cava,
32 ( 497 )
498
ANGIOLOGY
whence it is conveyed to the right atrium. From this it will be seen that the
blood contained in the portal vein passes through two sets of vessels: (1) the
capillaries in the spleen, pancreas, stomach, etc., and (2) the sinusoids in the liver.
The blood in the portal vein carries certain of the products of digestion: the carbo-
hydrates, which are mostly taken up by the liver cells and stored as glycogen, and
the protein products which remain in solution and are carried into the general
circulation to the various tissues and organs of the body.
Speaking generally, the arteries may be said to contain pure and the veins
impure blood. This is true of the systemic, but not of the pulmonary vessels,
since it has been seen that the impure blood is conveyed from the heart to the lungs
by the pulmonary arteries, and the pure blood returned from the lungs to the heart
by the pulmonary veins. Arteries, therefore, must be defined as vessels which
convey blood from the heart, and veins as vessels which return blood io the heart.
Structure of Arteries (Fig. 448). — The arteries are composed of three coats: an internal or
endothelial coat {tunica intima of KoUiker); a middle or muscular coat {tunica media); and an
external or connective-tissue coat (tunica adventitia).
The two inner coats together are very easily separated
from the external, as by the ordinary operation of
tying a ligature around an artery. If a fine string be
tied forcibly upon an artery and then taken off, the
external coat will be found undivided, but the two
inner coats are divided in the track of the Ugature
and can easily be further dissected from the outer
coat.
The inner coat {tunica intima) can be separated
from the middle by a little maceration, or it may be
stripped off in small pieces; but, on account of its
friabiUty, it cannot be separated as a complete mem-
brane. It is a fine, transparent, colorless structure
which is highly elastic, and, after death, is commonly
corrugated into longitudinal WTinkles. The inner coat
consists of: (1) A layer of pavement endotheUum,
the cells of which are polygonal, oval, or fusiform,
and have very distinct round or oval nuclei. This
endothelium is brought into view most distinctly by
staining with nitrate of silver. (2) A subendothelial
layer, consisting of delicate connective tissue with
branched cells lying in the interspaces of the tissue;
in arteries of less than 2 mm. in diameter the sub-
endotheUal layer consists of a single stratum of stel-
late cells, and the connective tissue is only largely
developed in vessels of a considerable size. (3) An
elastic or fenestrated layer, which consists of a mem-
brane containing a net-work of elastic fibers, having
principally a longitudinal direction, and in which,
under the microscope, smaU elongated apertures or
perforations may be seen, giving it a fenestrated ap-
pearance. It was therefore called by Henle the fenes-
trated membrane. This membrane forms the chief
thickness of the inner coat, and can be separated into
several layers, some of which present the appearance
of a net-work of longitudinal elastic fibers, and others
a more membranous character, marked by pale lines
having a longitudinal direction. In minute arteries
the fenestrated membrane is a very thin layer; but in the larger arteries, and especially in the
aorta, it has a very considerable thickness.
The middle coat (tunica media) is distinguished from the inner by its color and by the trans-
verse arrangement of its fibers. In the smaller arteries it consists principally of plain muscle
fibers in fine bundles, arranged in lamellae and disposed circularly around the vessel. These
lamellae vary in number according to the size of the vessel; the smallest arteries having only a
single layer (Fig. 449), and those shghtly larger three or four layers. It is to this coat that the
thickness of the wall of the artery is mainly due (Fig. 448^, m). In the larger arteries, as the
Fig. 448. — Transverse section through a small
arterj' and vein of the mucous membrane of the
epiglottis of a child. X 350. (Klein and Noble
Smith.) A. Artery, showing the nucleated endo-
thelium, €, which lines it; the vessel being con-
tracted, the endothelial cells appear very thick.
Underneath the endothelium is the wavy elastic
lamina. The chief part of the wall of the vessel
is occupied by the circular muscle coat m; the
rod-shaped nuclei of the muscle cella are well seen.
Outside this is a, part of the adventitia. This is
composed of bundles of connective tissue fibers,
shown in section, with the nuclei of the connec-
tive tissue corpuscles. The adventitia gradually
merges into the surrounding connective tissue.
V. Vein showing a thin endothelial membrane.
e, raised accidentally from the intima, which on
account of its delicacy is seen as a mere line on the
media m. This latter is composed of a few circular
unstriped muscle cells o. The adventitia, similar
in structure to that of an arterj-.
STRUCTURE OF ARTERIES
499
FiQ. 449. — Small arterj' and vein, pia mater of
sheep. X 250. Surface view above the inter-
rupted line; longitudinal section below. Artery
in red; vein in blue,
iliac, femoral, and carotid, elastic fibers unite to form lamellae which alternate with the layers
of muscular fibers; these laraelke are united to one another by elastic fibers which pass between
the muscular bundles, and are connected with the fenestrated membrane of the inner coat (Fig.
450). In the largest arteries, as the aorta and innominate, the amount of elastic tissue is very
considerable; in these vessels a few bundles of white connective tissue also have been found in
the middle coat. The muscle fiber cells are about 50^ in length and contain well-marked, rod-
shaped nuclei, which are often sUghtly curved.
The external coat {tunica adventitia) consists mainly of fine and closely felted bundles of white
connective tissue, but also contains elastic fibers in all but the smallest arteries. The elastic
tissue is much more abundant next the tunica media,
and it is sometimes described as forming here, between
the adventitia and media, a special layer, the tunica
elastica externa of Henle. This layer is most marked
in arteries of medium size. In the largest vessels the
external coat is relatively thin; but in small arteries
it is of greater proportionate thickness. In the smaller
arteries it consists of a single layer of white connec-
tive tissue and elastic fibers; while in the smallest
arteries, just above the capillaries, the elastic fibers
are wanting, and the connective tissue of which the
coat is composed becomes more nearly homogeneous
the nearer it approaches the capillaries, and is grad-
ually reduced to a thin membranous envelope, which
finally disappears.
Some arteries have extremely thin walls in propor-
tion to their size; this is especially the case in those
situated in the cavity of the cranium and vertebral
canal, the difference depending on the thinness of the
external and middle coats.
The arteries, in their distribution throughout the
body, are included in thin fibro-areolar investments,
which form their sheaths. The vessel is loosely con-
nected with its sheath by delicate areolar tissue; and
the sheath usually encloses the accompanying veins,
and sometimes a nerve. Some arteries, as those in the cranium, are not included in sheaths.
All the larger arteries, like the other organs of the body, are supplied with bloodvessels. These
nutrient vessels, called the vasa vasorum, arise from a branch of the artery, or from a neighbor-
ing vessel, at some considerable distance from the point at which they are distributed; they
ramify in the loose areolar tissue connecting the artery with its sheath, and are distributed to
the external coat, but do not, in man, penetrate the other coats; in some of the larger mammals
a few vessels have been traced into the middle coat. Minute veins return the blood from these
vessels; they empty themselves into the vein or veins accompanying the artery. Lymphatic
vessels are also present in the outer coat.
Arteries are also supplied with nerves, which are derived from the sympathetic, but may pass
through the cerebrospinal nerves. They form intricate plexuses upon the surfaces of the larger
trunks, and run along the smaller arteries as single filaments, or bundles of filaments which twist
around the vessel and unite with each other in a plexiform manner. The branches derived from
these plexuses penetrate the external coat and are distributed principally to the muscular tissue
of the middle coat, and thus regulate, by causing the contraction and relaxation of this tissue
the amount of blood sent to any part.
The Capillaries. — The smaller arterial branches (excepting those of the cavernous structure
of the sexual organs, of the splenic pulp, and of the placenta) terminate in net-works of vessels
which pervade nearly every tissue of the body. These vessels, from their minute size, are termed
capillaries. They are interposed between the smallest branches of the arteries and the commenc-
ing veins, constituting a net-work, the branches of which maintain the same diameter throughout;
the meshes of the net-work are more uniform in shape and size than those formed by the anasto-
moses of the small arteries and veins.
The diameters of the capillaries vary in the different tissues of the body, the usual size being
about 8^. The smallest are those of the brain and the mucous membrane of the intestines;
and the largest those of the skin and the marrow of bone, where they are stated to be as large
as 20/x in diameter. The form of the capillary net varies in the different tissues, the meshes being
generally rounded or elongated.
The rounded form of mesh is most common, and prevails where there is a dense network, as in
the lungs, in most glands and mucous membranes, and in the cutis; the meshes are not of an
absolutely circular outhne, but more or less angular, sometimes nearly quadrangular, or polygonal,
or more often irregular.
500
ANGIOLOGY
Elongated meshes are observed in the muscles and nerves, the meshes resembling parallelograms
in form, the long axis of the mesh running parallel with the long axis of the nerve or muscle.
Sometimes the capillaries have a looped arrangement; a single vessel projecting from the common
net-work and returning after forming one or more loops, as in the papillae of the tongue and
skin.
The number of the capillaries and the size of the meshes determine the degree of vascularity
of a part. The closest network and the smallest interspaces are found in the lungs and in the
choroid coat of the eye. In these situations the interspaces are smaller than the capillary vessels
themselves. In the intertubular plexus of the kidney, in the conjunctiva, and in the cutis, the
interspaces are* from three to f om- times as large as the capillaries which form them ; and in the
brain from eight to ten times as large as the capillaries in their long diameters, and from four
to six times as large in their transverse diameters. In the adventitia of arteries the width of the
meshes is ten times that of the capillary vessels. As a general rule, the more active the func-
tion of the organ, the closer is its capillary net and the larger its supply of blood; the meshes of
the network are very narrow in all growing parts, in the glands, and in the mucous membranes,
wider in bones and hgaments which are comparatively inactive; bloodvessels are nearly alto-
gether absent in tendons, in which very little organic change occurs after their formation. In
the hver the capillaries take a more or less radial course toward the intralobular vein, and then-
walls are incomplete, so that the blood comes into direct contact with the Hver cells. These
vessels in the liver are not true capillaries but "sinusoids;" they are developed by the growth
of columns of hver cells into the blood spaces of the embryonic organ.
lCA'0»Cr\
•J
Endothelial and sub-
endothelial layer of
inner coat
— Elastic layer
Innermost layers of
iniddle coat
IUnI^cA
Outermost layers of
~' middle coat
Innermost part of
outer coat
Outermost part of
r"" outer coat
Fig. 450. — Section of a medium-sized artery, (.\fter Griinstein.)
Structure. — The waU of a capillary consists of a fine transparent endothehal layer, composed
of cells joined edge to edge by an interstitial cement substance, and continuous with the endo-
thehal cells which hne the arteries and veins. When stained with nitrate of silver the edges which
bound the epithelial cells are brought into view (Fig. 451). These cells are of large size and of
an irregular polygonal or lanceolate shape, each containing an oval nucleus which may be dis-
played by carmine or hematoxyUn. Between their edges, at various points of their meeting,
roundish dark spots are sometimes seen, which have been described as stomata, though they are
closed by intercellular substance. They have been beheved to be the situations through which
the colorless corpuscles of the blood, when migrating from the bloodvessels, emerge; but this
view, though probable, is not universally accepted.
Kolossow describes these cells as having a rather more complex structure. He states that
STRUCTURE OF VEINS
501
each consists of two parts: of hyaline ground plates, and of a protoplasmic granular part, in
which is imbedded the nucleus, on the outside of the ground plates. The hyahne internal coat
of the capillaries does not form a complete membrane, but consists of "plates" which are inelastic,
and though in contact with each other are not continuous; when therefore the capillaries are sub-
jected to intravascular pressure, the plates become separated from each other; the protoplasmic
portions of the cells, on the other hand, are united together. In some organs, e. g., the glomeruU
of the kidneys, intercellular cement cannot be demonstrated in the capillary wall and the cells
are beheved to form a sjTicytium.
In many situations a delicate sheath or envelope of branched nucleated connective tissue cells
is found around the simple capillary tube, particularly in the larger ones; and in other places,
especially in the glands, the capillaries are invested with retiform connective tissue.
Sinusoids. — In certain organs, viz., the heart, the liver, the suprarenal and parathyroid
glands, the glomus caroticum and glomus coccygeum, the smallest bloodvessels present various
differences from true capillaries. They are wider, with an
irregular lumen, and have no connective tissue covering,
their endothehal cells being in direct contact with the cells of
the organ. Moreover, they are either arterial or venous and
not intermediate as are the true capillaries. These vessels
have been called sinusoids by Minot. They are formed
by columns of cells or trabeculae pushing their way into a
large bloodvessel or blood space and carrying its endothe-
lium before them ; at the same time the wall of the vessel
or space grows out between the cell columns.
Structure of Veins. — The veins, like the arteries, are com-
posed of thi-ee coats: internal, middle, and external; and
these coats are, with the necessary modifications, analogous
to the coats of the arteries; the internal being the endo-
thelial, the middle the muscular, and the external the
connective tissue or areolar (Fig. 452). The main differ-
ence between the veins and the arteries is in the compara-
tive weakness of the middle coat in the former.
In the smallest veins the three coats are hardly to be dis-
tinguished (Fig. 449). The endothelium is supported on a
membrane separable into two layers, the outer of which
is the thicker, and consists of a delicate, nucleated mem-
brane iadventiiia) , while the inner is composed of a network
of longitudinal elastic fibers (media). In the veins next
above these in size (0.4 mm. in diameter), according to
KoUiker, a connective tissue layer containing numerous
muscle fibers circularly disposed can be traced, forming the
middle coat, while the elastic and connective tissue elements of the outer coat become
more distinctly perceptible. In the middle-sized veins the typical structure of these vessels
becomes clear. The endothelium is of the same character as in the arteries, but its cells
are more oval and less fusiform. It is supported by a connective tissue layer, consisting of
a dehcate net-work of branched cells, and external to this is a layer of elastic fibers disposed
in the form of a net-work in place of the definite fenestrated membrane seen in the arteries.
This constitutes the internal coat. The middle coat is composed of a thick layer of con-
nective tissue with elastic fibers, intermixed, in some veins, with a transverse layer of muscular
tissue. The white fibrous element is in considerable excess, and the elastic fibers are in much
smaller proportion in the veins than in the arteries. The outer coat consists, as in the arteries,
of areolar tissue, with longitudinal elastic fibers. In the largest veins the outer coat is from
two to five times thicker than the middle coat, and contains a large number of longitudinal
muscular fibers. These are most distinct in the inferior vena cava, especially at the termination
of this vein in the heart, in the trunks of the hepatic veins, in aU the large trunks of the portal
vein, and in the external iliac, renal, and azygos veins. In the renal and portal veins they extend
through the whole thickness of the outer coat, but in the other veins mentioned a layer of con-
nective and elastic tissue is found external to the muscular fibers. All the large veins which open
into the heart are covered for a short distance with a layer of striped muscular tissue continued
on to them from the heart. Muscular tissue is wanting: (1) in the veins of the maternal part
of the placenta; (2) in the venous sinuses of the dura mater and the veins of the pia mater of
the brain and medulla spinalis; (3) in the veins of the retina; (4) in the veins of the cancellous
tissue of bones; (5) in the venous spaces of the corpora cavernosa. The veins of the above-men-
tioned parts consist of an internal endothehal Uning supported on one or more layers of areolar
tissue.
Most veins are provided with valves which serve to prevent the reflux of the blood. Each
valve is formed by a reduplication of the inner coat, strengthened by connective tissue and elastic
Fig. 451. — Capillaries from the mesen-
tery of a guinea-pig, after treatment with
solution of nitrate of silver, a. Cells.
b. Their nuclei.
502
ANGIOLOGY
fibers, and is covered on both surfaces with endothelium, the arrangement of which differs on
the two surfaces. On the surface of the valve next the wall of the vein the cells are arranged
transversely; while on the other surface, over which the current of blood flows, the cells are
arranged longitudinally in the direction of the current. Most commonly two such valves are
found placed opposite one another, more especially in the smaller veins or in the larger trunks
at the point where they are joined by smaller branches; occasionally there are three and some-
times only one. The valves are semilunar. They are attached by their convex edges to the
wall of the vein; the concave margins are free, directed in the course of the venous current, and
lie in close apposition with the wall of the vein as long as the current of blood takes its natural
course; if, however, any regurgitation takes place, the valves become distended, then- opposed
edges are brought into contact, and the current is interrupted. The wall of the vein on the
cardiac side of the point of attachment of each valve is expanded into a pouch or sinus, which
gives to the vessel, when injected or distended with blood, a knotted appearance. The valves
are very numerous in the veins of the extremities, especially of the lower extremities, these vessels
Endothelium -~^^
Elastic layer ^■^
TuOvCA
Middle coat —
Older coat
Fig. 452. — Section of a medium-sized vem.
having to conduct the blood against the force of gi-avitj*. They are absent in the ver}' small
veins, i. e., those less than 2 mm. in diameter, also in the vense cava*, hepatic, renal, uterine, and
ovarian veins. A few valves are found in each spermatic vein, and one also at its point of junc-
tion with the renal vein or inferior vena cava respectively. The cerebral and spinal veins, the
veins of the cancellated tissue of bone, the pulmonary veins, and the umbilical vein and its
branches, are also destitute of valves. A few valves are occasionally found in the azygos and
intercostal veins. Rudimentary valves are found in the tributaries of the portal venous system.
The veins, like the arteries, are supplied with nutrient vessels, vasa vasorum. Nerves also
are distributed to them in the same manner as to the arteries, but in much less abundance.
THE BLOOD.
The blood is an opaque, rather viscid fluid, of a bright red or scarlet color
when it flows from the arteries, of a dark red or purple color when it flows from
the veins. It is salt to the taste, and has a peculiar faint odor and an alkaline
reaction. Its specific gravity is about 1.06, and its temperature is generally about
37° C, though varying slightly in different parts of the body.
THE BLOOD
503
Fig. 453. — Human red blood corpuscles. Higlily magnified, a.
Seen from the surface. 6. Seen in profile and forming rouleaux.
c. Rendered spherical by water, d. Rendered crenate by salt
solution.
General Composition of the Blood.— Blood consists of a faintly yellow fluid, the
plasma or liquor sanguinis, in which are suspended numerous minute particles,
the blood corpuscles, the majority of which are colored and give to the blood its
red tint. If a drop of blood be placed in a thin layer on a glass slide and examined
under the microscope, a number of these corpuscles will be seen floating in the
plasma.
The Blood Corpuscles are of
three kinds: (1) colored cor-
puscles or erythrocytes; (2) color-
less corpuscles or leucocytes; (3)
blood platelets.
1. Colored or red corpuscles
{erythrocytes), when examined
under the microscope, are seen
to be circular disks, biconcave in
profile. The disk has no nucleus,
but, in consequence of its bicon-
cave shape, presents, according
to the alterations of focus under
an ordinary high power, a central
part, sometimes bright, sometimes
dark, which has the appearance of a nucleus (Fig. 453, a). It is to the aggregation
of the red corpuscles that the blood owes its red hue, although when examined
by transmitted light their color appears to be only a faint reddish yellow. The
corpuscles vary slightly in size even in the same drop of blood, but the average
diameter is about 7.5^,^ and the thickness about 2/i. Besides these there are
found certain smaller corpuscles of about one-half of the size just indicated;
these are termed microcytes, and are very scarce in normal blood; in diseased con-
ditions {e. g., anemia), however, they are more numerous. The number of red
corpuscles in the blood is enormous; between 4,000,000 and 5,000,000 are con-
tained in a cubic millimetre. Power states that the red corpuscles of an adult
would present an aggregate surface of about 3000 square yards.
If the web of a living frog's foot be spread out and examined under the micro-
scope the blood is seen to flow in a continuous stream through the vessels, and the
corpuscles show no tendency to adhere to each other or to the wall of the vessel.
Doubtless the same is the case in the human body; but when himian blood is drawn
and examined on a slide without reagents the corpuscles tend to collect into heaps
like rouleaiLx of coins (Fig. 453, h). It has been suggested that this phenomenon
may be explained by alteration in surface tension. During life the red corpuscles
may be seen to change their shape under pressure so as to adapt themselves, to
some extent, to the size of the vessel. They are, however, highly elastic, and
speedily recover their shape when the pressure is removed. They are readily
influenced by the medium in which they are placed. In water they swell up, lose
their shape, and become globular {endosmosis) (Fig. 453, c). Subsequently the
hemoglobin is dissolved out, and the envelope can barely be distinguished as a
faint circular outline. Solutions of salt or sugar, denser than the plasma, give
them a stellate or crenated appearance (exosmosis) (Fig. 453, d), but the usual
shape may be restored by diluting the solution to the same tonicity as the plasma.
The crenated outline may be produced as the first effect of the passage of an elec-
tric shock: subsequently, if suflFiciently strong, the shock ruptures the envelope.
A solution of salt, isotonic with the plasma, merely separates the blood corpuscles
mechanically, without changing their shape. Two views are held with regard to
I A micromillimetre (J' ) is 1/1000 of a millimetre or 1/25000 of an inch.
504
ANGIOLOGY
the structure of the er>i:hrocytes. The older view, that of Rollett, supposes that
the corpuscle consists of a sponge work or stroma permeated by a solution of hemo-
globin. Schafer, on the other hand, believes that the hemoglobin solution is con-
tained within an envelope or membrane, and the facts stated above with regard
to the osmotic behavior of the erythrocyte support this belief. The envelope
consists mainly of lecithin, cholesterin, and nucleoprotein.
The colorless corpuscles or leucocytes are of various sizes, some no larger, others
smaller, than the red corpuscles, In human blood, however, the majority are
rather larger than the red corpuscles, and measure about 10^ in diameter. On the
average from 7000 to 12,000 leucocytes are found in each cubic millimetre of
blood.
Fig. 454. — Varieties of leucocytes found in human blood. Highly magnified.
They consist of minute masses of nucleated protoplasm, and exhibit several
varieties, which are differentiated from each other chieflv bv the occurrence or
non-occurrence of granules in their protoplasm, and by the staining reactions of
these granules when present (Fig. 454). (1) The most numerous (60 per cent.) and
important are irregular in shape, possessed of the power of ameboid movement,
and are characterized by nuclei which often consist of two or three parts (multi-
partite) connected together by fine threads of chromatin. The protoplasm is
clear, and contains a number of very fine granules, which stain with acid dyes,
such as eosin, or with neutral dyes, and are therefore called oxyphil or neutrophil
(Fig. 454, P). These cells are termed the polymorphonuclear leucocytes. (2) A
second variety comprises from 1 to 4 per cent, of the leucocytes; they are larger
than the previous kind, and are made up of coarsely granular protoplasm, the
granules being highly refractile and grouped around single nuclei of horse-shoe
shape (Fig. 454, E). The granules stain deeply with eosin, and the cells are there-
fore often termed eosinophil corpuscles. (3) The third variety is called the hyaline
cell or macrocyte (Fig. 454, //). This is usually about the same size as the eosino-
phil cell, and, when at rest, is spherical in shape and contains a single round or
oval nucleus. The protoplasm is free from granules, but is not quite transparent,
having the appearance of ground glass. (4) The fourth kind of colorless corpuscle
is designated the lymphocjrte (Fig. 454, L), because it is identical with the cell derived
from the lymph glands or other lymphoid tissue. It is the smallest of the leuco-
cytes, and consists chiefly of a spheroidal nucleus with a very little surrounding
protoplasm of a homogeneous nature; it is regarded as the immature form of the
DEVELOPMEXT OF THE VASCULAR SYSTEM
505
hyaline cell. The third ami fourth varieties together constitute from 20 to 30
per cent, of the colorless corpuscles, but of these two varieties the lymphocytes
are by far the more numerous. Leucocytes having in their protoplasm granules
which stain with basic dyes (basophil) have been described as occurring in human
blood, but they are rarely found except in disease.
The colorless corpuscles are very various in shape in living blood (Fig. 455),
because many of them have the power of constantly changing their form by pro-
truding finger-shaped or filamentous processes of their substance, by which they
move and take up granules from the surrounding medium. In locomotion the
corpuscle pushes out a process of its substance — a pseudopodiiun, as it is called
Fig. 455.-
-Human colorless blood corpuscle, showing its successive changes of outline within ten minutes when kept
moist on a warm stage. (Schofield.)
— and then shifts the rest of the body into it. In the same way when any granule
or particle comes in its way the corpuscle wraps a pseudopodium around it, and then
withdraws the pseudopodium with the contained particle into its own substance.
By means of these ameboid properties the cells have the power of wandering
or emigrating from the bloodvessels by penetrating their walls and thus finding
their way into the extravascular spaces. A chemical investigation of the proto-
plasm of the leucocytes shows the presence of nucleoprotein and of a globulin.
The occurrence of small amounts of fat, lecithin, and glycogen may also be
demonstrated.
The blood platelets (Fig. 456) are discoid or irregularly shaped, colorless, refractile
bodies, much smaller than the red corpuscles. Each contains a central chromatin
mass resembling a nucleus. Blood platelets possess the power of ameboid move-
ment. ^^hen blood is shed they rapidly disintegrate
and form granular masses, setting free prothrombin
and the substance called by Flowell thromboplastin.
It is doubtful whether they exist normally in circu-
lating blood.
DEVELOPMENT OF THE VASCULAR SYSTEM.
Bloodvessels first make their appearance in sev-
eral scattered vascular areas which are developed
simultaneously between the entoderm and the meso-
derm of the yolk-sac, i. e., outside the body of the
embryo. Here a new type of cell, the angioblast
or vasoformative cell, is differentiated from the
mesoderm. These cells as they di^•ide form small,
dense sync\'tial masses which soon join with similar
masses b\' means of fine processes to form plexuses. These plexuses increase
both by di\ision and gro^\■th of its cells and by the addition of new angioblasts
which differentiate from the mesoderm. ^Yithill these solid plexuses and also
within the isolated masses of angioblasts vacuoles appear through liquefaction of
the central part of the sync^'tium into plasma. The lumen of the bloodvessels
thus formed is probably intracellular. The flattened cells at the periphery form
the endotheliimi. The nucleated red blood corpuscles develop either from small
masses of the original angioblast left attached to the inner wall of the lumen or
directly from the flat endothelial cells. In either case the syncytial mass thus
Fig. 456.— Blood platelets. Highly
magnified. (After Kopsch.)
506
ANGIOLOGY
formed projects from and is attached to the wall of the vessel. Such a mass is
known as a blood island and hemoglobin gradually accumulates within it. Later
the cells on the surface round up, giving the mass a mulberry-like appearance.
Then the red blood cells break loose and are carried away in the plasma. Such
free blood cells continue to divide. The term blood island was originally used for
the syncytial masses of angioblasts found in the area vasculosa, but it is probably
best to limit the term to the masses within the lumen from which the red blood
cells arise as Sabin^ has done. Blood islands ha^■e been seen in the area vasculosa
in the omphalomesenteric vein and arteries, and in the dorsal aorta.
The differentiation of angioblasts from the mesoderm occurs not only in the area
vasculosa but within the embryo and probably most of the larger bloodvessels are
developed in situ in this manner. This process of the differentiation of angioblasts
from the mesoderm probably ceases in different regions of the embryo at different
periods and after its cessation
new vessels are formed by sprouts
from vessels already laid down in
the form of capillary plexuses.
The first rudiment of the heart
appears as a pair of tubular
vessels which are developed in
the splanchnopleure of the peri-
cardial area (Fig. 457). These
are named the primitive aortae,
and a direct continuity is soon
established between them and
the vessels of the yolk-sac. Each
receives anteriorly a vein— the
vitelline vein — from the yolk-sac,
and is prolonged backward on
the lateral aspect of the noto-
chord under the name of the
dorsal aorta. The dorsal aortse give branches to the yolk-sac, and are continued
backward tlu-ough the body-stalk as the umbilical arteries to the villi of the
chorion.
Eternod- describes the circulation in an embryo which he estimated to be about
thirteen days old (Fig. 458). The rudiment of the heart is situated immediately
below the fore-gut and consists of a short stem. It gives off two vessels, the primi-
tive aortae, which run backward, one on either side of the notochord, and then pass
into the body-stalk along which they are carried to the chorion. From the chorionic
villi the blood is returned by a pair of umbilical veins which unite in the body-stalk
to form a single vessel and subsequently encircle the mouth of the yolk-sac and
open into the heart. At the junction of the yolk-sac and body-stalk each vein
is joined by a branch from the vascular plexus of the yolk-sac. From his
observations it seems that, in the human embryo, the chorionic circulation is
established before that on the yolk-sac.
By the forward growth and flexure of the head the pericardial area and the
anterior portions of the primitive aortse are folded backward on the ventral aspect
of the fore-gut, and the original relation of the somatopleure and splanchnopleure
layers of the pericardial area is reversed. Each primitive aorta now consists of
a ventral and a dorsal part connected anteriorly by an arch (Fig. 459) ; these three
parts are named respectively the anterior ventral aorta, the dorsal aorta, and the
first cephalic arch. The vitelline veins which enter the embryo through the
Fig. 457. — Transverse section through the region of the heart in
a rabbit embryo of nine days. X 80. (KoIIiker.) j. j. Jugular
veins, ao. Aorta, ph. Pharynx, som. Somatopleure. 6^ Proamnion.
ect. Ectoderm, ent. Entoderm, p. Pericardium, spl. Splanchno-
pleure. ah. Outer wall of heart. iVi. Endothelial lining of heart, e'.
Septum between heart tubes.
' Anatomical ]{ecord, 1917, vol. xiii, p. 199.
^ Anat. Anzeiger, 1899, vol. xv.
DEVELOPMENT OF THE VASCULAR SYSTEM
507
Umbilical.
vein
Umbilical
vein
anterior wall of the umbilical orifice are now continuous with the posterior ends of
the anterior ventral aorta. With the formation of the tail-fold the posterior parts
of the primitive aortje are carried forward in a ventral direction to form the pos-
terior ventral aortie and primary caudal arches.^ In the pericardial region the two
primitive aortre grow together, and fuse to form a single tubular heart (Fig. 460),
the posterior end of which receives the two vitelline veins, while from its anterior
end the two anterior ventral aortae emerge.^ The first cephalic arches pass through
the mandibular arches, and behind them five additional pairs subsequently develop,
so that altogether six pairs of aortic arches are formed; the fifth arches are very
transitory vessels connecting the ventral aortse with the dorsal ends of the sixth
arches. By the rhythmical contraction of the tubular heart the blood is forced
through the aortae and bloodvessels of the vascular area, from which it is returned
to the heart by the vitelline veins. This constitutes the vitelline circulation (Fig.
459), and by means of it nutri-
ment is absorbed from the yolk
(vitellus.)
The vitelline veins at first
open separately into the poste-
rior end of the tubular heart, but
after a time their terminal por-
tions fuse to form a single ves-
sel. The vitelline veins ulti-
mately drain the blood from the
digestive tube, and are modified
to form the portal vein. This is
caused by the growth of the liver,
which interrupts their direct
continuitv with the heart; and
the blood returned by them cir-
culates through the liver before
reaching the heart.
With the atrophy of the yolk-
sac the vitelline circulation di-
minishes and ultimately ceases,
while an increasing amount of
blood is carried through the um-
bilical arteries to the villi of the
chorion. Subsequently, as the
non-placental chorionic villi atro-
phy, their vessels disappear; and
then the umbilical arteries con-
vey the whole of their contents
to the placenta, whence it is re-
turned to the heart by the umbilical veins. In this manner the placental circu-
lation is established, and by means of it nutritive materials are absorbed from,
and waste products given up to the maternal blood.
The umbilical veins, like the vitelline, undergo interruption in the developing
liver, and the blood returned by them passes through this organ before reaching
the heart. Ultimately the right umbilical vein shrivels up and disappears.
During the occurrence of these changes great alterations take place in the
primitive heart and bloodvessels.
Allantoic
diverticulum^
Body-stalk-
Neurenteric
canal
Fig. 458. — Diagram of the vascular channela in a human embryo
of the second week. (After Eternod.) The red lines are the dorsal
aortae continued into the umbilical arteries. The red dotted lines
are the ventral aortae, and the blue dotted lines the vitelline veins.
' Young and Robinson, .Journal of Anatomy and Physiology, vol. xxxii.
2 In most fishes and in the amphibia the heart originates as a single median tube.
508
ANGIOLOGY
Further Development of the Heart. — Between the endothelial lining and the
outer wall of the heart there exists for a time an intricate trabecular network of
mesodermal tissue from which, at a later stage, the musculi papillares, chordae
tendinea^, and trabecular carneue are developed. The simple tubular heart, already
Dorsal aorta
Primitive jugular
vein
CTuyrionic villi
Fig. 459. — Human embryo of about fourteen days, with yolk-sac. (After His.)
described, becomes elongated and bent on itself so as to form an S-shaped loop,
the anterior part bending to the right and the posterior part to the left (Fig. 4()()).
The intermediate portion arches transversely from left to right, and then turns
sharply forward into the anterior part of the loop. Slight constrictions make their
appearance in the tube and divide it from behind forward into five parts, viz.:
Fore-brain -fcr
Bidbus cordis
Atrium, —
Optic vesicle
— ■ Ventricle
J . '^ ' • Vitelline vein
Fig. 460. — Head of chick embryo of about thirty-eight houfs' incubation, viewed from the ventral surface. X 26
(Duval.)
(1) the sinus venosus; (2) the primitive atrium; (3) the primitive ventricle; (4) the
bulbus cordis, and (5) the tnmcus arteriosus (Figs. 461, 462). The constriction
between the atrium and ventricle constitutes the atrial canal, and indicates the site
of the future atrioventricular valves.
DEVELOPMENT OF THE VASCULAR SYSTEM
509
The sinus venosus is at first situated in the septum transversum (a layer of
mesoderm in which the Uver and the central tendon of the diaphragm are devel-
oped) behind the primitive atrium, and is formed by the union of the vitelline
veins. The veins or ducts of Cuvier from the body of the embryo and the umbilical
veins from the placenta subsequently open into it (Fig. 463). The sinus is at first
place transversely, and opens by a median aperture into the primitive atrium.
Bulbils Cord
Ventricle
Atrium
Sinus venosus
Vitelline veins
Fig. 461. — Diagram to illustrate the simple tubular
condition of the heart. (Drawn from Ecker-Ziegler
model.)
Fig. 462. — Heart of human embryo of about fourteen
days. (From model by His.)
Soon, however, it assumes an oblique position, and becomes crescentic in form; its
right half or horn increases more rapidly than the left, and the opening into the
atrium now communicates with the right portion of the atrial cavity. The right
horn and transverse portion of the sinus ultimately become incorporated with and
form a part of the adult right atrium, the line of union between it and the auricula
being indicated in the interior of the atrium by a vertical crest, the crista terminalis
of His. The left horn, which- ultimately receives onh' the left duct of Cuvier,
Bulbus cordis
Ventricle
Duct of Cuvier
Cardinal vein
Maxillary process
Stomodeum
Mandibular arch
- Atrium
Bile-duct
Umbilical vein
Fig. 463. — Heart of human embryo of about fifteen days. (Reconstruction by His.)
persists as the coronary sinus (Fig. 4(34) . The vitelline and umbilical veins are soon
replaced by a single vessel, the inferior vena cava, and the three veins (inferior vena
cava and right and left Cuvierian ducts) open into the dorsal aspect of the atrium
by a common slit-like aperture (Fig. 465). The upper part of this aperture repre-
sents the opening of the permanent superior vena cava, the lower that of the inferior
vena cava, and the intermediate part the orifice of the coronary sinus. The slit-
510
ANGIOLOGY
like aperture lies obliquely, and is guarded by two halves, the right and left venous
valves; above the opening these unite with each other and are continuous with a
Left duct of Opening into Eight duct of
Cuvier atrium Cuvier
Fia. 464. — Dorsal surface of heart of human embryo of thirty-five days. (From model by His.)
Septum spurium
Opening of sinus venosus
Left veTWus valve
Septum primum
Right venous
valve
Spina vestibuli
Posterior endocardial
cushion
Atrial canal
Septum inferius
Fig. 465. — Interior of dorsal half of heart from a humau embryo of about thirty days. (From model by His.)
fold named the septum spurium; below the opening they fuse to form a triangular
thickening — the spina vestibuli. The right venous valve is retained; a small
DEVELOPMENT OF THE VASCULAR SYSTEM
511
septum, the sinus septum, grows from the posterior wall of the sinus venosus to fuse
with the valve and divide it into two parts — an upper, the valve of the inferior
vena cava, and a lower, the valve of the coronary sinus (Fig. 4()S). The extreme
upper portion of the right venous valve, together with the septum spurium, form
Right atrium
Bulhus cordis
Left atrium
Atrial canal
Ventricle
Fig. 466. — Heart showing expansion of the atria. (Drawn from Ecker-Zeigler model.)
the crista terminalis already mentioned. The upper and middle thirds of the left
venous valve disappear; the lower third is continued into the spina vestibuli,
and later fuses with the septum secundum of the atria and takes part in the forma-
tion of the limbus fossae ovalis.
Septum secundum
Opening of coronary sinus j
Septum spurium
Right venous valve-
Right atrioventricular
opening
Left atrioventricular
opening
Septum intermedium
Septum inferius
Fig. 467.— Interior of dorsal half of heart of human embryo of about thirty-five days. (From model by His.)
The atrial canal is at first a short straight tube connecting the atrial with the
ventricular portion of the heart, but its growth is relatively slow, and it becomes
overlapped by the atria and ventricles so that its position on the surface of the heart
is indicated onlv bv an annular constriction (Fig. 406). Its lumen is reduced to a
512
ANGIOLOGY
transverse slit, and two thickenings appear, one on its dorsal and another on its
ventral wall. These thickenings, or endocardial cushions (Fig. 405) as they are
termed, project into the canal, and, meeting in the middle line, unite to form the
septum intermedium which divides the canal into two channels, the future right and
left atrioventricular orifices.
The primitive atrium grows rapidly and partially encircles the bulbus cordis;
the groove against which the bulbus cordis lies is the first indication of a division
into right and left atria. The cavity of the primitive atrium becomes subdivided
into right and left chambers by a septum, the septum primum (Fig. 4()5), which
grows downward into the ca"\'ity. For a time the atria communicate with each
other by an opening, the ostium primum of Born, below the free margin of the septum.
This opening is closed by the union of the septum primum with the septum inter-
medium, and the communication between the atria is reestablished through an
opening which is developed in the upper part of the septum primum; this opening
is known as the foramen ovale {ostium secundum of Born) and persists imtil birth.
Liji duct of Cuvier
Opening of coronary
sinus
Foramen ovale
Probe in aorta
Aortic septum
Septum
intermedium
Septum
inferiua
Fig. 468. — Same heart as in Fig. 467, opened on right side. (From model by His.)
A second septum, the septum secimdum (Figs. 467, 468), semilunar in shape, grows
downward from the upper wall of the atrium immediately to the right of the
primary septum and foramen ovale. Shortly after birth it fuses with the primary
septum, and by this means tiie foramen ovale is closed, but sometimes the fusion
is incomplete and the upper part of the foramen remains patent. The limbus fossse
ovalis denotes the free margin of the septum secundum. Issuing from each lung
is a pair of pulmonary veins; each pair unites to form a single vessel, and these in
turn join in a common trunk which opens into the left atrium. Subsequently
the common trunk and the two vessels forming it expand and form the vestibule
or greater part of the atrium, the expansion reaching as far as the openings of the
four vessels, so that in the adult all four veins open separately into the left atrium.
The primitive ventricle becomes divided by a septum, the septmn inferius or
ventricular septmn (Figs. 465, 466, 467), which grows upward from the lower part
of the ventricle, its position being indicated on the surface of the heart by a furrow.
Its dorsal part increases more rapidly than its ventral portion, and fuses Avith the
dorsal part of the septum intermedium. For a time an interventricular foramen
DEVELOPMENT OF THE VASCULAR SYSTEM
513
exists above its ventral portion (Fig. 468), but this foramen is ultimately closed by
the fusion of the aortic septum with the ventricular septum.
Fig. 469. — Diagrams to illustrate the transformation of the bulbus cordis. (Keith.) Ao. Truncus arteriosus.
Au. Atrium. B. Bulbus cordis. RV. Right ventricle. LV. Left ventricle. P. Pulmonary artery.
When the heart assumes its S-shaped form the bulbus cordis lies ventral to and
in front of the primitive ventricle. The adjacent walls of the bulbus cordis and
ventricle approximate, fuse, and finally disappear, and the bulbus cordis now
Aortic septum
Common atrio-
ventricular aperture
Right
ventricle
Septum
inferius
Left
ventricle
Aortic septum
Puhnonary
artery
Aorta
Right atrio-
ventricular
orifice
Right
ventricle
Septum inferius
Left atrio-
ventricular
orifice
Left
ventricle
Fig. 470. — Diagrams to show the development of the septum of the aortic bulb and of the ventricles. (Born.)
communicates freely with the right ventricle, while the junction of the bulbus with
the truncus arteriosus is brought directly ventral to and applied to the atrial canal.
By the upgrowth of the ventricular septum the bulbus cordis is in great measure
Aorta
Aorta,
Aorta
Pulmonary artery
Pulmo-
nary artery
Pulmonary artery
Fig. 471. — Transverse sections through the aortic bulb to show the growth of the aortic septum. The lowest
section is on the left, the highest on the right of the figure. (After His.)
separated from the left ventricle, but remains an integral part of the right ventricle,
of which it forms the infundibulum (Fig. 469).
33
514
ANGIOLOGY
The truncus arteriosus and bulbus cordis are divided by the aortic septum (Fig.
470). This makes its appearance in three portions. (1) Two distal ridge-Hke
thickenings project into the lumen of the tube; these increase in size, and ultimately
meet and fuse to form a septum, which takes a spiral course toward the proximal
end of the truncus arteriosus. It divides the distal part of the truncus into two
vessels, the aorta and pulmonary artery, which lie side by side above, but near
the heart the pulmonary artery is in front of the aorta. (2) Four endocardial
cushions appear in the proximal part of the truncus arteriosus in the region of the
future semilunar valves; the manner in which these are related to the aortic septum
is described below. (3) Two endocardial thickenings — anterior and posterior —
Second aortic arch
Third aortic arch
First aortic arch
Auditory vesicle
Primitive jugular vein
Fourth aortic arch
Sixth aortic arch
Dorsal aorta
Cardinal vein
Digestive tube
Hind-gut
Vmbilical vein
Olfactory pit
Maxillary process
Firnt branchial groove
Mandibular arch
Bulbil X cordis
Atrium
Duct of Cuvier
Ventricle
Vitelline vein
Yolk-sac
Allantois
Umbilical artery
Fig. 472. — Profile view of a human embryo estimated at twenty or twenty-oue days old. (After His.)
develop in the bulbus cordis and unite to form a short septum; this joins above with
the aortic septum and below with the ventricular septum. The septum grows down
into the ventricle as an oblique partition, which ultimately blends with the ven-
tricular septum in such a way as to bring the bulbus cordis into communication
with the pulmonary artery, and through the latter with the sixth pair of aortic
arches; while the left ventricle is brought into continuity with the aorta, which
communicates with the remaining aortic arches.
The Valves of the Heart. — The atrioventricular valves are developed in relation to
the atrial canal. By the upward expansion of the bases of the ventricles the canal
becomes invaginated into the ventricular cavities. The invaginated margin forms
the rudiments of the lateral cusps of the atrioventricular valves; the mesial or
DEVELOPMENT OF THE VASCULAR SYSTEM
515
septal cusps of the valves are developed as downward prolongations of the septum
intermedium (Fig. 467). The aortic and pulmonary semilunar valves are formed
from four endocardial thickenings — an anterior, a posterior, and two lateral —
which appear at the proximal end of the truncus arteriosus. As the aortic septum
grows downward it divides each of the lateral thickenings into two, thus giving
rise to six thickenings — the rudiments of the semilunar valves — three at the aortic
and three at the pulmonary orifice (Fig. 471).
Further Development of the Arteries.— Recent observations show that practi-
cally none of the main vessels of the adult arise as such in the embryo. In the site
of each vessel a capillary network forms, and by the enlargement of definite paths
in this the larger arteries and veins are developed. The branches of the main
arteries are not always simple modifications of the vessels of the capillary network,
but may arise as new outgrowths from the enlarged stem.
External carotid
Ventral aorta
Internal carotid
Common carotid
Aortic arch
Ductus arteriosus
Vertebral artery
Subclavian artery
Left pulmonary artery
Right svbclavian
artery
Right 'pulmonary
artery
Trunk of pulmonary
artery
Fig. 473. — Scheme of the aortic arches and their destination, (Modified from Kollmann.)
It has been seen (page 506) that each primitive aorta consists of a ventral and
a dorsal part which are continuous tlirough the first aortic arch. The dorsal aortse
at first run backward separately on either side of the notochord, but about the
third week they fuse from about the level of the fourth thoracic to that of the fourth
lumbar segment to form a single trunk, the descending aorta. The first aortic
arches run through the mandibular arches, and behind them five additional pairs
are developed within the visceral arches; so that, in all, six pairs of aortic arches
are formed (Figs. 472, 473). The first and second arches pass between the ventral
and dorsal aortae, while the others arise at first by a common trunk from the truncus
arteriosus, but end separately in the dorsal aortse. As the neck elongates, the
ventral aortse are drawn out, and the third and fourth arches arise directly from
these vessels.
In fishes these arches persist and give off branches to the gills, in which the
blood is oxygenated. In mammals some of them remain as permanent structures,
while others disappear or become obliterated (Fig. 473),
516
ANGIOLOGY
The Anterior Ventral Aortae. — These persist on both sides. The right forms (a)
the innominate artery, (b) the right common and external carotid arteries. The
left gives rise to (a) the short portion of the aortic arch, Avhich reaches from the
origin of the innominate artery to that of the left common carotid artery; {h) the
left common and external carotid arteries.
The Aortic Arches. — The first and second arches disappear early, but the dorsal
end of the second gives origin to the stapedial artery (Fig, 474), a vessel which
atrophies in man but persists in some mammals. It passes through the ring of the
stapes and divides into supraorbital, infraorbital, and mandibular branches which
follow the three divisions of the trigeminal nerve. The infraorbital and man-
Pas/, cerebral a.
Ant. cerebral ci.
Swpraorhital br
of skipedial a.
Trigeminal nerve
Maxillary nerve
Infraorbital a.
Mandibular nerve-^
Mandibular a
Ext. max. a
Lingual a.
Sup. thyroid a
Stapedial a.
Int. carotid a.
Common carotid a
Aortic arch
Pulmonary arch
Pulmonary art.
Dorsal aorta
Pig. 474. — Diagram showing the origins of the main branches of the carotid arteries. (Founded on Tandler.)
dibular arise from a common stem, the terminal part of which anastomoses with
the external carotid. On the obliteration of the stapedial artery this anastomosis
enlarges and forms the internal maxillary artery, and the branches of the stapedial
artery are now branches of this vessel. The common stem of the infraorbital and
mandibular branches passes between the two roots of the auriculotemporal nerve
and becomes the middle meningeal artery; the original supraorbital branch of the
stapedial is represented by the orbital twigs of the middle meningeal. The third
aortic arch constitutes the commencement of the internal carotid artery, and is
therefore named the carotid arch. The fourth right arch forms the right sub-
clavian as far as the origin of its internal mammarv branch ; while the fourth left
arch constitutes the arch of the aorta between the origin of the left carotid artery
DEVELOPMENT OF THE VASCULAR SYSTEM 517
and the termination of the ductus arteriosus. The fifth arch disappears on both
sides. The sixth right arch disappears; the sixth left arch gives off the pulmonary
arteries and forms the ductus arteriosus; this duct remains pervious during the
whole of fetal life, but is obliterated a few days after birth. His showed that in the
early embryo the right and left arches each gives a branch to the lungs, but that
later both pulmonary arteries take origin from the left arch.
The Dorsal Aortse. — In front of the third aortic arches the dorsal aortse persist
and form the continuations of the internal carotid arteries; these arteries pass to the
brain and each divides into an anterior and a posterior branch, the former giving
off the ophthalmic and the anterior and middle cerebral arteries, while the latter
turns back and joins the cerebral part of the vertebral artery. Behind the third
arch the right dorsal aorta disappears as far as the point where the two dorsal
aortfe fuse to form the descending aorta. The part of the left dorsal aorta between
the third and fourth arches disappears, while the remainder persists to form
the descending part of the arch of the aorta. A constriction, the aortic isthmus, is
sometimes seen in the aorta between the origin of the left subclavian and the
attachment of the ductus arteriosus.
Sometimes the right subclavian artery arises from the aortic arch distal to the
origin of the left subclavian and passes upward and to the right behind the trachea
and esophagus. This condition may be explained by the persistence of the right
dorsal aorta and the obliteration of the fourth right arch.
In birds the fourth right arch forms the arch of the aorta; in reptiles the fourth
arch on both sides persists and gives rise to the double aortic arch in these animals.
The heart originally lies on the ventral aspect of the pharynx, immediately
behind the stomodeum. With the elongation of the neck and the development
of the lungs it recedes within the thorax, and, as a consequence, the anterior
ventral aortse are drawn out and the original position of the fourth and fifth arches'
is greatly modified. Thus, on the right side the fourth recedes to the root of the
neck, while on the left side it is withdrawn within the thorax. The recurrent
nerves originally pass to the larynx under the sixth pair of arches, and are there-
fore pulled backward with the descent of these structures, so that in the adult the
left nerve hooks around the ligamentum arteriosum; owing to the disappearance of
the fifth and the sixth right arches the right nerve hooks around that immediately
above them, i. c, the commencement of the subclavian artery. Segmental arteries
arise from the primitive dorsal aortse and course between successive segments.
The seventh segmental artery is of special interest, since it forms the lower end of
the vertebral artery and, when the forelimb bud appears, sends a branch to it
(the subclavian artery). From the seventh segmental arteries the entire left
subclavian and the greater part of the right subclavian are formed. The second
pair of segmental arteries accompany the hypoglossal nerves to the brain and are
named the hypoglossal arteries. Each sends forward a branch which forms the
cerebral part of the vertebral artery and anastomoses with the posterior branch
of the internal carotid. The two vertebrals unite on the ventral surface of the
hind-brain to form the basilar artery. Later the hypoglossal artery atrophies
and the vertebral is connected with the first segmental artery. The cervical part
of the vertebral is developed from a longitudinal anastomosis between the first
seven segmental arteries, so that the seventh of these ultimately becomes the source
of the artery. As a result of the growth of the upper limb the subclavian artery
increases greatly in size and the vertebral then appears to spring from it.
Recent observations show that several segmental arteries contribute branches to
the upper limb-bud and form in it a free capillary anastomosis. Of these branches,
only one, viz., that derived from the seventh segmental artery, persists to form
the subclavian artery. The subclavian arter\ is prolonged into the limb under
the names of the axillary and brachial arteries, and these together constitute the
518
ANGIOLOGY
arterial stem for the upper arm, the direct continuation of this stem in the forearm
is the volar interosseous artery. A branch which accompanies the median nerve
soon increases in size and forms the main vessel (median artery) of the forearm,
while the volar interosseous diminishes. Later the radial and ulnar arteries are
developed as branches of the brachial part of the stem and coincidently wdth their
enlargement the median artery recedes; occasionally it persists as a vessel of some
considerable size and then accompanies the median nerve into the palm of the hand.
The primary arterial stem for the lower limb is formed by the inferior gluteal
(sciatic) artery, which accompanies the sciatic nerve along the posterior aspect of
the thigh to the back of the knee, whence it is continued as the peroneal artery.
This arrangement exists in reptiles and amphibians. The femoral artery arises
later as a branch of the common iliac, and, passing down the front and medial
side of the thigh to the bend of the knee, joins the inferior gluteal artery. The
femoral quickly enlarges, and, coincidently with this, the part of the inferior gluteal
immediately above the knee undergoes atrophy. The anterior and posterior tibial
arteries are branches of the main arterial stem.
Anterior detached portions
of umbilical veins '
Venae revehentes
Stomach
Venae advehentes
Pancreas
Bile-duct
Obliterated portions
of venous rings
Right umbilical vein
Dv£tus venosvs
Liver
Left umbilical vein.
Duodenum
Portal vein
Vitelline
veins
Fig. 475. — The liver and the veins in connection with it, of a human embryo, twenty-four or twenty-five daya old,
as seen from the ventral surface. (After His.)
Further Development of the Veins. — ^The formation of the great veins of the
embryo may be best considered by dividing them into two groups, visceral and
parietal.
The Visceral Veins. — The visceral veins are the two vitelline or omphalomesenteric
veins bringing the blood from the yolk-sac, and the two umbilical veins returning
the blood from the placenta; these four veins open close together into the sinus
venosus.
The Vitelline Veins run upward at first in front, and subsequently on either
side of the intestinal canal. They unite on the ventral aspect of the canal, and
beyond this are connected to one another by two anastomotic branches, one on the
dorsal, and the other on the ventral aspect of the duodenal portion of the intestine,
which is thus encircled by two venous rings (Fig. 475) ; into the middle or dorsal
anastomosis the superior mesenteric vein opens. The portions of the veins above
the upper ring become interrupted by the developing liver and broken up by it into
DEVELOPMENT OF THE VASCULAR SYSTEM
519
a plexus of small capillary-like vessels termed sinusoids (Minot). The branches
conveying the blood to this plexus are named the venae advehentes, and become
the branches of the portal vein; while the vessels draining the plexus into the
sinus venosus are termed the venae revehentes, and form the future hepatic veins
(Figs. 475, 476). Ultimately the left vena revehens no longer communicates
directly with the sinus venosus, but opens into the right vena revehens. The
persistent part of the upper venous ring, above the opening of the superior mes-
enteric vein, forms the trunk of the portal vein.
Right primitive jtigular vein
Right cardinal vein
Right duct of Cuvier
Sinii^ venosus
Rigjd hepatic vein
Portal vein
Portal vein
Right umbilical vein
Umbilical cord
Left primitive
jugular vein
Left cardinal vein
Left duct of Cuvier
Left hepatic vein
Left umbilical vein
Left umbilical vein
Fig. 476.-
-Human embryo with heart and anterior body-wall removed to show the sinus venosus and its tributaries.
(After His.)
The two Umbilical Veins fuse early to form a single trunk in the body-stalk,
but remain separate within the embryo and pass forward to the sinus venosus
in the side walls of the body. Like the vitelline veins, their direct connection
with the sinus venosus becomes interrupted by the developing liver, and thus at
this stage the whole of the blood from the yolk-sac and placenta passes through
the substance of the liver before it reaches the heart. The right umbilical and
right vitelline veins shrivel and disappear; the left umbilical, on the other hand,
becomes enlarged and opens into the upper venous ring of the vitelline veins; with
the atrophy of the yolk-sac the left vitelline vein also undergoes atrophy and
disappears. Finally a direct branch is established between this ring and the right
hepatic vein; this branch is named the ductus venosus, and, enlarging rapidly,
it forms a wide channel through which most of the blood, returned from the
placenta, is carried direct to the heart without passing through the liver. A small
proportion of the blood from the placenta is, however, conveyed from the left
umbilical vein to the liver through the left vena advehens. The left umbilical
520
AXGIOLOGY
vein and the ductus venosus undergo atrophy and obliteration after birth, and
form respectively the ligamentum teres and ligamentum venosum of the liver.
The Parietal Veins. — The first indication of a parietal system consists in the
appearance of two short transverse veins, the ducts of Cuvier, which open, one
on either side, into the sinus venosus. Each of these ducts receives an ascending
and descending vein. The ascending veins return tlie blood from the parietes
of the trunk and from the Wolffian bodies, and are called cardinal veins. The
descending veins return the blood from the head, and are called primitive jugular
veins (Fig. 477). The blood from the lower limbs is collected by the right and
left iliac and h^'pogast^ic veins, which, in the earlier stages of development, open
into the corresponding right and left cardinal veins; later, a transverse branch (the
left common iliac vein) is developed between the lower parts of the two cardinal
veins (Fig. 479), and through this the blood is carried into the right cardinal vein.
The portion of the left cardinal vein below the left renal vein atrophies and dis-
appears up to the point of entrance of the left spermatic vein; the portion above
Sinus venosus
Primitive jugular
Subclavian
Duct of Cuvier
Vitelline
Umbilical
Cardinal
Subcardinal
Renal
External iliac
Hypogastric
Fig. 477. — Scheme of arrangement of parietal
veins.
Internal jugular
External jugular
Subclavian
Dvct o/ Cuvier
Left cardinal
Ductus venosus
Renal
Subcardinal
External iliac
Hypogastric
Fig. 47S. — Scheme showing early stages of
development of the inferior vena cava.
the left renal vein persists as the hemiazygos and accessory hemiazygos veins
and the lower portion of the highest left intercostal vein. The right cardinal vein
which now receives the blood from both lower extremities, forms a large venous
trunk along the posterior abdominal wall; up to the level of the renal veins it
forms the lower part of the inferior vena cava. Above the level of the renal veins
the right cardinal vein persists as the azygos vein and receives the right intercostal
veins, while the hemiazygos veins are brought into communication with it by the
development of transverse branches in front of the vertebral column (Figs. 479, 480)
Inferior Vena Cava. — The development of the inferior vena cava is associated
with the formation of two veins, the subcardinal veins (Figs. 477, 478). These
lie parallel to, and on the ventral aspect of, the cardinal veins, and originate as
longitudinal anastomosing channels which link up the tributaries from the mes-
entery to the cardinal veins; they communicate with the cardinal veins above and
below, and also by a series of transverse branches. The two subcardinals are for
a time connected with each other in front of the aorta by cross branches, but these
disappear and are replaced by a single transverse channel at the level where the
DEVELOPMENT OF THE VASCULAR SYSTEM
521
renal veins join the cardinals, and at the same level a cross communication is
established on either side between the cardinal and subcardinal (Fig. 478). The
portion of the right subcardinal behind this cross communication disappears, while
Left innominate
Eight innominate
Superior vena cava.
Internal jugular
External jugular
- Duct of Cuvier
Left cardinal
Left swprarevxil
Left renal
Prerenal part of
inferior vena cava
Postrenal part of
inferior vena cava
Left common iliac
- External iliac
Hypogastric
Fig. 479. — Diagram showing development of main cross branches between jugulars and between cardinals.
that in front, i. e., the prerenal part, forms a connection with the ductus venosus
at the point of opening of the hepatic veins, and, rapidly enlarging, receives the
Left innominate
Right innominate. _
Superior vena cava
Azygos vein
Prerenal paH of
inferior vena cava ^-l
Internal jugular
External jugular
Subclavian,
Higfiest left intercostal
Ligainent of left vena cava
Oblique vein of left atrium
Coronary sinus
Accessory hemiazygos vein
Hemiazygos vein
■eft suprarenal
Left renal
Left internal spermatic
Left common iliac
External iliac
* Hypogastric
Fig. 480. — Diagram showing completion of development of the parietal veins.
blood from the postrenal part of the right cardinal through the cross communica-
tion referred to. In this manner a single trunk, the inferior vena cava (Fig. 480), is
formed, and consists of the proximal part of the ductus venosus, the prerenal part
522 ANGIOLOGY
of the right subcardinal vein, the postrenal part of the right cardinal vein, and the
cross branch which joins these two veins. The left subcardinal disappears, except
the part immediately in front of the renal vein, which is retained as the left supra-
renal vein. The spermatic (or ovarian) vein opens into the postrenal part of
the corresponding cardinal vein. This portion of the right cardinal, as already
explained, forms the lower part of the inferior vena cava, so that the right spermatic
opens directly into that vessel. The postrenal segment of the left cardinal dis-
appears, with the exception of the portion between the spermatic and renal vein,
which is retained as the terminal part of the left spermatic vein.
In consequence of the atrophy of the Wolffian bodies the cardinal veins diminish
in size; the primitive jugular veins, on the other hand, become enlarged, owing to
the rapid development of the head and brain. They are further augmented by
receiving the veins (subclavian) from the upper extremities, and so come to form
the chief veins of the Cuvierian ducts; these ducts gradually assume an almost
vertical position in consequence of the descent of the heart into the thorax. The
right and left Cuvierian ducts are originally of the same diameter, and are frequently
termed the right and left superior venae cavae. By the development of a transverse
branch, the left innominate vein between the two primitive jugular veins, the
blood is carried across from the left to the right primitive jugular (Figs. 479, 480).
The portion of the right primitive jugular vein between the left innominate and
the azygos vein forms the upper part of the superior vena cava of the adult; the
lower part of this vessel, i. e., below the entrance of the azygos vein, is formed by
the right Cuvierian duct. Below the origin of the transverse branch the left
primitive jugular vein and left Cuvierian duct atrophy, the former constituting
the upper part of the highest left intercostal vein, while the latter is represented
by the ligament of the left vena cava, vestigial fold of Marshall, and the oblique
vein of the left atrium, oblique vein of Marshall (Fig. 480). Both right and left
superior vense cavse are present in some animals, and are occasionally found in the
adult human being. The oblique vein of the left atrium passes downward across
the back of the left atrium to open into the coronary sinus, which, as already
indicated, represents the persistent left horn of the sinus venosus.
Venous Sinuses of the Dura Mater.^ — The primary arrangement for drainage of
the capillaries of the head (Figs. 481, 488) consists of a primary head vein which
starts in the region of the midbrain and runs caudalward along the side of the
brain tube to terminate at the duct of Cuvier. The primary head vein drains
three plexuses of capillaries : the anterior dural plexus, the middle dural plexus and
the posterior dural plexus. The growth of the cartilaginous capsule of the ear and
the gro^\i:h and alteration in form of the brain bring about changes in this primary
arrangement (Figs. 483-488). Owing to the growth of the otic capsule and middle
ear the course of the primary head vein becomes unfavorable and a segment of it
becomes obliterated. To make the necessary adjustment an anastomosis is estab-
lished above the otic capsule (Fig. 483) and the middle plexus drains into the poste-
rior plexus. Then the anteror plexus fuses with the middle plexus (Fig. 484) and
drains through it and the newly estabished channel, dorsal to the otic capsule.
All that remains of the primary head vein is the cardinal portion or internal jugular
and the part in the region of the trigeminal nerve which may be called the cavernous
sinus. Into it drain the orbital veins. The drainage from the cavernous sinus is
•now upward through the original trunk of the middle plexus, which is now the
superior petrosal sinus, into the newly established dorsal channel. This dorsal
channel is the transverse sinus (Figs. 485-488). The inferior petrosal sinus appears
later (Fig. 486) . From the anterior plexus a sagittal plexus extends forward from
which develops the superior sagittal sinus (Figs. 484-488). The straight sinus is
Streeter, Am. Jour. Anat., 1915, vol. xviii.
DEVELOPMENT OF THE VASCULAR SYSTEM
523
formed in the ventral part of the sagittal plexus. As the hemispheres extend back-
ward these sinuses elongate by incorporating the more caudal loops of the plexus.
The anterior part of the sinus is completed first.
P1.EXU9.MEOIAUS
PLEXUS; MEDIAUS
H TRIGEMfNUS
V. CAPITIS PRJMA
PLEXUS POST
V. CAPITIS PRIMA
M^
PLEXUS MEOIAUS
(IL£XUS,ANT
PLEXUS ANT
PLEXUS SAGITTALIS,
PLEXUS POST.
.SIN TRANS.
o
ffr :U
SIN
PETROS
^U
L^Sr^
•' /jUGULARE
V OPTHAL!><r
■v^
_[2;:4:>PARS
Tsicmoidl
\ ■
^
^■^^t^ y.
\
. /.v. JUS
INT. ,
■;
SIN. CAVERNOSUS / ^-^
484
SIN. RECTUS
PLEXUS ANT.
SIN. RECTUS
SUiL^AGirrAus sup^^,3'r
PLEXUS ANT.
(SAGiTTALis y^^^m^jLx
W'^^J :■; \ SIN. TRANSVERSUS
/ Nv SIN. TRANSVERSUS
^;SIN PETROS SUP ,
SIN. CAVERNOSUS /
485
V CEREBRAL. INF -
' SIN PETROS SUP.
K
SIN. CAVERN.
SIN. PETROS. INF
. V. JUQ.
NT
V.pPTHAL,
SIN. SAGITTALIS SUPi
SIN. R5CTU9
SIN. SAGITTALIS SU^.
CONFLUEN9
SINUUM
SIN. TRANS. V. OPTHAL
PARS SIGMOID,
SAGITTAU9 I
INP.
SIN. RECTUS
CONFLUEN9
, SINUUM
SIN. TRANS.
PARS SIGMOID.
Figs. 481 to 488. — Profile drawings of the dural veins showing principal stages in their development in human
embryos from 4 mm. to birth. It is of particular interest to notice their adaptation to the growth and changes in the
form of the central nervous system. Fig. 481, 4 mm. ; Fig. 482, 14 mm. ; Fig. 483, 18 mm. ; Fig. 484, 21 mm. ; Fig. 485,
35 mm. ; Fig. 486, 50 mm. crown-rump length; Fig. 487, 80 mm. crown-rump length; Fig. 488, adult. (After StreeterJ
524 ANGIOWGY
The external jugular vein at first drains the region behind the ear (posterior
auricular) and enters the primitive jugular as a lateral tributary. A group of veins
from the face and lingual region converge to form a common vein, the linguo-facial/
which also terminates in the primitive jugular. Later, cross communications
develop between the external jugular and the linguo-facial, with the result that
the posterior group of facial veins is transferred to the external jugular.
THE THORACIC CAVITY.
The heart and lungs are situated in the thorax, the walls of which afford them
protection. The heart lies between the two lungs, and is enclosed within a fibrous
bag, the pericardium, while each lung is invested by a serous membrane, the pleura.
The skeleton of the thorax, and the shape and boundaries of the cavity, have already
been described (page 117).
The Cavity of the Thorax. — The capacity of the cavity of the thorax does not
correspond with its apparent size externally, because (1) the space enclosed by
the lower ribs is occupied by some of the abdominal viscera; and (2) the cavity
extends above the anterior parts of the first ribs into the neck. The size of the
thoracic cavity is constantly varying during life with the movements of the ribs
and diaphragm, and with the 'degree of distention of the abdominal viscera.
From the collapsed state of the lungs as seen when the thorax is opened in the dead
body, it would appear as if the viscera only partly filled the cavity, but during
life there is no vacant space, that which is seen after death being filled up by the
expanded lungs.
The Upper Opening of the Thorax.^ — The parts which pass through the upper
opening of the thorax are, from before backward, in or near the middle line, the
Sternohyoideus and Sternothyreoideus muscles, the remains of the thymus, the
inferior thyroid veins, the trachea, esophagus, thoracic duct, and the Longus
colli muscles; at the sides, the innominate artery, the left common carotid, left
subclavian and internal mammarv arteries and the costocervical trunks, the
innominate veins, the vagus, cardiac, phrenic, and sympathetic nerves, the greater
parts of the anterior divisions of the first thoracic nerves, and the recurrent nerve
of the left side. The apex of each lung, covered by the pleura, also projects
through this aperture, a little above the level of the sternal end of the first rib.
The Lower Opening of the Thorax. — The lower opening pf the thorax is wider
transversely than from before backward. It slopes obliquely downward and back-
ward, so that the thoracic cavity is much deeper behind than in front. The dia-
phragm (see page 404) closes the opening and forms the floor of the thorax. The
floor is flatter at the center than at the sides, and higher on the right side than on
the left; in the dead body the right side reaches the level of the upper border of
the fifth costal cartilage, while the left extends only to the corresponding part
of the sixth costal cartilage. From the highest point on each side the floor slopes
suddenly downward to the costal and vertebral attachments of the diaphragm;
this slope is more marked behind than in front, so that only a narrow space is left
between the diaphragm and the posterior wall of the thorax.
THE PERICARDIUM.
The pericardium (Fig. 489) is a conical fibro-serous sac, in which the heart and
the roots of the great vessels are contained. It is placed behind the sternum and
the cartilages of the third, fourth, fifth, sixth, and seventh ribs of the left side,
in the mediastinal cavity.
Lewis, American Journa of Anatomy, February, 1909, No. 1, vol. ix.
THE PERICARDIUM
525
In front, it is separated from the anterior wall of the thorax, in the greater part
of its extent, by the lungs and pleiirse ; but a small area, somewhat variable in size,
and usually corresponding with the left half of the lower portion of the body of
the sternum and the medial ends of the cartilages of the fourth and fifth ribs of
the left side, comes into direct relationship with the chest wall. The lower extrem-
ity of the thymus, in the child, is in contact with the front of the upper part of
the pericardium. Behind, it rests upon the bronchi, the esophagus, the descending
thoracic aorta, and the posterior part of the mediastinal surface of each lung.
Laterally, it is covered by the pleurae, and is in relation with the mediastinal sur-
faces of the lungs; the phrenic nerve, with its accompanying vessels, descends
between the pericardium and pleura on either side.
R. common carotid a.
R, subclavian a
L. common carotid a.
L. subclavian a.
Cut edges of serous
'pericardimii
Sup. vena cava
R. pulmonary
veins
L. pulmoTuiry veins
Fig. 489. — Posterior wall of the pericardial sac, showing the lines of reflection of the serous pericardium
on the great vessels.
Structure of the Pericardiiun. — Although the pericardium is usually described as a single sac,
an examination of its structure shows that it consists essentially of two sacs intimately connected
with one another, but totally different in structure. The outer sac, known as the fibrous peri-
cardium, consists of fibrous tissue. The inner sac, or serous pericardium, is a deUcate mem-
brane which lies within the fibrous sac and lines its walls; it is composed of a single layer of
526 ANGIOLOGY
flattened cells resting on loose connective tissue. The heart invaginates the wall of the serous
sac from above and behind, and practically obliterates its cavity, the space being merely a
potential one.
The fibrous pericardium forms a flask-shaped bag, the neck of which is closed by its fusion
with the external coats of the great vessels, while its base is attached to the central tendon and
to the muscular fibers of the left side of the diaphragm. In some of the lower mammals the
base is either completely separated from the diaphragm or joined to it by some loose areolar
tissue; in man much of its diaphragmatic attachment consists of loose fibrous tissue which can
be readily broken downi, but over a small area the central tendon of the diaphragm and the
pericardium are completely fused. Above, the fibrous pericardium not only blends with the
external coats of the great vessels, but is continuous with the pretracheal laxev of the deep cervical
fascia. By means of these upper and lower connections it is securely anchored within the thoracic
cavity. It is also attached to the posterior surface of the sternum by the superior and inferior
stemopericardiac ligaments; the upper passing to the manubrium, and the lower to the xiphoid
process.
The vessels receiving fibrous prolongations from this membrane are: the aorta, the superior
vena cava, the right and left pulmonar}^ arteries, and the four pulmonary veins. The inferior
vena cava enters the pericardium through the central tendon of the diaphragm, and receives
no covering from the fibrous layer.
The serous pericardium is, as already stated, a closed sac which lines the fibrous pericardium
and is invaginated by the heart; it therefore consists of a visceral and a parietal portion. The
visceral portion, or epicardium, covers the heart and the great vessels, and from the latter is
continuous with the parietal layer which lines the fibrous pericardium. The portion which
covers the vessels is arranged in the form of two tubes. The aorta and pulmonary artery are
enclosed in one tube, the arterial mesocardium. The superior and inferior vence cavoe and the
four puhnonary veins are enclosed in a second tube, the venous mesocardium, the attachment
of which to the parietal layer presents the shape of an inverted U. The cul-de-sac enclosed between
the hmbs of the U Hes behind the left atrium and is known as the oblique sinus, while the passage
between the venous and arterial niesocardia — i. e., between the aorta and pulmonary artery in
front and the atria behind — is termed the transverse sinus.
The Ligament of the Left Vena Cava. — Between the left pulmonarj' artery and subjacent
pulmonary vein is a triangular fokl of the serous pericardium; it is known as the ligament of the
left vena cava (vestigial fold of Marshall). It is formed by the dupUcature of the serous layer
over the remnant of the lower part of the left superior vena cava (duct of Cuvier), which becomes
obhterated diu-ing fetal life, and remains as a fibrous band stretching from the highest left inter-
costal vein to the left atrium, where it is continuous with a small vein, the vein of the left atrium
(oblique vein of Marshall), which opens into the coronary sinus.
The arteries of the pericardium are derived from the internal mammary and its musculo-
phrenic branch, and from the descending thoracic aorta.
The nerves of the percardium are derived from the vagus and phrenic nerves, and the sj'mpa-
thetic trunks,
THE HEART (COR).
The heart is a hollow muscular organ of a somewhat conical form; it lies between
the lungs in the middle mediastinum and is enclosed in the pericardium (Fig. 490).
It is placed obliquely in the chest behind the body of the sternum and adjoining
parts of the rib cartilages, and projects farther into the left than into the right
half of the thoracic cavity, so that about one-third of it is situated on the right
and two-thirds on the left of the median plane.
Size. — The heart, in the adult, measures about 12 cm. in length, 8 to 9 cm. in
breadth at the broadest part, and 6 cm. in thickness. Its weight, in the male,
varies from 280 to 340 grams; in the female, from 230 to 280 grams. The heart
continues to increase in weight and size up to an advanced period of life; this
increase is more marked in men than in women.
Component Parts. — As has already been stated (page 497), the heart is sub-
divided by septa into right and left halves, and a constriction subdivides each
half of the organ into two cavities, the upper cavity being called the atrium, the
lower the ventricle. The heart therefore consists of four chambers, viz., right and
left atria, and right and left ventricles.
The division of the heart into four cavities is indicated on its surface by grooves.
The atria are separated from the ventricles by the coronary sulcus (auriculo-
THE HEART
527
ventricular groove); this contains the trunks of the nutrient vessels of the heart,
and is deficient in front, where it is crossed by the root of the pulmonary artery.
The interatrial groove, separating the two atria, is scarcely marked on the posterior
surface, while anteriorly it is hidden by the pulmonary artery and aorta. The
ventricles are separated by two grooves, one of which, the anterior longitudinal
sulcus, is situated on the sternocostal surface of the heart, close to its left margin,
the other posterior longitudinal sulcus, on the diaphragmatic surface near the right
margin; these grooves extend from the base of the ventricular portion to a notch,
the incisura apicis cordis, on the acute margin of the heart just to the right of the
apex.
Cut edge of pericardium
Fig. 490. — Front view of heart and lungs.
The base {basis cordis) (Fig. 491), directed upward, backward, and to the right,
( is separated from the fifth, sixth, seventh, and eighth thoracic vertebrae by the
^ esophagus, aorta, and thoracic duct. It is formed mainly by the left atrium,
I and, to a small extent, by the back part of the right atrium. Somewhat quadri-
• lateral in form, it is in relation above with the bifurcation of the pulmonary artery,
and is bounded below by the posterior part of the coronary sulcus, containing the
coronary sinus. On the right it is limited by the sulcus terminalis of the right
atrium, and on the left by the ligament of the left vena cava and the oblique vein
of the left atrium. The four pulmonary veins, two on either side, open into the
left atrium, while the superior vena cava opens into the upper, and the anterior
vena cava into the lower, part of the right atrium.
The Apex (apex cordis). — The apex is directed downward, forward, and to the
left, and is overlapped by the left lung and pleura: it lies behind the fifth left
intercostal space, 8 to 9 cm. from the mid-sternal line, or about 4 cm. below and
2 mm. to the medial side of the left mammary papilla.
528
ANGIOLOGY
The sternocostal surface (Fig. 492) is directed forward, upward, and to the left.
Its lower part is convex, formed chiefly by the right ventricle, and traversed near
its left margin by the anterior longitudinal sulcus. Its upper part is separated from
the lower by the coronary sulcus, and is formed by the atria; it presents a deep
concavity (Fig. 494), occupied by the ascending aorta and the pulmonary artery.
The diaphragmatic surface (Fig. 491), directed downward and slightly backward,
is formed by the ventricles, and rests upon the central tendon and a small part of
the left muscular portion of the diaphragm. It is separated from the base by
the posterior part of the coronary sulcus, and is traversed obliquely by the posterior
longitudinal sulcus.
The right margin of the heart is long, and is formed by the right atrium above
and the right ventricle below. The atrial portion is rounded and almost vertical;
it is situated behind the third, fourth, and fifth right costal cartilages about
Azygos vein
Left pulmonary veins
Oblique vein ofleftatrium
Great cardiac vein
Left marginal vein
Right pulmonary
veins
^^ Small cardiac vein
Posterior vein of left ventricle
Middle cardiac vein
Fig. 491. — Base and diaphragmatic surface of heart.
1.25 cm. from the margin of the sternum. The ventricular portion, thin and sharp,
is named the acute margin; it is nearly horizontal, and extends from the sternal
end of the sixth right costal cartilage to the apex of the heart.
The left or obtuse margin is shorter, full, and rounded: it is formed mainly by
the left ventricle, but to a slight extent, above, by the left atrium. It extends
from a point in the second left intercostal space, about 2.5 mm. from the sternal
margin, obliquely downward, with a convexity to the left, to the apex of the heart.
Right Atrium {atrium dextrum; right auricle). — The right atrium is larger than
the left, but its walls are somewhat thinner, measuring about 2 mm.; its cavity
is capable of containing about 57c.c. It consists of two parts: a principal cavity,
or sinus venarum, situated posteriorly, and an anterior, smaller portion, the auricula.
Sinus Venarum {sinus venosus). — The sinus venarum is the large quadrangular
cavity placed between the two vense cavse. Its walls, which are extremely thin,
\'^
THE HEART
529
are connected below with the right ventricle, and medially with the left atrium,
but are free in the rest of their extent.
Auricula (auricula dextra; right auricular appendix). — The auricula is a small
conical muscular pouch, the margins of which present a dentated edge. It projects
from the upper and front part of the sinus forward and toward the left side, over-
lapping the root of the aorta.
Ant. desc. branch of left
coronary artery
/
Right coronary
artery
Fio. 492. — Sternocostal surface of heart.
The separation of the auricula from the sinus venarum is indicated externally
by a groove, the terminal sulcus, which extends from the front of the superior vena
cava to the front of the inferior vena cava, and represents the line of union of the
sinus venosus of the embr\'o with the primitive atrium. On the inner wall of the
atrium the separation is marked by a vertical, smooth, muscular ridge, the terminal
crest. Behind the crest the internal surface of the airium is smooth, while in front
of it the muscular fibers of the wall are raised into parallel ridges resembling the
teeth of a comb, and hence named the musculi pectinati.
Its interior (Fig. 493) presents the following parts for examination:
Openings
Superior vena cava.
Inferior vena cava.
Coronary sinus.
Foramina venarum
minimarum.
Atrioventricular.
Valves
J Valve of the inferior vena cava.
1 Valve of the coronary sinus.
Fossa ovalis.
Limbus fossae ovalis.
Intervenous tubercle.
Musculi pectinati.
Crista terminalis.
The superior vena cava returns the blood from the upper half of the body, and
opens into the upper and back part of the atrium, the direction of its orifice being
downward and forward. Its opening has no valve.
34
530
ANGWLOGY
The inferior vena cava, larger than the superior, returns the blood from the
lower half of the body, and opens into the lowest part of the atrium, near the
atrial septum, its orifice being directed upward and backward, and guarded by
a rudimentary valve, the valve of the inferior vena cava (Eustachian valve). The
blood entering the atrium through the superior vena cava is directed downward
and forward, i. e., toward the atrioventricular orifice, while that entering through
the inferior vena cava is directed upward and backward, toward the atrial septum.
This is the normal direction of the two currents in fetal life.
The coronary sinus opens into the atrium, between the orifice of the inferior
vena cava and the atrioventricular opening. It returns blood from the substance
of the heart and is protected by a semicircular valve, the valve of the coronary
sinus {valve of Thebesius).
Pulmonary valve
Opening of sup. vena
cava _ ^l-
Crista terminalis —til
Atrial septum
Limbus fossce ovalis
Opening of coronary
sinus
Opening of inf. vena
cava
Ant. cusp of tricuspid
valve
Chord CB tcndineoB
Papillary
/ muscles
Valve of inf. vena cava
Valve of coronary sinus
FiQ. 493. — Interior of right side of heart.
The foramina venarum minimarum (Joramina. Thehesii) are the orifices of minute
veins {ven(p cordis minima'), which return blood directly from the muscular sub-
stance of the heart.
The atrioventricular opening (tricuspid orifice) is the large oval aperture of com-
munication between the atrium and the ventricle; it will be described with the
right ventricle.
The valve of the inferior vena cava (vahula venae cava' inferioris [Eustachii];
Eustachian valve) is situated in front of the orifice of the inferior vena cava. It
is semilunar in form, its convex margin being attached to the anterior margin
of the orifice; its concave margin, which is free, ends in two cornua, of which
the left is continuous with the anterior edge of the limbus fossie ovalis while
the right is lost on the wall of the atrium. The valve is formed by a duplicature
of the lining membrane of the atrium, containing a few muscular fibers, hi the
fetus this valve is of large size, and serves to direct the blood from the inferior
vena cava, through the foramen ovale, into the left atrium. In the adult it occa-
sionally persists, and may assist in preventing the reflux of blood into the inferior
vena cava; more commonly it is small, and may present a cribriform or filamentous
appearance; sometimes it is altogether wanting.
THE HEART 531
The valve of the coronary sinus {valvula sinus coronarii [Thebesii]; Thebesian
valve) is a semicircular fold of the lining membrane of the atrium, at the orifice of
the coronary sinus. It prevents the regurgitation of blood into the sinus during the
contraction of the atrium. This valve mav be double or it mav be cribriform.
The fossa ovalis is an oval depression on the septal wall of the atrium, and corre-
sponds to the situation of the foramen ovale in the fetus. It is situated at the lower
part of the septum, above and to the left of the orifice of the inferior vena cava.
The limbus fossae ovalis (ayiniilus ovalis) is the prominent oval margin of the fossa
ovalis. It is most distinct above and at the sides of the fossa; below, it is deficient.
A small slit-like valvular opening is occasionally found, at the upper margin of
the fossa, leading upward beneath the limbus, into the left atrium ; it is the remains
of the fetal aperture between the two atria.
The intervenous tubercle (tuherculum intervenosiim; tubercle of Lower) is a small
projection on the posterior wall of the atrium, above the fossa ovalis. It is distinct
in the hearts of quadrupeds, but in man is scarcely visible. It was supposed by
Lower to direct the blood from the superior vena cava toward the atrioventricular
opening.
Right Ventricle (ventriculus dexter). — The right ventricle is triangular in form,
and extends from the right atrium to near the apex of the heart. Its antero-
superior surface is rounded and convex, and forms the larger part of the sterno-
costal surface of the heart. Its under surface is flattened, rests upon the dia-
phragm, and forms a small part of the diaphragmatic surface of the heart. Its
posterior wall is formed by the ventricular septum, which bulges into the right
ventricle, so that a transverse section of the cavity presents a semilunar outline.
Its upper and left angle forms a conical pouch, the conus arteriosus, from which
the pulmonary artery arises. A tendinous band, which may be named the tendon
of the conus arteriosus, extends upward from the right atrioventt».^ilir fibrous
ring and connects the posterior surface of the conus arteriosus to the aoirta. The
wall of the right ventricle is thinner than that of the left, the proportion betwet*;!
them being as 1 to 3; it is thickest at the base, and gradually becomes thinnei*
toward the apex. The cavity equals in size that of the left ventricle, and is
capable of containing about 85 c.c. \
Its interior (Fig. 493) presents the following parts for examination: \
^ . (Right atrioventricular. Vl- (Tricuspid.
penmgs tpyjujQj^ary artery. iPulmonary.
Trabecule carneaj. Chordse tendinea?.
The right atrioventricular orifice is the large oval aperture of communication
between the right atrium and ventricle. Situated at the base of the ventricle,
it measures about 4 cm. in diameter and is surrounded by a fibrous ring, covered
by the lining membrane of the heart; it is considerably larger than the correspond-
ing aperture on the left side, being sufficient to admit the ends of four fingers
It is guarded by the tricuspid valve.
The opening of the pulmonary artery is circular in form, and situated at the
summit of the conus arteriosus, close to the ventricular septum. It is placed above
and to the left of the atrioventricular opening, and is guarded by the pulmonary
semilunar valves.
The tricuspid valve {valvula tricuspidalis) (Figs. 493, 495) consists of three some-
what triangular cusps or segments. The largest cusp is interposed between the
atrioventricular orifice and the conus arteriosus and is termed the anterior or infundib-
ular cusp. A second, the posterior or marginal cusp, is in relation to the right margin
of the ventricle, and a third, the medial or septal cusp, to the ventricular septum.
They are formed b}- duplicatures of the lining membrane of the heart, strengthened
S
532
ANGIOLOGY
by intervening layers of fibrous tissue: their central parts are thick and strong,
their marginal portions thin and translucent, and in the angles between the latter
small intermediate segments are sometimes seen. Their bases are attached to a
fibrous ring surrounding the atrioventricular orifice and are also joined to each other
so as to form a continuous annular membrane, while their apices project into the
ventricular cavity. Their atrial surfaces, directed toward the blood current from
the atrium, are smooth; their ventricular surfaces, directed toward the wall of the
ventricle, are rough and irregular, and, together with the apices and margins of
the cusps, give attachment to a number of delicate tendinous cords, the chordae
tendineae.
Right auricula
Left
auricula
Eight
atrium
Jt pulmonary veins
Fia. 494. — Heart seen from above
Sight pulmonary
veins
Fig. 495.-
-Base of ventricles exposed by removal
of the atria.
The trabeculse cameae (columrur carnecr) are rounded or irregular muscular
columns which project from the whole of the inner surface of the ventricle, with
the exception of the conus arteriosus. They are of three kinds: some are attached
along their entire length on one side and merely form prominent ridges, others
are fixed at their extremities but free in the middle, while a third set {muscidi
papillares) are continuous by their bases with the wall of the ventricle, while their
apices give origin to the chordiv tendineiie which pass to be attached to the seg-
ments of the tricuspid valve. There are two papillary muscles, anterior and pos-
terior: of these, the anterior is the larger, and its chorda? tendinccT are connected
with the anterior and posterior cusps of the valve: the posterior papillary muscle
sometimes consists of two or three parts; its chordae tendineffi are connected
. with the posterior and medial cusps. In addition to these, some chorda? tendineee
spring directly from the ventricular septum, or from small papillary eminences on it,
and pass to the anterior and medial cusps. A muscular band, well-marked in sheep
and some other animals, frequently extends from the base of the anterior papillary
muscle to the ventricular septum. From its attachments it may assist in preventing
overdistension of the ventricle, and so has been named the moderator band.
The pulmonary semilunar valves (Fig. 494) are three in number, two in front
and one behind, formed by duplicatures of the lining membrane, strengthened
by fibrous tissue. They are attached, by their convex margins, to the wall of the
artery, at its junction with the ventricle, their free borders being directed upward
into the lumen of the vessel. The free and attached margins of each are strength-
THE HEART
533
ened by tendinous fibers, and the former presents, at its middle, a thickened nodule
(corpus Amntii). From this nodule tendinous fibers radiate through the segment
to its attached margin, but are absent from two narrow crescentic portions, the
lunulas, placed one on either side of the nodule immediately adjoining the free
margin. Between the semilunar valves and the wall of the pulmonary artery are
three pouches or sinuses {sinuses uf Valsalva).
Left Atrium {atrium sinistum; left auricle) .—The left atrium is rather smaller
than the right, but its walls are thicker, measuring about 3 mm.; it consists, like
the right, of two parts, a principal cavity and an auricula.
The principal cavity is cuboidal in form, and concealed, in front, by the pul-
monary artery and aorta; in front and to the right it is separated from the right
atrium by the atrial septum; opening into it on either side are the two pulmonary
veins.
Auricula {auricula sinistra; left auricular appendix).— The auricula is somewhat
constricted at its junction with the principal cavity ; it is longer, narrower, and more
curved than that of the right side, and its margins are more deeply indented. It
is directed forward and toward the right and overlaps the root of the pulmonary
artery.
Fig. 496. — Interior of left side of heart.
The interior of the left atrium (Fig. 490) presents the following parts for
examination :
Openings of the four pulmonary veins.
Left atrioventricular opening.
Musculi pectinati.
The pulmonary veins, four in number, open into the upper part of the posterior
surface of the left atrium — two on either side of its middle line: they are not
provided with valves. The two left veins frequently end by a common opening.
The left atrioventricular opening is the aperture between the left atrium and
ventricle, and is rather smaller than the corresponding opening on the right side.
534
ANGIOLOGY
The musculi pectinati, fewer and smaller than in the right auricula, are confined
to the inner surface of the auricula.
On the atrial septum may be seen a lunated impression, bounded below by a
crescentic ridge, the concavity of which is turned upward. The depression is
just above the fossa ovalis of the right atrium.
Left Ventricle {ventriculus sinister). — The left ventricle is longer and more conical
in shape than the right, and on transverse section its concavity presents an oval
or nearly circular outline. It forms a small part of the sternocostal surface and a
considerable part of the diaphragmatic surface of the heart; it also forms the apex
of the heart. Its walls are about three times as thick as those of the right ventricle.
Its interior (Fig. 49G) presents the following parts for examination :
^ . (Left atrioventricular.
Openmgs ^^^^^.^
Trabecule carnese.
Y 1 . (Bicuspid or Mitral.
lAortic.
Chord* tendinese.
The left atrioventricular opening {mitral orifice) is placed below and to the left
of the aortic orifice. It is a little smaller than the corresponding aperture of the
opposite side, admitting only two fingers. It is surrounded by a dense fibrous ring,
covered by the lining membrane of the heart, and is guarded by the bicuspid or
ipitral valve.
Aortic sinus Left post.
Nodulus ^'""^"^
Lunula
Origins of coronary arteries
Right post, valve
Ant, valve
Fig. 497. — Aorta laid open to show the semilunar valves.
The aortic opening is a circular aperture, in front and to the right of the atrio-
ventricular, from which it is separated by, the anterior cusp of the bicuspid valve.
Its orifice is guarded by the aortic semilunar valves. The portion of the ventricle
immediately below the aortic orifice is termed the aortic vestibule, and possesses
fibrous instead of muscular walls.
The bicuspid or mitral valve (valvula bicuspidalis [metralis]) (Figs. 495, 496) is
attached to the circumference of the left atrioventricular orifice in the same way
that the tricuspid valve is on the opposite side. It consists of two triangular cusps,
formed by duplicatures of the lining membrane, strengthened by fibrous tissue,
and containing a few muscular fibers. The cusps are of unequal size, and are larger,
thicker, and stronger than those of the tricuspid valve. The larger cusp is placed
in front and to the right between the atrioventricular and aortic orifices, and is
known as the anterior or aortic cusp ; the smaller or posterior cusp is placed behind
and to the left of the opening. Two smaller cusps are usually found at the angles
of junction of the larger. The cusps of the bicuspid valve are furnished with chordae
tendineae, which are attached in a manner similar to those on the right side ; they
are, however, thicker, stronger, and less numerous.
THE HEART
535
The aortic semilunar valves (Figs. 494, 497) are three in number, and surround
the orifice of the aorta; two are anterior (right and left) and one posterior. They
are similar in structure, and in their mode of attachment, to the pulmonary semi-
lunar valves, but are larger, thicker, and stronger; the lunula? are more distinct,
and the noduli or corpora xVrantii thicker and more prominent. Opposite the valves
the aorta presents slight dilatations, the aortic sinuses (sinuses of Valsalva), which
are larger than those at the origin of the pulmonary artery.
The trabecule carnese are of three kinds, like those upon the right side, but
they are more numerous, and present a dense interlacement, especially at the
apex, and upon the posterior wall of the ventricle. The musculi papillares are two
in number, one being connected to the anterior, the other to the posterior wall;
they are of large size, and end in rounded extremities from which the chordae
tendinese arise. The chordae tendinese from each papillary muscle are connected
to both cusps of the bicuspid valve.
Left auricula
Inferior
vena cava
Membranous
septutn
Muscul i
pectinati
Aartiz valve
Papillary
muscles
Anterior papillary musde
Fig. 498. — Section of the heart showing the ventricular septum.
Ventricular Septum [septum ventriculorum; interventricular septum) (Fig. 498). —
The ventricular septum is directed obliquely backward and to the right, and is
curved with the convexity toward the right ventricle: its margins correspond
with the anterior and posterior longitudinal sulci. The greater portion of it is
thick and muscular and constitutes the muscular ventricular septum, but its upper
and posterior part, which separates the aortic vestibule from the lower part of
the right atrium and upper part of the right ventricle, is thin and fibrous, and is
termed the membranous ventricular septum. An abnormal communication may
exist between the ventricles at this part owing to defective development of the
membranous septum.
Structure. — The heart consists of muscular fibers, and of fibrous rings which serve for their
attachment. It is covered by the visceral layer of the serous pericardium (epicardium), and
lined by the endocardium. Between these two membranes is the muscular wall or myocardium.
The endocardiiun is a thin, smooth membrane which lines and gives the ghstening appear-
536
ANGIOLOGY
ance to the inner surface of the heart; it assists in forming the valves b\' its reduplications, and
is continuous with the Uning membrane of the large bloodvessels. It consists of connective
tissue and elastic fibers, and is attached to the muscular structure by loose elastic tissue which
contains bloodvessels and nerves; its free surface is covered by endothehal cells.
The fibrous rings surround the atrioventricular and arterial orifices, and are stronger upon
the left than on the right side of the heart. The atrioventricular rings serve for the attachment
of the muscular fibers of the atria and ventricles, and for the attachment of the bicuspid and
tricuspid valves. The left atrioventricular ring is closely connected, bj' its right margin, with
the aortic arterial ring; between these and the right atrioventricular ring is a triangular mass of
fibrous tissue, the trigonum fibrosum, which represents the os cordis seen in the heart of some of
the larger animals, as the ox and elephant. Lasth', there is the tendinous band, already referred
to, the posterior surface of the conus arteriosus.
The fibrous rings sm-roimding the arterial orifices serve for the attachment of the great vessels
and semUtmar valves. Each ring receives, by its ventricular margin, the attachment of some
of the muscular fibers of the ventricles; its opposite margin presents three deep semicircular
notches, to which the middle coat of the artery is firmly fixed. The attachment of the artery
to its fibrous ring is strengthened by the external coat and serous membrane externalh', and
by the endocardium internalh'. From the margins of the semicircular notches the fibrous structm^e
of the ring is continued into the segments of the valves. The middle coat of the artery in this
situation is thin, and the vessel is dilated to form the sinuses of the aorta and pulmonary arterj-.
(
i
^m« ^^^
%^fe=
B
Fig. 499. — Anastomosing muscular fibers of the heart seen
in a longitudinal section. On the right the limits of the
separate cells with their nuclei are exhibited somewhat dia-
grammaticallj'.
Fig. 500. — Purkinje's fibers from the sheep's
heart. .1. In longitudinal section. B. In
transverse section.
Cardiac Muscular Tissue. — The fibers of the heart difYer very remarkably from those of other
striped muscles. They are smaller by one-third, and their transverse strite are by no means so
well-marked. They show faint longitudinal striation. The fibers are made up of distinct quad-
rangular cells, joined end to end so as to form a syncytium (Fig. 499). Each cell contains a clear
oval nucleus, situated near its center. The extremities of the cells have a tendency to branch or
di\-ide, the subdivisions miiting with offsets from other cells, and thus producing an anastomosis
of the fibers. The connective tissue between the bimdles of fibers is much less than in ordinary
striped muscle, and no sarcolemma has been proved to exist.
Purkinje Fibers (Fig. 500). — Between the endocardiimi and the ordinary cardiac muscle are
fomid, imbedded in a small amount of connective tissue, peculiar fibers known as Purkinje fibers.
Thej- are fotind in certain mammals and in birds, and can be best seen in the sheep's heart, where
THE HEART 537
they form ;i considerable portion of the moderator band and also appear as gelatinous-looking
strands on the inner walls of the atria and ventricles. They also occur in the human heart asso-
ciated with the terminal distributions of the bundle of His. The fibers are very much larger in
size than the cardiac cells and differ from them in several ways. In longitudinal section they are
quadrilateral in shape, being about twice as long as they are broad. The central portion of each
fiber contains one or more nuclei and is made up of granular protoplasm, with no indication of
Ptriations, while the peripheral portion is clear and has cUstinct transverse striations. The fibers
are intimately connected with each other, possess no definite sarcolcmma, and do not branch.
The muscular structure of the heart consists of bands of fibers, which present an exceedingly
intricate interlacement. They comprise (a) the fibers of the atria, (6) the fibers of the ventricles,
and (c) the atrioventricular bundle of His.
The fibers of the atria are arranged in two layers — a superficial, common to both cavities, and
a deep, proper to each. The superficial fibers are most distinct on the front of the atria, across
the bases of which they run in a transverse direction, forming a thin and incomplete layer. Some
of these fibers run into the atrial septum. The deep fibers consist of looped and annular fibers.
The looped fibers pass upward over each atrium, being attached by their two extremities to the
corresponding atrioventricular ring, in front and behind. The an?iular fibers surround the auriculae,
and form annular bands around the terminations of the veins and around the fossa ovalis.
The fibers of the ventricles are arranged in a complex manner, and various accounts have
been given of their course and connections; the following description is based on the work of
McCallum.i They consist of superficial and deep layers, all of which, with the exception of
two, are inserted into the papillary muscles of the ventricles. The superficial layers consist
of the following: (a) Fibers which spring from the tendon of the conus arteriosus and sweep
downward and toward the left across the anterior longitudinal sulcus and around the apex of
the heart, where they pass upward and inward to terminate in the papillary muscles of the left
ventricle; those arising from the upper half of the tendon of the conus arteriosus pass to the
anterior papillary muscle, those from the lower half to the posterior papillary muscle and the
papillary muscles of the septum. (6) Fibers which arise from the right atrioventricular ring and
run diagonall}' across the diaphragmatic surface of the right ventricle and around its right border
on to its costosternal sm'face, where they dip beneath the fibers just described, and, crossing the
anterior longitudinal sulcus, wind around the apex of the heart and end in the posterior papillary
muscle of the left ventricle, (c) Fibers which spring from the left atrioventricular ring, and,
crossing the posterior longitudinal sulcus, pass successively into the right ventricle and end in
its papillary muscles. The deep layers are three in number; they arise in the papillary muscles
of one ventricle and, curving in an S-shaped manner, turn in at the longitudinal sulcus and end
in the papillary muscles of the other ventricle. The layer which is most superficial in the right
ventricle hes next the lumen of the left, and vice versa. Those of the first layer almost encircle
the right ventricle and, crossing in the septum to the left, unite with the superficial fibers from
the right atrioventricular ring to form the posterior papillary muscle. Those of the second
layer have a less extensive com-se in the wall of the right ventricle, and a correspondingly greater
course in the left, where they join with the superficial fibers from the anterior half of the tendon
of the conus arteriosus to form the papillary muscles of the septum. Those of the third layer
pass almost entirely around the left ventricle and unite with the superficial fibers from the lower
half of the tendon of the conus arteriosus to form the anterior papillary muscle. Besides the
layers just described there are two bands which do not end in papiL'ar}' muscles. One springs
from the right atrioventricular ring and crosses in the atrioventricular septum; it then encircles
the deep layers of the left ventricle and ends in the left atrioventricular ring. The second band
is apparently confined to the left ventricle; it is attached to the left atrioventricular ring, and
encircles the portion of the ventricle adjacent to the aortic orifice.
The atrioventricular bundle of His iFig. 501), is the only direct muscular connection known to
exist between the atria and the ventricles. Its cells differ from ordinary cardiac muscle cells in
being more spindle-shaped. They are, moreover, more loosely arranged and have a richer vascu-
lar supply than the rest of the heart muscle. It arises in connection with two small collections of
spindle-shaped cells, the sinoatrial and atrioventricular nodes. The sinoatrial node is situated on
the anterior border of the opening of the superior vena cava ; from its strands of fusiform fibers run
under the endocardiiun of the wall of the atrium to the atrioventricular node. The atrioventricular
node lies near the orifice of the coronary sinus in the annular and septal fibers of the right atrium;
from it the atrioventricular bundle passes forward in the lower part of the membranous septum,
and divides into right and left fascicuh. These run down in the right and left ventricles, one on
either side of the ventricular septum, covered by endocardium. In the lower parts of the ventricles
they break up into numerous strands which end in the papillary muscles and in the ventricular
muscle generally. The greater portion of the atrioventricular bundle consists of narroWj somewhat
fusifgrm fibers, but its terminal strands are composed of Pm-kinje fibers.
1 Johns Hopkins Hospital Reports, vo
538
ANGIOLOGY
Dr. A. Morison^ has shown that in the sheep and pig the atrioventricular bundle "is a great
avenue for the transmission of nerves from the auricular to the ventricular heart; large and
numerous nerve trunks entering the bundle and coursing with it." From these, branches pass
off and form plexuses around groups of Purkinje cells, and from these plexuses fine fibrils go to
innervate individual cells.
Clinical and experimental evidence go to prove that this bundle conveys the impulse to sys-
tolic contraction from the atrial septum to the ventricles.
Fig. 501. — Scliematic representation of the atrioventricular bundle of His. The bundle, represented in red
originates near the orifice of the coronary sinus, undergoes slight enlargement to form a node, passes forward to
the ventricular septum, and divides into two limbs. The ultimate distribution cannot be completely shown in this
diagram.
Vessels and Nerves. — The arteries supplying the heart are the right and left coronary from
the aorta; the veins end in the right atrium.
The lymphatics end in the thoracic and right lymphatic ducts.
The nerves are derived from the cardiac plexus, which are formed partly from the vagi, and
partly from the sympathetic trunks. They are freely distributed both on the surface and in the
substance of the heart, the separate nerve filaments being furnished with small ganglia.
The Cardiac Cycle and the Actions of the Valves. — By the contractions of the
heart the blood is pumped through the arteries to all parts of the body. These
contractions occur regularly and at the rate of about seventy per minute. Each
wave of contraction or period of activity is followed by a period of rest, the two
periods constituting what is known as a cardiac cycle.
Each cardiac cycle consists of three phases, which succeed each other as follows:
(1) a short simultaneous contraction of both atria, termed the atrial systole, fol-
' Journai of Anatomy and Physiology, vol. xlvi.
PECULIARITIES IN THE VASCULAR SYSTEM OF THE FETUS 539
lowed, after a slight pause, by (2) a simultaneous, but more prolonged, contraction
of both ventricles, named the ventricular systole, and (3) a period of rest, during which
the whole heart is relaxed. The atrial contraction commences around the venous
openings, and sweeping over the atria forces their contents through the atrio-
ventricular openings into the ventricles, regurgitation into the veins being pre-
vented by the contraction of their muscular coats. When the ventricles contract,
the tricuspid and bicuspid valves are closed, and prevent the passage of the blood
back into the atria; the musculi papillares at the same time are shortened, and,
pulling on the chorda^ tendincfe, prevent the inversion of the valves into the atria.
As soon as the pressure in the ventricles exceeds that in the pulmonary artery and
aorta, the valves guarding the orifices of these vessels are opened and the blood is
driven from the right ventricle into the pulmonary artery and from the left into
the aorta. The moment the systole of the ventricles ceases, the pressure of the
blood in the pulmonary artery and aorta closes the pulmonary and aortic semilunar
valves to prevent regurgitation of blood into the ventricles, the valves remaining
shut until reopened by the next ventricular systole. During the period of rest the
tension of the tricuspid and bicuspid valves is relaxed, and blood is flowing from
the veins into the atria, being aspirated by negative intrathoracic pressure, and
slightly also from the atria into the ventricles. The average duration of a cardiac
cycle is about yt of a second, made up as follows :
Atrial systole, yV- Atrial diastole, yV.
Ventricular systole, ^. Ventricular diastole, y-g-.
Total systole, yy. Complete diastole, -y^-
The rhythmical action of the heart is muscular in origin^ — that is to say, the
heart muscle itself possesses the inherent property of contraction apart from any
nervous stimulation. The more embryonic the muscle the better is it able to initiate
and propagate the contraction wave; this explains why the normal systole of the
heart starts at the entrance of the veins, for there the muscle is most embryonic
in nature. At the atrioventricular junction there is a slight pause in the wave of
muscular contraction. To obviate this so far as possible a peculiar band of marked
embryonic type passes across the junction and so carries on the contraction wave
to the vpntricles. This band, composed of special fibers, is the atrioventricular
bundle of His (p. 537). The nerves, although not concerned in originating the
contractions of the heart muscle, play an important role in regulating their force
and frequency in order to subserve the physiological needs of the organism.
PECULIARITIES IN THE VASCULAR SYSTEM OF THE FETUS.
The chief peculiarities of the fetal heart are the direct communication between
the atria through the foramen ovale, and the large size of the valve of the inferior
vena cava. Among other peculiarities the following may be noted. (1) In early
fetal life the heart lies immediately below the mandibular arch and is relatively
large in size. As development proceeds it is gradually dra^^^l within the thorax, but
at first it lies in the middle line ; toward the end of pregnancy it gradually becomes
oblique in direction. (2) For a time the atrial portion exceeds the ventricular in
size, and the w^alls of the ventricles are of equal thickness : toward the end of fetal
life the ventricular portion becomes the larger and the wall of the left ventricle
exceeds that of the right in thickness. (3) Its size is large as compared with that
of the rest of the body, the proportion at the second month being 1 to 50, and at
birth, 1 to 120, while in the adult the average is about 1 to 160.
The foramen ovale, situated at the lower part of the atrial septum, forms a free
communication between the atria until the end of fetal life. A septum (septum
secundum) grows down from the upper wall of the atrium to the right of the primary
540 ANGIOLOGY
septum in which the foramen ovale is situated; shortly after birth it fuses with
the primary septum and the foramen ovale is obliterated.
The valve of the inferior vena cava serves to direct the blood from that vessel
through the foramen ovale into the left atrium.
The peculiarities in the arterial system of the fetus are the communication
between the pulmonary artery and the aorta by means of the ductus arteriosus,
and the continuation of the hypogastric arteries as the umbilical arteries to the
placenta.
The ductus arteriosus is a short tube, about 1.25 cm. in length at birth, and
of the diameter of a goose-quill. In the early condition it forms the continuation
of the pulmonary artery, and opens into the aorta, just beyond the origin of the
left subclavian artery; and so conducts the greater amount of the blood from the
right ventricle into the aorta. When the branches of the pulmonary artery have
become larger relatively to the ductus arteriosus, the latter is chiefly connected
to the left pulmonary artery.
The hypogastric arteries run along the sides of the bladder and thence upward
on the back of the anterior abdominal wall to the umbilicus; here they pass out
of the abdomen and are continued as the umbilical arteries in the umbilical cord
to the placenta. They convey the fetal blood to the placenta.
The peculiarities in the venous system of the fetus are the communications
established between the placenta and the liver and portal vein, through the umbil-
ical vein; and between the umbilical vein and the inferior vena cava through the
ductus venosus.
Fetal Circulation (Fig. 502). — The fetal blood is returned from the placenta to
the fetus by the umbilical vein. This vein enters the abdomen at the umbilicus,
and passes upward along the free margin of the falciform ligament of the liver to
the under surface of that organ, where it gives off two or three branches, one of
large size to the left lobe, and others to the lobus quadratus and lobus caudatus.
At the porta hepatis {transTerse fissure of the liver) it divides into two branches:
of these, the larger is joined by the portal vein, and enters the right lobe; the
smaller is continued upward, under the name of the ductus venosus, and joins
the inferior vena cava. The blood, therefore, which traverses the umbilical vein,
passes to the inferior vena cava in three different ways. A considerable quantity
circulates through the liver with the portal venous blood, before entering the
inferior vena cava by the hepatic veins; some enters the liver directly, and is
carried to the inferior cava by the hepatic veins; the remainder passes directly
into the inferior vena cava through the ductus venosus.
In the inferior vena cava, the blood carried by the ductus venosus and hepatic
veins becomes mixed with that returning from the lower extremities and abdominal
wall. It enters the right atrium, and, guided by the valve of the inferior vena
cava, passes through the foramen ovale into the left atrium, where it mixes with
a small quantity of blood returned from the lungs by the pulmonary veins. From
the left atrium it passes into the left ventricle; and from the left ventricle into the
aorta, by means of which it is distributed almost entirely to the head and upper
extremities, a small quantity being probably carried into the descending aorta.
From the head and upper extremities the blood is returned by the superior vena
cava to the right atrium, where it mixes with a small portion of the blood from the
inferior vena cava. P'rom the right atrium it descends into the right ventricle,
and thence passes into the pulmonary artery. The lungs of the fetus being inactive,
only a small quantity of the blood of the pulmonary artery is distributed to them
by the right and left pulmonary arteries, and returned by the pulmonary veins
to the left atrium : the greater part passes through the ductus arteriosus into the
aorta, where it mixes with a small quantity of the blood transmitted by the left
ventricle into the aorta. Through this vessel it descends, and is in part distributed
PECULIARITIES IN THE VASCULAR SYSTEM OF THE FETUS 541
to the lower extremities and the viscera of the abdomen and pelvis, but the greater
amount is conveyed by the umbilical arteries to the placenta.
From the preceding account of the circulation of the blood in the fetus the fol-
lowing facts will be evident: (1) The placenta serves the purposes of nutrition
^ J}tietu»
^Urloaua
Hypogastric arteries
Fig. 502.— Plan of the fetal circulation. In this plan the figured arrows represent the kind of blood, as well as the
direction which it takes in the vessles. Thus — arterial blood is figured > > ; venous blood, > > ; mixed
(arterial and venous) blood, > >.
and excretion, receiving the impure blood from the fetus, and returning it purified
and charged with additional nutritive material. (2) Nearly the whole of the blood
of the umbilical vein traverses the liver before entering the inferior vena cava;
hence the large size of the liver, especially at an early period of fetal life. (3) The
right atrium is the point of meeting of a double current, the blood in the inferior
542 ANGIOLOGY
vena cava being guided by the valve of this vessel into the left atrium, while that
in the superior vena cava descends into the right ventricle. At an early period
of fetal life it is highly probable that the two streams are quite distinct; for the
inferior vena cava opens almost directly into the left atrium, and the valve of the
inferior vena cava would exclude the current from the right ventricle. At a later
period, as the separation between the two atria becomes more distinct, it seems
probable that some mixture of the two streams must take place. (4) The pure
blood carried from the placenta to the fetus by the umbilical vein, mixed with the
blood from the portal vein and inferior vena cava, passes almost directly to the
arch of the aorta, and is distributed by the branches of that vessel to the head
and upper extremities. (5) The blood contained in the descending aorta, chiefly
derived from that which has already circulated through the head and limbs,
together with a small quantity from the left ventricle, is distributed to the
abdomen and lower extremities.
Changes in the Vascular System at Birth. — At birth, when respiration is estab-
lished, an increased amount of blood from the pulmonary artery passes through the
lungs, and the placental circulation is cut off. The foramen ovale is closed by about
the tenth day after birth: the valvular fold above mentioned adheres to the margin
of the foramen for the greater part of its circumference, but a slit-like opening is
left between the two atria above, and this sometimes persists.
The ductus arteriosus begins to contract immediately after respiration is estab-
lished, and is completely closed from the fourth to the tenth day; it ultimately
degenerates into an impervious cord, the ligamentum arteriosum, which connects
the left pulmonary artery to the arch of the aorta.
Of the hypogastric arteries, the parts extending from the sides of the bladder
to the umbilicus become obliterated between the second and fifth days after birth,
and project as fibrous cords, the lateral umbilical ligaments, toward the abdominal
cavity, carrying on them folds of peritoneum.
The umbilical vein and ductus venosus are completely obliterated between the
second and fifth days after birth; the former becomes the ligamentum teres, the
latter the ligamentum venosum, of the liver.
BIBLIOGRAPHY.
Bremer, J. L. : The Earliest Bloodvessels in Man, Am. Jour. Anat., 1914, xvi.
EvAxs, H. M.: On the Development of the Aorta^, Cardinal and Umbihcal Veins and Other
Bloodvessels of the Vertebrate Embryos from Capillaries, Anat. Rec, 1909, iii.
EvAXS, H. M.: The Development of the Vascular System, Keibel and Mall, Manual of
Human Embryologj-.
His, W.: Anatomie Menschlicheii Embryonen, Leipzig, 1880-85.
MacCallum, J. B.: On the Muscular Architecture and Growth of the Ventricles of the Heart,
Johns Hop. Hosp. Rep., 1900, ix. «
Mall, F. P.: A Study of the Structural Unit of the Liver, Am. Jour. Anat., 1906, v.
Mall, F. P. : On the Muscular Architecture of the Ventricles of the Human Heart, Am. Jour.
Anat., 1911, xi.
Mall, F. P.: The Development of the Internal Mammary and Deep Epigastric Arteries in
Man, Johns Hop. Hosp. Bulletin, 1898.
Stockard, C. R.: A Study of Wandering Mesenchymal Cells on the Living Yolk Sac and
Their Developmental Products: Chromatophores. Vascular Endothelium and Blood Cells, Am.
Jour. Anat., 1915, xviii.
Streeter, G. L.: The Development of the Venous Sinuses of the Dura Mater in the Human
Embryo, Am. Jour. Anat., 1915, xviii.
Thoma, R. : Text-book of General Pathology and Pathological Anatomy, Translated by Bruce,
London, 1896.
THE ARTERIES.
THE distribution of the systematic arteries is like a highly ramified tree, the
common trunk of which, formed by the aorta, commences at the left ventricle,
while the smallest ramifications extend to the peripheral parts of the body and the
contained organs. Arteries are found in all parts of the body, except in the hairs,
nails, epidermis, cartilages, and cornea ; the larger trunks usually occupy the most
protected situations, running, in the limbs, along the flexor surface, where they
are less exposed to injury.
There is considerable variation in the mode of division of the arteries : occasion-
ally a short trunk subdivides into several branches at the same point, as may be
observed in the celiac artery and the thyrocervical trunk: the vessel may give off
several branches in succession, and still continue as the main trunk, as is seen in
the arteries of the limbs; or the division may be dichotomous, as, for instance, when
the aorta divides into the two common iliacs.
A branch of an artery is smaller than the trunk from which it arises; but if an
artery divides into two branches, the combined sectional area of the two vessels
is, in nearly every instance, somewhat greater than that of the trunk; and the
combined sectional area of all the arterial branches greatly exceeds that of the
aorta; so that the arteries collectively may be regarded as a cone, the apex of
which corresponds to the aorta, and the base to the capillary system.
The arteries, in their distribution, communicate with one another, forming
what are called anastomoses, and these communications are very free between
the large as well as between the smaller branches. The anastomosis between trunks
of equal size is found w^here great activity of the circulation is requisite, as in the
brain ; here the two vertebral arteries unite to form the basilar, and the two ante-
rior cerebral arteries are connected by a short communicating trunk; it is also
found in the abdomen, where the intestinal arteries have very ample anastomoses
between their larger branches. In the limbs the anastomoses are most numerous
and of largest size around the joints, the branches of an artery above uniting
with branches from the vessels below. These anastomoses are of considerable in-
terest to the surgeon, as it is by their enlargement that a collateral circulation is
established after the application of a ligature to an artery. The smaller branches
of arteries anastomose more frequently than the larger; and between the smallest
twigs these anastomoses become so numerous as to constitute a close network
that pervades nearly every tissue of the body.
Throughout the body generally the larger arterial branches pursue a fairly
straight course, but in certain situations they are tortuous. Thus the external
maxillary artery in its course over the face, and the arteries of the lips, are extremely
tortuous to accommodate themselves to the movements of the parts. The uterine
arteries are also tortuous, to accommodate themselves to the increase of size which
the uterus undergoes during pregnancy.
The Pulmonary Artery (A. Pulmonalis) (Figs. 503, 504).
The pulmonary artery conveys the venous blood from the right ventricle of the
heart to the lungs. It is a short, wide vessel, about 5 cm. in length and 3 cm. in
(543)
544
ANGIOLOGY
diameter, arising from the conus arteriosus of the right ventricle. It extends
obhquely upward and backward, passing at first in front and then to the left
TranstJersus thoracis
Internal mammary vessel i
Left phrenic
nerve
Piilmormry pleura
Costal pleura
Sympathetic trunk J \J/ \ -^^UQos vein
Thoracic duct Vagus nerves
Fig. 503. — Transverse section of thorax, showing relations of pulmonary artery.
ANCE OF
AZYGOS
CH OF PUL-
RY ARTERY
Fig. 504. — Pulmonary vessels, seen in a dorsal view of the heart and lungs. The lungs have been pulled away from
the median line, and a part of the right lung has been cut away to display the air-ducts and bloodvessels.
THE ASCENDING AORTA 545
of the ascending aorta, as far as the under surface of the aortic arch, where it
divides, about the level of the fibrocartilage between the fifth and sixth thoracic
vertebra?, into right and left branches of nearly equal size.
Relations. — The whole of this vessel is contained within the pericardium. It is enclosed with
the ascending aorta in a single tube of the visceral layer of the serous pericardium, which is con-
tinued upward upon them from the base of the heart. The fibrous layer of the pericardium is
gradually lost upon the external coats of the two branches of the artery. In front, the pulmonary
artery is separated from the anterior end of the second left intercostal space by the pleura and
left lung, in addition to the pericardium; it rests at first upon the ascending aorta, and higher
up lies in front of the left atrium on a plane posterior to the ascending aorta. On either side of
its origin is the auricula of the corresponding atrium and a coronary artery, the left coronary
artery passing, in the first part of its course, behind the vessel. The superficial part of the cardiac
plexus hes above its bifurcation, between it and the arch of the aorta.
The right branch of the pulmonary artery (ramvs dexter a. pulmonalis), longer
and larger than the left, runs horizontally to the right, behind the ascending aorta
and superior vena cava and in front of the right bronchus, to the root of the right
lung, where it divides into two branches. The lower and larger of these goes to
the middle and lower lobes of the lung; the upper and smaller is distributed to the
upper lobe.
The left branch of the pulmonary artery (ramus sinister a. pulmonalis) , shorter
and somewhat smaller than the right, passes horizontally in front of the descending
aorta and left bronchus to the root of the left lung, w^here it divides into two
branches, one for each lobe of the lung.
Above, it is connected to the concavity of the aortic arch by the ligamentum
arteriosum, on the left of which is the left recurrent nerve, and on the right the
superficial part of the cardiac plexus. Below, it is joined to the upper left pul-
monary vein by the ligament of the left vena cava.
The terminal branches of the pulmonary arteries will be described with the
anatomy of the lungs.
THE AORTA.
The aorta is the main trunk of a series of vessels which convey the oxygenated
blood to the tissues of the body for their nutrition. It commences at the upper
part of the left ventricle, where it is about 3 cm. in diameter, and after ascending
for a short distance, arches backward and to the left side, over the root of the left
lung; it then descends within the thorax on the left side of the vertebral column,
passes into the abdominal cavity through the aortic hiatus in the diaphragm,
and ends, considerably diminished in size (about 1.75 cm. in diameter)^ opposite
the lower border of the fourth lumbar vertebra, by dividing into the right and left
common iliac arteries. Hence it is described in several portions, viz., the ascending
aorta, the arch of the aorta, and the descending aorta, which last is again divided into
the thoracic and abdominal aortse.
THE ASCENDING AORTA (AORTA ASCENDENS) (Fig. 505).
The ascending aorta is about 5 cm. in length. It commences at the upper part
of the base of the left ventricle, on a level with the lower border of the third costal
cartilage behind the left half of the sternum; it passes obliquely upward, forward,
and to the right, in the direction of the heart's axis, as high as the upper border
of the second right costal cartilage, describing a slight curve in its course, and being
situated, about 6 cm. behind the posterior surface of the sternum. At its origin
it presents, opposite the segments of the aortic valve, three small dilatations
called the aortic sinuses. At the union of the ascending aorta with the aortic arch
the caliber of the vessel is increased, owung to a bulging of its right wall. This
dilatation is termed the bulb of the aorta, and on transverse section presents a som.e-
35
546
ANGIOLOGY
what oval figure. The ascending aorta is contained within the pericardium, and
is enclosed in a tube of the serous pericardium, common to it and the pulmonary
artery.
Relations. — The ascending aorta is covered at its commencement by the trunk of the pul-
monary artery and the right auricula, and, higher up, is separated from the sternum by the
pericardium, the right pleura, the anterior margin of the right lung, some loose areolar tissue,
and the remains of the thymus; posteriorly, it rests upon the left atrium and right pulmonary
artery. On the right side, it is in j-elation with the superior vena cava and right atrium, the
former lying partly behind it ; on the left side, with the pulmonary artery.
Right vagtisX\\^-
Recurrent nerve ^\
n^rUi Gatti
Left rngus
Left phrenic
— Thoracic duct
Fig. 506.— Plan of the
branches.
Fig. 505. — The arch of the aorta, and its branches.
Branches. — The only branches of the ascending aorta are the two coronary
arteries which supply the heart; they arise near the commencement of the aorta
immediately above the attached margins of the semilunar valves.
The Coronary Arteries. — The Right Coronary Artery (a. coronaria [cordis] dextra)
arises from the right anterior aortic sinus. It passes at first between the conus
arteriosus and the right auricula and then runs in the right portion of the coronary
sulcus, coursing at first from the left to right and then on the diaphragmatic surface
of the heart from right to left as far as the posterior longitudinal sulcus, down
THE ARCH OF THE AORTA 547
which it is continued to the apex of the heart as the posterior descending branch.
It gives off a Uirge marginal branch which foHows the acute margin of the heart
and suppHes branches to both surfaces of the right ventricle. It also gives twigs
to the right atrium and to the part of the left ventricle which adjoins the
posterior longitudinal sulcus.
The Left Coronary Artery (a. coronaria [cordis] sinistra), larger than the right,
arises from the left anterior aortic sinus and divides into an anterior descending
and a circumflex branch. The anterior descending branch passes at first behind the
pulmonary artery and then comes forward between that vessel and the left auricula
to reach the anterior longitudinal sulcus, along which it descends to the incisura
apicis cordis; it gives branches to both ventricles. The circumflex branch follows
the left part of the coronary sulcus, running first to the left and then to the right,
reaching nearly as far as the posterior longitudinal sulcus; it gives branches to the
left atrium and ventricle. There is a free anastomosis between the minute
branches of the two coronar\' arteries in the substance of the heart.
Peculiarities. — These vessels occasionally arise by a common trunk, or their number may be
increased to three, the additional branch being of small size. More rarely, there are two addi-
tional branches.
THE ARCH OF THE AORTA (ARCUS AORT.ffi; TRANSVERSE
AORTA) (Fig. 505).
The arch of the aorta begins at the level of the upper border of the second sterno-
costal articulation of the right side, and runs at first upward, backward, and to the
left in front of the trachea ; it is then directed backward on the left side of the trachea
and finally passes downward on the left side of the body of the fourth thoracic
vertebra, at the lower border of which it becomes continuous with the descending
aorta. It thus forms two curvatures: one with its convexity upward, the other
with its convexity forward and to the left. Its upper border is usually about 2.5
cm. below the superior border to the manubrium sterni.
Relations. — The arch of the aorta is covered anteriorly by the pleursB and anterior margins
of the lungs, and by the remains of the thymus. As the vessel runs backward its left side is in
contact with the left lung and pleura. Passing downward on the left side of this part of the arch
are four nerves; in order from before backward these are, the left phrenic, the lower of the superior
cardiac branches of the left vagus, the superior cardiac branch of the left sympathetic, and the
trunk of the left vagus. As the last nerve crosses the arch it gives off its recurrent branch, which
hooks around below the vessel and then passes upward on its right side. The highest left inter-
costal vein runs obhquely upward and forward on the left side of the arch, between the phrenic
and vagus nerves. On the right are the deep part of the cardiac plexus, the left recurrent nerve,
the esophagus, and the thoracic duct; the trachea lies behind and to the right of the vessel.
Above are the innominate, left common carotid, and left subclavian arteries, which arise from
the convexity of the arch and are crossed close to their origins by the left innominate vein. Below
are the bifurcation of the pulmonary artery, the left bronchus, the hgamentum arteriosum, the
superficial part of the cardiac plexus, and the left recurrent nerve. As already stated, the liga-
mentum arteriosum connects the commencement of the left pulmonary artery to the aortic arch.
Between the origin of the left subclavian artery and the attachment of the ductus
arteriosus the lumen of the fetal aorta is considerably narrowed, forming what is
termed the aortic isthmus, while immediately beyond the ductus arteriosus the
vessel presents a fusiform dilation which His has named the aortic spindle- — the
point of junction of the two parts being marked in the concavity of the arch by an
indentation or angle. These conditions persist, to some extent, in the adult, where
His found that the average diameter of the spindle exceeded that of the isthmus
by 3 mm.
Distinct from this diffuse and moderate stenosis at the isthmus is the condition known as
coarctation of the aorta, or marked stenosis often amounting to complete obhteration of its lumen,
seen in adults and occurring at or near, oftenest a little below, the insertion of the ligamentum
548 ANGIOLOGY
arteriosum into the aorta. According to Bonnet^ this coarctation is never found in the fetus or
at birth, and is due to an abnormal extension of the peculiar tissue of the ductus into the aortic
wall, which gives rise to a simultaneous stenosis of both vessels as it contracts after birth — the
ductus is usually obUterated in these cases. An extensive collateral circulation is set up, by the
costocervicals, internal mammaries, and the descending branches of the transverse cervical
above the stenosis, and below it by the first four aortic intercostals, the pericardiaco-phrenics,
and the superior and inferior epigastrics.
Peculiarities. — The height to which the aorta rises in the thorax is usually about 2.5 cm.
below the upper border of the sternum; but it may ascend nearly to the top of the bone. Occa-
sionally it is found 4 cm., more rarely from 5 to 8 cm. below this point. Sometimes the aorta
arches over the root of the right lung (right aortic arch) instead of over that of the left, and passes
down on the right side of the vertebral column, a condition which is found in birds. In such cases
all the thoracic and abdominal A-iscera are transposed. Less frequently the aorta, after arching
over the root of the right lung, is directed to its usual position on the left side of the vertebral
column; this peculiarity is not accompanied by transposition of the viscera. The aorta occa-
sionally divides, as in some quadrupeds, into an ascending and a descending trunk, the former
of which is directed vertically upward, and subdivides into three branches, to supply the head
and upper extremities. Sometimes the aorta subdivides near its origin into two branches, which
soon reunite. In one of these cases the esophagus and trachea were found to pass through the
interval between the two branches; this is the normal condition of the vessel in the reptilia.
Branches (Figs. 505, 506). — The branches given off from the arch of the aorta
are three in number: the innominate, the left common carotid, and the left subclavian.
Peculiarities. — Position of the Branches. — The branches, instead of arising from the highest
part of the arch, may spring from the commencement of the arch or upper part of the ascending
aorta; or the distance between them at their origins may be increased or diminished, the most
frequent change in this respect being the approximation of the left carotid toward the innominate
artery.
The number of the primary branches may be reduced to one, or more commonly two; the left
carotid arising from the innominate artery; or (more rarely) the carotid and subclavian arteries
of the left side ai'ising from a left innominate artery. But the number may be increased to four,
from the right carotid and subclavian arteries arising directly from the aorta, the innominate
being absent. In most of these latter cases the right subclavian has been found to arise from the ■
left end of the arch; in other cases it is the second or third branch given off, instead of the first.
Another common form in which there are four primary branches is that in which the left vertebral
artery arises from the arch of the aorta between the left carotid and subclavian arteries. Lastly,,
the number of trunks from the arch may be increased to five or six; in these instances, the external
and internal carotids arise separately from the arch, the common carotid being absent on one or
both sides. In some few cases six branches have been found, and this condition is associated
with the origin of both vertebral arteries from the arch.
Number Usual, Arrangement Different. — When the aorta arches over to the right side, the
three branches have an arrangement the reverse of what is usual; the innominate artery is a left
one, and the right carotid and subclavian arise separately. In other cases, where the aorta takes
its usual course, the two carotids may be joined in a common trunk, and the subclavians arise
separately from the arch, the right subclavian generally arising from the left end of the arch.
In some instances other arteries spring from the arch of the aorta. Of these the most common
are the bronchial, one or both, and the thyreoidea ima; but the internal mammary and the inferior
thyroid have been seen to arise from this vessel. >
The Innominate Artery (A. Anonyma; Brachiocephalic Artery) (Fig. 505).
The innominate artery is the largest branch of the arch of the aorta, and is from
4 to 5 cm. in length. It arises, on a level with the upper border of the second
right costal cartilage, from the commencement of the arch of the aorta, on a plane
anterior to the origin of the left carotid; it ascends obliquely upward, backward,
and to the right to the level of the upper border of the right sternoclavicular
articulation, where it divides into the right common carotid and right subclavian
arteries.
Relations. — Anteriorly, it is separated from the manubrium sterni by the Sternoliyoideus and
Sternothyreoideus, the remains of the thymus, the left innominate and right inferior thyroid veins
which cross its root, and sometimes the superior cardiac branches of the right vagus. Posterior
' Rev. de M6d., Paris, 1903.
i
THE COMMON CAROTID ARTERY 549
to it is the trachea, which it crosses obliquely. On the right side are the right innominate vein,
the superior vena cava, the right phrenic nerve, and the pleura; and on the left side, the remains
of the thymus, the origin of the left common carotid artery, the inferior thjToid veins, aiid the
trachea.
Branches.— The innominate artery usually gives off no branches; but occasion-
ally a small branch, the thyreoidea ima, arises from it. Sometimes it gives oft" a
thymic or bronchial branch.
The thyreoidea ima (a. thyreoidea ima) ascends in front of the trachea to the
lower part of the thyroid gland, which it supplies. It varies greatly in size, and
appears to compensate for deficiency or absence of one of the other thyroid
vessels. It occasionally arises from the aorta, the right common carotid, the
subclavian or the internal mammary.
Point of Division. — The innominate artery sometimes divides above the level of the sterno-
clavicular joint, less frequently below it.
Position.— When the aortic arch is on the right side, the innominate is directed to the left side
of the neck.
Collateral Circulation. — Allan Burns demonstrated, on the dead subject, the possibility of the
establishment of the collateral circulation after Ugature of the innominate artery, by tying and
dividing that artery. He then found that "Even coarse injection, impelled into the aorta, passed
freely by the anastomosing branches into the arteries of the right arm, fiUing them and all the
vessels of the head completely. "' The branches by which this circulation would be carried on
are very numerous; thus, all the communications across the middle line between the branches
of the carotid arteries of opposite sides would be available for the supply of blood to the right
side of the head and neck; while the anastomosis between the costocervical of the subclavian and
the first aortic intercostal (see infra on the collateral circulation after obliteration of the thoracic
aorta) would bring the blood, by a fx'ee and direct course, into the right subclavian. The numerous
connections, also, between the intercostal arteries and the branches of the axillary and internal
mammary arteries would, doubtless, assist in the supply of blood to the right arm, while the
inferior epigastric from the external iliac would, by means of its anastomosis with the internal
mammary, compensate for any deficiency in the vascularity of the wall of the chest.
THE ARTERIES OF THE HEAD AND NECK.
The principal arteries of supply to the head and neck are the two common
carotids; they ascend in the neck and each divides into two branches, viz., (1) the
external carotid, supplying the exterior of the head, the face, and the greater part
of the neck; (2) the internal carotid, supplying to a great extent the parts within
the cranial and orbital cavities.
THE COMMON CAROTID ARTERY (A. CAROTIS COMMUNIS).
The common carotid arteries differ in length and in their mode of origin. The
right begins at the bifurcation of the innominate artery behind the sternoclavicular
joint and is confined to the neck. The left springs from the highest part of the
arch of the aorta to the left of, and on a plane posterior to tlie innominate artery,
and therefore consists of a thoracic and a cervical portion.
The thoracic portion of the left common carotid artery ascends from the arch of
the aorta through the superior mediastinum to the level of the left sternoclavicular
joint, where it is continuous with the cervical portion.
Relations. — In front, it is separated from the manubrium sterni by the Sternohyoideus and
Sternothyreoideus, the anterior portions of the left pleura and lung, the left innominate vein,
and the remains of the thymus; behind, it lies on the trachea, esophagus, left recurrent nerve,
and thoracic duct. To its right side below is the innominate artery, and above, the trachea, the
inferior thyroid veins, and the remains of the thymus; to its left side are the left vagus and phrenic
nerves, left pleura, and lung. The left subclavian artery is posterior and shghtly lateral to it.
' Surgical Anatomy of tie Head and Neck, p. 62.
550
ANGIOLOGY
The cervical portions of the common carotids resemble each other so closely
that one description will apply to both (Fig. 507). Each vessel passes obliquely
upward, from behind the sternoclavicular articulation, to the level of the upper
border of the thyroid cartilage, where it divides into the external and internal
carotid arteries.
Fig. 507. — Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.
At the lower part of the neck the two common carotid arteries are separated
from each other by a very narrow interval which contains the trachea; but at the
upper part, the thyroid gland, the larynx and pharj'nx project forward between
the two vessels. The common carotid artery is contained in a sheath, which is
derived from the deep cervical fascia and encloses also the internal jugular vein
and vagus nerve, the vein lying lateral to the artery, and the nerve between the
artery and vein, on a plane posterior to both. On opening the sheath, each of
these three structures is seen to have a separate fibrous investment.
THE EXTERNAL CAROTID ARTERY 551
Relations. — At the lower part of the neck the common carotid artery is very deeply seated,
being covered by the integument, superficial fascia, Platysma, and deep cervical fascia, the Sterno-
cleidomastoideus, Sternohyoideus, Sternothyreoideus, and Omohyoideus; in the upper part of
its coiurse it is more superficial, being covered merely by the integument, the superficial fascia,
Platysma, deep cervical fascia, and medial margin of the Sternocleidomastoideus. When the
latter muscle is drawTi backward, the artery is seen to be contained in a triangular space, the
carotid triangle, bounded behind by the Sternocleidomastoideus, above by the Stylohyoideus
anil posterior belly of the Digastricus, and below by the superior belly of the Omohyoideus.
This part of the artery is crossed obUquely, from its medial to its lateral side, by the sterno-
cleidomastoid branch of the superior thyroid artery; it is also crossed by the superior and middle
thyroid veins which end in the internal jugular; descending in front of its sheath is the descending
branch of the hypoglossal nerve, this filament being joined by one or two branches from the
cervical nerves, which cross the vessel obUquely. Sometimes the descending branch of the hypo-
glossal nerve is contained within the sheath. The superior thyroid vein crosses the artery near
its termination, and the middle thyroid vein a Uttle below the level of the cricoid cartilage; the
anterior jugular vein crosses the artery just above the clavicle, but is separated from it by the
Sternohyoideus and Sternoth>Teoideus. Behind, the artery is separated from the transverse
processes of the cervical vertebrae by the Longus colli and Longus capitis, the sympathetic trunk
being interposed between it and the muscles. The inferior thyroid artery crosses behind the
lower part of the vessel. Medially, it is in relation with the esophagus, trachea, and thyroid
gland (which overlaps it), the inferior thyroid artery and recurrent nerve being interposed; higher
up, with the larynx and pharynx. Lateral to the artery are the internal jugular vein and vagus
nerve.
At the lower part of the neck, the right recurrent nerve crosses obUquely behind the artery;
the right internal jugular vein diverges from the artery, but the left approaches and often over-
laps the lower part of the artery.
Behind the angle of bifurcation of the common carotid artery is a reddish-brown oval body,
known as the glomus caroticuin {carotid body). It is similar in structure to the glomus coccygeum
{coccygeal body) which is situated on the middle sacral artery.
Peculiarities as to Origin. — The right common carotid may arise above the level of the upper
border of the sternoclavicular articulation; this variation occurs in about 12 per cent, of cases.
In other cases the artery may arise as a separate branch from the arch of the aorta, or in con-
junction with the left carotid. The lejt common carotid varies in its origin more than the right.
In the majority of abnormal cases it arises with the innominate artery; if that artery is absent,
the two carotids arise usuaUy by a single trunk. It is rarely joined with the left subclavian^
except in cases of transposition of the aortic arch.
Peculiarities as to Point of Division. — In the majority of abnormal cases this occurs higher
than usual, the artery dividing opposite or even above the hyoid bone; more rarely, it occurs
below, opposite the middle of the larynx, or the lower border of the cricoid cartilage; one case
is related by Morgagni, where the artery was only 4 cm. in length and divided at the root of the
neck. Very rarely, the common carotid ascends in the neck without any subdivision, either the
external or the internal carotid bemg wanting; and in a few cases the common carotid has been
found to be absent, the external and internal carotids arising directly from the arch of the aorta.
This peculiarity existed on both sides in some instances, on one side in others.
Occasional Branches. — The common carotid usually gives off no branch previous to its bifurca-
tion, but it occasionaUy gives origin to the superior thyroid or its laryngeal branch, the ascend-
ing pharyngeal, the inlerior thyroid, or, more rareh', the vertebral artery.
Collateral Circulation. — After Ugatiu-e of the common carotid, the coUateral circulation can
be perfectly estabUshed, by the free communication which exists between the carotid arteries
of opposite sides, both without and within the cranium, and by enlargement of the branches of
the subclavian artery on the side corresponding to that on which the vessel has been tied. The
chief communications outside the skull take place between the superior and inferior thyroid
arteries, and the profunda cervicis and ramus descendens of the occipital; the vertebral takes
the place of the internal carotid within the cranium.
The External Carotid Artery (A. Carotis Externa) (Fig. 507).
The external carotid artery begins opposite the upper border of the thyroid
cartilage, and, taking a slightly curved course, passes upward and forward, and
then inclines backward to the space behind the neck of the mandible, where it
divides into the superficial temporal and internal maxillary arteries. It rapidly
diminishes in size in its course up the neck, owing to the number and large size
of the branches given off from it. In the child, it is somewhat smaller than the
internal carotid; but in the adult, the two vessels are of nearly equal size. At its
552 ANGIOLOGY
origin, this artery is more superficial, and placed nearer the middle line than the
internal carotid, and is contained within the carotid triangle.
Relations. — The external carotid artery is covered by the skin, superficial fascia, Platysma,
deep fascia, and anterior margin of the Sternocleidomastoideus; it is crossed by the hj'poglossal
nerve, bj' the Ungual, ranine, common facial, and superior thjToid veins; and bj- the Digastricus
and Stylohyoideus; higher up it passes deeply into the substance of the parotid gland, where
it lies deep to the facial nerve and the junction of the temporal and internal maxillary veins.
Medial to it are the hyoid bone, the wall of the pharynx, the superior larjTigeal nerve, and a
portion of the parotid gland. Lateral to it, in the lower part of its course, is the internal carotid
artery. Posterior to it, near its origin, is the superior laryngeal nerve; and higher up, it is sepa-
rated from the internal carotid by the Styloglossus and StylopharjTigeus, the glossopharj-ngeal
nerve, the pharjTigeal branch of the vagus, and part of the parotid gland.
Branches. — The branches of the external carotid artery may be divided into four
sets.
Anterior. Posterior. Ascending. Terminal.
Superior Thyroid. Occipital. Ascending Superficial Temporal.
Lingual. Posterior Auricular. Pharyngeal. Internal Maxillary.
External Maxillary.
1. The superior thyroid artery (o. thyreoidea superior) (Fig. 507) arises from
the external carotid artery just below the level of the greater cornu of the hyoid
bone and ends in the thyroid gland.
Relations. — From its origin under the anterior border of the Sternocleidomastoideus it runs
upward and forward for a short distance in the carotid triangle, where it is covered by the skin,
Platysma, and fascia; it then arches downward beneath the Omohyoideus, Sternohyoideus, and
SternothjTeoideus. To its medial side are the Constrictor pharjTigis inferior and the external
branch of the superior larjTigeal nerve.
Branches. — It distributes twigs to the adjacent muscles, and numerous branches
to the thyroid gland, anastomosing with its fellow of the opposite side, and with
the inferior thyroid arteries. The branches to the gland are generally two in
number; one, the larger, supplies principally the anterior surface; on the isthmus
of the gland it anastomoses with the corresponding artery of the opposite side:
a second branch descends on the posterior surface of the gland and anastomoses
with the inferior thyroid artery.
Besides the arteries distributed to the muscles and to the thyroid gland, the
branches of the superior thyroid are :
Hyoid. Superior Laryngeal.
Sternocleidomastoid. Cricothyroid.
The Hyoid Branch {ramus hyoideus; infrahyoid branch) is small and runs along
the lower border of the hvoid bone beneath the Thvreohvoideus and anastomoses
with the vessel of the opposite side.
The Sternocleidomastoid Branch {ramus sternocleidomastoideus; sternomastoid
branch) runs downward and lateralward across the sheath of the common carotid
artery, and supplies the Sternocleidomastoideus and neighboring muscles and
integument; it frequently arises as a separate branch from the external carotid.
The Superior Laryngeal Artery (a. laryngca superior), larger than either of the
preceding, accompanies the internal laryngeal branch of the superior laryngeal
nerve, beneath the Thyreohyoideus; it pierces the hyothyroid membrane, and
supplies the muscles, mucous membrane, and glands of the larynx, anastomosing
with the branch from the opposite side.
The Cricothyroid Branch {ramus cricothyreoideus) is small and runs transversely
across the cricothyroid laembrajie, communicating with the artery of the opposite
side.
THE EXTERNAL CAROTID ARTERY 553
2. The lingual artery (a. lingnalis) (Fig. 513) arises from the external carotid
between the superior thyroid and external maxillary; it first runs obliquely upward
and medialward to the greater cornu of the hyoid bone; it then curves downward
and forward, forming a loop which is crossed by the hypoglossal nerve, and passing
beneath the Digastricus and Stylohyoideus it runs horizontally forward, beneath
the Hyoglossus, and finally, ascending almost perpendicularly to the tongue, turns
forward on its lower surface as far as the tip, under the name of the profunda
linguae.
Relations. — Its first, or oblique, portion is superficial, and is contained within the carotid
triangle; it rests upon the Constrictor pharyngis medius, and is covered by the Platysma and
the fascia of the neck. Its second, or curved, portion also hcs upon the Constrictor pharyngis
medius, being covered at first by the tendon of the Digastricus and by the Stylohyoideus, and
afterward by the Hyoglossus. Its third, or horizontal, portion lies between the Hyoglossus and
Genioglossus. The fourth, or terminal part,, imder the name of the profunda linguae {ranine
artery) runs along the under surface of the tongue to its tip; here it is superficial, being covered
only by the mucous membrane; above it is the Longitudinalis inferior, and on the medial side
the Genioglossus. The hypoglossal nerve crosses the first part of the hngual artery, but is sepa-
rated from the second part by the Hyoglossus.
Branches. — The branches of the lingual artery are:
Hyoid. Sublingual.
Dorsales linguae. Profunda linguae.
The Hyoid Branch {ramus hyoideus; suprahyoid branch) runs along the upper
border of the hyoid bone, supplying the muscles attached to it and anastomosing
with its fellow of the opposite side.
The Arteriae Dorsales Linguae {rami dorsales linguoe) consist usually of two or
three small branches which arise beneath the Hyoglossus; they ascend to the back
part of the dorsum of the tongue, and supply the mucous membrane in this situa-
tion, the glossopalatine arch, the tonsil, soft palate, and epiglottis; anastomosing
with the vessels of the opposite side.
The Sublingual Artery (a. sublingualis) arises at the anterior margin of the Hyo-
glossus, and runs forward between the Genioglossus and jNIylohyoideus to the sub-
lingual gland. It supplies the gland and gives branches to the Mylohyoideus and
neighboring muscles, and to the mucous membrane of the mouth and gums. One
branch runs behind the alveolar process of the mandible in the substance of the
gum to anastomose with a similar artery from the other side; another pierces
the ]\Iylohyoideus and anastomoses with the submental branch of the external
maxillary artery.
The Arteria Profunda Linguae {ranine artery; deep lingual artery) is the terminal
portion of the lingual artery; it pursues a tortuous course and runs along the under
surface of the tongue, below the Longitudinalis inferior, and above the mucous
membrane; it lies on the lateral side of the Genioglossus, accompanied by the
lingual nerve. At the tip of the tongue, it is said to anastomose with the artery
of the opposite side, but this is denied by Hyrtl. In the mouth, these vessels are
placed one on either side of the frenulum linguae.
3. The external maxillary artery (a. maxillaris externa; facial artery) (Tig. 508),
arises in the carotid triangle a little above the lingual artery and, sheltered by the
ramus of the mandible, passes obliquely up beneath the Digastricus and Stylo-
hyoideus, over which it arches to enter a groove on the posterior surface of the
submaxillary gland. It then curves upward over the body of the mandible at the
antero-inferior angle of the ]\Iasseter; passes forward and upward across the cheek
to the angle of the mouth, then ascends along the side of the nose, and ends at
the medial commissure of the eye, under the name of the angular artery. This
vessel, both in the neck and on the face, is remarkably tortuous: in the former
554
ANGIOLOGY
situation, to accommodate itself to the movements of the pharynx in deglutition;
and in the latter, to the movements of the mandible, lips, and cheeks.
Relations. — In the neck, its origin is superficial, being covered by the integument, Platj'sma,
and fascia; it then passes beneath the Digastricus and Stjdohyoideus muscles and part of the
submaxillary gland, and frequently beneath the hypoglossal nerve. It lies upon the Constrictorea
pharyngis medius and superior, the latter of which separates it, at the summit of its arch, from
the lower and back part of the tonsil. On the face, where it passes over the body of the mandible,
it is comparatively superficial, lying immediately beneath the Platysma. In its course over the
face, it is covered by the integument, the fat of the cheek, and, near the angle of the mouth,
by the Platysma, Risorius, and Zygomaticus. It rests on the Buccinator and Caninus, and
passes either over or under the infraorbital head of the Quadratus labii superioris. The anterior
facial vein hes lateral to the artery, and takes a more du-ect course across the face, where it is
separated from the artery by a considerable interval. In the neck it lies superficial to the artery.
The branches of the facial nerve cross the artery from behind forward.
Angular
Lateral
nasal
Septal
Superior labial
Inferior labial
Fig. 508. — The arteries of the face and scalp.*
Branches. — The branches of the artery may be divided into two sets: those
given off in the neck (cervical), and those on the face (facial).
Cervical Branches. Facial Branches.
Ascending Palatine. Inferior Labial.
Tonsillar. Superior Labial.
Glandular. Lateral Nasal.
Submental. Angular.
Muscular. Muscular.
1 The muscular tissue of the hpa must be supposed to have been cut away, in order to show the course of the labial
arteries.
THE EXTERNAL CAROTID ARTERY
555
The Ascending Palatine Artery (a. palatina ascendens) (Fig. 513) arises close to
the origin of the external maxillary artery and passes up between the Styloglossus
and Stylopharyngeus to the side of the pharynx, along which it is continued between
the Constrictor pharyngis superior and the Pterygoideus internus to near the base
of the skull. It divides near the Levator veli palatini into two branches: one fol-
lows the course of this muscle, and, winding over the upper border of the Constrictor
pharyngis superior, supplies the soft palate and the palatine glande, anastomosing
with its fellow of the opposite side and with the descending palatine branch of the
internal maxillary artery; the other pierces the Constrictor pharyngis superior
and supplies the palatine tonsil and auditory tube, anastomosing with the tonsillar
and ascending pharyngeal arteries.
The Tonsillar Branch {ramus tonsillaris) (Fig. 513) ascends between the Ptery-
goideus internus and Styloglossus, and then along the side of the pharynx,
perforating the Constrictor pharyngis superior, to ramify in the substance of the
palatine tonsil and root of the tongue.
The Glandular Branches {rami glandulares; submaxillary branches) consist of three
or four large vessels, which supply the submaxillary gland, some being prolonged
to the neighboring muscles, lymph glands, and integument.
The Submental Artery (a. submentalis) the largest of the cervical branches, is
given off from the facial artery just as that vessel quits the submaxillary gland:
it runs forward upon the Mylohyoideus, just below the body of the mandible,
and beneath the Digastricus. It supplies the surrounding muscles, and anastomoses
with the sublingual artery and with the mylohyoid branch of the inferior alveolar;
at the symphysis menti it turns upward over the border of the mandible and
divides into a superficial and a deep branch. The superficial branch passes between
the integument and Quadratus labii inferioris, and anastomoses with the inferior
labial artery; the deep branch runs between the muscle and the bone, supplies
the lip, and anastomoses with the inferior labial and mental arteries.
Fig. 509 — The labial coronary arteries, the glands of the lips, and the nerves of the right side seen from the
posterior surface after removal of the mucous membrane. (Poirier and Charpy.)
The Inferior Labial Artery (a. labialis inferior; inferior coronary artery) arises near
the angle of the mouth; it passes upward and forward beneath the Triangularis
and, penetrating the Orbicularis oris, runs in a tortuous course along the edge of
the lower lip between this muscle and the mucous membrane. It supplies the
labial glands, the mucous membrane, and the muscles of the lower lip; and anas-
tomoses with the artery of the opposite side, and with the mental branch of the
inferior alveolar artery.
The Superior Labial Artery (a. labialis superior; superior coronary artery) is larger
and more tortuous than the inferior. It follows a similar course along the edge
of the upper lip, lying between the mucous membrane and the Orbicularis oris,
and anastomoses with the artery of the opposite side. It supplies the upper lip,
556 ANGIOLOGY
and gives off in its course two or three vessels which ascend to the nose; a septal
branch ramifies on the nasal septum as far as the point of the nose, and an alar
branch supplies the ala of the nose.
The Lateral Nasal branch is derived from the external maxillary as that" vessel
ascends along the side of the nose. It supplies the ala and dorsum of the nose, anas-
tomosing with its fellow, with the septal and alar branches, with the dorsal nasal
branch of the ophthalmic, and with the infraorbital branch of the internal maxillary.
The Angular Artery (a. angularis) is the terminal part of the external maxillary;
it ascends to the medial angle of the orbit, imbedded in the fibers of the angular
head of the Quadratus labii superioris, and accompanied by the angular vein.
On the cheek it distributes branches which anastomose with the infraorbital;
after supplying the lacrimal sac and Orbicularis oculi, it ends by anastomosing
with the dorsal nasal branch of the ophthalmic artery.
The Muscular Branches in the neck are distributed to the Pterygoideus internus and
Stylohyoideus, and on the face to the Masseter and Buccinator. The anastomoses
of the external maxillary artery are very numerous, not only with the vessel of
the opposite side, but, in the neck, with the sublingual branch of the lingual, with
the ascending pharyngeal, and by its ascending palatine and tonsillar branches
with the palatine branch of the internal maxillary; on the face, with the mental
branch of the inferior alveolar as it emerges from the mental foramen, with the
transverse facial branch of the superficial temporal, with the infraorbital branch
of the internal maxillary, and with the dorsal nasal branch of the ophthalmic.
Peculiarities. — The external maxillary artery not infrequently arises in common with the
lingual. It varies in its size and in the extent to which it supplies the face" it occasionally ends
as the submental, and not infrequently extends only as high as the angle of the mouth or nose.
The deficiency is then compensated for by enlargement of one of the neighboring arteries.
4. The occipital artery (a. occipitalis) (Fig. 508) arises from the posterior part
of the external carotid, opposite the external maxillary, near the lower margin
of the posterior belly of the Digastricus, and ends in the posterior part of the scalp.
Course and Relations. — At its origin, it is covered by the posterior belly of the Digastricus
and the Stylohyoideus, and the hypoglossal nerve winds around it from behind forward; higher
up, it crosses the internal carotid artery, the internal jugular vein, and the vagus and accessory
nerves. It next ascends to the interval between the transverse process of the atlas and the mastoid
process of the temporal bone, and passes horizontally backward, grooving the surface of the
latter bone, being covered by the Sternocleidomastoideus, Splenius capitis, Longissimus capitis,
and Digastricus, and resting upon the Rectus capitis lateralis, the Obliquus superior, and Semi-
spinalis capitis. It then changes its course and runs vertically upward, pierces the fascia con-
necting the cranial attachment of the Trapezius with the Sternocleidomastoideus, and ascends
in a tortuous course in the superficial fascia of the scalp, where it divides into numerous branches,
which reach as high as the vertex of the skull and anastomose with the posterior auricular and
superficial temporal arteries. Its terrninal portion is accompanied by the greater occipital nerve.
Branches. — The branches of the occipital artery are:
Muscular. Sternocleidomastoid. Auricular.
^Meningeal. Descending.
The Muscular Branches {rami musculares) supply the Digastricus, Stylohyoideus,
Splenius, and Longissimus capitis.
The Sternocleidomastoid Artery (a. sternocleidomastoidea; sternomastoid artery)
generally arises from the occipital close to its commencement, but sometimes
springs directly from the external carotid. It passes downward and backward
over the hypoglossal nerve, and enters the substance of the muscle, in company
with the accessory nerve.
The Auricular Branch (ramus auricularis) supplies the back of the concha and
frequently gives off a branch, which enters the skull through the mastoid foramen
I
THE EXTERNAL CAROTID ARTERY 557
and supplies the diim mater, the diploe, and the mastoid cells; this latter branch
sometimes arises from the occipital artery, and is then known as the mastoid branch.
The Meningeal Branch (ramus meningevs; dvral branch) ascends with the internal
jugular vein, and enters the skull through the jugular foramen and condyloid
canal, to supply the dura mater in the posterior fossa.
The Descending Branch {ramvs descendens; arieria princeps cerricis) (Fig. 513),
the largest branch of the occipital, descends on the back of the neck, and divides
into a superficial and deep portion. The superficial portion runs beneath the
Splenius, giving off branches which pierce that muscle to supply the Trapezius and
anastomose with the ascending branch of the transverse cervical: the deep portion
runs down between the Semispinals capitis and colli, and anastomoses with the
vertebral and with the a. profunda cervicalis, a branch of the costocervical trunk.
The anastomosis between these vessels assists in establishing the collateral circu-
lation after ligature of the common carotid or subclavian artery.
The terminal branches of the occipital artery are distributed to the back of the
head: they are very tortuous, and lie between the integument and Occipitalis,
anastomosing with the artery of the opposite side and with the posterior auricular
and temporal arteries, and supplying the Occipitalis, the integument, and peri-
cranium. One of the terminal branches may give off a meningeal twig which passes
through the parietal foramen.
5. The posterior auricular artery (a. auricularis posterior) (Fig. 508) is small
and arises from the external carotid, above the Digastricus and Stylohyoideus,
opposite the apex of the styloid process. It ascends, under cover of the parotid
gland, on the styloid process of the temporal bone, to the groove between the
cartilage of the ear and the mastoid process, immediately above which it divides
into its auricular and occipital branches.
Branches. — Besides several small branches to the Digastricus, Stylohyoideus,
and Sternocleidomastoideus, and to the parotid gland, this vessel gives off three
branches:
Stylomastoid. . Auricular. Occipital.
The Stylomastoid Artery (a. styloviastoidea) enters the stylomastoid foramen and
supplies the tympanic cavity, the tympanic antrum and mastoid cells, and the
semicircular canals. In the young subject a branch from this vessel forms, with
the anterior tympanic artery from the internal maxillary, a vascular circle, which
I' surrounds the tympanic membrane, and from which delicate vessels ramify on that
membrane. It anastomoses with the superficial petrosal branch of the middle
meningeal artery by a twig which enters the hiatus canalis facialis.
The Auricular Branch (ramus auricularis) ascends behind the ear, beneath the
Auricularis posterior, and is distributed to the back of the auricula, upon which
it ramifies minutely, some branches curving around the margin of the cartilage,
others perforating it, to supply the anterior surface. It anastomoses with the
parietal and anterior auricular branches of the superficial temporal.
The Occipital Branch (ramus occipitalis) passes backward, over the Sternocleido-
mastoideus, to the scalp above and behind the ear. It supplies the Occipitalis
and the scalp in this situation and anastomoses with the occipital artery.
6. The ascending pharyngeal artery (a. pharyngea ascendens) (Fig. 513), the
smallest branch of the external carotid, is a long, slender vessel, deeply seated in
the neck, beneath the other branches of the external carotid and under the Stylo-
pharyngeus. It arises from the back part of the external carotid, near the com-
mencement of that vessel, and ascends vertically between the internal carotid
and the side of the pharynx, to the under surface of the base of the skull, lying
on the Longus capitis.
558 ANGIOLOGY
Branches. — Its branches are:
Pharyngeal. Prevertebral.
Palatine. Inferior Tympanic.
Posterior Meningeal.
The Pharyngeal Branches (rami pharyngei) are three or four in number. Two
of these descend to supply the Constrictores pharyngis medius and inferior and
the Stylopharyngeus, ramifying in their substance and in the mucous membrane
lining them.
The Palatine Branch varies in size, and may take the place of the ascending
palatine branch of the facial artery, when that vessel is small. It passes inward
upon the Constrictor pharyngis superior, sends ramifications to the soft palate
and tonsil, and supplies a branch to the auditory tube.
The Prevertebral Branches are numerous small vessels, which supply the Longi
capitis and colli, the sympathetic trunk, the h^-poglossal and vagus nerves, and the
lymph glands; they anastomose with the ascending cervical artery.
The Inferior Tympanic Artery (a. tympanica inferior) is a small branch which
passes through a minute foramen in the petrous portion of the temporal bone, in
company with the tympanic branch of the glossopharyngeal nerve, to supply the
medial wall of the tympanic cavity and anastomose with the other tympanic arteries.
The Meningeal Branches are several small vessels, which supply the dura mater.
One, the posterior meningeal, enters the cranium through the jugular foramen;
a second passes through the foramen lacerum; and occasionally a third through
the canal for the hypoglossal nerve.
7. The superficial temporal artery (a. temporalis snperficialis) (Fig. 508), the
smaller of the two terminal branches of the external carotid, appears, from its
direction, to be the continuation of that vessel. It begins in the substance of the
parotid gland, behind the neck of the mandible, and crosses over the posterior root
of the zygomatic process of the temporal bone; about 5 cm. above this process
it divides into two branches, a frontal and a parietal.
Relations. — -As it crosses ihe zygomatic process, it is covered by the Auricularis anterior muscle,
and by a dense fascia; it is crossed by the temporal and zygomatic branches of the facial nerve
and one or two veins, and is accompanied by the auriculotemporal nerve, which Ues immediately
behind it.
Branches. — Besides some twigs to the parotid gland, to the temporomandibular
joint, and to the Masseter muscle, its branches are:
Transverse Facial. Anterior Auricular.
Middle Temporal. Frontal.
Parietal.
The Transverse Facial Artery (a. transversa faciei) is given off from the superficial
temporal before that vessel quits the parotid gland; running forward through the
substance of the gland, it passes transversely across the side of the face, between
the parotid duct and the lower border of the zygomatic arch, and divides into numer-
ous branches, which supply the parotid gland and duct, the Masseter, and the
integument, and anastomose with the external maxillary, masseteric, buccinator,
and infraorbital arteries. This vessel rests on the Masseter, and is accompanied
by one or two branches of the facial nerve.
The Middle Temporal Artery (a. temporalis media) arises immediately above the
zj^gomatic arch, and, perforating the temporal fascia, gives branches to the Tem-
poralis, anastomosing with the deep temporal branches of the internal maxillary.
It occasionally gives off a zygomaticoorbital branch, which runs along the upper
border of the zygomatic arch, between the two layers of the temporal fascia, to
the lateral angle of the orbit. This branch, which may arise directly from the
THE EXTERNAL C.UiOTID ARTERY
559
superficial temporal artery, supplies the Orbicularis oculi, and anastomoses with
the lacrimal and palpebral branches of the ophthalmic artery.
The Anterior Auricular Branches {ranii auriculares anteriores) are distributed to
the anterior portion of the auricula, the lobule, and part of the external meatus,
anastomosing with the posterior auricular.
The Frontal Branch {ramus frontalis; anterior temporal) runs tortuously upward
and forward to the forehead, supplying the muscles, integument, and pericranium
in this region, and anastomosing with the'supraorbital and frontal arteries.
The Parietal Branch (ramus parietalis; posterior temporal) larger than the frontal,
curves upward and backward on the side of the head, lying superficial to the tem-
poral fascia, and anastomosing with its fellow of the opposite side, and with the
posterior auricular and occipital arteries.
Incisor branch
Fig. 510. — Plan of branches of internal maxillary arter>'.
8. The internal maxillary artery (a. maxillaris interna) (Fig. 510), the larger
of the two terminal branches of the external carotid, arises behind the neck of the
mandible, and is at first imbedded in the substance of the parotid gland; it passes
forward between the ramus of the mandible and the sphenomandibular ligament,
and then runs, either superficial or deep to the Pterygoideus externus, to the
pterygopalatine fossa. It supplies the deep structures of the face, and may be
divided into mandibular, pterygoid, and pterygopalatine portions.
The first or mandibular portion passes horizontally forward, between the ramus
of the mandible and the sphenomandibular ligament, where it lies parallel to and
a little below the auriculotemporal nerve; it crosses the inferior alveolar nerve,
and runs along the lower border of the Pterygoideus externus.
The second or pterygoid portion runs obliquely forward and upward under cover
of the ramus of the mandible and insertion of the Temporalis, on the superficial
(very frequently on the deep) surface of the Pterygoideus externus; it then passes
between the two heads of origin of this muscle and enters the fossa.
The third or pterygopalatine portion lies in the pterygopalatine fossa in relation
with the sphenopalatine ganglion.
560
ANGIOLOGY
The branches of this vessel may be divided into three groups (Fig. 511), corre-
sponding with its three divisions.
Branches of the First or Mandibular Portions. —
Anterior Tympanic.
Deep Auricular.
Inferior Alveolar.
Middle Meningeal.
Accessory INIeningeal
, The Anterior Tympanic Artery (a. tympanica anterior; tympanic artery) passes
upward behind the temporomandibular articulation, enters the tympanic cavity
through the petrotympanic fissure, and ramifies upon the tympanic membrane,
forming a vascular circle around the membrane with the stylomastoid branch of
the posterior auricular, and anastomosing with the artery of the pterygoid canal
and with the caroticotj'mpanic branch from the internal carotid.
j.rt. of Pferpffoia
Sphenopalatine
Infraorbital
Post. sup. alveolar
[Mylohyoid
Fig. 511. — Plan of branches of internal maxiUary artery.
The Deep Auricular Artery (a. auricularis profunda) often arises in common with
the preceding. It ascends in the substance of the parotid gland, behind the tem-
poromandibular articulation, pierces the cartilaginous or bony wall of the external
acoustic meatus, and supplies its cuticular lining and the outer surface of the
tympanic membrane. It gives a branch to the temporomandibular joint.
The Middle Meningeal Artery (a. meningea media; medidural artery) is the largest
of the arteries which supply the dura mater. It ascends between the spheno-
mandibular ligament and the Pterygoideus externus, and between the two roots
of the auriculotemporal nerve to the foramen spinosum of the sphenoid bone,
through which it enters the cranium ; it then runs forward in a groove on the great
wing of the sphenoid bone, and divides into two branches, anterior and posterior.
The anterior branch, the larger, crosses the great wing of the sphenoid, reaches the
groove, or canal, in the sphenoidal angle of the parietal bone, and then divides
into branches which spread out between the dura mater and internal surface of
the cranium, some passing upward as far as the vertex, and others backward to
the occipital region. The posterior branch curves backward on the squama of the
temporal bone, and, reaching the parietal some distance in front of its mastoid
angle, divides into branches which supply the posterior part of the dura mater and
I
THE EXTERNAL CAROTID ARTERY 561
cranium. The branches of the middle meningeal artery are distributed partly
to the dura mater, but chiefly to the bones; they anastomose with the arteries of
the opposite side, and with the anterior and posterior meningeal.
The middle meningeal on entering the cranium gives off the following branches: (1) Numerous
small vessels supply the semilunar ganglion and the dura mater in this situation. (2) A superficial
petrosal branch enters the hiatus of the facial canal, supplies the facial nerve, and anastomoses
with the stylomastoid branch of the posterior auricular artery. (3) A superior tympanic artery
runs in the canal for the Tensor tympani, and supphes this muscle and the lining membrane of
the canal. (4) Orbital branches pass through the superior orbital fissure or through separate
canals in the great wing of the sphenoid, to anastomose with the lacrimal or other branches of
the ophthalmic artery. (5) Temporal branches pa-ss through foramina in the great wing of the
sphenoid, and anastomose in the temporal fossa with the deep temporal arteries.
The Accessory Meningeal Branch {ramais meningeus accessorius; small meningeal
or parvidural branch) is sometimes derived from the preceding. It enters the
skull through the foramen ovale, and supplies the semilunar ganglion and dura
mater.
The Inferior Alveolar Artery (a. alveolaris inferior; inferior dental artery) descends
with the inferior alveolar nerve to the mandibular foramen on the medial surface
of the ramus of the mandible. It runs along the mandibular canal in the substance
of the bone, accompanied by the nerve, and opposite the first premolar tooth divides
into two branches, incisor and mental. The incisor branch is continued forward
beneath the incisor teeth as far as the middle line, where it anastomoses with the
artery of the opposite side; the mental branch escapes with the nerve at the mental
foramen, supplies the chin, and anastomoses with the submental and inferica-
labial arteries. Near its origin the inferior alveolar artery gives off a lingual branch
which descends with the lingual nerve and supplies the mucous membrane of the
mouth. As the inferior alveolar artery enters the foramen, it gives off a mylohyoid
branch which runs in the mylohyoid groove, and ramifies on the under surface of
the Mylohyoideus. The inferior alveolar artery and its incisor branch during
their course through the substance of the bone give off a few twigs which are lost
in the cancellous tissue, and a series of branches which correspond in number to
the roots of the teeth : these enter the minute apertures at the extremities of the
roots, and supply the pulp of the teeth.
Branches of the Second or Pterygoid Portion. —
Deep Temporal. Masseteric.
Pterygoid. Buccinator.
The Deep Temporal Branches, two in number, anterior and posterior, ascend
between the Temporalis and the pericranium; they supply the muscle, and anasto-
mose with the middle temporal artery ; the anterior communicates with the lacrimal
artery by means of small branches which perforate the zygomatic bone and great
wing of the sphenoid.
The Pterygoid Branches {rami pterygoidei) , irregular in their number and origin,
supply the Pterygoidei.
The Masseteric Artery (a. masseterica) is small and passes lateralward through
the mandibular notch to the deep surface of the Masseter. It supplies the muscle,
and anastomoses with the masseteric branches of the external maxillary and with
the transverse facial artery.
The Buccinator Artery (a. buccinator ia; buccal artery) is small and runs obliquely
forward, between the Pterygoideus internus and the insertion of the Temporalis,
to the outer surface of the Buccinator, to which it is distributed, anastomosing
with branches of the external maxillary and with the infraorbital.
Branches of the Third or Pterygopalatine Portion. —
Posterior Superior Alveolar. Artery of the Pterygoid Canal.
Infraorbital. Pharyngeal.
Des.cending Palatine. Sphenopalatine.
36
562 ANGIOLOGY
The Posterior Superior Alveolar Artery (a. aheolaris superior posterior; alveolar or
posterior dental artery) is given oft' from the internal maxillary, frequently in con-
junction with the infraorbital just as the trunk of the vessel is passing into the
pterygopalatine fossa. Descending upon the tuberosity of the maxilla, it divides
into numerous branches, some of which enter the alveolar canals, to supply the
molar and premolar teeth and the lining of the maxillary sinus, while others are
continued forward on the alveolar process to supply the gums.
The Infraorbital Artery (a. infraorbitalis) appears, from its direction, to be the
continuation of the trunk of the internal maxillary, but often arises in conjunction
with the posterior superior alveolar. It runs along the infraorbital groove and
canal with the infraorbital nerve, and emerges on the face through the infraorbital
foramen, beneath the infraorbital head of the Quadratus labii superioris. While
in the canal, it gives off (a) orbital branches which assist in supplying the Rectus
inferior and Obliquus inferior and the lacrimal sac, and (6) anterior superior alveolar
branches which descend through the anterior alveolar canals to supph' the upper
incisor and canine teeth and the mucous membrane of the maxillary sinus. On
the face, some branches pass upward to the medial angle of the orbit and the
lacrimal sac, anastomosing with the angular branch of the external maxillary
artery ; others run toward the nose, anastomosing with the dorsal nasal branch of
the ophthalmic; and others descend between the Quadratus labii superioris and
the Caninus, and anastomose with the external maxillary, transverse facial, and
buccinator arteries. The four remaining branches arise from that portion of the
internal maxillary which is contained in the pterygopalatine fossa.
The Descending Palatine Artery (a. palatina descendens) descends through the
pterygopalatine canal with the anterior palatine branch of the sphenopalatine
ganglion, and, emerging from the greater palatine foramen, runs forward in a groove
on the medial side of the alveolar border of the hard palate to the incisive canal;
the terminal branch of the artery passes upward through this canal to anastomose
with the sphenopalatine artery. Branches are distributed to the gums, the palatine
glands, and the mucous membrane of the roof of the mouth ; while in the pterygo-
palatine canal it gives off twigs which descend in the lesser palatine canals to supply
the soft palate and palatine tonsil, anastomosing with the ascending palatine artery.
The Artery of the Pterygoid Canal (a. canalis pterygoidei; Vidian artery) passes
backward along the pterygoid canal with the corresponding nerve. It is distributed
to the upper part of the pharynx and to the auditory tube, sending into the tympanic
cavity a small branch which anastomoses with the other tympanic arteries.
The Pharyngeal Branch is very small; it runs backward through the pharyngeal
canal with the pharyngeal nerve, and is distributed to the upper part of the pharynx
and to the auditory tube.
The Sphenopalatine Artery (a. sphenopalatina ; nasopalatine artery) passes through
the sphenopalatine foramen into the cavity of the nose, at the back part of the
superior meatus. Here it gives oft' its posterior lateral nasal branches which spread
forward over the conchse and meatuses, anastomose with the ethmoidal arteries
and the nasal branches of the descending palatine, and assist in supplying the
frontal, maxillary, ethmoidal, and sphenoidal sinuses. Crossing the under surface of
the sphenoid the sphenopalatine artery ends on the nasar septum as the posterior
septal branches; these anastomose with the ethmoidal arteries and the septal
branch of the superior labial; one branch descends in a groove on the vomer to
the incisive canal and anastomoses with the descending palatine artery.
THE TRIANGLES OF THE NECK (Fig. 512).
The side of the neck presents a somewhat quadrilateral outline, limited, above,
by the lower border of the body of the mandible, and an imaginary line extending
THE TRIANGLES OF THE NECK
563
from the angle of the mandible to the mastoid process; below, by the upper border
of the clavicle; in front, by the middle line of the neck; behind, by the anterior
margin of the Trapezius. This space is subdivided into two large triangles by the
Sternocleidomastoideus, which passes obliquely across the neck, from the sternum
and clavicle below, to the mastoid process and occipital bone above. The triangular
space in front of this muscle is called the anterior triangle; and that behind it, the
posterior triangle.
Anterior Triangle. — The anterior triangle is bounded, hi front, by the middle line
of the neck; behind, by the anterior margin of the Sternocleidomastoideus; its
base, directed upward, is formed by the lower border of the body of the mandible,
and a line extending from the angle of the mandible to the mastoid process; its
apex is below, at the sternum. This space is subdivided into four smaller triangles
by the Digastricus above, and the superior belly of the Omohyoideus below.
These smaller triangles are named the inferior carotid, the superior carotid, the
submaxillary, and the suprahyoid.
Suprahyoid triangle
Submaxillary triangle
Superior carotid triangle
Inferior carotid triangle
Occipital triangle
Subclavian triangle
Fig. 512. — The triangles of the neck.
The Inferior Carotid, or Muscular Triangle, is bounded, in front, by the median
line of the neck from the hyoid bone to the sternum ; behind, by the anterior margin
of the Sternocleidomastoideus; above, by the superior belly of the Omohyoideus.
It is covered by the integument, superficial fascia, Platysma, and deep fascia,
ramifying in which are some of the branches of the supraclavicular nerves. Be-
neath these superficial structures are the Sternohyoideus and Sternothyreoideus,
which, together with the anterior margin of the Sternocleidomastoideus, conceal
the lower part of the common carotid artery.^ This vessel is enclosed within its
sheath, together with the internal jugular vein and vagus nerve; the vein lies
lateral to the artery on the right side of the neck, but overlaps it below on the left
side; the nerve lies between the artery and vein, on a plane posterior to both.
' Therefore the common carotid artery and internal jugular vein are not, strictly speaking, contained in this tri-
angle, since they are covered by the Sternocleidomastoideus: that is to say, they lie under that muscle, which forms
the posterior border of the triangle. But as they lie very close to the structures which are really contained in the
triangle, and whose position it is essential to remember in operating on this part of the artery, it is e.xpedient to study
the relations of all these parts together.
564 ANGIOLOGY
In front of the sheath are a few descending filaments from the ansa hypoglossi;
behind the sheath are the inferior thyroid artery, the recurrent nerve, and the sym-
pathetic trmik; and on its medial side, the esophagus, the trachea, the thyroid
gland, and the lower part of the larynx. By cutting into the upper part of this
space, and slightly displacing the Sternocleidomastoideus, the common carotid
artery may be tied below the Omohyoideus.
The Superior Carotid, or Carotid Triangle, is bounded, behind by the Sternocleido-
mastoideus; beloiv, by the superior belly of the Omohyoideus; and above, by the
Stylohyoideus and the posterior belly of the Digastricus. It is covered by the integu-
ment, superficial fascia, Platysma and deep fascia; ramifying in which are branches
of the facial and cutaneous cervical nerves. Its floor is formed by parts of the Thyro-
hyoideus, Hyoglossus, and the Constrictores pharyngis medius and inferior. This
space when dissected is seen to contain the upper part of the common carotid
artery, which bifurcates opposite the upper border of the thyroid cartilage into the
external and internal carotid. These vessels are somewhat concealed from view
by the anterior margin of the Sternocleidomastoideus, which overlaps them.
The external and internal carotids lie side by side, the external being the more
anterior of the two. The following branches of the external carotid are also met
with in this space: the superior thyroid, running forward and downward; the
lingual, directly forward; the external maxillary, forward and upward; the occipital,
backward; and the ascending pharyngeal, directly upward on the medial side of the
internal carotid. The veins met with are: the internal jugular, which lies on the
lateral side of the common and internal carotid arteries; and veins corresponding
to the above-mentioned branches of the external carotid — viz., the superior thyroid,
the lingual, common facial, ascending pharyngeal, and sometimes the occipital —
all of which end in the internal jugular. The nerves in this space are the following.
In front of the sheath of the common carotid is the ramus descendens hypoglossi.
The hypoglossal nerve crosses both the internal and external carotids above,
curving around the origin of the occipital artery. Within the sheath, between the
artery and vein, and behind both, is the vagus nerve; behind the sheath, the sym-
pathetic trunk. On the lateral side of the vessels, the accessory nerve runs for a
short distance before it pierces the Sternocleidomastoideus; and on the medial
side of the external carotid, just below the hyoid bone, may be seen the internal
branch of the superior laryngeal nerve; and, still more inferiorly, the external
branch of the same nerve. The upper portion of the larynx and lower portion of
the pharynx are also found in the front part of this space.
The Submaxillary or Digastric Triangle corresponds to the region of the neck
immediatelv beneath the bodv of the mandible. It is bounded, above, bv the lower
border of the body of the mandible, and a line drawn from its angle to the mastoid
process; beloiv, by the posterior belly of the Digastricus and the Stylohyoideus;
in front, by the anterior belly of the Digastricus. It is covered by the integument,
superficial fascia, Platysma, and deep fascia, ramifying in which are branches
of the facial nerve and ascending filaments of the cutaneous cervical nerve. Its
floor is formed by the Mylohyoideus, Hyoglossus, and Constrictor pharyngis
superior. It is divided into an anterior and a posterior part by the stylomandibular
ligament. The anterior part contains the submaxillary gland, superficial to which
is the anterior facial vein, while imbedded in the gland is the external maxillary
artery and its glandular branches; beneath the gland, on the surface of the Mylo-
hyoideus, are the submental artery and the mylohyoid artery and nerve. The
posterior part of this triangle contains the external carotid artery, ascending deeply
in the substance of the parotid gland; this vessel lies here in front of, and super-
ficial to, the internal carotid, being crossed by the facial nerve, and gives off in
its course the posterior auricular, superficial temporal, and internal maxillary
branches: more deeply are the internal carotid, the internal jugular vein, and the
I
THE TRIANGLES OF THE NECK 565
vagus nerve, separated from the external carotid by the Styloglossus and Stylo-
pharyngeus, and the glossopharyngeal nerve.'
The Suprahyoid Triangle is limited behind by the anterior belly of the Digastricus,
in front by the middle line of the neck between the mandible and the hyoid bone;
below, by the body of the hyoid bone; its floor is formed by the Mylohyoideus.
It contains one or two lymph glands and some small veins; the latter unite to form
the anterior jugular vein.
Posterior Triangle.— The posterior triangle is bounded, in front, by the Sterno-
cleidomastoideus; behind, by the anterior margin of the Trapezius; its base is formed
by the middle third of the clavicle; its apex, by the occipital bone. The space
is crossed, about 2.5 cm. above the clavicle, by the inferior belly of the Omo-
hyoideus, which divides it into two triangles, an upper or occipital, and a lower or
subclavian.
The Occipital Triangle, the larger division of the posterior triangle, is bounded,
in front, by the Sternocleidomastoideus; behind, by the Trapezius; below, by the
Omohyoideus. Its floor is formed from above downward by the Splenius capitis.
Levator scapuLT, and the Scaleni medius and posterior. It is covered by the skin,
the superficial and deep fascia^, and by the Platysma below. The accessory nerve
is directed obliquely across the space from the Sternocleidomastoideus, which it
pierces, to the under surface of the Trapezius; below, the supraclavicular nerves
and the transverse cervical vessels and the upper part of the brachial plexus cross
the space. A chain of lymph glands is also found running along the posterior border
of the Sternocleidomastoideus, from the mastoid process to the root of the neck.
The Subclavian Triangle, the smaller division of the posterior triangle, is bounded,
above, by the inferior belly of the Omohyoideus; beloiv, by the clavicle; its base is
formed by the posterior border of the Sternocleidomastoideus. Its floor is formed
by the first rib with the first digitation of the Serratus anterior. The size of the
subclavian triangle varies with the extent of attachment of the clavicular portions
of the Sternocleidomastoideus and Trapezius, and also with the height at which
the Omohyoideus crosses the neck. Its height also varies according to the position
of the arm, being diminished by -raising the limb, on account of the ascent of the
clavicle, and increased by drawing the arm downward, when that bone is depressed.
This space is covered by the integument, the superficial and deep fasciie and the
Platysma, and crossed by the supraclavicular nerves. Just above the level of the
clavicle, the third portion of the subclavian artery curves lateralward and downward
from the lateral margin of the Scalenus anterior, across the first rib, to the axilla,
and this is the situation most commonly chosen for ligaturing the vessel. Some-
times this vessel rises as high as 4 cm. above the clavicle; occasionallj', it passes
in front of the Scalenus anterior, or pierces the fibers of that muscle. The sub-
clavian vein lies behind the clavicle, and is not usually seen in this space; but in
some cases it rises as high as the artery, and has even been seen to pass with that
vessel behind the Scalenus anterior. The brachial plexus of nerves lies above
the artery, and in close contact with it. Passing transversely behind the clavicle
are the transverse scapular vessels; and traversing its upper angle in the same
direction, the transverse cervical artery and vein. The external jugular vein runs
vertically downward behind the posterior border of the Sternocleidomastoideus,
to terminate in the subclavian vein; it receives the transverse cervical and trans-
verse scapular veins, which form a plexus in front of the artery, and occasionally
a small vein which crosses the clavicle from the cephalic. The small nerve to the
Subclavius also crosses this triangle about its middle, and some lymph glands are
usually found in the space.
' The remark made about the inferior carotid triangle applies also to this one. The structures enumerated as con-
tained in its posterior part lie, strictly speaking, beneath the muscles which form the posterior boundan,' of the tri-
angle; but as it is very important to bear in mind their close relation to the parotid gland, all these parts are spoken
of together.
566
ANGIOLOGY
The Internal Carotid Artery (A. Carotis Interna) (Fig. 513).
The internal carotid artery supplies the anterior part of the brain, the eye and its
appendages, and sends branches to the forehead and nose. Its size, in the adult,
is equal to that of the external carotid, though, in the child, it is larger than that
First acrtic intercostal
FiQ. 513. — The internal carotid and vertebral arteries. Right side.
vessel. It is remarkable for the number of curvatures that it presents in different
parts of its course. It occasionally has one or two flexures near the base of the skull,
while in its passage through the carotid canal and along the side of the body of
the sphenoid bone it describes a double curvature and resembles the italic letter *S.
THE INTERNAL CAROTID ARTERY 567
Course and Relations. — In considering the course and relations of this vessel
it may be divided into four portions: cervical, petrous, cavernous, and cerebral.
Cervical Portion. — This portion of the internal carotid begins at the bifurca-
tion of the common carotid, opposite the upper border of the thyroid cartilage,
and runs perpendicularly upward, in front of the transverse processes of the upper
three cervical vertebrie, to the carotid canal in the petrous portion of the temporal
bone. It is comparatively superficial at its commencement, where it is contained
in the carotid triangle, and lies behind and lateral to the external carotid, over-
lapped by the Sternocleidomastoideus, and covered by the deep fascia, Platysma,
and integument: it then passes beneath the parotid gland, being crossed by the
hypoglossal nerve, the Digastricus and Stylohyoideus, and the occipital and pos-
terior auricular arteries. Higher up, it is separated from the external carotid by
the Styloglossus and Stylopharyngeus, the tip of the styloid process and the stylo-
hyoid ligament, the glossopharyngeal nerve and the pharyngeal branch of the vagus.
It is in relation, behind, with the Longus capitis, the superior cervical ganglion of
the sympathetic trunk, and the superior laryngeal nerve; laterally, with the internal
jugular vein and vagus nerve, the nerve lying on a plane posterior to the artery;
medially, with the pharynx, superior laryngeal nerve, and ascending pharyngeal
artery. At the base of the skull the glossopharyngeal, vagus, accessory, and hypo-
glossal nerves lie between the artery and the internal jugular vein.
Petrous Portion. — When the internal carotid artery enters the canal in the
petrous portion of the temporal bone, it first ascends a short distance, then curves
forward and medialward, and again ascends as it leaves the canal to enter the
cavity of the skull between the lingula and petrosal process of the sphenoid. The
artery lies at first in front of the cochlea and tympanic cavity; from the latter
cavity it is separated by a thin, bony lamella, which is cribriform in the young
subject, and often partly absorbed in old age. Farther forward it is separated
from the semilunar ganglion by a thin plate of bone, which forms the floor of the
fossa for the ganglion and the roof of the horizontal portion of the canal. Fre-
quently this bony plate is more or less deficient, and then the ganglion is separated
from the artery by fibrous membrane. The artery is separated from the bony wall
of the carotid canal by a prolongation of dura mater, and is surrounded by a number
of small veins and by filaments of the carotid plexus, derived from the ascending
branch of the superior cervical ganglion of the sympathetic trunk.
Cavernous Portion. — In this part of its course, the artery is situated between
the layers of the dura mater forming the cavernous sinus, but covered by the lining
membrane of the sinus. It at first ascends toward the posterior clinoid process,
then passes forward by the side of the body of the sphenoid bone, and again curves
upward on the medial side of the anterior clinoid process, and perforates the dura
mater forming the roof of the sinus. This portion of the artery is surrounded by
filaments of the sympathetic nerve, and on its lateral side is the abducent nerve.
Cerebral Portion. — Having perforated the dura mater on the medial side of
the anterior clinoid process, the internal carotid passes between the optic and oculo-
motor nerves to the anterior perforated substance at the medial extremity of the
lateral cerebral fissure, where it gives oft' its terminal or cerebral branches.
Peculiarities. — The length of the internal carotid varies according to the length of the neck,
and also according to the point of bifurcation of the common carotid. It arises sometimes from
the arch of the aorta; in such rare instances, this vessel has been found to be placed nearer the
middle line of the neck than the external carotid, as far upward as the larynx, when the latter
vessel crossed the internal carotid. The course of the artery, instead of being straight, may be
very tortuous. A few instances are recorded in which this vessel was altogether absent; in one
of these the common carotid passed up the neck, and gave off the usual branches of the external
carotid; the cranial portion of the internal carotid was replaced by two branches of the internal
maxillary, which entered the skull through the foramen rotundum and foramen ovale, and joined
to form a single vessel-
L
568 ANGIOLOGY
Branches. — The cervical portion of the internal carotid gives off no branches.
Those from the other portions are :
r, .1 -n A n J- (Caroticotympanic.
rrom the Fetrous r onion 'i a j. £ ^u t»x • i /-> i
(Arterv ot the rtervgoid Canal.
From the Cavernous Portion
From the Cerebral Portion
Cavernous.
Hypophyseal.
Semilunar.
Anterior JNIeningeal.
Ophthalmic.
Anterior Cerebral.
Middle Cerebral.
Posterior Communicating.
Choroidal.
1. The caroticotympanic branch {ramus caroticotympanicus; tympanic branch)
is small; it enters the tympanic cavity through a minute foramen in the carotid
canal, and anastomoses with the anterior tympanic branch of the internal maxillary,
and Avith the stylomastoid artery.
2. The artery of the pterygoid canal (a. canilis pterygoidei [Vidii]; Vidian artery)
is a small, inconstant branch which passes into the pterygoid canal and anas-
tomoses with a branch of the internal maxillary artery.
3. The cavernous branches are numerous small vessels which supply the
hypophysis, the semilunar ganglion, and the walls of the cavernous and inferior
petrosal sinuses. Some of them anastomose with branches of the middle meningeal.
4. The h3T)ophyseal branches are one or two minute vessels supplying the
hypophysis.
5. The semilunar branches are small vessels to the semilunar ganglion.
6. The anterior meningeal branch (a. meningea anterior) is a small branch which
passes over the small wing of the sphenoid to supply the dura mater of the anterior
cranial fossa; it anastomoses with the meningeal branch from the posterior eth-
moidal artery.
7. The ophthalmic artery (a. ophthalinica) (Fig. 514) arises from the internal
carotid, just as that vessel is emerging from the cavernous sinus, on the medial
side of the anterior clinoid process, and enters the orbital cavity through the optic
foramen, below and lateral to the optic nerve. It then passes over the nerve to
reach the medial wall of the orbit, and thence horizontally forward, beneath the
lower border of the Obliquus superior, and divides it into two terminal branches,
the frontal and dorsal nasal. As the artery crosses the optic nerve it is accompanied
by the nasociliary nerve, and is separated from the frontal nerve by the Rectus
superior and Levator palpebrae superioris.
Branches. — The branches of the ophthalmic artery may be divided into an orbital
group, distributed to the orbit and surrounding parts; and an ocular group, to the
muscles and bulb of the eye.
Orbital Group. Ocular Group.
Lacrimal. Central Artery of the Retina.
Supraorbital. Short Posterior Ciliary.
Posterior Ethmoidal. Long Posterior Cihary.
Anterior Ethmoidal. Anterior Ciliary.
Medial Palpebral. Muscular.
Frontal.
Dorsal Nasal.
THE INTERNAL CAROTID ARTERY
569
The Lacrimal Artery (a. lacrimalu) arises close to the optic foramen, and is one
of the largest branches derived from the ophthalmic: not infrequently it is given
off before the artery enters the orbit. It accompanies the lacrimal ner^'e along
the upper border of the Rectus lateralis, and supplies the lacrimal gland. Its
terminal branches, escaping from the gland, are distributed to the eyelids and con-
junctiva: of those supplying the eyelids, two are of considerable size and are named
the lateral palpebral arteries; they run mediaiward in the upper and lower lids
respectively and anastomose with the medial palpebral arteries, forming an arterial
circle in this situation. The lacrimal artery give off one or two zygomatic branches,
one of which passes through the zygomatico-temporal foramen, to reach the tem-
poral fossa, and anastomoses with the deep temporal arteries; another appears
on the cheek through the zygomatico-facial foramen, and anastomoses with the
transverse facial. A recurrent branch passes backward through the lateral part of
the superior orbital fissure to the dura mater, and anastomoses with a branch of
the middle meningeal artery. The lacrimal artery is sometimes derived from one
of the anterior branches of the middle meningeal artery.
Dorsal nasal Medial palpebral
Supraorbital
Anterior ethmoidal
Posterior ethmoidal
■^^*- / Zygomatic branches
^*^ y of lacrimal
Arteria
centralis retiruB
Lacrimal
Muscular
Ophthalmic
Internal carotid
Fig. 514. — The ophthalmic artery and its branches.
The Supraorbital Artery (a. supraorbitalis) springs from the ophthalmic as that
vessel is crossing over the optic nerve. It passes upward on the medial borders
of the Rectus superior and Levator palpebrse, and meeting the supraorbital nerve
accompanies it between the periosteum and Levator palpebral to the supraorbital
foramen; passing through this it divides into a superficial and a deep branch,
which supply the integument, the muscles, and the pericranium of the forehead,
anastomosing with the frontal, the frontal branch of the superficial temporal, and
the artery of the opposite side. This artery in the orbit supplies the Rectus superior
and the Levator palpebrae, and sends a branch across the pulley of the Obliquus
superior, to supply the parts at the medial palpebral commissure. At the supra-
orbital foramen it frequently transmits a branch to the diploe.
570
ANGIOLOGY
The Ethmoidal Arteries are two in number: posterior and anterior. The posterior
ethmoidal artery, the smaller, passes through the posterior ethmoidal canal, supplies
the posterior ethmoidal cells, and, entering the cranium, gives off a meningeal
branch to the dura mater, and nasal branches which descend into the nasal cavity
through apertures in the cribriform plate, anastomosing with branches of the
sphenopalatine. The anterior ethmoidal artery accompanies the nasociliary nerve
through the anterior ethmoidal canal, supplies the anterior and middle ethmoidal
cells and frontal sinus, and, entering the cranium, gives off a meningeal branch
to the dura mater, and nasal branches; these latter descend into the nasal cavity
through the slit by the side of the crista galli, and, running along the groove on
the inner surface of the nasal bone, supply branches to the lateral wall and septum
of the nose, and a terminal branch which appears on the dorsum of the nose between
the nasal bone and the lateral cartilage.
11 4
Fig. 515. — Bloodvessels of the eyelids, front \-iew. 1, supraorbital artery and vein; 2, nasal artery; 3, angular artery,
the terminal branch of 4, the facial artery; 5, suborbital arterj-; 6, anterior branch of the superficial temporal arterj-;
6', malar branch of the transverse artery of the face; 7, lacrimal arterj-; 8, superior palpebral artery with 8', its external
arch; 9, anastomoses of the superior palpebral with the superficial temporal and lacrimal; 10, inferior palpebral artery;
11, facial vein: 12, angular vein; 13, branch of the superficial temporal vein. (Testut.)
The Medial Palpebral Arteries (aa. palpehrales mediales; internal 'palpebral
arteries), two in number, superior and inferior, arise from the ophthalmic, opposite
the pulley of the Obliquus superior; they leave the orbit to encircle the eyelids
near their free margins, forming a superior and an inferior arch, which lie between
the Orbicularis oculi and the tarsi. The superior palpebral anastomoses, at the
lateral angle of the orbit, with the zygomaticoorbital branch of the temporal artery
and with the upper of the two lateral palpebral branches from the lacrimal artery;
the inferior palpebral anastomoses, at the lateral angle of the orbit, with the lower
of the two lateral palpebral branches from the lacrimal and with the transverse
facial artery, and, at the medial part of the lid, with a branch from the angular
artery. From this last anastomoses a branch passes to the nasolacrimal duct,
ramifying in its mucous membrane, as far as the inferior meatus of the nasal
cavity.
The Frontal Artery (a. frontalis), one of the terminal branches of the ophthalmic,
leaves the orbit at its medial angle with the supratrochlear nerve, and, ascending
THE INTERNAL CAROTID ARTERY 571
on the forehead, supphes the integument, muscles, and pericranium, anastomosing
with the supraorbital artery, and with the artery of the opposite side.
The Dorsal Nasal Artery (a. dorsalis nasi; }msal artery), the other terminal branch
of the ophthalmic, emerges from the orbit above the medial palpebral ligament,
and, after giving a twig to the upper part of the lacrimal sac, divides into two
branches, one of which crosses the root of the nose, and anastomoses with the
angular artery, the other runs along the dorsum of the nose, supplies its outer
surface; and anastomoses Avith the artery of the opposite side, and with the lateral
nasal branch of the external maxillary.
The Central Artery of the Retina (a. centralis retina') is the first and one of the
smallest l)ranches of the ophthalmic artery. It runs for a short distance within
the dural sheath of the optic nerve, but about 1.25 cm. behind the eyeball it pierces
the nerve obliquely, and runs forward in the center of its substance to the retina.
Its mode of distribution will be described with the anatomy of the eye.
The Ciliary Arteries {aa. ciliares) are divisible into three groups, the long and short,
posterior, and the anterior. The short posterior ciliary arteries from six to twelve
in number, arise from the ophthalmic, or its branches; they pass forward around the
optic nerve to the posterior part of the eyeball, pierce the sclera around the entrance
of the nerve, and supply the choroid and ciliary processes. The long posterior
ciliary arteries, two in number, pierce the posterior part of the sclera at some little
distance from the optic nerve, and run forward, along either side of the eyeball,
between the sclera and choroid, to the ciliary muscle, where they divide into two
branches; these form an arterial circle, the circulus arteriosus major, around the
circumference of the iris, from which numerous converging branches run, in the
substance of the iris, to its pupillary margin, where they form a second arterial
circle, the circulus arteriosus minor. The anterior ciliary arteries are derived from
the muscular branches; they run to the front of the eyeball in company with the
tendons of the Recti, form a vascular zone beneath the conjunctiva, and then pierce
the sclera a short distance from the cornea and end in the circulus arteriosus major.
The Muscular Branches, [rami muscularcs), two in number, superior and inferior,
frequently spring from a common trunk. The superior, often wanting, supplies
the Levator palpebra? superioris, Rectus superior, and Obliquus superior. The
inferior, more constantly present, passes forward between the optic nerve and Rectus
inferior, and is distributed to the Recti lateralis, medialis, and inferior, and the
Obliquus inferior. This vessel gives off most of the anterior ciliary arteries. Addi-
tional muscular branches are given off from the lacrimal and supraorbital arteries,
or from the trunk of the ophthalmic.
8. The anterior cerebral artery (a. cerebri anterior) (Figs. 516, 517, 518) arises
from the internal carotid, at the medial extremity of the lateral cerebral fissure.
It passes forward and medialward across the anterior perforated substance, above
the optic nerve, to the commencement of the longitudinal fissure. Here it comes
into close relationship with the opposite artery, to which it is connected by a short
trunk, the anterior communicating artery. From this point the two vessels run side
by side in the longitudinal fissure, curve around the genu of the corpus callosum,
and turning backward continue along the upper surface of the corpus callosum
to its posterior part, where they end by anastomosing with the posterior cerebral
arteries.
Branches. — In its course the anterior cerebral artery gives off the following
branches :
Antero-medial Ganglionic. Anterior. Posterior.
Inferior. Middle.
The Antero-medial Ganglionic Branches are a group of small arteries which arise
at the commencement of the anterior cerebral artery; they pierce the anterior
b
572
ANGIOLOGY
perforated substance and lamina terminalis, and supply the rostrum of the corpus
callosum, the septum pellucidum, and the head of the caudate nucleus. The
inferior branches, two or three in number, are distributed to the orbital surface of
the frontal lobe, where they supply the olfactory lobe, gyrus rectus, and internal
orbital gyrus. The anterior branches supply a part of the superior frontal gyrus,
and send twigs over the edge of the hemisphere to the superior and middle frontal
gyri and upper part of the anterior central gyrus. The middle branches supply
the corpus callosum, the cingulate gyrus, the medial surface of the superior frontal
gyrus, and the upper part of the anterior central gyrus. The posterior branches
supply the precuneus and adjacent lateral surface of the hemisphere.
Fig. 516. — The arteries of the base of the brain. The tempora pole of the cerebrum and a portion of the cerebellar
hemisphere have been removed on the right side.
The Anterior Communicating Artery (a. communicans anterior) connects the two
anterior cerebral arteries across the commencement of the longitudinal fissure.
Sometimes this vessel is wanting, the two arteries joining together to form a
single trunk, which afterward divides; or it may be wholly, or partially, divided
into two. Its length averages about 4 mm., but varies greatly. It gives off some
of the antero-medial ganglionic vessels, but these are principally derived from the
anterior cerebral.
9. The middle cerebral artery (a. cerebri media) (Figs. 516, 517), the largest
branch of the internal carotid, runs at first lateralward in the lateral cerebral or
Sylvian fissure and then backward and upward on the surface of the insula, where
THE INTERNAL CAROTID ARTERY
573
it divides into a number of branches which are distributed to the lateral surface
of the cerebral hemisphere.
Branches. — The branches of this vessel are the:
Antero-lateral Ganglionic.
Inferior Lateral Frontal.
Ascending Frontal.
Ascending Parietal.
Parietotemporal.
Temporal.
Fig. 517. — Outer surface of cerebral hemisphere, showing areas supplied by cerebral arteries.
The Antero-lateral Ganglionic Branches, a group of small arteries which arise at
the commencement of the middle cerebral artery, are arranged in two sets: one,
the internal striate, passes upward through the inner segments of the lentiform
nucleus, and supplies it, the caudate nucleus, and the internal capsule; the other,
the external striate, ascends through the outer segment of the lentiform nucleus,
and supplies the caudate nucleus and the thalamus. One artery of this group
is of larger size than the rest, and is of special importance, as being the artery in
the brain most frequently ruptured; it has been termed by Charcot the artery
of cerebral hemorrhage. It ascends between the lentiform nucleus and the external
capsule, and ends in the caudate nucleus. The inferior lateral frontal supplies
Fig. 518. — Medial surface of cerebral hemisphere, showing areas supplied by cerebral arteries.
the inferior frontal gyrus {Broca's convolution) and the lateral part of the orbital
surface of the frontal lobe. The ascending frontal supplies the anterior central
gyrus. The ascending parietal is distributed to the posterior central gyrus and the
lower part of the superior parietal lobule. The parietotemporal supplies the supra-
marginal and angular gyri, and the posterior parts of the superior and middle
temporal gyri. The temporal branches, two or three in number, are distributed
to the lateral surface of the temporal lobe.
10. The posterior commimicatiaig artery (a. communicans posterior) (Fig. 516)
runs backward from the internal carotid, and anastomoses with the posterior
574
ANGIOLOGY
cerebral, a branch of the basilar. It varies in size, being sometimes small, and occa-
sionally so large that the posterior cerebral may be considered as arising from the
internal carotid rather than from the basilar. It is frequently larger on one side
than on the other. From its posterior half are given off a number of small branches,
the postero-medial ganglionic branches, which, with similar vessels from the posterior
cerebral, pierce the posterior perforated substance and supply the medial surface
of the thalami and the walls of the third ventricle.
11. The anterior choroidal (a. chorioidea; choroid artery) is a small but constant
branch, which arises from the internal carotid, near the posterior communicating
artery. Passing backward and lateralward between the temporal lobe and the
cerebral peduncle, it enters the inferior horn of the lateral ventricle through the
choroidal fissure and ends in the choroid plexus. It is distributed to the hippo-
campus, fimbria, tela chorioidea of the third ventricle, and choroid plexus.
Ant. comm'Wnicating
Ant. cerebral
Post com-
municating
Internnl
auditory
THE ARTERIES OF THE BRAIN.
Since the mode of distribution of the vessels of the brain has an important
bearing upon a considerable number of the pathological lesions which may occur
in this part of the nervous system, it is im-
portant to consider a little more in detail the
manner in which the vessels are distributed.
The cerebral arteries are derived from the
internal carotid and vertebral, which at the
base of the brain form a remarkable anasto-
mosis known as the arterial circle of Willis.
It is formed in front by the anterior cere-
bral arteries, branches of the internal carotid,
which are connected together by the anterior
communicating; behind by the two posterior
cerebral arteries, branches of the basilar,
which are connected on either side with the
internal carotid by the posterior commu-
nicating (Figs. 516, 519). The parts of the
brain included within this arterial circle are
the lamina terminalis, the optic chiasma,
the infundibulum, the tuber cinereum, the
corpora mammillaria, and the posterior
perforated substance.
The three trunks which together supply
each cerebral hemisphere arise from the
arterial circle of Willis. From its anterior
part proceed the two anterior cerebrals,
from its antero-lateral parts the middle
cerebrals, and from its posterior part the
posterior cerebrals. Each of these prin-
cipal arteries gives origin to two different
systems of secondary vessels. One of these is named the ganglionic system, and the
vessels belonging to it supply the thalami and corpora striata ; the other is the cortical
system, and its vessels ramify in the pia mater and supply the cortex and subjacent
brain substance. These two systems do not communicate at any point of their
peripheral distribution, but are entirely independent of each other, and there is
between the parts supplied by the two systems a borderland of diminished
nutritive activity, where, it is said, softening is especially liable to occur in the
brains of old people.
Posterior
inferior
cerebellar
Fig. 519. — Diagram of the arterial circulation at
the base of the brain. A.L. Antero-lateral. A.M.
Antero-medial. P.L. Postero-lateral. P.M. Postero-
medial ganglionic branches.
THE SUBCLAVIAN ARTERY 575
The Ganglionic System. — All the vessels of this system are given off from the
arterial circle of Willis, or from the vessels close to it. They form six principal
groups: (I) the antero-medial group, derived from the anterior cerebrals and anterior
communicating; (II) the postero-medial group, from the posterior cerebrals and
posterior communicating; (III and IV) the right and left antero-lateral groups,
from the middle cerebrals; and (V and VI) the right and left postero-lateral
groups, from the posterior cerebrals, after they have wound arouncl the cerebral
peduncles. The vessels of this system are larger than those of the cortical system,
and are what Cohnheim designated terminal arteries — that is to say, vessels which
from their origin to their termination neither supply nor receive any anastomotic
branch, so that, through any one of the vessels only a limited area of the thalamus
or corpus striatum can be injected, and the injection cannot be driven beyond the
area of the part supplied by the particular vessel which is the subject of the
experiment.
The Cortical Arterial System. — The vessels forming this system are the terminal
branches of the anterior, middle, and posterior cerebral arteries. They divide
and ramify in the substance of the pia mater, and give off branches which penetrate
the brain cortex, perpendicularly. These branches are divisible into two classes,
long and short. The long, or medullary arteries, pass through the gray substance
and penetrate the subjacent white substance to the depth of 3 or 4 cm., without
intercommunicating otherwise than by very fine capillaries, and thus constitute
so many independent small systems. The short vessels are confined to the cortex,
where they form with the long vessels a compact net-work in the middle zone
of the gray substance, the outer and inner zones being sparingly supplied with
blood. The vessels of the cortical arterial system are not so strictly "terminal"
as those of the ganglionic system, but they approach this type very closely, so
that injection of one area from the vessel of another area, though possible, is
frequently very difficult, and is only effected through vessels of small caliber. As
a result of this, obstruction of one of the main branches, or its divisions, may have
the effect of producing softening in a limited area of the cortex.
THE ARTERIES OF THE UPPER EXTREMITY.
The artery which supplies the upper extremity continues as a single trunk
from its commencement down to the elbow ; but different portions of it have received
different names, according to the regions through which they pass. That part
of the vessel which extends from its origin to the outer border of the first rib is
termed the subclavian; beyond this point to the lower border of the axilla it is
named the axillary; and from the lower margin of the axillary space to the bend
of the elbow it is termed brachial ; here the trunk ends by dividing into two branches
the radial and ulnar.
THE SUBCLAVIAN ARTERY (A. SUBCLAVIA) (Fig. 520).
On the right side the subclavian artery arises from the innominate artery behind
the right sternoclavicular articulation; on the left side it springs from the arch
of the aorta. The two vessels, therefore, in the first part of their course, differ
in length, direction, and relation with neighboring structures.
In order to facilitate the description, each subclavian artery is divided into
three parts. The first portion extends from the origin of the vessel to the medial
border of the Scalenus anterior; the second lies behind this muscle; and the third
extends from the lateral margin of the muscle to the outer border of the first rib,
where it becomes the axillary artery. The first portions of the two vessels require
separate descriptions; the second and third parts of the two arteries are practically
alike.
576
ANGIOLOGY
First Part of the Right Subclavian Artery (Figs. 505, 520).— The first part of
the right subclavian artery arises from the innominate artery, behind the upper
part of the right sternoclavicuUir articulation, and passes upward and lateralward
to the medial margin of the Scalenus anterior. It ascends a little above the clavicle,
the extent to which it does so varying in different cases.
Fig. 520. — Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.
Relations. — It is covered, in front, by the integument, superficial fascia, Platysma, deep fascia,
the clavicular origin of the Stemocleidomastoideus, the Sternohyoideus, and SternothjTeoideus,
and another layer of the deep fascia. It is crossed bj- the internal jugular and vertebral veins,
by the vagus nerve and the cardiac branches of the vagus and sj-mpathetic, and by the sub-
clavian loop of the sympathetic trimk which forms a ring around the vessel. The anterior jugular
vein is directed lateralward in front of the artery, but is separated from it by the Sternohyoideus
and Sternothyreoideus. Below and behind the artery is the pleura, which separates it from the
apex of the lung; behind is the sympathetic trimk, the Longus colli and the first thoracic vertebra.
The right recurrent nerve winds around the lower and back part of the vessel.
THE SUBCLAVIAN ARTERY 577
First Part of the Left Subclavian Artery (Fig. 505).— The first part of the left
subclavian artery arises from the arch of the aorta, behind the left common carotid,
and at the level of the fourth thoracic vertebra ; it ascends in the superior medias-
tinal cavity to the root of the neck and then arches lateralward to the medial
border of the Scalenus anterior.
Relations. — It is in relation, in front, with tlie vagus, cardiac, and phrenic nerves, which lie
parallel with it, the left common carotid artery, left internal jugular and vertebral veins, and
the commencement of the left innominate vein, and is covered by the SternothjTeoideus, Sterno-
hyoideus, and Sternocleidomastoideus; behind, it is in relation with the esophagus, thoracic
duct, left recurrent nerve, inferior cervical ganghon of the sympathetic trunk, and Longus colli;
higher up, however, the esophagus and thoracic duct lie to its right side; the latter ultimately
arching over the vessel to join the angle of union between the subclavian and internal jugular
veins. Medial to it are the esophagus, trachea, thoracic duct, and left recurrent nerve; lateral
to it, the left pleura and lung.
Second and Third Parts of the Subclavian Artery (Fig. 520). — The second
portion of the subclavian artery lies behind the Scalenus anterior; it is very short,
and forms the highest part of the arch described by the vessel.
Relations. — It is covered, in front, by the skin, superficial fascia, Platysina, deep cervical
fascia, Sternocleidomastoideus, and Scalenus anterior. On the right side of the neck the
phrenic nerve is separated from the second part of the artery by the Scalenus anterior, while
on the left side it crosses the first part of the artery close to the medial edge of the muscle.
Behind the vessel are the pleura and the Scalenus medius; above, the brachial plexus of nerves;
below, the pleura. The subclavian vein lies below and in front of the artery, separated from it
by the Scalenus anterior.
The third portion of the subclavian artery runs downward and lateralward from
the lateral margin of the Scalenus anterior to the outer border of the first rib,
where it becomes the axillary artery. This is the most superficial portion of the
vessel, and is contained in the subclavian triangle (see page 565).
Relations. — It is covered, in front, by the skin, the superficial fascia, the Platysma, the supra-
clavicular nerves, and the deep cervical fascia. The external jugular vein crosses its medial
part and receives the transverse scapular, transverse cervical, and anterior jugular veins, which
frequently form a plexus in front of the artery. Behind the veins, the nerve to the Subclavius
descends in front of the artery. The terminal part of the artery lies behind the clavicle and the
Subclavius and is crossed by the transverse scapular vessels. The subclavian vein is in front
of and at a sUghtly lower level than the artery. Behind, it lies on the lowest trunk of the brachial
plexus, which intervenes between it and the Scalenus medius. Above and to its lateral side are
the upper trunks of the brachial plexus and the Omohyoideus. Below, it rests on the upper
surface of the first rib.
Peculiarities. — The subclavian arteries vary in their origin, their course, and the height to
which the}' rise in the neck.
The origin of the right subclavian from the innominate takes place, in some cases, above the
sternoclavicular articulation, and occasionally, but less frequently, below that joint. The artery
may arise as a separate trunk from the arch of the aorta, and in such cases it may be either the
first, second, third, or even the last branch derived from that vessel; in the majority, however,
it is the first or last, rarely the second or third. When it is the first branch, it occupies the ordinary
position of the innominate artery; when the second or third, it gains its usual position by passing
behind the right carotid; and when the last branch, it arises from the left extremity of the arch,
and passes obhquely toward the right side, usually behind the trachea, esophagus, and right
carotid, sometimes between the esophagus and trachea, to the upper border of the first rib,
whence it follows its ordinary course. In very rare instances, this vessel arises from the thoracic
aorta, as low down as the fourth thoracic vertebra. Occasionally, it perforates the Scalenus
anterior; more rarely it passes in front of that muscle. Sometimes the subclavian vein passes
with the artery behind the Scalenus anterior. The artery may ascend as high as 4 cm. above
the clavicle, or any intermediate point between this and the upper border of the bone, the right
subclavian usually ascending higher than the left.
The left subclavian is occasionally joined at its origin with the left carotid.
The left subclavian artery is more deeply placed than the right in the first part of its course,
and, as a rule, does not reach quite as high a level in the neck. The posterior border of the Sterno-
cleidomastoideus corresponds pretty closely to the lateral border of the Scalenus anterior, so
that the third portion of the artery, the part most accessible for operation, lies immediately
lateral to the posterior border of the Sternocleidomastoideus.
37
578 ANGIOLOGY
Collateral Circulation. — After ligature of the third part of the subclavian artery, the collateral
circulation is established mainly by three sets of vessels, thus described in a dissection:
1. A posterior set, consisting of the transverse scapular and the descending ramus of the trans-
verse cervical branches of the subclavian, anastomosing with the subscapular from the axillary.
2. A medial set, produced by the connection of the internal mammary on the one hand, with
the highest intercostal and lateral thoracic arteries, and the branches from the subscapular on
the other.
3. A middle or axillary set, consisting of a number of small vessels derived from branches of
the subclavian, above, and, passing through the axilla, terminating either in the main trunk,
or some of the branches of the axillary below. This last set presented most conspicuously the
pecuMar character of newly formed or, rather, dilated arteries, being excessively tortuous, and
forming a complete plexus.
The chief agent in the restoration of the axillary artery below the tumor was the subscapular
artery, which communicated most freely with the internal mammary, transverse scapular and
descending ramus of the transverse cervical branches of the subclavian, from all of which it
received so great an influx of blood as to dilate it to three times its natural size.^
When a ligature is applied to the first part of the subclavian artery, the collateral circulation is
carried on by: (1) the anastomosis between the superior and inferior thyroids; (2) the anastomosis
of the two vertebrals; (3) the anastomosis of the internal mammary with the inferior epigastric
and the aortic intercostals; (4) the costocervical anastomosing with the aortic intercostals; (5)
the profunda cervicis anastomosing with the descending branch of the occipital; (6) the scapular
branches of the thyrocervical trunk anastomosing with the branches of the axillary, and (7) the
thoracic branches of the axillary anastomosing with the aortic intercostals.
Branches. — The branches of the subclavian artery are:
Vertebral. Internal mammary.
Thyrocervical. Costocervical.
On the left side all four branches generally arise from the first portion of the
vessel; but on the right side (Fig. 520) the costocervical trunk usually springs
from the second portion of the vessel. On both sides of the neck, the first three
branches arise close together at the medial border of the Scalenus anterior; in
the majority of cases, a free interval of from 1.25 to 2.5 cm. exists between the
commencement of the artery and the origin of the nearest branch.
1. The vertebral artery (a. vertebralis) (Fig. 514), is the first branch of the sub-
clavian, and arises from the upper and back part of the first portion of the vessel.
It is surrounded by a plexus of nerve fibers derived from the inferior cervical
ganglion of the sympathetic trunk, and ascends through the foramina in the
transverse processes of the upper six cervical vertebrse;- it then winds behind the
superior articular process of the atlas and, entering the skull through the foramen
magnum, unites, at the lower border of the pons, with the vessel of the opposite
side to form the basilar artery.
Relations. — The vertebral artery may be divided into four parts: The first part runs upward
and backward between the Longus colli and the Scalenus anterior. In front of it are the internal
jugular and vertebral veins, and it is crossed by the inferior th>Toid artery; the left vertebral
is crossed by the thoracic duct also. Behind it are the transverse process of the seventh cervical
vertebra, the sympathetic trunk and its inferior cervical ganghon. The second part runs upward
through the foramina in the transverse processes of the upper six cervical vertebrte, and is sur-
rounded by branches from the inferior cervical sympathetic ganghon and by a plexus of veins
which unite to form the vertebral vein at the lower part of the neck. It is situated in front of
the trunks of the cervical nerves, and pursues an almost vertical course as far as the transverse
process of the atlas, above which it runs upward and lateralward to the foramen in the trans-
verse process of the atlas. The third part issues from the latter foramen on the medial side of
the Rectus capitis lateraUs, and curves backward behind the superior articular process of the
atlas, the anterior ramus of the first cervical nerve being on its medial side; it then lies in the
groove on the upper surface of the posterior arch of the atlas, and enters the vertebral canal
by passing beneath the posterior atlantooccipital membrane. This part of the artery is covered
by the Semispinalis capitis and is contained in the suboccipital triangle — a triangular space
1 Guy's Hospital Reports, vol. i, 1836. Case of axillarj- aneurism, in which Aston Key had tied the subclavian
artery on the lateral edge of the Scalenus anterior, twelve years previously.
'' The vertebral artery sometimes enters the foramen in the transverse process of the fifth vertebra, and has been
seen entering that of the seventh vertebra.
THE SUBCLAVIAN ARTERY 579
bounded by the Rectus capitis posterior major, the Obliquus superior, and the Obh'quus inferior.
The first cervical or suboccipital nerve Mes between the artery and the posterior arch of the atlas.
The fourth part pierces the dura mater and inclines mcdialward to the front of the medulla
oblongata; it is placed between the hypoglossal nerve and the anterior root of the first cervical
nerve and beneath the first digitation of the ligamentum denticulatum. At the lower border
of the pons it unites with the vessel of the opposite side to form the basilar artery.
Branches.— The branches of the vertebral artery may be divided into two sets:
those given oft' in the neck, and those within the cranium.
Cervical Branches. Cranial Branches.
Spinal. Meningeal.
IMuscular. Posterior Spinal.
Anterior Spinal.
Posterior Inferior Cerebellar.
Medullary.
Spinal Branches (rami spinales) enter the vertebral canal through the interverte-
bral foramina, and each divides into two branches. Of these, one passes along
the roots of the nerves to supply the medulla spinalis and its membranes, anasto-
mosing with the other arteries of the medulla spinalis; the other divides into an
ascending and a descending branch, which unite with similar branches from the
arteries above and below, so that two lateral anastomotic chains are formed on the
posterior surfaces of the bodies of the vertebrae, near the attachment of the pedicles.
From these anastomotic chains branches are supplied to the periosteum and the
bodies of the vertebrae, and others form communications with similar branches from
the opposite side; from these communications small twigs arise which join similar
branches above and below, to form a central anastomotic chain on the posterior
surface of the bodies of the vertebrae.
Muscular Branches are given oft" to the deep muscles of the neck, where the
vertebral artery curves around the articular process of the atlas. They anastomose
with the occipital, and with the ascending and deep cervical arteries.
The Meningeal Branch {ramus meningeus; posterior meningeal branch) springs
from the vertebral opposite the foramen magnum, ramifies between the bone
and dura mater in the cerebellar fossa, and supplies the falx cerebelli. It is fre-
quently represented by one or two small branches.
The Posterior Spinal Artery (a. spinalis posterior; dorsal spinal artery) arises
from the vertebral, at the side of the medulla oblongata; passing backward, it
descends on this structure, lying in front of the posterior roots of the spinal nerves,
and is reinforced by a succession of small branches, which enter the vertebral
canal through the intervertebral foramina; by means of these it is continued to
the lower part of the medulla spinalis, and to the cauda equina. Branches from
the posterior spinal arteries form a free anastomosis around the posterior roots
of the spinal nerves, and communicate, by means of very tortuous transverse
branches, with the vessels of the opposite side. Close to its origin each gives off
an ascending branch, which ends at the side of the fourth ventricle.
The Anterior Spinal Artery (a. spinalis anterior; ventral spinal artery) is a small
branch, which arises near the termination of the vertebral, and, descending in
front of the medulla oblongata, unites with its fellow of the opposite side at the
level of the foramen magnum. One of these vessels is usually larger than the other,
but occasionally they are about equal in size. The single trunk, thus formed,
descends on the front of the medulla spinalis, and is reinforced by a succession
of small branches which enter the vertebral canal through the intervertebral
foramina; these branches are derived from the vertebral and the ascending cervical
of the inferior thyroid in the neck; from the intercostals in the thorax; and from
the lumbar, iliolumbar, and lateral sacral arteries in the abdomen and pelvis.
They unite, by means of ascending and descending branches, to form a single
580 ANGIOLOGY
anterior median artery, which extend as far as the lower part of the medulla spinalis,
and is continued as a slender twig on the filum terminale. This vessel is placed
in the pia mater along the anterior median fissure; it supplies that membrane, and
the substance of the medulla spinalis, and sends off branches at its lower part to
be distributed to the cauda equina.
The Posterior Inferior Cerebellar Artery (a. cereheUi inferior posterior) (Fig. 516),
the largest branch of the vertebral, winds backward around the upper part of the
medulla oblongata, passing between the origins of the vagus and accessory nerves,
over the inferior peduncle to the under surface of the cerebellum, where it divides
into two branches. The medial branch is continued backward to the notch between
the two hemispheres of the cerebellum; while the lateral supplies the under surface
of the cerebellum, as far as its lateral border, where it anastomoses with the anterior
inferior cerebellar and the superior cerebellar branches of the basilar artery.
Branches from this artery supply the choroid plexus of the fourth ventricle.
The Medullary Arteries (bulbar arteries) are several minute vessels which spring
from the vertebral and its branches and are distributed to the medulla oblongata.
The Basilar Artery (a. basilaris) (Fig. 516), so named from its position at the
base of the skull, is a single trunk formed by the junction of the two vertebral
arteries: it extends from the lower to the upper border of the pons, lying in its
median groove, under cover of the arachnoid. It ends by dividing into the two
posterior cerebral arteries.
Its branches, on either side, are the following:
Pontine. Anterior Inferior Cerebellar.
Internal Auditory. Superior Cerebellar.
Posterior Cerebral.
The pontine branches {rami ad po7item; transverse branches) are a number of small
vessels which come off at right angles from either side of the basilar artery and
supply the pons and adjacent parts of the brain.
The internal auditory artery (a. auditiva interna; auditory artery), a long slender
branch, arises from near the middle of the artery ; it accompanies the acoustic nerve
through the internal acoustic meatus, and is distributed to the internal ear.
The anterior inferior cerebellar artery (a. cerebelli inferior anterior) passes back-
ward to be distributed to the anterior part of the under surface of the cerebellum,
anastomosing with the posterior inferior cerebellar branch of the vertebral.
The superior cerebellar artery (a. cerebelli superior) arises near the termination
of the basilar. It passes lateralward, immediately below the oculomotor nerve,
which separates it from the posterior cerebral artery, winds around the cerebral
peduncle, close to the trochlear nerve, and, arriving at the upper surface of the
cerebellum, divides into branches which ramify in the pia mater and anastomose
with those of the inferior cerebellar arteries. Several branches are given to the
phieal body, the anterior medullary velum, and the tela chorioidea of the third
ventricle.
The posterior cerebral artery (a. cerebri posterior) (Figs. 516, 517, 518) is larger
than the preceding, from which it is separated near its origin by the oculomotor
nerve. Passing lateralward, parallel to the superior cerebellar artery, and receiving
the posterior communicating from the internal carotid, it winds around the cerebral
peduncle, and reaches the tentorial surface of the occipital lobe of the cerebrum,
where it breaks up into branches for the supply of the temporal and occipital lobes.
The branches of the posterior cerebral artery are divided into two sets, ganglionic
and cortical:
f Posterior-med ial .
Ganglionic i Posterior Choroidal. ^ ^. ,
IPostero-lateral. ^""'^''^^
Anterior Temporal.
Posterior Temporal.
Calcarine.
Parietooccipital.
THE SUBCLAVIAN ARTERY 581
Ganglicmic. — The postero-medial ganglionic branches (Fig. 519) are a group of
small arteries which arise at the commencement of the posterior cerebral artery:
these, with similar branches from the posterior communicating, pierce the pos-
terior perforated substance, and supply the medial surfaces of the thalami and the
walls of the third ventricle. The posterior choroidal branches run forward beneath
the splenium of the corpus callosum, and supply the tela chorioidea of the third
ventricle and the choroid plexus. The postero-lateral ganglionic branches are small
arteries which arise from the posterior cerebral artery after it has turned around the
cerebral peduncle; they supply a considerable portion of the thalamus.
Cortical. — The cortical branches are: the anterior temporal, distributed to the
uncus and the anterior part of the fusiform gyrus; the posterior temporal, to the
fusiform and the inferior temporal gyri; the calcarine, to the cuneus and gyrus
lingualis and the back part of the convex surface of the occipital lobe; and the
parietooccipital, to the cuneus and the precuneus.
2. The thyrocervical trunk (truncus thyreocervicalis; thyroid axis) (Fig. 520) is
a short thick trunk, which arises from the front of the first portion of the subclavian
artery, close to the medial border of the Scalenus anterior, and divides almost
immediately into three branches, the inferior thyroid, transverse scapular, and trans-
verse cervical.
The Inferior Thyroid Artery (a. thyreoidea inferior) passes upward, in front of the
vertebral artery and Longus colli ; then turns medialward behind the carotid sheath
and its contents, and also behind the sympathetic trunk, the middle cervical
ganglion resting upon the vessel. Reaching the lower border of the thyroid gland
it divides into two branches, which supply the postero-inferior parts of the gland,
and anastomose with the superior thyroid, and with the corresponding artery of
the opposite side. The recurrent nerve passes upward generally behind, but occa-
sionally in front, of the artery.
The branches of the inferior thyroid are :
Inferior Laryngeal.. Esophageal.
Tracheal. Ascending Cervical.
Muscular.
The inferior laryngeal artery (a. laryngea inferior) ascends upon the trachea to
the back part of the larynx under cover of the Constrictor pharyngis inferior, in
company with the recurrent nerve, and supplies the muscles and mucous mem-
brane of this part, anastomosing with the branch from the opposite side, and with
the superior laryngeal branch of the superior thyroid artery.
The tracheal branches {rami tracheales) are distributed upon the trachea, and
anastomose below with the bronchial arteries.
The esophageal branches {rami oesophagei) supply the esophagus, and anasto-
mose with the esophageal branches of the aorta.
The ascending cervical artery (a. cervicalis ascendens) is a small branch which
arises from the inferior thyroid as that vessel is passing behind the carotid sheath;
it runs up on the anterior tubercles of the transverse processes of the cervical
vertebrae in the interval between the Scalenus anterior and Longus capitis. To
the muscles of the neck it gives twigs which anastomose with branches of the ver-
tebral, and it sends one or two spinal branches into the vertebral canal through
the intervertebral foramina to be distributed to the medulla spinalis and its mem-
branes, and to the bodies of the vertebrae, in the same manner as the spinal branches
from the vertebral. It anastomoses with the ascending pharyngeal and occipital
arteries.
The muscular branches supply the depressors of the hyoid bone, and the Longus
colli, Scalenus anterior, and Constrictor pharyngis inferior.
I
582
ANGIOLOGY
Desc. br. of
transverse cervical
Transverse scapular
Acrninial branch
■)f thoracoacromial
nterior
nneral
circumjiex
Fig. 521. — The scapular and circumflex arteries.
The Transverse Scapular Artery (a. transversa scapulcp; suprascapular artery) passes
at first downward and lateralward across the Scalenus anterior and phrenic
nerve, being covered by the
Sternocleidomastoideus ; it then
crosses the subclavian artery
and the brachial plexus, and
runs behind and parallel with
the clavicle and Subclavius,
and beneath the inferior belly
of the Omohyoideus, to the
superior border of the scapula;
it passes over the superior
transverse ligament of the
scapula which separates it from
the suprascapular nerve, and
enters the supraspinatous fossa
(Fig. 521). In this situation it
lies close to the bone, and rami-
fies between it and the Supra-
spinatus, to which it supplies
branches. It then descends be-
hind the neck of the scapula,
through the great scapular
notch and under cover of the
inferior transverse ligament, to
reach the infraspinatous fossa, where it anastomoses with the scapular circumflex
and the descending branch of the transverse cervical. Besides distributing branches
to the Sternocleidomastoideus, Subclavius, and neighboring muscles, it gives off a
suprasternal branch, which crosses over the sternal end of the clavicle to the skin of
the upper part of the chest; and an acromial branch, which pierces the Trapezius
and supplies the skin over the acromion, anastomosing with the thoracoacromial
artery. As the artery passes over the superior transverse ligament of the scapula,
it sends a branch into the subscapular fossa, where it ramifies beneath the Sub-
scapularis, and anastomoses with the subscapular artery and with the descending
branch of the transverse cervical. It also sends articular branches to the acro-
mioclavicular and shoulder-joints, and a nutrient artery to the clavicle.
The Transverse Cervical Artery (a. transversa colli; transversalis colli artery) lies
at a higher level than the transverse scapular; it passes transversely above the
inferior belly of the Omohyoideus to the anterior margin of the Trapezius, beneath
which it divides into an ascending and a descending branch. It crosses in front of
the phrenic nerve and the Scaleni, and in front of or between the divisions of the
brachial plexus, and is covered by the Platysma and Sternocleidomastoideus, and
crossed by the Omohyoideus and Trapezius.
The ascending branch {ramus ascendens; superficial cervical artery) ascends be-
neath the anterior margin of the Trapezius, distributing branches to it, and to the
neighboring muscles and lymph glands in the neck, and anastomosing with the
superficial branch of the descending ramus of the occipital artery.
The descending branch {ramus descendens; posterior scapular artery) (Fig. 521)
passes beneath the Levator scapulae to the medial angle of the scapula, and then
descends under the Rhomboidei along the vertebral border of that bone as far as
the inferior angle. It supplies the Rhomboidei, Latissimus dorsi and Trapezius,
and anastomoses with the transverse scapular and subscapular arteries, and with
the posterior branches of some of the intercostal arteries.
THE SUBCLAVIAN ARTERY
583
Peculiarities.— The ascending branch of the transverse cervical frequently arises directly
from the th>Tocervical trunk; and the descending branch from the third, more rarely from the
second, part of the subclavian.
Thyrocervical artery
Scalenus anterior
Musculophrenic artery
Common carotid artery
~ Innominate artery
Internal mammary artery
Perforating branches
Superior epigastric artery
Inferior epigastric artery
^ — External iliac artery
FiQ. 522. — ^The internal mammary artery and its branches.
3. The internal mammary artery {a. mammaria interna) (Fig. 522) arises from
the under surface of the first portion of the subclavian, opposite the thyro-
cervical trunk. It descends behind the cartilages of the upper six ribs at a distance
584 ANGIOLOGY
of about 1.25 cm. from the margin of the sternum, and at the level of the sixth
intercostal space divides into the musculophrenic and superior epigastric arteries.
Relations. — It is directed at first downward, forward, and medialward behind the sternal
end of the clavicle, the subclavian and internal jugular veins, and the first costal cartilage, and
passes forward close to the lateral side of the innominate vein. As it enters the thorax the phrenic
nerve crosses from its lateral to its medial side. Below the first costal cartilage it descends almost
vertically to its point of bifurcation. It is covered in front by the cartilages of the upper six
ribs and the intervening Intercostales interni and anterior intercostal membranes, and is crossed
by the terminal portions of the upper six intercostal nerves. It rests on the pleura, as far as the
third costal cartilage; below this level, upon the Transversus thoracis. It is accompanied by a
pair of veins; these unite above to form a single vessel, which runs medial to the artery and ends
in the corresponding innominate vein.
Branches. — The branches of the internal mammary are:
Pericardiacophrenic. Intercostal.
Anterior jNIediastinal. Perforating.
Pericardial. Musculophrenic.
Sternal. Superior Epigastric.
The Pericardiacophrenic Artery (a. pericardiacophrenica; a. comes nervi phrenici)
is a long slender branch, which accompanies the phrenic nerve, between the pleura
and pericardium, to the diaphragm, to which it is distributed; it anastomoses
with the musculophrenic and inferior phrenic arteries.
The Anterior Mediastinal Arteries (aa. mediastinales anteriores; mediastinal arter-
ies) are small vessels, distributed to the areolar tissue and lymph glands in the
anterior mediastinal cavity, and to the remains of the thymus.
The Pericardial Branches supply the upper part of the anterior surface of the
pericardium; the lower part receives branches from the musculophrenic artery.
The Sternal Branches (rami sternales) are distributed to the Transversus thoracis,
and to the posterior surface of the sternum.
The anterior mediastinal, pericardial, and sternal branches, together with some
twigs from the pericardiacophrenic, anastomose with branches from the intercostal
and bronchial arteries, and form a subpleural mediastinal plexus.
The Intercostal Branches {rami intercostales; anterior intercostal arteries) supply
the upper five or six intercostal spaces. Two in number in each space, these small
vessels pass lateralward, one lying near the lower margin of the rib above, and the
other near the upper margin of the rib below, and anastomose with the intercostal
arteries from the aorta. They are at first situated between the pleura and the
Intercostales interni, and then between the Intercostales interni and externi.
They supply the Intercostales and, by branches which perforate the Intercostales
externi, the Pectorales and the mamma.
The Perforating Branches {rami perforantes) correspond to the five or six inter-
costal spaces. They pass forward through the intercostal spaces, and, curving
lateralward, supply the Pectoralis major and the integument. Those which corre-
spond to the second, third, and fourth spaces give branches to the mamma, and
during lactation are of large size.
The Musculophrenic Artery (a. musculophrenica) is directed obliquely downward
and lateralward, behind the cartilages of the false ribs; it perforates the dia-
phragm at the eighth or ninth costal cartilage, and ends, considerably reduced
in size, opposite the last intercostal space. It gives off intercostal branches
to the seventh, eighth, and ninth intercostal spaces; these diminish in size as the
spaces decrease in length, and are distributed in a manner precisely similar to the
intercostals from the internal mammary. The musculophrenic also gives branches
to the lower part of the pericardium, and others which run backward to the dia-
phragm, and downward to the abdominal muscles.
THE AXILLA 585
The Superior Epigastric Artery (a. epigasirica superior) continues in the original
direction of the internal mammary; it descends through the interval between the
costal and sternal attachments of the diaphragm, and enters the sheath of the
Rectus abdominis, at first lying behind the muscle, and then perforating and sup-
plying it, and anastomosing with the inferior epigastric artery from the external
iliac. Branches perforate the anterior wall of the sheath of the Rectus, and supply
the muscles of the abdomen and the integument, and a small branch passes in
front of the xiphoid process and anastomoses with the artery of the opposite side.
It also gives some twigs to the diaphragm, while from the artery of the right
side small branches extend into the falciform ligament of the liver and anastomose
with the hepatic artery.
4. The costccervical trunk (truncus costocervicalis; superior intercostal artery)
(Fig. 513) arises from the upper and back part of the subclavian artery, behind
the Scalenus anterior on the right side, and medial to that muscle on the left side.
Passing backward, it gives of? the profunda cervicalis, and, continuing as the highest
intercostal artery, descends behind the pleura in front of the necks of the first and
second ribs, and anastomoses with the first aortic intercostal. As it crosses the
neck of the first rib it lies medial to the anterior division of the first thoracic nerve,
and lateral to the first thoracic ganglion of the sympathetic trunk.
In the first intercostal space, it gives oft" a branch which is distributed in a
manner similar to the distribution of tlie aortic intercostals. The branch for the
second intercostal space usually joins with one from the highest aortic intercostal
artery. This branch is not constant, but is more commonly found on the right
side; when absent, its place is supplied by an intercostal branch from the aorta.
Each intercostal gives off a posterior branch which goes to the posterior vertebral
muscles, and sends a small spinal branch through the corresponding intervertebral
foramen to the medulla spinalis and its membranes.
The Profunda Cervicalis [a. cervicalis profunda; deep cervical branch) arises, in
most cases, from the costocervical trunk, and is analogous to the posterior branch
of an aortic intercostal artery: occasionally it is a separate branch from the sub-
clavian artery. Passing backward, above the eighth cervical nerve and between
the transverse process of the seveiith cervical vertebra and the neck of the first rib,
it runs up the back of the neck, between the Semispinals capitis and colli, as high
as the axis vertebra, supplying these and adjacent muscles, and anastomosing with
the deep division of the descending branch of the occipital, and with branches of
the vertebral. It gives off a spinal twig which enters the canal through the inter-
vertebral foramen between the seventh cervical and first thoracic vertebrae.
THE AXILLA.
The axilla is a pyramidal space, situated between the upper lateral part of the
chest and the medial side of the arm.
Boundaries. — The apjex, which is directed upward toward the root of the neck,
corresponds to the interval between the outer border of the first rib, the superior
border of the scapula, and the posterior surface of the clavicle, and through it
the axillary vessels and nerves pass. The base, directed downward, is broad at
the chest but narrow and pointed at the arm; it is formed by the integument and a
thick layer of fascia, the axillary fascia, extending between the lower border of the
Pectoralis major in front, and the lower border of the Latissimus dorsi behind.
The anterior tvall is formed by the Pectorales major and minor, the former covering
the whole of this wall, the latter only its central part. The space between the upper
border of the Pectoralis minor and the clavicle is occupied by the coracoclavicular
fascia. The posterior icall, which extends somewhat lower than the anterior, is
formed by the Subscapularis above, the Teres major and Latissimus dorsi below.
586 ANGIOLOGY
On the medial side are the first four ribs with their corresponding Intercostales,
and part of the Serratus anterior. On the lateral side, where the anterior and
posterior walls converge, the space is narrow, and bounded by the humerus, the
Coracobrachialis, and the Biceps brachii.
Contents. — It contains the axillary ^•essels, and the brachial plexus of nerves,
with their branches, some branches of the intercostal nerves, and a large number
of lymph glands, together with a quantity of fat and loose areolar tissue. The
axillary artery and vein, with the brachial plexus of nerves, extend obliquely along
the lateral boundary of the axilla, from its apex to its base, and are placed much
nearer to the anterior than to the posterior wall, the vein lying to the thoracic side
of the artery and partially concealing it. At the forepart of the axilla, in contact
with the Pectorales, are the thoracic branches of the axillary artery, and along
the lower margin of the Pectoralis minor the lateral thoracic artery extends to the
side of the chest. At the back part, in contact with the lower margin of the Sub-
scapularis, are the subscapular vessels and nerves; winding around the lateral
border of this muscle are the scapular circumflex vessels; and, close to the neck
of the humerus, the posterior humeral circumflex vessels and the axillary nerve
curve backw^ard to the shoulder. Along the medial or thoracic side no vessel of
any importance exists, the upper part of the space being crossed merely by a few
small branches from the highest thoracic artery. There are some important nerves,
however, in this situation, viz., the long thoracic nerve, descending on the surface
of the Serratus anterior, to which it is distributed; and the intercostobrachial
nerve, perforating the upper and anterior part of this wall, and passing across the
axilla to the medial side of the arm.
The position and arrangement of the lymph glands are described on pages 699
and 700.
The Axillary Artery (A. Axillaris) (Fig. 523).
The axillary artery, the continuation of the subclavian, commences at the outer
border of the first rib, and ends at the lower border of the tendon of the Teres
major, where it takes the name of brachial. Its direction varies with the position
of the limb; thus the vessel is nearly straight when the arm is directed at right
angles with the trunk, concave upward when the arm is elevated above this, and
convex upward and lateralward when the arm lies by the side. At its origin the
artery is very deeply situated, but near its termination is superficial, being covered
only by the skin and fascia. To facilitate the description of the vessel it is divided
into three portions; the first part lies above, the second behind, and the third
below the Pectoralis minor.
Relations. — The first portion of the axillary artery is covered anteriorly by the clavicular
portion of the Pectorahs major and the coracoclavicular fascia, and is crossed by the lateral
anterior thoracic nerve, and the thoracoacromial and cephalic veins; posterior to it are the first
intercostal space, the corresponding Intercostalis externus, the first and second digitations of
the Serratus anterior, and the long thoracic and medial anterior thoracic nerves, and the medial
cord of the brachial plexus; on its lateral side is the brachial plexus, from which it is separated
by a little areolar tissue; on its medial, or thoracic side, is the axillary vein which overlaps the
artery. It is enclosed, together with the axillary vein and the brachial plexus, in a fibrous sheath
— the axillary sheath — continuous above with the deep cervical fascia.
The second portion of the axillary artery is covered, anteriorly, by the Pectorales major and
minor; posterior to it are the posterior cord of the brachial plexus, and some areolar tissue which
intervenes between it and the Subscapularis; on the medial side is the axillary vein, separated
from the artery by the medial cord of the brachial plexus and the medial anterior thoracic nerve;
on the lateral side is the lateral cord of the brachial plexus. The brachial plexus thus surrounds
the artery on three sides, and separates it from direct contact with the vein and adjacent muscles.
The third portion of the axillary artery extends from the lower border of the Pectorahs minor
to the lower border of the tendon of the Teres major. In front, it is covered by the lower part
of the Pectoralis major above, but only by the integument and fascia below; behind, it is in rela-
tion with the lower part of the Subscapularis, and the tendons of the Latissimus dorsi and Teres
THE AXILLARY ARTERY
587
major; on its lateral side is the Coracobraohialis, and on its medial or thoracic side, the axillary
vein. The nerves of the brachial plexus bear the following relations to this part of the artery:
on the lateral side are the lateral head and the trunk of the median, and the musculocutaneous
for a short distance; on the medial side the ulnar (between the vein and artery) and medial brachial
cutaneous (to the medial side of the vein); in front are the medial head of the median and the
medial antibrachial cutaneous, and behind, the radial and axillary, the latter only as far as the
lower border of the Subscapularis.
Collateral Circulation after Ligature of the Axillary Artery. — If the artery be tied above the
origin of the thoracoacromial, the collateral circulation will be carried on by the same branches
as after the ligature of the third part of the subclavian; if at a lower point, between the
thoracoacromial and the subscapular, the latter vessel, by its free anastomosis with the trans-
verse scapular and transverse cervical branches of the subclavian, will become the chief agent
in carrying on the circulation ; the lateral thoracic, if it be below the hgature, wiU materially contrib-
ute by its anastomoses with the intercostal and internal mammary arteries. If the point included
in the ligature is below the origin of the subscapular artery, it will most probably also be below
the origins of the two humeral circumflex arteries. The chief agents in restoring the circulation
will then be the subscapular and the two humeral circumflex arteries anastomosing with the
a. profunda brachii.
Anterior
humeral
circumflex
Fig. 523. — The axillary artery and its branches.
Branches. — The branches of the axillary are :
From first part, Highest Thoracic. From second jmrt JLj^^gj^l Thoracic!
fSubscapular.
From third part I Posterior Humeral Circumflex.
[Anterior Humeral Circumflex.
1. The highest thoracic artery (a. ihoracalis suprema; superior thoracic artery)
is a small vessel, which may arise from the thoracoacromial. Running forward
and medialward along the upper border of the Pectoralis minor, it passes between
it and the Pectoralis major to the side of the chest. It supplies branches to these
588
ANGIOLOGY
muscles, and to the parietes of the thorax, and anastomoses with the internal mam-
mary and intercostal arteries.
2. The thoracoacromial artery (a. thoracoacromialis; acromiothoracic artery; tho-
racic axis) is a short trunk, which arises from the forepart of the axillary artery,
its origin being generally overlapped by the upper edge of the Pectoralis minor
Projecting forward to the upper border of this muscle, it pierces the coracoclavicular
fascia and divides into four branches — pectoral, acromial, clavicular, and deltoid.
The pectoral branch descends between the two Pectorales, and is distributed to
them and to the mamma, anastomosing with the intercostal branches of the internal
mammary and with the lateral thoracic. The acromial branch runs lateralward
over the coracoid process and under the Deltoideus, to which it gives branches;
it then pierces that muscle and ends on the acromion in an arterial network formed
by branches from the transverse scapular, thoracoacromial, and posterior humeral
circumflex arteries. The clavicular branch runs upward and medialward to the
sternoclavicular joint, supplying this articulation, and the Subclavius. The deltoid
{humeral) branch, often arising with the acromial, crosses over the Pectoralis minor
and passes in the same groove as the cephalic vein, between the Pectoralis major
and Deltoideus, and gives branches to both muscles.
3. The lateral thoracic artery (a. thoracalis lateralis; long thoracic artery; external
mammary artery) follows the lower border of the Pectoralis minor to the side of
the chest, supplying the Serratus anterior and the Pectoralis, and sending branches
across the axilla to the axillary glands and Subscapularis; it anastomoses with the
internal mammary, subscapular, and intercostal arteries, and with the pectoral
branch of the thoracoacromial. In the female it supplies an external mammary
branch which turns round the free edge of the Pectoralis major and supplies the
mamma.
4. The subscapular artery (a. subscapularis) the largest branch of the axillary
artery, arises at the lower border of the Subscapularis, which it follows to the in-
ferior angle of the scapula, where
it anastomoses with the lateral
thoracic and intercostal arteries
and with the descending branch
of the transverse cervical, and
ends in the neighboring muscles.
About 4 cm. from its origin it
gives off a branch, the scapular
circumflex artery.
The Scapular Circumflex Artery
(a. circumfiexa scapula'; dorsalis
scapula" artery) is generally larger
than the continuation of the sub-
scapular. It curves around the
axillary border of the scapula,
traversing the space between
the Subscapularis above, the
Teres major below, and the long
head of the Triceps laterally
(Fig. 524); it enters the infra-
spinatous fossa under cover of
the Teres minor, and anasto-
moses with the transverse scap-
ular artery and the descending branch of the transverse cervical. In its course
it gives off two branches: one (infrascapular) enters the subscapular fossa beneath
the Subscapularis, which it supplies, anastomosing with the transverse scapular
Desc. br. of
transverse cervical
Transverse, scapular
Acromial branch
If tlioraco-acromial
Anterior
humeral
zircumjlex
^Termination of
subscajiular
Fig. 524. — The scapular and circumflex arteries.
THE BRACHIAL ARTERY 589
artery and the descending branch of the transverse cervical; the other is continued
along the axillary border of the scapula, between the Teres major and minor,
and at the dorsal surface of the inferior angle anastomoses with the descending
branch of the transverse cervical. In addition to these, small branches are dis-
tributed to the back part of the Deltoideus and the long head of the Triceps
brachii, anastomosing with an ascending branch of the a. profunda brachii.
5. The posterior humeral circumflex artery (a. circumflexa humeri jjosterior; pos-
terior circumflex artery) (Fig. 524) arises from the axillary artery at the lower border
of the Subscapularis, and runs backward with the axillary nerve through the quad-
rangular space bounded by the Subscapularis and Teres minor above, the Teres
major below, the long head of the Triceps brachii medially, and the surgical neck
of the humerus laterally. It winds around the neck of the humerus and is dis-
tributed to the Deltoideus and shoulder-joint, anastomosing wdth the anterior
humeral circumflex and profunda brachii.
6. The anterior humeral circumflex artery (a. circumflexa humeri ayiterior; anterior
circumflex artery) (Fig. 524), considerably smaller than the posterior, ames nearly
opposite it, from the lateral side of the axillary artery. It runs horizontally, beneath
the Coracobrachialis and short head of the Biceps brachii, in front of the neck of
the humerus. On reaching the intertubercular sulcus, it gives off a branch which
ascends in the sulcus to supply the head of the humerus and the shoulder-joint.
The trunk of the vessel is then continued onward beneath the long head of the
Biceps brachii and the Deltoideus, and anastomoses with the posterior humeral
circumflex artery.
Peculiarities. — The branches of the axillary artery vary considerably in different subjects.
Occasionally the subscapular, humeral circumflex, and profunda arteries arise from a common
trunk, and when this occurs the branches of the brachial plexus surround this trunk instead of
the main vessel. Sometimes the axillary artery divides into the radial and ulnar arteries, and
occasionally it gives origin to the volar interosseous artery of the forearm.
The Brachial Artery (A. Brachialis) (Fig. 525).
The brachial artery commences at the lower margin of the tendon of the Teres
major, and, passing down the arm, ends about 1 cm. below the bend of the elbow,
where it divides into the radial and ulnar arteries. At first the brachial arter}' lies
medial to the humerus; but as it runs down the arm it gradually gets in front of
the bone, and at the bend of the elbow it lies midway between its two epicondyles.
Relations. — The artery is superficial throughout its entire extent, being covered, in front,
by the integument and the superficial and deep fascise; the lacertus fibrosus (bicipital fascia)
lies in front of it opposite the elbow and separates it from the vena mediana cubiti; the median
nerve crosses from its lateral to its medial side opposite the insertion of the Coracobrachialis.
Behiyid, it is separated from the long head of the Triceps brachii by the radial nerve and a. pro-
funda brachii. It then lies upon the medial head of the Triceps brachii, next upon the insertion
of the Coracobrachialis, and lastly on the Brachialis. Laterally, it is in relation above with the
median nerve and the Coracobrachialis, below with the Biceps brachii, the two muscles over-
lapping the artery to a considerable extent. Medially, its upper half is in relation with the medial
antibrachial cutaneous and ulnar nerves, its lower half with the median nerve. The basihc vein
lies on its medial side, but is separated from it in the lower part of the arm by the deep fascia.
The artery is accompanied by two venae comitantes, which lie in close contact with it, and are
connected together at intervals by short transverse branches.
The Anticubital Fossa. — At the bend of the elbow the brachial artery sinks
deeply into a triangular interval, the anticubital fossa. The base of the triangle
is directed upward, and is represented by a line connecting the two epicondyles
of the humerus; the sides are formed by the medial edge of the Brachioradialis
and the lateral margin of the Pronator teres; the floor is formed by the Brachialis
and Supinator. This space contains the brachial artery, with its accompanying
veins; the radial and ulnar arteries; the median and radial nerves; and the tendon
of the Biceps brachii. The brachial artery occupies the middle of the space, and
590
ANGIOLOGY
Med. antibrach,
cut an. nerve
Radial nerve
A. profunda
brachii
divides opposite the neck of the radius into the radial and ulnar arteries ; it is covered,
in front, by the integument, the superficial fascia, and the vena mediana cubiti,
the last being separated from the artery by the lacertus fibrosus. Behind it is
the Brachialis which separates it from the elbow-joint. The median nerve lies
close to the medial side of the
artery, above, but is separated
from it below by the ulnar head of
the Pronator teres. The tendon of
the Biceps brachii lies to the lateral
side of the artery ; the radial nerve
is situated upon the Supinator, and
concealed bv the Brachioradialis.
Peculiarities of the Brachial Artery as
Regards its Course. — The brachial artery,
accompanied by the median nerve, may
leave the medial border of the Biceps
brachii, and descend toward the medial
epicondyle of the humerus; in such cases
it usually passes behind the supracondylar
process of the humerus, from which a
fibrous arch is in most cases thrown
over the artery; it then runs beneath or
through the substance of the Pronator
teres, to the bend of the elbow. This
variation bears considerable analogy with
the normal condition of the artery in
some of the carnivora; it has been re-
ferred to in the description of the hu-
merus (p. 212).
As Regards its Division. — Occasionally,
the artery is divided for a short distance
at its upper part into two trunks, which
are united below. Frequently the artery
divides at a higher level than usual, and
the vessels concerned in this high division
are three, viz., radial, ulnar, and inter-
osseous. Most frequently the radial is
given off high up, the other limb of the
bifurcation consisting of the ulnar and
interosseous; in some instances the ulnar
arises above the ordinary level, and the
radial and interosseous form the other
limb of the division; occasionally the in-
terosseous arises high up.
Sometimes, long slender vessels, vasa
aberrantia, connect the brachial or the
axillary artery with one of the arteries
of the forearm, or branches from them.
These vessels usually join the radial.
The brachial artery is occasionally concealed, in some part
Sup. ulnar collateral
artery
Inf. ulnar collateral
artery
Fig. 525. — The brachial artery
Varieties in Muscular Relations,
of its course, by muscular or tendinous shps derived from the Coracobrachialis, Biceps brachii,
Brachiahs, or Pronator teres.
Collateral Circulation.— After the apphcation of a ligature to the brachial artery in the upper
third of the arm, the circulation is carried on by branches from the humeral circumflex and sub-
scapular arteries anastomosing with ascending branches from the profunda brachii. If the
artery be tied below the origin of the profunda brachii and superior ulnar collateral, the circula-
tion is maintained by the branches of these two arteries anastomosing with the inferior ulnar
collateral, the radial and ulnar recurrents, and the dorsal interosseous.
Branches. — The branches of the brachial artery are:
Profunda Brachii. Superior Ulnar Collateral.
Nutrient.
Inferior Ulnar Collateral.
Muscular.
THE BRACHIAL ARTERY
591
1. The arteria profunda brachii {superior profunda artery) is a large vessel which
arises from the medial and back part of the brachial, just below the lower border
of the Teres major. It follows closely the radial nerve, running at first backward
between the medial and lateral heads of the Triceps brachii, then along the groove
for the radial nerve, where it is covered by the lateral head of the Triceps brachii,
to the lateral side of the arm; there it pierces the lateral intermuscular septum,
and, descending between the Brachioradialis and the Brachialis to the front of
the lateral epicondyle of the humerus, ends by anastomosing with the radial recur-
rent artery. It gives branches to the Deltoideus and to the muscles between which
it lies; it supplies an occasional nutrient artery which enters the humerus behind the
deltoid tuberosity. A branch ascends between the long and lateral heads of the
Triceps brachii to anastomose with the posterior humeral circumflex artery; a
middle collateral branch descends in the middle head of the Triceps brachii and
assists in forming the anastomosis above the olecranon ; and, lastly, a radial collateral
branch runs down behind the lateral intermuscular septum to the back of the lateral
epicondyle of the humerus, where it anastomoses with the interosseous recurrent
and the inferior ulnar collateral arteries.
2. The nutrient artery (a. nutricia humeri) of the body of the humerus arises
about the middle of the arm and enters the nutrient canal near the insertion of the
Coracobrachialis.
A. profunda brachii
Sup. ul/iar collateral
Brachial
Anterior branch of profunda
Radial collateral branch
of profunda
Radial recxirrent
Interosseous recurrent
Radial
Inf. xdnar collateral
Anterior idnar recurrent
Posterior ulnar recurrent
Interosseous
Dorsal interosseous
Ulnar
Volar interosseous
Fig. 526. — Diagram of the anastomosis around the elbow-joint.
3. The superior ulnar collateral artery (a. collateralis tdnans superior; inferior
■profunda artery), of small size, arises from the brachial a little below the middle
of the arm; it frequently springs from the upper part of the a. profunda brachii.
It pierces the medial intermuscular septum, and descends on the surface of the medial
head of the Triceps brachii to the space between the medial epicondyle and
592 ANGIOLOGY
olecranon, accompanied by the ulnar nerve, and ends under the Flexor carpi ulnaris
by anastomosing with the posterior ulnar recurrent, and inferior ulnar collateral.
It sometimes sends a branch in front of the medial epicondyle, to anastomose
with the anterior ulnar recurrent.
4. The inferior ulnar collateral artery (a. collaferalis ulnaris inferior; anastomotica
magna artery) arises about 5 cm. above the elbow. It passes medialward upon the
Brachialis, and piercing the medial intermuscular septum, winds around the back of
the humerus between the Triceps brachii and the bone, forming, by its junction with
the profunda brachii, an arch above the olecranon fossa. As the vessel lies on the
Brachialis, it gives off branches which ascend to join the superior ulnar collateral:
others descend in front of the medial epicondyle, to anastomose with the anterior
ulnar recurrent. Behind the medial epicondyle a branch anastomoses with the
superior ulnar collateral and posterior ulnar recurrent arteries.
5. The muscular branches {rami musculares) three or four in number, are dis-
tributed to the Coracobrachialis, Biceps brachii, and Brachialis.
The Anastomosis Around the Elbow-joint (Fig. 526). — The vessels engaged in
this anastomosis may be conveniently divided into those situated i7i front of and
those behind the medial and lateral epicondyles of the humerus. The branches
anastomosing in front of the medial epicondyle are: the anterior branch of the
inferior ulnar collateral, the anterior ulnar recurrent, and the anterior branch of
the superior ulnar collateral. Those behind the medial epicondyle are: the inferior
ulnar collateral, the posterior ulnar recurrent, and the posterior branch of the supe-
rior ulnar collateral. The branches anastomosing in front of the lateral epicondyle
are: the radial recurrent and the terminal part of the profunda brachii. Those
behind the lateral epicondyle (perhaps more properly described as being situated
between the lateral epicondyle and the olecranon) are: the inferior ulnar collateral,
the interosseous recurrent, and the radial collateral branch of the profunda brachii.
There is also an arch of anastomosis above the olecranon, formed by the interosseous
recurrent joining with the inferior ulnar collateral and posterior ulnar recurrent
(Fig. 529).
The Radial Artery (A. Radialis) (Fig. 527).
The radial artery appears, from its direction, to be the continuation of the brachial,
but it is smaller in caliber than the ulnar. It commences at the bifurcation of the
brachial, just below the bend of the elbow, and passes along the radial side of the
forearm to the wrist. It then Avinds backward, around the lateral side of the carpus,
beneath the tendons of the Abductor pollicis longus and Extensores pollicis longus
and brevis to the upper end of the space between the metacarpal bones of the thumb
and index finger. Finally it passes forward between the two heads of the first
Interosseous dorsalis, into the palm of the hand, where it crosses the metacarpal
bones and at the ulnar side of the hand unites with the deep volar branch of the
ulnar artery to form the deep volar arch. The radial artery therefore consists
of three portions, one in the forearm, a second at the back of the wrist, and a third
in the hand.
Relations. — (a) In the forearm the artery extends from the neck of the radius to the forepart
of the stj'Ioid process, being placed to the medial side of the body of the bone above, and in front
of it below. Its upper part is overlapped by the fleshy belly of the Brachioradiahs; the rest of
the artery is superficial, being covered by the integument and the superficial and deep fascia^.
In its course downward, it lies upon the tendon of the Biceps brachii, the Supinator, the Pronator
teres, the radial origin of the Flexor digitorum subUmis, the Flexor pollicis longus, the Pronator
quadratus, and the lower end of the radius. In the upper third of its course it lies between the
Brachioradiahs and the Pronator teres; in the lower two-thirds, between the tendons of the
Brachioradiahs and Flexor carpi radiahs. The superficial branch of the radial nerve is close to
the lateral side of the artery in the middle third of its course; and some filaments of the lateral
antibrachial cutaneous nerve run along the lower part of the artery as it winds around the wrist..
The vessel is accompanied by a pair of vense comitantes throughout its whole course.
I
THE RADIAL ARTERY
593
(h) At the wrist the artery reaches the back of the carpus by passing between the radial collateral
ligament of the wrist and the tendons of the Abductor polUcis longus and Extensor pollicis brevis.
Radial
recurrent
Radial
recurrent
Dorsal
interosseous
Muscular
Deep volar yolar radial carpal _J
branch Supetficial volar ~\
of ulnar '
Inferior ulnar
collateral
Anterior ulnar
recurrent
Posterior ulrmr
recurrent
Muscular
Volar ulnar carpal
Deep volar branch
of ulnar
Fia. 527. — The radial and ulnar arteries.
Fig. 528. — Ulnar and radial arteries. Deep view.
It then descends on the navicular and greater multangular bones, and before disappearing be-
tween the heads of the first Interosseus dorsalis is crossed by the tendon of the Extensor pollicis
38
594 ANGIOLOGY
longus. In the interval between the two Extensores pollicis it is crossed by the digital rami of
the superficial branch of the radial nerve which go to the thumb and index finger.
(c) In the hand, it passes from the upper end of the first interosseous space, between the heads
of the first Interosseus dorsahs, transversely across the palm between the Adductor pollicis
obliquus and Adductor pollicis transversus, but sometimes piercing the latter muscle, to the
base of the metacarpal bone of the little finger, where it anastomoses with the deep volar branch
from the ulnar artery, completing the deep volar arch (Fig. 528).
Peculiarities. — The origin of the radial artery is, in nearly one case in eight, higher than usual;
more often it arises from the axillary or upper part of the brachial than from the lower part of
the latter vessel. In the forearm it deviates less frequently from its normal position than the
ulnar. It has been found lying on the deep fascia instead of beneath it. It has also been observed
on the surface of the Brachioradialis," instead of under its medial border; and in turning around
the wrist, it has been seen lying on, instead of beneath, the Extensor tendons of the thumb.
Branches. — The branches of the radial artery may be divided into three groups,
corresponding with the three regions in which the vessel is situated.
In the Forearm. At the JJ^ist. In the Hand.
Radial Recurrent. Dorsal Carpal. Princeps Pollicis.
Muscular. First Dorsal Metacarpal. Volaris Indicis Radialis.
Volar Carpal. Volar ^Metacarpal.
Superficial Volar. Perforating.
Recurrent.
The radial recurrent artery {a. recvrrens radialis) arises immediately below the
elbow. It ascends between the branches of the radial nerve, lying on the Supinator
and then between the Brachioradialis and Brachialis, supplying these muscles
and the elbow-joint, and anastomosing with the terminal part of the profunda
brachii.
The muscular branches (rami musculares) are distributed to the muscles on the
radial side of the forearm.
The volar carpal branch {ramus carpeus volaris; anterior radial carpal artery)
is a small vessel which arises near the lower border of the Pronator quadratus,
and, running across the front of the carpus, anastomoses with the volar carpal
branch of the ulnar artery. This anastomosis is joined by a branch from the volar
interosseous above, and by recurrent branches from the deep volar arch below,
thus forming a volar carpal net-work which supplies the articulations of the wrist
and carpus.
The superficial volar branch (raynus volaris superficialis; supcrficialis voice artery)
arises from the radial artery, just where this vessel is about to wind around the
lateral side of the wrist. Runijing forward, it passes through, occasionally over,
the muscles of the ball of the thumb, which it supplies, and sometimes anastomoses
with the terminal portion of the ulnar artery, completing the superficial volar arch.
This vessel varies considerably in size: usually it is very small, and ends in the
muscles of the thumb; sometimes it is as large as the continuation of the radial
The dorsal carpal branch (ramus carpeus dorsalis; posterior radial carpal artery)
is a small vessel which arises beneath the Extensor tendons of the thumb ; crossing
the carpus transversely toward the medial border of the hand, it anastomoses with
the dorsal carpal branch of the ulnar and with the volar and dorsal interosseous
arteries to form a dorsal carpal network. From this network are given off three
slender dorsal metacarpal arteries, which run downward on the second, third, and
fourth Interossei dorsales and bifurcate into the dorsal digital branches for the
supply of the adjacent sides of the middle, ring, and little fingers respectively,
communicating with the proper volar digital branches of the superficial volar
arch. Near their origins they anastomose with the deep volar arch by the superior
perforating arteries, and near their points of bifurcation with the common volar
digital vessels of the superficial volar arch by the inferior perforating arteries.
THE ULNAR ARTERY 595
The first dorsal metacarpal arises just before the radial artery passes between
the two heads of the first Interosseous dorsahs and divides almost immediately
into two branches which supply the adjacent sides of the thumb and index finger;
the radial side of the thumb receives a branch directly from the radial artery.
The arteria princeps poUicis arises from the radial just as it turns mediahvard
to the deep part of the hand; it descends between the first Interosseous dorsalis and
Adductor pollicis obliquus, along the ulnar side of the metacarpal bone of the
thumb to the base of the first phalanx, where it lies beneath the tendon of the
Flexor pollicis longus and divides into two branches. These make their appear-
ance between the medial and lateral insertions of the Adductor pollicis obliquus,
and run along the sides of the thumb, forming on the volar surface of the last
phalanx an arch, from which branches are distributed to the integument and
subcutaneous tissue of the thumb.
The arteria volaris indicis radialis {radialis indicis artery) arises close to the pre-
ceding, descends between the first Interosseus dorsalis and Adductor pollicis trans-
versus, and runs along the radial side of the index finger to its extremity, where it
anastomoses with the proper digital artery, supplying the ulnar side of the finger. At
the lower border of the Adductor pollicis transversus this vessel anastomoses with
the princeps pollicis, and gives a communicating branch to the superficial volar arch.
The a. princeps pollicis and a. volaris indicis radialis may spring from a common
trunk termed the first volar metacarpal artery.
The deep volar arch (arcus volaris profundus; deep palmar arch) (Fig. 528) is
formed by the anastomosis of the terminal part of the radial artery with the deep
volar branch of the ulnar. It lies upon the carpal extremities of the metacarpal
bones and on the Interossei, being covered by the Adductor pollicis obliquus, the
Flexor tendons of the fingers, and the Lumbricales. Alongside of it, but running
in the opposite direction — that is to say, toward the radial side of the hand- — is
the deep branch of the ulnar nerve.
The volar metacarpal arteries (aa. metacarpeoe volares; palmar interosseous
arteries), three or four in number, arise from the convexity of the deep volar arch;
they run distally upon the Interossei, and anastomose at the clefts of the fingers
with the common digital branches of the superficial volar arch.
The perforating branches {ravii perforantes) , three in number, pass backward
from the deep volar arch, through the second, third, and fourth interosseous spaces
and between the heads of the corresponding Interossei dorsalis, to anastomose
with the dorsal metacarpal arteries.
The recurrent branches arise from the concavity of the deep volar arch. They
ascend in front of the wrist, supply the intercarpal articulations, and end in the
volar carpal network.
The Ulnar Artery (A. Ulnaris) (Fig. 528).
The ulnar artery, the larger of the two terminal branches of the brachial, begins
a little below the bend of the elbow, and, passing obliquely downward, reaches
the ulnar side of the forearm at a point about midway between the elbow and the
wrist. It then runs along the ulnar border to the wrist, crosses the transverse
carpal ligament on the radial side of the pisiform bone, and immediately beyond
this bone divides into two branches, which enter into the formation of the superficial
and deep volar arches.
Relations. — (a) In the forearm.— In its upper half, it is deeply seated, being covered by the
Pronator teres, Flexor carpi radialis, Palmaris longus, and Flexor digitorum sublimis; it lies
upon the Brachialis and Flexor digitorum profundus. The median nerve is in relation with the
medial side of the artery for about 2.5 cm. and then crosses the vessel, being separated from it
by the ulnar head of the Pronator teres. In the lower half of the forearm it hes upon the Flexor
digitorum profundus, being covered by the integument and the superficial and deep fasciae.
In the Forearm
596 ANGIOLOGY
and placed between the Flexor carpi ulnaris and Flexor digitorum subUmis. It is accompanied
by two venaj comitantes, and is overlapped in its middle third by the Flexor carpi ulnaris; the
ulnar nerve lies on the medial side of the lower two-thirds of the artery, and the palmar cutaneous
branch of the nerve descends on the lower part of the vessel to the palm of the hand.
(6) At the wrist (Fig. 527) the ulnar arterj' is covered by the integument and the volar carpal
ligament, and Ues upon the transverse carpal hgament. On its medial side is the pisiform bone,
and, somewhat behind the arterj', the ulnar nerve.
Peculiarities. — The ulnar artery varies in its origin in the proportion of about one in thirteen
cases; it may arise about 5 to 7 cm. below the elbow, but more frequently higher, the brachial
being more often the soiu-ce of origin than the axillary-. Variations in the position of this vessel
are more common than in the radial. When its origin is normal, the course of the vessel is rarelj'
changed. ^Tien it arises high up, it is almost invariably superficial to the Flexor muscles in the
forearm, lying commonly beneath the fascia, more rarely between the fascia and integument.
In a few cases, its position was subcutaneous in the upper part of the forearm, and subaponeurotic
in the lower part.
Branches. — The branches of the ulnar artery may be arranged in the following
groups :
Anterior Recurrent. At th W ' f ^ ^ ol^r Carpal.
Posterior Recurrent. \ Dorsal Carpal.
Common Interosseous, t ., u ■, i Deep Volar.
^r 1 -''^ "'^ Hand < ^ c • i ^^ i \ u
Muscular. ( Superhcial \ olar Arch.
The anterior ulnar recurrent artery (a. recurrentes vJnaris anterior) arises imme-
diately below the elbow-joint, runs upward between the Brachialis and Pronator
teres, supplies twigs to those muscles, and, in front of the medial epicondyle, anasto-
moses with the superior and inferior ulnar collateral arteries.
The posterior ulnar recurrent artery (a. recurrentes ulnaris posterior) is much
larger, and arises somewhat lower than the preceding. It passes backward and
medialward on the Flexor digitorum profundus, behind the Flexor digitorum sub-
limis, and ascends behind the medial epicondyle of the humerus. In the interval
between this process and the olecranon, it lies beneath the Flexor carpi ulnaris,
and ascending between the heads of that muscle, in relation with the ulnar nerve,
it supplies the neighboring muscles and the elbow-joint, and anastomoses with
the superior and inferior ulnar collateral and the interosseous recurrent arteries
(Fig. 529).
The coimnon interosseous artery {a. intcrossea communis) (Fig. 528), about 1 cm.
in length, arises immediately below the tuberosity of the radius, and, passing
backward to the upper border of the interosseous membrane, divides into two
branches, the volar and dorsal interosseous arteries.
The Volar Interosseous Artery (a. interossea rolaris; anterior interosseous artery)
(Fig. 528), passes down the forearm on the volar surface of the interosseous mem-
brane. It is accompanied by the volar interosseous branch of the median nerve,
and overlapped by the contiguous margins of the Flexor digitorum profundus and
Flexor poUicis longus, giving off in this situation muscular branches, and the nutrient
arteries of the radius and ulna. At the upper border of the Pronator quadratus it
pierces the interosseous membrane and reaches the back of the forearm, where it
anastomoses with the dorsal interosseous artery (Fig. 529). It then descends, in
company with the terminal portion of the dorsal interosseous nerve, to the back
of the wrist to join the dorsal carpal net-work. The volar interosseous artery gives
oflF a slender branch, the arteria mediana, which accompanies the median nerve, and
gives offsets to its substance; this artery is sometimes much enlarged, and runs
with the nerve into the palm of the hand. Before it pierces the interosseous
membrane the volar interosseous sends a branch downward behind the Pronator
quadratus to join the volar carpal network.
The Dorsal Interosseous Artery {a. interossea dorsalis; posterior interosseous artery)
(Fig. 529) passes backward between the oblique cord and the upper border of the
interosseous membrane. It appears between the contiguous borders of the Supinator
THE ULNAR ARTERY
597
and the Abductor poUicis longus, and runs down the back of the forearm between
the superficial and deep layers of muscles, to both of which it distributes branches.
Where it lies upon the Abductor pollicis longus and the Extensor pollicis brevis,
Inf. ulnar collateral
Posterior vlnar recurrent —
A. profunda brachii
Dorsal interosseous
Dorsal ulnar carpal
■Termination of volar
interosseous
Dorsal radial carpal
Radial
\ l.it dorsal
f metacarpal
Fig. 529. — Arteries of the back of the forearm and hand.
it is accompanied by the dorsal interosseous nerve. At the lower part of the fore-
arm it anastomoses with the termination of the volar interosseous artery, and with
the dorsal carpal network. It gives off, near its origin, the interosseous recurrent
artery, which ascends to the interval between the lateral epicondyle and olecranon,
598 ANGIOLOGY
on or through the fibers of the Supinator, but beneath the Anconteus, and anasto-
moses with the radial collateral l)ranch of the profunda brachii, the posterior
ulnar recurrent and the inferior ulnar collateral.
The muscular branches {rami musculares) are distributed to the muscles along
the ulnar side of the forearm.
The volar carpal branch (ramus carpeus volares; anterior ulnar carpal artery) is a
small vessel which crosses the front of the carpus beneath the tendons of the Flexor
digitorum profundus, and anastomoses with the corresponding branch of the radial
artery.
The dorsal carpal branch {ramus carpeus dorsalis; posterior ulnar carpal artery)
arises immediately above the pisiform bone, and winds backward beneath the
tendon of the Flexor carpi ulnaris; it passes across the dorsal surface of the carpus
beneath the Extensor tendons, to anastomose with a corresponding branch of the
radial artery. Immediately after its origin, it gives off a small branch, which runs
along the ulnar side of the fifth metacarpal bone, and supplies the ulnar side of the
dorsal surface of the little finger.
The deep volar branch {ramus volaris profundus; profunda branch) (Fig. 528)
passes between the Abductor digiti quinti and Flexor digiti quinti brevis and
through the origin of the Opponens digiti quinti; it anastomoses with the radial
artery, and completes the deep volar arch.
The superficial volar arch {arcus volaris superficialis; superficial palmar arch)
(Fig. 527) is formed by the ulnar artery, and is usually completed by a branch
from the. a. volaris indicis radialis, but sometimes by the superficial volar or by
a branch from the a. princeps pollicis of the radial artery. The arch passes across
the palm, describing a curve, with its convexity downward.
Relations. — The superficial volar arch is covered by the skin, the Palmaris brevis, and the
palmar aponeurosis. It lies upon the transverse carpal ligament, the Flexor digiti quinti brevis
and Opponens digiti quinti, the tendons of the Flexor digitorum sublimis, the Lumbrjcales, and
the divisions of the median and ulnar nerves.
Three Common Volar Digital Arteries {aa. digitales volares communes; palmar digital
arteries) (Fig. 527) arise from the convexity of the arch and proceed downward
on the second, third, and fourth Lumbricales. Each receives the corresponding
volar metacarpal artery and then divides into a pair of proper volar digital arteries
{aa. digitales volares propriw; collateral digital arteries) which run along the con-
tiguous sides of the index, middle, ring, and little fingers, behind the corresponding
digital nerves; they anastomose freely in the subcutaneous tissue of the finger tips
and by smaller branches near the interphalangeal joints. Each gives off a couple
of dorsal branches which anastomose with the dorsal digital arteries, and supply
the soft parts on the back of the second and third phalanges, including the matrix
of the finger-nail. The proper volar digital artery for medial side of the little
finger springs from the ulnar artery under cover of the Palmaris brevis.
THE ARTERIES OF THE TRUNK.
THE DESCENDING AORTA.
The descending aorta is divided into two portions, the thoracic and abdominal,
in correspondence with the two great cavities of the trunk in which it is situated-
The Thoracic Aorta (Aorta Thoracalis) (Fig. 530).
The thoracic aorta is contained in the posterior mediastinal cavity. It begins
at the lower border of the fourth thoracic vertebra where it is continuous with
the aortic arch, and ends in front of the lower border of the twelfth at the aortic
THE THORACIC AORTA
599
hiatus in the diaphragm. At its commencement, it is situated on the left of the
vertebral column; it approaches the median line as it descends; and, at its termina-
tion, lies directly in front of the column. The vessel describes a curve which is
concave forward, and as the branches given off from it are small, its diminution
in size is inconsiderable.
Highest intercostal artery
Highest intercostal vein
/
Rami communicantes
Lig. arteriosum
Fig. 530. — The thoracic aorta, viewed from the left side.
Relations. — It is in relation, anteriorly, from above downward, with the root of the left lung,
the pericardium, the esophagus, and the diaphragm; posteriorly, with the vertebral column
and the hemiazygos veins; on the right side, with the azygos vein and thoracic duct; on the lejt
side, with the left pleura and lung. The esophagus, with its accompanying plexus of nerves,
lies on the right side of the aorta above ; but at the lower part of the thorax it is placed in front
of the aorta, and, close to the diaphragm, is situated on its left side.
Peculiarities. — The aorta is occasionally found to be obUterated at the junction of the arch
with the thoracic aorta, just below the ductus arteriosus. Whether this is the result of disease,
or of congenital malformation, is immaterial to our present purpose; it affords an interesting
opportunity of observing the resources of the collateral circulation. The course of the anastomos-
600 ANGIOLOGY
ing vessels, by which the blood is brought from the upper to the lower part of the artery, will be
found well described in an account of two cases in the Pathological Transactions, vols, viii and x.
In the former, Sydney Jones thus sums up the detailed description of the anastomosing vessels:
The principal communications by which the circulation was carried on were; (1) The internal
mammary, anastomosing with the intercostal arteries, with the inferior phrenic of the abdominal
aorta by means of the musculophrenic and pericardiacophrenic, and largely with the inferior
epigastric. (2) The costocervical trunk, anastomosing anteriorly by means of a large branch
with the first aortic intercostal, and posteriorly with the posterior branch of the same artery.
(3) The inferior thyroid, by means of a branch about the size of an ordinary radial, forming a
communication with the first aortic intercostal. (4) The transverse cervical, by means of very
large communications with the posterior branches of the intercostals. (5) The branches (of
the subclavian and axillary) going to the side of the chest were large, and anastomosed freely
with the lateral branches of the intercostals. In the second case Wood describes the anastomoses
in a somewhat similar manner, adding the remark that "the blood which was brought into the
aorta through the anastomosis of the intercostal arteries appeared to be expended principally
in supplying the abdomen and pelvis ; while the supply to the lower extremities had passed through
the internal mammary and epigastrics."
In a few cases an apparently double descending thoracic aorta has been found, the two vessels
lying side by side, and eventually fusing to form a single tube in the lower part of the thorax or
in the abdomen. One of them is the aorta, the other represents a dissecting aortic aneurism
which has become canalized; opening above and below into the true aorta, and at first sight
presenting the appearances of a proper bloodvessel.
Branches of the Thoracic Aorta.—
Visceral
Pericardial. ( Intercostal.
Bronchial. Parietal ■( Subcostal.
Esophageal. ( Superior Phrenic.
Mediastinal.
\
The pericardial branches (rami pericardiaci) consist of a few small vessels which
are distributed to the posterior surface of the pericardium.
The bronchial arteries (aa. hronchiales) vary in number, size, and origin. There
is as a rule only one right bronchial artery, which arises from the first aortic inter-
costal, or from the upper left bronchial artery. The left bronchial arteries are usually
two in number, and arise from the thoracic aorta. The upper left bronchial arises
opposite the fifth thoracic vertebra, the lower just below the level of the left bron-
chus. Each vessel runs on the back part of its bronchus, dividing and subdividing
along the bronchial tubes, suj)pl;sing them, the areolar tissue of the lungs, the
bronchial l^^nph glands, and the esophagus.
The esophageal arteries {aa. oesophagece) four or five in number, arise from
the front of the aorta, and pass obliquely downward to the esophagus, forming
a chain of anastomoses along that tube, anastomosing with the esophageal branches
of the inferior thyroid arteries above, and with ascending branches from the left
inferior phrenic and left gastric arteries below.
The mediastinal branches {rami viediastinales) are numerous small vessels which
supply the lymph glands and loose areolar tissue in the posterior mediastinum.
Intercostal Arteries {aa. intercostal es). — There are usually nine pairs of aortic
intercostal arteries. They arise from the back of the aorta, and a redistributed
to the lower nine intercostal spaces, the first two spaces being supplied by the highest
intercostal arterv, a branch of the costocervical trunk of the subclavian. The
right aortic intercostals are longer than the left, on account of the position of the
aorta on the left side of the vertebral column; they pass across the bodies of the
vertebrse behind the esophagus, thoracic duct, and vena azygos, and are covered
by the right lung and pleura. The left aortic intercostals run backward on the
sides of the vertebrae and are covered by the left lung and pleura; the upper two
vessels are crossed by the highest left intercostal vein, the low^er. vessels by the
hemiazygos veins. The further course of the intercostal arteries is practically
the same on both sides. Opposite the heads of the ribs the sympathetic trunk
THE THORACIC AORTA 601
passes downward in front of them, and the splanchnic nerves also descend in front
by the lower arteries. Each artery then divides into an anterior and a posterior
ramus.
The Anterior Ramus crosses the corresponding intercostal space obliquely toward
the angle of the upper rib, and thence is continued forward in the costal groove. It
is placed at first between the pleura and the posterior intercostal membrane, then
it pierces this membrane, and lies between it and the Intercostalis externus as far as
the angle of the rib; from this onward it runs between the Intercostales externus
and internus, and anastomoses in front with the intercostal branch of the internal
mammary or musculophrenic. Each artery is accompanied by a vein and a nerve,
the former being above and the latter below the artery, except in the upper spaces,
where the nerve is at first above the artery. The first aortic intercostal artery
anastomoses with the intercostal branch of the costocervical trunk, and may form
the chief supply of the second intercostal space. The lower two intercostal arteries
are continued anteriorly from the intercostal spaces into the abdominal wall, and
anastomose with the subcostal, superior epigastric, and lumbar arteries.
Branches. — The anterior rami give off the following branches:
Collateral Intercostal. Lateral Cutaneous.
Muscular. Mammary.
The collateral intercostal branch comes off from the intercostal artery near the
angle of the rib, and descends to the upper border of the rib below, along which it
courses to anastomose with the intercostal branch of the internal mammary.
Muscular branches are given to the Intercostales and Pectorales and to the
Serratus anterior; they anastomose with the highest and lateral thoracic branches
of the axillary artery.
The lateral cutaneous branches accompany the lateral cutaneous branches of the
thoracic nerves.
Mammary branches are given off by the vessels in the third, fourth, and fifth
spaces. They supply the mamma, and increase considerably in size during the
period of lactation.
The Posterior Ramus runs backward through a space which is bounded above
and below by the necks of the ribs, medially by the body of a vertebra, and laterally
by an anterior costotransverse ligament. It gives off a spinal branch which enters
the vertebral canal through the intervertebral foramen and is distributed to the
medulla spinalis and its membranes and the vertebrae. It then courses over
the transverse process with the posterior division of the thoracic nerye, supplies
branches to the muscles of the back and cutaneous branches which accompany
the corresponding cutaneous branches of the posterior division of the nerve.
The subcostal arteries, so named because they lie below the last ribs, constitute
the lowest pair of branches derived from the thoracic aorta, and are in series with
the intercostal arteries. Each passes along the lower border of the twelfth rib
behind the kidney and in front of the Quadratus lumborum muscle, and is accom-
panied by the twelfth thoracic nerve. It then pierces the posterior aponeurosis
of the Transversus abdominis, and, passing forward between this muscle and the
Obliquus internus, anastomoses with the superior epigastric, lower intercostal, and
lumbar arteries. Each subcostal artery gives off a posterior branch which has a
similar distribution to the posterior ramus of an intercostal artery.
The superior phrenic branches are small and arise from the lower part of the
thoracic aorta; they are distributed to the posterior part of the upper surface of
the diaphragm, and anastomose with the musculophrenic and pericardiacophrenic
arteries.
A small aberrant artery is sometimes found arising from the right side of the tho-
racic aorta near the origin of the right bronchial. It passes upward and to the right
602
ANGIOLOGY
behind the trachea and the esophagus, and may anastomose with the highest
right intercostal artery. It represents the remains of the right dorsal aorta, and in a
small proportion of cases is enlarged to form the first part of the right subclavian
artery.
The Abdominal Aorta Aorta AbdominaUs') (Fig. 531).
The abdominal aorta begins at the aortic hiatus of the diaphragm, in front
of the lower border of the body of the last thoracic vertebra, and, descending in
P \A_PjH_R_A_GjVf
Inferior pltnnic arteries
Internal
spermatic
vessels
Fig. 531. — The abdominal aorta and its branches.
front of the vertebral column, ends on the body of the fourth lumbar vertebra,
commonlv a little to the left of the middle line,^ bv dividing into the two common
iliac arteries. It diminishes rapidly in size, in consequence of the many large
branches which it gives off. As it lies upon the bodies of the vertebrae, the curve
which it describes is convex forward, the summit of the convexity corresponding
to the third lumbar vertebra.
1 Lord Lister, having accurately examined 30 bodies in order to ascertain the exact point of termination of this
vessel, found it "either absolutely, or almost absolutely, mesial in 15, while in 13 it de'viated more or less to the left,
and in 2 was slightly to the right. " System of Surgerj-, edited by T. Holmes, 2d ed., v, 652.
THE ABDOMINAL AORTA 603
Relations. — The abdominal aorta is covered, anteriorly, by the lesser omentum and stomach,
behind which are tlie branches of the ceUac artery and the celiac plexus; below these, by the
lienal vein, the pancreas, the left renal vein, the inferior part of the duodenum, the mesentery,
and aortic plexus. Posteriorly, it is separated from the lumbar vertebra; and intervertebral
fibrocartilages by the anterior longitudinal Hgament and left lumbar veins. On the right side
it is in relation above with the azygos vein, cisterna chyli, thoracic duct, and the right crus of
the diaphragm — the last separating it from the upper part of the inferior vena cava, and from
the right cehac ganglion; the inferior vena cava is in contact with the aorta below. On the
left side are the left crus of the diaphragm, the left celiac ganghon, the ascending part of the
duodenum, and some coils of the small intestine.
Collateral Circulation. — The collateral circulation would be carried on by the anastomoses
between the internal mammary and the inferior epigastric; by the free communication between
the superior and inferior mesenteries, if the hgature were placed between these vessels; or by the
anastomosis between the inferior mesenteric and the internal pudendal, when (as is more common)
the point of ligature is below the origin of the inferior mesenteric; and possibly by the anastomoses
of the lumbar arteries with the branches of the hypogastric.
Branches. — The branches of the abdominal aorta may be divided into three
sets: visceral, parietal, and terminal.
Visceral Branches. Parietal Branches.
Celiac. Inferior Phrenics.
Superior ^Mesenteric. Lumbars.
Inferior ^Mesenteric. ^Middle Sacral.
Middle Suprarenals.
Renals.
Internal Spermatics. Terminal Branches.
Ovarian (in the female). Common Iliacs.
Of the visceral branches, the celiac artery and the superior and inferior mes-
enteric arteries are unpaired, while the suprarenals, renals, internal spermatics,
and ovarian are paired. Of the parietal branches the inferior phrenics and lumbars
are paired; the middle sacral is unpaired. The terminal branches are paired.
The celiac artery (a. cwliaca; celiac axis) (Figs. 532, 533) is a short thick trunk,
about 1.25 cm. in length, which arises from the front of the aorta, just below
the aortic hiatus of the diaphragm, and, passing nearly horizontally forward,
divides into three large branches, the left gastric, the hepatic, and the splenic; it
occasionally gives off one of the inferior phrenic arteries.
Relations. — The cehac artery is covered by the lesser omentum. On the right side it is in
relation with the right cehac ganghon and the caudate process of the liver; on the left side, with
the left cehac ganghon and the cardiac end of the stomach. Below, it is in relation to the upper
border of the pancreas, and the Uenal vein.
1. The Left Gastric Artery (a. gastrica sinistra; gastric or coronary artery), the
smallest of the three branches of the celiac artery, passes upward and to the left,
posterior to the omental bursa, to the cardiac orifice of the stomach. Here it dis-
tributes branches to the esophagus, which anastomose with the aortic esophageal
arteries; others supply the cardiac part of the stomach, anastomosing with branches
of the lienal artery. It then runs from left to right, along the lesser curvature of the
stomach to the pylorus, between the layers of the lesser omentum ; it gives branches
to both surfaces of the stomach and anastomoses with the right gastric artery.
2. The Hepatic Artery (a. hepatica) in the adult is intermediate in size between
the left gastric and lienal; in the fetus, it is the largest of the three branches of
the celiac artery. It is first directed forward and to the right, to the upper margin
of the superior part of the duodenum, forming the lower boundary of the epiploic
foramen {foramen of Winslow). It then crosses the portal vein anteriorly and
ascends between the layers of the lesser omentum, and in front of the epiploic fora-
men, to the porta hepatis, where it divides into two branches, right and left, which
supply the corresponding lobes of the liver, accompanying the ramifications of the
604
ANGIOLOGY
portal vein and hepatic ducts. The hepatic artery, in its course along the right
border of the lesser omentum, is in relation with the common bile-duct and portal
vein, the duct lying to the right of the artery, and the vein behind.
Its branches are:
Right Gastric.
Gastroduodenal l^^-^^^G-'^^^^^^P^P'^^^:, ^ ,
[ buperior rancreaticoduodenal.
Cvstic.
Cystic artery
o
re
Fig. 532. — The celiac arterj' and its branches; the liver has been raised, and the lesser omentum and anterior
layer of the greater omentum removed.
The right gastric artery (a. gasirica dextra; pyloric artery) arises from the hepatic,
above the pylorus, descends to the pyloric end of the stomach, and passes from
right to left along its lesser curvature, supplying it with branches, and anastomosing
with the left gastric artery.
The gastroduodenal artery {a. gasiroduodenalis) (Fig. 533) is a short but large
branch, which descends, near the pylorus, between the superior part of the duo-
denum and the neck of the pancreas, and divides at the lower border of the duodenum
into two branches, the right gastroepiploic and the superior pancreaticoduodenal.
Previous to its division it gives off two or three small branches to the pyloric end
of the stomach and to the pancreas.
The right gastroepiploic artery (a. gastroepiploica dextra) runs from right to left
along the greater curvature of the stomach, between the layers of the greater
omentum, anastomosing with the left gastroepiploic branch of the lienal artery.
Except at the pylorus, where it is in contact with the stomach, it lies about a finger's
THE ABDOMINAL AORTA
605
breadth from the greater curvature. This vessel gives off numerous branches,
some of which ascend to supply both surfaces of the stomach, while others descend
to supply the greater omentum and anastomose with branches of the middle colic.
The superior pancreaticoduodenal artery (a. pancreaticoduodenalis superior)
descends between the contiguous margins of the duodenum and pancreas. It
supplies both these organs, and anastomoses with the inferior pancreaticoduodenal
branch of the superior mesenteric artery, and with the pancreatic branches of the
lienal artery.
Branches to greater amentum
Fig 533. — The celiac arterj' and its branches; the stomach has been raised and the peritoneum removed.
The cystic artery (a. cystica) (Fig. 532), usually a branch of the right hepatic,
passes downward and forward along the neck of the gall-bladder, and divides into
two branches, one ot which ramifies on the free surface, the other on the attached
surface of the gall-bladder.
3. The Lienal or Splenic Artery (a. lienalis), the largest branch of the celiac
artery, is remarkable fof the tortuosity of its course. It passes horizontally to
the left side, behind the stomach and the omental bursa of the peritoneum, and
along the upper border of the pancreas, accompanied by the lienal vein, which
lies below it; it crosses in front of the upper* part of the left kidney, and, on arriving
near the spleen, divides into branches, some of which enter the hilus of that organ
between the two layers of the phrenicolienal ligament to be distributed to the tissues
of the spleen; some are given to the pancreas, while others pass to the greater curva-
ture of the stomach between the layers of the gastrolienal ligament. Its branches are :
Pancreatic.
Short Gastric.
Left Gastroepiploic.
606
ANGIOLOGY
The pancreatic branches (rami pancreatici) are numerous small vessels derived
from the lienal as it runs behind the upper border of the pancreas, supplying its
body and tail. One of these, larger than the rest, is sometimes given off near the
tail of the pancreas; it runs from left to right near the posterior surface of the gland,
following the course of the pancreatic duct, and is called the arteria pancreatica
magna. These vessels anastomose with the pancreatic branches of the pancreatico-
duodenal and superior mesenteric arteries.
Fig. 534. — The superior mesenteric artery and its branches.
The short gastric arteries {aa. gastricop breves; vasa brevia) consist of from five to
«even small branches, which arise from the end of the lienal artery, and from its
terminal divisions. They pass from left to right, between the layers of the gastro-
lienal ligament, and are distributed to the greater curvature of the stomach, anasto-
mosing with branches of the left gastric and left gastroepiploic arteries.
The left gastroepiploic artery (a. gastroepiploica sinistra) the largest branch of the
lienal, runs from left to right about a finger's breadth or more from the greater
curvature of the stomach, between the layers of the greater omentum, and anasto-
moses with the right gastroepiploic. In its course it distributes several ascending
branches to both surfaces of the stomach; others descend to supply the greater
omentum and anastomose with branches of the middle colic.
The superior mesenteric ariiery (a. viesenterica superior) (Fig. 534) is a large
THE ABDOMINAL AORTA 607
vessel which suppHes the whole length of the small intestine, except the superior
part of the duodenum; it also supplies the cecum and the ascending part of the colon
and about one-half of the transverse part of the colon. It arises from the front
of the aorta, about 1.25 cm. below the celiac artery, and is crossed at its origin by
the lienal vein and the neck of the pancreas. It passes downward and forward,
anterior to the processus uncinatus of the head of the pancreas and inferior part
of the duodenum, and descends between the layers of the mesentery to the right
iliac fossa, where, considerably diminished in size, it anastomoses with one of
its own branches, viz., the ileocolic. In its course it crosses in front of the inferior
vena cava, the right ureter and Psoas major, and forms an arch, the convexity of
which is directed forward and downward to the left side, the concavity backward
and upward to the right. It is accompanied by the superior mesenteric vein,
which lies to its right side, and it is surrounded by the superior mesenteric plexus
of nerves.
Branches. — Its branches are:
Inferior Pancreaticoduodenal. Ileocolic.
Intestinal. Right Colic.
Middle Colic.
The Inferior Pancreaticoduodenal Artery (a. ixmcreaticoduodenalis inferior) is given
off from the superior mesenteric or from its first intestinal branch, opposite the
upper border of the inferior part of the duodenum. It courses to the right
between the head of the pancreas and duodenum, and then ascends to anastomose
with the superior pancreaticoduodenal artery. It distributes branches to the head
of the pancreas and to the descending and inferior parts of the duodenum.
The Intestinal Arteries {aa. intestinales ; rasa intestini tenuis) arise from the convex
side of the superior mesenteric artery. They are usually from twelve to fifteen
in number, and are distributed to the jejunum and ileum. They run nearly parallel
with one another between the layers of the mesentery, each vessel dividing into
two branches, which unite with adjacent branches, forming a series of arches, the
convexities of which are directed toward the intestine (Fig. 535). From this first
set of arches branches arise, which unite with similar branches from above and below
and thus a second series of arches is formed; from the lower branches of the artery,
a third, a fourth, or even a fifth series of arches may be formed, diminishing in
size the nearer they approach the intestine. In the short, upper part of the mesen-
tery only one set of arches exists, but as the depth of the mesentery increases,
second, third, fourth, or even fifth groups are developed. From the terminal
arches numerous small straight vessels arise which encircle the intestine, upon
which they are distributed, ramifying between its coats. From the intestinal
arteries small branches are given oft' to the lymph glands and other structures
between the layers of the mesentery.
The Ileocolic Artery (a. ileocolica) is the low'est branch arising from the concavity
of the superior mesenteric artery. It passes downward and to the right behind the
peritoneum toward the right iliac fossa, where it divides into a superior and an
inferior branch; the inferior anastomoses with the end of the superior mesenteric
artery, the superior with the right colic artery.
The inferior branch of the ileocolic runs toward the upper border of the ileo-
colic junction and supplies the following branches (Fig. 536) :
(a) eolic, which pass upward on the ascending colon; (6) anterior and posterior
cecal, which are distributed to the front and back of the cecum; (c) an appendicular
artery, which descends behind the termination of the ileum and enters the mesen-
teriole of the vermiform process; it runs near the free margin of this mesenteriole
and ends in branches which supply the vermiform process; and (d) ileal, which run
upward and to the left on the lower part of the ileum, and anastomose with the
termination of the superior mesenteric.
608
ANGIOLOGY
Fig. 535. — Loop of small intestine showing distribution of intestinal arteries. (From a preparation by Mr. Hamilton
Drummond.) The vessels were injected while the gut was in silu; the gut was then removed, and an i-ray photograph
taken.
Terminal part of ileocolic
Cecal branches
Ileal hranches
Appendictdar
artery
'^■^oj'm process
Fig. 536. — Arteries of cecum and vermiform process.
THE ABDOMINAL AORTA
609
The Right Colic Artery (a. colica dextra) arises from about the middle of the con-
cavity of the superior mesenteric artery, or from a stem common to it and the ileo-
cohc. It passes to the right behind the peritoneum, and in front of the right
internal spermatic or ovarian vessels, the right ureter and the Psoas major, toward
the middle of the ascending colon; sometimes the vessel lies at a higher level,
and crosses the descending part of the duodenum and the lower end of the right
kidney. At the colon it divides into a descending branch, which anastomoses with
the ileocolic, and an ascending branch, which anastomoses with the middle colic.
These branches form arches, from the convexity of which vessels are distributed
to the ascending colon.
Middle Hemorrhoidal
Inferior Hemorrhoidal
Fig. 537. — The inferior mesenteric artery and its branches.
The Middle Colic Artery (a. colica media) arises from the superior mesenteric
just below the pancreas and, passing downward and forward between the layers of
the transverse mesocolon, divides into two branches, right and left; the former
anastomoses with the right colic; the latter with the left colic, a branch of the in-
ferior mesenteric. The arches thus formed are placed about two fingers' breadth
from the transverse colon, to which thev distribute branches.
The inferior mesenteric artery (a. mesenterica inferior) (Fig. 537) supplies the
left half of the transverse part of the colon, the whole of the descending and iliac
parts of the colon, the sigmoid colon, and the greater part of the rectum. It is
smaller than the superior mesenteric, and arises from the aorta, about 3 or 4 cm.
39
610 ANGIOLOGY
above its division into the common iliacs and close to the lower border of the
inferior part of the duodenum. It passes downward posterior to the peritoneum,
lying at first anterior to and then on the left side of the aorta. It crosses the
left common iliac artery and is continued into the lesser pelvis under the name of
the superior hemorrhoidal artery, which descends between the two layers of the
sigmoid mesocolon and ends on the upper part of the rectum.
Branches. — Its branches are:
Left Colic. Sigmoid. Superior Hemorrhoidal.
The Left Colic Artery (a. colica sinistra) runs to the left behind the peritoneum
and in front of the Psoas major, and after a short, but variable, course divides
into an ascending and a descending branch; the stem of the artery or its branches
cross the left ureter and left internal spermatic vessels. The ascending branch
crosses in front of the left kidney and ends, between the two layers of the transverse
mesocolon, by anastomosing with the middle colic artery; the descending branch
anastomoses with the highest sigmoid artery. From the arches formed by these
anastomoses branches are distributed to the descending colon and the left part
of the transverse colon.
The Sigmoid Arteries (aa. sigmoidecp) (Fig. 538), two or three in number, run
obliquely downward and to the left behind the peritoneum and in front of the
Psoas major, ureter, and internal spermatic vessels. Their branches supply the lower
part of the descending colon, the iliac colon, and the sigmoid or pelvic colon ; anasto-
mosing above with the left colic, and below with the superior hemorrhoidal artery.
The Superior Hemorrhoidal Artery (a. hccmorrhoidalis superior) (Fig. 538), the
continuation of the inferior mesenteric, descends into the pelvis between the layers
of the mesentery of the sigmoid colon, crossing, in its course, the left common
iliac vessels. It divides, opposite the third sacral vertebra, into two branches,
which descend one on either side of the rectum, and about 10 or 12 cm, from the
anus break up into several small branches. These pierce the muscular coat of the
bowel and run downward, as straight vessels, placed at regular intervals from each
other in the wall of the gut between its muscular and mucous coats, to the level
of the Sphincter ani internus; here they form a series of loops around the lower end
of the rectum, and communicate with the middle hemorrhoidal branches of the
hypogastric, and with the inferior hemorrhoidal branches of the internal pudendal.
The middle suprarenal arteries {aa. suprarenales media; middle capsular arteries;
suprarenal arteries) are two small vessels which arise, one from either side of the
aorta, opposite the superior mesenteric artery. They pass lateralward and slightly
upward, over the crura of the diaphragm, to the suprarenal glands, where they
anastomose with suprarenal branches of the inferior phrenic and renal arteries. In
the fetus these arteries are of large size.
The renal arteries (aa. renales) (Fig. 531), are two large trunks, which arise
from the side of the aorta, immediately below the superior mesenteric artery.
Each is directed across the crus of the diaphragm, so as to form nearly a right
angle with the aorta. The right is longer than the left, on account of the position
of the aorta; it passes behind the inferior vena cava, the right renal vein, the head
of the pancreas, and the descending part of the duodenum. The left is somewhat
higher than the right; it lies behind the left renal vein, the body of the pancreas
and the lienal vein, and is crossed by the inferior mesenteric vein. Before reaching
the hilus of the kidney, each artery divides into four or five branches; the greater
number of these lie between the renal vein and ureter, the vein being in front,
the ureter behind, but one or more branches are usually situated behind the ureter.
Each vessel gives oft" some small inferior suprarenal branches to the suprarenal
gland, the ureier, and the surrounding cellular tissue and muscles. One or two
accessory renal arteries are frequently found, more especially on the left side
THE ABDOMINAL AORTA
611
(hey usually arise from the aorta, and may come off above or below the main artery,
the former being the more common position. Instead of entering the kidney at the
hilus, they usually pierce the upper or lower part of the gland.
The internal spermatic arteries {aa. spermaticae interna'; spermatic arteries)
(Fig. 531) are distributed to the testes. They are two slender vessels of consid-
erable length, and arise from the front of the aorta a little below the renal arteries.
Each passes obliquely downward and lateralward behind the peritoneum, resting
on the Psoas major, the right spermatic lying in front of the inferior vena cava
and behind the middle colic and ileocolic arteries and the terminal part of the
ileum, the left behind the left colic and sigmoid arteries and the iliac colon. Each
crosses obliquely over the ureter and the lower part of the external iliac artery
Fig. 538. — Sigmoid colon and rectum, showing distribution of branches of inferior mesenteric artery and their
anastomoses. (From a preparation by Mr. Hamilton Drummond.) Prepared in same manner as Fig. 535.
to reach the abdominal inguinal ring, through which it passes, and accompanies
the other constituents of the spermatic cord along the inguinal canal to the
scrotum, where it becomes tortuous, and divides into several branches. Two or
three of these accompany the ductus deferens, and supply the epididymis, anasto-
mosing with the artery of the ductus deferens; others pierce the back part of the
tunica albuginea, and supply the substance of the testis. The internal spermatic
artery supplies one or two small branches to the ureter, and in the inguinal canal
gives one or two twigs to the Cremaster.
The ovarian arteries {aa. omricoe) are the corresponding arteries in the female
to the internal spermatic in the male. They supply the ovaries, are shorter than the
internal spermatics, and do not pass out of the abdominal cavity. The origin
and course of the first part of each artery are the same as those of the internal
612 ANGIOLOGY
spermatic, but on arriving at the upper opening of the lesser pelvis the ovarian
artery passes inward, between the two layers of the ovariopelvic ligament and of
the broad ligament of the uterus, to be distributed to the ovary. Small branches
are given to the ureter and the uterine tube, and one passes on to the side of the
uterus, and unites with the uterine artery. Other offsets are continued on the round
ligament of the uterus, through the inguinal canal, to the integument of the labium
ma jus and groin.
At an early period of fetal life, when the testes or ovaries lie by the side of the
vertebral column, below the kidneys, the internal spermatic or ovarian arteries
are short; but with the descent of these organs into the scrotum or lesser pelvis,
the arteries are gradually lengthened.
The inferior phrenic arteries (aa. phrenicce inferiores) (Fig. 531) are two small
vessels, which supply the diaphragm but present much variety in their origin.
They may arise separately from the front of the aorta, immediately above the celiac
artery, or by a common trunk, which may spring either from the aorta or from the
celiac artery. Sometimes one is derived from the aorta, and the other from one of
the renal arteries; they rarely arise as separate vessels from the aorta. They
diverge from one another across the crura of the diaphragm, and then run ob-
liquely upward and lateralward upon its under surface. The left phrenic passes
behind the esophagus, and runs forward on the left side of the esophageal hiatus.
The right phrenic passes behind the inferior vena cava, and along the right side
of the foramen which transmits that vein. Near the back part of the central
tendon each vessel divides into a medial and a lateral branch. The medial branch
curves forward, and anastomoses with its fellow of the opposite side, and with
the musculophrenic and pericardiacophrenic arteries. The lateral branch passes
toward the side of the thorax, and anastomoses with the lower intercostal arteries,
and with the musculophrenic. The lateral branch of the right phrenic gives off
a few vessels to the inferior vena cava; and the left one, some branches to the
esophagus. Each vessel gives off superior suprarenal branches to the suprarenal
gland of its own side. The spleen and the liver also receive a few twigs from the
left and right vessels respectively.
The lumbar arteries (aa. lumbales) are in series with the intercostals. They
are usually four in number on either side, and arise from the back of the aorta,
opposite the bodies of the upper four lumbar vertebrse. A fifth pair, small in size,
is occasionally present : they arise from the middle sacral artery. They run lateral-
ward and backward on the bodies of the lumbar vertebrae, behind the sympathetic
trunk, to the intervals between the adjacent transverse processes, and are then
continued into the abdominal wall. The arteries of the right side pass behind the
inferior vena cava, and the upper two on each side run behind the corresponding
cms of the diaphragm. The arteries of both sides pass beneath the tendinous
arches which give origin to the Psoas major, and are then continued behind this
muscle and the lumbar plexus. They now cross the Quadratus lumborum, the upper
three arteries running behind, the last usually in front of the muscle. At the lateral
border of the Quadratus lumborum they pierce the posterior aponeurosis of the
Transversus abdominis and are carried forward between this muscle and the
Obliquus internus. They anastomose \,ith the lower intercostal, the subcostal,
the iliolumbar, the deep iliac circumflex, and the inferior epigastric arteries.
Branches. — In the interval between the adjacent transverse processes each lumbar
artery gives off a posterior ramus which is continued backward between the trans-
verse processes and is distributed to the muscles and skin of the back; it furnishes
a spinal branch which enters the vertebral canal and is distributed in a manner
similar to the spinal branches of the posterior rami of the intercostal arteries
(page 601). Muscular branches are supplied from each lumbar artery and from its
posterior ramus to the neighboring muscles.
THE COMMON ILIAC ARTERIES
613
The middle sacral artery (a. sacralis media) (Fig. 531) is a small vessel, which
arises from the back of the aorta, a little above its bifurcation. It descends in
the middle line in front of the fourth and fifth lumbar vertebrae, the sacrum and
coccyx, and ends in the glomus coccygeum {coccygeal gland). From it, minute
branches are said to pass to the posterior surface of the rectum. On the last
lumbar vertebra it anastomoses with the lumbar branch of the iliolumbar artery;
in front of the sacrum it anastomoses with the lateral sacral arteries, and sends
offsets into the anterior sacral foramina. It is crossed by the left common iliac
vein, and is accompanied by a pair of venae comitantes; these unite to form a single
vessel, which opens into the left common iliac vein.
^a»-:l
Middle sacral
Sup. hemorrhoidal
Fig. 539. — The arteries of the pelvis.
THE COMMON ILIAC ARTERIES (AA. ILIAC^ COMMUNES) (Figs. 531, 539).
The abdominal aorta divides, on the left side of the body of the fourth lumbar
vertebra, into the two common iliac arteries. Each is about 5 cm. in length. They
diverge from the termination of the aorta, pass downward and lateralward, and
divide, opposite the intervertebral fibrocartilage between the last lumbar vertebra
and the sacrum, into two branches, the external iliac and hypogastric arteries;
the former supplies the lower extremity; the latter, the viscera and parietes of the
pelvis.
614 ANGIOLOGY
The right common iliac artery (Fig. 539) is somewhat longer than the left, and
passes more obliquely across the body of the last lumbar vertebra. In front of
it are the peritoneum, the small intestines, branches of the sympathetic nerves,
and, at its point of division, the ureter. Behind, it is separated from the bodies of
the fourth and fifth lumbar vertebrae, and the intervening fibrocartilage, by the
terminations of the two common iliac' veins and the commencement of the inferior
vena cava. Laterally, it is in relation, above, with the inferior vena cava and the
right common iliac vein; and, below, with the Psoas major. Medial to it, above,
is the left common iliac vein.
The left common iliac artery is in relation, in front, with the peritoneum, the
small intestines, branches of the sympathetic nerves, and the superior hemorrhoidal
artery; and is crossed at its point of bifurcation by the ureter. It rests on the
bodies of the fourth and fifth lumbar vertebrae, and the intervening fibrocartilage.
The left common iliac vein lies partly viedial to, and partly behind the artery;
laterally, the artery is in relation with the Psoas major.
Branches. — The common iliac arteries give off small branches to the peritoneum,
Psoas major, ureters, and the surrounding areolar tissue, and occasionally give
origin to the iliolumbar, or accessory renal arteries.
Peculiarities. — The point of origin varies according to the bifurcation of the aorta. In three-
fourths of a large number of cases, the aorta bifurcated either upon the fourth lumbar vertebra,
or upon the fibrocartilage between it and the fifth; the bifurcation being, in one case out of nine,
below, and in one out of eleven, above this point. In about SO per cent, of the cases the aorta
bifurcated within 1.25 cm. above or below the level of the crest of the ilium; more frequently
below than above.
The ■point of division is subject to great varietj'. In two-thirds of a large number of cases it
was between the last lumbar vertebra and the upper border of the sacrum; being above that point
in one case out of eight, and below it in one case out of six. The left common iUac artery divides
lower do^Ti more frequently than the right.
The relative lengths, also, of the two common iliac arteries vary. The right common iliac was
the longer in sixty-three cases; the left in fiftj'-two; while thej' were equal in fiftjMhree. The
length of the arteries varied, in five-sevenths of the cases examined, from 3.5 to 7.5 cm.; in about
half of the remaining cases the arterj' was longer, and in the other half, shorter; the minimima
length being less than 1.25 cm., the maximum, 11 cm. In rare instances, the right common
iliac has been found wanting, the external ihac and hypogastric arising directly from the aorta.
Collateral Circulation. — The principal agents in carrjdng on the collateral circulation after the
application of a hgature to the common iliac are: the anastomoses of the hemorrhoidal branches
of the hjTJOgastric with the superior hemorrhoidal from the inferior mesenteric; of the uterine,
ovarian, and vesical arteries of the opposite sides; of the lateral sacral with the middle sacral
artery; of the inferior epigastric with the internal mammary, inferior intercostal, and lumbar
arteries; of the deep iliac circmnflex with the lumbar arteries; of the iholumbar with the last
lumbar artery; of the obturator artery, by means of its pubic branch, with the vessel of the
opposite side and with the inferior epigastric.
The Hypogastric Artery (A. Hypogastrica ; Internal Iliac Artery) (Fig. 539).
The hypogastric artery supplies the walls and viscera of the pelvis, the buttock,
the generative organs, and the medial side of the thigh. It is a short, thick vessel,
smaller than the external iliac, and about 4 cm. in length. It arises at the bifur-
cation of the common iliac, opposite the lumbosacral articulation, and, passing
downward to the upper margin of the greater sciatic foramen, divides into two
large trunks, an anterior and a posterior.
Relations. — It is in relation in front with the ureter; behind, with the internal Uiac vein, the
lumbosacral trimk, and the Piriformis muscle; laterally, near its origin, with the external iUac
vein, which lies between it and the Psoas major muscle; lower down, with the obturator nerve.
In the fetus, the hypogastric artery is twice as large as the external iliac, and is
the direct continuation of the common iliac. It ascends along the side of the
bladder, and runs upward on the back of the anterior wall of the abdomen to the
umbilicus, converging toward its fellow of the opposite side. Having passed through
THE HYPOGASTRIC ARTERY 615
the umbilical opening, the two arteries, now termed umbilical, enter the umbilical
cord, where they are coiled around the umbilical vein, and ultimately ramify in
the placenta.
At birth, when the placental circulation ceases, the pelvic portion only of the
artery remains patent and constitutes the hypogastric and the first part of the
superior vesical artery of the adult; the remainder of the vessel is converted into
a solid fibrous cord, the lateral umbilical ligament (obliterated hypogastric artery)
which extends from the pelvis to the umbilicus.
Peculiarities as Regards Length. — In two-thirds of a laxge number of cases, the length of the
hypogastric varied between 2.25 and 3.4 cm.; in the remaining third it was more frequently
longer than shorter, the maximum length being about 7 cm. the minimum about 1 cm.
The lengths of the common iliac and hypogastric arteries bear an inverse proportion to each
other, the hypogastric artery being long when the common iliac is short, and vice versa.
As Regards its Place of Division. — The place of division of the hypogastric varies between
the upper margin of the sacrum and the upper border of the greater sciatic foramen.
The right and left hypogastric arteries in a series of cases often differed in length, but neither
seemed constantly to exceed the other.
Collateral Circulation. — The circulation after Mgature of the hypogastric artery is carried on
by the anastomoses of the uterine and ovarian arteries; of the vesical arteries of the two sides;
of the hemorrhoidal branches of the hypogastric with those from the inferior mesenteric; of the
obturator arterj', by means of its pubic branch, with the vessel of the opposite side, and with the
inferior epigastric and medial femoral circumflex; of the circumflex and perforating branches of
the profunda femoris with the inferior gluteal; of the superior gluteal with the posterior branches
of the lateral sacral arteries; of the iholumbar with the last lumbar; of the lateral sacral with the
middle sacral; and of the iliac circumflex with the iliolimibar and superior gluteal.^
Branches. — ^The branches of the h
ypogastric
artery are:
From the Anterior Trunk.
From the Posterior Trunk
Superior Vesical.
Iliolumbar,
jNIiddle Vesical.
Lateral Sacral.
Inferior Vesical.
Superior Gluteal.
Middle Hemorrhoidal.
Obturator.
Internal Pudendal.
Inferior Gluteal.
T' • 1 [hi the Female.
\ agmal j
The superior vesical artery (a. vesicalis superior) supplies numerous branches
to the upper part of the bladder. From one of these a slender vessel, the artery
to the ductus deferens, takes origin and accompanies the duct in its course to the
testis, where it anastomoses with the internal spermatic artery. Other branches
supply the ureter. The first part of the superior vesical artery represents the
terminal section of the per\'ious portion of the fetal hypogastric artery.
The middle vesical artery (a. resicalis medialis), usually a branch of the superior,
is distributed to the fundus of the bladder and the vesiculae seminales.
The inferior vesical artery {a. vesicalis inferior) frequently arises in common
with the middle hemorrhoidal, and is distributed to the fundus of the bladder, the
prostate, and the vesicula? seminales. The branches to the prostate communicate
with the corresponding vessels of the opposite side.
The middle hemorrhoidal artery (a. hoemorrhoidalis media) usually arises with
the preceding vessel. It is distributed to the rectum, anastomosing with the
inferior vesical and with the superior and inferior hemorrhoidal arteries. It gives
offsets to the vesiculre seminales and prostate.
The uterine artery (a. uterina) (Fig. 540) springs from the anterior division of
1 For a de.scription of a case in which Owen made a dissection ten years after ligature of the hypogastric artery,
see Med.-Chir. Trans., vol. xvi.
616
ANGIOLOGY
the hypogastric and runs medialward on the Levator ani and toward the cervix
uteri; about 2 cm. from the cervix it crosses above and in front of the ureter, to
which it supplies a small branch. Reaching the side of the uterus it ascends in a
tortuous manner between the two layers of the broad ligament to the junction
of the uterine tube and uterus. It then runs lateralward toward the hilus of the
ovary, and ends by joining with the ovarian artery. It supplies branches to the
cervix uteri and others which descend on the vagina; the latter anastomose with
branches of the vaginal arteries and form with them two median longitudinal
vessels — the azygos arteries of the vagina — one of which runs down in front of
and the other behind the vagina. It supplies numerous branches to the body of the
uterus, and from its terminal portion twigs are distributed to the uterine tube and
the round ligament of the uterus.
The vaginal artery (a. vaginalis) usually corresponds to the inferior vesical in
the male; it descends upon the vagina, supplying its mucous membrane, and sends
branches to the bulb of the vestibule, the fundus of the bladder, and the contiguous
part of the rectum. It assists in forming the azygos arteries of the vagina, and
is frequently represented by two or three branches.
Branches to tube
Branches to fundus
Fio. 540. — The arteries of the internal organs of generation of the female, seen from behind. (After Hyrtl.)
The obturator artery (a. ohturatoria) passes forward and downward on the lateral
wall of the pelvis, to the upper part of the obturator foramen, and, escaping from
the pelvic cavity through the obturator canal, it divides into an anterior and a
posterior branch. In the pelvic cavity this vessel is in relation, laterally, with the
obturator fascia; medially, with the ureter, ductus deferens, and peritoneum;
while a little below it is the obturator nerve.
Branches. — Inside the pelvis the obturator artery gives off iliac branches to the
iliac fossa, which supply the bone and the Ihacus, and anastomose with the ilio-
lumbar artery; a vesical branch, which runs backward to supply the bladder; and
a pubic branch, which is given off from the vessel just before it leaves the pelvic
cavity. The pubic branch ascends upon the back of the pubis, communicating
THE HYPOGASTRIC ARTERY 617
with the corresponding vessel of the opposite side, and with the inferior epigastric
artery.
Outside the yehis, the obturator artery divides at the upper margin of the obtur-
ator foramen, into an anterior and a posterior branch which encircle the foramen
under cover of the Obturator externus.
The anterior branch runs forward on the outer surface of the obturator mem-
brane and then curves downward along the anterior margin of the foramen. It
distributes branches to the Obturator externus, Pectineus, Adductores, and Gracilis,
and anastomoses with the posterior branch and with the medial femoral circum-
flex artery.
The posterior branch follows the posterior margin of the foramen and turns for-
ward on the inferior ramus of the ischium, where it anastomoses with the anterior
branch. It gives twigs to the muscles attached to the ischial tuberosity and anas-
tomoses with the inferior gluteal. It also supplies an articular branch which
enters the hip-joint through the acetabular notch, ramifies in the fat at the bottom
of the acetabulum' and sends a twig along the ligamentum teres to the head of the
femur.
Peculiarities. — The obturator artery sometimes arises from the main stem or from the posterior
trunk of the hypogastric, or it may spring from the superior gluteal artery; occasionally it arises
from the external iliac. In about two out of every seven cases it springs from the inferior epi-
gastric and descends almost vertically to the upper part of the obturator foramen. The artery
in this course usually Ues in contact with the external ihac vein, and on the lateral side of the
femoral ring (Fig. 54 IJ.) ; in such cases it would not be endangered in the operation for strangulated
femoral hernia. Occasionally, however, it curves along the free margin of the lacunar hgament
(Fig. 5415), and if in such circumstances a femoral hernia occurred, the vessel would almost
completely encircle the neck of the hernial sac, and would be in great danger of being wovmded
if an operation were performed for strangulation.
Fig. 541.- — Variations in origin and course of obturator artery.
The internal pudendal artery (a. imdenda interna; internal imdic artery) is the
smaller of the two terminal branches of the anterior trunk of the hypogastric, and
supplies the external organs of generation. Though the course of the artery is
the same in the two sexes, the vessel is smaller in the female than in the male, and
the distribution of its branches somewhat different. The description of its arrange-
ment in the male will first be given, and subsequent!} the differences which it
presents in the female will be mentioned.
The internal pudendal artery in the male passes downward and outward to the
lower border of the greater sciatic foramen, and emerges from the pelvis between
the Piriformis and Coccygeus; it then crosses the ischial spine, and enters the peri-
neum through the lesser sciatic foramen. The artery now crosses the Obturator
internus, along the lateral wall of the ischiorectal fossa, being situated about 4 cm.
above the lower margin of the ischial tuberosity. It gradually approaches the
margin of the inferior ramus of the ischium and passes forward between the two
layers of the fascia of the urogenital diaphragm; it then runs forward along the
medial margin of the inferior ramus of the pubis, and about 1.25 cm. behind the
pubic arcuate ligament it pierces the inferior fascia of the urogenital diaphragm
and divides into the dorsal and deep arteries of the penis.
618
ANGIOLOGY
Relations. — Within the pelvis, it lies in front of the Piriformis muscle, the sacral plexus of
nerv^es, and the inferior gluteal artery. As it crosses the ischial spine, it is covered by the Gluta?us
maximus and overlapped by the sacrotuberous ligament. Here the pudendal nerve hes to the
medial side and the nerve to the Obturator internus to the lateral side of the vessel. In the peri-
neum it lies on the lateral wall of the ischiorectal fossa, in a canal (Alcock's canal) formed by the
splitting of the obturator fascia. It is accompanied by a pair of vena; comitantes and the pudendal
nerve.
Peculiarities. — The internal pudendal artery is sometimes smaller than usual, or fails to give
off one or two of its usual branches; in such cases the deficiency is supplied by branches derived
from an additional vessel, the accessory pudendal, which generally arises from the internal
pudendal artery before its exit from the greater sciatic foramen. It passes forward along the
lower part of the bladder and across the side of the prostate to the root of the penis, where it
perforates the vurogenital diaphragm, and gives off the branches usually derived from the internal
pudendal artery. The deficiency most frequently met with is that in which the internal pudendal
ends as the artery of the uretliral bulb, the dorsal and deep arteries of the penis being derived
from the accessory pudendal. The internal pudendal artery may also end as the perineal, the
artery of the urethral bulb being derived, with the other two branches, from the accessory vessel.
Occasionally the accessory pudendal artery is derived from one of the other branches of the
hypogastric artery, most frequently the inferior vesical or the obturator.
Branches.— The branches of the internal pudendal artery (Figs. 542, 543) are:
IVIuscular. Artery of the Urethral Bulb.
Inferior Hemorrhoidal. Urethral.
Perineal. Deep Artery of the Penis.
Dorsal Artery of the Penis.
Posterior scrotal arteries
Posterior scrotal nerves
Pudendal nerve
Internal pudendal artery
Fig. 542. — The superficial branches of the internal pudendal artery.
\
The Muscular Branches consist of two sets: one given off in the pelvis; the other,
as the vessel crosses the ischial spine. The former consists of several small offsets
which supply the Levator ani, the Obturator internus, the Piriformis, and the
Coccygeus. The branches given off outside the pelvis are distributed to the
adjacent parts of the Glutseus maximus and external rotator muscles. They
anastomose with branches of the inferior gluteal artery.
THE HYPOGASTRIC ARTERY
619
The Inferior Hemorrhoidal Artery (a. hcemorrhoidalis inferior) arises from the
internal pudendal as it passes above the ischial tuberosity. Piercing the wall
of Alcock's canal it divides into two or three branches which cross the ischiorectal
fossa, and are distributed to the muscles and integument of the anal region, and
send offshoots around the lower edge of the Glutseus maximus to the skin of the
buttock. They anastomose with the corresponding vessels of the opposite side, with
the superior and middle hemorrhoidal, and with the perineal artery.
The Perineal Artery (a. iJerinei; superficial perineal artery) arises from the internal
pudendal, in front of the preceding branches, and turns upward, crossing either
over or under the Transversus perinsei superficialis, and runs forward, parallel
to the pubic arch, in the interspace between the Bulbocavernosus and Ischiocaver-
nosus, both of which it supplies, and finally divides into several posterior scrotal
branches which are distributed to the skin and dartos tunic of the scrotum. As
it crosses the Transversus perinsei superficialis it gives off the transverse perineal
artery which runs transversely on the cutaneous surface of the muscle, and anasto-
moses with the corresponding vessel of the opposite side and with the perineal
and inferior hemorrhoidal arteries. It supplies the Transversus periucnei super-
ficialis and the structures between the anus and the urethral bulb.
Deep artery of penis
Dorsal artery of penis
Artery of urethral hiilb
Internal pudendal artery -
Bulho-urcthral gland
Fig. 543. — The deeper branches of the internal pudendal artery.
The Artery of the Urethral Bulb (a. Imlhi vrethrcp) is a short vessel of large caliber
which arises from the internal pudendal between the two layers of fascia of the uro-
genital diaphragm; it passes medialward, pierces the inferior fascia of the urogenital
diaphragm, and gives off branches which ramify in the bulb of the urethra and in
the posterior part of the corpus cavernosum urethrse. It gives off a small branch
to the bulbo-urethral gland.
The Urethral Artery (a. urethralis) arises a short distance in front of the artery
of the urethral bulb. It runs forward and medialw^ard, pierces the inferior fascia
of the urogenital diaphragm and enters the corpus cavernosum urethrse, in which
it is continued forward to the glans penis.
620 ■ ANGIOLOGY
The Deep Artery of the Penis (a. 'profunda penis; artery to the corpus cavernosum),
one of the terminal branches of the internal pudendal, arises from that vessel
while it is situated between the two fascife of the urogenital diaphragm; it
pierces the inferior fascia, and, entering the crus penis obliquely, runs forward
in the center of the corpus cavernosum penis, to which its branches are distributed.
The Dorsal Artery of the Penis (a. dorsalis i^enis) ascends between the crus penis
and the pubic symphysis, and, piercing the inferior fascia of the urogenital dia-
phragm, passes between the two layers of the suspensory ligament of the penis,
and runs forward on the dorsum of the penis to the glans, where it divides into two
branches, which supply the glans and prepuce. On the penis, it lies between the
dorsal nerve and deep dorsal vein, the former being on its lateral side. It supplies
the integument and fibrous sheath of the corpus cavernosum penis, sending branches
through the sheath to anastomose with the preceding vessel.
The internal pudendal artery in the female is smaller than in the male. Its origin
and course are similar, and there is considerable analogy in the distribution of its
branches. The perineal artery supplies the labia pudendi; the artery of the bulb
supplies the bulbus vestibuli and the erectile tissue of the vagina; the deep artery
of the clitoris supplies the corpus cavernosum clitoridis; and the dorsal artery of
the clitoris supplies the dorsum of that organ, and ends in the glans and prepuce
of the clitoris. ■
The inferior gluteal artery (a. gluto'a inferior; sciatic artery) (Fig. 544), the
larger of the two terminal branches of the anterior trunk of the hypogastric, is
distributed chiefly to the buttock and back of the thigh. It passes down on the
sacral plexus of nerves and the Piriformis, behind the internal pudendal artery,
to the lower part of the greater sciatic foramen, through which it escapes from the
pelvis between the Piriformis and Coccygeus. It then descends in the interval
between the greater trochanter of the femur and tuberosity of the ischium, accom-
panied by the sciatic and posterior femoral cutaneous nerves, and covered by the
Glutseus maximus, and is continued down the back of the thigh, supplying the
skin, and anastomosing with branches of the perforating arteries.
Inside the pelvis it distributes branches to the Piriformis, Coccygeus, and Levator
ani; some branches which supply the fat around the rectum, and occasionally
take the place of the middle hemorrhoidal artery; and vesical branches to the
fundus of the bladder, vesiculje seminales, and prostate. • Outside the pelvis it gives
off the following branches:
Muscular. Anastomotic.
Coccygeal. Articular.
Comitans Nervi Ischiadici. Cutaneous.
The Muscular Branches supply the Glut?eus maximus, anastomosing with the
superior gluteal artery in the substance of the muscle; the external rotators,
anastomosing with the internal pudendal artery; and the muscles attached to
the tuberosity of the ischium, anastomosing with the posterior branch of the
obturator and the medial femoral circumflex arteries.
The Coccygeal Branches run medialward, pierce the sacrotuberous ligament, and
supply the Gluta^us maximus, the integument, and other structures on the back
of the coccyx.
The Arteria Comitans Nervi Ischiadici is a long, slender vessel, which accom-
panies the sciatic nerve for a short distance; it then penetrates it, and runs in its
substance to the lower part of the thigh.
The Anastomotic is directed downward across the external rotators, and assists
in forming the so-called crucial anastomosis by joining with the first perforating
and medial and lateral femoral circumflex arteries.
The Articular Branch, generally derived from the anastomotic, is distributed to
the capsule of the hip-joint.
\
THE HYPOGASTRIC ARTERY
621
The Cutaneous Branches are distributed to the skin of the buttock and back of
the thigh.
The iliolumbar artery {a. iliolumhalis) a branch of the posterior trunk of the
hypogastric, turns upward behind the obturator nerve and the external ihac vessels,
to the medial border of the Psoas major, behind which it divides into a lumbar and
an iliac branch.
The Lumbar Branch {ramus himhalis) supplies the' Psoas major and Quadratus
lumborum, anastomoses with the last lumbar artery, and sends a small spinal
branch through the intervertebral
foramen between the last lumbar
vertebra and the sacrum, into the
vertebral canal, to supply the
Cauda equina.
The Iliac Branci {ramus iliacus)
descends to supply the Iliacus;
some offsets, running between the
muscle and the bone, anastomose
with the iliac branches of the ob-
turator; one of these enters an
oblique canal to supply the bone,
while others run along the crest of
the ilium, distributing branches to
the gluteal and abdominal muscles,
and anastomosing in their course
with the superior gluteal, iliac
circumflex, and lateral femoral
circumflex arteries.
The lateral sacral arteries {aa.
sacrales laterales) (Fig. 539) arise
from the posterior division of the
hypogastric; there are usually two,
a superior and an inferior.
The superior, of large size, passes
medial ward, and, after anastomos-
ing with branches from the middle
sacral, enters the first or second
anterior sacral foramen, supplies
branches to the contents of the
sacral canal, and, escaping by the
corresponding posterior sacral fora-
men, is distributed to the skin and
muscles on the dorsum of the
sacrum, anastomosing with the
superior gluteal.
The inferior runs obliquely across
the front of the Piriformis and the
sacral nerves to the medial side of
the anterior sacral foramina, de-
scends on the front of the sacrum,
and anastomoses over the coccjtc
with the middle sacral and opposite
lateral sacral artery. In its course it gives off branches, which enter the anterior
sacral foramina; these, after supplying the contents of the sacral canal, escapes
by the posterior sacral foramina, and are distributed to the muscles and skin on
the dorsal surface of the sacrum, anastomosing with the gluteal arteries.
Termination oj
■medial femoral
circumflex
-First
perforating
Second
perforating
Third
perforating
Term,ination
of profunda
Superior muscular
Lateral
superior
genicular
Fia. 544.
Medial superior genicular
\^ Sural
-The arteries of the gluteal and posterior
femoral regions.
622 ANGIOLOGY
The superior gluteal artery (o. ghdcea superior; gluteal artery) (Fig. 544) is the
largest branch of the hypogastric, and appears to be the continuation of the pos-
terior division of that vessel. It is a short artery which runs backward between
the lumbosacral trunk and the first sacral nerve, and, passing out of the pelvis
above the upper border of the Piriformis, immediately divides into a superficial
and a deep branch. Within the pelvis it gives off a few branches to the Iliacus,
Piriformis, and Obturator internus, and just previous to quitting that cavity, a
nutrient artery which enters the ilium.
The superficial branch enters the deep surface of the Glutseus maximus, and
divides into numerous branches, some of which supply the muscle and anastomose
with the inferior gluteal, while others perforate its tendinous origin, and supply
the integument covering the posterior surface of the sacrum, anastomosing with
the posterior branches of the lateral sacral arteries.
The deep branch lies under the Glutseus medius and almost immediately sub-
divides into two. Of these, the superior division, continuing the original course
of the vessel, passes along the upper border of theGlutaeus minimus to the anterior
superior spine of the ilium, anastomosing with the deep iliac circumflex artery and
the ascending branch of the lateral femoral circumflex artery. The inferior division
crosses the Glutseus minimus obliquely to the greater trochanter, distributing
branches to the Glutsei and anastomoses with the lateral femoral circumflex artery.
Some branches pierce the Gluta?us minimus and supply the hip-joint.
The External Iliac Artery (A. Iliaca Externa) (Fig. 539).
The external iliac artery is larger than the hypogastric, and passes obliquely
downward and lateralward along the medial border of the Psoas major, from the
bifurcation of the common iliac to a point beneath the inguinal ligament, midway
between the anterior superior spine of the ilium and the symphysis pubis, where
it enters the thigh and becomes the femoral artery.
Relations. — In front and medially, the artery is in relation with the peritoneum, subperitoneal
areolar tissue, the termination of the ileum and frequently the vermiform process on the right
side, and the sigmoid colon on the left, and a thin layer of fascia, derived from the ihac fascia,
which surrounds the artery and vein. At its origin it is crossed by the ovarian vessels in the
female, and occasionally by the ureter. The internal spermatic vessels lie for some distance
upon it near its termination, and it is crossed in this situation by the external spermatic branch
of the genitofemoral nerve and the deep iliac circumflex vein; the ductus deferens in the male,
and the round ligament of the uterus in the female, curve down across its medial side. Behind,
it is in relation with the medial border of the Psoas major, from which it is separated by the
iUac fascia. At the upper part of its course, the external ihac vein lies partly behind it, but lower
down hes entirely to its medial side. Laterally, it rests against the Psoas major, from which it
is separated by the iliac fascia. Numerous lymphatic vessels and lymph glands he on the front
and on the medial side of the vessel.
Collateral Circulation. — The principal anastomoses in carrying on the collateral circulation,
after the application of a ligature to the external ihac, are: the iUolumbar with the ihac circum-
flex; the superior gluteal with the lateral femoral circumflex; the obturator with the medial femoral
circumflex; the inferior gluteal with the first perforating and circumflex branches of the profunda
artery; and the internal pudendal with the external pudendal. When the obturator arises from
the inferior epigastric, it is supplied with blood by branches, from either the hypogastric, the
lateral sacral, or the internal pudendal. The inferior epigastric receives its supply from the
internal mammarj^ and lower intercogtal arteries, and from the hypogastric by the anastomoses
of its branches with the obturator.^
Branches. — Besides several small branches to the Psoas major and the neighbor-
ing lymph glands, the external iliac gives off two branches of considerable size:
Inferior Epigastric. Deep Iliac Circumflex.
1 Sir Astley Cooper describes in Guy's Hospital Reports, vol. i, the dissection of a limb eighteen years after successful
ligature of the external iliac artery.
1
THE FEMORAL ARTERY 623
The inferior epigastric artery (a. epigastrica inferior; deep epigastric artery)
(Fig. 547) arises from the external iUac, immediately above the inguinal ligament.
It curves forward in the subperitoneal tissue, and then ascends obliquely along
the medial margin of the abdominal inguinal ring; continuing its course upward,
it pierces the transversalis fascia, and, passing in front of the linea semicircularis,
ascends between the Rectus abdominis and the posterior lamella of its sheath.
It finally divides into numerous branches, which anastomose, above the umbilicus,
with the superior epigastric branch of the internal mammary and with the lower
intercostal arteries (Fig. 522). As the inferior epigastric artery passes obliquely
upward from its origin it lies along the lower and medial margins of the abdominal
inguinal ring, and behind the commencement of the spermatic cord. The ductus
deferens, as it leaves the spermatic cord in the male, and the round ligament of the
uterus in the female, winds around the lateral and posterior aspects of the artery.
Branches. — The branches of the vessel are : the external spermatic artery {cremasteric
artery), which accompanies the spermatic cord, and supplies the Cremaster and
other coverings of the cord, anastomosing with the internal spermatic artery (in
the female it is very small and accompanies the round ligament) ; a pubic branch
which runs along the inguinal ligament, and then descends along the medial margin
of the femoral ring to the back of the pubis, and there anastomoses with the pubic
branch of the obturator artery ; muscular branches, some of which are distributed to
the abdominal muscles and peritoneum, anastomosing with the iliac circumflex
and lumbar arteries; branches which perforate the tendon of the Obliquus
externus, and supply the integument, anastomosing with branches of the super-
ficial epigastric.
Peculiarities. — The origin of the inferior epigastric may take place from any part of the external
iliac between the inguinal ligament and a point 6 cm. above it; or it may arise below this ligament,
from the femoral. It frequently springs from the external iUac, by a common trunk with the
obturator. Sometimes it arises from the obturator, the latter vessel being furnished by the
hypogastric, or it may be formed of two branches, one derived from the external ihac, the other
from the hypogastric.
The deep iliac circumflex artery (a. circumjiexa ilium profunda) arises from the
lateral aspect of the external iliac nearly opposite the inferior epigastric artery.
It ascends obliquely lateralward behind the inguinal ligament, contained in a
fibrous sheath formed by the junction of the transversalis fascia and iliac fascia,
to the anterior superior iliac spine, where it anastomoses with the ascending branch
of the lateral femoral circumflex artery. It then pierces the transversalis fascia
and passes along the inner lip of the crest of the ilium to about its middle, where
it perforates the Transversus, and runs backward between that muscle and the
Obliquus internus, to anastomose with the iliolumbar and superior gluteal arteries.
Opposite the anterior superior spine of the ilium it gives ofi a large branch, which
ascends between the Obliquus internus and Transversus muscles, supplying them,
and anastomosing with the lumbar and inferior epigastric arteries.
THE ARTERIES OF THE LOWER EXTREMITY.
The artery which supplies the greater part of the lower extremity is the direct
continuation of the external iliac. It runs as a single trunk from the inguinal
ligament to the lower border of the Popliteus, where it divides into two branches,
the anterior and posterior tibial. The upper part of the main trunk is named the
femoral, the lower part the popliteal.
THE FEMORAL ARTERY (A. FEMORALIS) (Figs. 549, 550).
The femoral artery begins immediately behind the inguinal ligament, midway
between the anterior superior spine of the ilium and the symphysis pubis, and
624
ANGIOLOGY
Fi<i. 54o. — Femoral sheath laid open to show its three compartments.
Lai. fern, cuiau. nerve
/
Femoral nerve
^2^ /' Lumho-iyiguiiial nerve
Femoral arlcry
Femoral sheath
Femoral vein
Femoral ring
Lacunar ligament
Fig. 546. — Structures passing behind the inguinal ligament.
THE FEMORAL ARTERY
G25
passes down the front and medial side of the thigh. It ends at the junction of the
middle with the lower third of the thigh, where it passes through an opening in
the Adductor magnus to become the popliteal artery. The vessel, at the upper part
of the thigh, lies in front of the hip-joint; in the lower part of its course it lies to
the medial side of the body of the femur, and between these two parts, where it
crosses the angle between the head and body, the vessel is some distance from the
bone. The first 4 cm. of the vessel is enclosed, together with the femoral vein,
in a fibrous sheath — the femoral sheath. In the upper third of the thigh the femoral
artery is contained in the femoral triangle (Scarpa's triangle), and in the middle
third of the thigh, in the adductor canal {Hunter's canal).
The femoral sheath (crural sheath) (Figs. 545, 546) is formed by a prolongation
downward, behind the inguinal ligament, of the fasciae which line the abdomen,
the transversalis fascia being continued down in front of the femoral vessels and
the iliac fascia behind them. The sheath assumes the form of a short funnel, the
wide end of which is directed upward, while the lower, narrow end fuses with the
Fig. 547. — The relations of the femoral and abdominal inguinal rings, seen from within the abdomen. Right side.
fascial investment of the vessels, about 4 cm. below the inguinal ligament. It is
strengthened in front by a band termed the deep crural arch (page 419). The lateral
wall of the sheath is vertical and is perforated by the lumboinguinal nerve; the
medial wall is directed obliquely downward and lateralward, and is pierced by the
great saphenous vein and by some lymphatic vessels. The sheath is divided by
two vertical partitions which stretch between its anterior and posterior walls.
The lateral compartment contains the femoral artery, and the intermediate the
femoral vein, while the medial and smallest compartment is named the femoral
canal, and contains some lymphatic vessels and a lymph gland imbedded in a small
amount of areolar tissue. The femoral canal is conical and measures about 1.25
cm. in length. Its base, directed upward and named the femoral ring, is oval in
form, its long diameter being directed transversely and measuring about 1.25 cm.
The femoral ring (Figs. 546, 547) is bounded in front by the inguinal ligament,
behind by the Pectineus covered by the pectineal fascia, medially by the crescentic
base of the lacunar ligament, and laterally by the fibrous septum on the medial
side of the femoral vein. The spermatic cord in the male and the round ligament
40
626
ANGIOLOGY
of the uterus in the female lie immediately above the anterior margin of the ring,
while the inferior epigastric vessels are close to its upper and lateral angle. The
femoral ring is closed by a somewhat condensed portion of the extraperitoneal
fatty tissue, named the septum femorale (crural septum), the abdominal surface
of which supports a small lymph gland and is covered by the parietal layer of the
peritoneum. The septum femorale is pierced by numerous lymphatic vessels
passing from the deep inguinal to the external iliac lymph glands, and the parietal
peritoneum immediately above it presents a slight depression named the femoral
fossa.
SUPERFICIAL CIR>
CUMFLEX ILIAC
EXTERNAL
CIRCUMFLEX
DESCENDING
RAMUS or
external
Circumflex
SUPERFICIAL
EXTERNAL
PUDIC
DEEP
EXTERNAL
PUDIC
INTERNAL
CIRCUM FLEX
SUPERIOR EXTER-
NAL ARTICULAR
BRANCH OF
POPLITEAL
SUPERIOR INTERNAL
ARTICU LAR
BRANCH OF
POPLITEAL
Fig. 548. — Scheme of the femoral artery. (Poirier and Charpy.)
The femoral triangle {trigonum femorale; Scarpa's triangle) (Fig. 549) corre-
sponds to the depression seen immediately below the fold of the groin. Its apex
is directed downward, and the sides are formed laterally by the medial margin
of the Sartorius, medially by the medial margin of the Adductor longus, and above
by the inguinal ligam^ent. The floor of the space is formed from its lateral to its
medial side by the Iliacus, Psoas major, Pectineus, in some cases a small part of
THE FEMORAL ARTERY
627
the Adductor brevis, and the Adductor longus; and it is divided into two nearly
equal parts by the femoral vessels, which extend from near the middle of its base
to its apex: the artery giving off in this situation jts superficial and profunda
branches, the vein receiving the deep femoral and great saphenous tributaries.
On the lateral side of the femoral artery is the femoral nerve dividing into its
branches. Besides the vessels and nerves, this space contains some fat and
lymphatics.
The adductor canal {canalis adductorius; Hunter's canal) is an aponeurotic
tunnel in the middle third of the thigh, extending from the apex of the femoral
triangle to the opening in the Adductor magnus. It is bounded, in front and later-
ally, by the Vastus medialis; behind by the Adductores longus and magnus; and
is covered in by a strong aponeurosis which extends from the Vastus medialis,
across the femoral vessels to the Adductores longus and magnus; lying on the
aponeurosis is the Sartorius muscle. The canal contains the femoral artery and
vein, the saphenous nerve, and the nerve to the Vastus medialis.
Superficial iliac circxiinjlcx itssels
Femoral nerve
Superficial epigastric vessels
Superficial external pudendal vessels
Deep external pudendal vessels
Great saphcyious vein
Fig. 549. — The left femoral triangle.
Relations of the Femoral Artery. — In the femoral triangle (Fig. 54n) the artery is superficial.
In front of it are the skin and superficial fascia, the superficial subinguinal lymph glands, the
superficial iliac circumflex vein, the superficial layer of the fascia lata and the anterior part of
the femoral sheath. The lumboinguinal nerve courses for a short distance within the lateral
compartment of the femoral sheath, and lies at first in front and then lateral to the artery. Near
the apex of the femoral triangle the medial branch of the anterior femoral cutaneous nerve
crosses the artery from its lateral to its medial side.
628
ANGIOLOGY
Behind the artery are the posterior part of the femoral sheath, the pectineal fascia, the medial
part of the tendon of the Psoas major, the Pectineus and the Adductor longus. The artery is
separated from the capsule of the hip-joint by the tendon of the Psoas major, from the Pectineus
by the femoral vein and profunda vessels, and from the Adductor longus by the femoral vein.
The nerve to the Pectineus passes medialward behind the artery. On the lateral side, of the
artery, but separated from it by some fibers of the Psoas major, is the femoral nerve. The femoral
vein is on the medial side of the upper part of the artery, but is behind the vessel in the lower
part of the femoral triangle.
Anterior tibial recurrent
Scrotum
Saphenous nerve
Highest genicular
Lateral sup. genicular
Musculo-arlicular br. of
highest genicular
Medial sup. gcnicvlar
Lateral inf. genicular — 7
Medial inf. genicular
Fig. 550. — The femoral artery.
' In the adductor canal (Fig. 550) the femoral artery is more deeply situated, being covered by
the integument, the superficial and deep fascia;, the Sartorius and the fibrous roof of the canal;
the saphenous nerve crosses from its lateral to its medial side. Behind the artery are the Adduc-
THE FEMORAL ARTERY 629
tores longiis and magnus; in front and lateral to it is the Vastus medialis. The femoral vein
lies posterior to the upper part, and lateral to the lower part of the artery
Peculiarities. — Several cases are recorded in which the femoral artery divided into two trunks
below the origin of the profunda, and became reunited near the opening in the Adductor magnus,
so as to form a single popliteal artery. One occurred in a patient who was operated upon for
popliteal aneurism. A few cases have been recorded in which the femoral artery was absent,
its place being supphed by the inferior gluteal artery which accompanied the sciatic nerve to the
popliteal fossa. The external iliac in these cases was small, and terminated in the profunda.
The femoral vein is occasionally placed along the medial side of the artery throughout the entire
extent of the femoral trangle; or it may be split so that a large vein is placed on either side of
the artery for a greater or lesser distance.
Collateral Circulation. — After hgature of the femoral artery, the main channels for carrying
on the circulation are the anastomoses between — (1) the superior and inferior gluteal branches
of the hypogastric with the medial and lateral femoral circumflex and first perforating branches
of the profunda femoris; (2) the obturator branch of the hypogastric with the medial femoral
circumflex of the profunda; (3) the internal pudendal of the hypogastric with the superficial
and deep external pudendal of the femoral; (4) the deep iUac circumflex of the external iliac with
the lateral femoral circumflex of the profunda and the superficial iliac circumflex of the femoral,
and (5) the inferior gluteal of the hypogastric with the perforating branches of the profunda.
Branches. — The branches of the femoral artery are:
Superficial Epigastric. Deep External Pudendal.
Superficial Iliac Circumflex. Muscular.
Superficial External Pudendal. Profunda Femoris.
Highest Genicular.
The superficial epigastric artery {a. epigastrica svperficialis) arises from the
front of the femoral artery about 1 cm. below the inguinal ligament, and, passing
through the femoral sheath and the fascia cribrosa, turns upward in front of the
inguinal ligament, and ascends between the two layers of the superficial fascia of
the abdominal wall nearly as far as the umbilicus. It distributes branches to the
superficial subinguinal lymph glands, the superficial fascia, and the integument;
it anastomoses with branches of the inferior epigastric, and with its fellow of the
opposite side.
The superficial iliac circumflex artery (a. circumflexa ilium, suyerficialis) , the
smallest of the cutaneous branches, arises close to the preceding, and, piercing
the fascia lata, runs lateralward, parallel with the inguinal ligament, as far as the
crest of the ilium; it divides into branches which supply the integument of the
groin, the superficial fascia, and the superficial subinguinal lymph glands, anas-
tomosing with the deep iliac circumflex, the superior gluteal and lateral femoral
circumflex arteries.
The superficial external pudendal artery (a. pudenda externa superficialis ;
superficial external pudic artery) arises from the medial side of the femoral artery,
close to the preceding vessels, and, after piercing the femoral sheath and fascia
cribrosa, courses medial ward, across the spermatic cord (or round ligament in the
female), to be distributed to the integument on the lower part of the abdomen,
the penis and scrotum in the male, and the labium majus in the female, anasto-
mosing with branches of the internal pudendal.
The deep external pudendal artery (a. pudenda externa profunda; deep external
pudic artery), more deeply seated than the preceding, passes medialward across
the Pectineus and the Adductor longus muscles; it is covered by the fascia lata,
which it pierces at the medial side of the thigh, and is distributed, in the male,
to the integument of the scrotum and perineum, in the female to the labium majus;
its branches anastomose with the scrotal (or labial) branches of the perineal artery.
Muscular branches {rami mvsculares) are supplied by the femoral artery to the
Sartorius, Vastus medialis, and Adductores.
The profunda femoris artery (a. profunda femoris; deep femoral artery) (Fig.
550) is a large vessel arising from the lateral and back part of the femoral artery,
630 ANGIOLOGY
from 2 to 5 cm. below the inguinal ligament. At first it lies lateral to the femoral
artery; it then runs behind it and the femoral vein to the medial side of the femur,
and, passing downward behind the Adductor longus, ends at the lower third of the
thigh in a small branch, which pierces the Adductor magnus, and is distributed
on the back of the thigh to the hamstring muscles. The terminal part of the pro-
funda is sometimes named the fourth perforating artery.
Relations. — Behind it, from above downward, are the Iliacus, Pectineus, Adductor brevis,
and Adductor magnus. hi front it is separated from the femoral artery by the femoral and pro-
funda veins above and by the Adductor longus below. Laterally, the origin of the Vastus medialis
intervenes between it and the femur.
Peculiarities. — This vessel sometimes arises from the medial side, and, more rarely, from the
back of the femoral artery; but a more important pecuUarity, from a surgical point of vie\\, is
that relating to the height at which the vessel arises. In three-fourths of a large number of c ises
it arose from 2.25 to 5 cm. below the inguinal ligament; in a few cases the distance was less than
2.25 cm.; more rarely, opposite the Ugament; and in one case above the inguinal ligament, fi-om
the external iliac. Occasionally the distance between the origin of the vessel and the inguinal
ligament exceeds 5 cm.
Branches. — The profunda gives off the following branches :
Lateral Femoral Circumflex. Perforating.
iNIedial Femoral Circumflex. Muscular.
The Lateral Femoral Circumflex Artery (a. circumfiexa femoris lateralis; external
circumflex artery) arises from the lateral side of the profunda, passes horizontally
between the divisions of the femoral nerve, a'^d beMnd the Sartorius and Rectus
femoris, and divides into ascending, transverse, and descending branches.
The ascending branch passes upward, beneath the Tensor fasciae latse, tf^ the
lateral aspect of the hip, and anastomoses Avith the terminal branches of the superior
gluteal and deep iliac circumflex arteries.
The descending branch runs downward, behind the Rectus femoris, upon the
Vastus lateralis, to which it gives offsets; one long branch descends in the muscle
as far as the knee, and anastomoses Avith the superior lateral genicular branch of
the popliteal artery. It is accompanied by the branch of the femoral nerve to the
Vastus lateralis.
The transverse branch, the smallest, passes lateralward over the Vastus inter-
medins, pierces the Vastus lateralis, and winds around the femur, just below the
greater trochanter, anastomosing on the back of the thigh with the medial femoral
circumflex, inferior gluteal, and first perforating arteries.
The Medial Femoral Circumflex Artery (a. circumfiexa femoris medialis; internal
circumflex artery) arises from the medial and posterior aspect of the profunda,
and winds around the medial side of the femur, passing first between the Pectineus
and Psoas major, and then between the Obturator externus and the Adductor
brevis. At the upper border of the Adductor brevis it gives oft' two branches:
one is distributed to the Adductores, the Gracilis, and Obturator externus, and
anastomoses with the obturator artery; the other descends beneath the Adductor
brevis, to supply it and the Adductor magnus; the continuation of the vessel
passes backward and divides into superficial, deep, and acetabular branches. The
superficial branch appears between the Quadratus femoris and upper border of the
Adductor magnus, and anastomoses with the inferior gluteal, lateral femoral
circumflex, and first perforating arteries (crucial aiiastomosis). The deep branch
runs obliquely upward upon the tendon of the Obturator externus and in front
of the Quadratus femoris toward the trochanteric fossa, where it anastomoses
with twigs from the gluteal arteries. The acetabular branch arises opposite the
acetabular notch and enters the hip-joint beneath the transverse ligament in com-
pany with an articular branch from the obturator artery; it supplies the fat in the
bottom of the acetabulum, and is continued along the round ligament to the head
of the femur.
THE POPLITEAL FOSSA 631
The Perforating Arteries (Tig. 544), usually three in number, are so named because
they perforate the tendon of the Adductor magnus to reach the back of the thigh.
They pass backward close to the linea aspera of the femur under cover of small
tendinous arches in the muscle. The first is given off above the Adductor brevis,
the second in front of that muscle, and the third immediately below it.
The first perforating artery (a. perforans prima) passes backward between the Pec-
tineus and Adductor brevis (sometimes it perforates the latter); it then pierces
the Adductor magnus close to the linea aspera. It gives branches to the Adductores
brevis and magnus, Biceps femoris, and Glutiieus maximus, and anastomoses with
the inferior gluteal, medial and lateral femoral circumflex and second perforating
arteries.
The second perforating artery (a. perforans secunda) , larger than the first, pierces
the tendons of the Adductores brevis and magnus, and divides into ascending
and descending branches, which supply the posterior femoral muscles, anasto-
mosing with the first and third perforating. The second artery frequently arises
in common with the first. The nutrient artery of the femur is usually given off
from the second perforating artery ; when two nutrient arteries exist, they usually
spring from the first and third perforating vessels.
The third perforating artery (a. perforans tertia) is given off below the Adductor
brevis; it pierces the Adductor magnus, and divides into branches which supply
the posterior femoral muscles; anastomosing above with the higher perforating
arteries, and below with the terminal branches of the profunda and the muscular
branches of the popliteal. The nutrient artery of the femur may arise from this
branch. The termination of the profunda artery, already described, is somjetimes
termed the fourth perforating artery.
Numerous muscular branches arise from the profunda; some of these end in the
Adductores, others pierce the Adductor magnus, give branches to the hamstrings,
and anastomose with the medial femoral circumflex artery and with the superior
muscular branches of the popliteal.
The highest genicular artery (a. genu suprema; anastomoiica magna artery) (Fig.
550) arises from the femoral just before it passes through the opening in the
tendon of the Adductor magnus, and immediately divides into a saphenous and a
musculo-articular branch.
The saphenous branch pierces the aponeurotic covering of the adductor canal,
and accompanies the saphenous nerve to the medial side of the knee. It passes
between the Sartorius and Gracilis, and, piercing the fascia lata, is distributed to
the integument of the upper and medial part of the leg, anastomosing with the
medial inferior genicular artery.
The musculo-articular branch descends in the substance of the Vastus medialis,
and in front of the tendon of the Adductor magnus, to the medial side of the knee,
where it anastomoses with the medial superior genicular artery and anterior recur-
rent tibial artery. A branch from this vessel crosses above the patellar surface
of the femur, forming an anastomotic arch with the lateral superior genicular
artery, and supplying branches to the knee-joint.
THE POPLITEAL FOSSA (Fig. 551).
Boundaries. — The popliteal fossa or space is a lozenge-shaped space, at the
back of the knee-joint. Laterally it is bounded by the Biceps femoris above,
and by the Plantaris and the lateral head of the Gastrocnemius below; medially
it is limited by the Semitendinous and Semimembranosus above, and by the medial
head of the Gastrocnemius below. The floor is formed by the popliteal surface
of the femur, the oblique popliteal ligament of the knee-joint, the upper end of the
tibia, and the fascia covering the Popliteus] the fossa is covered in by the fascia lata.
632
ANGIOLOGY
-Sural
arteries
Contents. — The popliteal fossa contains the popliteal vessels, the tibial and the
common peroneal nerves, the termination of the small saphenous vein, the lower
part of the posterior femoral cutaneous nerve, the articular branch from the obtur-
ator nerve, a few small lymph glands, and
a considerable quantity of fat. The tibial
nerve descends through the middle of the
fossa, lyingunder the deep fascia and cross-
ing the vessels posteriorly from the lateral
to the medial side. The common peroneal
nerve descends on the lateral side of the
upper part of the fossa, close to the tendon
of the Biceps femoris. On the floor of the
fossa are the popliteal vessels, the vein
being superficial to the artery and united
to it by dense areolar tissue; the vein is a
thick-walled vessel, and lies at first lateral
to the artery, and then crosses it posteriorly
to gain its medial side below; sometimes
it is double, the artery lying between the
two veins, which are usually connected by
short transverse branches. The articular
branch from the obturator nerve descends
upon the artery to the knee-joint. The
popliteal lymph glands, six or seven in
number, are imbedded in the fat; one lies
beneath the popliteal fascia near' the termi-
nation of the external saphenous vein,
another between the popliteal artery and
the back of the knee-joint, while the others
are placed at the sides of the popliteal
vessel. Arising from the artery, and pass-
ing off from it at right angles, are its genic-
ular branches.
m
-Perf. branch
of fcroneal
, i -x-i 1
"v^'
"^i
'CALCANEUS,
Fig. 551. — The popliteal, posterior tibial, and
peroneal arteries.
The Popliteal Artery (A. Poplitea) (Fig. 551).
The popliteal artery is the continuation of
the femoral, and courses through the poplit-
eal fossa. It extends from the opening in
the Adductor magnus, at the junction of the
middle and lower thirds of the thigh, down-
ward and lateralward to the intercondyloid
fossa of the femur, and then vertically down-
ward to the lower border of the Popliteus,
where it divides into anterior and posterior
tibial arteries.
Relations. — In front of the artery from above
downward are the popliteal surface of the femur
(which is separated from the vessel by some fat),
the back of the knee-joint, and the fascia cover-
ing the Popliteus. Behind, it is overlapped by the
Semimembranosus above, and is covered by the
Gastrocnemius and Plantaris below. In the middle
part of its course the artery is separated from the
integument and fasciae by a quantity of fat, and is
THE POPLITEAL ARTERY 633
crossed from the lateral to the medial side by the tibial nerve and the popliteal vein, the vein
being between the nerve and the artery and closely adherent to the latter. On its lateral side,
above, are the Biceps femoris, the tibial nerve, the popliteal vein, and the lateral condyle of the
femur; below, the Plantaris and the lateral head of the Gastrocnemius. On its medial side, above,
are the Semimembranosus and the medial condyle of the femur; below, the tibial nerve, the
popliteal vein, and the medial head of the Gastrocnemius. The relations of the popliteal lymph
glands to the artery are described above.
Peculiarities in Point of Division.— Occasionally the popliteal artery divides into its terminal
branches opposite the knee-joint. The anterior tibial under these circumstances usually passes
in front of the Popliteus.
Unusual Branches. — The artery sometimes divides into the anterior tibial and peroneal, the
posterior tibial being wanting, or very small. Occasionally it divides into three branches, the
anterior and posterior tibial, and peroneal.
Branches. — The branches of the popliteal artery are:
Muscular j ^^'^'f''' lateral Superior Genicular.
I bural. Middle Genicular.
Cutaneous. Medial Inferior Genicular.
Medial Superior Genicular Lateral Inferior Genicular.
The superior muscular branches, two or three in number, arise from the upper
part of the artery, and are distributed to the lower parts of the Adductor magnus
and hamstring muscles, anastomosing with the terminal part of the profunda
femoris.
The sural arteries {cm. surahs; inferior muscular arteries) are two large branches,
which are distributed to the Gastrocnemius, Soleus, and Plantaris. They arise
from the popliteal artery opposite the knee-joint.
The cutaneous branches arise either from the popliteal artery or from some of
its branches; they descend between the two heads of the Gastrocnemius, and,
piercing the deep fascia, are distributed to the skin of the back of the leg. One
branch usually accompanies the small saphenous vein.
The superior genicular arteries (an. genu superior es; superior articular arteries)
(Figs. 550, 551), two in number, arise one on either side of the popliteal, and wind
around the femur immediately above its condyles to the front of the knee-joint. The
medial superior genicular runs in front of the Semimembranosus and Semitendinosus,
above the medial head of the Gastrocnemius, and passes beneath the tendon of the
Adductor magnus. It divides into two branches, one of which supplies the Vastus
medialis, anastomosing with the highest genicular and medial inferior genicular
arteries; the other ramifies close to the surface of the femur, supplying it and the
knee-joint, and anastomosing with the lateral superior genicular artery. The medial
superior genicular artery is frequently of small size, a condition, which is associated
with an increase in the size of the highest genicular. The lateral superior genicular
passes above the lateral condyle of the femur, beneath the tendon of the Biceps
femoris, and divides into a superficial and a deep branch; the superficial branch
supplies the Vastus lateralis, and anastomoses with the descending branch of the
lateral femoral circumflex and the lateral inferior genicular arteries; the deep
branch supplies the lower part of the femur and knee-joint, and forms an anasto-
motic arch across the front of the bone with the highest genicular and the medial
inferior genicular arteries.
The middle genicular artery (a. genu media; azygos articular artery) is a small
branch, arising opposite the back of the knee-joint. It pierces the oblique popliteal
ligament, and supplies the ligaments and synovial membrane in the interior of
the articulation.
The inferior genicular arteries {aa. genu inferiores; inferior articular arteries) (Figs.
550, 551), two in number, arise from the popliteal beneath the Gastrocnemius. The
medial inferior genicular first descends along the upper margin of the Popliteus, to
which it gives branches; it then passes below the medial condyle of the tibia, beneath
634
ANGIOLOGY
the tibial collateral ligament, at the anterior border of which it ascends to the front
and medial side of the joint, to supply the upper end of the tibia and the articula-
tion of the knee, anastomosing with the lateral inferior and medial superior genic-
ular arteries. The lateral inferior genicular runs lateralward above the head of the
fibula to the front of the knee-joint, passing in its course beneath the lateral head
of the Gastrocnemius, the fibular collateral ligament, and the tendon of the Biceps
femoris. It ends by dividing into branches, which anastomose with the medial
inferior and lateral superior genicular arteries, and with the anterior recurrent
tibial artery.
Descending hranch of
lateral femoral circumflex
Lateral superior genicular
Highest genicular
Musculo-articular hranch oj
highest genicular
Saphenous hranch of highest
genicular
Medial superior genicular
Lateral inferior gemcvlofr
Medial inferior genicular
ff.:^^. w. ■ 'f luiiii'iiim/
Fibular
Anterior recurrent tibial
Anterior tibial
FiQ. 552. — Circumpatellar anastomosis.
The Anastomosis Around the Knee-joint (Fig. 552). — Around and above the patella,
and on the contiguous ends of the femur and tibia, is an intricate net-work of vessels
forming a superficial and a deep plexus. The superficial plexus is situated between
the fascia and skin around about the patella, and forms three well-defined arches:
one, above the upper border of the patella, in the loose connective tissue over the
Quadriceps femoris; the other two, below the level of the patella, are situated in
the fat behind the ligamentum patelhe. The deep plexus, which forms a close
net-work of vessels, lies on the lower end of the femur and upper end of the tibia
around their articular surfaces, and sends numerous offsets into the interior of the
joint. The arteries which form this plexus are the two medial and the two lateral
genicular branches of the popliteal, the highest genicular, the descending branch
of the lateral femoral circumflex, and the anterior recurrent tibial.
The Anterior Tibial Artery (A. Tibialis Anterior) (Fig. 553).
The anterior tibial artery commences at the bifurcation of the popliteal, at the
lower border of the Popliteus, passes forward between the two heads of the Tibialis
THE ANTERIOR TIBIAL ARTERY 635
posterior, and through the aperture above the upper border of the interosseous
membrane, to the deep part of the front of the leg: it here lies close to the medial
side of the neck of the fibula. It then descends on the anterior surface of the inter-
osseous membrane, gradually approaching the tibia; at the lower part of the leg
it lies on this bone, and then on the front of the ankle-joint, where it is more
superficial, and becomes the dorsalis pedis.
Relations. — In the upper two-thirds of its extent, the anterior tibial artery rests upon the inter-
osseous membrane; in the lower third, upon the front of the tibia, and the anterior ligament of
the ankle-joint. In the upper third of its course, it lies between the Tibialis anterior and Extensor
digitorum longus; in the middle third between the Tibiahs anterior and Extensor hallucis longus.
At the ankle it is crossed from the lateral to the medial side by the tendon of the Extensor hallucis
longus, and lies between it and the first tendon of the Extensor digitorum longus. It is covered
in the upper two-thirds of its course, by the muscles which lie on either side of it, and by the deep
fascia; in the lower third, by the integument and fascia, and the transverse and cruciate crural
ligaments.
The anterior tibial artery is accompanied by a pair of venae comitantes which lie one on either
side of the artery; the deep peroneal nerve, coursing around the lateral side of the neck of the
fibula, comes into relation with the lateral side of the artery shortly after it has reached the
front of the leg; about the middle of the leg the nerve is in front of the artery; at the lower part
it is generally again on the lateral side.
Peculiarities in Size. — This vessel may be diminished in size, may be deficient to a greater
or less extent, or may be entirely wanting, its place being supplied by perforating branches from
the posterior tibial, or by the perforating branch of the peroneal artery.
Course. — The artery occasionally deviates toward the fibular side of the leg, regaining its
usual position at the front of the ankle. In rare instances the vessel has been found to approach
the surface in the middle of the leg, being covered merely by the integument and fascia below
that point.
Branches. — The branches of the anterior tibial artery are:
Posterior Tibial Recurrent. ■ Muscular.
Fibular. Anterior Medial Malleolar.
Anterior Tibial Recurrent. Anterior Lateral Malleolar.
The posterior tibial recurrent artery (a. recurrens tibialis posterior) an inconstant
branch, is given off from the anterior tibial before that vessel passes through the
interosseous space. It ascends in front of the Popliteus, which it supplies, and
anastomoses with the inferior genicular branches of the popliteal artery, giving
an offset to the tibiofibular joint.
The fibular artery is sometimes derived from the anterior tibial, sometimes rrom
the posterior tibial. It passes lateralward, around the neck of the fibula, through
the Soleus, which it supplies, and ends in the substance of the Peroneus longus.
The anterior tibial recurrent artery (a. recurrens tibialis anterior) arises from
the anterior tibial, as soon as that vessel has passed through the interosseous
space; it ascends in the Tibialis anterior, ramifies on the front and sides of the
knee-joint, and assists in the formation of the patellar plexus by anastomosing
with the genicular branches of the popliteal, and with the highest genicular artery.
The muscular branches {rami musculares) are numerous; they are distributed to
the muscles which lie on either side of the vessel, some piercing the deep fascia to
supply the integument, others passing tlirough the interosseous membrane, and
anastomosing with branches of the posterior tibial and peroneal arteries.
The anterior medial malleolar artery (a. malleolaris anterior medialis; internal
malleolar artery) arises about 5 cm. above the ankle-joint, and passes behind the
tendons of the Extensor hallucis longus and Tibialis anterior, to the medial side of
the ankle, upon which it ramifies, anastomosing with branches of the posterior tibial
and medial plantar arteries and with the medial calcaneal from the posterior tibial.
The anteriot lateral malleolar artery (a. malleolaris anterior lateralis; exter-
nal malleolar artery) passes beneath the tendons of the Extensor digitorum
636
ANGIOLOGY
Lateral
inferior .
genicular
'i v;
Medial
■ inferior
genicular
Anterior
tibial
recurrent
i .V
longus and Peronseus tertius and supplies the lateral side of the ankle, anas-
tomosing with the perforating branch of the peroneal artery, and with ascend-
ing twigs from the lateral tarsal artery.
The arteries around the ankle-joint
anastomose freely with one another
and form net-works below the corre-
sponding malleoli. The medial malleolar
net-work is formed by the anterior
medial malleolar branch of the anterior
tibial, the medial tarsal branches of
the dorsalis pedis, the posterior medial
malleolar and medial calcaneal branches
of the posterior tibial and branches
from the medial plantar artery. The
lateral malleolar net-work is formed by
the anterior lateral malleolar branch of
the anterior tibial, the lateral tarsal
branch of the dorsalis pedis, the per-
forating and the lateral calcaneal
branches of the peroneal, and twigs
from the lateral plantar artery.
The Arteria Dorsalis Pedis (Dorsalis
Pedis Artery) (Fig. 553).
The arteria dorsalis pedis, the contin-
uation of the anterior tibial, passes for-
ward from the ankle-joint along the
tibial side of the dorsum of the foot to
the proximal part of the first inter-
metatarsal space, where it divides into
two branches, the first dorsal metatarsal
and the deep plantar.
Relations. — This vessel, in its course for-
ward, rests upon the front of the articular
capsule of the ankle-joint, the talus, navic-
ular, and second cuneiform bones, and the
ligaments connecting them, being covered by
the integument, fascia and cruciate ligament,
and crossed near its termination by the first
tendon of the Extensor digitorum brevis. On
its tibial side is the tendon of the Extensor
hallucis longus; on its fibular side, the first
tendon of the Extensor digitorum longus,
and the termination of the deep peroneal
nerve. It is accompanied by two veins.
. Peculiarities in Size. — The dorsal artery of
the foot may be larger than usual, to com-
pensate for a deficient plantar artery; or its
terminal branches to the toes may be absent,
the toes then being supplied by the medial
plantar; or its place may be taken altogether
by a large perforating branch of the peroneal
artery.
Position. — This artery frequently curves
lateral ward, lying lateral to .the line between
the middle of the ankle and the back part of
the first interosseous space.
Perf. hr. of _
'peroneal
Ant. lat. _
Tnalleolar
Ant. med.
malleolar
r/
^rfitate
Deep
plantar
Fia. 553. — .interior tibial and dorsalis pedis arteries.
THE POSTERIOR TIBIAL ARTERY 637
Branches. — The branches of the arteria dorsahs pedis are:
Lateral Tarsal. Arcuate.
Medial Tarsal. First Dorsal Metatarsal.
Deep Plantar.
The lateral tarsal artery (a. tarsea lateralis ; tarsal artery) arises from the dorsalis
pedis, as that vessel crosses the navicular bone; it passes in an arched direction
lateralward, lying upon the tarsal bones, and covered by the Extensor digitorum
brevis; it supplies this muscle and the articulations of the tarsus, and anastomoses
with branches of the arcuate, anterior lateral malleolar and lateral plantar arteries,
and with the perforating branch of the peroneal artery.
The medial tarsal arteries {aa. tarsea; mediales) are two or three small branches
which ramify on the medial borderof the foot and join the medial malleolar net-work.
The arcuate artery (a. arcuata; metatarsal artery) arises a little anterior to the
lateral tarsal artery; it passes lateralward, over the bases of the metatarsal bones,
beneath the tendons of the Extensor digitorum brevis, its direction being influenced
by its point of origin; and it anastomoses with the lateral tarsal and lateral plantar
arteries. This vessel gives off the second, third, and fourth dorsal metatarsal arteries,
which run forward upon the corresponding Interossei dorsales; in the clefts between
the toes, each divides into two dorsal digital branches for the adjoining toes. At
the proximal parts of the interosseous spaces these vessels receive the posterior
perforating branches from the plantar arch, and at the distal parts of the spaces
they are joined by the anterior perforating branches, from the plantar metatarsal
arteries. The fourth dorsal metatarsal artery gives off a branch which supplies
the lateral side of the fifth toe.
The first dorsal metatarsal artery (a. dorsalis hallucis) runs forward on the first
Interosseous dorsalis, and at the cleft between the first and second toes divides
into two branches, one of which passes beneath the tendon of the Extensor hallucis
longus, and is distributed to the medial border of the great toe; the other bifurcates
to supply the adjoining sides of the great and second toes.
The deep plantar artery (ramus planturis profundus; communicating artery)
descends into the sole of the foot, between the two heads of the first Interosseous
dorsalis, and unites with the termination of the lateral plantar artery, to complete
the plantar arch. It sends a branch along the medial side of the great toe, and is
continued forward along the first interosseous space as the first plantar metatarsal
artery, which bifurcates for the supply of the adjacent sides of the great and second
toes.
The Posterior Tibial Artery (A. Tibialis Posterior) (Fig. 551).
The posterior tibial artery begins at the lower border of the Popliteus, opposite
the interval between the tibia and fibula; it extends obliquely downward, and, as
it descends, it approaches the tibial side of the leg, lying behind the tibia, and in
the lower part of its course is situated midway between the medial malleolus and
the medial process of the calcaneal tuberosity. Here it divides beneath the origin
of the Adductor hallucis into the medial and lateral plantar arteries.
Relations. — The posterior tibial artery lies successively upon the Tibialis posterior, the Flexor
digitorum longus, the tibia, and the back of the ankle-joint. It is covered by the deep trans-
verse fascia of the leg, which separates it above from the Gastrocnemius and Soleus; at its termi-
nation it is covered by the Abductor hallucis. In the lower third of the leg, where it is more
superficial, it is covered only by the integument and fascia, and runs parallel with the medial
border of the tendo calcaneus. It is accompanied by two veins, and by the tibial nerve, which
lies at first to the medial side of the artery, but soon crosses it posteriorly, and is in the greater
part of its course on its lateral side.
Behind the medial malleolus, the tendons, bloodvessels, and nerve are arranged, under cover
of the laciniate ligament, in the following order from the medial to the lateral side: (1) the
638 ANGIQLOGY
tendons of the Tibialis posterior and Flexor digitorum longus, lying in the same groove, behind
the malleolus, the former being the more medial. Next is the posterior tibial artery, with a vein
on either side of it; and lateral to the vessels is the tibial nerve; about 1.25 cm. nearer the heel
is the tendon of the Flexor hallucis longus.
Peculiarities in Size. — The posterior tibial is not infrequenth' smaller than usual, or absent,
its place being supplied by a large peroneal artery, which either joins the small posterior tibial
artery, or continues alone to the sole of the foot.
Branches, — The branches of the posterior tibial artery are:
Peroneal. Posterior ^ledial ^Malleolar.
Nutrient. Communicating.
Muscular. Medial Calcaneal.
The peroneal artery (o. peroncpa) is deeply seated on the back of the fibular
side of the leg. It arises from the posterior tibial, about 2.5 cm. below the lower
border of the Popliteus, passes obliquely toward the fibula, and then descends
along the medial side of that bone, contained in a fibrous canal between the Tibialis
posterior and the Flexor hallucis longus, or in the substance of the latter muscle.
It then runs behind the tibiofibular syndesmosis and divides into lateral calcaneal
branches which ramify on the lateral and posterior surfaces of the calcaneus.
It is covered, in the upper part of its course, by the Soleus and deep transverse
fascia of the leg; helow, by the Flexor hallucis longus.
Peculiarities in Origin. — The peroneal artery may arise 7 or 8 cm. below the Popliteus, or from
the posterior tibial high up, or even from the popliteal.
Its size is more frequently increased than diminished; and then it either reinforces the posterior
tibial by its junction with it, or altogether takes the place of the posterior tibial in the lower
part of the leg and foot, the latter vessel only existing as a short muscular branch. In those
rare cases where the peroneal artery is smaller than usual, a branch from the posterior tibial
supplies its place; and a branch from the anterior tibial compensates for the diminished anterior
peroneal artery. In one case the peroneal artery was entirely wanting.
Branches. — The branches of the peroneal are:
^luscular. Perforating.
Nutrient. Communicating.
Lateral Calcaneal.
Muscular Branches. — The peroneal artery, in- its course, gives off branches to
the Soleus, Tibialis posterior. Flexor hallucis longus, and Peronei.
The Nutrient Artery (a. nutricia fihulcc) supplies the fibula, and is directed
downward.
The Perforating Branch {ramus perforans; anterior peroneal artery) pierces the
interosseous membrane, about 5 cm. above the lateral malleolus, to reach the front
of the leg, where it anastomoses with the anterior lateral malleolar; it then passes
down in front of the tibiofibular syndesmosis, gives branches to the tarsus, and
anastomoses with the lateral tarsal. The perforating branch is sometimes enlarged,
and takes the place of the dorsalis pedis artery.
The Communicating Branch (ramus covimunicans) is given oft" from the peroneal
about 2.5 cm. from its lower end, and joins the communicating branch of the
posterior tibial.
The Lateral Calcaneal {ramus calcaneus lateralis; external calcaneal) are the ter-
minal branches of the peroneal artery; they pass to the lateral side of the heel,
and communicate with the lateral malleolar and, on the back of the heel, with the
medial calcaneal arteries.
The nutrient artery (a. nutricia tibicp) of the tibia arises from the posterior
tibial, near its origin, and after supplying a few muscular branches enters the
nutrient canal of the bone, which it traverses obliquely from above downward.
This is the largest nutrient artery of bone in the body.
THE POSTERIOR TIBIAL ARTERY
639
The muscular branches of the posterior tibial are distributed to the Soleus and
deep muscles along the back of the leg.
The posterior medial malleolar artery (o. malleohris posterior medialis; iniernal
malleolar artery) is a small branch which winds around the tibial malleolus and
ends in the medial malleolar net-work.
The communicating branch {ramus communicans) runs transversely across the
back of the til)ia, about 5 cm. above its lower end, beneath the Flexor hallucis
longus, and joins the communicating branch of the peroneal.
The medial calcaneal {rami calcanei mediales; internal calcaneal) are several
large arteries which arise from the posterior tibial just before its division; they
pierce the laciniate ligament and are distributed to the fat and integument behind
the tendo calcaneus and about the heel, and to the muscles on the tibial side of
the sole, anastomosing with the peroneal and medial malleolar and, on the back
of the heel, with the lateral calcaneal arteries.
Deep -plantar
\st plantar
metatarsal
Fig. 554. — The plantar arteries. Superficial view.
Fig. 555. — The plantar arteries. Deep view.
The medial plantar artery («. pkuttaris medialis; internal plantar artery) (Figs.
554 and 555), much smaller than the lateral, passes forward along the medial side
of the foot. It is at first situated above the Abductor hallucis, and then between
it and the Flexor digitorum brevis, both of which it supplies. At the base of the
first metatarsal bone, where it is much diminished in size, it passes along the medial
border of the first toe, anastomosing with the first dorsal metatarsal artery-. Small
superficial digital branches accompany the digital branches of the medial plantar
nerve and join the plantar metatarsal arteries of the first three spaces.
The lateral plantar artery (a. plantaris lateralis; external plantar artery), much
larger than the medial, passes obliquely lateralward and forward to the base of
the fifth metatarsal bone. It then turns medialward to the interval between the
bases of the first and second metatarsal bones, where it unites with the deep plantar
branch of the dorsalis pedis artery, thus completing the plantar arch. As this artery
passes lateralward, it is first placed between the calcaneus and Abductor hallucis,
640 ANGIOLOGY
and then between the Flexor digitorum brevis and Quadratus planf?e; as it runs
forward to the base of the little toe it lies more superficially between the Flexor
digitorum brevis and Abductor digiti quinti, covered by the plantar aponeurosis
and integument. The remaining portion of the vessel is deeply situated; it extends
from the base of the fifth metatarsal bone to the proximal part of the first imer-
osseous space, and forms the plantar arch; it is convex forward, lies below the bases
of the second, third, and fourth metatarsal bones and the corresponding Interossei,
and upon the oblique part of the Adductor hallucis.
Branches. — The plantar arch, besides distributing numerous branches to the
muscles, integument, and fasciae in the sole, gives off the following branches:
Perforating. Plantar Metatarsal.
The Perforating Branches {rami perforanies) are three in number; they ascend
through the proximal parts of the second, third, and fourth interosseous spaces,
between the heads of the Interossei dorsales, and anastomose with the dorsal
metatarsal arteries.
The Plantar Metatarsal Arteries {aa. metatarsece plantares; digital branches) are
four in number, and run forward between the metatarsal bones and in contact
with the Interossei. Each divides into a pair of plantar digital arteries which sup-
ply the adjacent sides of the toes. Near their points of division each sends upward
an anterior perforating branch to join the corresponding dorsal metatarsal artery.
The first plantar metatarsal artery {artcria princeps hallucis) springs from the junc-
tion between the lateral plantar and deep plantar arteries and sends a digital
branch to the medial side of the first toe. The digital branch for the lateral side
of the fifth toe arise from the lateral plantar artery near the base of the fifth
metatarsal bone.
BIBLIOGRAPHY.
Bean, R. B.: A Composite Study of the Subcla^^an Artery in Man, Am. Jour. .\nat., 1905. iv.
Bremer, J. L. : On the Origin of the Renal Artery in Mammals and its Anomalies, Am. Jour.
Anat., 1915, x\'iii.
Brojiax, Ivar: Ueber die Entwickelung " Wanderung, " und Variation der Bauchaortenzweige
bei den Wirbeltieren, Ergebnisse der Anat. u. Entwick., 1906, xvi.
E.\Tox, P. B.: The Celiac Axis, Anat. Rec, 1917, -xiii.
Hexle, J.: Anatomie des Menschen.
HiTZROT, J. M.: A Composite Study of the .\xillary Artery in Man, Johns Hop. Hosp. Bull.,
1901, xii.
LiPSHCTZ, B. B.: Studies on the Blood Vascular Tree. I. A Composite Stud}- of the Femoral
.\rtery, Anat. Rec, 191G, x.
Poirier ct Charpy: Traite d'Anatomie Humaine.
Quain's Anatomy.
THE VEINS.
THE Veins convey the blood from the capillaries of the different parts of the
body to the heart. They consist of two distinct sets of vessels, the pulmonary
and systemic.
The Puhnonary Veins, unlike other veins, contain arterial blood, which they return
from the luno;s to the left atrium of the heart.
The Systemic Veins return the venous blood from the body generally to the
right atrium of the heart.
The Portal Vein, an appendage to the systemic venous system, is confined to
the abdominal cavity, and returns the venous blood from the spleen and the viscera
of digestion to the; liver. This vessel ramifies in the substance of the liver and there
breaks up into a minute network of capillary-like vessels, from which the blood
is conveyed by the hepatic veins to the inferior vena cava.
The veins commence by minute plexuses which receive the blood from the capil-
laries. The branches arising from these plexuses unite together into trunks, and
these, in their passage toward the heart, constantly increase in size as they receive
tributaries, or join other veins. The veins are larger and altogether more numerous
than the arteries; hence, the entire capacity of the venous system is much greater
than that of the arterial; the capacity of the pulmonary veins, however, only
slightly exceeds that of the pulmonary arteries. The veins are cylindrical like the
arteries; their walls, however, are thin and they collapse when the vessels are
empty, and the uniformity of their surfaces is interrupted at intervals by slight
constrictions, which indicate the existence of valves in their interior. They com-
municate \ery freely with one another, especially in certain regions of the body;
and these communications exist between the larger trunks as well as between the
smaller branches. Thus, between the venous sinuses of the cranium, and between
the veins of the neck, where obstruction would be attended with imminent danger
to the cerebral venous system, large and frequent anastomoses are found. The
same free communication exists between the veins throughout the whole extent
of the vertebral canal, and between the veins composing the various venous plexuses
in the abdomen and pelvis, e. r/., the spermatic, uterine, vesical, and pudendal.
The systemic venous channels are subdivided into three sets, viz., superficial
and deep veins, and venous sinuses.
The Superficial Veins [cutaneous veins) are found between the layers of the
superficial fascia immediately beneath the skin; they return the blood from these
structures, and communicate with the deep veins by perforating the deep fascia.
The Deep Veins accompany the arteries, and are usually enclosed in the same
sheaths with those vessels. With the smaller arteries — as the radial, ulnar, brachial,
tibial, peroneal — they exist generally in pairs, one lying on each side of the vessel,
and are called venae comitantes. The larger arteries — such as the axillary, sub-
clavian, popliteal, and femoral — have usually only one accompanying vein. In
certain organs of the body, however, the deep veins do not accompany the arteries;
for instance, the veins in the skull and vertebral canal, the hepatic veins jji the liver,
and the larger veins returning blood from the bones.
Venous Sinuses are found only in the interior of the skull, and consist of canals
formed by a separation of the two layers of the dura mater; their outer coat con-
sists of fibrous tissue, their inner of an endothelial layer continuous with the lining
membrane of the veins.
41 (641)
642 ANGIOLOGY
THE PULMONARY VEINS (VEN^ PULMONALES).
The pulmonary veins return the arteriahzed blood from the lungs to the left
atrium of the heart. They are four in number, two from each lung, and are desti-
tute of valves. The commence in a capillary net-work upon the walls of the air sacs,
where they are continuous with the capillary ramifications of the pulmonary artery,
and, joining together, form one vessel for each lobule. These vessels uniting
successively, form a single trunk for each lobe, three for the right, and two for
the left lung. The vein from the middle lobe of the right lung generally unites
with that from the upper lobe, so that ultimately two trunks from each lung are
formed; they perforate the fibrous layer of the pericardium and open separately
into the upper and back part of the left atrium. Occasionally the three veins
on the right side remain separate. Not infrequently the two left pulmonary
veins end by a common opening.
At the root of the lung, the superior pulmonary vein lies in front of and a little
below the pulmonary artery; the inferior is situated at the lowest part of the hilus
of the lung and on a plane posterior to the upper vein. Behind the pulmonary
artery is the bronchus.
Within the pericardium, their anterior surfaces are invested by the serous layer
of this membrane.
The right pulmonary veins pass behind the right atrium and superior vena cava;
the left in front of the descending thoracic aorta.
THE SYSTEMIC VEINS.
The systemic veins may be arranged into three groups : ( 1 ) The veins of the hearts
(2) The veins of the upper extremities, head, neck, and thorax, which end in the
superior vena cava. (3) The veins of the lower extremities, abdomen, and pelvis,
which end in the inferior vena cava.
THE VEINS OF THE HEART (VV. Cordis) (Fig. 556).
Coronary Sinus (sinus coronarius). — jVIost of the veins of the heart open into
the coronary sinus. This is a wide venous channel about 2.25 cm. in length
situated in the posterior part of the coronary sulcus, and covered by muscular
fibers from the left atrium. It ends in the right atrium between the opening of
the inferior vena cava and the atrioventricular aperture, its orifice being guarded
by a semilunar valve, the valve of the coronary sinus {valve of Thehesius).
Tributaries. — Its tributaries are the great, small, and middle cardiac veins, the
posterior vein of the left ventricle, and the oblique vein of the left atrium, all of
which, except the last, are provided with valves at their orifices.
1. The Great Cardiac Vein {v. cordis magna; left coronary vein) begins at the apex
of the heart and ascends along the anterior longitudinal sulcus to the base of the
ventricles. It then curves to the left in the coronary sulcus, and reaching the
back of the heart, opens into the left extremity of the coronary sinus. It receives
tributaries from the left atrium and from both ventricles: one, the left marginal
vein, is of considerable size, and ascends along the left margin of the heart.
2. The Small Cardiac Vein {v. cordis parva; right coronary vein) runs in the coronary
sulcus between the right atrium and ventricle, and opens into the right extremity
of the coronary sinus. It receives blood from the back of the right atrium and
ventricle; the right marginal vein ascends along the right margin of the heart and
joins it in the coronary sulcus, or opens directly into the right atrium.
THE VEINS OF THE HEAD AND NECK
643
3. The Middle Cardiac Vein {v. cordis media) commences at the apex of the heart,
ascends in the posterior longitudinal sulcus, and ends in the coronary sinus near
its right extremity.
4. The Posterior Vein of the Left Ventricle (v. posterior ventriadi sinvitri) runs on
the diaphragmatic surface of the left \entricle to the coronary sinus, but may end
in the great cardiac vein.
5. The ObUque Vein of the Left Atrium {v. ohliqua atrii sinistri [Marshalli]; oblique
vein of Marshall) h a small vessel which descends obliquely on the back of the left
atrium and ends in the coronary sinus near its left extremity; it is continuous above
with the ligament of the left vena cava {Ug. venoe cavoe sinistroe; vestigial fold of
Marshall), and the two structures form the remnant of the left Cuvierian duct.
Azygos vein
Left pulmonnry veins
Oblique vein of left atrium
Great cardiac vein
Left marginal vein
Rigid pulmonary
veins
Small cardiac vein
Posterior vein of left ventricle
Middle cardiac vein
FiQ. 556. — Base and diaphragmatic surface of heart.
The following cardiac veins do not end in the coronary sinus: (1) the anterior
cardiac veins, comprising three or four small vessels which collect blood from the
front of the right ventricle and open into the right atrium; the right marginal vein
frequently opens into the right atrium, and is therefore sometimes regarded as
belonging to this group; (2) the smallest cardiac veins {veins of Thebesius), con-
sisting of a number of minute veins which arise in the muscular wall of the heart;
the majority open into the atria, but a few end in the ventricles.
THE VEINS OF THE HEAD AND NECK.
The veins of the head and neck may be subdivided into three groups: (1) The
veins of the exterior of the head and face. (2) The veins of the neck. (3) The diploic
veins, the veins of the brain, and the venous sinuses of the dura mater.
644
ANGIOLOGY
The Veins of the Exterior of the Head and Face (Fig. 557).
The veins of the exterior of the head and face are:
Frontal.
Supraorbital.
Angular.
Anterior Facial.
Occipital.
Superficial Temporal
Internal ^Maxillary.
Posterior Facial.
Posterior Auricular.
Frontal
Communicating branch
with ophthalmic vein
Angxdar
Lingual
Pharynfjcal
Superior thyroid
Fig. 557. — Veins of the liead and neck.
The frontal vein (v. froninJis) begins on the forehead in a venous plexus which
communicates with the frontal branches of the superficial temporal vein. The
veins converge to form a single trunk, which runs downward near the middle line
of the forehead parallel with the vein of the opposite side. The two veins are joined,
at the root of the nose, by a transverse branch, called the nasal arch, which receives
some small veins from the dorsum of the nose. At the root of the nose the veins
diverge, and, each at the medial angle of the orbit, joins the supraorbital vein, to
THE VEINS OF THE EXTERIOR OF THE HEAD AND FACE 645
form the angular vein. Occasionally the frontal veins join to form a single trunk,
which bifurcates at the root of the nose into the two angular veins.
The supraorbital vein (v. supraorhitaHs) begins on the forehead where* it com-
municates with the frontal branch of the superficial temporal vein. It runs down-
ward superficial to the Frontalis muscle, and joins the frontal vein at the medial
angle of the orbit to form the angular vein. Previous to its junction with the frontal
vein, it sends through the supraorbital notch into the orbit a branch which com-
municates with the ophthalmic vein; as this vessel passes through the notch, it
receives the frontal diploic vein through a foramen at the bottom of the notch.
The angular vein {v. angnlaris) formed by the junction of the frontal and supra-
orbital veins, runs obliquely downward, on the side of the root of the nose, to the
level of the lower margin of the orbit, where it becomes the anterior facial vein.
It receives the veins of the ala nasi, and communicates with the superior ophthalmic
vein through the nasofrontal vein, thus establishing an important anastomosis
between the anterior facial vein and the cavernous sinus.
The anterior facial vein (v. facialis anterior; facial vein) commences at the side
of the root of the nose, and is a direct continuation of the angular vein. It lies
behind the external maxillary (facial) artery and follows a less tortuous course.
It runs obliquely downward and backward, beneath the Zygomaticus and zygo-
matic head of the Quadratus labii superioris, descends along the anterior border
and then on the superficial surface of the Masseter, crosses over the body of the
mandible, and passes obliquely backward, beneath the Platysma and cervical
fascia, superficial to the submaxillary gland, the Digastricus and Stylohyoideus.
It unites with the posterior facial vein to form the common facial vein, which
crosses the external carotid artery and enters the internal jugular vein at a vari-
able point below the hyoid bone. From near its termination a communicating
branch often runs down the anterior border of the Sternocleidomastoideus to join
the lower part of the anterior jugular vein. The facial vein has no valves, and its
walls are not so flaccid as most superficikl veins.
Tributaries. — The anterior facial vein receives a branch of considerable size,
the deep facial vein, from the pterygoid venous plexus. It is also joined by the
superior and inferior palpebral, the superior and inferior labial, the buccinator
and the masseteric veins. Below the mandible it receives the submental, palatine,
and submaxillary veins, and, generally, the vena comitans of the hypoglossal nerve.
The superficial temporal vein {v. temporalis superficialis) begins on the side and
vertex of the skull in a plexus which communicates with the frontal and supra-
orbital veins, with the corresponding vein of the opposite side, and with the pos-
terior auricular and occipital veins. From this net-work frontal and parietal branches
arise, and unite above the zygomatic arch to form the trunk of the vein, which is
joined in this situation by the middle temporal vein, from the substance of the Tem-
poralis. It then crosses the posterior root of the zygomatic arch, enters the sub-
stance of the parotid gland, and unites with the internal maxillary vein to form the
posterior facial vein.
Tributaries. — The superficial temporal vein receives in its course some parotid
veins, articular veins from the temporomandibular joint, anterior auricular veins
from the auricula, and the transverse facial from the side of the face. The middle
temporal vein receives the orbital vein, which is formed by some lateral palpebral
branches, and passes backward between the layers of the temporal fascia to join
the superficial temporal vein.
The pterygoid plexus (plexus pterygoideus) is of considerable size, and is situated
between the Temporalis and Pterygoideus externus, and partly between the two
Pterygoidei. It receives tributaries corresponding with the branches of the internal
maxillary artery. Thus it receives the sphenopalatine, the middle meningeal, the
•deep temporal, the pterygoid, masseteric, buccinator, alveolar, and some palatine
646 ANGIOLOGY
veins, and a branch which communicates with the ophthalmic vein through the
inferior orbital fissure. This plexus communicates freely with the anterior facial
vein; it also communicates with the cavernous sinus, by branches through the
foramen Vesalii, foramen ovale, and foramen lacerum.
The internal maxillary vein (r. maxillaris interna) is a short trunk which accom-
panics the first part of the internal maxillary artery. It is formed by a confluence
of the veins of the pterygoid plexus, and passes backward between the spheno-
mandibular ligament and the neck of the mandible, and unites with the temporal
vein to form the posterior facial vein.
The posterior facial vein (v. facialis posterior; temporomaxillary vein), formed
by the union of the superficial temporal and internal maxillary veins, descends in
the substance of the parotid gland, superficial to the external carotid artery but
beneath the facial nerve, between the ramus of the mandible and the Sternocleido-
mastoideus muscle. It divides into two branches, an anterior, which passes forward
and unites with the anterior facial vein to form the common facial vein and a pos-
terior, which is joined by the posterior auricular vein and becomes the external
jugular vein.
The posterior auricular vein (v. aiiricidaris posterior) begins upon the side of
the head, in a plexus which communicates with the tributaries of the occipital,
and superficial temporal veins. It descends behind the auricula, and joins the
posterior division of the posterior facial vein to form the external jugular. It
receive the stylomastoid vein, and some tributaries from the cranial surface of the
auricula.
The occipital vein (v. occipitalis) begins in a plexus at the back part of the vertex
of the skull, From the plexus emerges a single vessel, which pierces the cranial
attachment of the Trapezius and, dipping into the suboccipital triangle, joins the
deep cervical and vertebral veins. Occasionally it follows the course of the occipital
artery and ends in the internal jugular; in other instances, it joins the posterior
auricular and through it opens into the external jugular. The parietal emissary
vein connects it with the superior sagittal sinus; and as it passes across the mastoid
portion of the temporal bone, it receives the mastoid emissary vein which connects
it with the transverse sinus. The occipital diploic vein sometimes joins it.
The Veins of the Neck (Fig. 558).
The veins of the neck, which return the blood from the head and face, are:
External Jugular. Anterior Jugular.
Posterior External Jugular. Internal Jugular.
Vertebral.
The external jugular vein (v. jugularis externa) receives the greater part of the
blood from the exterior of the cranium and the deep parts of the face, being formed
by the junction of the posterior division of the posterior facial with the posterior
auricular vein. It commences in the substance of the parotid gland, on a level
with the angle of the mandible, and runs perpendicularly down the neck, in the
direction of a line drawn from the angle of the mandible to the middle of the clavicle
at the posterior border of the Sternocleidomastoideus. In its course it crosses
the Sternocleidomastoideus obliquely, and in the subclavian triangle perforates
the deep fascia, and ends in the subclavian vein, lateral to or in front of the Scalenus
anterior. It is separated from the Sternocleidomastoideus by the investing layer
of the deep cervical fascia, and is covered by the Platysma, the. superficial fascia,
and the integument; it crosses the cutaneous cervical nerve, and its upper half
runs parallel with the great auricular nerve. The external jugular vein varies in
size, bearing an inverse proportion to the other veins of the neck, it is occasionally
THE VEINS OF THE NECK
647
double. It is provided with two pairs of valves, the lower pair being placed at
its entrance into the subclavian vein, the upper in most cases about 4 cm. above the
clavicle. The portion of vein between the two sets of valves is often dilated, and
is termed the sinus._ These valves do not prevent the regurgitation of the blood,
or the passage of injection from below upward.
Tributaries.— This vein receives the occipital occasionally, the posterior external
jugular, and, near its termination, the transverse cervical, transverse scapular, and
anterior jugular veins; in the substance of the parotid, a large branch of commu-
nication from the internal jugular joins it.
Fig. 558.-
Suhclavian rein
-The veins of the neck, viewed from in front.
(Spalteholz )
The posterior external jugular vein (v. jugidaris posterior) begins in the occipital
region and returns the blood from the skin and superficial muscles in the upper and
back part of the neck, lying between the Splenius and Trapezius. It runs down
the back part of the neck, and opens into the external jugular vein just below the
middle of its course.
The anterior jugular vein {r. jugidaris anterior) begins near the hyoid bone by
the confluence of several superficial veins from the submaxillary region. It descends
between the median line and the anterior border of the Sternocleidomastoideus,
and, at the lower part of the neck, passes beneath that muscle to open into the ter-
mination of the external jugular, or, in some instances, into the subclavian vein
(Figs. 557, 558). It varies considerably in size, bearing usually an inverse propor-
648
ANGIOLOGY
tion to the external jugular; most frequently there are two anterior jugulars, a
right and left; but sometimes only one. Its tributaries are some laryngeal veins,
and occasionally a small thyroid vein. Just above the sternum the two anterior
jugular veins communicate by a transverse trunk, the venous jugular arch, which
receive tributaries from the inferior thyroid veins; each also communicates with the
internal jugular. There are no valves in this vein.
The internal jugular vein (v. jngxdaris interna) collects the blood from the brain,
from the superficial parts of the face, and from the neck. It is directly continuous
with the transverse sinus, and begins in the posterior compartment of the jugular
foramen, at the base of the skull. At its origin it is somewhat dilated, and this
dilatation is called the superior bulb. It runs down the side of the neck in a vertical
direction, lying at first lateral to the internal carotid artery, and then lateral
to the common carotid, and at the root of the neck unites with the subclavian vein
to form the innominate vein; a little above its termination is a second dilatation,
the inferior bulb. Above, it lies upon the Rectus capitis lateralis, behind the internal
carotid artery and the nerves passing through the jugular foramen; lower down,
the vein and artery lie upon the same plane, the glossopharyngeal and hypoglossal
nerves passing forward between them; the vagus descends between and behind
the vein and the artery in the same sheath, and the accessory runs obliquely
backward, superficial or deep to the vein. At the root of the neck the right internal
jugular vein is placed at a little distance from the common carotid artery, and
DORSALIS
LINGUA ARTEBV
LINGUAL VEIN
VEINS OF
DORSUM OF
TONGUE
HYPOGLOSSAL NERVE
Fig. 559. — Veins of the tongue.
The hypoglossal ners^e has been displaced downward in this preparation.
(Testut after Hirschfeld.)
crosses the first part of the subclavian artery, while the left internal jugular vein
usually overlaps the common carotid artery. The left vein is generally smaller
than the right, and each contains a pair of valves, which are placed about 2.5 cm.
above the termination of the vessel.
Tributaries. — This vein receives in its course the inferior petrosal sinus, the common
facial, lingual, pharyngeal, superior and middle thyroid veins, and sometimes the
occipital. The thoracic duct on the left side and the right lymphatic duct on the
right side open into the angle of union of the internal jugular and subclavian veins.
The Inferior Petrosal Sinus {sinus yetrosus inferior) leaves the skull through the
anterior part of the jugular foramen, and joins the superior bulb of the internal
jugular vein.
The Lingual Veins (to. linguales) begin on the dorsum, sides, and under surface
of the tongue, and, passing backward along the course of the lingual artery, end
in the internal jugular vein. The vena comitans of the hypoglossal nerve (ranine
THE VEINS OF THE NECK
649
vein), a branch of considerable size, begins below the tip of the tongue, and may
join the lingual; generally, however, it passes backward on the Hyoglossus, and
joins the common facial.
The Pharyngeal Veins (tv. pharyngeiv) l)fqin in the pharyngeal plexus on the outer
surface of the pharynx, and, after recei\ing some posterit)r meningeal veins and the
vein of the pterygoid canal, end in the internal jugular. They occasionally open
into the facial, lingual, or superior thyroid vein.
The Superior Thyroid Vein (i\ thyreoidea superioris) (Fig. 560) hegim in the sub-
stance and on the surface of the thyroid gland, by tributaries corresponding with
the branches of the superior thyroid artery, and ends in the upper part of the
internal jugular vein. It receives the superior laryngeal and cricothyroid veins.
The Middle Thyroid Vein (Figs. 561 , 562) collects the blood from the lower part
of the thyroid gland, and after being joined by some veins from the larynx and
trachea, ends in the lower part of the internal jugular vein.
The common facial and occipital veins have been described.
'!vri!d"'bhnr ^
Yagus nerve
External carotid artery
Superior thyroid artery
Superior thyroid vein
Middle thyroid vein
-6t'>
Fia. 560. — The veins of the thyroid gland.
The vertebral vein {v. vertehralis) is formed in the suboccipital triangle, from
numerous small tributaries which spring from the internal vertebral venous plexuses
and issue from the vertebral canal above the posterior arch of the atlas. The\'
unite with small ^■eins from the deep muscles at the upper part of the back of
the neck, and form a vessel which enters the foramen in the transverse process
of the atlas, and descends, forming a dense plexus around the vertebral artery,
in the canal formed by the foramina transversaria of the cervical vertebrae. This
plexus ends in a single trunk, which emerges from the foramen transversarium of
the sixth cervical vertebra, and opens at the root of the neck into the back part
of the innominate vein near its origin, its mouth being guarded by a pair of valves.
On the right side, it crosses the first part of the subclavian artery.
650
ANGIOLOGY
Tributaries. — The vertebral vein communicates with the transverse smus by
a vein which passes through the condyloid canal, when that canal exists. It
Fig. 561. — Diagram showing common arrangement of thyroid veins. (Kocher.)
SUPERIOR
THYROID
ARTERY
CRICO-
THYROID
MUSCLE
MIDDLE
THYROID
VEIN
INTERIOR
THYROID
VEIN
STERNO-
THYROID
MUSCLE
INFERIOR
THYROID
VEIN
Fig 5G2.— The fascia and middle thyroid veins. The veins here designated the
Kocher the thyroidea ima. (Poiricr and Charpy
inferior thyroid are called by
receives branches from the occipital vein and from the prevertebral muscles, froni
the internal and external vertebral venous plexuses, from the anterior vertebral
THE DIPLOIC VEINS
651
and the deep cervical veins; close to its termination it is sometimes joined by the
first intercostal vein.
The Anterior Vertebral Vein commences in a plexus around the transverse pro-
cesses of the upper cervical vertebrae, descends in company with the ascending
cervical artery between the Scalenus anterior and Longus capitis muscles, and
opens into the terminal part of the vertebral vein.
VERTEBRAL-
VERTEBRAL
POSTEHIO
ASCENDING
CERVICAL
Fig. 503. — The vertebral vein. (Poirier and Charpy.)
The Deep Cervical Vein {v. cervicalis profunda; yosterior -vertebral or posterior
deep cervical vein) accompanies its artery between the Semispinals capitis and
colli. It begins in the suboccipital region by communicating branches from the
occipital vein and by small veins from the deep muscles at the back of the neck.
It receives tributaries from the plexuses around the spinous processes of the cer-
vical vertebrae, and terminates in the lower part of the vertebral vein.
The Diploic Veins (Ven« Diploicse) (Fig. 564).
The diploic veins occupy channels in the diploe of the cranial bones. They are
large and exhibit at irregular intervals pouch-like dilatations; their walls are thin,
and formed of endothelium resting upon a layer of elastic tissue.
So long as the cranial bones are separable from one another, these veins are
confined to the particular bones; but when the sutures are obliterated, they unite
with each other, and increase in size. They communicate with the meningeal
veins and the sinuses of the dura mater, and with the veins of the pericranium.
They consist of (1) the frontal, which opens into the supraorbital vein and the
superior sagittal sinus; (2) the anterior temporal, which is confined chiefly to the
frontal bone, and opens into the sphenoparietal sinus and into one of the deep
temporal veins, through an aperture in the great wing of the sphenoid; (3) the
posterior temporal, which is situated in the parietal bone, and ends in the transverse
sinus, through an aperture at the mastoid angle of the parietal bone or through the
652
ANGIOLOGY
mastoid foramen; and (4) the occipital, the largest of the four, which is confined
to the occipital bone, and opens either externally into the occipital vein, or inter-
nally into the transverse sinus or into the confluence of the sinuses {torcular
Herophili) .
Fig. 564. — Veins of the diploe as displayed by the removal of the outer table of the skull.
The Veins of the Brain.
The A'eins of the brain possess no valves, and their walls, owing to the absence
of muscular tissue, are extremely thin. They pierce the arachnoid membrane and
the inner or meningeal layer of the dura mater, and open into the cranial venous
sinuses. They may be divided into two sets, cerebral and cerebellar.
The cerebral veins {vv. cerebri) are divisible into external and internal groups
according as they drain the outer surfaces or the inner parts of the hemispheres.
The external veins are the superior, inferior, and middle cerebral.
The Superior Cerebral Veins {vv. cerebri superiores) , eight to twelve in number,
drain the superior, lateral, and medial surfaces of the hemispheres, and are mainly
lodged in the sulci between the gyri, but some run across the gyri. They open into
the superior sagittal sinus; the anterior veins runs nearly at right angles to the
sinus; the posterior and larger veins are directed obliquely forward and open into
the sinus in a direction more or less opposed to the current of the blood contained
within it.
The Middle Cerebral Vein {v. cerebri media; superficial Sylvian vein) begins on the
lateral surface of the hemisphere, and, running along the lateral cerebral fissure,
ends in the cavernous or the sphenoparietal sinus. It is connected (a) with the
superior sagittal sinus by the great anastomotic vein of Trolard, which opens into one
of the superior cerebral veins; (6) with the transverse sinus by the posterior anasto-
motic vein of Labbe, which courses over the temporal lobe.
The Inferior Cerebral Veins {vv. cerebri iuferiores), of small size, drain the under
surfaces of the hemispheres. Those on the orbital surface of the frontal lobe join
the superior cerebral veins, and through these open into the superior sagittal
sinus; those of the temporal lobe anastomose with the middle cerebral and basal
veins, and join the cavernous, sphenoparietal, and superior petrosal sinuses.
THE VEINS OF THE BRAIN
653
The basal vein is formed at the anterior perforated substance by the union of (a)
a small anterior cerebral vein which accompanies the anterior cerebral artery, (b)
the deep middle cerebral vein (deep Syhian vein), which receives tributaries from
the insula and neighboring gyri, and runs in the lower part of the lateral cerebral
fissure, and (c) the inferior striate veins, which leave the corpus striatum through
the anterior perforated substance. The basal vein passes backward around the
cerebral peduncle, and ends in the internal cerebral vein [vein of Galen) ; it receives
tributaries from the interpeduncular fossa, the inferior horn of the lateral ventricle,
the hippocampal gyrus, and the mid-brain.
The Internal Cerebral Veins {vv. cerebri internes; veins of Galen; deep cerebral
veins) drain the deep parts of the hemisphere and are two in number; each is formed
near the interventricular foramen by the union of the terminal and choroid veins.
They run backward parallel with one another, between the layers of the tela
chorioidea of the third ventricle, and beneath the splenium of the corpus callosum,
where they unite to form a short trunk, the great cerebral vein; just before their
union each receives the corresponding basal vein.
The terminal vein [v. terminalis; vena corporis striati) commences in the groove
between the corpus striatum and thalamus, receives numerous veins from both
of these parts, and unites behind the crus fornicis with the choroid vein, to form
one of the internal cerebral veins. The choroid vein runs along the whole length of
the choroid plexus, and receives veins from the hippocampus, the fornix, and the
corpus callosum.
CAUDATE
NUCLEUS
FORAMEN OF
MONRO
Fig. 565. — Velum interpositum. (Poirier and Charpy.)
GREAT
CEREBRAL VEIN
The Great Cerebral Vein {v. cerebri -magna [Galeni]; great vein of Galen) (Fig. 5G5),
formed by the union of the two internal cerebral veins, is a short median trunk
which curves backward and upward around the splenium of the corpus callosum
and ends in the anterior extremity of the straight sinus.
The cerebellar veins are placed on the surface of the cerebellum, and are dis-
posed in two sets, superior and inferior. The superior cerebellar veins {vv. cerebeUi
superiores) pass partly forward and medialward, across the superior vermis, to end
in the straight sinus and the internal cerebral veins, partly lateralward to the trans-
verse and superior petrosal sinuses. The inferior cerebellar veins {vv. ccrebclli infe-
riores) of large size, end in the transverse, superior petrosal, and occipital sinuses.
k
654
ANGIOLOGY
The Sinuses of the Dura Mater (Sinus Durae Matris).
Emissary Veins.
Ophthahnic Veins and
The sinuses of the dura mater are venous channels which drain the blood from the
brain; they are devoid of valves, and are situated between the two layers of the
dura mater and lined by endothelium continuous with that which lines the veins.
They may be divided into two groups: (1) a postero-superior, at the upper and back
part of the skull, and (2) an antero-inferior, at the base of the skull.
The postero-superior group comprises the
Superior Sagittal.
Inferior Sagittal,
Occipital.
Straight.
Two Transverse.
Dural vein
Superior sagittal
sinus
Venous
lacuna
Venous lacuna
Fig. 506. — Superior sagittal sinus laid open after remova of the skull cap. The cliordae WilUsii are clearly seen.
The venous lacunse are also well shown; from two of them probes are passed into the superior sagittal sinus.
(Poirier and Charpy.)
The superior sagittal sinus (sinus sagittalis superior; superior longitudinal sinus)
(Figs. 5GG, 567) occupies the attached or convex margin of the falx cerebri. Com-
mencing at the foramen cecum, through which it receives a vein from the nasal
cavity, it runs from before backward, grooving the inner surface of the frontal,
the adjacent margins of the two parietals, and the superior division of the cruciate
eminence of the occipital; near the internal occipital protuberance it deviates to
one or other side (usually the right), and is continued as the corresponding trans-
verse sinus. It is triangular in section, narrow in front, and gradually increases in
size as it passes backward. Its inner surface presents the openings of the superior
cerebral veins, which run, for the most part, obliquely forward, and open chiefly
at the back part of the sinus, their orifices being concealed by fibrous folds ; numerous
THE SINUSES OF THE DURA MATER
655
fibrous bands (chorda' WUlisii) extend transversely across the inferior angle of
the sinus; and, lastly, small openings communicate with irregularly shaped venous
spaces {venous lacuna;) in the dura mater near the sinus. There are usually three
lacunae on either side of the sinus: a small frontal, a large parietal, and an occipital,
intermediate in size between the other two (Sargent'). Most of the cerebral
veins from the outer surface of the hemisphere open into these lacunae, and numer-
ous arachnoid granulations {Pacchionian bodies) project into them from below.
The superior sagittal sinus receives the superior cerebral veins, veins from the diploe
and dura mater, and, near the posterior extremity of the sagittal suture, veins from
the pericranium, which pass through the parietal foramina.
The numerous communications exist between this sinus and the veins of the
nose, scalp, and diploe.
Cfreat cerebral vein
Glossophanjnjual nerve
Va(/us nerve
Accessory nerve
Acoustic nerve
Facial nerve
Abducent nerve Trigeminal nerve
Fig. 567. — Dura mater and its proces.se3 exposed by removing part of the right half of the skull, and
Optic nerves
Ophthalmic artery
Diajihra'jma sellce
Oculomotor nerves
Trochlear nerve
the brain.
The inferior sagittal sinus {sinus sayittalis inferior; inferior longitudinal sinus)
(Fig. 567) is contained in the posterior half or two-thirds of the free margin of the
falx cerebri. It is of a cylindrical form, increases in size as it passes backward, and
ends in the straight sinus. It receives several veins from the falx cerebri, and
occasionally a few from the medial surfaces of the hemispheres.
The straight sinus {sinus rectus; tentorial sinus) (Figs. 567, 569) is situated at
the line of junction of the falx cerebri with the tentorium cerebelli. It is triangular
1 Journal of Anatomy and Physiologj-, vol. xlv.
656
ANGIOLOGY
in section, increases in size as it proceeds backward, and runs downward and back-
ward from the end of the inferior sagittal sinus to the transverse sinus of the oppo-
Torcular herophili.
Foramen cecum
Fig. 568. — Sagittal seclion o* the skull- showing the sinuses of the dura.
Optic nei-ve Internal carotid artery
_. , ,7 \ 1 Oculomotor nerve
Diapnragma sellce \
\ I ' Attached margin of tentorium
Free margin of tentorium \ .
Confluence of the sinuses
Fig. 569. — Tentorium cerebelli from above.
site side to that into which the superior sagittal sinus is prolonged. Its terminal
part communicates by a cross branch with the confluence of the sinuses. Besides
THE SINUSES OF THE DURA MATER
657
the inferior sagittal sinus, it receives the great cerebral vein (great vein of Galen)
and the superior cerebellar veins. A few "transverse bands cross its interior.
The transverse sinuses (sijms transversus; lateral shmses) (Figs. 569, 570) are
of large size and begin at the internal occipital protuberance; one, generally the
right, being the direct continuation of the superior sagittal sinus, the other of the
straight sinus. Each transverse sinus passes laterahvard and forward, describing
a slight curve with its convexity upward, to the base of the petrous portion of
the temporal bone, and lies, in this part of its course, in the attached margin of
the tentorium cerebelli; it then leaves the tentorium and curves downward and
Levator palpebrcp.
Rectus superior
Sup. oph-
thalmic vein
Sphenoparietal
sinus
End of straight sinus
Vertebral artery
Superior sagittal sinus
Fig. 570. — The sinuses at the base of the skull.
medialward to reach the jugular foramen, Avhere it ends in the internal jugular
vein. In its course it rests upon the squama of the occipital, the mastoid angle
of the parietal, the mastoid part of the temporal, and, just before its termination,
the jugular process of the occipital; the portion which occupies the groove on the
mastoid part of the temporal is sometimes termed the sigmoid sinus. The trans-
verse sinuses are frequently of unequal size, that formed by the superior sagittal
sinus being the larger; they increase in size as they proceed from behind forward.
On transverse section the horizontal portion exhibits a prismatic, the curved
portion a semicylindrical form. .They receive the blood from the superior petrosal
42
658
ANGIOLOGY
sinuses at the base of the petrous portion of the temporal bone ; they communicate
with the veins of the pericranium by means of the mastoid and condyloid emissary
veins; and they receive some of the inferior cerebral and inferior cerebellar veins,
and some veins from the diploe. The petrosquamous sinus, when present, runs
backward along the junction of the squama and petrous portion of the temporal,
and opens into the transverse sinus.
The occipital sinus (smus occipitalis) (Fig. 570) is the smallest of the cranial
sinuses. It is situated in the attached margin of the falx cerebelli, and is generally
single, but pccasionally there are two. It commences around the margin of the for-
amen magnum by several small venous channels, one of which joins the terminal
part of the transverse sinus; it communicates with the posterior internal vertebral
venous plexuses and ends in the confluence of the sinuses.
The Confluence of the Sinuses {conflnens siimnm; torcular Herophili) is the term
applied to the dilated extremity of the superior sagittal sinus. It is of irregular
form, and is lodged on one side (generally the right) of the internal occipital pro-
tuberance. From it the transverse sinus of the same side is derived. It receives
also the blood from the occipital sinus, and is connected across the middle line with
the commencement of the transverse sinus of the opposite side.
The antero-inferior group of sinuses comprises the
Two Cavernous.
Two Intercavernous
Two Superior Petrosal.
Two Inferior Petrosal.
Basilar Plexus.
The cavernous sinuses {sinvs cavernosus) (Figs. 570, 571) are so named because
they present a reticulated structure, due to their being traversed by numerous inter-
lacing filaments. They are of irregular
Internal carotid artery
Cavernous sinvs
Oculomotor nerve
Trochlear nerve
Ophthalmic nerve
Abducent nerve
Maxillary nerve
Fig. 571. — Oblique section through the cavernous sinus.
form, larger behind than in front, and
are placed one on either side of the
body of the sphenoid bone, extending
from the superior orbital fissure to
the apex of the petrous portion of
the temporal bone. Each opens be-
hind into the petrosal sinuses. On
the medial wall of each sinus is the
internal carotid artery, accompanied
by filaments of the carotid plexus;
near the artery is the abducent nerve;
on the lateral wall are the oculomotor
and trochlear nerves, and the oph-
thalmic and maxillary divisions of
the trigeminal nerve (Fig. 571). These structures are separated from the blood
flowing along the sinus by the lining membrane of the sinus. The cavernous
sinus receives the superior ophthalmic vein through the superior orbital fissure,
some of the cerebral veins, and also the small sphenoparietal sinus, which courses
along the under surface of the small wing of the sphenoid. It communicates with
the transverse sinus by means of the superior petrosal sinus; with the internal
jugular vein through the inferior petrosal sinus and a plexus of veins on the inter-
nal carotid artery ; with the pterygoid venous plexus through the foramen Vesalii,
foramen ovale, and foramen lacerum, and with the angular vein through the
ophthalmic vein. The two sinuses also communicate with each other by means
of the anterior and posterior intercavernous sinuses.
The ophthalmic veins (Fig. 572), two in number, superior and inferior, are
devoid of valves.
THE SINUSES OF THE DURA MATER
659
The Superior Ophthalmic Vein (v. ophthalmica superior) begins at the inner angle
of the orbit in a vein named the nasofrontal which communicates anteriorly with the
angular vein; it pursues the same course as the ophthalmic artery, and receives
tributaries corresponding to the branches of that vessel. Forming a short single
trunk, it passes between the two heads of the Rectus lateralis and through the medial
part of the superior orbital fissure, and ends in the cavernous sinus.
The Inferior Ophthalmic Vein (v. ophthalmica inferior) begins in a venous net-work
at the forepart of the floor and medial wall of the orbit; it receives some veins from
the Rectus inferior, Obliquus inferior, lacrimal sac and eyelids, runs backward in
the lower part of the orbit and divides into two branches. One of these passes
through the inferior orbital fissure and joins the pterygoid venous plexus, while
the other enters the cranium through the superior orbital fissure and ends in the
cavernous sinus, either by a separate opening, or more frequently in common with
the superior ophthalmic vein.
Cavernous
siniis
Inferior
ophthalmic
-Veins of orbit. (Poirier and Charpy.)
The intercavernous sinuses (sini intercavernosi) (Fig. 570) are two in number, an
anterior and a posterior, and connect the two cavernous sinuses across the middle
line. The anterior passes in front of the hypophysis cerebri, the posterior behind it,
and they form with the cavernous sinuses a venous circle (circular sinus) around the
hypophysis. The anterior one is usually the larger of the two, and one or other is
occasionally absent.
The superior petrosal sinus (sinus petrosus superior) (Fig. 570) small and narrow,
connects the cavernous with the transverse sinus. It runs lateralward and back-
ward, from the posterior end of the cavernous sinus, over the trigeminal nerve,
and lies in the attached margin of the tentorium cerebelli and in the superior
petrosal sulcus of the temporal bone; it joins the transverse sinus where the latter
curves downward on the inner surface of the mastoid part of the temporal. It
receives some cerebellar and inferior cerebral veins, and veins from the tympanic
cavity.
The inferior petrosal sinus (sinus petrosus inferior) (Fig. 570) is situated in the
inferior petrosal sulcus formed by the junction of the petrous part of the temporal
with the basilar part of the occipital. It begins in the postero-inferior part of the
cavernous sinus, and, passing through the anterior part of the jugular foramen,
ends in the superior bulb of the internal jugular vein. The inferior petrosal sinus
660 ANGIOLOGY
receives the internal auditory veins and also veins from the medulla oblongata,
pons, and under surface of the cerebellum.
The exact relation of the parts to one another in the jugular foramen is as follows:
the inferior petrosal sinus lies medially and anteriorly with the meningeal branch
of the ascending pharyngeal artery, and is directed obliquely downward and back-
ward; the transverse sinus is situated at the lateral and back part of the foramen
with a meningeal branch of the occipital artery, and between the two sinuses are
the glossopharyngeal, vagus, and accessory nerves. These three sets of structures
are divided from each other by two processes of fibrous tissue. The junction of the
inferior petrosal sinus with the internal jugular vein takes place on the lateral
aspect of the nerves.
The basilar plexus (plexus hasilaris; transverse or basilar sinus) (Fig. 571) con-
sists of several interlacing venous channels between the layers of the dura mater
over the basilar part of the occipital bone, and serves to connect the two inferior
petrosal sinuses. It communicates with the anterior vertebral venous plexus.
Emissary Veins (emissaria) . — The emissary veins pass through apertures in the
cranial wall and establish communication between the sinuses inside the skull and
the veins external to it. Some are always present, others only occasionally so.
The principal emissary veins are the following: (1) A mastoid emissary vein,
usually present, runs through the mastoid foramen and unites the transverse sinus
with the posterior auricular or with the occipital vein. (2) A parietal emissary
vein passes through the parietal foramen and connects the superior sagittal sinus
with the veins of the scalp. (3) A net-work of minute veins (rete canalis hypoglossi)
traverses the hypoglossal canal and joins the transverse sinus with the vertebral
vein and deep veins of the neck. (4) An inconstant condyloid emissary vein passes
through the condyloid canal and connects the transverse sinus with the deep veins
of the neck. (5) A net-work of veins (rete foraminis ovalis) unites the cavernous
sinus with the pterygoid plexus through the foramen ovale. (6) Two or three small
veins run through the foramen lacerum and connect the cavernous sinus with the
pterygoid plexus. (7) The emissary vein of the foramen of Vesalius connects the
same parts. (8) An internal carotid plexus of veins traverses the carotid canal and
unites the cavernous sinus with the internal jugular vein. (9) A vein is trans-
mitted through the foramen cecum and connects the superior sagittal sinus with
the veins of the nasal cavity.
THE VEINS OF THE UPPER EXTREMITY AND THORAX.
The veins of the upper extremity are divided into two sets, superficial and deep;
the two sets anastomose frequently with each other. The superficial veins are
placed immediately beneath the integument between the two layers of superficial
fascia. The deep veins accompany the arteries, and constitute the vense comi-
tantes of those vessels. Both sets are provided with valves, which are more
numerous in the deep than in the superficial veins.
The Superficial Veins of the Upper Extremity.
The superficial veins of the upper extremity are the digital, metacarpal, cephalic,
basilic, median.
Digital Veins. — The dorsal digital veins pass along the sides of the fingers and
are joined to one another by oblique communicating branches. Those from the
adjacent sides of the fingers unite to form three dorsal metacarpal veins (Fig.
573), which end in a dorsal venous net-work opposite the middle of the meta-
carpus. The radial part of the net-work is joined by the dorsal digital vein from the
radial side of the index finger and by the dorsal digital veins of the thumb, and
is prolonged upward as the cephalic vein. The ulnar part of the net-work receives
THE SUPERFICIAL VEINS OF THE UPPER EXTREMITY
661
the dorsal digital vein of the ulnar side of the little finger and is continued upward
as the basilic vein. A communicating branch frequently connects the dorsal
venous network with the cephalic vein about the middle of the forearm.
The volar digital veins on each finger are connected to the dorsal digital veins
by oblique intercapitular veins. They drain into a venous plexus which is situated
over the thenar and hypothenar eminences and across the front of the wrist.
Cephalic
Dorsal venous
network
Fig. 573. — The veins on the dorsum of the hand. (Bourgery.)
The cephalic vein (Fig. 574) begins in the radial part of the dorsal venous net-
work and winds upward around the radial border of the forearm, receiving tribu-
taries from both surfaces. Below the front of the elbow it gives off the vena mediana
cubiti {median basilic vein), which receives a communicating branch from the deep
veins of the forearm and passes across to join the basilic vein. The cephalic vein
then ascends in front of the elbow in the groove between the Brachioradialis and
the Biceps brachii. It crosses superficial to the musculocutaneous nerve and ascends
in the groove along the lateral border of the Biceps brachii. In the upper third
of the arm it passes between the Pectoralis major and Deltoideus, where it is accom-
662
ANGIOWGY
panied by the deltoid
clavicular fascia and
below the clavicle.
Cephalic vein
Lateral
antibrachial
cutaneoiLS
nerve
Accessory
cephalic vein
Cephalic vein
branch of the thoracoacromial artery. It pierces the coraco-
, crossing the axillary artery, ends in the axillary vein just
Sometimes it communicates with the external jugular vein
by a branch which ascends in front
of the clavicle.
The accessory cephalic vein {v.
cephalica acccssoria) arises either
from a small tributory plexus on
the back of the forearm or from
the ulnar side of the dorsal venous
net-work; it joins the cephalic be-
low the elbow. In some cases the
accessory cephalic springs from
the cephalic above the wrist and
joins it again higher up. A large
oblique branch frequently con-
nects the basilic and cephalic veins
on the back of the forearm.
The basilic vein {v. basilica)
(Fig. 574) begins in the ulnar part
of the dorsal venous network. It
runs up the posterior surface of
the ulnar side of the forearm and
inclines forward to the anterior
surface below the elbow, where it
is joined by the vena mediana
cubiti. It ascends obliquely in
the groove between the Biceps
brachii and Pronator teres and
crosses the brachial artery, from
which it is separated by the lacertus
fibrosus; filaments of the medial
antibrachial cutaneous nerve pass
both in front of and behind this
portion of the vein. It then runs
upward along the medial border
of the Biceps brachii, perforates
the deep fascia a little below the
middle of the arm, and, ascending
on the medial side of the brachial
artery to the lower border of the
Teres major, is continued onward
as the axillary vein.
The median antibrachial vein
{v. mediana antibrachii) drains the
venous plexus on the volar surface
of the hand. It ascends on the
ulnar side of the front of the fore-
arm and ends in the basilic vein or
in the vena mediana cubiti; in a
small proportion of cases it divides
into two branches, one of which
joins the basilic, the other the
cephalic, below the elbow.
— Basilic vein
VeTia mediana
cubiti
Basilic vein
Medial anti-
bra<:hial cutane-
ous nerve
Median anti-
brachial vein
Fig. 574. — The superficial veins of the upper extremity.
THE DEEP VEINS OF THE UPPER EXTREMITY
663
NAE COMITES
BRACHIAL
ERY
The Deep Veins of the Upper Extremity.
The deep veins follow the course of the arteries, forming their venae comitantes-
They are generally arranged in pairs, and are situated one on either side of the
corresponding artery, and connected at intervals by short transverse branches.
Deep Veins of the Hand. — ^The superficial and deep volar arterial arches are
each accompanied by a pair of venae comitantes which constitute respectively
the superficial and deep volar venous arches, and receive the veins corresponding
to the branches of the arterial arches; thus the common volar digital veins, formed by
the union of the proper volar digital veins, open into the superficial, and the volar
metacarpal veins into the deep volar venous arches. The dorsal metacarpal veins
receive perforating branches
from the volar metacarpal
veins and end in the radial
veins and in the superficial
veins on the dorsum of the
wrist.
The deep veins of the fore-
arm are the venae comitantes
of the radial and ulnar veins
and constitute respectively the
upward continuations of the
deep and superficial volar
venous arches; they unite in
front of the elbow to form
the brachial veins. The radial
veins are smaller than the ulnar
and receive the dorsal meta-
carpal veins. The ulnar veins
receive tributaries from the
deep volar venous arches and
communicate with the super-
ficial veins at the wrist; near
the elbow they receive the volar
and dorsal interosseous veins
and send a large communicat-
ing branch (profunda vein) to
the vena mediana cubiti.
The brachial veins (vv.
brachiales) are placed one on
either side of the brachial
artery, receiving tributaries
corresponding with the branches given off from that vessel ; near the lower margin
of the Subscapularis, they join the axillary vein; the medial one frequently joins
the basilic vein.
These deep veins have numerous anastomoses, not only with each other, but
also with the superficial veins.
The axillary vein (v. axillaris) begins at the lower border of the Teres major,
as the continuation of the basilic vein, increases in size as it ascends, and ends at the
outer border of the first rib as the subclavian vein. Near the lower border of
the Subscapularis it receives the brachial veins and, close to its termination, the
cephalic vein; its other tributaries correspond with the branches of the axillary
artery. It lies on the medial side of the artery, which it partly overlaps; between
the two vessels are the medial cord of the brachial plexus, the median, the ulnar.
INTEROSSEOUS
VEINS
ULNAR DEEP
VEINS
ASTOMOSIS
RADIAL
0 ULNAR
RADIAL DEEP
VEINS
Fig. 575 — The deep veins of the upper extremity. (Bourgery.)
664
ANGIOLOGY
and the medial anterior thoracic nerves. It is provided with a pair of valves oppo-
site the lower border of the Subscapularis ; valves are also found at the ends of the
cephalic and subscapular veins.
The subclavian vein {v. suhclavia), the continuation of the axillary, extends
from the outer border of the first rib to the sternal end of the clavicle, where it
unites with the internal jugular to form the innominate vein. It is in relation, in
front, with the clavicle and Subclavius; belmid and above, with the subclavian
artery, from which it is separated medially by the Scalenus anterior and the phrenic
nerve. Below, it rests in a depression on the first rib and upon the pleura. It is
usually provided with a pair of valves, which are situated about 2.5 cm. from its
termination.
AXILLARY
ARTERY
MUSCULO-
CUTANEUS NERVE
MEDIAN NERVE
ANTERIOR
CIRCUMFLEX
LONG THORACIC
Fig. 576. — The veins of the right axilla, viewed from in front. (Spalteholz )
The subclavian vein occasionally rises in the neck to a level with the third part
of the subclavian artery, and occasionally passes with this vessel behind the Scalenus
anterior.
Tributaries. — This vein receives the external jugular vein, sometimes the anterior
jugular vein, and occasionally a small branch, which ascends in front of the clavicle,
from the cephalic. At its angle of junction with the internal jugular, the left
subclavian vein receives the thoracic duct, and the right subclavian vein the right
lymphatic duct.
The Veins of the Thorax (Fig. 577)
The innominate veins (vv. anonymce; brachiocephalic veins) are two large trunks,
placed one on either side of the root of the neck, and formed by the union of the
internal jugular and subclavian veins of the corresponding side; they are devoid
of valves.
The Right Iimominate Vein {v. anonyma dextra) is a short vessel, about 2.5 cm.
in length, which begins behind the sternal end of the clavicle, and, passing almost
vertically downward, joins with the left. innominate vein just below the cartilage
THE VEINS OF THE THORAX
665
of the first rib, close to the right border of the sternum, to form the superior vena
cava. It lies in front and to the right of the innominate artery; on its right side
Anterior jugular
Superior thyroid
Middle
thyroid
Internal
matamarg
Inferior
phrenic
Suprarenal
11 ce^
CiTckrn,
Fig. 577. — The venae cavae and azygos veins, with their tributaries.
are the phrenic nerve and the pleura, which are interposed between it and the apex
of the lung. This vein, at its commencement, receives the right vertebral vein; and,
666 ANGIOLOGY
lower down, the right internal mammary and right inferior thyroid veins, and some-
times the vein from the first intercostal space.
The Left Innominate Vein (v. anonyma sinistra), about 6 cm. in length, begins
behind the sternal end of the clavicle and runs obliquely downward and to the
right behind the upper half of the manubrium sterni to the sternal end of the first
right costal cartilage, w'here it unites with the right innominate vein to form the
superior vena cava. It is separated from the manubrium sterni by the Sterno-
hyoideus and Sternothyreoideus, the thymus or its remains,. and some loose areolar
tissue. Behind it are the three large arteries, innominate, left common carotid, and
left subclavian, arising from the aortic arch, together with the vagus and phrenic
nerves. The left innominate vein may occupy a higher level, crossing the jugular
notch and lying directly in front of the trachea.
Tributaries. — Its tributaries are the left vertebral, left internal mammary, left
inferior thyroid, and the left highest intercostal veins, and occasionally some
thymic and pericardiac veins.
Peculiarities. — Sometimes the innominate veins open separately into the right atrium; in
such cases the right vein takes the ordinary course of the superior vena cava; the left vein —
left superior vena cava, as it is then termed — which may communicate by a small branch with
the right one, passes in front of the root of the left lung, and, turning to the back of the heart,
ends in the right atrium. This occasional condition in the adult is due to the persistence of the
early fetal condition, and is the normal state of things in birds and some mammalia.
The internal mammary veins (vv. mammaricB interna) are venae comitantes
to the lower half of the internal mammary artery, and receive tributaries corre-
sponding to the branches of the artery. They then unite to form a single trunk,
which runs up on the medial side of the artery and ends in the corresponding
innominate vein. The superior phrenic vein, i. e., the vein accompanying the peri-
cardiacophrenic artery, usually opens into the internal mammary vein.
The inferior thyroid veins {vv. thyreoideoe inferiores) two, frequently three or
four, in number, arise in the venous plexus on the thyroid gland, communicating
with the middle and superior thyroid veins. They form a plexus in front of the
trachea, behind the Sternothyreoidei. From this plexus, a left vein descends and
joins the left innominate trunk, and a right vein passes obliquely downward and to
the right across the innominate artery to open into the right innominate vein,
just at its junction with the superior vena cava; sometimes the right and left veins
open by a common trunk in the latter situation. These veins receive esophageal
tracheal, and inferior laryngeal veins, and are provided with valves at their
terminations in the innominate veins.
The highest intercostal vein {v. intercostalis siiprema; suyerior intercostal veins)
(right and left) drain the blood from the upper three or four intercostal spaces.
The right vein {v. intercostalis suprema dextra) passes downward and opens into the
vena azygos; the left vein {v. intercostalis suj)rema sinistra) runs across the arch
of the aorta and the origins of the left subclavian and left common carotid
arteries and opens into the left innominate vein. It usually receives the left
bronchial vein, and sometimes the left superior phrenic vein, and communicates
below with the accessory hemiazygos vein.
The superior vena cava (r. cava superior) drains the blood from the upper half
of the body. It measures about 7 cm. in length, and is formed by the junction of
the two innominate veins. It begins immediately below the cartilage of the right
first rib close to the sternum, and, descending vertically behind the first and second
intercostal spaces, ends in the upper part of the right atrium opposite the upper
border of the third right costal cartilage: the lower half of the vessel is within the
pericardium. In its course it describes a slight curve, the convexity of which is
to the right side.
THE VEINS OF THE VERTEBRAL COLUMN 667
Relations. — In front are the anterior margins of the right lung and pleura with the pericardium
intervening below; these separate it from the first and second intercostal spaces and from the
second and third right costal cartilages; behind it are the root of the right lung and the right
vagus nerve. On its right side are the phrenic nerve and right pleura; on its left side, the com-
mencement of the innominate artery and the ascending aorta, the latter overlapping it. Just
before it pierces the pericardium, it receives the azygos vein and several small veins from the
pericardium and other contents of the mediastinal cavity. The portion contained within the
pericardium is covered, in front and laterally, by the serous layer of the membrane. The superior
vena cava has no valves.
The azygos vein (w. azygos; vena azygos major) begins opposite the first or second
lumbar vertebra, by a branch, the ascending lumbar vein (page 678) ; sometimes by
a branch from the right renal vein, or from the inferior vena cava. It enters the
thorax through the aortic hiatus in the diaphragm, and passes along the right side
of the vertebral column to the fourth thoracic vertebra, where it arches forward
over the root of the right lung, and ends in the superior vena cava, just before
that vessel pierces the pericardium. In the aortic hiatus, it lies with the thoracic
duct on the right side of the aorta ; in the thorax it lies upon the intercostal arteries,
on the right side of the aorta and thoracic duct, and is partly covered by pleura.
Tributaries. — It receives the right subcostal and intercostal veins, the upper three
or four of these latter opening by a common stem, the highest superior intercostal
vein. It receives the hemiazygos veins, several esophageal, mediastinal, and peri-
cardial veins, and, near its termination, the right bronchial vein. A few imperfect
valves are found in the azygos vein; but its tributaries are provided with complete
valves.
The intercostal veins on the left side, below the upper three intercostal spaces,
usually form two trunks, named the hemiazygos and accessory hemiazygos veins.
The Hemiazygos Vein (v. hemiazygos; vena azygos minor inferior) begi7is in the
left ascending lumbar or renal vein. It enters the thorax, through the left crus
of the diaphragm, and, ascending on the left side of the vertebral column, as high
as the ninth thoracic vertebra, passes across the column, behind the aorta, esoph-
agus, and thoracic duct, to end in the azygos vein. It receives the lower four
or five intercostal veins and the subcostal vein of the left side, and some esophageal
and mediastinal veins.
The Accessory Hemiazygos Vein {v. hemiazygos accessoria; vena azygos minor supe-
rior) descends on the left side of the vertebral column, and varies inversely in size
with the highest left intercostal vein. It receives veins from the three or four
intercostal spaces between the highest left intercostal vein and highest tributary
of the hemiazygos; the left bronchial vein sometimes opens into it. It either crosses
the body of the eighth thoracic vertebra to join the azygos vein or ends in the
hemiazygos. When this vein is small, or altogether wanting, the left highest
intercostal vein may extend as low as the fifth or sixth intercostal space.
In obstruction of the superior vena cava, the azygos and hemiazygos veins are one of the
principal means by which the venous circulation is carried on, connecting as they do the superior
and inferior venae cavae, and communicating with the common iliac vein? by the ascending lumbar
veins and with many of the tributaries of the inferior vena cava.
The BroncMal Veins (vv. bronchiales) return the blood from the larger bronchi, and
from the structures at the roots of the lungs; that of the right side opens into the
azygos vein, near its termination; that of the left side, into the highest left inter-
costal or the accessory hemiazygos vein. A considerable quantity of the blood which
is carried to the lungs through the bronchial arteries is returned to the left side of
the heart through the pulmonary veins.
The Veins of the Vertebral Column (Figs. 578, 579).
The veins which drain the blood from the vertebral column, the neighboring
muscles, and the meninges of the medulla spinalis form intricate plexuses extending
668
ANGIOLOGY
along the entire length of the column; these plexuses may be divided into two
groups, external and internal, according to their positions inside or outside the
vertebral canal. The plexuses of the two groups anastomose freely with each other
and end in the intervertebral veins.
The external vertebral venous plexuses {plexus venosi vertebrales exierni; extra-
spinal veins) best marked in the cervical region, consist of anterior and posterior
plexuses which anastomose freely with each other. The anterior external plexuses
lie in front of the bodies of the vertebrae, communicate with the basivertebral and
intervertebral veins, and receive tributaries from the vertebral bodies. The pos-
terior external plexuses are placed partly on the posterior surfaces of the vertebral
arches and their processes, and partly between the deep dorsal muscles. They are
best developed in the cervical region, and there anastomose with the vertebral,
occipital, and deep cervical veins.
The internal vertebral venous plexuses {plexus venosi vertebrales interni; intra-
spinal veins) lie within the vertebral canal between the dura mater and the verte-
brae, and receive tributaries from the bones and from the medulla spinalis. They
Posterior external plexuses
Fig. 578. — Transverse section of a thoracic vertebra, Fig. 57
showing the vertebral venous plexuses.
579. — Median sagittal section of two thoracic verte-
brae, showing the vertebral venous plexuses.
^orm a closer net-work than the external plexuses, and, running mainly in a vertical
direction, form four longitudinal veins, two in front and two behind; they therefore
may be divided into anterior and posterior groups. The anterior internal plexuses
consist of large veins which lie on the posterior surfaces of the vertebral bodies and
intervertebral fibrocartilages on either side of the posterior longitudinal ligament;
under cover of this ligament they are connected by trans\erse branches into which
the basivertebral veins open. The posterior internal plexuses are placed, one on
either side of the middle line in front of the vertebral arches and ligamenta fiava,
and anastomose by veins passing through those ligaments with the posterior exter-
nal plexuses. The anterior and posterior plexuses communicate freely with one
another by a series of venous rings {retia vcnosa vertehrarum) , one opposite each
vertebra. ' Around the foramen magnum they form an intricate net-work which
opens into the vertebral veins and is connected above with the occipital sinus,
the basilar plexus, the condyloid emissary vein, and the rete canalis hypoglossi.
The basivertebral veins \n\ hasivertebrales) emerge from the foramina on the
posterior surfaces of the vertebral bodies. They are contained in large, tortuous
THE SUPERFICIAL VEINS OF THE LOWER EXTREMITY G69
channels in the substance of the bones, similar in every respect to those found in
the diploe of the cranial bones. They communicate through small openings on the
front and sides of the bodies of the vertebrae with the anterior external vertebral
plexuses, and converge behind to the principal canal, which is sometimes double
toward its posterior part, and open by valved orifices into the transverse branches
which unite the anterior internal vertebral plexuses. They become greatly enlarged
in advanced age.
The intervertebral veins {vv. intervertebrales) accompany the spinal nerves
through the intervertebral foramina; they receive the veins from the medulla
spinalis, drain the internal and external vertebral plexuses and end in the vertebral,
intercostal, lumbar, and lateral sacral veins, their orifices being provided with
valves.
The veins of the medulla spinalis (vv. spinales; veins of the spinal cord) are
situated in the pia mater and form a minute, tortuous, venous plexus. They
emerge chiefly from the median fissures of the medulla spinalis and are largest in
the lumbar region. In this plexus there are (1) two median longitudinal veins,
one in front of the anterior fissure, and the other behind the posterior sulcus of the
cord, and (2) four lateral longitudinal veins which run behind the nerve roots.
They end in the intervertebral veins. Near the base of the skull they unite, and
form two or three small trunks, which communicate with the vertebral veins,
and then end in the inferior cerebellar veins, or in the inferior petrosal sinuses.
THE VEINS OF THE LOWER EXTREMITY, ABDOMEN, AND PELVIS.
The veins of the lower extremity are subdivided, like those of the upper, into
two sets, superficial and deep ; the superficial veins are placed beneath the integument
between the two layers of superficial fascia ; the deep veins accompany the arteries.
Both sets of veins are provided with valves, which are more numerous in the deep
than in the superficial set. Valves are also more numerous in the veins of the
lower than in those of the upper limb.
The Superficial Veins of the Lower Extremity.
The superficial veins of the lower extremity are the great and small saphenous
veins and their tributaries.
On the dorsum of the foot the dorsal digital veins receive, in the clefts between the
toes, the intercapitular veins from the plantar cutaneous venous arch and join to
form short common digital veins which unite across the distal ends of the metatarsal
bones in a dorsal venous arch. Proximal to this arch is an irregular venous net-
work which receives tributaries from the deep veins and is joined at the sides of the
foot by a medial and a lateral marginal vein, formed mainly by the union of branches
from the superficial parts of the sole of the foot.
On the sole of the foot the superficial veins form a plantar cutaneous venous arch
which extends across the roots of the toes and opens at the sides of the foot into
the medial and lateral marginal veins. Proximal to this arch is a plantar cutaneous
venous net-work which is especially dense in the fat beneath the heel; this net-work
communicates with the cutaneous venous arch and with the deep veins, but is
chiefly drained into the medial and lateral marginal veins.
The great saphenous vein {v. saphena magna; internal or long saphenous vein)
(Fig. 581), the longest vein in the body, begins in the medial marginal vein of the
dorsum of the foot and ends in the femoral vein about 3 cm. below the inguinal
hgament. It ascends in front of the tibial malleolus and along the medial side of
the leg in relation with the saphenous nerve. It runs upward behind the medial
670
AXGIOLOGY
condyles of the tibia and femur and along the medial side of the thigh and, passing
through the fossa ovalis, ends in the femoral vein.
Tributaries. — At the ankle it receives branches from the sole of the foot through
the medial marginal vein; in the leg it anastomoses freely with the small saphenous
vein, communicates with the anterior and posterior tibial veins and receives many
cutaneous veins; in the thigh it communicates with the femoral vein and receives
numerous tributaries; those from the medial and posterior parts of the thigh
frequently unite to form a* large accessory saphenous vein which joins the main
vein at a variable level. Near the fossa ovalis (Fig. 5S0) it is joined by the super-
ficial epigastric, superficial iliac circumflex, and superficial external pudendal veins.
A vein, named the thoracoepigastric, runs along the lateral aspect of the trunk
between the superficial epigastric vein below and the lateral thoracic vein above
and establishes an important communication between the femoral and axillary
V'Cms.
Fig. 580. — The great saphenous vein and its tributaries at the fossa ovalis.
The valves in the great saphenous vein vary from ten to twenty in number;
they are more numerous in the leg than in the thigh.
The small saphenous vein (v. saphena parva; external or short saphenous vein)
(Fig. 582) begins behind the lateral malleolus as a continuation of the lateral
marginal vein; it first ascends along the lateral margin of the tendocalcaneus,
and then crosses it to reach the middle of the back of the leg. Running directly
upward, it perforates the deep fascia in the lower part of the popliteal fossa, and
ends in the popliteal vein, between the heads of the Gastrocnemius. It commu-
THE DEEP VEINS OF THE LOWER EXTREMITY
671
nicates with the deep veins on the dorsum of the foot, and receives numerous large
tributaries from the back of the leg. Before it pierces the deep fascia, it gives off
a branch which runs upward and forward to join
the great saphenous vein. The small saphenous
vein possesses from nine to twelve valves, one of
which is always found near its termination in the
popliteal vein. In the lower third of the leg the
small saphenous vein is in close relation with
the sural nerve, in the upper two-thirds with
the medial sural cutaneous nerve.
vV^
^N
The Deep Veins of the Lower Extremity.
The deep veins of the lower extremity accom-
pany the arteries and their branches; they possess
numerous valves.
\l
It
Fig. 581. — The great saphenous vein and
its tributaries.
Fig. 582. — The small saphenous vein.
The plantar digital veins (rr. digUales plantares) arise from plexuses on the
plantar surfaces of the digits, and, after sending intercapitular veins to join the
672
ANGIOLOGY
dorsal digital veins, unite to form four metatarsal veins ; these run backward in
the metatarsal spaces, communicate, by means of perforating veins, with the
veins on the dorsum of the foot, and unite to form the deep plantar venous arch
which lies alongside the plantar arterial arch. From the deep plantar venous arch
the medial and lateral plantar veins run backward close to the corresponding
arteries and, after communicating with the great and small saphenous veins, unite
behind the medial malleolus to form the posterior tibial veins.
The posterior tibial veins (vv. tibiales posteriores) accompany the posterior
tibial artery, and are joined by the peroneal veins.
The anterior tibial veins (vv. tibiales anteriores) are
the upward continuation of the venae comitantes of the
dorsalis pedis artery. They leave the front of the
leg by passing between the tibia and fibula, over the
interosseous membrane, and unite with the posterior
tibial, to form the popliteal vein.
The Popliteal Vein [v. j^oplitea) (Fig. 583) is formed
by the junction of the anterior and posterior tibial veins
at the lower border of the Popliteus; it ascends through
the popliteal fossa to the aperture in the Adductor mag-
nus, where it becomes the femoral vein. In the lower
part of its course it is placed medial to the artery;
between the heads of the Gastrocnemius it is super-
ficial to that vessel; but above the knee-joint, it is close
to its lateral side. It receives tributaries corresponding
to the branches of the popliteal artery, and it also
receives the small saphenous vein. The valves in the
popliteal vein are usually four in number.
The femoral vein {v. femoralis) accompanies the
femoral artery through the upper two-thirds of the
thigh. In the lower part of its course it lies lateral to
the artery; higher up, it is behind it; and at the inguinal
ligament, it lies on its medial side, and on the same
plane. It receives numerous muscular tributaries, and
about 4 cm. below the inguinal ligament is joined b}'
thev. profunda femoris; near its termination it is joined
by the great saphenous vein. The valves in the femoral
vein are three in number.
The Deep Femoral Vein {v. profunda femoris) receives
tributaries corresponding to the perforating branches of the profunda artery, and
through these establishes communications with the popliteal vein below and the
inferior gluteal vein above. It also receives the medial and lateral femoral circum-
flex veins.
The Veins of the Abdomen and Pelvis (Figs. 585, 586, 587).
The external iliac vein (r. iliaca externa), the upward continuation of the femoral
vein, begins behind the inguinal ligament, and, passing upward along the brim
of the lesser pelvis, ends opposite the sacroiliac articulation, by uniting with the
hypogastric vein to form the common iliac vein. On the right side, it lies at first
medial to the artery: but, as it passes upward, gradually inclines behind it. On
the left side, it lies altogether on the medial side of the artery. It frequently
contains one, sometimes two, valves.
Tributaries. — The external iliac vein receives the inferior epigastric, deep iliac
circumflex, and pubic veins.
The Inferior Epigastric Vein {v. epigastrica inferior; deep epigastric vein) is formed
Fig. 583.— The popliteal vein.
THE VEINS OF THE ABDOMEN AND PELVIS
673
by the union of the vena? comitantes of the inferior epigastric artery, which com-
municate above with the superior epigastric vein; it joins the external ihac about
1.25 cm. above the inguinal ligament.
The Deep Iliac Circumflex Vein (r. circumflexa ilium profunda) is formed by the
union of the venae comitantes of the deep iliac circumflex artery, and joins the
external iliac vein about 2 cm. above the inguinal ligament.
The Pubic Vein communicates with the obturator vein in the obturator foramen,
and ascends on the back of the pubis to the external iliac vein.
The hypogastric vein (r. hypogastrica; internal iliac vein) begins near the upper
part of the greater sciatic foramen, passes upward behind and slightly medial to
the hypogastric artery and, at the brim of the pelvis, joins with the external iliac
to form the common iliac vein.
UMBILICUS
SUPERFICIAL
EPIGASTRIC
SUPCRPlCIAl
INTERNAL
CIRCUMFLEX
SUPERFI
EXTE
PU
SUPERFICIAL
ILIAC
CIRCUMFLCX
Fig. 5S4. — The femoral vein and its tributaries. (Poirior and Charpy.)
Tributaries. — With the exception of the fetal umbilical vein which passes upward
and backward from the umbilicus to the liver, and the iliolumbar vein which usually
joins the common iliac vein, the tributaries of the hypogastric vein correspond
with the branches of the hypogastric artery. It receives (a) the gluteal, internal
pudendal, and obturator veins, which have their origins outside the pelvis; (b) the
lateral sacral veins, which lie in front of the sacrum; and (c) the middle hemorrhoidal,
vesical, uterine, and vaginal veins, which originate in ^•enous plexuses connected
with the pelvic viscera.
43 •
674
ANGIOLOGY
1. The Superior Gluteal Veins (vv. glutaece superiores; gluteal veins) are venae
comitantes of the superior gluteal artery; they receive tributaries from the buttock
corresponding with the branches of the artery, and enter the pelvis through the
greater sciatic foramen, above the Piriformis, and frequently unite before ending
in the hypogastric vein.
TTiird lumbar
Deep iliac — ^^
circumjiea \ y
Obturator
Prostatic plexus
D^p dorsal vein
of penis
Scrotal
Fig. 585.
Vesical plexus Internal pudendal
-The veins of the right half of the male pelvis. (Spalteholz).
Superior
hemorrhoidal
Hemorrhoidal \
plexus I
M £ Middle
hemorrhoidal
Inferior
hemorrhoidal
2. The Inferior Gluteal Veins {m. glutaece inferior es ; sciatic veins), or vense comi-
tantes of the inferior gluteal artery, begin on the upper part of the back of the
thigh, where they anastomose with the medial femoral circumflex and first perfo-
rating veins. They enter the pelvis through the lower part of the greater sciatic
foramen and join to form a single stem which opens into the lower part of the hypo-
gastric vein.
3. The Internal Pudendal Veins {internal pudic veins) are the vense comitantes
of the internal pudendal artery. They begin in the deep veins of the penis which
issue from the corpus cavernosum penis, accompany the internal pudendal artery,
and unite to form a single vessel, which ends in the hypogastric vein. They receive
the veins from the urethral bulb, and the perineal and inferior hemorrhoidal veins.
THE VEINS OF THE ABDOMEN AND PELVIS
675
DEEP
CIRCUMFLEX
LIAC
NFERIOR
EPIGASTRIC
SACRAL
Fio. 586. — The iliac veins. (Poirier and Charpy.)
MIDDLE
HEMOnRHOIDAL,^=
INFERIOR ^
HEMORRHOIDAL
Fig. 587. — Scheme of the anastomosis of the veins of tfte rectum. (Poirier and Charpy.)
676 ANGIOLOGY
The deep dorsal vein of the penis communicates with the internal pudendal veins,
but ends mainly in the pudendal plexus.
4. The Obturator Vein (v. obturatoria) begins in the upper portion of the adductor
region of the thigh and enters the pelvis through the upper part of the obturator
foramen. It runs backward and upward on the lateral wall of the pelvis below the
obturator artery, and then passes between the ureter and the hypogastric artery,
to end in the hypogastric vein.
5. The Lateral Sacral Veins (vv. sacrales laterales) accompany the lateral sacral
arteries on the anterior surface of the sacrum and end in the hypogastric vein.
6. The Middle Hemorrhoidal Vein {v. hcrmorrhoidalis media) takes origin in the
hemorrhoidal plexus and receives tributaries from the bladder, prostate, and
seminal vesicle; it runs lateralward on the pelvic surface of the Levator ani to
end in the hypogastric vein.
The hemorrhoidal plexus (plexus hcemorrhoidalis) surrounds the rectum, and
communicates in front with the vesical plexus in the male, and the uterovaginal
plexus in the female. It consists of two parts, an internal in the submucosa, and an
external outside the muscular coat. The internal plexus presents a series of dilated
pouches which are arranged in a circle around the tube, immediately above the
anal orifice, and are connected by transverse branches.
The lower part of the external plexus is drained by the inferior hemorrhoidal
veins into the internal pudendal vein; the middle part by the middle hemorrhoidal
vein which joins the hypogastric vein ; and the upper part by the superior hemor-
rhoidal vein which forms the commencement of the inferior mesenteric vein,
a tributary of the portal vein. A free communication between the portal and sys-
temic venous systems is established through the hemorrhoidal plexus.
The veins of the hemorrhoidal plexus are contained in very loose, connective
tissue, so that they get less support from surrounding structures than most other
veins, and are less capable of resisting increased blood-pressure.
The pudendal plexus (plexus pudendalis; vesicoprostatic plexus) lies behind the
arcuate pubic ligament and the lower part of the symphysis pubis, and in front of
the bladder and prostate. Its chief tributary is the deep dorsal vein of the penis,
but it also receives branches from the front of the bladder and prostate. It com-
municates with the vesical plexus and with the internal pudendal vein and drains
into the vesical and hypogastric veins. The prostatic veins form a well-marked
prostatic plexus which lies partly in the fascial sheath of the prostate and partly
between the sheath and the prostatic capsule. It communicates with the pudendal
and vesical plexuses.
The vesical plexus (plexus resicalis) envelops the lower part of the bladder and
the base of the prostate and communicates with the pudendal and prostatic plexuses.
It is drained, by means of several vesical veins, into the hypogastric veins.
The Dorsal Veins of the Penis (vv. dorsales penis) are two in number, a superficial
and a deep. The superficial vein drains the prepuce and skin of the penis, and,
running backward in the subcutaneous tissue, inclines to the right or left, and opens
into the corresponding superficial external pudendal vein, a tributary of the great
saphenous vein. The deep vein lies beneath the deep fascia of the penis; it receives
the blood from the glans penis and corpora cavernosa penis and courses backward
in the middle line between the dorsal arteries; near the root of the penis it passes
between the two parts of the suspensory ligament and then through an aperture
between the arcuate pubic ligament and the transverse ligament of the pelvis,
and divides into two branches, which enter the pudendal plexus. The deep vein
also communicates below the symphysis pubis with the internal pudendal vein.
The uterine plexuses lie along the sides and superior angles of the uterus between
the two layers of the broad ligament, and communicate with the ovarian and
vaginal plexuses. They are drained by a pair of uterine veins on either side : these
THE VEINS OF THE ABDOMEN AND PELVIS
677
SUPERFICIAL DOR-
SAL VEIN
DORSAL ARTERY .DEEP DORSAL VEIN
CORPUS CAVERNOSUM.
arise from the lower part of the plexuses, opposite the external orifice of the uterus,
and open into the corresponding hypogastric vein.
The vaginal plexuses are placed at the sides of the vagina; they communicate
with the uterine, vesical, and hemorrhoidal plexuses, and are drained by the
vaginal veins, one on either side, into the hypogastric veins.
The common iliac veins {iw. iliacoe
communes) are formed by the union
of the external iliac and hypogastric
veins, in front of the sacroiliac artic-
ulation; passing obliquely upward
toward the right side, they end upon
the fifth lumbar vertebra, by uniting
with each other at an acute angle to
form the inferior vena cava. The
right common iliac is shorter than
the left, nearly vertical in its di-
rection, and ascends behind and then
lateral to its corresponding artery.
The left common iliac, longer than
the right and more oblique in its
course, is at first situated on the medial side of the corresponding artery, and then
behind the right common iliac. Each common iliac receives the iliolumbar, and
sometimes the lateral sacral veins. The left receives, in addition, the middle sacral
vein. No valves are found in these veins.
The Middle Sacral Veins {vv. sacrales mediales) accompany the corresponding
artery along the front of the sacrum, and join to form a single vein, which ends in
the left common iliac vein; sometimes in the angle of junction of the two iliac veins.
DEEP
FASCIA
bulbo-cavernous artery/ ._
—anterior branch i urethra
corVus
spongiosum
Fig. 588. — The penia in transverse section, showing the
bloodvessels. (Testut.)
TUBAL VESSELS
ANASTOMOSIS OF
FALLOPIAN
OS UTERI VAGINA CUT OPEN BEHIND
Fig. 589. — Vessels of the uterus and its appendages, rear view. (Testut.)
Peculiarities. — The left common iliac vein, instead of joining with the right in its usual posi-
tion, occasionally ascends on the left side of the aorta as high as the kidney, where, after receiving
the left renal vein, it crosses over the aorta, and then joins with the right vein to foim the vena
cava. In these cases, the two common iliacs are connected by a small communicating branch
at the spot where they are usually united.
The inferior vena cava (i'. cava inferior) (Fig. 577), returns to the heart the blood
from the parts below the diaphragm. It is formed by the junction of the two
common iliac veins, on the right side of the fifth lumbar vertebra. It ascends along
678 ANGIOLOGY
the front of the vertebral column, on the right side of the aorta, and, having reached
the liver, is continued in a groove on its posterior surface. It then perforates
the diaphragm between the median and right portions of its central tendon;
it subsequently inclines forward and medialward for about 2.5 cm., and, piercing
the fibrous pericardium, passes behind the serous pericardium to open into the
lower and back part of the right atrium. In front of its atrial orifice is a semilunar
valve, termed the valve of the inferior vena cava: this is rudimentary in the adult,
but is of large size and exercises an important function in the fetus (see page 540).
Relations. — The abdominal portion of the inferior vena cava is in relation in front, from below
upward, with the right common iliac artery, the mesentery, the right internal spermatic artery,
the inferior part of the duodenum, the pancreas, the common bile duct, the portal vein, and the
posterior surface of the hver; the last partly overlaps and occasionally completely surrounds it;
behind, with the vertebral column, the right Psoas major, the right crus of the diaphragm', the
right inferior phrenic, suprarenal, renal and lumbar arteries, right sjTnpathetic trunk and right
cehac ganglion, and the medial part of the right suprarenal gland; on the right side, with the
right kidney and ureter; on the left side, with the aorta, right crus of the diaphragm, and the
caudate lobe of the liver.
The thoracic portion is only about 2.5 cm. in length, and is situated partly inside and partly
outside the pericardial sac. The cxtrapcricardial part is separated from the right pleura and
lung by a fibrous band, named the right phrenicopericardiac ligament. This ligament, often
feebly marked, is attached below to the margin of the vena-caval opening in the diaphragm, and
above to the pericardium in front of and behind the root of the right lung. The intrapericardiac
part is very short, and is covered antero-laterally by the serous layer of the pericardium.
Peculiarities. — In Position. — This vessel is sometimes placed on the left side of the aorta,
as high as the left renal vein, and, after receiving this vein, crosses over to its usual position on
the right side; or it may be placed altogether on the left side of the aorta, and in such a case the
abdominal and thoracic viscera, together with the great vessels, are all transposed.
Point of Termination. — Occasionally the inferior vena cava joins the azygos vein, which is
then of large size. In such cases, the superior vena cava receives the whole of the blood from
the body before transmitting it to the right atrium, except the blood from the hepatic veins,
which passes directly into the right atrium.
Tributaries. — The inferior vena cava receives the following veins:
Lumbar. Renal. Inferior Phrenic.
Right Spermatic or Ovarian. Suprarenal. Hepatic.
The Lumbar Veins {vv. lumbales) four in number on each side, collect the blood
by dorsal tributaries from the muscles and integument of the loins, and by abdomi-
nal tributaries from the walls of the abdomen, where thev communicate with the
epigastric veins. At the vertebral column, they receive veins from the vertebral
plexuses, and then pass forward, around the sides of the bodies of the vertebrae,
beneath the Psoas major, and end in the back part of the inferior cava. The left
lumbar veins are longer than the right, and pass behind the aorta. The lumbar
veins are connected together by a longitudinal vein which passes in front of the
transverse processes of the lumbar vertebrae, and is called the ascending lumbar;
it forms the most frequent origin of the corresponding azygos or hemiazygos vein,
and serves to connect the common iliac, iliolumbar, and azygos or hemiazygos
veins of its own side of the body.
The Spermatic Veins {vi\ spermaticce) (Fig. 590) emerge from the back of the
testis, and receive tributaries from the epididymis; they unite and form a convo-
luted plexus, called the pampiniform plexus, which constitutes the greater mass of
the spermatic cord; the vessels composing this plexus are very numerous, and
ascend along the cord, in front of the ductus deferens. Below the subcutaneous
inguinal ring they unite to form three or four veins, which pass along the inguinal
canal, and, entering the abdomen through the abdominal inguinal ring, coalesce
to form two veins, which ascend on the Psoas major, behind the peritoneum, lying
one on either side of the internal spermatic artery. These unite to form a single
vein, which opens on the right side into the inferior vena cava, at an acute angle;
on the left side into the left renal vein, at a right angle. The spermatic veins
THE VEINS OF THE ABDOMEN AND PELVIS
679
are provided with valves.^ The left spermatic vein passes behind the iliac colon,
and is thus exposed to pressure from the contents of that part of the bowel.
The Ovarian Veins (w. ovariccp) correspond with the spermatic in the male; they
form a plexus in the broad ligament near the ovary and uterine tube, and communi-
cate with the uterine plexus. They end in the same way as the spermatic veins
in the male. Valves are occasionally found in these veins. Like the uterine veins,
they become much enlarged during pregnancy.
Fig. 590. — Spermatic veins. (Testut.)
The Renal Veins (vv. renales) are of large size, and placed in front of the renal
arteries. The left is longer than the right, and passes in front of the aorta, just
below the origin of the superior mesenteric artery. It receives the left spermatic
and left inferior phrenic veins, and, generally, the left suprarenal vein. It opens
into the inferior vena cava at a slightly higher level than the right.
The Suprarenal Veins {vv. siqjrarenales) are two in number: the right ends in the
inferior vena cava; the left, in the left renal or left inferior phrenic vein.
The Inferior Phrenic Veins {vv. phrenicoB inferiores) follow the course of the inferior
phrenic arteries; the right ends in the inferior veria cava; the left is often repre-
sented by two branches, one of which ends in the left renal or suprarenal vein,
while the other passes in front of the esophageal hiatus in the diaphragm and
opens into the inferior vena cava.
' Rivington has pointed out that valves are usually found at the orifices of both the right and left spermatic veins.
When no valves exist at the opening of the left spermatic vein into the left renal vein, valves are generally present in
the left renal vein within 6 mm from the orifice of the spermatic vein. — Journal of Anatomy and Physiology, vii, 163.
680
ANGIOLOGY
The Hepatic Veins (vv. hepaticce) commence in the substance of the liver, in the
terminations of the portal vein and hepatic artery, and are arranged in two groups,
upper and lower. The upper group usually consists of three large veins, which
converge toward the posterior surface of the liver, and open into the inferior
vena cava, while that vessel is situated in the groove on the back part of the liver.
The veins of the lower group vary in number, and are of small size; they come
from the right and caudate lobes. The hepatic veins run singly, and are in direct
contact with the hepatic tissue. They are destitute of valves.
Fig. 591. — The portal vein and its tributaries.
THE PORTAL SYSTEM OF VEINS (Fig. 591).
The portal system includes all the veins which drain the blood from the abdominal
part of the digestive tube (with the exception of the lower part of the rectum)
and from the spleen, pancreas, and gall-bladder. From these viscera the blood
is conveyed to the liver by the portal vein. In the liver this vein ramifies like an
artery and ends in capillary-like vessels termed sinusoids, from which the blood is
THE PORTAL SYSTEM OF VEINS 681
conveyed to the inferior vena cava by the hepatic veins. From this it will be seen
that the blood of the portal system passes through two sets of minute vessels,
viz., (a) the capillaries of the digestive tube, spleen, pancreas, and gall-bladder;
and (6) the sinusoids of the liver. In the adult the portal vein and its tributaries
are destitute of valves; in the fetus and for a short time after birth valves can be
demonstrated in the tributaries of the portal vein; as a rule they soon atrophy
and disappear, but in some subjects they persist in a degenerate form.
The portal vein (vena -porta;) is about 8 cm. in length, and is formed at the level
of the second lumbar vertebra by the junction of the superior mesenteric and lienal
veins, the union of these veins taking place in front of the inferior vena cava and
behind the neck of the pancreas. It passes upward behind the superior part of
the duodenum and then ascends in the right border of the lesser omentum to the
right extremity of the porta hepatis, where it divides into a right and a left branch,
which accompany the corresponding branches of the hepatic artery into the sub-
stance of the liver. In the lesser omentum it is placed behind and between the
common bile duct and the hepatic artery, the former lying to the right of the latter.
It is surrounded by the hepatic plexus of nerves, and is accompanied by numerous
lymphatic vessels and some lymph glands. The right branch of the portal vein
enters the right lobe of the liver, but before doing so generally receives the cystic
v'ein. The left branch, longer but of smaller caliber than the right, crosses the left
sagittal fossa, gives branches to the caudate lobe, and then enters the left lobe of
the liver. As it crosses the left sagittal fossa it is joined in front by a fibrous cord,
the ligamentum teres {obliterated umbilical vein), and is united to the inferior vena
cava by a second fibrous cord, the ligamentum venosum (obliterated ductus venosus).
Tributaries. — The tributaries of the portal vein are:
Lienal. Pyloric.
Superior Mesenteric. Cystic.
Coronary. Parumbilical.
The Lienal Vein {v. lienalis; splenic vein) commences by five or six large branches
which return the blood from the spleen. These unite to form a single vessel, which
passes from left to right, grooving the upper and back part of the pancreas, below
the lineal artery, and ends behind the neck of the pancreas by uniting at a right
angle with the superior mesenteric to form the portal vein. The lienal vein is
of large size, but is not tortuous like the artery.
Tributaries. — The lineal vein receives the short gastric veins, the left gastro-
epiploic vein, the pancreatic veins, and the inferior mesenteric veins.
The short gastric veins {vv. gastricoe breves) ,io\iTOT five in number, drain the fundus
and left part of the greater curvature of the stomach, and pass between the two
layers of the gastrolienal ligament to end in the lienal vein or in one of its large
tributaries.
The left gastroepiploic vein {v. gastroepiploica sinistra) receives branches from
the antero-superior and postero-inferior surfaces of the stomach and from the greater
omentum; it runs from right to left along the greater curvature of the stomach
and ends in the commencement of the lienal vein.
The pancreatic veins (vv. pancreaticcp) consist of several small vessels which drain
the body and tail of the pancreas, and open into the trunk of the lienal vein.
The inferior mesenteric vein (r. mesenterica inferior) returns blood from the rectum
and the sigmoid, and descending parts of the colon. It begins in the rectum as
the superior hemorrhoidal vein, which has its origin in the hemorrhoidal plexus,
and through this plexus communicates with the middle and inferior hemor-
rhoidal veins. The superior hemorrhoidal vein leaves the lesser pelvis and crosses
the left common iliac vessels with the superior hemorrhoidal artery, and is con-
tinued upward as the inferior mesenteric vein. This vein lies to the left of its
artery, and ascends behind the peritoneum and in front of the left Psoas major;
682 ANGIOLOGY
it then passes behind the body of the pancreas and opens into the lienal vein;
sometimes it ends in the angle of union of the lienal and superior mesenteric veins.
Tributaries. — The inferior mesenteric vein receives the sigmoid veins from the
sigmoid colon and iliac colon, and the left colic vein from the descending colon and
left colic flexure.
The Superior Mesenteric Vein {r. mesenierica siiperior) returns the blood from the
small intestine, from the cecum, and from the ascending and transverse portions
of the colon. It begins in the right iliac fossa by the union of the veins which drain
the terminal part of the ileum, the cecum, and vermiform process, and ascends
between the two layers of the mesentery on the right side of the superior mes-
enteric artery. In its upward course it passes in front of the right ureter, the
inferior vena ca\'a, the inferior part of the duodenum, and the lower portion of
the head of the pancreas. Behind the neck of the pancreas it unites with the lienal
vein to form the portal vein.
Tributaries. — Besides the tributaries which correspond with the branches of the
superior mesenteric artery, viz., the intestinal, ileocolic, right colic, and middle colic
veins, the superior mesenteric vein is joined by the right gastroepiploic and pan-
creaticoduodenal veins.
The right gastroepiploic vein {v. gasiroepiploica dexira) receives branches from the
greater omentum and from the lower parts of the antero-superior and postero-
inferior surfaces of the stomach; it runs from left to right along the greater curva-
ture of the stomach between the two layers of the greater omentum.
The pancreaticoduodenal veins (ct. pancreaticoduodenales) accompany their corre-
sponding arteries; the lower of the tw^o frequently joins the right gastroepiploic
vein.
The Coronary Vein {r. coronaria reniriculi; gastric rein) derives tributaries from
both surfaces of the stomach; it runs from right to left along the lesser curvature
of the stomach, between the two layers of the lesser omentum, to the esophageal
opening of the stomach, where it receives some esophageal veins. It then turns
backward and passes from left to right behind the omental bursa and ends in the
portal vein.
The Pyloric Vein is of small size, and runs from left to right along the pyloric
portion of the lesser curvature of the stomach, between the two layers of the lesser
omentum, to end in the portal vein.
The Cystic Vein (v. cystica) drains the blood from the gall-bladder, and, accom-
panying the cystic duct, usually ends in the right branch of the portal vein.
Parumbilical Veins(i'r. parumbilicales) . — In the course of the ligamentum teres
of the liver and of the middle umbilical ligament, small veins (parumbilical) are
found which establish an anastomosis between the veins of the anterior abdominal
wall and the portal, hypogastric, and iliac veins'. The best marked of these small
veins is one which commences at the umbilicus and runs backward and upward
in, or on the surface of, the ligamentum teres between the layers of the falciform
ligament to end in the left portal vein.
Collateral venous circulation to relieve portal obstruction in the liver may be effected by
communications between (a) the gastric veins and the esophageal veins which often project
as a varicose bunch into the stomach, emptying themselves into the hemiazygos vein; (6) the
veins of the colon and duodenum and the left renal vein; (c) the accessory portal system of
Sappey, branches of which pass in the round and falciform Hgaments (particularly the latter)
to unite with the epigastric and internal mammary veins, and through the diaphragmatic
veins with the azygos; a single large vein, shown to be a parumbihcal vein, may pass from
the hilus of the liver by the round hgament to the umbihcus, producing there a bunch of
prominent varicose veins known as the caput medustv; (d) the veins of Retzius, which connect
the intestinal veins with the inferior vena cava and its retroperitoneal branches; (e) the inferior
mesenteric veins, and the hemorrhoidal veins that open into the hypogastrics; (/) very rarely
the ductus venosus remains patent, affording a direct connection between the portal vein and
the inferior vena cava.
THE LYMPHATIC SYSTEM.
THE lymphatic system consists (1) of complex capillary networks which collect the
lymph in the various organs and tissues; (2) of an elaborate system of collecting
vessels which conduct the lymph from the capillaries to the large veins of the neck
at the junction of the internal jugular and subekA-ian veins, where the lymph is
poured into the blood stream; and (3) hTnph glands or nodes which are inter-
spaced in the pathways of the collecting vessels filtering the hinph as it passes
through them and contributing hnnphocytes to it. The Ijanphatic capillaries and
collecting vessels are lined throughout by a continuous layer of endothelial cells,
forming thus a closed system. The lymphatic vessels of the small intestine receive
the special designation of lacteals or chyliferous vessels ; they differ in no respect
from the lymphatic vessels generally excepting that during the process of digestion
they contain a milk-white fluid, the chyle.
Lejt innominate
Jugular (i/mph-sac
Right innominate
S iperior vena cava
Prerenal 'part of
inferior vena cava
Postrenal part of
inferior vena cava
Posterior lymph-sac
Internal jugular
External jugular
Duct of Cuvier
— Left Cardinal
Cisterna chyli
Left renal
Retro- peritoneal
lymph-sac
Left common iliac
External iliac
Hypogastric
Fig. 592. — Scheme showing relative positions of primary lymph sacs based on the description given by
Florence Sabin.
The Development of the Lymphatic Vessels. — The lymphatic system begins as
a series of sacs^ at the points of junction of certain of the embryonic veins. These
lymph-sacs are developed by the confluence of numerous venous capillaries, which
at first lose their connections with the venous system, but subsequently, on the
formation of the sacs, regain them. The lymphatic system is therefore develop-
mentally an oft'shoot of the venous system, and the lining walls of its vessels are
always endothelial.
In the human embryo the lymph sacs from which the lymphatic vessels are
1 Sabin, Am. Jour. Anat., 1909, vol. ix; Johns Hopkins Hospital Reports, 1913.
(683)
684 ANGIOLOGY
derived are six in number; two paired, the jugular and the posterior lymph-sacs;
and two unpaired, the retroperitoneal and the cisterna chy.'i. In lower mammals
an additional pair, subclavian, is present, but in the human embryo these are
merely extensions of the jugular sacs.
The position of the sacs is as follows: (1) jugular sac, the first to appear, at
the junction of the subclavian vein with the primitive jugalar; (2) posterior sac,
at the junction of the iliac vein with the cardinal; (3) retroperitoneal, in the root
of the mesentery near the suprarenal glands; (4) cisterna chyli, opposite the third
and fourth lumbar vertebrae (Fig. 592), From the lymph-sacs the lymphatic
vessels bud out along fixed lines corresponding more or less closely to the course
of the embryonic bloodvessels. Both in the body-wall and in the wall of the
intestine, the deeper plexuses are the first to be developed; by continued growth
of these the vessels in the superficial layers are gradually/ formed. The thoracic
duct is probably formed from anastomosing outgrowths irom the jugular sac and
cisterna chyli. At its connection with the cisterna chyli it is at first double, but
the two vessels soon join.
All the lymph-sacs except the cisterna chyli are, at a later stage, divided up by
slender connective tissue bridges and transformed into groups of lymph glands.
The lower portion of the cisterna chyli is similarly converted, but its upper portion
remains as the adult cisterna.
Lymphatic Capillaries. — The complex capillary plexuses which consist of a
single layer of thin flat endothelial cells lie in the connective-tissue spaces in the
various regions of the body to which they are distributed and are bathed by the
intercellular tissue fluids. Two views are at present held as to the mode in which
the lymph is formed : one being by the physical processes of filtration, diffusion, and
osmosis, and the other, that in addition to these physical processes the endothelial
cells have an active secretory function. The colorless liquid hTnph has about the
same composition as the blood plasma. It contains many lymphocytes and fre-
quently red blood corpuscles. Granules and bacteria are also taken up by the lymph
from the connective-tissue spaces, partly by the action of hinphocytes which pass
into the l>Tnph between the endothelial cells and partly by the direct passage of the
granules through the endothelial cells.
The l^Tnphatic capillary plexuses vary greatly in form; the anastomoses are
usually numerous; blind ends or cul-de-sacs are especially common in the intestinal
villi, the dermal papilla? and the filiform papillae of the tongue. The plexuses are
often in two layers: a superficial and a deep, the superficial being of smaller caliber
than the deep. The caliber, however, varies greatly in a given plexus from a few
micromillimeters to one millimeter. The capillaries are without valves.
Distribution. — The Skin. — Lymphatic capillaries are abundant in the dermis
where they form superficial and deep plexuses, the former sending blind ends into
the dermal papilla?. The plexuses are especially rich over the palmar surface of the
hands and fingers and over the plantar surface of the feet and toes. The epidermis
is without capillaries. The conjunctiva has an especially rich plexus.
The stihcntaneons tissue is without capillaries.
The tendons of striated muscle and muscle sheaths are richly supplied. In muscle,
however, their existence is still disputed.
The ijeriosteum of bone is richly supplied and they have been described in the
Haversian canals. They are absent in cartilage and probabl}' in bone marrow.
The joint capsules are richly supplied with l;\Tnphatic capillaries, they do not,
however, open into the joint cavities.
Beneath the mesothelium lining of the pleural, peritoneal and pericardial cavities
are rich plexuses; they do not open into these cavities.
The alimentary canal is supplied with rich plexuses beneath the epithelium, often
as a superficial plexus in the mucosa and a deeper submucosal plexus. Cul-de-sacs
LYMPHATIC CAPILLARIES
685
extend into the filiform papillae of the tongue and the villi of the small intestine.
Those portions of the alimentary canal covered by peritoneum, have in addition
a subserous IjTnphatic capillary plexus beneath the mesothelium.
Fig. 593. — Lymph capillaries of the human conjunctiva: a, conjunctiva comese; 6, conjunctiva sclerotica.
X 40 dia. (Teichmann.)
Fig. 594.— Lymph capillaries from the human scrotum, showing also transition from capillaries to the collecting
vessels a. a. X 20 dia. (Teichmann.)
The salivary glands are supplied with hmphatic capillaries.
The liver has a rich subserous plexus in the capsule and also extensive plexuses
» which accompany the hepatic artery and portal vein. The IxTnphatic capillaries
have not been followed into the liver lobules. The bTuph from the liver forms a
686
ANGIOLOGY
large part of that which flows through the thoracic duct. The gall-bladder and bile
ducts have rich subepithehal plexuses and the former a subserous plexus.
The syleen has a rich subserous set and a capsular set of lymphatic capillaries
Their presence in the parench>Tna is uncertain.
Fig. 595. — Lymph capillaries of the cutis from the inner border of the sole of the human foot, a, a, outer layer;
h, 6. inner layer. X 30 dia. (Teichniann.)
The nasal cavity has extensive capillary plexuses in the mucosa and submucosa.
The trachea and bronchi have plexuses in the mucosa and submucosa but the
smaller bronchi have only a single layer. The capillaries do not extend to the
air-cells. The plexuses around the smaller bronchi connect with the rich subserous
plexus of the lungs in places where the veins reach the surface.
Fig. 596. — Vertical section through human tongue; a. a, blind lymph capillaries in the filiform papillae with the under-
lying lymphatic plexus. X 45. (Teichniann.)
Lymphatics have been described in the thyroid gland and in the thymus.
The adrenal has a superficial plexus divided into two layers, one in the loose tissue
about the gland and the other beneath the capsule. Capillaries have also been
described within the parenchyma.
STRUCTURE OF LYMPHATIC VESSELS 687
The kidney is supplied with a coarse subserous plexus and a deeper plexus of
finer capillaries in the capsule. Lymphatics have been described within the sub-
stance of the kidney surrounding the tubules.
The urinary bladder has a rich plexus of lymphatic capillaries just beneath the
epithelial lining, also a subserous set which anastomoses with the former through
the muscle layer. The submucous plexus is continuous with the submucous plexus
of the lu-ethra.
The prostate has a rich lymphatic plexus surrounding the gland and a wide-
meshed subcapsular plexus.
The testis has a rich superficial plexus beneath the tunica albuginea. The pres-
ence of deep lymphatics is disputed.
The 7derus is provided with a subserous plexus, the deeper lymphatics are
uncertain. Subepithelial plexuses are found in the vagina.
The ovary has a rich superficial plexus and a deep interstitial plexus.
The heart has a rich subserous plexus beneath the epicardium. L\Tnphatic
capillaries have also been described beneath the endocardium and throughout
the muscle.
Lymphatic capillaries are probably absent in the central nervous system, the
meninges, the eyeball (except the conjunctiva), the orbit, the internal ear, within
striated muscle, the liver lobule, the spleen pulp and kidney parenchyma. They
are entirely absent in cartilage. In many places further investigation is needed.
Lymphatic Vessels. — The lymphatic vessels are exceedingly delicate, and their
coats are so transparent that the fluid they contain is readily seen through them.
They are interrupted at intervals by constrictions, which give them a knotted
or beaded appearance; these constrictions correspond to the situations of valves
in their interior. Lymphatic vessels have been found in nearly every texture
and organ of the body which contains bloodvessels. Such non-vascular structures
as cartilage, the nails, cuticle, and hair have none, but with these exceptions it is
probable that eventually all parts will be found to be permeated by these vessels.
Structure of Lymphatic Vessels. — The larger lymphatic vessels are each composed of three
coats. The internal coat is thin, transparent, slightly elastic, and consists of a layer of elongated
endothehal cells with wavy margins by which the contiguous cells are dovetailed into one another;
the cells are supported on an elastic membrane. The middle coat is composed of smooth muscular
and fine elastic fibers, disposed in a transverse direction. The external coat consists of connective
tissue, intermixed with smooth muscular fibers longitudinally or obliquely disposed; it forms
a protective covering to the other coats, and serves to connect the vessel with the neighboring
structures. In the smaller vessels there are no muscular or elastic fibers, and the wall consists
only of a connective-tissue coat, hned by endothelium. The thoracic duct has a more complex
structure than the other lymphatic vessels; it presents a distinct subendothelial layer of branched
corpuscles, similar to that found in the arteries; in the middle coat there is, in addition to the
muscular and elastic fibers, a layer of connective tissue with its fibers arranged longitudinally.
The lymphatic vessels are supplied by nutrient vessels, which are distributed to their outer
and middle coats; and here also have been traced many non-medullated nerves in the form of
a fine plexus of fibrils.
The valves of the lymphatic vessels are formed of thin layers of fibrous tissue covered on both
surfaces by endothehum which presents the same arrangement as on the valves of veins (p. 501).
In form the valves are semilunar; they are attached by their convex edges to the wall of the
vessel, the concave edges being free and directed along the course of the contained current.
Usually two such valves, of equal size, are found opposite one another; but occasionally excep-
tions occur, especially at or near the anastomoses of lymphatic vessels. Thus, one valve may
be of small size and the other increased in proportion.
In the lymphatic vessels the valves are placed at much shorter intervals than in the veins.
They are most numerous near the lymph glands, and are found more frequently in the lymphatic
vessels of the neck and upper extremity than in those of the lower extremity. The wall of
the lymphatic vessel immediately above the point of attachment of each segment of a valve is
expanded into a pouch or sinus which gives "to these vessels, when distended, the knotted or
beaded appearance already referred to. Valves are wanting in the vessels composing the plexi-
form net-work in which the lymphatic vessels usually originate on the surface of the body.
688
ANGIOLOGY
Ljmapn Glands (lymphoglandulcp) . — The lymph glands are small oval or bean-
shaped bodies, situated in the course of lymphatic and lacteal vessels so that the
lymph and chyle pass through them on their way to the blood. Each generally
presents on one side a slight depression — thehilus — through which the bloodvessels
enter and leave the interior. The efferent lymphatic vessel also emerges from the
gland at this spot, while the afferent vessels enter the organ at different parts of
the periphery. On section (Fig. 597) a lymph gland displays two different struc-
tures: an external, of lighter color — the cortical; and an internal, darker — the
medullary. The cortical structure does not form a complete investment, but is
deficient at the hilus, where the medullary portion reaches the surface of the
gland; so that the efferent vessel is derived directly from the medullary structures,
while the afferent vessels empty themselves into the cortical substance.
Lymphoid
tissue in
cortex
Svbcapsular
lymph-path
Lymph-path
in medulla
Fig. 597. — Section of small lymph gland of rabbit. X 100.
Structure of Lymph Glands. — A lymph gland consists of (1) a fibrous envelope, or capsule,
from which a frame-work of processes {traheculce) proceeds inward, imperfectly dividing the
gland into open spaces freely communicating with each other; (2) a quantity of lymphoid tissue
occupying these spaces without completely filling them; (3) a free supply of bloodvessels, which
are supported in the trabeculse; and (4) the afferent and efferent vessels communicating through
the lymph paths in the substance of the gland. The nerves passing into the hilus are few in
number and are chiefly distributed to the bloodvessels supplying the gland.
The capsule is composed of connective tissue with some plain muscle fibers, and from its internal
surface are given off a number of membranous processes or trabeculae, consisting, in man, of
connective tissue, with a small admixture of plain muscle fibers; but in many of the lower animals
composed almost entirely of involuntary muscle. They pass inward, radiating toward the center
of the gland, for a certain distance — that is to say, for about one-third or one-fourth of the space
between the circumference and the center of the gland. In some animals they are sufficiently
well-marked to divide the peripheral or cortical portion of the gland into a number of compart-
ments (so-called foUicles), but in man this arrangement is not obvious. The larger trabeculae
springing from the capsule break up into finer bands, and these interlace to form a mesh-work
in the central or medullary portion of the gland. In these spaces formed by the interlacing
trabeculae is contained the proper gland substance or lymphoid tissue. The gland pulp does
not, however, completely fill the spaces, but leaves, between its outer margin and the enclosing
trabeculae, a channel or space of uniform width throughout. This is termed the lymph path
STRUCTURE OF LYMPH GLANDS
689
or lymph sihus (Fig. 507). Running across it are a number of finer trabecula; of retiform con-
nective tissue, the fibers of which are, for the most part, covered by ramifying cells.
On account of the peculiar arrangement of the frame-work of the organ, the gland pulp in the
cortical portion is disposed in the form of nodules, and in the medullary part in the form of rounded
cords. It consists of ordinary lymphoid tissue (Fig. 598), being made up of a delicate net-work
of retiform tissue, which is continuous with that in the lymph paths, but marked off from it
by a closer reticulation; it is probable, moreover, that the reticular tissue of the gland pulp and
the lymph paths is continuous with that of the trabeculae, and ultimately with that of the capsule
of the gland. In its meshes, in the nodules and cords of lymphoid tissue, are closely packed
lymph corpuscles. The gland pulp is traversed by a dense plexus of capillary bloodvessels.
The nodules or follicles in the cortical portion of the gland frequently show, in their centers,
areas where karyokinetic figures indicate a division of the lymph corpuscles. These areas are
termed germ centers. The cells composing them have more abundant protoplasm than the
peripheral cells.
The afferent vessels, as stated above, enter at all parts of the periphery of the gland, and after
branching and forming a dense plexus in the substance of the capsule, open into the lymph sinuses
of the cortical part. In doing this they lose all their coats except their endothelial lining, which
is continuous with a layer of similar cells lining the lymph paths. In like manner the efferent
vessel commences from the lymph sinuses of the medullary portion. The stream of lymph carried
to the glajid by the afferent vessels thus passes through the plexus in the capsule to the lymph
Fig. 598. — Lymph gland tissue. Highly magnified, a, Trabeculse. b. Small artery in substance of same.
c. Lymph paths, d. Lymph corpuscles, e. Capillary plexus.
paths of the cortical portion, where it is exposed to the action of the gland pulp; flowing through
these it enters the paths or sinuses of the medullary portion, and finally emerges from the hilus
by means of the efferent vessel. The stream of lymph in its passage through the lymph sinuses
is much retarded by the presence of the reticulum, hence morphological elements, either normal
or morbid, are easily arrested and deposited in the sinuses. Many lymph corpuscles pass with
the efferent lymph stream to join the general blood stream. The arteries of the gland enter
at the hilus, and either go at once to the gland pulp, to break up into a capillary plexus, or else
run along the trabeculae, partly to supply them and partly running across the lymph paths,
to assist in forming the capillary plexus of the gland pulp. This plexus traverses the lymphoid
tissue, but does not enter into the lymph sinuses. From it the veins commence and emerge
from the organ at the same place as that at which the arteries enter.
The lymphatic vessels are arranged into a superficial and a deep set. On the
surface of the body the superficial lymphatic vessels are placed immediately
beneath the integument, accompanying the superficial veins; they join the deep
lymphatic vessels in certain situations by perforating the deep fascia. In the
interior of the body they lie in the submucous areolar tissue, throughout the whole
length of the digestive, respiratory, and genito-urinary tracts; and in the subserous
tissue of the thoracic and abdominal walls. Plexiform networks of minute lym-
phatic vessels are found interspersed among the proper elements and bloodvessels
of the several tissues; the vessels Composing the net-work, as well as the meshes
44
690 ANGJOLOGY
betw^een them, are touch larger than those of the capillary plexus. From these
net-works small vessels emerge, which pass, either to a neighboring gland, or to
join some larger lymphatic trunk. The deep lymphatic vessels, fewer in number,
but larger than the superficial, accompany the deep bloodvessels. Their mode of
origin is probably similar to that of the superficial vessels. The lymphatic vessels
of any part or organ exceed the veins in number, but in size they are much smaller.
Their anastomoses also, especially those of the large trunks, are more frequent,
and are effected by vessels equal in diameter to those which they connect, the con-
tinuous trunks retaining the same diameter.
Hemolymph nodes or glands and hemal nodes which are so abundant in some
mammals are probably not present in man.
Lymph. — L^^nph, found only in the closed l.Mnphatic vessels, is a transparent,
colorless, or slightly yellow, watery fluid of specific gravity about 1.015; it closely
resembles the blood plasma, but is more dilute. When it is examined under the
microscope, leucoc}i;es of the l^^nphoc^'te class are found floating in the transparent
fluid ; they are always increased in number after the passage of the hmph through
h-mphoid tissue, as in hTnph glands. Lymph should be distinguished from "tissue
fluid"^ which is found outside the hniphatic vessels in the tissue spaces.
THE THORACIC DUCT.
The thoracic duct {ductus thoracicus) (Fig. 599) conveys the greater part of the
lymph and chyle into the blood. It is the common trunk of all the lymphatic
vessels of the body, excepting those on the right side of the head, neck, and thorax,
and right upper extremity, the right lung, right side of the heart, and the convex
surface of the liver. In the adult it varies in length from 38 to 45 cm. and extends
from the second lumbar vertebra to the root of the neck. It begins in the abdomen
by a triangular dilatation, the cistema chyli, which is situated on the front of the
body of the second lumbar vertebra, to the right side of and behind the aorta,
by the side of the right crus of the diaphragm. It enters the thorax through the
aortic hiatus of the diaphragm, and ascends through the posterior mediastinal
cavity between the aorta and azygos vein. Behind it in this region are the vertebral
column, the right intercostal arteries, and the hemiazygos veins as they cross to
open into the azj-gos vein; in front of it are the diaphragm, esophagus, and peri-
cardium, the last being separated from it by a recess of the right pleural cavity.
Opposite the fifth thoracic vertebra, it inclines toward the left side, enters the supe-
rior mediastinal cavity, and ascends behind the aortic arch and the thoracic part
of the left subclavian artery and between the left side of the esophagus and the
left pleura, to the upper orifice of the thorax. Passing into the neck it forms an
arch which rises about 3 or 4 cm. above the clavicle and crosses anterior to the
subclavian arter}^, the vertebral artery and vein, and the thyrocervical trunk or
its branches. It also passes in front of the phrenic nerve and the medial border
of the Scalenus anterior, but is separated from these two structures by the pre-
vertebral fascia. In front of it are the left common carotid artery, vagus nerve,
and internal jugular vein; it ends by opening into the angle of junction of the left
subclavian vein with the left internal jugular vein. The thoracic duct, at its com-
mencement, is about equal in diameter to a goose-quill, but it diminishes consid-
erably in caliber in the middle of the thorax, and is again dilated just before its
termination. It is generally flexuous, and constricted at intervals so as to present
a varicose appearance. Not infrequently it divides in the middle of its course into
two vessels of unequal size which soon reunite, or into several branches which form
' Sabin, Harvey Lecture, Series ix. New York, 1915-16.
THE THORACIC DUCT
691
Right
lipnphatic
duct
Posterior ]
intercostal C
glands )
a plexiform interl.acement. It occasionally divides at its upper part into two
branches, right and left; the left ending in the usual manner, while the right opens
into the right subclavian vein, in
connection with the right lymphatic ^ ,M Fi A>-"
duct. The thoracic duct has several
valves; at its termination it is pro-
vided with a pair, the free borders
of which are turned toward the vein,
so as to prevent the passage of
venous blood into the duct.
The cisterna chyli (receptaculum
chyli) (Fig. 600) receives the two
lumbar lymphatic trunks, right and
left, and the intestinal lymphatic
trunk. The lumbar trunks are formed
by the union of the efferent vessels
from the lateral aortic lymph glands.
They receive the lymph from the
lower limbs, from the walls and
viscera of the pelvis, from the kid-
neys and suprarenal glands and the
deep lymphatics of the greater part
of the abdominal wall. The intes-
tinal trunk receives the lymph from
the stomach and intestine, from the
pancreas and spleen, and from the
lower and front part of the liver.
Tributaries. — Opening into the
commencement of the thoracic duct,
on either side, is a descending trunk
from the posterior intercostal lymph
glands of the lower six or seven in-
tercostal spaces. In the thorax the
duct is joined, on either side, by a
trunk which drains the upper lumbar
lymph glands and pierces the crus
of the diaphragm. It also receives
the efferents from the posterior
mediastinal lymph glands and from
the posterior intercostal lymph
glands of the upper six left spaces.
In the neck it is joined by the left
jugular and left subclavian trunks,
and sometimes by the left broncho-
mediastinal trunk; the last-named,
however, usually opens indepen-
dently into the junction of the left
subclavian and internal jugular
veins.
The right lymphatic duct {ductus lymphaticus dexter) (Fig. 601), about 1.25 cm.
in length, courses along the medial border of the Scalenus anterior at the root of
the neck and ends in the right subclavian vein, at its angle of junction with the right
internal jugular vein. Its orifice is guarded by two semilunar valves, which prevent
the passage of venous blood into the duct.
Lumbar glands
Fig. 599. — The thoracic and right lymphatic ducts.
692
ANGIOLOGY
Tributaries. — The right lymphatic duct receives the lymph from the right side
of the head and neck through the right jugular trunk ; from the right upper extremity
through the right subclavian trunk; from the right side of the thorax, right lung,
— a
..h
-•d
■ c
■h
• e
■ g
--•-/
c
Fig. 600. — Modes of origin of thoracic duct. (Poirier and Charpy.) a. Thoracic duct, a' . Cisterna chyli. 6, c
Efferent trunks from lateral aortic glands, d. An efferent vessel which pierces the left crus of the diaphragm, c. f.
Lateral aortic glands, h. Retroaortic glands, i. Intestinal trunk, j. Descending branch from intercostal lymphatics.
right side of the heart, and part of the convex surface of the liver, through the
right bronchomediastinal trunk. These three collecting trunks frequently open
separately in the angle of union of the two veins.
Fig. 601. — Terminal collecting trunks of right side. o. Jugular trunk, b. Subclavian trunk, c. Broncho-
mediastinal trunk, d. Right lymphatic trunk, e. Gland of internal mammary chain. /. Gland of deep cervical
chain. (Poirier and Charpy.)
THE LYMPHATICS OF THE HEAD, FACE, AND NECK.
The Lymph Glands of the Head (Fig. 602).
The lymph glands of the head are arranged in the following groups:
Occipital. Facial.
Posterior Auricular. Deep Facial.
Anterior Auricular. Lingual.
Parotid. Retropharyngeal.
The occipital glands (lyynphoglanduloE occipitales), one to three in number, are
placed on the back of the head close to the margin of the Trapezius and resting
on the insertion of the Semispinalis capitis. Their afferent vessels drain the occipi-
tal region of the scalp, while their efferents pass to the superior deep cervical
glands.
THE LYMPH GLANDS OF THE HEAD
693
The posterior auricular glands {lym-phoglandulcp auriculares; mastoid glands),
usually two in number, are situated on the mastoid insertion of the Sternocleido-
mastoideus, beneath the Aurieularis posterior. Their afferent vessels drain the
posterior part of the temporoparietal region, the upper part of the cranial surface
of the auricula or pinna, and the back of the external acoustic meatus; their
efferents pass to the superior deep cervical glands.
Posterior
auric^ilar
glands
Occipital
glands
Superficial, cervical
glands
Maxillary glands
Parotid glands
Buccinator glands
Supramandihular
glands
Submaxillary
glands
iSvbmental glands
Inferior deep
cervical glands
Fig. 602. — Superficial lymph glanda and lymphatic vessels of head and neck.
The anterior auricular glands {lymphoglandulw auricidares anteriores; superficial
parotid or preauricular glands), from one to three in number, lie immediately in
front of the tragus. Their afferents drain the lateral surface of the auricula and the
skin of the adjacent part of the temporal region; their efferents pass to the superior
deep cervical glands.
The parotid glands {lymphoglandidcp parotidexr), form two groups in relation
with the parotid salivary gland, viz., a group imbedded in the substance of the gland,
and a group of subparotid glands lying on the lateral w^all of the pharynx. Occa-
sionally small glands are found in the subcutaneous tissue over the parotid gland.
Their afferent vessels drain the root of the nose, the eyelids, the frontotemporal
region, the external acoustic meatus and the tympanic cavity, possibly also the
posterior parts of the palate and the floor of the nasal cavity. The efferents of
these glands pass to the superior deep cervical glands. The afferents of the sub-
694
ANGIOLOGY
parotid glands drain the nasal part of the pharynx and the posterior parts of the
nasal cavities; their efferents pass to the superior deep cervical glands.
The facial glands comprise three groups: (o) infraorbital or maxillary, scattered
over the infraorbital region from the groove between the nose and cheek to the
zygomatic arch; (6) buccinator, one or more placed on the Buccinator opposite the
angle of the mouth; (c) supramandibular, on the outer surface of the mandible,
in front of the Masseter and in contact ^Yith the external maxillary artery and
anterior facial vein. Their efferent vessels drain the eyelids, the conjunctiva,
and the skin and mucous membrane of the nose and cheek; their efferents pass to
the submaxillary glands.
The deep facial glands (lymphoglandul(F faciales profunda; internal maxillary
glands) are placed beneath the ramus of the mandible, on the outer surface of the
Pterygoideus externus, in relation to the internal maxillary artery. Their afferent
vessels drain the temporal and infratemporal fossae and the nasal part of the pharynx
their efferents pass to the superior deep cervical glands.
The lingual glands (lymphoglandulo' linguales) are two or three small nodules
lying on the Hyoglossus and under the Genioglossus. They form merely glandular
substations in the course of the lymphatic vessels of the tongue.
Afferent vessel to deep
cervical glands
Glandular nodule
Gland of deep cervical
chain.
Efferent vessels of retro-
pharyngeal glands
Fig. 603. — Lymphatics of pharj^nx. (Poirier and Charpy.
The retropharyngeal glands (Fig. 603), from one to three in number, lie in the
buccopharyngeal fascia, behind the upper part of the pharynx and in front of the
arch of the atlas, being separated, however, from the latter by the Longus capitis.
Their afferents drain the nasal cavities, the nasal part of the pharynx, and the
auditory tubes; their efferents pass to the superior deep cervical glands.
The lymphatic vessels of the scalp are divisible into (a) those of the frontal region,
which terminate in the anterior auricular and parotid glands; (6) those of the
temporoparietal region, which end in the parotid and posterior auricular glands;
and (c) those of the occipital region, which terminate partly in the occipital
glands and partly in a trunk which runs down along the posterior border of the
Sternocleidomastoideus to end in the inferior deep cervical glands.
The lymphatic vessels of the auricula and external acoustic meatus are also divisible
into three groups: (a) an anterior, from the lateral surface of the auricula and
anterior wall of the meatus to the anterior auricular glands; (b) a posterior, from
the margin of the auricula, the upper part of its cranial surface, the internal surface
THE LYMPH GLANDS OF THE HEAD
695
and posterior \yall of the meatus to the posterior auricular and superior deep cervical
glands; (c) an inferior, from the floor of the meatus and from the lobule of the auric-
ula to the superficial and superior deep cervical glands.
The lymphatic vessels of the face (Fig. 604) are more numerous than those of the
scalp. Those from the eyelids and conjunctiva terminate partly in the submaxillary
but mainly in the parotid glands. The vessels from the posterior part of the cheek
also pass to the parotid glands, while those from the anterior portion of the cheek,
the side of the nose, the upper lip, and the lateral portions of the lower lip end in
the submaxillary glands. The deeper vessels from the temporal and infratemporal
fossae pass to the deep facial and superior deep cervical glands. The deeper vessels
of the cheek and lips end, like the superficial, in the submaxillary glands. Both
superficial and deep vessels of the central part of the lower lip run to the submental
glands.
Parotid gland.
Superficial cervi-
cal glands
Facial glands
-Submaxillary glands
Deep cervical glands
Fia. 604. — The lymphatics of the face. (After Kuttner.)
Lymphatic Vessels of the Nasal Cavities. — ^Those from the anterior parts of the
nasal cavities communicate with the vessels of the integument of the nose and
end in the submaxillary glands; those from the posterior two-thirds of the nasal
cavities and from the accessory air sinuses pass partly to the retropharyngeal
and partly to the superior deep cervical glands.
Lymphatic Vessels of the Mouth. — ^The vessels of the gums pass to the submaxillary
glands; those of the hard palate are continuous in front with those of the upper
gum, but pass backward to pierce the Constrictor pharyngis superior and end in
the superior deep cervical and subparotid glands; those of the soft palate pass
backward and lateral ward and end partly in the retropharyngeal and subparotid,
and partly in the superior deep cervical glands. The vessels of the anterior part
of the floor of the mouth pass either directly to the inferior glands of the superior
deep cervical group, or indirectly through the submental glands; from the rest
of the floor of the mouth the vessels pass to the submaxillary and superior deep
cervical glands.
The lymphatic vessels of the palatine tonsil, usually three to five in number,
pierce the buccopharyngeal fascia and constrictor pharyngis superior and pass
696
ANGIOLOGY
between the Stylohyoideus and internal jugular vein to the uppermost of the
superior deep cervical glands. They end in a gland which lies at the side of the
posterior belly of the Digastricus, on the internal jugular vein; occasionally one
or two additional vessels run to small glands on the lateral side of the vein under
cover of the Sternocleidomastoideus.
Vessels from,
root of tongue
Vessels from
margin of
tongue
Principal
gland of
tongue
"I Vessels from
--' apex
Submental
gland
I Trunks from,
r margin of
tongue
Interrupting nodule
Central trunk
Supra-omohymd
gland
Fig. 605. — Lymphatics ot the tongue. (Poirier and Charpy.)
The lymphatic vessels of the tongue (Fig. 605) are drained chiefly into the deep
cervical glands lying between the posterior belly of the Digastricus and the superior
belly of the Omohyoideus; one gland situated at the bifurcation of the common
carotid artery is so intimately associated with these vessels that it is known as the
principal gland of the tongue. The lymphatic vessels of the tongue may be divided
into four groups: (1) apical, from the tip of the tongue to the suprahyoid glands
and principal gland of the tongue; (2) lateral, from the margin of the tongue —
some of these pierce the Mylohyoideus to end in the submaxillary glands, others
pass down on the Hyoglossus to the superior deep cervical glands; (3) basal, from
the region of the vallate papillae to the superior deep cervical glands; and (4)
median, a few of which perforate the Mylohyoideus to reach the submaxillary
glands, while the majority turn around the posterior border of the muscle to
enter the superior deep cervical glands.
THE LYMPH GLANDS OF THE NECK 697
The Lymph Glands of the Neck.
The lymph glands of the neck include the following groups:
Submaxillary. Superficial Cervical.
Submental. Anterior Cervical.
Deep Cervical.
The submaxillary glands (JympTioglanduhr suhmaxillares) (Fig. 604), three to
six in number, are placed beneath the body of the mandible in the submaxillary
triangle, and rest on the superficial surface of the submaxillary salivary gland.
One gland, the middle gland of Stahr, which lies on the external maxillary artery
as it turns over the mandible, is the most constant of the series; small lymph glands
are sometimes found on the deep surface of the submaxillary salivary glands. The
afferents of the submaxillary glands drain the medial palpebral commissure,
the cheek, the side of the nose, the upper lip, the lateral part of the lower lip,
the gums, and the anterior part of the margin of the tongue; efferent vessels
from the facial and submental glands also enter the submaxillary glands. Their
efferent vessels pass to the superior deep cervical glands.
The submental or suprahyoid glands are situated between the anterior bellies
of the Digastrici. Their afferents drain the central portions of the lower lip and
floor of the mouth and the apex of the tongue; their efferents pass partly to the
submaxillary glands and partly to a gland of the deep cervical group situated on
the internal jugular vein at the level of the cricoid cartilage.
The superficial cervical glands {lymphoglandulae cervicales superficial es) lie in
close relationship with the external jugular vein as it emerges from the parotid
gland, and, therefore, superficial to the Sternocleidomastoideus. Their afferents
drain the lower parts of the auricula and parotid region, while their efferents pass
around the anterior margin of the Sternocleidomastoideus to join the superior deep
cervical glands.
The anterior cervical glands form an irregular and inconstant group on the front
of the larynx and trachea. They may be divided into {a) a superficial set, placed
on the anterior jugular vein; (6) a deeper set, which is further subdivided into
prelaryngeal, on the middle cricothyroid ligament, and pretracheal, on the front
of the trachea. This deeper set drains the lower part of the larynx, the thyroid
gland,* and the upper part of the trachea; its efferents pass to the lowest of the
superior deep cervical glands.
The deep cervical glands Qymphoglandulw cervicales profundcp) (Figs. 602,
605) are numerous and of large size: they form a chain along the carotid sheath,
lying by the side of the pharynx, esophagus, and trachea, and extending from the
base of the skull to the root of the neck. They are usually described in two groups :
(1) the superior deep cervical glands lying under the Sternocleidomastoideus in
close relation with the accessory nerve and the internal jugular vein, some of the
glands lying in front of and others behind the vessel ; (2) the inferior deep cervical
glands extending beyond the posterior margin of the Sternocleidomastoideus
into the supraclavicular triangle, where they are closely related to the brachial
plexus and subclavian vein. A few minute paratracheal glands are situated along-
side the recurrent nerves on the lateral aspects of the trachea and esophagus.
The superior deep cervical glands drain the occipital portion of the scalp, the
auricula, the back of the neck, a considerable part of the tongue, the larynx, thyroid
gland, trachea, nasal part of the pharynx, nasal cavities, palate, and esophagus.
They receive also the efferent vessels from all the other glands of the head and
neck, except those from the inferior deep cervical glands. The inferior deep cervical
glands drain the back of the scalp and neck, the superficial pectoral region, part
of the arm (see page 701), and, occasionally, part of the superior surface of the
k
698
ANGIOLOGY
liver, In addition, they receive vessels from the superior deep cervical glands.
The efferents of the superior deep cervical glands pass partly to the inferior deep
cervical glands and partly to a trunk which unites with the efferent vessel of the
inferior deep cervical glands and forms the jugular trunk. On the right side, this
trunk ends in the junction of the internal jugular and subclavian veins; on the left
side it joins the thoracic duct.
Deltcyideo.
pecioro
glauc
Axillary glands
Fig. 606. — The superficial lymph glanas and lymphatic vessels of the upper extremity.
The lymphatic vessels of the skin and muscles of the neck pass to the deep cervical
glands. From the upper part of the 'pharynx the lymphatic vessels pass to the retro-
pharyngeal, from the lower part to the deep cervical glands. From the larynx
two sets of vessels arise, an upper and a lower. The vessels of the upper set pierce
the hyothyroid membrane and join the superior deep cervical glands. Of the
lower set, some pierce the conus elasticus and join the pretracheal and pre-
laryngeal glands; others run between the cricoid and first tracheal ring and enter
the inferior deep cervical glands. The lymphatic vessels of the thyroid gland con-
sist of two sets, an upper, which accompanies the superior thyroid artery and enters
the superior deep cervical glands, and a lower, which runs partly to the pretracheal
THE LYMPH GLANDS OF THE UPPER EXTREMITY
G99
glands and partly to the small paratracheal glands which accompany the recurrent
nerves. These latter glands receive also the lymphatic vessels from the cervical
portion of the trachea.
THE LYMPHATICS OF THE UPPER EXTREMITY.
The Lymph Glands of the Upper Extremity (Fig. 606).
The lymph glands of the upper extremity are divided into two sets, superficial
and deep.
The superficial lymph glands are few and of small size. One or two supra-
trochlear glands are placed above the medial epicondyle of the humerus, medial
to the basilic vein. Their afferents drain the middle, ring, and little fingers, the
medial portion of the hand, and the superficial area over the ulnar side of the fore-
arm; these vessels are, however, in free communication with the other lymphatic
vessels of the forearm. Their efferents accompany the basilic vein and join the
deeper vessels. One or two deltoideopectoral glands are found beside the cephalic
vein, between the Pectoralis major and Deltoideus, immediately below the clavicle.
They are situated in the course of the external collecting trunks of the arm.
Deltoideopectoral glands
Lateral group
Subclavicular group
I
Central group
Subscapular group
Mammary lymphaiic
ending in
subclavicular glands
—■ Pectoral group
Mammary collecting
trunks
Subareolar plexus
Pectoral group
Cutaneous collecting trunk > V\
from the thoracic uull
Cutaneous collecting \^^ ^ Collecting trunks
trunks passing to internal
mammary glands
Fig. 607. — Lymphatics of the mamma, and the axillary glands (semidiagrammatic) (Poirier and Charpy.)
I
The deep lymph glands are chiefly grouped in the axilla, although a few may
be found in the forearm, in the course of the radial, ulnar, and interosseous vessels,
and in the arm along the medial side of the brachial artery.
The Axillary Glands {lymphoglandulcp axillares) (Fig. 607) are of large size, vary
from twenty to thirty in number, and may be arranged in the following groups:
1. A lateral group of from four to six glands lies in relation to the medial and
posterior aspects of the axillary vein; the afferents of these glands drain the whole
arm with the exception of that portion whose vessels accompany the cephalic
700
ANGIOLOGY
vein. The efferent vessels pass partly to the central and subclavicular groups of
axillary glands and partly to the inferior deep cervical glands.
2. An anterior or pectoral group consists of four or five glands along the lower
border of the Pectoralis minor, in relation with the lateral thoracic artery. Their
afferents drain the skin and muscles of the anterior and lateral thoracic walls,
and the central and lateral parts of the namma; their efferents pass partly to the
central and partly to the subclavicular groups of axillary glands.
3. A posterior or subscapular group of six or seven glands is placed along the lower
margin of the posterior wall of the axilla in the course of the subscapular artery.
The afFerents of this group drain the skin and muscles of the lower part of the back
of the neck and of the posterior thoracic wall; their efTerents pass to the central
group of axillary glands.
4. A central or intermediate group of three or four large glands is imbedded in
the adipose tissue near the base of the axilla. Its afferents are the efferent vessels
of all the preceding groups of axillary glands ; its efferents pass to the subclavicular
group.
5. A medial or subclavicular group of six to twelve glands is situated partly
posterior to the upper portion of the Pectoralis minor and partly above the upper
border of this muscle. Its only direct territorial afferents are those which accompany
the cephalic vein and one which drains the upper peripheral part of the mamma,
but it receives the efferents of all the other axillary glands. The efferent vessels
of the subclavicular group unite to
form the subclavian trunk, which opens
either directly into the junction of
the internal jugular and subclavian
veins or into the jugular lymphatic
trunk; on the left side it may end in
the thoracic duct. A few efferents
from the subclavicular glands usually
pass to the inferior deep cervical
glands.
The Lymphatic Vessels of the
Upper Extremity.
The lymphatic vessels of the upper
extremitv are divided into two sets,
superficial and deep.
The superficial lymphatic vessels
commence (Fig. 608) in the lymphatic
plexus which everywhere pervades
the skin; the meshes of the plexus are
much finer in the palm and on the
flexor aspect of the digits than else-
where. The digital plexuses are drained
by a pair of vessels which run on
the sides of each digit, and incline
backward to reach the dorsum of the
hand. From the dense plexus of the
palm, vessels pass in different direc-
tions, viz., upward toward the wrist,
downward to join the digital vessels,
medialward to join the vessels on the ulnar border of the hand, and lateralward to
those on the thumb. Several vessels from the central part of the plexus unite ta
Fig.
608. — Lymphatic vessels of the dorsal surface of the
hand. (Sappey.)
THE LYMPH GLANDS OF THE LOWER EXTREMITY
701
form a trunk, which passes around the metacarpal bone of the index finger to join
the vessels on the back of that digit and on the back of the thumb. Running
upward in front of and behind the wrist, the lymphatic vessels are collected
into radial, median, and ulnar groups, which accompany respectively the cephalic,
median, and basilic veins in the forearm. A few of the ulnar lymphatics end in
the supratrochlear glands, but the majority pass directly to the lateral group of
axillary glands. Some of the radial vessels are collected into a trunk which
ascends with the cephalic vein to the deltoideopectoral glands; the efferents from
this group pass either to the subclavicular axillary glands or to the inferior cervical
glands.
The deep lymphatic vessels accompany the deep bloodvessels. In the fore-
arm, they consist of four sets, corresponding with the radial, ulnar, volar, and
dorsal interosseous arteries; they communicate at intervals with the superficial
lymphatics, and some of them end in the glands which are occasionally found beside
the arteries. In their course upward, a few end in the glands which lie upon the
brachial artery; but most of them pass to the lateral group of axillary glands.
Tibial nerve
Popliteal vein
Popliteal artery
Common peronceal nerve
Gland at side of popliteaJ^
vesseln
Gland on back of knee
joint
Gland at termination of
small saph. vein
Fig. 600. — Lymph glands of popliteal fossa. (Poirier and Charpy.)
THE LYMPHATICS OF THE LOWER EXTREMITY.
The Lymph Glands of the Lower Extremity.
The lymph glands of the lower extremity consist of the anterior tibial gland
and the popliteal and inguinal glands.
V The anterior tibial gland (lymphoglandula tibialis anterior) is small and incon-
stant. It lies on the interosseous membrane in relation to the upper part of the
anterior tibial vessels, and constitutes a substation in the course of the anterior
tibial lymphatic trunks.
The popliteal glands {lymphogla^idula poplitea-) (Fig. 609), small in size and
some six or seven in number, are imbedded in the fat contained in the popliteal
702
AXGIOLOGY
"Sc
Superficial
inguinal ■
glands
Superficial
subiiiguinal-
glu lids
ir%~.
f\j
'■W
Fig. 610. — The superficial lymph glands and lymphatic
vessela of the lower extremity.
fossa. One lies immediately beneath
the popliteal fascia, near the terminal
part of the small saphenous vein, and
drains the region from which this vein
derives its tributaries. Another is placed
between the popliteal artery and the
posterior surface of the knee-joint; it
receives the lymphatic vessels from the
knee-joint together with those which
accompany the genicular arteries. The
others lie at the sides of the popliteal
vessels, and receive as efl'erents the
trunks which accompany the anterior
and posterior tibial vessels. The effer-
ents of the popliteal glands pass almost
entirely alongside the femoral vessels to
the deep inguinal glands, but a few may
accompany the great saphenous vein,
and end in the glands of the superficial
subinguinal group.
I The inguinal glands [lymyhoglandidcr
\inginnales) (Fig. 610), from twelve to
twentv in number, are situated at the
upper part of the femoral triangle. They
may be divided into two groups by a
horizontal line at the level of the termi-
nation of the great saphenous vein;
those lying above -this line are termed
/ the superficial inguinal glands, and those
below it the subinguinal glands, the latter
group consisting of a superficial and a
deep set.
The Superficial Inguinal Glands form
a chain immediately below the inguinal
ligament. Thev receive as afferents Ivm-
phatic vessels from the integument of
the penis, scrotum, perineum, buttock,
and abdominal wall below the level of
the umbilicus.
The Superficial Subinguinal Glands
{lymphoglandidcc suhinguincdes super-
ficiales) are placed on either side of the
upper part of the great saphenous vein;
their efferents consist chiefly of the
superficial lymphatic vessels of the
lower extremitv; but thev also receive
some of the vessels which drain the in-
tegument of the penis, scrotum, peri-
neum, and buttock.
The Deep Subinguinal Glands {lympho-
glandulcF siihingninales profundce) vary
from one to three in number, and are
placed under the fascia lata, on the
medial side of the femoral vein. \Yhen
THE LYMPH GLANDS OF THE ABDOMEN AND PELVIS 703
three are present, the lowest is situated just below the junction of the great saphe-
nous and femoral veins, the middle in the femoral canal, and the highest in the
lateral part of the femoral ring. The middle one is the most inconstant of the
three, but the highest, the gland of Cloquet or RosenmuUer, is also frequently absent.
They receive as afferents the deep lymphatic trunks which accompany the femoral
vessels, the lymphatics from the glans penis vel clitoridis, and also some of the
eflferents from the superficial subinguinal glands.
The Lymphatic Vessels of the Lower Extremity.
The lymphatic vessels of the lower extremity consist of two sets, superficial
and deep, and in their distribution correspond closely with the veins.
The superficial lymphatic vessels lie in the superficial fascia, and are divisible
into two groups: a medial, which follows the course of the great saphenous vein,
and a lateral, which accompanies the small saphenous vein. The vessels of the
medial group (Fig. 610) are larger and more numerous than those of the lateral
group, and commence on the tibial side and dorsum of the foot; they ascend both
in front of and behind the medial malleolus, run up the leg with the great saphe-
nous vein, pass with it behind the medial condyle of the femur, and accompany
it to the groin, where they end in the subinguinal group of superficial glands.
The vessels of the lateral group arise from the fibular side of the foot; some ascend
in front of the leg, and, just below the knee, cross the tibia to join the lymphatics
on the medial side of the thigh; others pass behind the lateral malleolus, and,
accompanying the small saphenous vein, enter the popliteal glands.
The deep lymphatic vessels are few in number, and accompany the deep blood-
vessels. In the leg, they consist of three sets, the anterior tibial, posterior tibial,
and peroneal, which accompany the corresponding bloodvessels, two or three with
each artery; they enter the popliteal lymph glands.
The deep lymphatic vessels of the gluteal and ischial regions follow the course
of the corresponding bloodvessels. Those accompanying the superior gluteal
vessels end in a gland which lies on the intrapelvic portion of the superior gluteal
artery near the upper border of the greater sciatic foramen. Those following
the inferior gluteal vessels traverse one or two small glands which lie below the
Piriformis muscle, and end in the hypogastric glands.
THE LYMPHATICS OF THE ABDOMEN AND PELVIS.
The Lymph Glands of the Abdomen and Pelvis.
The lymph glands of the abdomen and pelvis may be divided, from their situa-
tions, into (a) parietal, lying behind the peritoneum and in close association with
the larger bloodvessels; and (6) visceral, which are found in relation to the visceral
arteries.
The parietal glands (Figs. 611, 612) include the following groups:
External Iliac. Iliac Circumflex. ^Lateral Aortic.
Common Iliac. Hypogastric. Lumbar j Preaortic.
Epigastric. Sacral. [Retroaortic.
The External Iliac Glands, from eight to ten in number, lie along the external
iliac vessels. They are arranged in three groups, one on the lateral, another
on the medial, and a third on the anterior aspect of the vessels; the third group is,
however, sometimes absent. Their principal afferents are derived from the inguinal
and subinguinal glands, the deep lymphatics of the abdominal wall below the umbili-
cus and of the adductor region of the thigh, and the lymphatics from the glans
704
ANGIOLOGY
penis vel clltoridis, the membranous urethra, the prostate, the fundus of the bladder,
the cervix uteri, and upper part of the vagina.
The Common Iliac Glands, four to six in number, are grouped behind and on the
sides of the common ihac artery, one or two being placed below the bifurcation
of the aorta, in front of the fifth lumbar vertebra. They drain chiefly the hi^'po-
gastric and external iliac glands, and their eflferents pass to the lateral aortic glands.
The Epigastric Glands (lymphoglcmdulcp eingasiricoe) , three or four in number,
are placed alongside the lower portion of the inferior epigastric vessels.
Left lateral aortic
Common
Gland in
front of sacral
'promontory
Ccnnmon iliac —
ExterTud iliac
Obturator
1 > Common
) iliac
External iliac
_ Obturator
/// nerve
V/L Obturator
artery
External iliac
Obturator gland
:5
^'
FiQ. 611. — The parietal lymph glands of the pelvis. (Cun6o and Marcille.)
The Iliac Circumflex Glands, two to four in number, are situated along the course
of the deep iliac circumflex vessels; they are sometimes absent.
The Hypogastric Glands {lymphoglmidulw hypogastricoe; mternal iliac gland)
(Fig. 612) surround the hypogastric vessels, and receive the lymphatics corre-
sponding to the distribution of the branches of the hypogastric artery, i. e., they
receive lymphatics from all the pelvic viscera, from the deeper parts of the perineum,
including the membranous and cavernous portions of the urethra, and from the
buttock and back of the thigh. An obturator gland is sometimes seen in the upper
part of the obturator foramen.
The Sacral Glands are placed in the concavity of the sacrum, in relation to the
THE LYMPH GLANDS OF THE ABDOMEN AND PELVIS
705
middle and lateral sacral arteries; they receive lymphatics from the rectum and
posterior wall of the pelvis.
The efferents of the hypogastric group end in the common iliac glands.
The Lumbar Glands {lymphoglandulop lumbales) are very numerous, and consist
of right and left lateral aortic, preaortic, and retroaortic groups.
The right lateral aortic glands are situated partly in front of the inferior vena
cava, near the termination of the renal vein, and partly behind it on the origin of the
Psoas major, and on the right crus of the diaphragm. The left lateral aortic
glands form a chain on the left side of the abdominal aorta in front of the origin
of the Psoas major and left crus of the diaphragm. The glands on either side
receive (a) the efferents of the common iliac glands, (b) the lymphatics from the
testis in the male and from the ovary, uterine tube, and body of the uterus in the
Gtarid in front of
Sdcral promontory
External iliac
glands
Internal lymphatics of
bladder
Lympha i ic from glans
penis
Lymphatic!! of bladder
Lateral sacral
' ~'"4\\F'V \ Hypogastric:
'^ \l i \ Satellite trunk of
- — •" M'7 - /j- internal puden-
^-- i/'/ 7 dal vessels.
Trunk of middle
hfi'morrhoidal
vessels.
Prostatic collecting trunk
ethial collettinj tiunks
Glandular nodule in front of symphysis Prostatic collecting trunk
FiQ. 612. — Iliopelvic glands (lateral view). (Cun6o and Marcille.)
female; (c) the lymphatics from the kidney and suprarenal gland; and (d) the
lymphatics draining the lateral abdominal muscles and accompanying the lumbar
veins. Most of the efferent vessels of the lateral aortic glands converge to form
the right and left lumbar trunks which join the cisterna chyli, but some enter the
pre- and retroaortic glands, and others pierce the crura of the diaphragm to join
the lower end of the thoracic duct. The preaortic glands lie in front of the aorta,
and may be divided into celiac, superior mesenteric, and inferior mesenteric groups,
arranged around the origins of the corresponding arteries. They receive a few
vessels from the lateral aortic glands, but their principal afferents are derived from
the viscera supplied by the three arteries with which they are associated. Some
of their efferents pass to the retroaortic glands, but the majority unite to form
the intestinal trunk, which enters the cisterna chyli. The retroaortic glands are placed
45
706 ANGIOLOGY
below the cisterna chyli, on the hodies of the third and fourth lumbar vertebrae.
They receive lymphatic trunks from the lateral and preaortic glands, while their
efferents end in the cisterna chyli.
The Lymphatic Vessels of the Abdomen and Pelvis.
The lymphatic vessels of the walls of the abdomen and pelvis may be divided
into two sets, superficial and deep.
The superficial vessels follow the course of the superficial bloodvessels and
converge to the superficial inguinal glands; those derived from the integument
of the front of the abdomen below the umbilicus follow the course of the superficial
epigastric vessels, and those from the sides of the lumbar part of the abdominal
wall pass along the crest of the ilium, with the superficial iliac circumflex vessels.
The superficial lymphatic vessels of the gluteal region turn horizontally around the
buttock, and join the superficial inguinal and subinguinal glands.
The deep vessels run alongside the principal bloodvessels. Those of the parietes
of the pelvis, which accompany the superior and inferior gluteal, and obturator
vessels, follow the course of the hypogastric artery, and ultimately join the lateral
aortic glands.
Lymphatic Vessels of the Perineum and External Genitals. — The lymphatic vessels
of the perineum, of the integument of the penis, and of the scrotum (or vulva),
follow the course of the external pudendal vessels, and end in the superficial ingui-
nal and subinguinal glands. Those of the glans penis vel clitoridis terminate
partly in the deep subinguinal glands and partly in the external iliac glands.
The visceral glands are associated with the branches of the celiac, superior
and inferior mesenteric arteries. Those related to the branches of the celiac
artery form three sets, gastric, hepatic, and pancreaticolienal.
The Gastric Glands (Figs. 613, 614) consist of two sets, superior and inferior.
The Superior Gastric Glands {lymphoglandula: gastricoe superiores) accompany
the left gastric artery and are divisible into three groups, viz.: {a) upper, on the
stem of the artery; (6) lower, accompanying the descending branches of the artery
along the cardiac half of the lesser curvature of the stomach, between the two layers
of the lesser omentum; and (c) paracardial outlying members of the gastric glands,
disposed in a manner comparable to a chain of beads around the neck of the stomach
(Jamieson and Dobson'). They receive their afferents from the stomach; their
efferents pass to the celiac group of preaortic glands.
The Inferior Gastric Glands {lymphoglandulce gastricce inferiores; right gastro-
epiploic gland), four to seven in number, lie between the two layers of the greater
omentum along the pyloric half of the greater curvature of the stomach.
The Hepatic Glands [lymphoglandulce hepaticcp) (Fig. 613), consist of the follow-
ing groups: (fl) hepatic, on the stem of the hepatic artery, and extending upward
along the common bile duct, between the two layers of the lesser omentum, as
far as the porta hepatis; the cystic gland, a member of this group, is placed near
the neck of the gall-bladder; (6) subpyloric, four or five in number, in close relation
to the bifurcation of the gastroduodenal artery, in the angle between the superior
and descending parts of the duodenum; an outlying member.of this group is some-
times found above the duodenum on the right gastric (pyloric) artery. The glands
of the hepatic chain receive afferents from the stomach, duodenum, liver, gall-
bladder, and pancreas; their efferents join the celiac group of preaortic glands.
The Pancreaticolienal Glands {lymphoglandidoe pancreaticolienales; splenic
glands) (Fig. 614) accompany the lienal (splenic) artery, and are situated in rela-
tion to the posterior surface and upper border of the pancreas ; one or two members
1 Lancet, April 20 and 27, 1907.
THE LYMPHATIC VESSELS OF THE ABDOMEX AXD PELVIS 707
Paracardial glands
Superior gastric glands
Hepatic glands \ I .^^f'*"^
S lib pyloric
glands
/sto)'-r'
'll I '
"S^-^c^.
Pancreaticolienal glands
Inferior gastric glands
Fig. 613. — Lymphatics of stomach, etc. (Jamieson and Dobson.)
Suhpylorw
glands
FlQ. 614. — Lymphatics of stomach, etc. The stomach has been turned upward. (Jamieson and Dobson.)
708
ANGIOLOGY
of this group are found in the gastrolienal ligament (Jamieson and Dobson, op. cit.).
Their aflferents are derived from the stomach, spleen, and pancreas, their efferents
join the celiac group of preaortic glands.
Duodenum
Upper group of
ileocolic glands
Lower group of
ileocolic glands
Cecum Vermiform process
Fia. 615. — ^The lymphatics of cecum and vermiform process from the front. (Jamieson and Dobson.)
9
I
Upper group of
ileocolic glatuls
Lower group of
ileocolic glands
Vermiform process Cecum
Fig. 616. — The lymphatics of cecum and vermiform process from behind. (Jamieson and Dobson.;
THE LYMPHATIC VESSELS OF ABDOMEN AND PELVIS
709
The superior mesenteric glands may be divided into three principal groups:
mesenteric, ileocolic, and mesocolic.
The Mesenteric Glands {lymi)hoglandid(r vies enter iccp) lie between the layers of
the mesentery. They vary from one hundred to one hundred and fifty in number,
and may be grouped into three sets, viz. : one lying close to the wall of the small
intestine, among the terminal twigs of the superior mesenteric artery; a second,
in relation to the loops and primary branches of the vessels; and a third along
the trunk of the artery.
The Ileocolic glands (Figs. 615, GIG), from ten to twenty in number, form a chain
around the ileocolic artery, but show a tendency to subdivision into two groups,
one near the duodenum and another on the lower part of the trunk of the artery.
Inferior mesenteric glands
Fig. 617. — Lymphatics of colon. (Jamieson and DobaoiL^
Where the vessel divides into its terminal branches the chain is broken up into sev-
eral groups, viz.: (a) ileal, in relation to the ileal branch of the artery; {h) anterior
ileocolic, usually of three glands, in the ileocolic fold, near the wall of the cecum;
(c) posterior ileocolic, mostly placed in the angle between the ileum and the colon,
but partly lying behind the cecum at its junction with the ascending colon; {d)
a single gland, between the layers of the mesenteriole of the vermiform process;
{e) right colic, along the medial side of the ascending colon.
The Mesocolic Glands (lymphoglandulopmesocoUcGp) are numerous, and lie between
the layers of the transverse mesocolon, in close relation to the transverse colon; they
are best developed in the neighborhood of the right and left colic flexures. One or
two small glands are occasionally seen along the trunk of the right colic artery and
others are found in relation to the trunk and branches of the middle colic artery.
710 ANGIOLOGY
The superior mesenteric glands receive afferents from the jejunum, ileum, cecum,
vermiform process, and the ascending and transverse parts of the colon; their
efferents pass to the preaortic glands.
The inferior mesenteric glands (Fig. 617) consist of: (a) small glands on the
branches of the left colic and sigmoid arteries; (6) a group in the sigmoid mesocolon,
around the superior hemorrhoidal artery; and (c) a pararectal group in contact with
the muscular coat of the rectum. They drain the descending iliac and sigmoid
parts of the colon and the upper part of the rectum; their efferents pass to the
preaortic glands.
The Lymphatic Vessels of the Abdominal and Pelvic Viscera.
The lymphatic vessels of the abdominal and pelvic viscera consist of (1) those
of the subdiaphragmatic portion of the digestive tube and its associated glands,
the liver and pancreas ; (2) those of the spleen and suprarenal glands ; (3) those of
the urinary organs; (4) those of the reproductive organs.
1. The lymphatic vessels of the subdiaphragmatic portion of the digestive tube
are situated partly in the mucous membrane and partly in the seromuscular coats,
but as the former system drains into the latter, the two may be considered as one.
The Lymphatic Vessels of the Stomach (Figs. 613, 614) are continuous at the
cardiac orifice with those of the esophagus, and at the pylorus with those of the
duodenum. They mainly follow the bloodvessels, and may be arranged in four
sets. Those of the first set accompany the branches of the left gastric artery,
receiving tributaries from a large area on either surface of the stomach, and ter-
minate in the superior gastric glands. Those of the second set drain the fundus
and body of the stomach on the left of a line drawn vertically from the esophagus;
they accompany, more or less closely, the short gastric and left gastroepiploic
arteries, and end in the pancreaticolienal glands. The vessels of the third set drain
the right portion of the greater curvature as far as the pyloric portion, and end in
the inferior gastric glands, the efferents of which pass to the subpyloric group.
Those of the fourth set drain the pyloric portion and pass to the hepatic and
subpyloric glands, and to the superior gastric glands.
The Ljonphatic Vessels of the Duodenum consist of an anterior and a posterior
set, which open into a series of small pancreaticoduodenal glands on the anterior
and posterior aspects of the groove between the head of the pancreas and the duo-
denum. The efferents of these glands run in two directions, upward to the hepatic
glands and downward to the preaortic glands around the origin of the superior
mesenteric artery.
The Lymphatic Vessels of the Jejunum and Ileum are termed lacteals, from the
milk-white fluid they contain during intestinal digestion. They run between the
layers of the mesentery and enter the mesenteric glands, the efferents of which
end in the preaortic glands.
The Lymphatic Vessels of the Vermiform Process and Cecum (Figs. 615, 616) are
numerous, since in the wall of this process there is a large amount of adenoid tissue.
From the body and tail of the vermiform process eight to fifteen vessels ascend
between the layers of the mesenteriole, one or two being interrupted in the gland
which lies between the layers of this peritoneal fold. They unite to form three
or four vessels, which end partly in the lower and partly in the upper glands of the
ileocolic chain. The vessels from the root of the vermiform process and from the
cecum consist of an anterior and a posterior group. The anterior vessels pass in
front of the cecum, and end in the anterior ileocolic glands and in the upper and
lower glands of the ileocolic chain; the posterior vessels ascend over the back of the
cecum and terminate in the posterior ileocolic glands and in the lower glands of the
ileocolic chain.
THE LYMPHATIC VESSELS OF ABDOMINAL AND PELVIC VISCERA 711
Lymphatic Vessels of the Colon (Fig. G17).^The lymphatic vessels of the ascend-
ing and transverse parts of the colon finally end in the mesenteric glands, after
traversing the right colic and mesocolic glands. Those of the descending and iliac
sigmoid parts of the colon are interrupted by the small glands on the branches
of the left colic and sigmoid arteries, and ultimately end in the preaortic glands
around the origin of the inferior mesenteric artery.
Lymphatic Vessels of the Anus, Anal Canal, and Rectum. — The lymphatics from
the anus pass forward and end with those of the integument of the perineum and
scrotum in the superficial inguinal glands; those from the anal canal accompany
the middle and inferior hemorrhoidal arteries, and end in the hypogastric glands;
while the vessels from the rectum traverse the pararectal glands and pass to those
in the sigmoid mesocolon; the efferents of the latter terminate in the preaortic
glands around the origin of the inferior mesenteric artery.
The Lymphatic Vessels of the Liver are divisible into two sets, superficial and deep.
The former arise in the subperitoneal areolar tissue over the entire surface of the
organ, and mscy be grouped into (a) those on the convex surface, (6) those on the
inferior surface.
(a) On the convex surface: The vessels from the back part of this surface reach
their terminal glands by three different routes; the vessels of the middle set, five
or six in number, pass through the vena-caval foramen in the diaphragm and end
in one or two glands which are situated around the terminal part of the inferior
vena cava; a few vessels from the left side pass backward toward the esophageal
hiatus, and terminate in the paracardial group of superior gastric glands; the vessels
from the right side, one or two in number, run on the abdominal surface of the
diaphragm, and, after crossing its right crus, end in the preaortic glands which
surround the origin of the celiac artery. From the portions of the right and left
lobes adjacent to the falciform ligament, the lymphatic vessels converge to form
two trunks, one of which accompanies the inferior vena cava through the dia-
phragm, and ends in the glands around the terminal part of this vessel; the other
runs downward and forward, and, turning around the anterior sharp margin of the
liver, accompanies the upper part of the ligamentum teres, and ends in the upper
hepatic glands. From the anterior surface a few additional vessels turn around the
anterior sharp margin to reach the upper hepatic glands.
(b) On the inferior surface: The vessels from this surface mostly converge
to the porta hepatis, and accompany the deep lymphatics, emerging from the
porta to the hepatic glands; one or two from the posterior parts of the right and
caudate lobes accompany the inferior vena cava through the diaphragm, and
end in the glands around the terminal part of this vein.
The deep lymphatics converge to ascending and descending trunks. The ascend-
ing trunks accompany the hepatic veins and pass through the diaphragm to end
in the glands around the terminal part of the inferior vena cava. The descending
trunks emerge from the porta hepatis, and end in the hepatic glands.
The Lymphatic Vessels of the Gall-bladder pass to the hepatic glands in the porta
hepatis; those of the common bile duct to the hepatic glands alongside the duct
and to the upper pancreaticoduodenal glands.
The Lymphatic Vessels of the Pancreas follow the course of its bloodvessels.
Most of them enter the pancreaticolienal glands, but some end in the pancreatico-
duodenal glands, and others in the preaortic glands near the origin of the superior
mesenteric artery.
2. The lymphatic vessels of the spleen and suprarenal glands.
The Lymphatic Vessels of the Spleen, both superficial and deep, pass to the pan-
creaticolienal glands.
The Lymphatic Vessels of the Suprarenal Glands usually accompany the supra-
renal veins, and end in the lateral aortic glands; occasionally some of them
k
712
ANGIOLOGY
pierce the crura of the diaphragm and end in the glands of the posterior medias-
tinum.
3. The lymphatic vessels of the urinary organs.
The Lymphatic Vessels of the Kidney form three plexuses: one in the substance
of the kidney, a second beneath its fibrous capsule, and a third in the perinephric
fat; the second and third communicate freely with each other. The Aessels from
the plexus in the kidney substance converge to form four or five trunks which
issue at the hilum. Here they are joined by vessels from the plexus under the
capsule, and, following the course of the renal vein, end in the lateral aortic glands.
The perinephric plexus is drained directly into the upper lateral aortic glands.
The Lymphatic Vessels of the Ureter run in different directions. Those from
its upper portion end partly in the efferent vessels of the kidney and partly in the
lateral aortic glands; those from the portion immediately above the brim of the
lesser pelvis are drained into the common iliac glands; while the vessels from the
intrapelvic portion of the tube either join the efiereuts from the bladder, or end
in the hypogastric glands.
Common iliac
artery
External iliac
glands
Lymphatics (
from bladder {
Gland in front of
sacral promontory
Hypogastric
glands
Ureter
Lymphatics frcmi
bladder
Fig. 618. — Lymphatics of the bladder. (Cun6o and MarciUe.)
The Lymphatic Vessels of the Bladder (Fig. 618) originate in two plexuses, an
intra- and an extramuscular, it being generally admitted that the mucous mem-
brane is devoid of lymphatics. ^ The efferent vessels are arranged in two groups,
one from the anterior and another from the posterior surface of the bladder. The
vessels from the anterior surface pass to the external iliac glands, but in their course
minute glands are situated. These minute glands are arranged in two groups,
an anterior vesical, in front of the bladder, and a lateral vesical, in relation to the
lateral umbilical ligament. The vessels from the posterior surface pass to the hypo-
gastric, external, and common ihac glands; those draining the upper part of this
surface traverse the lateral vesical glands.
' Some authorities maintain that a plexus of lymphatic vessels docs exist in the mucous membrane of the bladder
(consult M6decine op6ratoire des Voies urinaires, par J. Albarran. Paris. 1909).
THE LYMPHATIC VESSELS OF ABDOMINAL AXD PELVIC VISCERA 713
The Lymphatic Vessels of the Prostate (Fig. 619) terminate chiefly in the hypo-
gastric and sacral glands, but one trunk from the posterior surface ends in the exter-
nal iliac glands, and another from the anterior surface joins the vessels which drain
the membranous part of the urethra.
Lymphatic Vessels of the Urethra. — The lymphatics of the cavernous portion of
the urethra.accompany those of the glans penis, and terminate with them in the deep
subinguinal and external iliac glands. Those of the memhranous and prostatic
portions, and those of the whole urethra in the female, pass to the hypogastric glands.
iliac glands {
Ext. iliac
Vessels draining
into ext. iliac
glands
Retroprostatic
lymph-nodes
Vessels draining
into gla7id on
sacral prom-
ontory
• Gland in front
of sacral
promontory
^yA.-—- Lateral sacral
glands
..Ext. iliac
glands
.Vessel.'^ drain-
ing into
gland on
sacral prom-
ontory
■Middle hem-
orrhoidal
gland
•Middle hem-
orrhoidal
lymphatic
vessels
Fig. 619. — Lymphatics of the prostate. (Cun^o and Marcillel
(4) The lymphatic vessels of the reproductive organs.
The Ljmiphatic Vessels of the Testes consist of two sets, superficial and deep,
the former commencing on the surface of the tunica vaginalis, the latter in the
epididymis and body of the testis. They form from four to eight collecting trunks
which ascend with the spermatic veins in the spermatic cord and along the front
of the Psoas major to the level where the spermatic vessels cross the ureter and end
in the lateral and preaortic groups of lumbar glands.^
The L3miphatic Vessels of the Ductus Deferens pass to the external ihac glands;
those of the vesiculae seminales partly to the hypogastric and partly to the external
glands.
' "The Lymphatics of the Testicle," by Jamieson and Dobson, Lancet, February 19, 1900.
714
ANGIOWGY
The Lymphatic Vessels of the Ovary are similar to those of the testis, and ascend
with the ovarian artery to the lateral and preaortic glands.
The Lymphatic Vessels of the Uterine Tube pass partly with those of the ovary
and partly with those of the uterus.
The Lymphatic Vessels of the Uterus (Fig. G20) consist of two sets, superficial
and deep, the former being placed beneath the peritoneum, the latter in the sub-
stance of the organ. The lymphatics of the cervix uteri run in three directions:
transversely to the external iliac glands, postero-laterally to the hypogastric glands,
and posteriorly to the common iliac glands. The majority of the vessels of the body
Efferents to lat.
aortic glands
Efferents to ext.
iliac glands
Network in lateral
aspect of cervix
uteri
_ Glands in front
of sacral prom-
ontory
Efferents to glands
"■"" in front of sa-
cral promontory
A Hypogastric
glands
Lat. sacral
glands
Vessels draining
into hypogastric
glands
Vessels passitig
to lat. sacral
glands
Fig. G20. — Lymphatics of the uterua. (Cun6o and Maroille.)
and fundus of the uterus pass lateralward in the broad ligaments, and are continued
up with the ovarian vessels to the lateral and preaortic glands; a few, however,
run to the external iliac glands, and one or two to the superficial inguinal glands.
In the unimpregnated uterus the lymphatic vessels are very small, but during
gestation they are. greatly enlarged.
The Lymphatic Vessels of the Vagina are carried in three directions: those of
the upper part of the vagina to the external iliac glands, those of the middle part
to the hypogastric glands, and those of the lower part to the common iliac glands.
On the course of the vessels from the middle and lower parts small glands are
situated. Some lymphatic vessels from the lower part of the vagina join those
of the vulva and pass to the superficial inguinal glands. The lymphatics of the
vagina anastomose with those of the cervix uteri, vulva, and rectum, but not with
those of the bladder.
THE LYMPHATICS OF THE THORAX 715
THE LYMPHATICS OF THE THORAX.
The lymph glands of the thorax may he divided into parietal and visceral — the
former being situated in the thoracic wall, the latter in relation to the viscera.
The parietal lymph glands include the sternal, intercostal, and diaphragmatic
glands.
1. The Sternal Glands {lymphoglaruhdce sternales; internal mammary glands) are
placed at the anterior ends of the intercostal spaces, by the side of the internal
mammary artery. They derive afferents from the mamma, from the deeper struc-
tures of the anterior abdominal wall above the level of the umbilicus, from the
upper surface of the liver through a small group of glands which lie behind the
xiphoid process, and from the deeper parts of the anterior portion of the thoracic
wall. Their efi'erents usually unite to form a single trunk on either side; this may
open directly into the junction of the internal jugular and subclavian veins, or
that of the right side may join the right subclavian trunk, and that of the left
the thoracic duct.
2. The Intercostal Glands {lyviplioglandulw iniercosiahs) occupy the posterior -
parts of the intercostal spaces, in relaticm to the intercostal vessels. They receive
the deep lymphatics from the postero- lateral aspect of the chest; some of these
vessels are interrupted by small lateral intercostal glands. The efferents of the
glands in the lower four or five spaces unite to form a trunk, which descends and
opens either into the cisterna chyli or into the commencement of the thoracic duct.
The efferents of the glands in the upper spaces of the left side end in the thoracic
duct; those of the corresponding right spaces, in the right lymphatic duct.
3. The Diaphragmatic Glands lie on the thoracic aspect of the diaphragm,
and consist of three sets, anterior, middle, and posterior.
The anterior set comprises (a) two or three small glands behind the base of the
xiphoid process, which receive afferents from the convex surface of the liver, and
(b) one or two glands on either side near the junction of the seventh rib with its
cartilage, which re(?eive lymphatic vessels from the front part of the diaphragm.
The efferent vessels of the anterior set pass to the sternal glands.
The middle set consists of two or three glands on either side close to where the
phrenic nerves enter the diaphragm. On the right side some of the glands of this
group lie within the fibrous sac of the pericardium, on the front of the termination
of the inferior vena cava. The afferents of this set are derived from the middle
part of the diaphragm, those on the right side also receiving afferents from the
convex surface of the liver. Their efferents pass to the posterior mediastinal glands
The posterior set consists of a few glands situated on the back of the crura of
the diaphragm, and connected on the one hand with the lumbar glands and on
the other with the posterior mediastinal glands.
The superficial lymphatic vessels of the thoracic wall ramify beneath the skin
and converge to the axillary glands. Those over the Trapezius and Latissimus
dorsi run forward and unite to form about ten or twelve trunks which end in the
subscapular group. Those over the pectoral region, including the vessels from the
skin covering the peripheral part of the mamma, run backAvard, and those over
the Serratus anterior upward, to the pectoral group. Others near the lateral margin
of the sternum pass inward between the rib cartilages and end in the sternal glands,
while the vessels of opposite sides anastomose across the front of the sternum. A
few vessels from the upper part of the pectoral region ascend over the clavicle to
the supraclavicular group of cervical glands.
The Lymphatic Vessels of the Mamma originate in a plexus in the interlobular
spaces and on the walls of the galactophorous ducts. Those from the central part
of the gland pass to an intricate plexus situated beneath the areola, a plexus which
receives also the lymphatics from the skin over the central part of the gland and
716
ANGIOLOGY
those from the areola and nipple. Its efferents are collected into two trunks which
pas? to the pectoral group of axillary glands. The vessels which drain the medial
part of the mamma pierce the thoracic wall and end in the sternal glands, while
a vessel has occasionally been seen to emerge from the upper part of the mamma
and, piercing the Pectoralis major, terminate in the subclavicular glands (Fig. 607).
MEDIASTINAL
NODES AND
VESSELS
INTERCOSTAL
NODES AND
VESSELS
MMON INTES-
TINAL TRUNK
COMMON INTES-
TINAL TRUNK
INTERNAL ILIAC
EXTERNAL ILIAC
Fia. 621. — Deep lymph nodes and vessels of the thorax and abdomen (diagrammatic). Afferent vessels are
represented by continuous lines, and efferent and internodular vessels by dotted lines. (Cunningham.)
The deep lymphatic vessels of the thoracic wall (Fig. 621) consist of:
1. The lymphatics of the muscles which lie on the ribs: most of these end in
the axillary glands, but some from the Pectoralis major pass to the sternal glands.
2. The intercostal vessels which drain the Intercostales and parietal pleura. Those
draining the Intercostales externi run backward and, after receiving the vessels
1
THE LYMPHATICS OF THE THORAX 111
which accompany the posterior branches of the intercostal arteries, end in the
intercostal glands. Those of the Intercostales interni and parietal pleura consist
of a single trunk in each space. These trunks run forward in the subpleural tissue
and the upper six open separately into the sternal glands or into the vessels which
unite them; those of the lower spaces unite to form a single trunk which terminates
in the lowest of the sternal glands. 3. The lymphatic vessels of the diaphragm,
which form two plexuses, one on its thoracic and another on its abdominal surface.
These plexuses anastomose freely with each other, and are best marked on the
parts covered respectively by the pleurae and peritoneum. That on the thoracic
surface communicates with the lymphatics of the costal and mediastinal parts of
the pleura, and its efferents consist of three groups: (a) anterior, passing to the gland
which lie near the junction of the seventh rib with its cartilage; (h) middle, to the
glands on the esophagus and to those around the termination of the inferior vena
cava; and (o) posterior, to the glands which surround the aorta at the point where
this vessel leaves the thoracic cavity.
The plexus on the abdominal surface is composed of fine vessels, and anasto-
moses with the lymphatics of the liver and, at the periphery of the diaphragm,
with those of the subperitoneal tissue. The efferents from the right half of this
plexus terminate partly in a group of glands on the trunk of the corresponding
inferior phrenic artery, while others end in the right lateral aortic glands. Those
from the left half of the plexus pass to the pre- and lateral aortic glands and to the
glands on the terminal portion of the esophagus.
The visceral lymph glands consist of three groups, viz.: anterior mediastinal,
posterior mediastinal, and tracheobronchial.
The Anterior Mediastinal Glands {lympJioglandulw mediastinales anteriores) are
placed in the anterior part of the superior mediastinal cavity, in front of the aortic
arch and in relation to the innominate veins and the large arterial trunks which
arise from the aortic arch. They receive afferents from the thymus and pericar-
dium, and from the sternal glands; their efferents unite with those of the tracheo-
bronchial glands, to form the right and left bronchomediastinal trunks.
The Posterior Mediastinal Glands {lymphoglanduloe mediastinales posteriores)
lie behnid the pericardium in relation to the esophagus and descending thoracic
aorta. Their aft'erents are derived from the esophagus, the posterior part of the
pericardium, the diaphragm, and the convex surface of the liver. Their efferents
mostly end in the thoracic duct, but some join the tracheobronchial glands.
The Tracheobronchial Glands (Fig. 622) form four main groups: (a) tracheal,
on either side of the trachea; (b) bronchial, in the angles between the lower part
of the trachea and bronchi and in the angle between the two bronchi; (c) broncho-
pulmonary, in the hilus of each lung; and (d) pulmonary, in the lung substance, on
the larger branches of the bronchi. The afferents of the tracheobronchial glands
drain the lungs and bronchi, the thoracic part of the trachea and the heart; some
of the efferents of the posterior mediastinal glands also end in this group. Their
efferent vessels ascend upon the trachea and unite with efferents of the internal
mammary and anterior mediastinal glands to form the right and left broncho-
mediastinal trunks. The right bronchomediastinal trunk may join the right
lymphatic duct, and the left the thoracic duct, but more frequently they open
independently of these ducts into the junction of the internal jugular and
subclavian veins of their own side.
In all town dwellers there are continually being swept into these glands from the bronchi
and alveoli large quantities of the dust and black carbonaceous pigment that are so freely
inhaled in cities. At first the glands are moderately enlarged, firm, inky black, and gritty on
section; later thej'- enlarge still further, often becoming fibrous from the irritation set up by
the minute foreign bodies with which they are crammed, and may break down into a soft slimy
mass or may calcify.
k
718
ANGIOLOGY
The lymphatic vessels of the thoracic viscera comprise those of the heart an(3
pericardium, lungs and pleura, thymus, and esophagus.
The Lymphatic Vessels of the Heart consist of two plexuses: (a) deep, immediately
under the endocardium; and (6) superficial, subjacent to the visceral pericardium.
The deep plexus opens into the superficial, the efferents of which form right and
left collecting trunks. The left trunks, two or three in number, ascend in the anterior
longitudinal sulcus, receiving, in their course, vessels from both ventricles. On
reaching the coronar}' sulcus they are joined by a large trunk from the diaphragmatic
surface of the heart, and then unite to form a single vessel which ascends between
the pulmonary artery and the left atrium and ends in one of the tracheobronchial
L. recurrent nerve
Parairacheal glands
R. recurrent nerve
Paratracheal glands
Q|/ // Innominate artery
L. Iracheohronchial
glands
L. bronchopulmo-
nary glands
i?. trachedbro7ichial
gland.^
E. hronchopulmo-
niiry glands
Fig. 622. — The tracheobronchial lymph glands. (From a figure designed by M. Hall6.)
glands. The right trunk receives its afferents from the right atrium and from the
right border and diaphragmatic surface of the right ventricle. It ascends in the
posterior longitudinal sulcus and then runs forward in the coronary sulcus, and
passes up behind the pulmonary artery, to end in one of the tracheobronchial
glands.
The Lymphatic Vessels of the Lungs originate in two plexuses, a superficial and a
deep. The superficial plexus is placed beneath the pulmonary pleura. The deep
accompanies the branches of the pulmonary vessels and the ramifications of the
bronchi. In the case of the larger bronchi the deep plexus consists of two net-works
— one, submucous, beneath the mucous membrane, and another, peribronchial,
outside the walls of the bronchi. In the smaller bronchi there is but a single plexus,
which extends as far as the bronchioles, but fails to reach the alveoli, in the walls
THE LYMPHATICS OF THE THORAX 719
of which there are no traces of lymphatic vessels. The superficial efferents turn
around the borders of the lungs and the margins of their fissures, and converge to
end in some glands situated at the hilus; the deep efferents are conducted to the
hilus along the pulmonary vessels and bronchi, and end in the tracheobronchial
glands. Little or no anastomosis occurs between the superficial and deep lym-
phatics of the lungs, except in the region of the hilus.
The Lymphatic Vessels of the Pleura consist of two sets — one in the visceral
and another in the parietal part of the membrane. Those of the visceral pleura
drain into the superficial efferents of the lung, while the lymphatics of the parietal
pleura have three modes of ending, viz.: (a) those of the costal portion join the
lymphatics of the Intercostales interni and so reach the sternal glands; (6) those
of the diaphragmatic part are drained by the efferents of the diaphragm; while
(c) those of the mediastinal portion terminate in the posterior mediastinal glands.
The Lymphatic Vessels of the Thymus end in the anterior mediastinal, tracheo-
bronchial, and sternal glands.
The Lymphatic Vessels of the Esophagus form a plexus around that tube, and the
collecting vessels from the plexus drain into the posterior mediastinal glands.
BIBLIOGRAPHY.
Bartels, p. : Das Lymphgefilsssystem, Bardeleben's Handbuch der Anatomie des Menschen,
1909.
Clark, E. R. : Observations on Living, Growing Lymphatics in the Tail of the Frog Larva,
Anat. Rec, 1909, iii.
Huntington, G.: The Genetic Principles of the Development of the Systemic Lymphatic
Vessels in the Mammalian Embryo, Anat. Rec, 1910, iv.
Huntington and McClure: The Anatomy and Development of the Jugular Lymph Sacs
in the Domestic Cat, Am. Jour. Anat., 1910, x.
Sappy: Description et Iconographie des Vaisseaux Lymphatiques, Paris, 1885.
Sabin, F. R.: The Development of the Lymphatic System, Keibel and Mall, Manual of
Human Embryology, 1912.
Teichman: Das Saugadermsy.stem, Leipzig, 1861.
NEUROLOGY.
THE Nervous System is the most complicated and highly organized of the various
systems which make up the human body. It is the mechanism concerned
with the correlation and integi'ation of various bodily processes and the reactions
and adjustments of the organism to its enviroimient. In addition the cerebral
cortex is concerned with conscious life. It may be divided into two parts, central
and peripheral.
The central nervous system consists of the encephalon or brain, contained within
the cranium, and the medulla spinalis or spinal cord, lodged in the vertebral canal;
the two portions are continuous with one another at the level of the upper border
of the atlas vertebra.
The peripheral nervous system consists of a series of nerves by which the central
nervous system is connected with the various tissues of the body. For descriptive
purposes these nerves may be arranged in two groups, cerebrospinal and sympathetic,
the arrangement, however, being an arbitrary one, since the two groups are inti-
mately connected and closely intermingled. Both the cerebrospinal and sym-
pathetic nerves have nuclei of origin (the somatic efferent and sympathetic efferent)
as well as nuclei of termination (somatic afferent and sympathetic afferent) in the
central nervous system. The cerebrospinal nerves are forty-three in number on
either side — twelve cranial, attached to the brain, and thirty-one spinal, to the
medulla spinalis. They are associated with the functions of the special and gen-
eral senses and with the voluntary movements of the body. The sympathetic
nerves transmit the impulses which regulate the movements of the viscera,
determine the caliber of the bloodvessels, and control the phenomena of secre-
tion. In relation with them are two rows of central ganglia, situated one on
either side of the middle line in front of the vertebral column; these ganglia are
intimately connected with the medulla spinalis and the spinal nerves, and are also
joined to each other by vertical strands of nerve fibers so as to constitute a pair
of knotted cords, the sympathetic trunks, which reach from the base of the skull
to the coccyx. The sympathetic nerves issuing from the ganglia form three great
prevertebral plexuses which supply the thoracic, abdominal, and pelvic viscera;
in relation to the walls of these viscera intricate nerve plexuses and numerous
peripheral ganglia are found.
STRUCTURE OF THE NERVOUS SYSTEM.
The nervous tissues are composed of nerve cells and their various processes,
together with a supporting tissue called neuroglia, which, however, is found only
in the brain and medulla spinalis. Certain long processes of the nerve cells are of
special importance, and it is convenient to consider them apart from the cells;
they are known as nerve fibers.
To the naked eye a difference is obvious between certain portions of the brain
and medulla spinalis, viz., the gray substance and the white substance. The gray
substance is largely composed of nerve cells, while the white substance contains
only their long processes, the nerve fibers. It is in the former that nervous impres-
sions are received, stored, and transformed into efferent impulses, and by the latter
4b ( 721 )
722
NEUROLOGY
that they are conducted. Hence the gray substance forms the essential constituent
of all the ganglionic centers, both those in the isolated ganglia and those aggregated
in the brain and medulla spinalis; while the white substance forms the bulk of the
commissural portions of the nerve centers and the peripheral nerves.
Neuroglia.- — Neuroglia, the peculiar ground.substance in which are imbedded the
true nervous constituents of the brain and medulla spinalis, consists of cells and
fibers. Some of the cells are stellate in shape, with ill-defined cell body, and their
fine processes become neuroglia fibers, which extend radially and unbranched
(Fig. 623, B) among the nerve cells and fibers which they aid in supporting. Other
cells give off fibers which branch repeatedly (Fig. 623, A). Some of the fibers start
from the epithelial cells lining the ventricles of the brain and central canal of
the medulla spinalis, and pass through the nervous tissue, branching repeatedly
to end in slight enlargements on the pia mater. Thus, neuroglia is evidently a
connective tissue in function but is not so in development; it is ectodermal in
origin, whereas all connective tissues are mesodermal.
Fig. 623. — Neuroglia cells of brain shown by Golgi's method. A. Cell with branched processes. B. Spider cell
with unbranched processes. (After Andriezen.)
Nerve Cells (Fig. 624). — Xerve cells are largely aggregated in the gray substance
of the brain and medulla spinalis, but smaller collections of these cells also form
the SAvellings, called ganglia, seen on many nerves. These latter are found chiefly
upon the spinal and cranial nerve roots and in connection with the sympathetic
nerves.
The nerve cells vary in shape and size, and have one or more processes. They
may be divided for purposes of description into three groups, according to the
number of processes which they possess: (1) Unipolar cells, which are found in
the spinal ganglia; the single process, after a short course, divides in a T-shaped
manner (Fig. 624, E). (2) Bipolar cells, also found in. the spinal ganglia (Fig. 625),
when the cells are in an embryonic condition. They are best demonstrated in the
spinal ganglia of fish. Sometimes the processes come off from opposite poles of
the cell, and the cell then assumes a spindle shape; in other cells both processes
emerge at the same point. In some cases where two fibers are apparently con-
nected with a cell, one of the fibers is really derived from an adjoining nerve cell
and is passing to end in a ramification around the ganglion cell, or, again, it may
be coiled spirally around the nerve process which is issuing from the cell. (3)
Multipolar cells, which are pyramidal or stellate in shape, and characterized by
their large size and by the numerous processes which issue from them. The
i
STRUCTURE OF THE NERVOUS SYSTEM
723
processes are of two kinds: one of them is termed the axis-cylinder process or axon
because it becomes the axis-cylinder of a nerve fiber (Figs. 026, 627, 628). The
others are termed the protoplasmic processes or dendrons; they begin to divide and
Fig. 624.— Various forms of nerve oeUs A. Pyramidal cell. B. Small multipolar cell, in which the axon quickly
divides into numerous branches. C. Small fusiform cell. D and K. Ganglion cells (E shows T-shaped division of
axon), ax. Axon, c Capsule.
Axon
Sheath of
cell body
Nucleus
Cell -protoplasm
Axon
2fuckolii3
Fig. C26. — Motor nerve cell from ventral horn of medulla
spinalis of rabbit. The angular and spindle-shaped Nissl
bodies are well shov/n. (After Nissl.)
subdivide soon after they emerge from the
cell, and finally end in minute twigs and be-
come lost among the other elements of the
nervous tissue. - ..< -
The body of the nerve cell, known as the
cyton, consists of a finely fibrillated proto-
plasmic material, of a reddish or yellowish-
brown color, which occasionally presents
patches of a deeper tint, caused by the ag-
gregation of pigment granules at one side of
the nucleus, as in the substantia nigra and
locus cteruleus of the brain. The protoplasm also contains peculiar angular gran-
ules, which stain deeply with basic dyes, such as methylene blue; these are known
as Nissl's granules (Fig. 626). They extend into the dendritic processes but not
into the axis-cylinder; the small clear area at the point of exit of the axon in
Dendron
-Myelin sheath
Fig, 625. — Bipolar nerve cell from the sjjinal gan-
glion of the pike. (.After KoUiker.)
>
724
NEUROLOGY
some cell t^-pes is termed the cone of origin. These granules disappear (chromato-
lysis) during fatigue or after prolonged stimulation of the nerve fibers connected
with the cells. They are supposed to represent a store of nervous energy, and
in various mental diseases are deficient or absent. The nucleus is, as a rule, a
large,^ well-defined, spherical body, often presenting an intranuclear network, and
containing a well-marked nucleolus.
Fia. 627. — Pyramidal cell from the cerebral cortex
of a mouse. (After Ramon y Cajal.)
Fig. 628. — Cell of Purkinje from the cerebellum. Golgi
method. (Cajal.) a. Axon. b. CoUateral. c and d.
Dendrons.
In addition to the protoplasmic network described above, each nerve cell may
be shown to have delicate neurofibrils running through its substance (Fig. 629);
these fibrils are continuous with the fibrils of the axon, and are believed to
convey ner\e impulses. Golgi has also described an extracellular network, which
is probably a supporting structure.
Nerve Fibers. — Nerve fibers are found universally in the peripheral nerves
and in the white substance of the brain and medulla spinalis. The}' are of two
kinds — viz., meduUated or white fibers, and non-medullated or gray fibers.
The medullated fibers form the white part of the brain and medulla spinalis, and
also the greater part of every cranial and spinal nerve^ and give to these structures
STRUCTURE OF THE NERVOUS SYSTEM
725
their opaque, white aspect. When perfectly fresh they appear to be homogeneous;
but soon after removal from the body each fiber presents, when examined by trans-
mitted light, a double outline or contour, as if consisting of two parts (Fig. 630).
The central portion is named the axis - cylinder ; around this is a sheath of fatty
material, staining black with osmic acid, named the white substance of Schwann
or medullary sheath, which gives to the fiber its double contour, and the whole
is enclosed in a delicate membrane, the neurolemma, primitive sheath, or nucleated
sheath of Schwann (Fig. 633)
Fig. 629. — Nerve cells of kitten, showing neurofibrils. (Cajal.) a. .\xou. 6. Cyton. c. Nucleus, d. Neurofibrils.
The axis-cylinder is the essential part of the nerve fiber, and is always present;
the medullary sheath and the neurolemma are occasionally absent, expecially at
the origin and termination of the nerve fiber. The axis-cylinder undergoes no
interruption from its origin in the nerve center to its peripheral termination, and
must be regarded as a direct prolongation of a nerve cell. It constitutes about
one-half or one-third of the nerve fiber, being greater in proportion in the fibers
of the central organs than in those of the nerves. It is quite transparent, and is
therefore indistinguishable in a perfectly fresh and natural state of the nerve.
It is made up of exceedingly fine fibrils, which stain darkly with gold chloride
(Fig. 632), and at its termination may be seen to break up into these fibrillse. The
fibrillse have been termed the primitive fibrillae of Schultze. The axis-cylinder is
said by some to be enveloped in a special reticular sheath, which separates it from
the medullary sheath, and is composed of a substance called neurokeratin. The
more common opinion is that this network or reticulum is contained in the white
726
NEUROLOGY
matter of Schwann, and by some it is believed to be produced by the action of
the reagents employed to show it.
The medullary sheath, or white matter of Schwami (Fig. 031), is regarded as being a
fatty matter in a fluid state, which insulates and protects the essential part of the
nerve — the axis-cylinder. It varies in thickness, in some forming a layer of extreme
Incisure
Node of Ranvier
y \\[|
Fig. 030.— Medullatcd nerve fibers. X 350.
Incisure
Nucleus -""'"'^•■^ ' 'I™' ^ ^"^^ "■'■ ^"^^■^''
Neurolemma
Medullary sheath
Axis-cylinder
Fig. 631. — Diagram of longitudinal sections of medullated
nerve fibers. Osmic acid.
Axis-cylinder
Neurolemma
Medullary sheath
Fig. 632. — Transverse sections of medullated nerve fibers.
Osmic acid.
Fig. 033. — Diagram of medullated nerve fibers
stained with osmic acid. X 425. (Schafer.) R.
Nodes of Ranvier. a. Neurolemma, c. Nucleus.
thinness, so as to be scarcely distinguishable, in others forming about one-half the
nerve fiber. The variation in diameter of the nerve fibers (from 2 to 16/i) depends
mainly upon the amount of the white substance, though the axis cylinder also
varies within certain limits. The medullary sheath undergoes interruptions in its
continuity at regular intervals, giving to the fiber the appearance of constriction
STRUCTURE OF THE NERVOUS SYSTEM
727
at these points: these are known as the nodes of Ranvier (Fi^s. 631 and 633). The
portion of nerve fiber between two nodes is called an internodal segment. The
neurolemma or primitive sheath is not interrupted at the nodes, but passes over
them as a continuous membrane. If the fiber be treated with silver nitrate the
reagent penetrates the neurolemma at the nodes, and on exposure to light reduction
takes place, giving rise to the appearance of black crosses, Ranvier's crosses, on the
axis-cylinder. There may also be seen transverse lines beyond the nodes termed
Frommann's lines (Fig. 634); the significance of these is not understood. In addi-
tion to these interruptions oblique clefts may be seen in the medullary sheath,
subdividing it into irregular portions, which are termed medullary segments, or
segments of Lantermann (Fig. 631); there is reason to believe that these clefts are
artificially produced in the preparation of the specimens. Medullated nerve
fibers, when examined in the fresh condition, frequently present a beaded or vari-
cose appearance: this is due to manipulation and pressure causing the oily matter
to collect into drops, and in consequence of the extreme delicacy of the primitive
sheath, even slight pressure will cause the transudation of the fatty matter, which
collects as drops of oil outside the membrane.
^ ;
1
i i
: ir ■*•
i
iSi;
• ■ i !
1 ;
i !:
■ ■= 1
i
Frommann's
11 " '^
M
''i ■
M':
■i j
' ^
liTies
||
r J' 11 a.
i!
''■■\
: '■ ^
Node of
\MJI : ' I
1 I: hiW
M
: :1 ;
=i
Banvier
^ I
ni/ H^/iN.
'. '■■
: '/\\
3
If]
V I
' % '
r
^
'! * / •
; i
lli\
i;
/ •■
\ ■
f ■ '
■\
1
/M
\;
1
.1
'
''\
■ •
■:
'/
7 ,■:
■ - ;■
■/..
\
i
■ '.V
U
h
i/t
i
: 1
::p
■ \ r
.1
1 ll^
.(
V:
i ■. .
'-i]!ll
\ il
i
1
Fig. 634. — Medullated nerve fibers stained with silver nitrate.
Fig. 635. — A small nervous branch
from the sympathetic of a mammal,
a. Two mediillated nerve fibers among
a number of gray nerve fibers, b.
The neurolemma or primitive sheath presents the appearance of a delicate,
structureless membrane. Here and there beneath it, and situated in depressions
in the white matter of Schwann, are nuclei surrounded by a small amount of
protoplasm. The nuclei are oval and somewhat flattened, and bear a definite
relation to the nodes of Ranvier, one nucleus generally lying in the center of each
internode. The primitive sheath is not present in all medullated nerve fibers,
being absent in those fibers which are found in the brain and medulla spinalis.
Wallerian Degeneration. — When nerve fibers are cut across, the central ends of the fibers
degenerate as far as the first node of Ranvier; but the peripheral ends degenerate simultaneously
throughout their whole length. The axons break up into fragments and become surrounded by
drops of fatty substance which are formed from the breaking down of the medullary sheath.
The nuclei of the primitive sheath proliferate, and finally absorption of the axons and fatty
substance occurs. If the cut ends of the nerve be sutured together regeneration of the nerve
fibers takes place by the downgrowth of axons from the central end of the nerve. At one time
it was beUeved that the regeneration was peripheral in origin, but this has been disproved, the
proHferated nuclei in the peripheral portions taking part merely in the formation of the so-called
scaffolding along which the new axons pass.
728 NEUROLOGY
Non-medullated Fibers. — Most of the fibers of the sympathetic system, and
some of the cerebrospinal, consist of the gray or gelatinous nerve fibers {fibers of
Remak) (Fig. 635). Each of these consists of an axis-cylinder to which nuclei are
applied at intervals. These nuclei are believed to be in connection with a delicate
sheath corresponding with the neurolemma of the medullated nerve fiber. In
external appearance the non-medullated nerve fibers are semitransparent and gray
or yellowish gray. The individual fibers vary in size, generally averaging about
half the size of the medullated fibers.
Structure of the Peripheral Nerves and Ganglia. — The cerebrospinal nerves con-
sist of numerous n&v\e fibers collected together and enclosed in membranous sheaths
(Fig. 636). A small bundle of fibers, enclosed in a tubular sheath, is called a
funiculus; if the nerve is of small size, it may consist only of a single funiculus; but
if large, the funiculi are collected together into larger bundles or fasciculi, which
are bound together in a common membranous investment. In structure the
common membranous investment, or sheath of the whole nerve (epineurium), as
well as the septa given oft' from it to separate the fasciculi, consist of connective
tissue, composed of white and yellow elastic fibers, the latter existing in great
abundance. The tubular sheath of the funiculi (perineurium) is a fine, smooth,
transparent membrane, which may be easily separated, in the form of a tube, from
the fibers it encloses; in structure it is made up of connective tissue, which has a
distinctly lamellar arrangement. The nerve fibers are held together and supported
within the funiculus by delicate connective tissue, called the endoneurium. It is
continuous with septa which pass inward from the innermost layer of the peri-
neurium, and shows a ground substance in which are imbedded fine bundles of
fibrous connective tissue running for the most part longitudinally. It serves to
support capillary vessels, arranged so as to form a net-work Avith elongated meshes.
The cerebrospinal nerves consist almost exclusively of medullated nerve fibers,
only a Aery small proportion of non-medullated being present.
The bloodvessels supplying a nerve end in a minute capillary plexus, the vessels
composing which pierce the perineurium, and run, for the most part, parallel with
the fibers; they are connected together by short, transverse vessels, forming narrow,
oblong meshes, similar to the capillary system of muscle. Fine non-medullated
nerve fibers, vasomotor fibers, accompany these capillary vessels, and break up into
elementary fibrils, which form a network around the vessels. Horsley has demon-
strated certain medullated fibers running in the epineurium and terminating in
small spheroidal tactile corpuscles or end bulbs of Krause. These nerve fibers, which
INIarshall belieA'es to be sensory, and which he has termed nervi nervorum, are con-
sidered by him to have an important bearing upon certain neuralgic pains.
The nerve fibers, so far as is at present kno^^^l, do not coalesce, but pursue an
uninterrupted course from the center to the periphery. In separating a nerve,
however, into its component funiculi, it may be seen that these do not pm^sue a
perfectly insulated course, but occasionally join at a very acute angle with other
funiculi proceeding in the same direction; from this, branches are given oft", to joint
again in like manner with other funiculi. It must be distinctly understood, however,
that in these communications the individual nerve fibers do not coalesce, but
merely pass into the sheath of the adjacent nerve, become intermixed with its nerve
fibers, and again pass on to intermingle with the nerve fibers in some adjoining
funiculus.
Nerves, in their course, subdivide into branches, and these frequently communi-
cate w^th branches of a neighboring nerve. The communications which thus take
place form what is called a plexus. Sometimes a plexus is formed by the primary
branches of the trunks of the nerves — as the cervical, brachial, lumbar, and sacral
plexuses — and occasionally by the terminal funiculi, as in the plexuses formed at
the periphery of the body. In the formation of a plexus, the component nerves
STRUCTURE OF THE NERVOUS SYSTEM
729
divide, then join, and again subdivide in such a complex manner that the in(hvi(hial
funicuh become inteHaced most intricately; so that each branch Iea\in2; a plexus
may contain filaments from all the primary nervous trunks which form tlie plexus.
In the formation also of smaller plexuses at the periphery of the body there is a
free interchange of the funiculi and jirimitive fibers. In each case, however, the
individual hbers remain sejjarate and distinct.
It is probable that through this interchange of fibers, every branch passing off
from a plexus has a more extensi^•e connection with the spinal cord than if it had
proceeded to its distribution without forming connections with other nerves.
Consequently the parts supplied by these nerves have more extended relations
with the nervous centers; by this means, also, groups of muscles may be associated
for combined action.
/■,
•N.^-
\
Epineurium
Perineurium
^
^ -0
""mm
i'ii%rx\
Fig. 636. — Transverse section of human tibial nerve.
The sympathetic nerves are constructed in the same manner as the cerebrospinal
nerves, but consist mainly of non-medullated fibers, collected in funiculi and enclosed
in sheaths of connective tissue. There is, however, in these nerves a certain admix-
ture of medullated fibers. The number of the latter varies in different nerves, and
may be estimated by the color of the nerve. Those branches of the s^Tupathetic,
which present a well-marked gray color, are composed chiefly of non-medullated
nerve fibers, intermixetl v.ith a few medullated fibers; while those of a white color
contain manv of the latter fibers, and few of the former.
The cerebrospinal and s^inpathetic nerve fibers convey various impressions.
The sensory nerves, called also centripetal or afferent nerves, transmit to the nervous
centers impressions maile upon the peripheral extremities of the ner^'es, and in this
way the mind, through the medium of the brain, becomes conscious of external
objects. The centrifugal or efferent nerves transmit impressions from the nervous
centers to the parts to which the nerves are distributed, these impressions either
exciting muscular contraction or influencing the processes of nutrition, gro^^th,
and secretion.
Origins and Terminations of Nerves. — By the expression "the terminations of
nerve fibers" is signified their connections with the nerve centers and with the parts
730 NEUROLOGY
they supply. The former are sometimes called their origins or central terminations;
the latter their peripheral terminations.
Origins of Nerves. — The origin in some cases is single — that is to say, the whole
nerve emerges from the nervous center by a single root; in other instances the nerve
arises by two or more roots which come ofl" from difi'erent parts of the nerve center,
sometimes widely apart from each other, and it often happens, when a nerve arises
in this way by two roots, that the functions of these two roots are different; as, for
example, in the spinal nerves, each of which arises by two roots, the anterior of
which is motor, and the posterior sensory. The point where the nerve root or
roots emerge from the surface of the nervous center is named the superficial or
apparent origin, but the fibers of the nerve can be traced for a certain distance into
the substance of the nervous center to some portion of the gray matter, which
constitutes the deep or real origin of the nerve. The centrifugal or efferent nerve
fibers originate in the nerve cells of the gray substance, the axis-cylinder processes
of these cells being prolonged to form the fibers. In the case of the centripetal or
afferent nerves the fibers grow inward either from nerve cells in the organs of special
sense, e. g., the retina, or from nerve cells in the ganglia. Having entered the nerve
center they branch and send their ultimate twigs among the cells, without, however,
uniting with them.
Peripheral Terminations of Nerves. — Nerve fibers terminate peripherally in various
ways, and these may be conveniently studied in the sensory and motor nerves
respectively. The terminations of the sensory nerves are dealt with in the section
on Sense Organs.
Motor nerves can be traced into either unstriped or striped muscular fibers. In
the utuiriped or involuntary muscles the ner\-es are derived from the sympathetic,
and are composed mainly of non-medullated fibers. Near their terminations they
di^■ide into niunerous branches, which communicate and form intimate plexuses.
At the junction of the branches small triangular nuclear bodies (ganglion cells) are
situated. From these plexuses minute branches are given off which divide and
break up into the ultimate fibrillar of which the nerves are composed. These
fibrillar course between the involuntary muscle cells, and, according to Elischer,
terminate on the surfaces of the cells, opposite the nuclei, in minute swellings.
In the striped or vohtntary muscle the nerves supplying the muscular fibei-s are
derived from the cerebrospinal ner\es, and are composed mainly of medullated
fibers. The ner^'e, after entering the sheath of the muscle, breaks up into fibers or
bundles of fibers, which form plexuses, and gradually divide until, as a rule, a single
nerve fiber enters a single muscular fiber. Sometimes, however, if the muscular
fiber be long, more than one ner^■e fiber enters it. Within the muscular fiber the
nerve terminates in a special expansion, called by Kiihne, who first accurately
described it, a motor end-plate (Fig. 637). The nerAC fiber, on approaching the mus-
cular fiber, suddenly loses its medullary sheath, the neurolemma becomes continuous
with the sarcolemma of the muscle, and only the axis-cylinder enters the muscular
fiber. There it at once spreads out, ramifying like the roots of a tree, immediately
beneath the sarcolemma, and becomes imbedded in a layer of granular matter,
containing a number of clear, oblong nuclei, the whole constituting an end-plate
from which the contractile wave of the muscular fiber is said to start.
Ganglia are small aggregations of nerve cells. They are found on the posterior
roots of the spinal ner\es; on the sensory roots of the trigeminal, facial, glosso-
pharyngeal, and vagus nerves, and on the acoustic nerves. They are also lound in
connection with the snnpathetic nerves. On section they are seen to consist of a
reddish-gray substance, traversed by numerous white nerve fibers; they vary con-
siderably in form and size; the largest are found in the cavity of the abdomen;
the smallest, not visible to the naked eye, exist in considerable numbers upon the
nerves distributed to the different viscera. Each ganglion is invested by a smooth
STRUCTURE OF THE NERVOUS SYSTEM
731
and firm, closely adhering, membranous en\elope, consisting of dense areolar
tissue; this sheath is continuous with the perineurium of the nerves, and sends
numerous processes into the interior to support the bloodvessels supplying the
substance of the ganglion.
mmm IfH^W^l'WJW'lZW WH^^Bm
■- •:.:::;:::,:„'>^"-S(-"r3
ilifi!'\r','.!"'.'.'.nl"!!iI"'."'.'.'J
TuwirmTilmEKif
■ ^.ff-r'—fij-'.'P-s "'..'At':}--
feTiTTrJ'r'Miu" '■"
.TX-^
Fig. 637. — Muscular fibers of Lacerta vxridis with the terminations of nerves, a. Seen in profile. P, P. The nerve
end-plates. S. S. The base of the plate, consisting of a granular mass with nuclei, h. The same as seen in looking at
a perfectly fresh fiber, the nervous ends being probably still excitable. (The forms of the variously divided plate can
hardly be represented in a woodcut by sufficiently delicate and pale contours to reproduce correctly what is seen in
nature.) c. The same as seen two hours after death from poisoning by curare.
In structure all ganglia are essentially similar, consisting of the same structural
elements — viz., nerve cells and nerve fibers. Each nerve cell has a nucleated sheath
which is continuous with the neurolemma of the nerve fiber with which the cell is
connected. The nerve cells in the ganglia of the spinal nerves (Fig. 038) are p^Ti-
form in shape, and have each a single process. A short distance from the cell and
while still within the ganglion this process divides in a T-shaped manner, one
limb of the cross-bar turning into the medulla spinalis, the other limb passing out-
FiG.''l>3S. — Transverse section of spinal ganglion of rabbit. .-1. GangUon. X 30. a. Large clear nerve cell. 6.
Small deeply staining nerve cell. c. Nuclei of capsule. X 250. The lines in the center point to the corresponding
cells in the ganglion.
V ard to the periphery. In the s\Tnpathetic ganglia (Fig. 639) the nerve cells are
multipolar and each has one axis-cylinder process and several dendrons; the axon
emerges from the ganglion as a non-medullated nerve fiber. Similar cells are found
in the ganglia connected with the trigeminal nerve, and these ganglia are therefore
732
XE UROLOGY
regarded as the cranial portions of the s^^npathetic system. The sxanpathetic
nervous system inchides those portions of the nervous mechanism in which a medul-
lated nerve fiber from the central system passes to a ganglion, sympathetic or
peripheral, from which fibers, usually non-medullated, are distributed to such
structures, e. g., blood^'essels, as are not under voluntary control. The spinal and
sympathetic ganglia difl'er somewhat in the size and disposition of the cells and in
the number of nerve fibers entering and leaving them. In the spinal ganglia (Fig.
638) the nerve cells are much larger and for the most part collected in groups near
the periphery, while the fibers, which are mostly medullated. traverse the central
portion of the ganglion; whereas in
Nerve-cells of ganglion the sympathetic ganglia (Fig. 639)
the cells are smaller and distributed
in irregular groups throughout the
whole ganglion; the fibers also are
irregularly scattered; some of the
entering ones are medullated, while
many of those leaving the ganglion
are non-medullated.
Neuron Theory. — The nerve cell
and its processes collectively con-
stitute what is termed a neuron, and
AValdeyer formulated the theory
that the nervous system is built up
of nmnerous neurons. " anatomically
and genetically independent of one
another." According to this theory
{neuron iheory) the processes of
one neuron only come into con-
tact, and are never in direct con-
tinuity, with those of other neu-
rons; while impulses are transmitted from one nerve cell to another through
these points of contact, the synapses. The synapse or synaptic membrane seems
to allow nervous impulses to pass in one direction only, namely, from the terminals
of the axis-cylinder to the dendrons. This theory is based on the following facts,
viz. : (1) embryonic nerve cells or neuroblasts are entirely distinct from one another;
(2) when nervous tissues are stained by the Golgi method no continuity is seen even
between neighboring neurons; and (3) when degenerative changes occur in nervous
tissue, either as the result of disease or experiment, they never spread from one
neuron to another, but are limited to the individual neurons, or groups of neurons,
primarily aftected. It must, however, be added that within the past few years the
validity of the neuron theory has been called in question by certain eminent histol-
ogists, who maintjiin that by the emplo\Tnent of more delicate histological methods,
minute fibrils can be followed from one nerve cell into another. Their existence,
howe^■er, in the living is open to question. ^lott and Marinesco made careful
examinations of living cells, using even the ultramicroscope and agree that neither
Nissl bodies nor neurofibrils are present in the living state.
For the present we may look upon the neurons as the units or structural elements
of the ner^•ous system. All the neurons are present at birth which are present in
the adult, their di^•ision ceases before birth; thev are not all functionalh^ active
at birth, but gradually assume functional activity. There is no indication of any
regeneration after the destruction of the cell-body of any individual neuron.
Fasciculi, tracts or fiber systems are groups of axons having homologous origin
and homologous distribution (as regards their collaterals, subdivisions and ter-
minals) and are often named in accordance with their origin and termination, the
P^G. 639. — Transverse section of sj-mpathetic ganglion of cat.
A. Ganglion. X 50. a. A nerve cell. X 250.
DEVELOPMENT OF THE NERVOUS SYSTEM
733
name of the nucleus or the location of the cell body from which the axon or fiber
arises preceding that of the nucleus or location of its termination. A. given topo-
graphical area seldom represents a pure tract, as in most cases fibers of different
systems are mixed.
DEVELOPMENT OF THE NERVOUS SYSTEM.
The entire nervous system is of ectodermal origin, and its first rudiment is seen
in the neural groove which extends along the dorsal aspect of the embryo (Fig.
17). By the elevation and ultimate fusion of the neural folds, the groove is con-
verted into the neural tube (Fig. 19). The anterior end of the neural tube becomes
expanded to form the three primary brain- vesicles; the cavity of the tube is sub-
sequently modified to form the ventricular cavities of the brain, and the central
canal of the medulla spinalis; from the wall the nervous elements and the neuroglia
of the brain and medulla spinalis are developed.
Roof-plate
Oval bundle
Posterior nerve root
Central canal
Ependymal layer
Mantle layer
Anterior nerve roots
Marginal layer
Floor-plate
Fig. 640. — Section of medulla spinalis of a four weeks' embryo. (His.)
The Medulla Spinalis. — At first the wall of the neural tube is composed of a
single layer of columnar ectodermal cells. Soon the side-walls become thickened,
while the dorsal and ventral parts remain thin, and are named the roof- and floor-
plates (Figs. 640, 042, 643). A transverse section of the tube at this stage presents
an oval outline, while its lumen has the appearance of a slit. The cells which
constitute the wall of the tube proliferate rapidly, lose their cell-boundaries and
form a syncytium. This syncytium consists at first of dense protoplasm with
closely packed nuclei, but later it opens out and forms a looser mesh work with
the cellular strands arranged in a radiating manner from the central canal. Three
layers may now be defined — an internal or ependymal, an intermediate or mantle,
and an external or marginal. The ependymal layer is ultimately converted into the
ependyma of the central canal; the processes of its cells pass outward toward
the periphery of the medulla spinalis. The marginal layer is devoid of nuclei, and
later forms the supporting framework for the white funiculi of the medulla spinalis.
The mantle layer represents the whole of the future gray columns of the medulla
spinalis; in it the cells are differentiated into two sets, viz., (a) spongioblasts or
young neuroglia cells, and (b) germinal cells, which are the parents of the neuroblasts
734
NEUROLOGY
or young nerve cells (Fig. 041). The spongioblasts are at first connected to one
another by filaments of the syncytium; in these, fibrils are developed, so that as the
neuroglial cells become defined they exhibit their characteristic mature appearance
with multiple processes proceeding from each cell. The germinal cells are large,
Germinal cell
Neuroblast
Nuclei of spongioblasts
Syncytium
Fig. 641. — Transv'erse section of the medulla spinalis of a human embryo at the beginning of the fourth week.
The left edge of the figure corresponds to the lining of the central canal. (His.)
round or oval, and first make their appearance between the ependymal cells on
the sides of the central canal. They increase rapidly in number, so that by the
fourth week they form an almost continuous layer on each side of the tube. No
germinal cells are found in the roof- or floor-plates; the roof-plate retains, in certain
Boqf-plate
Alar lamina
Oval bundle
Posterior
nerve-root
Central canal
Ependymal
layer
Lateral
funicuhis
Basal lamina
Floor-plate
Anterior
nerve-root
Anterior funiculus
Fasciculus gracilis ^ Posterior
Fasciculus cuneatv^J /"■^■iculus
—Post, nerve-root
Lateral
funiculus
Central canal
Anterior
column
Anterior funiculus
Figs. 6-12, 643. — Transverse sections through the medullae spinales of human embryos. (His.)
Fig. 642, aged about four and a half weeks. Fig. 643, aged about tbree months.
regions of the brain, its epithelial character; elsewhere, its cells become spongio-
blasts. By subdivision the germinal cells give rise to the neuroblasts or young
nerve cells, which migrate outward from the sides of the central canal into the
mantle layer and neural crest, and at the same time become pear-shaped; the
DEVELOPMENT OF THE NERVOUS SYSTEM 735
tapering part of the cell undergoes still further elongation, and forms the axis-
cylinder of the cell.
The lateral walls of the medulla spinalis continue to increase in thickness, and
the canal widens out near its dorsal extremity, and assumes a somewhat lozenge-
shaped appearance. The widest i)art of ,the canal serves to subdi^•ide the lateral
wall of the neural tube into a dorsal or alar, and a ventral or basal lamina (Figs. 642,
643) , a subdivision which extends forward into the brain. At a later stage the ventral
part of the canal widens out, while the dorsal part is first reduced to a mere slit
and then becomes obliterated by the approximation and fusion of its walls; the
ventral part of the canal persists and forms the central canal of the adult medulla
spinalis. The caudal end of the canal exliibits a conical expansion which is known
as the terminal ventricle.
The ventral part of the mantle layer becomes thickened,, and on cross-section
appears as a triangular patch between the marginal and ependymal layers. This
thickening is the rudiment of the anterior column of gray substance, and contains
many neuroblasts, the axis-cylinders of which pass out through the marginal layer
and form the anterior roots of the spinal nerves (Figs. 640,642, 643) . The thickening
of the mantle layer gradually extends in a dorsal direction, and forms the posterior
column of gray substance. The axons of many of the neuroblasts in the alar lamina
run forward, and cross in the floor-plate to the opposite side of the medulla spinalis;
these form the rudiment of the anterior white commissure.
About the end of the fourth week nerve fibers begin to appear in the marginal
layer. The first to develop are the short intersegmental fibers from the neuro-
blasts in the mantle zone, and the fibers of the dorsal nerve roots which grow into
the medulla spinalis from the cells of the spinal ganglia. By the sixth week these
dorsal root fibers form a well-defined oval bundle in the peripheral part of the alar
lamina; this bundle gradually increases in size, and spreading toward the middle
line forms the rudiment of the posterior funiculus. The long intersegmental fibers
begin to appear about the third month and the cerebrospinal fibers about the fifth
month. All nerve fibers are at first destitute of medullary sheaths. Different
groups of fibers receive their sheaths at different times — the dorsal and ventral
nerve roots about the fifth month, the cerebrospinal fibers after the ninth month.
By the growth of the anterior columns of gray substance, and by the increase
in size of the anterior funiculi, a furrow is formed between the lateral halves of the
cord anteriorly; this gradually deepens to form the anterior median fissure. The
mode of formation of the posterior septum is somewhat uncertain. Many believe
that it is produced by the growing together of the walls of the posterior part of the
central canal and by the development from its ependymal cells of a septum of
fibrillated tissue which separates the future funiculi graciles.
Up to the third month of fetal life the medulla spinalis occupies the entire
length of the vertebral canal, and the spinal nerves pass outward at right angles
to the medulla spinalis. From this time onward, the vertebral column grows more
rapidl}' than the medulla spinalis, and the latter, being fixed above through its
continuity with the brain, gradually assumes a higher position within the canal.
By the sixth month its lower end reaches only as far as the upper end of the sacrum;
at birth it is on a level with the third lumbar vertebra, and in the adult with the
lower border of the first or upper border of the second lumbar vertebra. A delicate
filament, the filum terminale, extends from its lower end as far as the coccyx.
The Spinal Nerves. — Each spinal nerve is attached to the medulla spinalis by
an anterior or ventral and a posterior or dorsal root.
The fibers of the anterior roots are formed by the axons of the neuroblasts
which lie in the ventral part of the mantle layer; these axons grow out through the
overlying marginal laver and become grouped to form the anterior nerve root
(Fig. 641).
736
NEUROLOGY
The fibers of the posterior roots are developed from the cells of the spinal ganglia.
Before the neural groove is closed to form the neural tube a ridge of ectodermal
cells, the ganglion ridge or neural crest (Fig. 044), appears along the prominent
margin of each neural fold. When the folds meet in the middle line the two gan-
glion ridges fuse and form a wedge-shaped area along the line of closure of the tube.
The cells of this area proliferate rapidly opposite the primitive segments and then
migrate in a lateral and ventral direction to the sides of the neural tube, where they
ultimately form a series of oval-shaped masses, the future spinal ganglia. These
ganglia are arranged symmetrically on the two sides of the neural tube and, except
in the region of the tail, are equal in number to the primitive segments. The cells
of the ganglia, like the cells of the mantle layer, are of two kinds, viz., spongio-
blasts and neuroblasts. The spongioblasts develop into the neuroglial cells of the
ganglia. The neuroblasts are at first round or oval in shape, but soon assume
the form of spindles the extremities of which gradually elongate into central and
peripheral processes. The central
processes grow medialward and, be-
coming connected with the neural
tube, constitute the fibers of the
posterior nerve roots, while the per-
ipheral processes grow lateralward to
mingle with the fibers of the anterior
root in the spinal nerve. As de-
velopment proceeds the original
bipolar form of the cells changes;
the two processes become approxi-
mated until they ultimately arise
from a single stem in a T-shaped
manner. Only in the ganglia of the
acoustic nerve is the bipolar form
retained . ]\Iore recent observers hold,
however, that the T-form is derived
from the branching of a single pro-
cess which grows out from the cell.
The anterior or ventral and the pos-
terior or dorsal nerve roots join imme-
diately beyond the spinal ganglion to form the spinal nerve, which then divides into
anterior, posterior, and visceral divisions. The anterior and posterior divisions
proceed directly to their areas of distribution without further association with
ganglion cells (Fig. 645). The visceral divisions are distributed to the thoracic,
abdominal, and pelvic viscera, to reach which they pass through the sympathetic
trunk, and many of the fibers form arborizations around the ganglion cells of this
trunk. Visceral branches are not given off from all the spinal nerves; they form
two groups, viz., (a) thoracico-lumbar, from the first or second thoracic, to the
second or third lumbar nerves; and (6) pelvic, from the second and third, or
third and fourth sacral nerves.
The Brain. — The brain is developed from the anterior end of the neural tube,
which at an early period becomes expanded into three vesicles, the primary cerebral
vesicles (Fig. 18). These are marked off from each other by intervening con-
strictions, and are named the fore-brain or prosencephalon, the mid-brain or
mesencephalon, and the hind-brain or rhombencephalon — the last being continuous
with the medulla spinalis. As the result of unequal growth of these different
parts three flexures are formed and the embryonic brain becomes bent on itself
in a somewhat zigzag fashion; the two earliest flexures are concave ventrally
and are associated with corresponding flexures of the whole head. The first flexure
FiQ. 644. — Two stages in the development of the neural
crest in the human embryo. (Lenhossfik.)
DEVELOPMENT OF THE NERVOUS SYSTEM
737
appears in the region of the mid-brain, and is named the ventral cephalic flexure
(Fig. 650). By means of it the fore-brain is bent in a ventral direction around
the anterior end of the notochord and fore-gut, with the result that the floor of
the fore-brain comes to lie almost parallel with that of the hind-brain. This
flexure causes the mid-brain to become, for a time, the most prominent part of
the brain, since its dorsal surface corresponds with the convexity of the curve.
Auditory vesicle
Facial and acoustic Ns. Glossopharyngeal N.
Trigeminal N. | Vagus N.
Trochlear N. ,. L I Accessory N.
Hypoglossal N.
Mesencephalon
Oculomotor N.^i
J
Die ncephalon — -
Cerebral
hemisphere
Froriep s
ganglion
1- Cervical
Phrenic N.
I. Thoracic
Vitelline loop
Tail
I. Coccygeal —
lyiimbar
I. Sacral
Pig. 645. — Reconstruction of periphera nerves of a liunian embrj-o of 10.2 mm. (After His.) The abducent nerve
is not labelled, but is seen passing forward to the eye under the mandibular and maxillary nerves.
The second bend appears at the junction of the- hind-brain and medulla spinalis.
'. This is termed the cervical flexure (Fig. 052), and increases from the third to the
: end of the fifth week, when the hind-brain forms nearly a right angle with the
: medulla spinalis; after the fifth week erection of the head takes place and the cervi-
cal flexure diminishes and disappears. The third bend is named the pontine flexure
(Fig. 652), because it is found in the region of the future pons Varoli. It difters
from the other two in that (a) its convexity is forward, and (6) it does not affect
47
738
NEUROLOGY
Alar lamina
mT'- "%K ^fc
Furrow between
oHmr^^.^J alar an
'W0' • -' Wl"<:'i la mince
i&Sf_it}S^ 'J alar and basal
Basal lamina
i^7::f^^^"'f*
Fig. 646. — Diagram to illustrate the alar and
basal laminsB of brain vesicles. (His.)
Vagus nerve
Hypoglossal n^^ve
Floor-plate
Fig. 647. — Transverse section of medulla oblongata of human
embr>-o. X 32. (Kollmann.)
Rhombic lip
Tract us
solitarius
Vagii-i nerve
Hypoglossal nerve
Floor-plate
Fig. 648. — Transverse section of medulla oblongata of human embrj-o. (After His.)
the head. The lateral walls of the brain-tiibe, like those of the medulla spinalis,
are divided by internal furrows into alar or dorsal and basal or ventral laminfe \
(Fig. 646). !
The Hind-brain or Rhombencephalon. — The cavity of the hind-brain becomes i
the fourth ventricle. At the time when the ventral cephalic flexure makes its i
Roof-plate
appearance, the length of the hind-brain exceeds the combined lengths of the other '
two vesicles. Immediately behind the mid-brain it exhibits a marked constriction, I
the isthmus rhombencephali (Fig. 650, Isthmus), which is best seen when the brain is I
viewed from the dorsal aspect. From the isthmus the anterior medullary velum ,
and the superior peduncle of the cerebellum are formed. It is customary to ,
«l
divide the rest of the hind-brain into two parts, viz., an upper, called the meten-
cephalon, and a lower, the myelencephalon. The cerebellum is developed by a
thickening of the roof, and the pons by a thickening in the floor and lateral walls
of the metencephalon. The floor and lateral walls of the myelencephalon are
thickened to form the medulla oblongata; its roof remains thin, and, retaining to
DEVELOPMENT OF THE NERVOUS SYSTEM
739
a great extent its epithelial nature, is expanded in a lateral direction. Later, by
the growth and backward extension of the cerebellum, the roof is folded inward
toward the cavity of the fourth ventricle; it assists in completing the dorsal wall
of this cavity, and is also invaginated to form the ependymal covering of its choroid
plexuses. Above it is continuous with the posterior medullary velum; below, wuth
the obex and ligulre.
The development of the medulla oblongata resembles that of the medulla spinalis,
but at the same time exhibits one or two interesting modifications. On transverse
section the myelencephalon at an early stage is seen to consist of two lateral walls,
connected across the middle line by floor- and roof-plates (Figs. 647 and 648).
Each lateral wall consists of an alar and a basal lamina, separated by an internal
furrow, the remains of which are represented in the adult brain by the sulcus
limitans on the rhomboid fossa. The contained cavity is more or less triangular
Ttznia
Ehombic lip
Optic stalk
V. N. Motor root
V. N. Sensory root
Oanglia of VII. and
VIII. Ns.
Auditory vesicle
Fig. 649. — Hind-brain of a human embryo of three
months — viewed from behind and partly from left side.
(From model by His.)
Fig. 650. — E.\terior of brain of human embryo of four
and a half weeks. (From model by His.)
in outline, the base being formed by the roof-plate, which is thin and greatly
expanded transversely. Pear-shaped neuroblasts are developed in the alar and
basal laminoe. and their narrow stalks are elongated to form the axis-cylinders of
the nerve fibers. Opposite the furrow or boundary between the alar and basal
laminse a bundle of nerve fibers attaches itself to the outer surface of the alar
lamina. This is named the tractus solitarius (Fig. 648), and is formed by the sensory
fibers of the glossopharyngeal and vagus nerves. It is the homologue of the oval
bundle seen in the medulla spinalis, and, like it, is developed by an ingrowth of
fibers from the ganglia of the neural crest. At first it is applied to the outer surface
of the alar lamina, but it soon becomes buried, owing to the growth over it of the
neighboring parts. By the fifth week the dorsal part of the alar lamina bends
in a lateral direction along its entire length, to form what is termed the rhombic
lip (Figs. 648, 649). ^YithiJl a few days this lip becomes applied to, and unites
740
NEUROLOGY
Garujlia of VII.
and VIII. Ns.
Auditory vesicle
Fig. 651. — Brain of human embrjo of four and a half weeks,
showing interior of fore-brain. (From model by His.)
The alar laminae of this
with, the outer surface of the main part of the alar lamina, and so covers in the
tractus solitarius and also the spinal root of the trigeminal nerve; the nodulus ■
and flocculus of the cerebellum are developed from the rhombic lip.
Neuroblasts accumulate in the mantle layer; those in the basal lamina corre-
spond with the cells in the anterior gray column of the medulla spinalis, and, like
them, give origin to motor nerve fibers; in the medulla oblongata they are, however,
arranged in groups or nuclei, instead of forming a continuous column. From the
alar lamina and its rhombic lip, neuroblasts migrate into the basal lamina, and
become aggregated to form the olivary nuclei, while many send their axis-cylinders
through the floor-plate to the opposite side, and thus constitute the rudiment of
the raphe of the medulla oblongata. By means of this thickening of the ventral
portion, the motor nuclei are buried deeply in the interior, and, in the adult, are
found close to the rhomboid fossa. This is still further accentuated: (a) by the
development of the pyramids, which
are formed about the fourth month
by the downward growth of the
motor fibers from the cerebral cortex;
and (b) by the fibers which pass to
and from the cerebellum. On the
rhomboid fossa a series of six tem-
porary furrows appears; these are
termed the rhombic grooves. They
bear a definite relationship to certain
of the cranial nerves; thus, from
before backward the first and second
grooves overlie the nucleus of the
trigeminal; the third, the nucleus of
the facial; the fourth, that of the ab-
ducent; the fifth, that of the glosso-
pharyngeal; and the sixth, that of
the vagus.
The pons is developed from the
ventro-lateral wall of the meten-
cephalon by a process similar to that
which has been described for the
medulla oblongata.
The cerebellum is developed in
the roof of the anterior part of
the hind-brain (Figs. 649 to 654).
region
become thickened to form two
lateral plates which soon fuse in the middle line and produce a thick lamina which
roofs in the upper part of the cavity of the hind-brain vesicle; this constitutes
the rudiment of the cerebellum, the outer surface of which is originally smooth
and convex. The fissures of the cerebellum appear first in the vermis and floccular
region, and traces of them are found during the third month; the fissures on the
cerebellar hemispheres do not appear until the fifth month. The primitive fissures
are not developed in the order of their relative size in the adult — thus the hori-
zontal sulcus in the fifth month is merely a shallow groove. The best marked
of the early fissures are: (o) the fissura prima between the developing culmen and
declive, and (6) the fissura secunda between the future pyramid and uvula. The
flocculus and nodule are developed from the rhombic lip, and are therefore recog-
nizable as separate portions before any of the other cerebellar lobules. The
groove produced by the bending over of the rhombic lip is here known as the
DEVELOPMENT OF THE NERVOUS SYSTEM
741
floccular fissure; when the two lateral walls fuse, the right and left floccular fissures
join in the middle line and their central part becomes the post-nodular fissure.
On the ventricular surface of the cerebellar lamina a transverse furrow, the
incisura fastigii, appears, and deepens to form the tent-like recess of the roof of the
fourth ventricle. The rudiment of the cerebellum at first projects in a dorsal
direction; but, by the backward growth of the cerebrum, it is folded downward and
somewhat flattened, and the thin roof-plate of the fourth ventricle, originally
continuous with the posterior border of the cerebellum, is projected inward toward
the cavity of the ventricle.
The Mid-brain or Mesencephalon.— The mid-brain (Figs. 650 to 654) exists for a
time as a thin-walled cavity of some size, and is separated from the isthmus rhomb-
encephali behind, and from the fore-brain in front, by slight constrictions. Its
cavity becomes relatively reduced in diameter, and forms the cerebral aqueduct
of the adult brain. Its basal laminae increase in thickness to form the cerebral
peduncles, which are at first of small size, but rapidly enlarge after the fourth month.
Ganglion habenvicB
1
Hypophysis cerebri
Fig. 652. — Exterior of brain of human embryo of five weeks. (From model by His.)
The neuroblasts of these laminae are grouped in relation to the sides and floor
of the cerebral aqueduct, and constitute the nuclei of the oculomotor and trochlear
nerves, and of the mesencephalic root of the trigeminal nerve. By a similar
thickening process its alar laminae are developed into the quadrigeminal lamina.
The dorsal part of the wall for a time undergoes expansion, and presents an internal
median furrow and a corresponding external ridge; these, however, disappear,
and the latter is replaced by a groove. Subsequently two oblique furrows extend
medialward and backward, and the thickened lamina is thus subdivided into the
superior and inferior colliculi.
The Fore-brain or Prosencephalon. — A transverse section of the early fore-brain
shows the same parts as are displayed in similar sections of the medulla spinalis
and medulla oblongata, viz., a pair of thick lateral walls connected by thin floor-
and roof-plates. Moreover, each lateral wall exhibits a division into a dorsal or
alar and a ventral or basal lamina separated internally by a furrow termed the sulcus
742
NEUROLOGY
of Monro. This sulcus ends anteriorly at the medial end of the optic stalk, and in
the adult brain is retained as a slight groove extending backward from the inter-
ventricular foramen to the cerebral aqueduct.
At a very early period — in some animals before the closure of the cranial part of
the neural tube — two lateral diverticula, the optic vesicles, appear, one on either
side of the fore-brain; for a time they communicate with the cavity of the fore-brain
by relatively wide openings. The peripheral parts of the vesicles expand, while
the proximal parts are reduced to tubular stalks, the optic stalks. The optic vesicle
gives rise to the retina and the epithelium on the back of the ciliary body and iris;
the optic stalk is invaded by nerve fibers to form the optic nerve. The fore-brain
then grows forward, and from the alar laminae of this front portion the cerebral
hemispheres originate as diverticula which rapidly expand to form two large
pouches, one on either side. The cavities of these diverticula are the rudiments of
the lateral ventricles; they communicate with the median part of the fore-brain
cavity by relatively wide openings, which ultimately form the interventricular
^/.
Choroidal fissure
Hypophysis
Recessiis infundibuU
Tuber cincreum
Corpus mamiliare,
Cervical flexure
Fig. 653. — Interior of brain of human embryo of five weeks. (From model by His.)
foramen. The median portion of the wall of the fore-brain vesicle consists of a
thin lamina, the lamina terminalis (Figs. 654, 657), which stretches from the
interventricular foramen to the recess at the base of the optic stalk. The
anterior part of the fore-brain, including the rudiments of the cerebral hemi-
spheres, is named the telencephalon, and its posterior portion is termed the
diencephalon; both of these contribute to the formation of the third ventricle.
The Diencephalon. — From the alar lamina of the diencephalon, the thalamus,
metathalamus, and epithalamus are developed. The thalamus (Figs. 650 to 654)
arises as a thickening which involves the anterior two-thirds of the alar lamina.
The two thalami are visible, for a time, on the surface of the brain, but are subse-
quently hidden by the cerebral hemispheres which grow backward over them.
The thalami extend medialward and gradually narrow the cavity between them
into a slit-like aperture which forms the greater part of the third ventricle; their
medial surfaces ultimately adhere, in part, to each other, and the intermediate
DEVELOPMENT OF THE NERVOUS SYSTEM
743
mass of the ventricle is developed across the area of contact. The metathalamus
comprises the geniculate bodies which originate as slight outward bulgings of the
alar lamina. In the adult the lateral geniculate body appears as an eminence on
the lateral part of the posterior end of the thalamus, while the medial is situated
on the lateral aspect of the mid-brain. The epithalamus includes the pineal
body, the posterior commissure, and the trigonum habenula?. The i)ineal body
arises as an upward the evagination of roof-plate immediately in front of the mid-
brain; this evagination becomes solid with the exception of its proximal part,
which persists as the recessus pinealis. In lizards the pineal evagination is elongated
into a stalk, and its peripheral extremity is expanded into a vesicle, in which a
rudimentary lens and retina are formed; the stalk becomes solid and nerve fibers
make their appearance in it, so that in these animals the pineal body forms a
rudimentary eye. The posterior commissure is formed by the ingrowth of fibers
into the depression behind and below the pineal evagination, and the trigonum
habenulai is developed in front of the pineal recess.
Choroidal fissure
Khineive) >h n Ion
Lamina tenninalis
Corpus striatum
Optic recess
Chiasma
Hypophysis
Recessus infundibuli
Fia. 654. — Median sagittal section of brain of human embrj'O of three months. (From model by His.)
From the basal laminae of the diencephalon the pars mamillaris hypothalami
is developed; this comprises the corpora mamillaria and the posterior part of
the tuber cinereum. The corpora mamillaria arise as a single thickening,
which becomes divided into two by a median furrow during the third month.
The roof-plate of the diencephalon, in front of the pineal body, remains thin and
epithelial in character, and is subsequently invaginated by the choroid plexuses
of the third ventricle.
The Telencephalon. — This consists of a median portion and two lateral diver-
ticula. The median portion forms the anterior part of the cavity of the third
ventricle, and is closed below and in front by the lamina terminalis. The lateral
diverticula consist of outward pouchings of the alar laminae; the cavities represent
the lateral ventricles, and their walls become thickened to form the nervous
744
NEUROLOGY
matter of the cerebral hemisplieres. The roof-plate of the telencephalon remains
thin, and is continnous in front with the lamina terminalis and behind with the
roof-plate of the diencephalon. In the basal laminae and floor-plate the pars
optica hypothalami is developed; this comprises the anterior part of the tuber
cinereum, the infundibulum and posterior lobe of the hypophysis, and the optic
chiasma. The anterior part of the tuber cinereum is derived from the posterior
part of the floor of the telencephalon; the infundibulum and posterior lobe of the
hypophysis arise as a downward diverticulum from the floor. The most depen-
dent part of the diverticulum becomes solid and forms the posterior lobe of the
hypophysis ; the anterior lobe of the hypophysis is developed from a diverticulum
of the ectodermal lining of the stomodeum. The optic chiasma is formed
by the meeting and partial decussation of the optic nerves, which subsequently
grow backward as the optic tracts and end in the diencephalon.
The cerebral hemispheres arise as diverticula of the alar laminae of the telen-
cephalon (Figs. 650 to 654); they increase rapidly in size and ultimately overlap
the structures developed from the mid- and hind-brains. This great expansion
of the hemispheres is a char-
acteristic feature of the brains
of mammals, and attains its
maximum development in
the brain of man. Elliott-
Smith divides each cerebral
hemisphere into three funda-
mental parts, viz., the rhinen-
cephalon, the corpus striatum,
and the neopallium.
The rhinencephalon (Fig.
655) represents the oldest
part of the telencephalon,
and forms almost the whole
of the hemisphere in fishes,
amphibians, and reptiles. In
man it is feebly developed
in comparison with the rest
of the hemisphere, and com-
prises the following parts,
viz., the olfactory lobe (con-
sisting of the olfactory tract and bulb and the trigonum olf actorium) , the anterior
perforated substance, the septum pellucidum, the subcallosal, supracallosal, and
dentate gyri, the fornix, the hippocampus, and the uncus. The rhinencephalon
appears as a longitudinal elevation, with a corresponding internal furrow, on the
under surface of the hemisphere close to the lamina terminalis; it is separated
from the lateral surface of the hemisphere by a furrow, the external rhinal fissure,
and is continuous behind with that part of the hemisphere, which will ultimately
form the anterior end of the temporal lobe. The elevation becomes divided by
a groove into an anterior and a posterior part. The anterior grows forward as
a hollow stalk the lumen of which is continuous with the anterior part of the ven-
tricular cavity. During the third month the stalk becomes solid and forms the
rudiment of the olfactory bulb and tract; a strand of gelatinous tissue in the interior
of the bulb indicates the position of the original cavity. From the posterior part the
anterior perforated substance and the pyriform lobe are developed; at the begin-
ning of the fourth month the latter forms a curved elevation continuous behind
with the medial surface of the temporal lobe, and consisting, from before backward,
of the gyrus olfactorius lateralis, gyrus ambiens, and gyrus semilunaris, parts which
Gyr. olf. med.
Gyr. olf. la I.
Gyr. ambiens
Gyr. diagonalis
Gyr, semilunaris
Cerebellum
Olive
Fig. 655. — Inferior surface of brain of embryo at beginning of fourth
month, (From Kollmann.)
DEVELOPMENT OF THE NERVOUS SYSTEM
745
in the adult brain are represented by the lateral root of the olfactory tract and the
uncus. The position and connections of the remaining portions of the rhinen-
cephalon are described with the anatomy of the brain.
The corpus striatum (Figs. 651 and 653) appears in the fourth week as a triangular
thickening of the floor of the telencephalon between the optic recess and the
interventricular foramen, and continuous behind with the thalamic part of the
diencephalon. It increases in size, and by the second month is seen as a swelling
in the floor of the future lateral ventricle ; this swelling reaches as far as the posterior
end of the primitive hemisphere, and when this part of the hemisphere grows
backward and downward to form the temporal lobe, the posterior part of the corpus
striatum is carried into the roof of the inferior horn of the ventricle, where it is
seen as the tail of the caudate nucleus in the adult brain. During the fourth and
fifth months the corpus striatum becomes incompletely subdivided by the fibers of
the internal capsule into two masses, an inner, the caudate nucleus, and an outer,
the lentiform nucleus. In front, the corpus striatum is continuous with the anterior
perforated substance; laterally it is confluent for a time with that portion of the
wall of the vesicle which is developed into the insula, but this continuity is sub-
sequently interrupted by the fibers of the external capsule.
Falz cerebri
Fdgf ofuhite <ntbstance
^Edije oj (jruj cortical
subntance
Ilippucampal fissure
Cs. Corpus striatum. Th. Thalamus.
Fig. 656. — Diagrammatic coronal section of brain to show relations of neopallium. (After His.) Cs. Corpus striatum.
Th. Thalamus.
The neopallium (Fig. 656) forms the remaining, and by far the greater, part of the
cerebral hemisphere. It consists, at an early stage, of a relatively large, more or
less hemispherical cavity — the primitive lateral ventricle — enclosed by a thin wall
from which the cortex of the hemisphere is developed. The vesicle expands in all
directions, but more especially upward and backward, so that by the third month
the hemispheres cover the diencephalon, by the sixth they overlap the mid-brain,
and by the eighth the hind-brain.
The median lamina uniting the two hemispheres does not share in their expan-
sion, and thus the hemispheres are separated by a deep cleft, the forerunner of
the longitudinal fissure, and this cleft is occupied by a septum of mesodermal
tissue which constitutes the primitive falx cerebri. Coincidently with the expan-
sion of the vesicle, its cavity is drawn out into three prolongations which represent
746
NEUROLOGY
the horns of the future lateral ventricle; the hinder end of the vesicle is carried down-
ward and forward and forms the inferior horn; the posterior horn is produced
somewhat later, in association with the backward growth of the occipital lobe of
the hemisphere. The roof-plate of the primitive fore-brain remains thin and of an
epithelial character; it is invaginated into the lateral ventricle along the medial
wall of the hemisphere. This invagination constitutes the choroidal fissure, and
extends from the interventricular foramen to the posterior end of the vesicle. Meso-
dermal tissue, continuous with that of the primitive falx cerebri, and carrying
bloodvessels with it, spreads between the two layers of the invaginated fold and
forms the rudiment of the tela choroidea; the margins of the tela become highly
vascular and form the choroid plexuses which for some months almost completely
fill the ventricular cavities; the tela at the same time invaginates the epithelial
roof of the diencephalon to form the choroid plexuses of the third ventricle. By
the downward and forward growth of the posterior end of the vesicle to form the
temporal lobe the choroidal fissure finally reaches from the interventricular fora-
men to the extremitv of the inferior horn of the ventricle.
Gyrus dentaius
Tcenia thalavii
Thalamus
Choroidal fissure
Post, commissure
Corpora quadrigcmina
Cerebral aqueduct
Cerebral peduncle
Cerebellum
IV. ventricle
Corpus callosum
Septum piUucidum
Anterior commissure
Lamina terminalis
?iicephalon
Optic chiasma
Hypophysis
^\ III. ventricle
Pons
Medidla oblongata
Fig. 657. — Median sagittal section of brain of human embryo of four months. (Marchand.)
Parallel with but above and in front of the choroidal fissure the medial wall of
the cerebral vesicle becomes folded outward and gives rise to the hippocampal
fissure on the medial surface and to a corresponding elevation, the hippocampus,
within the ventricular cavity. The gray or ganglionic covering of the wall of the
vesicle ends at the inferior margin of the fissure is a thickened edge; beneath this
the marginal or reticular layer (future white substance) is exposed and its lower
thinned edge is continuous with the epithelial invagination covering the choroid
plexus (Fig. G56). As a result of the later downward and forward growth of the
temporal lobe the hippocampal fissure and the parts associated Avith it extend from
the interventricular foramen to the end of the inferior horn of the ventricle.
The thickened edge of gray substance becomes the gyrus dentatus, the fasciola
cinerea and the supra- and subcallosal gyri, while the free edge of the white sub-
stance forms the fimbria hippocampi and the body and crus of the fornix. The
corpus callosum is developed within the arch of the hippocampal fissure, and the
upper part of the fissure forms, in the adult brain, the callosal fissure on the medial
surface of the hemisphere.
The Commissures (Fig. 657). — The development of the posterior commissure
has already been referred to (page 743). The great commisssures of the hemi-
DEVELOPMENT OF THE NERVOUS SYSTEM
747
Parietal
operculum
spheres, viz., the corpus callosum, the fornix, and anterior commissures, arise from
the lamina terminalis. About the fourth month a small thickening appears in
this lamina, immediately in front of the interventricular foramen. The lo\\'er
part of this thickening is soon constricted off, and fibers appear in it to form
the anterior commissure. The upper part continues to grow with the hemispheres,
and is invaded by two sets of fibers. Transverse fibers, extending between the
hemispheres, pass into its dorsal part, which is now difi'erentiated as the corpus
callosum (in rare cases the corpus callosum is not developed). Into the ventral
part longitudinal fibers from the hippocampus pass to the lamina terminalis, and
through that structure to the corpora mamillaria; these fibers constitute the
fornix. A small portion, lying antero-inferiorly between the corpus callosum and
fornix, is not in^'aded by the commissural fibers; it remains thin, and later a
cavity, the cavity of the septum pellucidum, forms in its interior.
Fissures and Sulci. — The outer surface of the cerebral hemisphere is at first smooth,
but later it exhibits a number of elevations or convolutions, separated from each
other by fissures and sulci, most of which
make their appearance during the sixth
or seventh months of fetal life. The
term, fissure is applied to such grooves as
involve the entire thickness of the cere-
bral wall, and thus produce correspond-
ing eminences in the ventricular cavity,
while the sulci affect only the superficial
part of the wall, and therefore leave no
impressions in the ventricle. The fissures
comprise the choroidal and hippocampal
already described, and two others, \iz.,
the calcarine and collateral, which pro-
duce the swellings known respectively
as the calcar avis and the collateral
eminence in the ventricular cavit}-. Of
the sulci the following may be referred
to, viz., the central sulcus (fissure of
Rolando), which is developed in two
parts; the intraparietal sulcus in four
parts; and the cingulate sulcus in two
or three parts. The lateral cerebral or Sylvian fissure differs from all the other
fissures in its mode of development. It appears about the third month as a depres-
sion, the Sylvian fossa, on the lateral surface of the hemisphere (Fig. 658); this
fossa corresponds with the position of the corpus striatum, and its floor is moulded
to form the insula. The intimate connection which exists between the cortex
of the insula and the subjacent corpus striatum prevents this part of the hemi-
sphere wall from expanding at the same rate as the portions which surround it.
The neighboring parts of the hemisphere therefore gradually grow over and cover
in the insula, and constitute the temporal, parietal, frontal, and orbital opercula
of the adult brain. The frontal and orbital opercula are the last to form, but by the
end of the first year after birth the insula is completely submerged by the approxi-
mation of the opercula. The fissures separating the opposed margins of the oper-
cula constitute the composite lateral cerebral fissure.
If a section across the wall of the hemisphere about the sixth week be examined
microscopically it will be found to consist of a thin marginal or reticular layer, a
thick ependymal layer, and a thin intervening mantle layer. Neuroblasts from the
ependymal and mantle layers migrate into the deep part of the marginal layer and
form the cells of the cerebral cortex. The nerve fibers which form the underlying
white substance of the hemispheres consist at first of outgrowths from the cells of
Temporal operculum
Sylvian fossa
Frontal operculum.
Fig. 658. — Outer surface of cerebral hemisphere of
human embryo of about five months.
748
NEUROLOGY
the corpora striata and thalami; later the fibers from the cells of the cortex are
added. Medullation of these fibers begins about the time of birth and continues
until puberty. A summary of the parts derived from the brain vesicles is given in
the following table :
Hind-brain or
Rhombencephalon
1. Myelencephalon
2. Metencephalon
Isthmus rhomb-
encephali
Mid-brain or Mesencephalon
Fore-brain or
Prosencephalon
1. Diencephalon
2. Telencephalon
Medulla oblongata
Lower part of fourth
ventricle.
Pons
Cerebellum
Intermediate part of fourth
ventricle.
Anterior medullary velum
Brachia conjunctiva
cerebelli.
Upper part of fourth
ventricle.
Cerebral peduncles
Lamina quadrigemina
Cerebral aqueduct.
Thalamus
Metathalamus
Epithalamus
Pars mamillaris hypo-
thalami
Posterior part of third
ventricle.
Anterior part of third
ventricle
Pars optica hypo-
thalami
Cerebral hemispheres
Lateral ventricles
Interventricular foramen.
The Cranial Nerves. — With the exception of the olfactory, optic, and acoustic
nerves, which will be especially considered, the cranial nerves are developed in a
similar manner to the spinal nerves
■Boof-plate
Alar lamina
Furrow between
alar and basal
laniince
Basal lamina
Vagus nerve
Hypoglossal tierve
Floor-plate
Fia. 659. — Transverse section of medulla oblongata of
human embryo. X 32. (KoUmann )
(see page 735). The sensory or
afferent nerves are derived from
the cells of the ganglion rudiments
of the neural crest. The central
processes of these cells grow into
the brain and form the roots of the
nerves, while the peripheral pro-
cesses extend outward and consti-
tute their fibers of distribution
(Fig. 645). It has been seen, in
considering the development of the
medulla oblongata (page 739), that
the tractus solitarius (Fig. 660), de-
rived from the fibers which grow
inward from the ganglion rudiments
of the glossopharyngeal and vagus
nerves, is the homologue of the
oval bundle in the cord which had
THE MEDULLA SPINALIS OR SPINAL CORD
749
its origin in the posterior nerve roots. The motor or efferent nerves arise as out-
growtlis of the neuroblasts situated in the basal laminae of the mid- and hind-
brain. While, however, the spinal motor nerve roots arise in one series from the
basal lamina, the cranial motor nerves are grouped into two sets, according as
they spring from the medial or lateral parts of the basal lamina. To the former
set belong the oculomotor, trochlear, abducent, and hypoglossal nerves; to the
latter, the accessory and the motor fibers of the trigeminal, facial, glossopharyn-
geal, vagus nerves (Figs. 659, 660).
Rhombic lip
Tract us
solitarius
Vagus nerve
hypoglossal nerve
Floor-plate
Fig. 660. — Transverse section of medulla oblongata of human embryo. (After His.)
THE MEDULLA SPINALIS OR SPINAL CORD.
The medulla spinalis or spinal cord forms the elongated, nearly cylindrical, part
of the central nervous system which occupies the upper two-thirds of the vertebral
canal. Its average length in the male is about 45 cm., in the female from 42 to 43
cm., while its weight amounts to about 30 gms. It extends from the level of the
upper border of the atlas to that of the lower border of the first, or upper border
of the second, lumbar vertebra. Above, it is continuous with the brain; below, it
ends in a conical extremity, the conus meduUaris, from the apex of which a delicate
filament, the filum terminale, descends as far as the first segment of the coccyx
(Fig. 661).
The position of the medulla spinalis varies with the movements of the vertebral
column, its lower extremity being drawn slightly upward when the column is
flexed. It also varies at different periods of life; up to the third month of fetal
life the medulla spinalis is as long as the vertebral canal, but from this stage onward
the vertebral column elongates more rapidly than the medulla spinalis, so that by
the end of the fifth month the medulla spinalis terminates at the base of the sacrum,
and at birth about the third lumbar vertebra.
The medulla spinalis does not fill the part of the vertebral canal in which it lies;
it is ensheathed by three protective membranes, separated from each other by two
concentric spaces. The three membranes are named from without inward, the
dura mater, the arachnoid, and the pia mater. The dura mater is a strong, fibrous
membrane which forms a wide, tubular sheath; this sheath extends below the ter-
mination of the medulla spinalis and ends in a pointed cul-de-sac at the level of the
lower border of the second sacral vertebra. The dura mater is separated from the
wall of the vertebral canal by the epidural cavity, which contains a quantity of loose
areolar tissue and a plexus of veins; between the dura mater and the subjacent
arachnoid is a capillary interval, the subdural cavity, which contains a small quan-
tity of fluid, probably of the nature of lymph. The arachnoid is a thin, transparent
750
NEUROLOGY
sheath, separated from the pia mater by a comparatively wide interval, the sub-
arachnoid cavity, which is filled with cerebrospinal fluid. The pia mater closely
invests the medulla spinalis and sends delicate septa into its substance; a narrow
band, the ligamentum denticulatmn, extends along each of its lateral surfaces
and is attached by a series of pointed processes to the inner surface of the dura
mater.
Thirty-one pairs of spinal nerves spring from the medulla spinalis, each nerve
having an anterior or ventral, and a posterior or dorsal root, the latter being dis-
tinguished by the presence of an oval swelling,
the spinal ganglion, which contains numerous
nerve cells. Each root consists of several
bundles of nerve fibers, and at its attachment
extends for some distance along the side of
the medulla spinalis. The pairs of spinal
nerves are grouped as follows: cervical 8,
thoracic 12, lumbar 5, sacral 5, coccygeal 1,
and, for convenience of description, the
medulla spinalis is divided into cervical,
thoracic, lumbar and sacral regions, corre-
sponding with the attachments of the different
groups of nerves.
Although no trace of transverse segmen-
tation is visible on the surface of the medulla
spinalis, it is convenient to regard it as being
built up of a series of superimposed spinal
segments or neuromeres, each of which has
a length equivalent to the extent of attach-
ment of a pair of spinal nerves. Since the ex-
tent of attachment of the successive pairs of
nerves varies in different parts, it follows that
the spinal segments are of varying lengths;
thus, in the cervical region they average about
13 mm., in the mid-thoracic region about 26
mm., while in the lumbar and sacral regions
they diminish rapidly from about 15 mm. at
the level of the first pair of lumbar nerves to
about 4 mm. opposite the attachments of the
lower sacral nerves.
As a consequence of the relative inequality
in the rates of growth of the medulla spinalis
and vertebral column, the nerve roots, which
in the early embryo passed transversely out-
ward to reach their respective intervertebral foramina, become more and more
oblique in direction from above downward, so that the lumbar and sacral nerves
descend almost vertically to reach their points of exit. From the appearance these
nerves present at their attachment to the medulla spinalis and from their great
length they are collectively termed the cauda equina (Fig. 662).
The filum terminale is a delicate filament, about 20 cm. in length, prolonged
downward from the apex of the conus medullaris. It consists of two parts, an upper
and a lower. The upper part, or filum terminale internum, measures about 15 cm.
in length and reaches as far as the lower border of the second sacral vertebra. It
is contained within the tubular sheath of dura mater, and is surrounded by the
nerves forming the cauda equina, from which it can be readily recognized by its
bluish-white color. The lower part, or filum terminale externum, is closely invested
Fig. 661. — Sagittal section of vertebral canal
to show the lower end of the medulla spinalis
and the filum terminale. Li, Lv. First and fifth
lumbar vertebrae. Sii. Second sacral vertebra.
1. Dura mater. 2. Lower part of tube of
dura mater. 3. Lower extremity of medulla
spinalis. 4. Intradural, and 5, Extradural por-
tions of filum terminale. 6. Attachment
of filum terminale to first segment of coccyx.
(Testut.)
THE MEDULLA SPINALIS OR SPINAL CORD
751
Decussation of
the pyramids
Anterior median
fissure
by, and is adherent to, the dura mater; it extends downward from the apex of the
tubular sheath and is attached to the back of the first segment of the coccyx.
The filum terminale consists mainly of
fibrous tissue, continuous above with
that of the pia mater. Adhering to its
outer surface, however, are a few strands
of nerve fibers which probably represent
rudimentary second and third coccygeal
nerves; further, the central canal of the
medulla spinalis extends downward into
it for 5 or 6 cm.
Enlargements. — The medulla spinalis
is not quite cylindrical, being slightly
flattened from before backward; it also
Dura mater
Conus medullaris
Posterior nerveroots
Filum terminale
Postero-
■ intermediate
sulcus
Cervical
enlargement
Posterior
median sidcus
Postero-
lateral sulcus
Lumhar
enlargement
■Conus
-~- Filum - —
Fio. 662. — Cauda equina and filum terminale seen
from behind. The dura mater has been opened and
spread out, and the arachnoid has been removed.
Ventral aspect Dorsal aspect
FiQ. 663. — Diagrams of the medulla spinalis.
r52
NEUROLOGY
presents two swellings or enlargements, an upper or cervical, and a lower or lumbar
(Fig. 663).
The cervical enlargement is the more pronounced, and corresponds with the attach-
ments of the large nerves which supply the upper limbs. It extends from about
the third cervical to the second thoracic vertebra, its maximum circumference
(about 38 mm.) being on a level with the attachment of the sixth pair of cervical
nerves.
The lumbar enlargement gives attachment to the nerves which supply the lower
limbs. It commences about the level of the ninth thoracic vertebra, and reaches
its maximum circumference, of about 33 mm., opposite the last thoracic vertebra,
below which it tapers rapidly into the conus medullaris.
Fissures and Sulci (Fig. 664). — An anterior median fissure and a posterior
median sulcus incompletely divide the medulla spinalis into two symmetrical
parts, which are joined across the middle line by a commissural band of nervous
matter.
Posterior median sulcus
Posterior median septvm
Posterior
inerve roots
ostero-latcral sulcus
Posterior
column
For mat io
reticularis
Lateral
column
Anterior
column
Fig. 664.-
Anteriornerve roots Anterior median fissure
-Transverse section of the medulla spinalis in the mid-thoracic region.
The Anterior Median Fissure {fissura mediana anterior) has an average depth of
about 3 mm., but this is increased in the lower part of the medulla spinalis. It
contains a double fold of pia mater, and its floor is formed by a transverse band
of white substance, the anterior white commissure, which is perforated by blood-
vessels on their way to or from the central part of the medulla spinalis.
The Posterior Median Sulcus {sulcus medianus jMsterior) is very shallow; from it
a septum of neuroglia reaches rather more than half-way into the substance of the
medulla spinalis; this septum varies in depth from 4 to 6 mm., but diminishes
considerably in the lower part of the medulla spinalis.
On either side of the posterior median sulcus, and at a short distance from it,
the posterior nerve roots are attached along a vertical furrow named the postero-
lateral sulcus. The portion of the medulla spinalis which lies between this and the
posterior median sulcus is named the posterior funiculus. In the cervical and upper
thoracic regions this funiculus presents a longitudinal furrow, the postero-inter-
mediate sulcus ; this marks the position of a septum which extends into the posterior
funiculus and subdivides it into two fasciculi — a medial, named the fasciculus
gracilis (tract of Goll); and a lateral, the fasciculus cuneatus {tract of Burdach)
THE MEDULLA SPINALIS OR SPINAL CORD
753
(Fig. 672). The portion of the medulla spinalis which lies in front of the postero-
lateral sulcus is termed the antero-lateral region. The anterior nerve roots, unlike
the posterior, are not attached in linear series, and their position of exit is not
marked by a sulcus. They arise by separate bundles which spring from the anterior
column of gray substance and, passing forward through the white substance,
emerge over an area of some slight width. The most lateral of these bundles is
generally taken as a dividing line which separates the antero-lateral region into
two parts, viz., an anterior funiculus, between the anterior median fissure and the
most lateral of the anterior nerve roots; and a lateral funiculus, between the exit
of these roots and the postero-lateral sulcus. In the upper part of the cervical
region a series of nerve roots passes outward through the lateral funiculus of the
medulla spinalis; these unite to form the spinal portion of the accessory nerve,
which runs upward and enters the cranial cavity through the foramen magnum.
White matter.
lOO
»0
60
40
L'O
100
Gray motter.
tire section.
I U m \Y V VI Ml Mil I II lU IV
VII \1ll
Xl .Ml I li 111 l>- V I U lUIWJ
Fig. 665. — Curves showing the sectional area at different levels of the cord. The ordinates show the area in sq. mm.
(Donaldson and Davis.)
The Internal Structure of the Medulla Spinalis. — On examining a transverse
section of the medulla spinalis (Fig. 664) it is seen to consist of gray and white
nervous substance, the former being enclosed within the latter.
Gray Substance {substantia grisca centralis). — ^The gray substance consists of
two symmetrical portions, one in each half of the medulla spinalis: these are
joined across the middle line by a.transverse commissure of gray substance, through
which runs a minute canal, the central canal, just visible to the naked eye. In a
transverse section each half of the gray substance is shaped like a comma or
crescent, the concavity of which is directed laterally; and these, together with
the intervening gray commissure, present the appearance of the letter H. An
imaginary coronal plane through the central canal serves to divide each crescent
into an anterior or ventral, and a posterior or dorsal column.
The Anterior Column {columna anterior; anterior cornu), directed forward, is
broad and of a rounded or quadrangular shape. Its posterior part is termed the
base, and its anterior part the head, but these are not differentiated from each other
by any well-defined constriction. It is separated from'the surface of the medulla
spinalis by a layer of white substance which is traversed by the bundles of the
. anterior nerve roots. In the thoracic region, the postero-lateral part of the anterior
column projects lateralward as a triangular field, which is named the lateral column
{columna lateralis; lateral cornu).
The Posterior Column {columna posterior; posterior cornu) is long and slender,
and is directed backward and lateralward : it reaches almost as far as the postero-
lateral sulcus, from which it is separated by a thin layer of white substance, the
tract of Lissauer. It consists of a base, directly continuous with the base of the
anterior horn, and a neck or slightly constricted portion, which is succeeded by
an oval or fusiform area, termed the head, of which the apex approaches the postero-
lateral sulcus. The apex is capped by a V-shaped or crescentic mass of trans-
lucent, gelatinous neuroglia, termed the substantia gelatinosa of Rolando, which
48
754
NEUROLOGY
C2,
C5,
contains both neuroglia cells, and small nerve cells. Between the anterior and
posterior columns the gray substance extends as a series of processes into the
lateral funiculus, to form a net-work called the for-
matio reticularis.
The quantity of gray substance, as well as the form
C./. which it presents on transverse section, varies mark-
edly at different levels. In the thoracic region it is
small, not only in amount but relatively to the sur-
rounding white substance. In the cervical and lum-
bar enlargements it is greatly increased : in the latter,
and especially in the conus medullaris, its proportion
to the white substance is greatest (Fig. 065). In
the cervical region its posterior column is compara-
tively narrow, while its anterior is broad and ex-
panded; in the thoracic region, both columns are
attenuated, and the lateral column is evident; in
the lumbar enlargement, both are expanded; while
in the conus medullaris the gray substance assumes
the form of two oval masses, one in each half of the
cord, connected together by a broad gray commissure.
The Central Canal (ccmalis centralis) runs through-
out the entire length of the medulla spinalis. The
C.8, portion of gray substance in front of the canal is
named the anterior gray commissure; that behind it,
the posterior gray commissure. The former is thin,
and is in contact anteriorly with the anterior white
commissure: it contains a couple of longitudinal
veins, one on either side of the middle line. The
posterior gray commissure reaches from the central
canal to the posterior median septum, and is thin-
. nest in the thoracic region, and thickest in the conus
medullaris. The central canal is continued upward
Th.8. through the lower part of the medulla oblongata, and
opens into the fourth ventricle of the brain; below,
it reaches for a short distance into the filum termi-
nale. In the lower part of the conus medullaris it
^fjJ2 exhibits a fusiform dilatation, the terminal ventricle;
this has a vertical measurement of from 8 to 10
mm., is triangular on cross-section with its base
directed forward, and tends to undergo obliteration
after the age of forty years.
Throughout the cervical and thoracic regions the
central canal is situated in the anterior third of the
medulla spinalis; in the lumbar enlargement it is
near the middle, and in the conus medullaris it
approaches the posterior surface. It is filled with
cerebrospinal fluid, and lined by ciliated, columnar
epithelium, outside of which is an encircling band
of gelatinous substance, the substantia gelatinosa
centralis. This gelatinous substance consists mainly
of neuroglia, but contains a few nerve cells and
fibers; it is traversed by processes from the deep ends
of the columnar ciliated cells which line the central
canal (Fig. 007).
ThZ
L.3.
S.2.
Coc
Fio. 666. — Transverse sections of the
medulla spinalis at different levels.
THE MEDULLA SPINALIS OR SPINAL CORD
755
Neuroglial cells
Ependymal cells
Fig. 667. — Section of central canal of medulla
spinalis, showing ependymal and neuroglial cells.
(v. Lenhossek.)
Structure of the Gray Substance. — The gray substance consists of numerous nerve
cells and nerve fibers held together by neuroglia. Throughout the greater part
of the gray substance the neuroglia presents the appearance of a sponge-like net-
work, but around the central canal and on the apices of the posterior columns
it consists of the gelatinous substance already referred to. The nerve cells are
multipolar, and vary greatly in size and shape. They consist of (1) motor cells of
large size, which are situated in the anterfor horn, and are especially numerous in
the cervical and lumbar enlargements; the axons of most of these cells pass out to
form the anterior nerve roots, but before leaving the w^hite substance they fre-
quently give off collaterals, which reenter and ramify in the gray substance.^ (2)
Cells of small or medium size, whose
axons pass into the white matter,
where some pursue an ascending,
and others a descending course, but
most of them divide in a T-shape
manner into descending and ascend-
ing processes. They give ofT col-
laterals which enter and ramify in
the gray substance, and the termi-
nations of the axons behave in a
similar manner. The lengths of
these axons vary greatly: some
are short and pass only between
adjoining spinal segments, while
others are longer and connect more
\^A
— Collateral
— AsceTiding
~ Descending
\~ Arborisation
Fig. 668. — Cells of medulla spinalis. Diagram showing
in longitudinal section the intersegmental neurons of the
medulla spinalis. The gray and white parts correspond
respectively to the gray and white substance of the medulla
spinalis. (Poirier.)
distant segments. These cells and their processes constitute a series of association
or intersegmental neurons (Fig. 668), which link together the different parts of
the medulla spinalis. The axons of most of these cells are confined to that side
of the medulla spinalis in which the nerve cells are situated, but some cross to the
opposite side through the anterior commissure, and are termed crossed commissural
fibers. Some of these latter end directly in the gray substance, while others enter
the white substance, and ascend or descend in it for varying distances, before finally
terminating in the gray substance. (3) Cells of the ty^e II of Golgi, limited for the
' Lenhossek and Cajal found that in the chick embryo the axons of a few of these nerve cells passed backward through
the posterior column, and emerged as the motor fibers of the voslerior nerce roots. These fabers are said to control the
peristaltic movements of the intestine. Their presence, in man, has not yet been determined.
756
NEUROLOGY
most part to the posterior column, are found also in the substantia gelatinosa of
Rolando; their axons are short and entirely confined to the gray substance, in which
Fasciculus cuneatus^__J_|
Ventral
'spinocerebellar
fasciculus
Posterior
spinothalamic
fasciculus
Spinotectal
fasciculus
Ventral
spinothalamic
fasciculus
Fig. 669. — Diagram showing a few of the connections of afferent (sensory) fibers of the posterior root with the efferent
fibers from the ventral column and with the various long ascending fasciculi.
they break up into numerous fine filaments. ]\Iost of the nerve cells are arranged in
longitudinal columns, and appear as groups on transverse section (Figs. 669, 670, 671).
-Lateral cerebrospinal
fasciculus
-Rubrospinal fasciculus
-Tectospinal fasciculus
C Vestibulospinal fasciculus
Fig. 670. — Diagram showing possible connection of long descending fibers from higher centers with the motor
cells of the ventral column through association fibers.
Nerve Cells in the Anterior Column. — The nerve cells in the anterior column are
arranged in columns of varying length. The longest occupies the medial part of
the anterior column, and is named the antero-medial column: it is well marked in
C4, Co, again from C 8 to L 4, it disappears in L5 and SI but is Avell marked in
THE MEDULLA SPINALIS OR SPINAL CORD
757
S2, S3 and S4 (Bruce). ^ Behind it
is not represented in L5, Si, S2 nor
dorsal rami of the spinal nerves to
cohimn. In the cervical and lumbar
enlargements, where the anterior
column is expanded in a lateral direc-
tion, the following additional col-
umns are present, viz.: (a) antero-
lateral, which consists of two groups,
one in C4, C5, CO the other in C6,
C 7, C 8 in the cervical enlargement
and of a group from L2 to S2 in
the lumbo-sacral enlargement; (b)
postero-lateral, in the lower five cer-
vical, lower four lumbar, and upper
three sacral segments ; (c) post-postero-
lateral, in the last cervical, first tho-
racic, and upper three sacral seg-
ments; and (f/) a central, in the lower
four lumbar and upper two sacral
segments. These cell groups are evi-
dently related to the nerve roots of
the brachial and sacral plexuses and
supply fibers to the muscles of the
arm and leg. Throughout the base
of the anterior column are scattered
solitary cells, the axons of some of
which form crossed commissural
fibers, while others constitute the
motor fibers of the posterior nerve
roots. (See footnote, page 755.)
Nerve Cells in the Lateral Column.
—These form a column which is
best marked where the lateral gray
column is dift'erentiated, viz., in the
thoracic region ;2 but it can be traced
throughout the entire length of the
medulla spinalis in the form of
groups of small cells which are situ-
ated in the anterior part of the
formatio reticularis. In the upper
part of the cervical region and lower
part of the medulla oblongata as
well as in the third and fourth sac-
ral segments this column is again
differentiated. In the medulla it is
kno^^^l as the lateral nucleus. The
cells of this column are fusiform or
star-shaped, and of a medium size:
the axons of some of them pass into
' Topographical Atlas of the Spinal Cord, 1901.
2 According to Bruce and Pirie (B. M. J., Novem-
ber 17, 1906) this column extends from the middle
of the eighth cervical segment to the lower part of
the second lumbar or the upper part of the third
lumbar segment.
is a dorso-medial column of small cells, which
below S4. Its axons probably pass into the
supply the dorsal musculature of the spinal
Lateral
column:
Postero-
lateral
column
Antero-lateral
column
C. VII
Dorso-medial
column
Antero-medial
column
Dorsal nucleu.
Lateral colUmii-
TH. VI
Anterior column'
Postero-
lateral
column
Antero-late
column
L. I
Antero-medial
column
S.I
Postero-lateral
Column
Central
column
Fig. 671. — -Transverse sections of the medulla spinalis at
different levels to show the arrangement of the principal cell
columns.
758 NEUROLOGY
the anterior nerve roots, by which they are carried to the sympathetic nerves:
they constitute the white rami and are sympathetic or visceral efferent fibers; they
are also known as preganglionic fibers of the sympathetic system; the axons of others
pass into the anterior and lateral funiculi, where they become longitudinal.
Nerve Cells in the Posterior Column.— 1. The dorsal nucleus (micleiis dorsaUs; col-
umn of Clarke) occupies the medial part of the base of the posterior column, and
appears on the transverse section as a well-defined oval area. It begins below
at the level of the second or third lumbar nerve, and reaches its maximum size
opposite the twelfth thoracic nerve. Above the level of the ninth thoracic nerve
its size diminishes, and the column ends opposite the last cervical or first thoracic
nerve. It is represented, however, in the other regions by scattered cells, which
become aggregated to form a cervical nucleus opposite the third cervical nerve,
and a sacral nucleus in the middle and lower part of the sacral region. Its cells
are of medium size, and of an oval or pyriform shape; their axons pass into the
peripheral part of the lateral funiculus of the same side, and there ascend, prob-
ably in dorsal spinocerebellar (direct cerebellar) fasciculus. 2. The nerve cells in the
substantia gelatinosa of Rolando are arranged in three zones: a posterior or margi-
nal, of large angular or fusiform cells; an intermediate, of small fusiform cells; and
an anterior, of star-shaped cells. The axons of these cells pass into the lateral
and posterior funiculi, and there assume a vertical course. In the anterior zone
some Golgi cells are found whose short axons ramify in the gray substance. 3.
Solitary cells of varying form and size are scattered throughout the posterior
column. Some of these are grouped to form the posterior basal column in the base
of the posterior column, lateral to the dorsal nucleus; the posterior basal column
is well-marked in the gorilla (Waldeyer), but is ill-defined in man. The axons of
its cells pass partly to the posterior and lateral funiculi of the same side, and
partly through the anterior white commissure to the lateral funiculus of the
opposite side. Golgi cells, type II, located in this region send axons to the lateral
and ventral columns.
A few star-shaped or fusiform nerve cells of varying size are found in the sub-
stantia gelatinosa centralis. Their axons pass into the lateral funiculus of the
same, or of the opposite side.
The nerve fibers in the gray substance form a dense interlacement of minute
fibrils among the nerve cells. This interlacement is formed partly of axons which
pass from the cells in the gray substance to enter the white funiculi or nerve roots;
partly of the axons of Golgi's cells which ramify only in the gray substance; and
partly of collaterals from the nerve fibers in the white funiculi which, as already
stated, enter the gray substance and ramify within it. ^
White Substance {suhstaniia alba). — The white substance of the medulla spinalis
consists of medullated nerve fibers imbedded in a spongelike net-work of neuroglia,
and is arranged in three funiculi: anterior, lateral, and posterior. The anterior
funiculus lies between the anterior median fissure and the most lateral of the ante-
rior nerve roots: the lateral funiculus between these nerve roots and the postero-
lateral sulcus; and the posterior funiculus between the postero-lateral and the pos-
terior median sulci (Fig. 672). The fibers vary greatly in thickness, the smallest
being found in the fasciculus gracilis, the tract of Dssauer, and inner part of the
lateral funiculus; while the largest are situated in the anterior funiculus, and in the
peripheral part of the lateral funiculus. Some of the nerve fibers assume a more
or less transverse direction, as for example those which cross from side to side
in the anterior white commissure, but the majority pursue a longitudinal course
and are divisible into (1) those connecting the medulla spinalis with the brain and
conveying impulses to or from the latter, and (2) those which are confined to the
medulla spinalis and link together its different segments, i. e., intersegmental or
association fibers.
THE MEDULLA SPINALIS OR SPINAL CORD
759
Nerve Fasciculi.— -The longitudinal fibers are grouped into more or less definite
bundles or fasciculi. These are not recognizable from each other in the normal
state, and their existence has been determined by the following methods: (1)
A. Waller discovered that if a bundle of nerve fibers be cut, the portions of the
fibers which are separated from their cells rapidly degenerate and become atrophied,
while the cells and the parts of the fibers connected with them undergo little alter-
ation.^ This is known as Wallerian degeneration. Similarly, if a group of nerve
cells be destroyed, the fibers arising from them undergo degeneration. Thus,
if the motor cells of the cerebral cortex be destroyed, or if the fibers arising from
these cells be severed, a descending degeneration from the seat of injury takes
place in the fibers. In the same manner, if a spinal ganglion be destroyed, or the
fibers which pass from it into the medulla spinalis be cut, an ascending degenera-
tion will extenfl along these fibers. (2) Pathological changes, especially in man,
have gi^•en important information by causing ascending and descending degenera-
Fasciculus gracilis
(Goll.y
Fasciculus cuneatus_
(Burdach)
Lateral proper
fasciculus
Dorsal
spinocerebellar . 1,
fasciculus
(Flechsig)
Veniro
spinocerebellar
fasciculus
(Gowers)
Posterior ^,
spinothalamic
fasciculus
Spinotectal
fasciculus
Septomarginal fasciculus
I pomma fasciculus
Posterior proper fasciculus
^Lissauer^s fasciculus
Lateral cerebrospinal
fasciculus
Rubrospinal
fasciculus
(Monakow)
Tectospinal ,
fasciculus
Anterior spinothalamic
fasciculus
Vestibulospinal
' fasciculus
Anterior cerebrospinal fasciculus
\ Sulcomarginal fasciculus
^Anterior proper fasciculus
Fig. 672. — Diagram of the principal fasciculi of the spinal cord.
tions. (3) By tracing the development of the nervous system, it has been observed
that at first the nerve fibers are merely naked axis-cylinders, and that they do not
all acquire their medullary sheaths at the same time; hence the fibers can be grouped
into different bundles according to the dates at which they receive their medullary
sheaths. (4) Various methods of staining nervous tissue are of great value in
tracing the course and mode of termination of the axis-cylinder processes.
Fasciculi in the Anterior Funiculus. — Descending Fasciculi. — The anterior cerebro-
spinal (fascicvivs cerehrospinaHs anterior; direct pyramidal tract), which is usually
small, but varies inversely in size with the lateral cerebrospinal fasciculus. It
lies close to the anterior median fissure, and is present only in the upper part
of the medulla spinalis; gradually diminishing in size as it descends, it ends about
the middle of the thoracic region. It consists of descending fibers which arise
1 Somewhat later a change, termed chromatoiysis, takes place in the nerve cells, and consists of a breaking down and
an ultimate disappearance of the Nissl bodies. Further, the body of the cell is swollen, the nucleus displaced toward
the periphery, and the part of the axon still attached to the altered cell is diminished in size and somewhat atrophied.
Under favorable conditions the cell is capable of reassuming its normal appearance, and its axon jnay grow again.
760 NEUROLOGY
from cells in the motor area of the cerebral hemisphere of the same side, and
which, as they run downward in the medulla spinalis, cross in succession through
the anterior white commissure to the opposite side, where they end, either directly
or indirectly, by arborizing around the motor cells in the anterior column. A few
of its fibers are said to pass to the lateral column of the same side and to the
gray matter at the base of the posterior column. They conduct voluntary motor
impulses from the precentral gyrus to the motor centers of the cord.
The vestibulospinal fasciculus, situated chiefly in the marginal part of the funiculus
and mainly derived from the cells of Deiters' nucleus, of the same and the opposite
side, i. e., the chief terminal nucleus of the vestibular nerve. Fibers are also
contributed to this fasciculus from scattered cells of the articular formation of the
medulla oblongata, the pons and the mid-brain (tegmentum). The other terminal
nuclei of the vestibular nerve also contribute fibers. In the brain stem these fibers
form part of the median longitudinal bundle. The fasciculus can be traced to the
sacral region. Its terminals and collaterals end either directly or indirectly among
the motor cells of the anterior column. This fasciculus is probably concerned with
equilibratory reflexes.
The tectospinal fasciculus, situated partly in the anterior and partly in the lateral
funiculus, is mainly derived from the opposite superior colliculus of the mid-brain.
The fibers from the superior colliculus cross the median raphe in the fountain
decussation of Me^Tiert and descend as the ventral longitudinal bundle in the
reticular formation of the brain-stem. Its collaterals and terminals end either
directly or indirectly among the motor cells of the anterior column of the same side.
Since the superior colliculus is an important visual reflex center, the tectospinal
fasciculus is probably concerned with visual reflexes.
Ascending Fasciculi. — The ventral spinothalamic fasciculus, situated in the
marginal part of the funiculus and intermingled more or less with the vestibulo-
spmal fasciculus, is derived from cells in the posterior column or intermediate gray
matter of the opposite side. Their axons cross in the anterior commissure. This
is a somewhat doubtful fasciculus and its fibers are supposed to end in the thalamus
and to conduct certain of the touch impulses.
The remaining fibers of the anterior funiculus constitute what is termed the
anterior proper fasciculus (fasciculus anterior proprius; anterior basis bundle). It
consists of (a) longitudinal intersegmental fibers which arise from cells in the gray
substance, more especially from those of the medial group of the anterior column,
and, after a longer or shorter course, reenter the gray substance; (6) fibers which
cross in the anterior white commissure from the gray substance of the opposite
side.
Fasciculi in the Lateral Funiculus. — 1. Descending Fasciculi. — (a) The lateral
cerebrospinal fasciculus (Jasciculus cerebrospinalis lateralis; crossed pyramidal
tract) extends throughout the entire length of the medulla spinalis, and on trans-
verse section appears as an oval area in front of the posterior column and medial
to the cerebellospinal. Its fibers arise from cells in the motor area of the cerebral
hemisphere of the opposite side. They pass downward in company with those
of the anterior cerebrospinal fasciculus through the same side of the brain as that
from which they originate, but they cross to the opposite side in the medulla oblon-
gata and descend in the lateral funiculus of the medulla spinalis.
It is probable^ that the fibers of the anterior and lateral cerebrospinal fasciculi
are not related in this direct manner with the cells of the anterior column, but ter-
minate by arborizing around the cells at the base of the posterior column and the
cells of Clarke's column, which in turn link them to the motor cells in the anterior
column, usually of several segments of the cord. In consequence of these interposed
1 Schafer, Proc. Physiolog. Soc, 1899.
THE MEDULLA SPINALIS OR SPINAL CORD 761
neurons the fibers of the cerebrospinal fascicuH correspond not to individual muscles,
but to associated groups of muscles.
The anterior and lateral cerebrospinal fasciculi constitute the motor fasciculi
of the medulla spinalis and have their origins in the motor cells of the cerebral
cortex. They descend through the internal capsule of the cerebrum, traverse the
cerebral peduncles and pons and enter the pyramid of the medulla oblongata.
In the lower part of the latter about two-thirds of them cross the middle line and
run downward in the lateral funiculus as the lateral cerebrospinal fasciculus, while
the remaining fibers do not cross the middle line, but are continued into the same
side of the medulla spinalis, where they form the anterior cerebrospinal fasciculus.
The fibers of the latter, however, cross the middle line in the anterior white com-
missure, and thus all the motor fibers from one side of the brain ultimately reach
the opposite side of the medulla spinalis. The proportion of fibers which cross
in the medulla oblongata is not a constant one, and thus the anterior and lateral
cerebrospinal fasciculi vary inversely in size. Sometimes the former is absent,
and in such cases it may be presumed that the decussation of the motor fibers in
the medulla oblongata has been complete. The fibers of these tw^o fasciculi do
not acquire their medullary sheaths until after birth. In some animals the motor
fibers are situated in the posterior funiculus.
(b) The rubrospinal fasciculus (Monakow) (prepyramidal tract), lies on the ventral
aspect of the lateral cerebrospinal fasciculus and on transverse section appears
as a somewhat triangular area. Its fibers descend from the mid-brain, where they
have their origin in the red nucleus of the tegmentum of the opposite side. Its
terminals and collaterals end either directly or indirectly in relation with the motor
cells of the anterior column. The rubrospinal fasciculus is supposed to be concerned
with cerebellar reflexes since fibers which pass from the cerebellum through the
superior peduncle send many collaterals and terminals to the red nucleus.
(c) The olivospinal fasciculus (Helweg) arises in the vicinity of the inferior
olivary nucleus in the medulla oblongata, and is seen only in the cervical region
of the medulla spinalis, where it forms a small triangular area at the periphery,
close to the most lateral of the anterior nerve roots. Its exact origin and its mode
of ending have not yet been definitely made out.
2. Ascendmg Fasciculi. — (a) The dorsal spinocerebellar fasciculus {fascicuJvs
cereheUospinalis; direct cerebellar tract of Flechsig) is situated at the periphery of the
posterior part of the lateral funiculus, and on transverse section appears as a
flattened band reaching as far forward as a line drawn transversely through the
central canal. JMedially, it is in contact with the lateral cerebrospinal fasciculus,
behind, with the fasciculus of Lissauer. It begins about the level of the second or
third lumbar nerve, and increasing in size as it ascends, passes to the vermis of the
cerebellum through the inferior peduncle. Its fibers are generally regarded as
being formed by the axons of the cells of the dorsal nucleus (Clarke s column) ; they
receive their medullary sheaths about the sixth or seventh month of fetal life. Its
fibers are supposed to conduct impulses of unconscious muscle sense.
The superficial antero-lateral fasciculus (tract of Gowers) consists of four fasciculi,
the ventral spinocerebellar, the lateral spinothalamic, the spinotectal and the
ventral spinothalamic.
(b) The ventral spinocerebellar fasciculus (Gowers) skirts the periphery of the
lateral funiculus in front of the dorsal spinocerebellar fasciculus. In transverse
section it is shaped somewhat like a comma, the expanded end of which lies in front
of the dorsal spinocerebellar fasciculus while the tail reaches forward into the
anterior funiculus. Its fibers come from the same but mostly from the opposite
side of the medulla spinalis and cross both in the anterior white commissure and
in the gray commissure; they are probably derived from the cells of the dorsal
nucleus and from other cells of tlie posterior column and the intermediate portion
762 NEUROLOGY
of the gray matter. The ventral spinocerebellar fasciculus begins about the level
of the tliird pair of lumbar nerves, and can be followed into the medulla oblongata,
and pons almost to the level of the inferior colliculus where it crosses over the
superior peduncle and then passes backward along its medial border to reach the
vermis of the cerebellum. In the pons it lies along the lateral edge of the lateral
lemniscus. Some of its fibers join the dorsal spinocerebellar fasciculus at the level
of the inferior peduncle and pass with them into the cerebellum. Other fibers are
said to continue upward in the dorso-lateral part of the tegmentum of the mid-brain
probably as far as the thalamus.
(e) The lateral spinothalamic fasciculus is supposed to come from cells in the dorsal
column and the intermediate gray matter whose axons cross in the anterior com-
missure to the opposite lateral funiculus where they pass upward on the medial
side of the ventral spinocerebellar fasciculus; on reaching the medulla oblongata
they continue in the formatio reticularis near the median fillet and probably ter-
minate in the ventro-lateral region of the thalamus. It is supposed to conduct
impulses of pain and temperature. The lateral and ventral spinothalamic fasciculi
are sometimes termed the secondary sensory fasciculus or spinal lemniscus.
(d) The spinotectal fasciculus is supposed to arise in the dorsal column and
terminate in the (inferior ?) and superior colliculi. It is situated ventral to the
lateral spinothalamic fasciculus, but its fibers are more or less intermingled with it.
It is also knowTi as the spino-quadrigeminal system of Mott. In the brain-stem tlie
fibers run lateral from the inferior olive, ventro-lateral from the superior olive, then
ventro-medial from the spinal tract of the trigeminal; the fibers come to lie in the
medial portion of the lateral lemniscus.
(e) The fasciculus of Lissauer is a small strand situated in relation to the tip
of the posterior column close to the entrance of the posterior nerve roots. It
consists of fine fibers which do not receive their medullary sheaths until toward
the close of fetal life. It is usually regarded as being formed by some of the fibers
of the posterior nerve roots, which ascend for a short distance in the tract and then
enter the posterior column, but since its fibers are myelinated later than those of
the posterior nerve roots, and do not undergo degeneration in locomotor ataxia,
they are probably intersegmental in character.
In addition the fasciculus or tract of Lissauer contains great numbers of fine
non-meduUated fibers flerived mostly from the dorsal roots but partly endogenous
in origin. These fibers are intimately related to the substantia gelatinosa which is
probably the terminal nucleus. The non-medullated fibers ascend or descend for
short distances not exceeding one or two segments, but most of them enter the
substantia gelatinosa at or near the level of their origin. Ransom^ suggests that
these non-medullated fibers and the substantia gelatinosa are concerned with the
reflexes associated with pain impulses.
(/) The lateral proper fasciculus (fasciculus lateralis proprius; lateral basis bundle)
constitutes the remainder of the lateral column, and is continuous in front with the
anterior proper fasciculus. It consists chiefly of intersegmental fibers which arise
from cells in the gray substance, and, after a longer or shorter course, reenter the
gray substance and ramify in it. Some of its fibers are, however, continued upward
into the brain under the name of the medial longitudinal fasciculus.
Fasciculi in the Posterior Funiculus. — This funiculus comprises two main fasciculi,
viz., the fasciculus gracilis, and the fasciculus cuneatus. These are separated from
each other in the cervical and upper thoracic regions by the postero-intermediate
septum, and consist mainly of ascending fibers derived from the posterior nerve roots.
The fasciculus gracilis (tract of Goll) is wedge-shaped on transverse section, and
lies next the posterior median septum, its base being at the surface of the medulla
1 Ransom, Am. Jour. Anat., 1914; Brain, 1915.
THE MEDULLA SPINALIS OR SPINAL CORD
763
spinalis, and its apex directed toward the posterior gray commissure. It increases
in size from below upward, and consists of long thin fibers which are derived from
the posterior nerve roots, and ascend as far as the medulla oblongata, where they
end in the nucleus gracilis.
The fasciculus cuneatus (tract of Burdach) is triangular on transverse section,
and lies between the fasciculus gracilis and the posterior column, its base corre-
sponding with the surface of the medulla spinalis. Its fibers, larger than those of
\
ft
V
7k„
\
A
\
Descending comma fasciculus
First
thoracic
nerve
Posterior
column
Dorsal peripheral hand
Posterior
column
Oval area of Flechsig.
Lumbar
nerves
Sacral
nerves
Posterior
column
Triangular fasciculus
Fig. 673. — Formation of the fasciculus gracilis. Medulla
spinalis \-iewed from behind. To the left, the fasciculus
gracilis is shaded. To the right, the drawing shows that
the fasciculus gracilis is formed by the long fibers of the
posterior roots, and that in this tract the sacral nerves
he next the median plane, the lumbar to their lateral
side, and the thoracic still more laterally. (Poirier.)
Posterior
column
Fig. 674. — Descending fibers in the posterior
funiculi, shown at different levels. A. In the conus
meduUaris. B. In the lumbar region. C. In the
lower thoracic region. D. In the upper thoracic
region. (After Testut.)
the fasciculus gracilis, are mostly derived from the same source, viz., the posterior
nerve roots. Some ascend for only a short distance in the tract, and, entering
the gray matter, come into close relationship with the cells of the dorsal nucleus;
while others can be traced as far as the medulla oblongata, where they end in the
gracile and cuneate nuclei.
The fasciculus gracilis and fasciculus cuneatus conduct (1) impulses of conscious
muscle sense, neurons of the second order from the nucleus gracilis and nucleus
cuneatus, pass in the median lemniscus to the thalamus and neurons of the third
764
NEUROLOGY
order from the thalamus to the cerebral cortex; (2) impulses of unconscious muscle
sense, via neurons of the second order from the nucleus gracilis and nucleus cuneatus
pass in the internal and external arcuate fibers of the medulla oblongata to the
inferior peduncle and through it to the cerebellum ; (3) impulses of tactile discrimina-
tion, via neurons of the second orcler from the nucleus cuneatus and nucleus gracilis
pass in the median lemniscus to the thalamus, neurons of the third order pass from
the thalamus to the cortex.
The Posterior Proper Fasciculus (posterior ground bundle: posierior basis bundle)
arises from cells in the posterior column; their axons bifurcate into ascending and
descending branches which occupy the ventral part of the funiculus close to the
gray column. They are intersegmental and run for varying distances sending off
collaterals and terminals to tlie gray matter.
Some descending fibers occupy different parts at different levels. In the cer-
vical and upper thoracic regions they appear as a comma-shaped fasciculus in
the lateral part of the fasciculus cuneatus, the blunt end of the comma being
directed toward the posterior gray commissure; in the lower thoracic region they
form a dorsal peripheral band on the posterior surface of the funiculus; in the lumbar
region, they are situated by the side of the posterior median septum, and appear
on section as a semi-elliptical bundle, which, together with the corresponding
bundle of the opposite side, forms the oval area of Flechsig; while in the conus
medullaris they assume the form of a triangular strand in the postero-medial part
of the fasciculus gracilis. These descending fibers are mainly intersegmental
in character and derived from cells in the posterior column, but some consist
of the descending branches of the posterior nerve roots. The comma-shaped
fasciculus was supposed to belong to the second category, but against this view
is the fact that it does not undergo descending degeneration when the posterior
nerve roots are destroyed.
Roots of the Spinal Nerves. — As already stated, each spinal nerve possesses
two roots, an anterior and a posterior, which are attached to the surface of the
medulla spinalis opposite the
Lateral column corresponding column of gray
substance (Fig. 675) ; their fibers
become medullated about the
fifth month of fetal life.
The Anterior Nerve Root [radix
anterior) consists of efferent fibers,
which are the axons of the nerve
cells in tlie \'entral part of the
anterior and lateral columns. A
short distance from their origins.
these axons are invested by medul-
lary sheaths and, passing forward,
emerge in two or three irregular
rows over an area which meas-
ures about 3 mm. in width.
The Posterior Root (r-adix pos-
terior) comprises some six or eight
fasciculi, attached in linear series
along the postero-lateral sulcus.
It consists of afferent fibers which
arise from the nerve cells in a spinal ganglion. Each ganglion cell gives oft' a single
fiber which divides in a T-shaped manner into two processes, medial and lateral.
The lateral processes extend to the sensory end-organs of the skin, muscles, tendons,
joints, etc. (somatic receptors), and to the sensory end-organs of the viscera [cisceral
Ant. med. fissure
Anterior column''
Anterior root-
Posterior
column
Posterior
root
Spinal
ganglion
Spinal
nerve
- Posterior
division
Fig. 675. — A spinal nerve with its anterior and posterior roots.
THE MEDULLA SPINALIS OR SPINAL CORD
765
receptors). The medial processes of the ganghon cells grow into the medulla spinalis
as the posterior roots of the spinal nerves.
The posterior nerve root enters the medulla spinalis in three chief bundles,
medial, intermediate, and lateral. The medial strand passes directly into the fas-
ciculus cuneatus : it consists of coarse fibers, which acquire their medullary sheaths
about the fifth month of intrauterine life; the intermediate strand consists of coarse
fibers, which enter the gelatinous substance of Rolando; the lateral is composed
of fine fibers, which assume a longitudinal direction in the tract of Lissauer, and
do not acquire their medullary sheaths until after birth. In addition to these
medullated fibers there are great numbers of non-medullated fibers wl)ich enter
witli the lateral bundle. They are more nimierous than the myelinated fibers.
They arise from the small cells of the spinal ganglia by T-shaped axons similar
to the myelinated. They are distributed Avith the peripheral nerves chiefly to the
skin, only a few are found in the nerves to the muscles.^
Having entered the medulla spinalis, all the fibers of the posterior nerve roots
divide into ascending and descending branches, and these in their turn give off
collaterals which enter the gray
substance (Fig. 676). The de-
scending fibers are short, and
soon enter the gray substance.
The ascending fibers are grouped
into long, short, and intermedi-
ate: the long fibers ascend in
the fasciculus cuneatus and fas-
ciculus gracilis as far as the me-
dulla oblongata, where they end
by arborizing around the cells of
the cuneate and gracile nuclei;
the short fibers run upward for
a distance of only 5 or 6 mm.
and enter the gray substance;
while the intermediate fibers,-
after a somewhat longer course,
have a similar destination. All
fibers entering the gray sub-
stance end by arborizing around
its nerve cells or the dendrites
of cells, those of intermediate
length being especially associated
with the cells of the dorsal nu-
cleus.
The long fibers of the posterior nerve roots pursue an oblique course upward, being
situated at first in the lateral part of the fasciculus cuneatus: higher up, they occupy
the middle of this fasciculus, having been displaced by the accession of other
entering fibers; while still higher, they ascend in the fasciculus gracilis. The upper
cervical fibers do not reach this fasciculus, but are entirely confined to the fascic-
ulus cuneatus. The localization of these fibers is very precise: the sacral nerves
he in the medial part of the fasciculus gracilis and near its periphery, the lumbar
nerves lateral to them, the thoracic nerves still more laterally; while the cervical
nerves are confined to the fasciculus cuneatus (Fig. 673).
Fig. 676. — Posterior roots entering medulla spinalis and dividing
into ascending and descending branches. (Van Gehuchten.) o.
Stem fiber, b, b. Ascending and descending limbs of bifurcation .
c. Collateral arising from stem fiber.
1 Ransom, Brain, 191.5, 38.
766
NEUROLOGY
THE ENCEPHALON OR BRAIN.
General Considerations and Divisions. — -The brain, is contained within the
cranium, and constitutes the upper, greatly expanded part of the central nervous
system. In its early embryonic
condition it consists of three hollow
vesicles, termed the hind-brain or
rhombencephalon, the mid-brain or
mesencephalon, and the fore-brain
or prosencephalon; and the parts
derived from each of these can
be recognized in the adult (Fig.
677). Thus in the process of de-
velopment the wall of the hind-
brain undergoes modification to
form the medulla oblongata, the
pons, and cerebellum, while its
cavity is expanded to form the
fourth ventricle. The mid-brain
forms only a small part of the
adult brain; its cavity becomes
the cerebral aqueduct (aqueduct of
Cerebral peduncle
Superior peduncle
Middle peduncle
Inferior peduncle
- Medulla oblongata
FiQ. 67
. — Scheme showing the connections of the several
parts of the brain. (After Schwalbe.)
^eRE^RO-^COf?
^v
BASAL GANGLIA
«F FORE-BRAIN
II.
CORPORA
aUADRIGEMINA
RETICULAR GANGLIONI
MASS WITH CRANIA
NE'-iVE NUCLE
NTRAL GRAY (FLOOR OF
URTH VENTRICLE AND
OUND AQUEDUCT)
NTRAL GRAY OF I,
PINAL CORD
Fig. 67S. — Schematic representation of the chief ganglionic categories (I to V). (Spitzka.)
THE HIXD-BKAIX OR RHOMBENCEPHALON 7G7
Sylvius), which serves as a tubular communication between the third and fourth
ventricles; while its walls are thickened to form the corpora quadrigemina and
cerebral peduncles. The fore-brain undergoes great modification: its anterior part
or telencephalon expands laterally in the form of two hollow vesicles, the cavities
of which become the lateral ventricles, while the surrounding walls form the cere-
bral hemispheres and their commissures; the cavity of the posterior part or dien-
cephalon forms the greater part of the third ventricle, and from its walls are devel-
oped most of the structures which bound that cavity.
THE HIND-BRAIN OR RHOMBENCEPHALON.
The hind-brain or rhombencephalon occupies the posterior fossa of the cranial
cavity and lies below a fold of dura mater, the tentorium cerebelli. It consists
of (a) the myelencephalon, comprising the medulla oblongata and the lower part
of the fourth ventricle; (b) the metencephalon, consisting of the pons, cerebellum,
and the intermediate part of the fourth ventricle; and (c) the isthmus rhomben-
cephali, a constricted portion immediately adjoining the mid-brain and includ-
ing the superior peduncles of the cerebellum, the anterior medullary \elum, and
the upper part of the fourth ventricle.
The Medulla Oblongata {spinal bulb). — The medulla oblongata extends from
the lower margin of the pons to a plane passing transversely below the pyram-
idal decussation and above the first pair of cervical nerves; this plane corre-
sponds with the upper border of the atlas behind, and the middle of the odontoid
process of the axis in front; at this level the medulla oblongata is continuous
with the medulla spinalis. Its anterior surface is separated from the basilar part of
the occipital bone and the upper part of the odontoid process by the membranes
of the brain and the occipitoaxial ligaments. Its posterior surface is received into
the fossa between the hemispheres of the cerebellum, and the upper portion of it
forms the lower part of the floor of the fourth ventricle.
The medulla oblongata is pyramidal in shape, its broad extremity being directed
upward toward the pons, while its narrow, lower end is continuous with the medulla
spinalis. It measures about 3 cm. in length, about 2 cm. in breadth at its widest
part, and about 1.25 cm. in thickness. The central canal of the medulla spinalis
is prolonged into its lower half, and then opens into the cavity of the fourth ven-
tricle; the medulla oblongata may therefore be divided into a lower closed part
containing the central canal, and an upper opeji part corresponding with the lower
portion of the fourth ventricle.
The Anterior Median Fissure (fissura mediana anterior; ventral or veniromedian
fissure) contains a fold of pia mater, and extends along the entire length of the
medulla oblongata: it ends at the lower border of the pons in a small triangular
expansion, termed the foramen cecum. Its lower part is interrupted by bundles
of fibers which cross obliquely from one side to the other, and constitute the pyram-
idal decussation. Some fibers, termed the anterior external arcuate fibers, emerge
from the fissure above this decussation and curve lateralward and upward over
the surface of the medulla oblongata to join the inferior peduncle.
The Posterior Median Fissure (fissura mediana posterior; dorsal or dorsomedian
fissure) is a narrow groove; and exists only in the closed part of the medulla oblon-
gata; it becomes gradually shallower from below upward, and finally ends about
the middle of the medulla oblongata, where the central canal expands into the
cavity of the fourth ventricle.
These two fissures divide the closed part of the medulla oblongata into sym-
metrical halves, each presenting elongated eminences which, on surface view,
are continuous with the funiculi of the medulla spinalis. In the open part the
halves are separated by the anterior median fissure, and by a median raphe which
^68
NEUROLOGY
extends from the bottom of the fissure to the floor of the fourth ventricle. Further,
certain of the cranial nerves pass through the substance of the medulla oblongata,
and are attached to its surface in series with the roots of the spinal nerves; thus,
the fibers of the hypoglossal nerve represent the upward continuation of the
anterior nerve roots, and emerge in linear series from a furrow termed the
antero-lateral sulcus. Similarly, the accessory, vagus, and glossopharyngeal nerves
correspond with the posterior nerve roots, and are attached to the bottom of a sulcus
named the postero-lateral sulcus. Advantage is taken of this arrangement to sub-
divide each half of the medulla oblongata into three districts, anterior, middle,
and posterior. Although these three districts appear to be directly continuous
with the corresponding funiculi of the medulla spinalis, they do not necessarily
contain the same fibers, since some of the fasciculi of the medulla spinalis end in
the medulla oblongata, while others alter their course in passing through it.
The anterior district (Fig. 679) is named the psrramid [pyramis medulla' oblongata-)
and lies between the anterior median fissure and the antero-lateral sulcus. Its
upper end is slightly constricted,
and between it and the pons
the fibers of the abducent nerve
emerge; a little below the pons it
becomes enlarged and prominent,
and finally tapers into the anterior
funiculus of the medulla spinalis,
with which, at first sight, it ap-
pears to be directly continuous.
The two pyramids contain the
motor fibers which pass from the
brain to the medulla oblongata and
medulla spinalis, corticobulbar and
corticospinal fibers. When these
pjTamidal fibers are traced doAMi-
Brachium
poniis
CerebeUi
Fig. 679.
-Medulla oblongata and pons.
Anterior surface.
Fig. 6S0.— Decussation of pyramids. Scheme showing pas-
sage of various fasciculi from medulla spinalis to medulla ob-
longata, a. Pons. b. Medulla oblongata, c. Decussation of
the pyramids, d. Section of cer\-ical part of medulla spinalis.
1. Anterior cerebrospinal fasciculus (in red). 2. Lateral
cerebrospinal fasciculus (in red). 3. Sensory tract (fasciculi
gracilis et cuneatus) (in blue). 3'. Gracile and cuneate nuclei.
4. Antero-lateral proper fasciculus (in dotted line). 5. Pyra-
mid. 6. Lemniscus. 7. Medial longitudinal fasciculus. 8.
Ventral spinocerebellar fasciculus (in blue). 9. Dorsal spino-
cerebellar fasciculus (in yellow). (Testut.)
ward it is found that some two-thirds or more of them leave the pyramids in
successive bundles, and decussate in the anterior median fissure, forming what is
termed the pyramidal decussation. Having crossed the middle line, they pass do^^•n
in the posterior part of the lateral funiculus as the lateral cerebrospinal fascic-
THE HIND-BRAIX OR RHOMBENCEPHALON
769
ulus. The remaining fibers — i. e., those which occupy the lateral part of the
pyramid— do not cross the middle line, but are carried downward as the anterior
cerebrospinal fasciculus (Fig. GSO) into the anterior funiculus of the same side.
The greater part of the anterior proper fasciculus of the medulla spinalis is con-
tinued upward through the medulla oblongata under the name of the medial
longitudinal fasciculus.
Superior brachmm Lateral geniculate body
I I Medial geniculate body
Inferior hrachium
Piilvinar
Pineal body \
Optic tract
Superior eoUic^ili
Inferior eollicttli
Frenulum veil
Trochlear iierre
Lateral lemniscus
HuperioT peduncle
Middle peduncle
Rhomboid fossa,
Clava
Glossopharyngeal and vagus nerves ^
Optic commissure
Oculomotor
nerve
Tngeminal nerve
Acoustic nerve
Facial nerve
Abducent nerve
Hypoglossal nerve
Accessory nerve
Fig. 681. — Hind- and mid-brains; postero-lateral view.
The lateral district (Fig. CSl) is limited in front by the antero-lateral sulcus
and the roots of the hypoglossal nerve, and behind by the postero-lateral sulcus
and the roots of the accessory, vagus, and glossopharyngeal nerves. Its upper part
consists of a prominent oval mass which is named the olive, while its lower part
is of the same width as the lateral funiculus of the medulla spinalis, and appears
on the surface to be a direct continuation of it. As a matter of fact, only a portion
of the lateral funiculus is continued upward into this district, for the lateral cerebro-
spinal fasciculus passes into the pyramid of the opposite side, and the dorsal
spinocerebellar fasciculus is carried into the inferior peduncle in the posterior
district. The ventral spinocerebellar fasciculus is continued upward on tlie lateral
surface of the medulla oblongata in the same relative position it occupies in the
spinal cord until it passes under cover of the external arcuate fibers. It passes
beneath these fibers just dorsal to the olive and ventral to the roots of tlie vagus
and glossopharyngeal nerves; it continues upward through the pons along the
dorso-lateral edge of the lateral lemniscus. The remainder of the lateral funiculus
consists chiefly of the lateral proper fasciculus. Most of these fibers dip beneath
the olive and disappear from the surface; but a small strand remains superficial to
the oli^•e. In a depression at the upper end of this strand is the acoustic nerve.
The olive (oJiva; olivary body) is situated lateral to the pyramid, from which it
is separated by the antero-lateral sulcus, and the fibers of the hypoglossal nerve.
Behind, it is separated from the postero-lateral sulcus by the ventral spinocerebellar
fasciculus. In the depression between the upper end of the olive and the pons lies
the acoustic nerve. It measures about 1.25 cm. in length, and between its upper
49
770
NEUROLOGY
Superior coUiculus
Inferior coUiculus
Ventral spinocere-
bellar fasciculus
Mn.
Fig. 682. — Superficial dissection of brain-stem. Lateral \-iew.
THE HIXD-BRAIN OR RHOMBENCEPHALON
771
r*.".-;;.'.'.:. ."•.'
Stria terminalis
Lateral geniculate
Superior colliculus
External arcuate
fibers
Dorsal external
arcuate fibers
Pyramidal tract
Fig. 683. — Dissection of brain-stem. Lateral view.
772
NEUROLOGY
Stria terminalis
Medial pemcuZafe '«c<^a v<vs|im|
Curtico-tectal ^^^^l''
fibers ^^a^
Superior colliculus
Inferior colliculus ^■■-
Ventral spinocerebellar
fasciculus
Pyramidal de-
cussation
Fig. 684. — Deep dissection of brain-stem. Lateral view.
THE HIND-BRAIN OR RHOMBENCEPHALON
IIZ
Medial geniculate ^
Superior colliculus
Inferior colliculus
Ventral spinocere
bellar fas.
Anterior corri/-
missure
Ftq. 685. — Deep dissection of brain-stem. Lateral view.
774
NEUROLOGY
end and the pons there is a slight depression to which the roots of the facial nerve
are attached. The external arcuate fibers wind across the lower part of the pyra-
mid and olive and enter the inferior peduncle.
The posterior district (Fig. 686) lies behind the postero-lateral sulcus and the
roots of the accessory, vagus, and the glossopharyngeal nerves, and, like the lateral
district, is divisible into a lower and an upper portion.
Trochlear nerve
Trigeminal nerve
Facial nerve
Acmistic nerve
Cerebral peduncle
Superior peduncle
Middle peduncle
Inferior peduncle
Glossoph aryngeal
nsrve
Vagus nerve .
Accessory nerve
{cerebral part)
Hypoglossal nerve
Accessory nerve
{spinal part)
Post, roots of first
cervical nerve
Medulla spinalis
Dura mater
{laid open)
' fasciculus cvneatus
•■ Fasciculus gracilis
FiQ. 686. — Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ.
The lower part is limited behind by the posterior median fissure, and consists
of the fasciculus gracilis and the fasciculus cuneatus. The fasciculus gracilis is
placed parallel to and along the side of the posterior median fissure, and separated
from the fasciculus cuneatus by the postero-intermediate sulcus and septum.
The gracile and cuneate fasciculi are at first vertical in direction; but at the lower
part of the rhomboid fossa they diverge from the middle line in a V-shaped manner,
and each presents an elongated swelling. That on the fasciculus gracilis is named
the clava, and is produced by a subjacent nucleus of gray matter, the nucleus
gracilis; that on the fasciculus cuneatus is termed the cuneate tubercle, and is like-
wise caused by a gray nucleus, named the nucleus cuneatus. The fibers of these
fasciculi terminate by arborizing around the cells in their respective nuclei. A
third elevation, produced by the substantia gelatinosa of Rolando, is present in
the lower part of the posterior district of the medulla oblongata. It lies on the
THE HIND-BRAIN OR RHOMBENCEPHALON lib
lateral aspect of the fasciculus cuneatus, and is separated from the surface of the
medulla oblongata by a band of nerve fibers which form the spinal tract (spinal
root) of the trigeminal nerve. Narrow below, this elevation gradually expands
above, and ends, about 1.25 cm. below the pons, in a tubercle, the tubercle of
Rolando (tuber cinereinn).
The upper part of the posterior district of the medulla oblongata is occupied
by the inferior peduncle, a thick rope-like strand situated between the lower part
of the fourth ventricle and the roots of the glossopharyngeal and vagus nerves.
The inferior peduncles connect the medulla spinalis and medulla oblongata with
the cerebellum, and are sometimes named the restiform bodies. As they pass
upward, they diverge from each other, and assist in forming the lower part of the
lateral boundaries of the fourth ventricle; higher up, they are directed backward,
each passing to the corresponding cerebellar hemisphere. Near their entrance,
into the cerebellum they are crossed by several strands of fibers, which run
to the median sulcus of the rhomboid fossa, and are named the strise meduUares.
The inferior peduncle appears to be the upward continuation of the fasciculus gra-
cilis and fasciculus cuneatus; this, however, is not so, as the fibers of these fasciculi
end in the gracile and cuneate nuclei. The constitution of the inferior peduncle
will be subsequently discussed.
Caudal to the strise medullares the inferior peduncle is partly covered by the
corpus pontobulbare (Essick^), a thin mass of cells and fibers extending from the
pons between the origin of the VII and VIII cranial nerves.
Internal Structure of the Medulla Oblongata. — Although the external form of the
medulla oblongata bears a certain resemblance to that of the upper part of the
medulla spinalis, its internal structure differs widely from that of the latter, and
this for the following principal reasons: (1) certain fasciculi which extend from the
medulla spinalis to the brain, and vice versa, undergo a rearrangement in their
passage through the medulla oblongata; (2) others which exist in the medulla spin-
alis end in the medulla oblongata; (3) new fasciculi originate in the gray substance
of the medulla oblongata and pass to different parts of the brain; (4) the gray
substance, which in the medulla spinalis forms a continuous H-shaped column,
becomes greatly modified and subdivided in the medulla oblongata, where also
new masses of gray substance are added; (5) on account of the opening out of the
central canal of the medulla spinalis, certain parts of the gray substance, which
in the medulla spinalis were more or less centrally situated, are displayed in the
rhomboid fossa; (6) the medulla oblongata is intimately associated with many
of the cranial nerves, some arising form, and others ending in, nuclei within its
substance.
The Cerebrospinal Fasciculi. — The downward course of these fasciculi from the
pyramids of the medulla oblongata and their partial decussation have already
been described (page 761). In crossing to reach the lateral funiculus of the oppo-
site side, the fibers of the lateral cerebrospinal fasciculi extend backward through
the anterior columns, and separate the head of each of these columns from its
base (Figs. GST, 688). The base retains its position in relation to the ventral
aspect of the central canal, and, when the latter opens into the fourth ventricle,
appears in the rhomboid fossa close to the middle line, where it forms the nuclei
of the hypoglossal and abducent nerves; while above the level of the ventricle it
exists as the nuclei of the trochlear and oculomotor nerves in relation to the floor
of the cerebral aqueduct. The head of the column is pushed lateralward and forms
the nucleus ambiguus, which gives origin from below upward to the cranial part
of the accessory and the motor fibers of the vagus and glossopharyngeal, and still
higher to the motor fibers of the facial and trigeminal nerves.
■1 Essick, Am. Jour. Anat., 1907.
776
NEUROLOGY
The fasciculus gracilis and fasciculus cuneatus constitute the posterior sensory
fasciculi of the medulla spinalis; they are prolonged upward into the lower part
Fig. 687. — Section of the medulla oblongata through
the lower part of the decussation of the pyramids. (Tes-
tut.) 1. Anterior median fissure. 2. Posterior median
etulcus. 3. Anterior column (in red), w-ith 3', anterior
root. 4. Posterior column (in blue), with 4', posterior
roots. 5. Lateral cerebrospinal fasciculus. 6. Posterior
funiculus. The red arrow, a, a' , indicates the course the
lateral cerebrospinal fasciculus takes at the level of the
decussation of the pyramids; the blue arrow, 6, 6', indi-
cates the course which the sensorj- fibers take.
Fig. OSS. — Section of the medulla oblongata at the
level of the decussation of the pyramids. (Testut.) 1
Anterior median fissure. 2. Posterior median sulcus.
3. Motor roots. 4. Sensorj' roots. 5. Base of the
anterior column, from which the head (5') has been
detached by the lateral cerebrospinal fasciculus. 6.
Decussation of the lateral cerebrospinal fasciculus. 7.
Posterior columns (in blue). 8. Gracile nucleus.
N. VI
Nn. VII, VIII
■Decussation
Fig. 689. — Superficial dissection of brain-stem. 'S'entral view.
of the medulla oblongata, where they end respectively in the nucleus gracilis and
nucleus cuneatus. These two nuclei are continuous with the central gray substance
THE HIND-BRAIN OR RHOMBENCEPHALON
777
of the medulla spinalis, and may be regarded as dorsal projections of this, each
being covered superficially by the fibers of the corresponding fasciculus. On
transverse section (Fig, 694) the nucleus gracilis appears as a single, more or less
quadrangular mass, while the nucleus cuncatus consists of two parts: a larger,
somewhat triangular, medial nucleus, composed of small or medium-sized cells,
and a smaller lateral nucleus containing large cells.
Decussation of
superior pe-
duncle
Nucleus of
lateral
lemniscus
Decussation of
lemniscus
Internal arcu-
ate fibers
Fig. 690. — Deep dissection of brain-stem. Ventral view.
The fibers of the fasciculus gracilis and fasciculus cuneatus end by arborizing
around the cells of these nuclei (Fig. 692). From the cells of the nuclei new fibers
arise; some of these are continued as the posterior external arcuate fibers into the
inferior peduncle, and through it to the cerebellum, but most of them pass forward
through the neck of the posterior column, thus cutting off its head from its base
(Fig. 693). Curving forward, they decussate in the middle line with the correspond-
ing fibers of the opposite side, and run upward immediately behind the cerebro-
spinal fibers, as a flattened band, named the lemniscus or fillet. The decussation
of these sensory fibers is situated above that of the motor fibers, and is named
the decussation of the lemniscus or sensory decussation. The lemniscus is joined by
the spinothalamic fasciculus (page 762), the fibers of which are derived from the
cells of the gray substance of the opposite side of the medulla spinalis.
The base of the posterior column at first lies on the dorsal aspect of the central
canal, but when the latter opens into the fourth ventricle, it appears in the lateral
part of the rhomboid fossa. It forms the terminal nuclei of the sensory fibers of
778
NEUROLOGY
the vagus and glossopharyngeal nerves, and is associated with the vestibular part
of the acoustic nerve and the sensory root of the facial nerve. Still higher, it forms a
mass of pigmented cells — the locus caeruleus — in which some of the sensory fibers
of the trigeminal nerve appear to end. The head of the posterior column forms a
long nucleus, in which the fibers of the spinal tract of the trigeminal nerve largely
end.
Auditory radiation
Medial geniculate
Stria terminalis
Inferior colliculus
N.V
Nucleus incertus
Vestibular nucleus
Cochlear nucleus
Nucleus cinerea
Nucleus cuneatus
Nucleus gracilis
Nucleus spinal
tract, trigem-
inal
Lateral lemniscus
I, Inferior peduncle
Dorsal external
arcuate fibers
External arcuate
fibers
Fig. 691. — Dissection of brain-stem.
Dorsal ^•iew. The nuclear masses of the medulla are taken from model by
Weed, Carnegie Publication, Ko. 19.
The dorsal spinocerebellar fasciculus (fasciculus ccrehellos'pinalis; direct cerebellar
tract) leaves the lateral district of the medulla oblongata ; most of its fibers are carried
backward into the inferior peduncle of the same side, and through it are conveyed
to the cerebellum; but some run upward with the fibers of the lemniscus, and,
reaching the inferior colliculus, undergo decussation, and are carried to the
cerebellum through the superior peduncle.
The proper fasciculi (basis bundles) of the anterior and lateral funiculi largel}'
consist of intersegmental fibers, which link together the different segments of the
medulla spinalis; they assist in the production of the formatio reticularis of the
medulla oblongata, and many of them are accumulated into a fasciculus which
runs up close to the median raphe between the lemniscus and the rhomboid fossa ;
THE HIND-BRAIN OR RHOMBENCEPHALON
119
this strand is named the medial longitudinal fasciculus, and will be again re-
ferred to.
Gray Substance of the Medulla Oblongata (Figs. ()94, 695).— In addition to the
gracile and cnneate nuclei, there are several other nuclei to be considered. Some
of these are traceable from the gray substance of the medulla spinalis, while others
are unrepresented in it.
1. The hypoglossal nucleus is derived from the base of the anterior column;
in the lower closed part of the medulla oblongata it is situated on the ventro-
lateral aspect of the central canal; but
in the upper part it approaches the
rhomboid fossa, where it lies close to
the middle line, under an eminence
named the trigonum hypoglossi (Fig. 709).
Numerous fibers connect the two luiclei,
both nuclei send long dcndrons across the
midline to the opposite nucleus; commis-
sure fibers also connect them. The nucleus
measures about 2 cm. in length, and con-
Fig. 092. — Superior terminations of the posterior fas-
ciculi of the medulla spinalis. 1. Posterior median
sulcus. 2. Fasciculus gracilis. 3. Fasciculus cuneatus,
4. Gracile nucleus. 5. Cuneate nucleus. 0, 6', 6".
Sensory fibers forming the lemniscus. 7. Sensory
decussation. 8. Cerebellar fibers uncrossed (in black).
9. Cerebellar fibers crossed (in black). (Testut.)
Fig. 093. — Transverse section passing through the
sensory decussation. (Schematic.) 1. Anterior median
fissure. 2. Posterior median sulcus. 3, 3. Head and
base of anterior column (in red). 4. Hypoglossal nerve.
5. Bases of posterior columns. 6. Gracile nucleus. 7.
Cuneate nucleus. 8, 8. Lemniscus. 9. Sensorj- decus-
sation. 10. Cerebrospinal fasciculus. (Testut.)
sists of large multipolar nerve cells, similar to those in the anterior column of the
spinal cord, whose axons constitute the roots of the hypoglossal nerve. These
nerve roots leave the ventral side of the nucleus, pass forward between the white
reticular formation and the gray reticular formation, some between the inferior
olivary nucleus and the medial accessory olivary nucleus, and emerge from the
antero-lateral sulcus.
2. The nucleus ambiguus (Figs. 696, 697), the somatic motor nucleus of the glosso-
pharvTigeal, vagus and cranial portion of the accessory nerves, is the continuation
into the medulla oblongata of the dorso-lateral cell group of the anterior column
of the .spinal cord. Its large multipolar cells are like those in the anterior column
of the cord; they form a slender column in the deep part of the formatio reticularis
grisea about midway between the dorsal accessory olive and the nucleus of the
spinal tract of the trigeminal. It extends from the level of the decussation of the
median fillet to the upper end of the medulla ol)longata. Its fibers first pass back-
ward toward the floor of the fourth ventricle and then curve rather abruptly
lateralward and ventrally to join the fibers from the dorsal nucleus.
780
NEUROLOGY
3. The dorsal nucleus (Figs. 696, 698), nucleus ala cinerea, often called the
sensory nucleus or the terminal nucleus of the sensory fibers of the glossophar^r^lgeal
gloVsal ^^^^* !
Nticleua of medial eminence nucleics \ ,^ JSucieus gracUis
ucleus cuneatus
Inferior peduncle
Spinal tract of
trigeminal nerve
Vagus nerve
Arcuate fibers
Eaphe
Formatio reticularis grisea
Fortnatio reticularis alba
Accessory olivary nucle
Inferior olivary nudev^
Hypoglossal nerve
Anterior median fissure
Fig. G94. — Section of the medulla oblongata at about the middle of the olive. (Schwalbe.)
2fucleus of vagus
Ligula j Medial longitudinal fasciculus
Nucleus intercalatus 1 / r> • ? ?•. ■
tu.. <,i«, , Fasciculus sohtanus
Hypoglossal nucleus \ I / /
I Descending root of vestibular nerve
^ Restifonn body
Nruileus lateralis
Spinal tract oftri.
i-^ getninal nerve
* — Vagus nerve
Nucleus ambiguus
Dorsal accessory
olivary nucleus
Inferior olivary nucleus
Hypoglossal nerve
Cerebrospinal fasciculus / \ Medial accessory olivary nucleu*
Lemniscus med. Nucleus arcuatus
Fig. G95. — Transverse section of medulla oblongata below the middle of the olive.
and vagus nerves, is probably a mixed nucleus and contains not only the terminations
of the s^Tupathetic afi'erent or sensory fibers and the cells connected with them but
contains also cells which give rise to s\Tnpathetic efferent or preganglionic fibers.
THE HIND-BRAIN OR RHOMBENCEPHALON
781
These preganglionic fibers terminate in s\Tnpathetic ganglia from which the impulses
are carried by other neurons. The cells of the dorsal nucleus are spindle-shaped,
like those of the posterior colunm of the spinal cord, and the nucleus is usually
considered as representing the base of the posterior column. It measures about 2
cm. in length, and in the lower, closed part of the medulla oblongata is situated
behind the hypoglossal nucleus; whereas in the upper, open part it lies lateral to
that nucleus, and corresponds to an eminence, named the ala cinerea (trigonum
vagi), in the rhomboid fossa.
4. The nuclei of the cochlear and vestibular nerves are described on page 788.
5. The olivary nuclei (Fig. ()94)
are three in number on either side
of the middle line, viz., the inferior
olivary nucleus, and the medial
and dorsal accessory olivary nu-
clei; they consist of small, round,
yellowish cells and numerous fine
nerve fibers, (a) The inferior oli-
vary nucleus is the largest, and is
situated within the olive. It con-
sists of a gray folded lamina ar-
ranged in the form of an incom-
plete capsule, opening medially
by an aperture called the hilum:
emerging from the hilum are num-
erous fibers which collectively
constitute the peduncle of the
olive. The axons, olivocerebellar
fibers, which leave the oli\ary
nucleus pass out through the
hilum and decussate with those
from the opposite olive in the
raphe, then as internal arcuate
fibers they pass partly through
and partly around the opposite
olive and enter the inferior
peduncle to be distributed to
the cerebellar hemisphere of the
opposite side from which they
arise. The fibers are smaller
than the internal arcuate fibers
connected with the median lem-
niscus. Fibers passing in the op-
posite direction from the cerebel-
lum to the olivary nucleus are
often described but their existence
isdoubtful. Much uncertainty also
exists in regard to the connections
of the olive and the spinal cord. Important connections between the cerebrum and
the olive of the same side exist but the exact pathway is unknown. Many collaterals
from the reticular formation and from the pyramids enter the inferior olivary
nucleus. Removal of one cerebellar hemisphere is followed by atrophy of the
opposite olivary nucleus, (b) The medial accessory olivary nucleus lies between
the inferior oli\'ary nucleus and the pyramid, and forms a curved lamina, the con-
cavity of which is directed laterally. The fibers of the hypoglossal nerve, as they
Nucleus ambiguus
{IX and X)
Nucleiis of
solitary tract
Fig. 696. — The cranial nerve nuclei schematically represented;
dorsal view. Motor nuclei in red; sensorj' in blue. (The olfactory
and optic centers are not represented.)
782
NEUROLOGY
traverse the medulla, pass between the medial accessory and the inferior olivarv
nuclei, (c) The dorsal accessory olivary nucleus is the smallest, and appears on
transverse section as a curved lamina behind the inferior olivary nucleus.
6. The nucleus arcuatus is described below with the anterior external arcuate fibers.
Inferior Peduncle (rest i form body). — The position of the inferior peduncles has
already been described (page 775). Each comprises:
(1) Fibers from the dorsal spinocerebellar fasciculus, which ascends from the lateral
funiculus of the medulla spinalis.
(2) The olivocerebellar fibers from the opposite olivary nucleus.
(3) Internal arcuate fibers from the gracile and cuneate nuclei of the opposite side;
these fibers form the deeper and larger part of the inferior peduncle.
Cervical nerves
Fig. 697. — Nuclei of origin of cranial motor nerves schematically represented ; lateral \'iew.
(4) The anterior external arcuate fibers vary as to their prominence in different cases :
in some they form an almost continuous layer covering the pyramid and olive,
while in others they are barely visible on the surface. They arise from the cells
of the gracile and cuneate nuclei, and passing forward through the formatio reticu-
laris, decussate in the middle line. Most of them reach the surface by way of the
anterior median fissure, and arch backward over the pyramid. Reinforced by
others which emerge between the pyramid and olive, they pass backward over
the olive and lateral district of the medulla oblongata, and enter the inferior
peduncle. They thus connect the cerebellum with the gracile and cuneate nuclei of
the opposite side. xA.s the fibers arch across the pyramid, they enclose a small
nucleus which lies in front of and medial to the pyramid. This is named the nucleus
arcuatus, and is serially continuous above with the nuclei pontis in the pons; it
contains small fusiform cells, around which some of the arcuate fibers end, and
from which others arise.
THE HIND-BRAIN OR RHOMBENCEPHALON
783
(5) The posterior external arcuate fibers also take ()ri(>;iu in the gracile and cuiieate
nuclei; they pass to the inferior peduncle of the same side. It is uncertain whether
Sensory root of
IX
Fig. 698. — Primary termiaal nuclei of the afferent (sensory) cranial nerves schematically represented; lateral
view. The olfactory and optic centers are not represented.
15
15 lo
Fig. 699. — Diagram showing the course of the arcuate fibers. (Testut.) 1. Medulla oblongata anterior surface.
2. Anterior median fissure. 3. Fourth ventricle. 4. Inferior olivary nucleus, with the accessory olivary nuclei. 5.
Gracile nucleus, 6. Cuneate nucleus. 7. Trigeminal. 8. Inferior peduncles, seen from in front. 9. Posterior external
arcuate fibers. 10. Anterior external arcuate fibers. 11. Internal arcuate fibers. 12. Peduncle of inferior olivary
nucleus. 13. Nucleus arcuatus. 14. Vagus. 15. Hypoglossal.
784
NEUROLOGY
fibers are continued directly from the gracile and cuneate fasciculi into the inferior
peduncle.
(6) Fibers from the terminal sensory nuclei of the cranial nerves, especially the
vestibular. Some of the fibers of the vestibular nerve are thought to continue
directly into the cerebellum.
(7) Fibers from the ventral spinocerebellar fasciculus.
(8) The existence of fibers from the cerebellum (cerebellobulbar, cerebelloolivary,
and cerebellospinal) to the medulla and spinal cord is very uncertain.
Fig. 700. — The formatio reticularis of the medulla oblongata, shown by a transverse section passing through the
middle of the olive. (Testut.) 1. Anterior median fissure. 2. Fourth ventricle. 3. Formatio reticularis, with 3',
its internal part (reticularis alba), and 3", its external part (reticularis grisea). 4. Raph6. 5. Pyramid. 6. Lemniscus.
7. Inferior olivary nucleus with the two accessory olivary nuclei. 8. Hypoglossal nerve, with 8', its nucleus of origin.
9. Vagus nerve, with 9', its nucleus of termination. 10. Lateral dorsal acoustic nucleus. 11. Nucleus ambiguus
(nucleus of origin of motor fibers of glossopharyngeal, vagus, and cerebral portion of spinal accessory). 12. Gracile
nucleus. 13. Cuneate nucleus. 14. Head of posterior column, with 14', the lower sensory root of trigeminal nerve.
15. Fasciculus solitarius. 16. Anterior external arcuate fibers, with 16', the nucleus arcuatus. 17. Nucleus lateralis
18. Nucleus of fasciculus teres. 19. Ligula.
Formatio Reticularis (Fig. 700). — This term is applied to the coarse reticulum
which occupies the anterior and lateral districts of the medulla oblongata. It
is situated behind the pyramid and oli^•e, extending laterally as far as the inferior
peduncles, and dorsally to within a short distance of the rhomboid fossa. The
reticulum is caused by the intersection of bundles of fibers running at right angles
to each other, some being longitudinal, others more or less transverse in direction.
The formatio reticularis presents a different appearance in the anterior district from
what it does in the lateral; in the former, there is an almost entire absence of nerve
cells, and hence this part is known as the reticularis alba; whereas in the lateral
district nerve cells are numerous, and as a consequence it presents a gray appear-
ance, and is termed the reticularis grisea.
In the substance of the formatio reticularis are two small nuclei of gray matter:
one, the inferior central nucleus {nucleus of Roller), near the dorsal aspect of the hilus
of the inferior olivary nucleus; the other, the nucleus lateralis, between the olive
and the spinal tract of the trigeminal nerve.
In the reticularis alba the longitudinal fibers form two well-defined fasciculi,
viz.: (1) the lemniscus, which lies close to the raphe, immediately behind the
fibers of the pyramid; and (2) the medial longitudinal fasciculus, which is continued
upward from the anterior and lateral proper fasciculi of the medulla spinalis, and,
I
THE HIND-BRAIN OR RHOMBENCEPHALON 785
in the upper part of the medulla oblongata, lies between the lemniscus and the gray
substance of the rhomboid fossa. The longitudinal fibers in the reticularis grisea
are derived from the lateral funiculus of the medulla spinalis after the lateral
cerebrospinal fasciculus has passed over to the opj>osite side, and the dorsal sj)ino-
cerebellar fasciculus has entered the inferior peduncle. They form indeterminate
fibers, with the exception of a bundle named the fasciculus solitarius, wliich is made up
of descending fibers of the vagus and glossopharyngeal nerves. The transverse
fibers of the formatio reticularis are the arcuate fibers already described (page 782).
The Pons {pons Varoli). — The pons or forepart of the hind-brain is situ-
ated in front of the cerebellum. From its superior surface the cerebral peduncles
emerge, one on either side of the middle line. Curving around each peduncle, close
to the upper surface of the pons, a thin white band, the taenia pontis, is frequently
seen; it enters the cerebellum between the middle and superior i)e(luncles. Behind
and below, the pons is continuous with the medulla oblongata, but is separated
from it in front by a furrow in which the abducent, facial, and acoustic nerves
appear.
Its ventral or anterior surface {pars basilaris pontw) is very prominent, markedly
convex from side to side, less so from above downward. It consists of transverse
fibers arched like a bridge across the middle line, and gathered on either side into
a compact mass which forms the middle peduncle. It rests upon the clivus of the
sphenoidal bone, and is limited above and below by well-defined borders. In the
middle line is the sulcus basilaris for the lodgement of the basilar artery; this sulcus
is bounded on either side by an eminence caused by the descent of the cerebrospinal
fibers through the substance of the pons. Outside these eminences, near the upper
border of the pons, the trigeminal nerves make their exit, each consisting of a
smaller, medial, motor root, and a larger, lateral, sensory root; vertical lines
drawn immediately beyond the trigeminal nerves, may be taken as the boundaries
between the ventral surface of the pons and the middle cerebellar peduncle.
Its dorsal or posterior surface {pars dorsalis pontis) , triangular in shape, is hidden
by the cerebellum, and is bounded laterally by the superior peduncle; it forms
the upper part of the rhomboid fossa, with which it will be described.
Structure (Fig. 701). — Transverse sections of the pons show it to be composed
of two parts which differ in appearance and structure: thus, the basilar or ventral
portion consists for the most part of fibers arranged in transverse and longitudinal
bundles, together with a small amount of gray substance; while the dorsal tegmental
portion is a continuation of the reticular formation of the medulla oblongata,
and most of its constituents are continued into the tegmenta of the cerebral
peduncles.
The basilar part of the pons consists of — («) superficial and deep transverse
fibers, {b) longitudinal fasciculi, and (c) some small nuclei of gray substance,
termefl the nuclei pontis which give rise to the transverse fibers.
The superficial transverse fibers {fihroe pontis superficialcs) constitute a rather
thick layer on the ventral surface of -the pons, and are collected into a large
rounded bundle on either side of the middle line. This bundle, with the addition
of some transverse fibers from the deeper part of the pons, forms the greater part
of the brachium pontis.
The deep transverse fibers {fihrce pontis profunda^) partly intersect and partly
lie on the dorsal aspect of the cerebrospinal fibers. They course to the lateral
border of the pons, and form part of the middle peduncle; the further connections
of this brachium will be discussed with the anatomy of the cerebellum.
The longitudinal fasciculi {fasciculi longitudinales) are derived from the cerebral
peduncles, and enter the upper surface of the pons. They stream downward on
either side of the middle line in larger or smaller bundles, separated from each
other by the deep transverse fibers; these longitudinal bundles cause a forward
50
786
NEUROLOGY
projection of the superficial transverse fibers, and thus give rise to the eminences
on the anterior surface. Some of these fibers end in, or give off collateral to, the
nuclei pontis. An important pathway is thus formed between the cerebral cortex
and the cerebellum, the first neuron haAing its cell body in the cortex and sending
its axon through the internal capsule and cerebral peduncle to form synapses either
by terminals or collaterals with cell bodies situated in the nuclei pontis. Axons
from these cells form the transverse fibers which pass through the middle peduncle
into the cerebellum. Others after decussating, terminate either directly or indi-
rectly in the motor nuclei of the trigeminal, abducent, facial, and hA-poglossal
nerves; but most of them are carried through the pons, and at its lower surface
are collected into the pyramids of the medulla. The fibers which end in the motor
nuclei of the cranial nerves are derived from the cells of the cerebral cortex, and
bear the same relation to the motor cells of the cranial nerves that the cerebro-
SuperioT peduncle
Mesencephalic root V.
Nn. mes. root
Med. long, fas.-
Lateral lemniscus
Formatio reticularis^^
Medial _
lemniscus
Transverse
fibers
Ant. med,
velum
White \
stratum i Gray stratum
Fourth ventricle
Cerebrospinal \/
fasciculi
Trigeminal'
Fig. 701. — Coronal section of the pons, at its upper part.
spinal fibers bear to the motor cells in the anterior column of the medulla spinalis.
Probably none of the collaterals or terminals of the cerebrospinal and cerebro-
bulbar fibers end directly in the motor nuclei of the spinal and cranial nerves, one or
more association neurons are probably interpolated in the pathway.
The nuclei pontis are serially continuous with the arcuate nuclei in the medulla,
and consist of small groups of multipolar nerve cells which are scattered between
the bundles of transverse fibers.
The dorsal or tegmental part of the pons is chiefly composed of an upward con-
tinuation of the reticular formation and gray substance of the medulla oblongata.
It consists of transverse and longitudinal fibers and also contains important gray
nuclei, and is subdivided bv a median raphe, which, however, does not extend into
the basilar part, being obliterated by the transverse fibers. The transverse fibers
in the lower part of the pons are collected into a distmct strand, named the
THE HIND-BRAIX OR RHOMBENCEPHALON 7bl
trapezoid body. This consists of fibers which arise from the cells of the cochlear
nucleus, and will be referred to in connection with the cochlear division of the
acoustic nerve. In the substance of the trapezoid body is a collection of nerve
cells, which constitutes the trapezoid nucleus. The longitudinal fibers, which are
continuous with those of the medulla oblongata, are mostly collected into two
fasciculi on either side. One of these lies between the trapezoid body and
the reticular formation, and forms the upward prolongation of the lemniscus;
the second is situated near the floor of the fourth ventricle, and is the medial
longitudinal fasciculus. Other longitudinal fibers, more diffusely distributed, arise
from the cells of the gray substance of the pons.
The rest of the dorsal part of the pons is a continuation upward of the formatio
reticularis of the medulla oblongata, and, like it, presents the appearance of a net-
work, in the meshes of which are numerous nerve cells. Besides these scattered
nerve cells, there are some larger masses of gray substance, viz., the superior
olivary nucleus and the nuclei of the trigeminal, abducent, facial, and acoustic
nerves (Fig. 600).
1. The superior olivary nucleus {nucleus olivaris superior) is a small mass of gray
substance situated on the dorsal surface of the lateral part of the trapezoid body.
Rudimentary in man, but well developed in certain animals, it exhibits the same
structure as the inferior olivary nucleus, and is situated immediately above it.
Some of the fibers of the trapezoid body end by arborizing around the cells of
this nucleus, while others arise from these cells.
2. The nuclei of the trigeminal nerve (nuclei n. irigemini) in the pons are two in
number: a motor and a sensory. The motor nucleus is situated in the upper part of
the pons, close to its posterior surface and along the line of the lateral margin of the
fourth ventricle. It is serially homologous with the nucleus ambiguus and the
dorso-lateral cell group of the anterior column of the spinal cord. The axis-cylinder
processes of its cells form the motor root of the trigeminal nerve. The mesen-
cephalic root arises from the gray substance of the floor of the cerebral aqueduct,
johis the motor root and probably conveys fibers of muscle sense from the tem-
poral, masseter and pterygoid muscles. It is not altogether clear whether the
mesencephalic root is motor or sensory. The sensory nucleus is lateral to the
motor one, antl beneath the superior peduncle. Some of the sensory fibers of
the trigeminal nerve end in this nucleus; but the greater number descend, under the
name of the spinal tract of the trigeminal nerve, to end in the substantia gelatinosa
of Rolando. The roots, motor and sensory, of the trigeminal ner\'e jiass through
the substance of the pons and emerge near the upper margin of its anterior surface.
3. The nucleus of the abducent nerve (nucleus n. abduccntis) is a circular mass of
gray substance situated close to the floor of the fourth ventricle, above the striae
medullares and subjacent to the medial eminence: it lies a little lateral to the
ascending part of the facial nerve. The fibers of the abducent nerve pass forward
through the entire thickness of the pons on the medial side of the superior olivary
nucleus, and between the lateral fasciculi of the cerebrospinal fibers, and emerge
in the furrow between the lower border of the pons and the pyramid of the
medulla oblongata.
4. The nucleus of the facial nerve (nucleus n. fascialis) is situated deeply in the
reticular formation of the pons, on the dorsal aspect of the superior olivary nucleus,
and the roots of the nerve derived from it pursue a remarkably tortuous course in
the substance of the pons. At first they pass backward and medialward until they
reach the rhomboid fossa, close to the median sulcus, where they are collected into
a round bundle; this passes upward and forward, producing an elevation, the
coUiculus facialis, in the rhomboid fossa, and then takes a sharp bend, and arches
lateralward through the substance of the pons to emerge at its lower border in
the interval between the olive and the inferior peduncle of the medulla oblongata.
788 NEUROLOGY
5. The nucleus of the cochlear nerve consists of: (a) the lateral cochlear nucleus,
corresponding to the tuberculum acusticum on the dorso-lateral surface of the
inferior peduncle; and ih) the ventral or accessory cochlear nucleus, placed between
the two divisions of the nerve, on the ventral aspect of the inferior peduncle.
The nuclei of the vestibular nerve, (a) The medial (dorsal or chief vestibular
nucleus), corresponding to the lower part of the area acustica in the rhomboid
fossa; the caudal end of this nucleus is sometimes termed the descending or spinal
vestibular nucleus, {h) The lateral or nucleus of Deiters, consisting of large cells
and situated in the lateral angle of the rliomboid fossa; the dorso-lateral part of
this nucleus is sometimes termed the nucleus of Bechterew.
The fibers of the vestibular nerve enter the medulla oblongata on the medial
side of those of the cochlear, and pass between the inferior peduncle and the spinal
tract of the trigeminal. They then divide into ascending and descending fibers.
The latter end by arborizing around the cells of the medial nucleus, which is situ-
ated in the area acustica of the rhomboid fossa. The ascending fibers either end
in the same manner or in the lateral nucleus, which is situated lateral to the area
acustica and farther from the ventricular floor. Some of the axons of the cells of
the lateral nucleus, and possibly also of the medial nucleus, are continued upward
through the inferior peduncle to the roof nuclei of the opposite side of the cere-
bellum, to which also other fibers of the vestibular root are prolonged without
interruption in the nuclei of the medulla oblongata. A second set of fibers from
the medial and lateral nuclei end partly in the tegmentum, while the remainder
ascend in the medial longitudinal fasciculus to arborize around the cells of the
nuclei of the oculomotor nerve.
The Cerebellum. — The cerebellum constitutes the largest part of the hind-
brain. It lies behind the pons and medulla oblongata; between its central portion
and these structures is the cavity of the fourth ventricle. It rests on the inferior
occipital fossse, while above it is the tentorium cerebelli, a fold of dura mater
which separates it from the tentorial surface of the cerebrum. It is somewhat
oval in form, but constricted medially and flattened from above downward, its
greatest diameter being from side to side. Its surface is not convoluted like that
of the cerebrum, but is traversed by numerous curved furrows or sulci, which
vary in depth at different parts, and separate the laminae of which it is composed.
Its average weight in the male is about 150 gms. In the adult the propor-
tion between the cerebellum and cerebrum is about 1 to 8, in the infant about
1 to 20.
Lobes of the Cerebellum. — The cerebellum consists of three parts, a median and
two lateral, which are continuous Avith each other, and are substantially the same
in structure. The median portion is constricted, and is called the vermis, from its
annulated appearance which it owes to the transverse ridges and furrows upon it;
the lateral expanded portions are named the hemispheres. On the upper surface
of the cerebellum the vermis is elevated above the level of the hemispheres, but
on the under surface it is sunk almost out of sight in the bottom of a deep depres-
sion between them; this depression is called the vallecula cerebelli, and lodges the
posterior part of the medulla oblongata. The part of the vermis on the upper
surface of the cerebellum is named the superior vermis; that on the lower surface,
the inferior vermis. The hemispheres are separated below and behind by a deep
notch, the posterior cerebellar notch, and in front by a broader shallower notch,
the anterior cerebellar notch. The anterior notch lies close to the pons and upper
part of the medulla, and its superior edge encircles the inferior colliculi and the
superior cerebellar peduncle. The posterior notch contains the upper part of the
falx cerebelli, a fold of dura mater.
The cerebellum is characterized by a laminated or foliated appearance; it is
marked by deep, somewhat curved fissures, which extend for a considerable dis-
THE HIND-BRAIN OR RHOMBENCEPHALON
789
tance into its substance, and divide it into a series of layers or leaves. The largest
and deepest fissure is named the horizontal sulcus. It commences in front of the
pons, and passes horizontally around the free margin of the hemisphere to the
middle line behind, and divides the cerebellum into an upper and a lower portion.
Several secondary but deep fissures separate the cerebellum into lobes, and these
are further subdivided by shallower sulci, which separate the individual folia or
laminae from each other. Sections across the laminae show that the folia, though
differing in appearance from the convolutions of the cerebrum, are analogous
to them, inasmuch as they consist of central white substance covered by gray
substance.
The cerebellum is connected to the cerebrum, pons, and medulla oblongata;
to the cerebrum by the superior peduncle, to the pons by the middle peduncle,
and to the medulla oblongata by the inferior peduncles.
Ala lobuli centralis
PrcBclival fissure
Lobulus central
Horizontal v^,s v
sulcus _ ^'^XxO
Postclival
fissure
I
mowticuli
Fig. 702. — Upper surface of the cerebellum. (Schafer.)
The upper surface of the cerebellum (Fig. 702) is elevated in the middle and sloped
toward the circumference, the hemispheres being connected together by the supe-
rior vermis, which assumes the form of a raised median ridge, most prominent
in front, but not sharply defined from the hemispheres. The superior vermis is
subdivided from before backward into the lingula, the lobulus centralis, the mon-
ticulus and the folium vermis, and each of these, with the e.xception of the lingula,
is continuous with the corresponding parts of the hemispheres — the lobulus
centralis with the alae, the monticulus with the quadrangular lobules, and the
folium vermis with the superior semilunar lobules.
The lingula {lingula cerebelli) is a small tongue-shaped process, consisting of
four or five folia; it lies in front of the lobulus centralis, and is concealed by it.
Anteriorly, it rests on the dorsal surface of the anterior medullary velum, and its
white substance is continuous with that of the velum.
The Lobulus Centralis and Alse. — The lobulus centralis is a small square lobule,
situated in the anterior cerebellar notch. It overlaps the lingula, from which it
is separated by the precentral fissure; laterally, it extends along the upper and
anterior part of each hemisphere, where it forms a wing-like prolongation, the ala
lobuli centralis.
The Monticulus and Quadrangular Lobules. — The monticulus is the largest part
of the superior vermis. Anteriorly, it overlaps the lobulus centralis, from which
it is separated by the postcentral fissure ; laterally, it is continuous with the quad-
rangular lobule in the hemispheres. It is divided by the preclival fissure into an
790
NEUROLOGY
anterior, raised part, the culmen or summit, and a posterior sloped part, the clivus;
the quadrangular lobule is similarly divided. The culmen and the anterior parts
of the quadrangular lobules form the lobus culminis ; the clivus and the posterior
parts, the lobus clivi.
The Folium Vermis and Superior Semilunar Lobule. — The folium vermis {folium
cacuminis; cacuminal lobe) is a short, narrow, concealed band at the posterior
extremity of the vermis, consisting apparently of a single folium, but in reality
marked on its upper and under surfaces by secondary fissures. Laterally, it
expands in either hemisphere into a considerable lobule, the superior semilunar
lobule (lobulus semilunaris superior; postero-suyerior lobules), which occupies the
posterior third of the upper surface of the hemisphere, and is bounded below by
the horizontal sulcus. The superior semilunar lobules and the folium vermis form
the lobus semilunaris.
Postnodular fissure
Ant. medullary velum
Lobulus centralis
Ala lohult centralis Flocculus
Ilnrizontal sulcus
Tuber vermis
Fig. 703. — Under surface of the cerebellum. (Schafer.
The under surface of the cerebellum (Fig. 703) presents, in the middle line, the
inferior vermis, buried in the vallecula, and separated from the hemisphere on either
side by a deep groove, the sulcus valleculas. Here, as on the upper surface, there
are deep fissures, dividing it into separate segments or lobules; but the arrangement
is more complicated, and the relation of the segments of the vermis to those of the
hemispheres is less clearly marked. The inferior vermis is subdivided from before
backward, into (1) the nodule, (2) the uvula, (3) the pyramid, and (4) the tuber
vermis; the corresponding parts on the hemispheres are (1) the flocculus, (2) the
tonsilla cerebelli, (3) the biventral lobule, and (4) the inferior semilunar lobule. The
three main fissures are (1) the postnodular fissure, which runs transversely across
the vermis, between the nodule and the uvula. In the hemispheres this fissure
passes in front of the tonsil, crosses between the flocculus in front and the biventral
lobule behind, and joins the anterior end of the horizontal sulcus. (2) The pre-
pyramidal fissure crosses the vermis between the uvula in front and the pyramid
behind, then curves forward between the tonsil and the biventral lobe, to join
the postnodular fissure. (3) The postpyramidal fissure passes across the vermis
between the pyramid and the tuber vermis, and, in the hemispheres, courses
behind the tonsil and biventral lobules, and then along the lateral border of the
biventral lobule to the postnodular sulcus; in the hemisphere it forms the anterior
boundary of the inferior semilunar lobule.
The Nodule and Flocculus. — The nodule (tiodulus vermis; nodular lobe) , or anterior
end of the inferior vermis, abuts against the roof of the fourth ventricle, and can
THE HIND-BRAIN OR RHOMBENCEPHALON 791
only be distinctly seen after the cerebellum has been separated from the medulla
oblongata and pons. On either side of the nodule is a thin layer of white sub-
stance, named the posterior medullary velum. It is semilunar in form, its convex
border being continuous with the white substance of the cerebellum; it extends
on either side as far as the flocculus. The flocculus is a prominent, irregular
lobule, situated in front of the biventral lobule, between it and the middle cere-
bellar peduncle. It is subdivided into a few small laminae, and is connected to
the inferior medullary velum by its central white core. The flocculi, together
with the posterior medullary velum and nodule, constitute the lobus noduli.
The Uvula and Tonsilla. — The uvula (uvula vermis; uvular lobe) forms a consid-
erable portion of the inferior vermis; it is separated on either side from the tonsil
by the sulcus valleculae, at the bottom of which it is connected to the tonsil by a
ridge of gray matter, indented on its surface by shallow furrows, and hence called
the furrowed band. The tonsilla {tonsilla cerebelli; amygdaline nucleus) is a rounded
mass, situated in the hemispheres. Each lies in a deep fossa, termed the bird's
nest {nidus avis), between the uvula and the biventral lobule. The uvula and ton-
sillse form the lobus uvulae.
The Pyramid and Biventral lobules constitute the lobus pyramidis. The pyramid
is a conical projection, forming the largest prominence of the inferior vermis.
It is separated from the hemispheres by the sulcus valleculse, across which it is
connected to the biventral lobule by an indistinct gray band, analogous to the
furrowed band already described. The biventral lobule is triangular in shape;
its apex points backward, and is joined by the gray band to the pyramid. The
lateral border is separated from the inferior semilunar lobule by the postpyramidal
fissure. The base is directed forward, and is on a line with the anterior border of
the tonsil, and is separated from the flocculus by the postnodular fissure.
The Tuber Vermis {tuber vahulce) and the Inferior Semilunar Lobule {lobulus semi-
lunaris inferior; postero-superior lobule) collectively form the lobus tuberus {tubercB
lobe). The tuber vermis, the most posterior division of the inferior vermis, is of
small size, and laterally spreads out into the large inferior semilunar lobules,
which comprise at least two-thirds of the inferior surface of the hemisphere.
Internal Structure of the Cerebellum. — The cerebellum consists of white and gray
substance.
White Substance. — If a sagittal section (Fig. 704) be made through either hemi-
sphere, the interior will be found to consist of a central stem of white substance,
in the middle of which is a gray mass, the dentate nucleus. From the surface of this
central white stem a series of plates is prolonged; these are covered with gray
substance and form the laminae. In consequence of the main branches from the
central stem dividing and subdividing, a characteristic appearance, named the
arbor vitae, is presented. If the sagittal section be made through the middle of
the vermis, it will be found that the central stem divides into a vertical and a hor-
izontal branch. The vertical branch passes upward to the culmen monticuli,
where it subdivides freely, one of its ramifications passing forward and upward
to the central lobule. The horizontal branch passes backward to the folium vermis,
greatly diminished in size in consequence of having given off large secondary
branches; one, from its upper surface, ascends to the clivus monticuli; the others
descend, and enter the lobes in the inferior vermis, viz., the tuber vermis, the
pyramid, the uvula, and the nodule.
The white substance of the cerebellum includes two sets of nerve fibers: (1)
projection fibers, (2) librae propriae.
Projection Fibers. — ^The cerebellum is connected to the other parts of the brain
by three large bundles of projection fibers, viz., to the cerebrum by the superior
peduncle, to the pons by the middle peduncle, and to the medulla oblongata by
the inferior peduncles (Fig. 705).
792
NEUROLOGY
The superior cerebellar peduncles {hrachia conjunctiva), two in number, emerge
from the upper and medial part of the white substance of the hemispheres and
are placed under cover of the upper part of the cerebellum. They are joined to each
other across the middle line by the anterior medullary velum, and can be followed
,,«. °1!^°''^V<3.
o<s Ala lohvli centralis
Lingula
'i^< Superior peduncle
Horizontal "
sulcus ~""'-
TONSll-
Nodule Fourth ventricle
FiQ. 704. — Sagittal section of the cerebellum, near the junction of the vermis with the hemisphere. (Schafer.)
Superior peduncle
Inferior peduncle
Middle peduncle
trigeminal jj
7ierve
Acoustic nerve
Pyramid
Olive
Inferior peduncle
Fig. 705. — Dissection showing the projection fibers of the cerebellum, (.\fter E. B. Jamieson.)
upward as far as the inferior colliculi, under which they disappear. Below; they
form the upper lateral boundaries of the fourth ventricle, but as they ascend they
converge on the dorsal aspect of the ventricle and thus assist in roofing it in.
The fibers of the superior peduncle are mainly derived from the cells of the
THE HIND-BRAIN OR RHOMBENCEPHALON 793
dentate nucleus of the cerebellum and emerge from the hilus of this nucleus;
a few arise from the cells of the smaller gray nuclei in the cerebellar white sub-
stance, and others from the cells of the cerebellar cortex. They are continued
upward beneath the corpora quadrigemina, and the fibers of the two ix-duncles under-
go a complete decussation ventral to the Sylvian aqueduct. Having crossed the
middle line they divide into ascending and descending groups of fibers, the former
ending in the red nucleus, the thalamus, and the nucleus of the oculomotor nerve,
while the descending fibers can be traced as far as the dorsal part of the pons;
Cajal believes them to be continued into the anterior funiculus of the medulla
spinalis.
As already stated (page 762), the majority of the fibers of the ventral spino-
cerebellar fasciculus of the medulla spinalis pass to the cerebellum, which they
reach by way of the superior peduncle.
The middle cerebellar peduncles (hrachia pontis) (Fig. 705) are composed entirely of
centripetal fibers, which arise from the cells of the nuclei pontis of the opposite side
and end in the cerebellar cortex; the fibers are arranged in three fasciculi, superior,
inferior, and deep. The superior fasciculus, the most superficial, is derived from
the upper transverse fibers of the pons; it is directed backward and lateralward
superficial to the other two fasciculi, and is distributed mainly to the lobules on
the inferior surface of the cerebellar hemisphere and to the parts of the superior
surface adjoining the posterior and lateral margins. The inferior fasciculus is
formed by the lowest transverse fibers of the pons; it passes under cover of the
superior fasciculus and is continued downward and backward more or less parallel
with it, to be distributed to the folia on the under surface close to the vermis.
The deep fasciculus comprises most of the deep transverse fibers of the pons.
It is at first covered by the superior and inferior fasciculi, but crosses obliquely
and appears on the medial side of the superior, from which it receives a bundle;
its fibers spread out and pass to the upper anterior cerebellar folia. The fibers
of this fasciculus cover those of the restiform body.^
The inferior cerebellar peduncles {restiform bodies) pass at first upward and lateral-
w^ard, forming part of the lateral walls of the fourth ventricle, and then bend
abruptly backward to enter tlie cerebellum between the superior and middle
peduncles. Each contains the following fasciculi: (1) the dorsal spinocerebellar
fasciculus of the medulla spinalis, which ends mainly in the superior vermis; (2)
fibers from the gracile and cuneate nuclei of the same and of the opposite sides;
(3) fibers from the opposite olivary nuclei ; (4) crossed and uncrossed fibers from the
reticular formation of the medulla oblongata; (5) vestibular fibers, derived partly
from the vestibular division of the acoustic nerve and partly from the nuclei in
which this division ends — these fibers occupy the medial segment of the inferior
peduncle and divide into ascending and descending groups of fibers, the ascending
fibers partly end in the roof nucleus of the opposite side of the cerebellum; (6)
cerebellobulbar fibers which come from the opposite roof nucleus and probably
from the dentate nucleus, and are said to end in the nucleus of Deiters and in the
formatio reticularis of the medulla oblongata; (7) some fibers from the ventral
spinocerebellar fasciculus are said to join the dorsal spinocerebellar fasciculus.
The anterior medullary velum {velum medullare anterius; valve of Vieussens; superior
medullary velum) is a thin, transparent lamina of white substance, which stretches
between the superior peduncle; on the dorsal surface of its lower half the folia
and Hngula are prolonged. It forms, together with the superior peduncle, the
roof of the upper part of the fourth ventricle; it is narrow above, where it passes
beneath the inferior colliculi, and broader below, where it is continuous with the
white substance of the superior vermis. A slightly elevated ridge, the frsenulum
' See article by E. B. Jamieson, Journal of Anatomy and Physiology, vol. xliv.
794 NEUROLOGY
veli, descends upon its upper part from between the inferior colliculi, and on either
side of this the trochlear nerve emerges.
The posterior medullary velum (velum medidlare posterius; inferior medullary velum)
is a thin layer of white substance, prolonged from the white center of the cerebellum,
above and on either side of the nodule; it forms a part of the roof of the fourth
ventricle. Somewhat semilunar in shape, its convex edge is continuous with the
white substance of the cerebellum, while its thin concave margin is apparently
free; in reality, however, it is continuous with the epithelium of the ventricle,
which is prolonged downward from the posterior medullary velum to the ligulfe.
The two medullary vela are in contact with each other along their line of emer-
gence from the white substance of the cerebellum; and this line of contact forms
the summit of the roof of the fourth ventricle, which, in a vertical section through
the cavity, appears as a pointed angle.
The Fibrse Proprise of the cerebellum are of two kinds: (1) commissural fibers,
which cross the middle line at the anterior and posterior parts of the vermis and
connect the opposite halves of the cerebellum; (2) arcuate or association fibers,
which connect adjacent laminae with each other.
Gray Substance. — The gray substance of the cerebellum is found in two situations:
(1) on the surface, forming the cortex; (2) as independent masses in the anterior.
(1) The gray substance of the cortex presents a characteristic foliated appearance,
due to the series of laminse which are given off from the central white substance;
these in their turn give off secondary laminae, which are covered by gray substance.
Externally, the cortex is covered by pia mater; internally is the medullary center,
consisting mainly of nerve fibers.
Microscopic Appearance of the Cortex (Fig. 706). — The cortex consists of two
layers, viz., an external gray molecular layer, and an internal rust-colored nuclear
layer; between these is an incomplete stratum of cells which are characteristic of
the cerebellum, viz., the cells of Purkinje.
The external gray or molecular layer consists of fibers and cells. The nerve fibers
are delicate fibrillae, and are derived from the following sources: (a) the dendrites
and axon collaterals of Purkinje's cells; (6) fibers from cells in the nuclear layer;
(c) fibers from the central white substance of the cerebellum; (d) fibers derived
from cells in the molecular laver itself. In addition to these are other fibers, which
have a vertical direction, and are the processes of large neuroglia cells, situated
in the nuclear layer. They pass outward to the periphery of the gray matter,
where they expand into little conical enlargements which form a sort of limiting
membrane beneath the pia mater, analogous to the membrana limitans interna
in the retina, formed by the sustentacular fibers of INIuller.
The cells of the molecular layer are small, and are arranged in two strata, an
outer and an inner. They all possess branched axons; those of the inner layer
are termed basket cells ; they run for some distance parallel with the surface of the
folium — giving off collaterals which pass in a vertical direction toward the bodies
of Purkinje's cells, around which they become enlarged, and form basket-like
net-works.
, The cells of Purkinje form a single stratum of large, flask-shaped cells at the
junction of the molecular and nuclear layers, their bases resting against the latter;
in fishes and reptiles they are arranged in several layers. The cells are flattened
in a direction transverse to the long axis of the folium, and thus appear broad
in sections carried across the folium, and fusiform in sections parallel to the long
axis of the folium. From the neck of the flask one or more dendrites arise and pass
into the molecular layer, where they subdivide and form an extremely rich arbores-
cence, the various subdivisions of the dendrites being covered by lateral spine-
like processes. This arborescence is not circular, but, like the cell, is flattened at
right angles to the long axis of the folium; in other words, it does not resemble
THE HIND-BRAIN OR RHOMBENCEPHALON
795
a round bush, but has been aptly compared by Obersteiner to the branches of a
fruit tree trained against a trelHs or a wall. Hence, in sections carried across
the folium the arborescence is broad and expanded ; whereas in those which are
parallel to the long axis of the folium, the arborescence, like the cell itself, is
seen in profile, and is limited to a narrow area.
From the bottom of the flask-shaped cell the axon arises; this passes through
the nuclear layer, and, becoming medullated, is continued as a nerve fiber in the
subjacent white substance. As this axon traverses the granular layer it gives off
fine collaterals, some of which run back into the molecular laver.
Cell of Purkinje
Axons of
granule cells
cut trans-
versely
Small cell
of molecular.
layer
Basket cell.
\ Molecular
I layer
Golgi cell
I Nuclear
layer
j Axon of cell of Purkinje
Neuroglia cell
Fig. 706. — Transverse section of a cerebellar folium. (Diagrapimatic, after Cajal and Kolliker.)
' Tendril fiber
Moss fiber
The internal rust-colored or nuclear layer (Fig. 706) is characterized by containing
numerous small nerve cells of a reddish-brown color, together with many nerve
fibrils. Most of the cells are nearly spherical and provided with short dendrites
which spread out in a spider-like manner in the nuclear layer. Their axons pass
outward into the molecular layer, and, bifurcating at right angles, run for some
distance parallel with the surface. In the outer part of the nuclear layer are some
larger cells, of the type II of Golgi. Their axons undergo frequent division as soon
as they leave the nerve cells, and pass into the nuclear layer; while their dendrites
ramify chiefly in the molecular layer.
796
NEUROLOGY
Finally, in the gray substance of the cerebellar cortex there are fibers which
come from the white center and penetrate the cortex. The cell-origin of these
fibers is unknown, though it is believed that it is probably in the gray substance
of the medulla spinalis. Some of these fibers end in the nuclear layer by dividing
into numerous branches, on which are to be seen peculiar moss-like appendages;
hence they have been termed by Ramon y Cajal the moss fibers; they form an
arborescence around the cells of the nuclear layer and are said to come from fibers
in the inferior peduncle. Other fibers, the clinging or tendril fibers, derived from the
medullary center can be traced into the molecular layer, where their branches
cling around the dendrites of Purkinje's cells. They are said to come from fibers
of the middle peduncle.
(2) The independent centers of gray substance in the cerebellum are four in
number on either side: one is of large size, and is known as the nucleus dentatus;
the other three, much smaller, are situated near the middle of the cerebellum, and
are known as the nucleus emboliformis, nucleus globosus, and nucleus fastigii.
Niideiis dentatus
Superior peduncle
Corpma quadrigemina
Inferior olivary nucleus
PiQ. 707. — Sagittal section through right cerebellar hemisphere. The right olive has also been cut sagitally.
The nucleus dentatus (Fig. 707) is situated a little to the medial side of the center
t)f the stem of the white substance of the hemisphere. It consists of an irregularly
folded lamina, of a grayish-yellow color, containing white fibers, and presenting
on its antero-medial aspect an opening, the hilus, from which most of the fibers of
the superior peduncle emerge (page 792).
The nucleus emboliformis lies immediately to the medial side of the nucleus
dentatus, and parth' covering its hilus. The nucleus globosus is an elongated
mass, directed antero-posteriorly, and placed medial to preceding. The nucleus
fastigii is somewhat larger than the other two, and is situated close to the middle
line at the anterior end of the superior vermis, and immediately over the roof
of the fourth ventricle, from which it is separated by a thin layer of white substance.
The cerebellum is concerned with the coordination of movements necessary in equilibration,
locomotion and prehension. In it terminate pathways conducting impulses of muscle sense,
tendon sense, joint sense and equilibratory disturbances. With the exception of the ventral
spinocerebellar fasciculus these impulses enter through the inferior peduncle. The reflex arc is
completed by fibers in the superior peduncle which pass to the red nucleus and the thalamus and
thence by additional neurons (rubrospinal tract) to the motor centers. The exact functions of its
different parts are still quite uncertain, owing to the contradictory nature of the evidence furnished
by (1) ablation experiments upon animals, and (2) clinical observations in man of the effects
produced by abscesses or tumors affecting different portions of the organ.
THE HIND-BRAIN OR RHOMBENCEPHALON 797
The Fourth Ventricle (ventriculus qiiarius) .—The fourth ventricle, or cavity
of the hind-brain, is situated in front of the cerebellum and behind the pons
and upper half of the medulla oblongata. Developmentally considered, the fourth
ventricle consists of three parts: a superior belonging to the isthmus rhombencephali,
an intermediate, to the metencephalon, and an inferior, to the myelencephalon.
It is lined by ciliated epithelium, and is continuous below with the central canal
of the medulla oblongata;^ above, it communicates, by means of a passage termed
the cerebral aqueduct, with the cavity of the third ventricle. It presents four
angles, and possesses a roof or dorsal wall, a floor or ventral wall, and lateral
boundaries.
Angles.— The superior angle is on a level with the upper border of the pons,
and is continuous Avith the lower end of the cerebral aqueduct. The inferior angle
is on a level with the lower end of the olive, and opens into the central canal of the
medulla oblongata. Each lateral angle corresponds with the point of meeting
of the brachia and inferior peduncle. A little below the lateral angles, on a level
with the strise medullares, the ventricular cavity is prolonged outward in the form
of two narrow lateral recesses, one on either side; these are situated between the
inferior peduncles andtheflocculi, and reach as far as the attachments of the glosso-
pharyngeal and vagus nerves.
Lateral Boundaries. — The lower part of each lateral boundary is constituted
by the clava, the fasciculus cuneatus, and the inferior peduncle; the upper part by
the middle and the superior peduncle.
Roof or Dorsal Wall (Fig. 708). — The upper portion of the roof is formed by
the superior peduncle and the anterior medullary velum; the lower portion,
by the posterior medullary velum, the epithelial lining of the ventricle covered
by the tela chorioidea inferior, the tsenise of the fourth ventricle, and the obex.
The superior peduncle (page 792), on emerging from the central white sub-
stance of the cerebellum, pass upward and forward, forming at first the lateral
boundaries of the upper part of the cavity; on approaching the inferior colliculi,
they converge, and their medial portions overlap the cavity and form part of its
roof.
The anterior medullary velum (page 79.3) fills in the angular interval between
the superior peduncle, and is continuous behind with the central white sub-
stance of the cerebellum; it is covered on its dorsal surface by the lingula of the
superior vermis.
The posterior medullary velum (page 794) is continued downward and forward
from the central white substance of the cerebellum in front of the nodule and
tonsils, and ends inferiorly in a thin, concave, somewhat ragged margin. Below
this margin the roof is devoid of nervous matter except in the immediate vicinity
of the lower lateral boundaries of the ventricle, where two narrow white bands, the
taeniae of the fourth ventricle (ligulw), appear; these bands meet over the inferior
angle of the ventricle in a thin triangular lamina, the obex. The non-nervous part
of the roof is formed by the epithelial lining of the ventricle, which is prolonged
downward as a thin membrane, from the deep surface of the posterior medullary
velum to the corresponding surface of the obex and taenise, and thence on to the
floor of the ventricular cavity; it is covered and strengthened by a portion of the
pia mater, which is named the tela chorioidea of the fourth ventricle.
The taeniae of the fourth ventricle {taenia ventriculi quarti; ligida) are two narrow
bands of white matter, one on either side, which complete the lower part of the roof
of the cavity. Each consists of a vertical and a horizontal part. The vertical part
is continuous below the obex with the clava, to which it is adherent by its lateral
' J. T. Wilson (Journal of Anatomy and Physiology, vol. xl) has pointed out that the central cana .of the medulla
oblongata, immediately below its entrance into the fourth ventricle, retains the cleft-like form presented by the fetal
medulla spinalis, and that it is marked by dorso- and ventro-lateral sulci.
798
NEUROLOGY
border. The horizontal portion extends transversely across the inferior peduncle,
below the striae medullares, and roofs in the lower and posterior part of the lateral
recess; it is attached b}' its lower margin to the inferior peduncle, and partly encloses
the choroid plexus, which, however, projects beyond it like a cluster of grapes; and
hence this part of the tnenia has been termed the cornucopia (Bochdalek) . The obex
is a thin, triangular, gray lamina, which roofs in the lower angle of the ventricle and
is attached by its lateral margins to the clavse. The tela chorioidea of the fourth
ventricle is the name applied to the triangular fold of pia mater which is carried
upward between the cerebellum and the medulla oblongata. It consists of two
layers, which are continuous with each other in front, and are more or less adherent
throughout. The posterior layer covers the antero-inferior surface of the cere-
bellum, while the anterior is applied to the structures which form the lower part
of the roof of the ventricle, and is continuous inferiorly with the pia mater on the
inferior peduncles and closed part of the medulla.
Corpora
guadrigcmina
Cerebral
'peduncle
Anterior
medullary
velum
Ependymal
lining of
ventricle
Posterior
medullary velum
Choroid plexus
Cisterna cerehellnmednllaris of
subarachnoid cavity
Central canal ma- .^v ^. • -.
Cisterna pontis of
subarachnoid cavity
Fig. 708. — Scheme of roof of fourth ventricle. The arrow is in the foramen of Majendie.
Choroid Plexuses. — These consist of two highly ^•ascular inflexions of the tela
chorioidea, which invaginate the lower part of the roof of the ventricle and are
everywhere covered by the epithelial lining of the cavity. Each consists of a ver-
tical and a horizontal portion : the former lies close to the middle line, and the latter
passes into the lateral recess and projects beyond its apex. The vertical parts of
the plexuses are distinct from each other, but the horizontal portions are joined
in the middle line; and hence the entire structure presents the form of the letter T,
the \'ertical limb of which, however, is double.
Openings in the Roof, — In the roof of the fourth ventricle there are three openings,
a medial and two lateral : the medial aperture {joravieji Majendii), is situated imme-
diately above the inferior angle of the ventricle; the lateral apertures, {foramina
of Luschka are found at the extremities of the lateral recesses. By means of these
three openings the ventricle communicates with the subarachnoid cavity, and the
cerebrospinal fluid can circulate from the one to the other.
Rhomboid Fossa {fossa rhomboidea; "floor" of the fourth ventricle) (Fig. 709). —
The anterior part of the fourtli ventricle is named, from its shape, the rhomboid
fossa, and its anterior wall, formed by the back of the pons and medulla oblongata,
constitutes the floor of the fourth ventricle. It is covered by a thin layer of gray
THE HIND-BRAIN OR RHOMBENCEPHALON
799
substance continuous with that of the medulla spinalis; superficial to this is a thin
lamina of neuroglia which constitutes the ependyma of the ventricle and supports
a layer of ciliated epithelium. The fossa consists of three parts, superior, inter-
mediate, and inferior. The superior part is triangular in shape and limited laterally
by the superior cerebellar peduncle; its apex, directed upward, is continuous with
the cerebral aqueduct; its base it represented by an imaginary line at the level of the
upper ends of the superior fovese. The intermediate part extends from this level
to that of the horizontal portions of the taeniae of the ventricle; it is narrow above
where it is limited laterally by the middle peduncle, but widens below and is pro-
longed into the lateral recesses of the ventricle. The inferior part is triangular,
and its downwardly directed apex, named the calamus scriptorius, is continuous
with the central canal of the closed part of the medulla oblongata.
T cent a pontis
Superior fovea
Collicvlus facialis
Striae medullares
Area acustica
Trigonum hjpoglossi
Ala cincrca
Tcenia of fourth ventricle
Frenulum veli
Trochlear nerve
Ant. medullary velum
Superior peduncle
Nux:leu3 dentatus
'Funiculus separans
^Area postrema
^Obex
' Clava
Fig. 709. — Rhomboid fossa.
The rhomboid fossa is divided into symmetrical halves by a median sulcus
which reaches from the upper to the lower angles of the fossa and is deeper below
than above. On either side of this sulcus is an elevation, the medial eminence,
bounded laterally by a sulcus, the sulcus limitans. In the superior part of the fossa
the medial eminence has a width equal to that of the corresponding half of the
fossa, but opposite the superior fovea it forms an elongated swelling, the colliculus
facialis, which overlies the nucleus of the abducent nerve, and is, in part at least,
produced by the ascending portion of the root of the facial nerve. In the inferior
part of the fossa the medial eminence assumes the form of a triangular area, the
trigonum hypoglossi. When examined under water with a lens this trigone is seen
to consist of a medial and a lateral area separated by a series of oblique furrows;
the medial area corresponds with the upper part of the nucleus of the hypoglossal
nerve, the lateral with a small nucleus, the nucleus intercalatus.
The sulcus limitans forms the lateral boundary of the medial eminence. In
the superior part of the rhomboid fossa it corresponds with the lateral limit of the
800
NEUROLOGY
fossa and presents a bluish-gray area, the locus cseruleus, which owes its color
to an underlying patch of deeply pigmented nerve cells, termed the substantia
ferruginea. At the level of the colliculus facialis the sulcus limitans widens into
a flattened depression, the superior fovea, and in the inferior part of the fossa appears
as a distinct dimple, the inferior fovea. Lateral to the fovese is a rounded elevation
named the area acustica, which extends into the lateral recess and there forms a
feebly marked swelling, the tuberculum acusticum. Winding around the inferior
peduncle and crossing the area acustica and the medial eminence are a number of
white strands, the striae medullares, which form a portion of the cochlear division of
the acoustic nerve and disappear into the median sulcus. Below the inferior fovea,
and between the trigonum hypoglossi and the lower part of the area acustica is a
triangular dark field, the ala cinerea, which corresponds to the sensory nucleus
of the vagus and glossopharyngeal nerves. The lower end of the ala cinerea is
crossed by a narrow translucent ridge, the funiculus separans, and between this
funiculus and the clava, is a small tongue-shaped area, the area postrema. On
section it is seen that the funiculus separans is formed by a strip of thickened
ependyma, and the area postrema by loose, highly vascular, neuroglial tissue con-
taining nerve cells of moderate size.
6..
THE MID-BRAIN OR MESENCEPHALON.
The mid-brain or mesencephalon (Fig. 681) is the short, constricted portion which
connects the pons and cerebellum with the thalamencephalon and cerebral hemi-
spheres. It is directed upward and for-
ward, and consists of (1) a ventro-
lateral portion, composed of a pair of
cvlindrical bodies, named the cerebral
peduncles; (2) a dorsal portion, consist-
ing of four rounded eminences, named
the corpora quadrigemina ; and (3) an
intervening passage or tunnel, the cere-
bral aqueduct, which represents the
original cavity of the mid-brain and
connects the third with the fourth ven-
tricle (Fig. 7101.
The cerebral peduncles {peduncidus
cerebri; crus cerebri) are two cylindrical
masses situated at the base of the brain,
and largely hidden by the temporal
lobes of the cerebrum, which must be
drawn aside or removed in order to
expose them. They emerge from the
upper surface of the pons, one on either
side of the middle line, and, diverging
as they pass upward and forward, dis-
appear into the substance of the cere-
bral hemispheres. The depressed area
between the crura is termed the inter-
peduncular fossa, and consists of a layer
of grayish substance, the posterior
perforated substance, which is pierced by small apertures for the transmission of
bloodvessels; its lower part lies on the ventral aspect of the medial portions of the
tegmenta, and contains a nucleus named the interpeduncular ganglion (page 802);
its upper part assists in forming the floor of the third ^•entricle. The ^•entral sur-
FiG. 710. — Coronal section through mid-brain. (Sche-
matic.) cTestut.) 1. Corpora quadrigemina. 2. Cere-
bral aqueduct. 3. Central gray stratum. 4. Interpedun-
cular space. 5. Sulcus lateralis, b. Substantia nigra. 7.
Red nucleus of tegmentum. 8. Oculomotor nerve, with S',
its nucleus of origin, a. Lemniscus (in blue) with a' the
medial lemniscus and a" the lateral lemniscus. 6.
Medial longitudinal fasciculus, c. Raph6. d. Temporo-
pontine fibers, e. Portion of medial lemniscus, which runs
to the lentiform nucleus and insula. /. Cerebrospinal
fibers, g. Frontopontine fibers.
THE MID-BRAIN OR MESENCEPHALON
801
face of each peduncle is crossed from the medial to the lateral side by the superior
cerebellar and posterior cerebral arteries; its lateral surface is in relation to the
gyrus hippocampi of the cerebral hemisphere and is crossed from behind forward
by the trochlear nerve. Close to the point of disappearance of the peduncle into
the cerebral hemisphere, the optic tract winds forward around its ventro-lateral
Inferior colliculi
Cerebral aquedtict
Nvcleus of oculomotor
nerve
Lateral lemniscus
Medial Innijitudinal
fasciculus
Medial lemniscus
Raphe
Fig. 711. — Transverse section of mid-brain at level of inferior colliculi.
surface. The medial surface of the peduncle forms the lateral boundary
of the interpeduncular fossa, and is marked by a longitudinal furrow, the oculo-
motor sulcus, from which the roots of the oculomotor nerve emerge. On the lateral
surface of each peduncle there is a second longitudinal furrow, termed the lateral
sulcus ; the fibers of the lateral lemniscus come to the surface in this sulcus, and
pass backward and iipward, to disappear under the inferior colliculus.
Superior colliculi
Cerebral aqueduct
Sucleus of oculomotor nerve
Medial longitudinal
fasciculus
FiQ. 712. — Transverse section of mid-brain at level of superior colliculi.
Structure of the Cerebral Peduncles (Figs. 711, 712). — On transverse section, each
peduncle is seen to consist of a dorsal and a ventral part, separated by a deeply
pigmented lamina of gray substance, termed the substantia nigra. The dorsal part
51
802 NEUROLOGY
is named the tegmentum; the ventral, the base or crusta; the two bases are separated
from each other, but the tegmenta are joined in the median plane by a forward
prolongation of the raphe of the pons. Laterally, the tegmenta are free; dorsally,
they blend with the corpora quadrigemina.
The base {basis pedunculi; crusta or pes) is semilunar on transverse section, and
consists almost entirely of longitudinal bundles of efferent fibers, which arise from
the cells of the cerebral cortex and are grouped into three principal sets, viz.,
cerebrospinal, frontopontine, and temporopontine (Fig. 710). The cerebrospinal
fibers, derived from the cells of the motor area of the cerebral cortex, occupy
the middle three-fifths of the base; they are continued partly to the nuclei of the
motor cranial nerves, but mainly into the pyramids of the medulla oblongata.
The frontopontine fibers are situated in the medial fifth of the base; they arise from
the cells of the frontal lobe and end in the nuclei of the pons. The temporopontine
fibers are lateral to the cerebrospinal fibers; they originate in the temporal lobe
and end in the nuclei pontis.^
The substantia nigra (intercalatum) is a layer of gray substance containing
numerous deeply pigmented, multipolar nerve cells. It is semilunar on transverse
section, its concavity being directed toward the tegmentum; from its convexity,
prolongations extend between the fibers of the base of the peduncle. Thicker
medially than laterally, it reaches from the oculomotor sulcus to the lateral sulcus,
and extends from the upper surface of the pons to the subthalamic region; its
medial part is traversed by the fibers of the oculomotor nerve as these stream for-
ward to reach the oculomotor sulcus. The connections of the cells of the substantia
nigra have not been definitely established. It receives collaterals from the medial
lemniscus and the p\Tamidal bundles. Bechterew is of the opinion that the fibers
from the motor area of the cerebral cortex form synapses with cells whose axons
pass to the motor nucleus of the trigeminal nerve and serve for the coordination
of the muscles of mastication.
The tegmentum is continuous below with the reticular formation of the pons,
and, like it, consists of longitudinal and transverse fibers, together with a consider-
able amount of gray substance. The principal gray masses of the tegmentum
are the red nucleus and the interpeduncular ganglion; of its fibers the chief longi-
tudinal tracts are the superior peduncle, the medial longitudinal fasciculus, and
the lemniscus.
Gray Substance. — The red nucleus is situated in the anterior part of the teg-
mentum, and is continued upward into the posterior part of the subthalamic region.
In sections at the level of the superior colliculus it appears as a circular mass
which is traversed by the fibers of the oculomotor nerve. It receives many terminals
and collaterals from the superior cerebellar peduncle also collaterals from the
ventral longitudinal bundle, from Gudden's bimdle and the median lemniscus.
The axons of its larger cells cross the middle line and are continued do^^^lward
into the lateral funiculus of the medulla spinalis as the rubrospinal tract (page 761);
those of its smaller cells end mainly in the thalamus. The rubrospinal tract forms
an unportant part of the pathway from the cerebellum to the lower motor centers.
The interpeduncular ganglion is a median collection of nerve cells situated in
the ventral part of the tegmentum. The fibers of the fasciculus retroflexus of
Meynert, which have their origin in the cells of the ganglion habenulse (page 812),
end in it.
Besides the two nuclei mentioned, there are small collections of cells which
form the dorsal and ventral nuclei and the central nucleus or nucleus of the raphe.
' A band of fibers, the Iractus peduncvlaris IraiisverSus, is sometimes seen emerging from in front of the superior collic-
ulus; it passes around the ventral aspect of the peduncle about midway between the pons and the optic tract, and
dijps into the oculomotor sulcus. This band is a constant structure in many mammals, but is only present in about
30 per cent, of human brains. Since it undergoes atrophy after enucleation of the eyeballs, it may be considered as
forming a path for visual sensations.
THE MID-BRAIN OR MESENCEPHALON 803
White Substance. — (1) The origin and course of the superior peduncle have
already been described (page 792).
(2) The medial {posterior) longitudinal fasciculus is continuous below with the
proper fasciculi of the anterior and lateral funiculi of the medulla spinalis. In
the medulla oblongata and pons it runs close to the middle line, near the floor
of the fourth ventricle; in the mid-brain it is situated on the ventral aspect
of the cerebral aqueduct, below the nuclei of the oculomotor and trochlear
nerves. Its connections are imperfectly known, but it consists largely of ascend-
ing and descending intersegmental or association fibers, which connect the
nuclei of the hind-brain and mid-brain to each other. Many of the fibers arise
in Deiters's nucleus (lateral vestibular imclevs) and divide into ascending and descend-
ing branches which send terminals and collaterals to the motor nuclei of the cranial
and spinal nerves. Its spinal portion is located in the anterior funiculus and is
kno^^^l as the vestibulospinal fasciculus. Other fibers pass to the median longitudinal
bundle from cells in the reticular formation of the medulla, pons and mid-brain
and also from certain large cells in the terminal nucleus of the trigeminal nerve.
According to Edinger it extends to the so-called nucleus of the posterior longi-
tudinal bundle in the hypothalamic region, but this is uncertain and the fibers
above the nucleus of the oculomotor are smaller in diameter than the rest of the
bundle. According to Held fibers from the posterior commissure can be traced
into the posterior longitudinal bundle, and according to the same author many
of the descending fibers arise in the superior colliculus, and, after decussating in
the middle line, end in the motor nuclei of the pons and medulla oblongata. These
fibers from the superior colliculus probably pass into the ventral longitudinal
bundle. Fibers are said to pass through the medial longitudinal fasciculus from the
nucleus of the abducent nerve into the oculomotor nerve of the opposite side, and
through this nerve to the Rectus medialis oculi. Fraser, however, denies the exist-
ence of such fibers. Again, fibers are said to be prolonged through this fasciculus
from the nucleus of the oculomotor nerve into the facial nerve, and are distributed
to the Orbicularis oculi, the Corrugator, and the Frontalis.^
The ventral longitudinal bundle consists for the most part of the tectospinal fas-
ciculus, and arises from the superior colliculus, the fibers arcli ventrally around the
central gray matter and cross the midline in the fountain-decussation of Meynert.
They then descend in the tegmentum, part of them passing through the red nucleus
ventral to the medial longitudinal bundle. In the medulla oblongata and spinal
cord its fibers are more or less intermingled with the medial longitudinal bundle
and the rubrospinal tract. It descends in the adjoining region of the ventral
and lateral funiculi. Collaterals and terminals are given oft' to the red nucleus and
probably other nuclei of the brain stem and to the anterior column of the spinal
cord. It is probably concerned in optic reflexes.
(3) The medial lemniscus or medial fillet (Fig. 713). — The fibers of the medial
lemniscus take origin in the gracile and cuneate nuclei of the medulla oblongata,
and as internal arcuate fibers they cross to the opposite side in the sensory decussa-
tion (page 777). They then pass in the interoli^'ary stratum upward through
the medulla oblongata, in which they are situated behind the cerebrospinal fibers
and between the olives. In the pons and lower part of the mid-brain it occupies
the ventral part of the reticular formation and tegmentum close to the raphe, while
above it gradually shifts to the dorso-lateral part of ths tegmentum in the angle
between the red nucleus and the substantia nigra. In the pons it assumes a flattened
ribbon-like appearance, and is placed dorsal to the trapezium. As the lemniscus
ascends, it receives additional fibers from the terminal sensory nuclei of the'^-raiiial
• » A. Bruce and J. H. Harvey Pirrie, "On the Origin of the Facial Nerve," Review of Neurology and Psychiatry.
December, 1908, No. 12, vol. vi, produce weighty evidence against the view that the facial nerve derives fibers from
the nucleus of the oculomotor nerve.
804
NEUROLOGY
nerves of the opposite side. Many of the fibers which arise from the terminal
sensor\' nuclei of the cranial nerves pass upward in the formatio reticularis as a
separate bundle, kno^^^l as the central tract of the cranial nerves, to the thalamus.
]\Iany fibers either terminate in or send off collaterals to the gray matter of the
medulla, the pons, and the mid-brain. Large numbers of fibers pass to or from the
substantia nigra. Many collaterals enter the red nucleus and other fibers are said
to run to the superior colliculus. The great bulk of the fibers, however, enter the
ventro-lateral portion of the thalamus, give off collaterals to the posterior semi-
lunar nucleus and then terminate in the principal sensory nucleus of the thalamus.
Cor'pora
quadrigemina
Superior olivary
nticleus
Cochlear nucleus
Sensory cerebral miclei
Nucleus gracilis
Nucleus cuneatus
Fig. 713. — Scheme showing the course of the fibers of the lemniscus; medial lemniscus in blue, lateral in red.
In the cerebral peduncle, a few of its fibers pass upward in the lateral part
of the base of the peduncle, on the dorsal aspect of the temporopontine fibers,
and reach the lentiform nucleus and the insula. The greater part of the medial
lemniscus, on the other hand, is prolonged through the tegmentum, and most
of its fibers end in the thalamus; probably some are continued dipectly through
the occipital part of the internal capsule to the cerebral cortex. From the cells of
the thalamus a relay of fibers is prolonged to the cerebral cortex.
The medial lemniscus may be considered as the upward continuation of the
posterior funiculus of the spinal cord and to convey conscious impulses of muscle
sense and tactile discrimination.
THE MID-BRAIN OR MESENCEPHALON
805
6 2
The central or thalamic tract of the cranial nerves is (■los(>ly associated with the
me(hal lemniscus. The iibers of tlie spinotiialainic fascicuH are continued from the
spinal cord into this tract which passes upward in the reticular formation and the
tegmentum to the thalamus along the dorsal side of the median lemniscus. It
receives fibers from the opposite terminal sensory nuclei of the vagus, glossopharyn-
geal, facial, trigeminal and probably the vestibular ner\es. Many of the secondary
sensory fibers of the trigeminal cross the raphe from its terminal nucleus and pass
upward to the thalamus by a more or less separate but closely associated pathway
kno^^^l as the central tract of the trigeminal nerve
which also lies on the dorsal aspect of the lemni.s-
cus. These two tracts give off collaterals to the
posterior semilunar nucleus of the thalamus and
terminate in the anterior semilunar nucleus of
the ventro-lateral region of the thalamus sending
collaterals into the zona incerta.
The fibers of the rubrospinal tract (bundle of
Monakow) arise in the red nucleus, cross the
midline in the decussation of Forel and pass
downward in the f ormatio reticularis of the brain-
stem into the lateral funiculus of the spinal cord
ventral to the crossed pyramidal tract.
The lateral lemniscus (lemniscus lateralis)
comes to the surface of the mid-brain along
its lateral sulcus, and disappears under the
inferior colliculus. It consists of fibers from
the terminal nuclei of the cochlear division
of the acoustic nerve, together with others from
the superior olivary and trapezoid nuclei. ]\Iost
of these fibers are crossed, but some are uncrossed. INIany of them pass to the
inferior colliculus of the same or opposite side, but others^ are prolonged to
the thalamus, and thence through the occipital part of the internal capsule to
the middle and superior temporal gyri.
The corpora quadrigemina (Fig. 720) are four rounded eminences which form
the dorsal part of the mid-braJn. They are situated above and in front of
the anterior medullary velum and superior peduncle, and below and behind the
third ventricle and posterior commissure. They are covered by the splenium of the
corpus callosum, and are partly overlapped on either side by the medial angle,
or pulvmar, of the posterior end of the thalamus; on the lateral aspect, under
cover of the pulvinar, is an oval eminence, named the medial geniculate body.
The corpora quadrigemina are arranged in pairs (superior and inferior coUiculi),
and are separated from one another by a crucial sulcus. The longitudinal part
of this sulcus expands superiorly to form a slight depression which supports the
pineal body, a cone-like structure which projects backward from the thalam-
encephalon and partly obscures the superior colliculi. From the inferior end of
the longitudinal sulcus, a white band, termed the frenulum veli, is prolonged down-
ward to the anterior medullary velum; on either side of this band the trochlear
nerve emerges, and passes forward on the lateral aspect of the cerebral peduncle
to reach the base of the brain. The superior coUicuU are larger and darker in color
than the inferior, and are oval in shape. The inferior colliculi are hemispherical,
and somewhat more prominent than the superior. The superior colliculi are
associated with the sense of sight, the inferior with that of hearing.
From the lateral aspect of each colliculus a white band, termed the brachium,
is prolonged upward and forward. The superior brachium extends lateralward
from the superior colliculus, and, passing between the pulvinar and medial genicu-
Fig. 714. — Transverse section passing through
the sensory decussation. Schematic. (Testut.)
1. Anterior median fissure. 2. Posterior median
sulcus. 3,3'. Head and base of anterior column
(in red). 4. Hypoglossal nerve. 5. Bases of
posterior column. 6. Gracile nucleus. 7. Cune-
ate nucleus. 8, 8. Lemniscus. 9. Sensory
decussation. 10. Cerebrospinal fasciculus.
806 NEUROLOGY
late body, is partly continued into an eminence called the lateral geniculate body,
and partly into the optic tract. The inferior brachium passes forward and upward
from the inferior colliculus and disappears under co\'er of the medial geniculate body.
In close relationship with the corpora quadrigemina are the superior peduncles,
which emerge from the upper and medial parts of the cerebellar hemispheres.
They run upward and forward, and, passing under the inferior colliculi, enter the
tegmenta as already described (page 792).
Structure of the Corpora Quadrigemina. — The inferior colliculus (colliculus inferior;
inferior quadrigeminal body; postgemina) consists of a compact nucleus of gray
substance containing large and small multipolar nerve cells, and more or less
completely surrounded by white fibers derived from the lateral lemniscus.
Most of these fibers end in the gray nucleus of the same side, but some cross the
middle line and end in that of the opposite side. From the cells of the gray
nucleus, fibers are prolonged through the inferior brachium into the tegmentum
of the cerebral peduncle, and are carried to the thalamus and the cortex of the
temporal lobe; other fibers cross the middle line and end in the opposite colliculus.
The superior colliculus {colliculus superior; superior quadrigeminal body;
pregemina) is covered by a thin stratum (stratum zonale) of white fibers,
the majority of which are derived from the optic tract. Beneath this is the
stratum cinereum, a cap-like layer of gray substance, thicker in the center than
at the circumference, and consisting of numerous small multipolar nerve cells,
imbedded in a fine network of nerve fibers. Still deeper is the stratum opticum,
containing large multipolar nerve cells, separated by numerous fine nerve fibers.
Finally, there is the stratum lemnisci, consisting of fibers derived partly from the
lemniscus and partly from the cells of the stratum opticum; interspersed among
these fibers are many large multipolar nerve cells. The two last-named strata
are sometimes termed the gray-white layers, from the fact that they consist of both
gray and white substance. Of the afl'erent fibers which reach the superior colliculus,
some are derived from the lemniscus, but the majority have their origins in the
retina and are conveyed to it through the superior brachium; all of them end by
arborizing around the cells of the gray substance. Of the efferent fibers, some
cross the middle line to the opposite colliculus; many ascend through the superior
brachium, and finally reach the cortex of the occipital lobe of the cerebrum; while
others, after undergoing decussation (fountain decussation of Meynert) form the
tectospinal fasciculus which descends through the formatio reticularis of the mid-
brain, pons, and medulla oblongata into the medulla spinalis, where it is found
partly in the anterior funiculus and partly intermingled with the fibers of the
rubrospinal tract.
The corpora quadrigemina are larger in the lower animals than in man. In
fishes, reptiles, and birds they are hollow, and only two in nimiber (corpora
bigemina); they represent the superior colliculi of mammals, and are frequently
termed the optic lobes, because of their intimate connection with the optic tracts.
The cerebral aqueduct {aqueductus cerebri; aqueduct of Sylvius) is a narrow
canal, about 15 mm. long, situated between the corpora quadrigemina and teg-
menta, and connecting the third with the fourth ventricle. Its shape, as seen in
transverse section, varies at different levels, being T-shaped, triangular above,
and oval in the middle; the central part is slightly dilated, and was named by
Retzius the ventricle of the mid-brain. It is lined by ciliated columnar epithelium,
and is surrounded by a layer of gray substance named the central gray stratum:
this is continuous below with the gray substance in the rhomboid fossa, and above
with that of the third ventricle. Dorsally, it is partly separated from the gray
substance of the quadrigeminal bodies by the fibers of the lemniscus; ventral to
it are the medial longitudinal fasciculus, and the formatio reticularis of the teg-
mentum. Scattered throughout the central gray stratum are numerous nerve
THE FORE-BRAIN OR PROSENCEPHALON
807
cells of various sizes, interlaced, by a net-work of fine fibers. Besides these scattered
cells it contains three groups which constitute the nuclei of the oculomotor and
trochlear nerves, and the nucleus of the mesencephalic root of the trigeminal nerve.
The nucleus of the trigeminal nerve extends along the entire length of the aqueduct,
and occupies the lateral part of the gray stratum, while the nuclei of the oculo-
motor and trochlear nerves are situated in its ventral part. The nucleus of the
oculomotor nerve is about 10 cm. long, and lies under the superior colliculus, beyond
which, however, it extends for a short distance into the gray substance of the third
ventricle. The nucleus of the trochlear nerve is small and nearly circular, and is on
a level with a plane carried transversely through the upper part of the inferior
colliculus.
THE FORE-BRAIN OR PROSENCEPHALON.
The fore-brain or prosencephalon consists of: (1) the diencephalon, corresponding
in a large measure to the third ventricle and the structures which bound it; and
(2) the telencephalon, comprising the largest part of the brain, viz., the cerebral
hemispheres; these hemispheres are intimately connected with each other across
the middle line, and each contains a large cavity, named the lateral ventricle.
The lateral ventricles communicate through the interventricular foramen with the
third ventricle, but are separated from each other by a medial septum, the septum
pellucidum; this contains a slit-like cavity, which does not communicate with the
ventricles.
rORAMEN OF MONRO
MIDDLE COMMISSURE
LEXUS OF
TRICLE
lA THALAMI
HABENULAR
COMMISSURE
POSTERIOR
MMISSURC
ROSTRUM
COPULA
ANTERIOR /
COMMISSURE ^
LAMINA TERMINALIS
OPTIC CHIASM
OPTIC / -^
LOMOTOR
E
CORPUS ALBICANS
TUBER CINEREUM
QUADRIGEMlNAl
LAMINA
AQUEDUCT
X.SUP. MEDULLARY
VELUM
FOURTH
VENTRICLE
Fig. 715. — Mesal aspect of a brain sectioned in the median sagittal plane.
The Diencephalon. — The diencephalon is connected above and in front with
the cerebral hemispheres; behind with the mid-brain. Its upper surface is con-
cealed by the corpus callosum, and is covered by a fold of pia mater, named the
tela chorioidea of the third ventricle; inferiorlv it reaches to the base of the brain.
The diencephalon comprises: (1) the thalamencephalon; (2) the pars mamillaris
808
NEUROLOGY
hypothalami ; and (3) the posterior part of the third ventricle. For descriptive purposes,
however, it is more convenient to consider the whole of the third ventricle and its
boundaries together; this necessitates the inclusion, under this heading, of the pars
optica hypothalami and the corresponding part of the third ventricle — structures
which properly belong to the telencephalon.
The Thalamencephalon. — The thalamencephalon comprises: (1) the thalamus;
(2) the metathalamus or corpora geniculata; and (3) the epithalamus, consisting of
the trigonum habenulje, the pineal body, and the posterior commissure.
Fig. 716. — Dissection showing the ventricles of the brain.
The Thalami {optic thalamus) (Figs. 71G, 717) are two large ovoid masses, situated
one on either side of the third ^•entricle and reaching for some distance behind that
cavity. Each measures about 4 cm. in length, and presents two extremities, an
anterior and a posterior, and four surfaces, superior, inferior, medial, and lateral.
The anterior extremity is narrow; it lies close to the middle line and forms the
posterior boinidary of the interventricular foramen.
The posterior extremity is expanded, directed backward and lateralward, and
overlaps the superior colliculus. INIedially it presents an angular prominence,
the pulvinar, which is continued laterally into an oval swelling, the lateral geniculate
body, while beneath the pulvinar, but separated from it by the superior brachium,
is a second oxaX swelling, the medial geniculate body.
The superior surface is free, slightly convex, and covered by a layer of white
substance, termed the stratum zonale. It is separated laterally from the caudate
nucleus by a white band, the stria terminalis, and by the terminal vein. It is divided
into a medial and a lateral portion by an oblique shallow furrow which runs from
behind forward and medialward and corresponds with the lateral margin of the
fornix; the lateral part forms a j^ortion of the floor of the lateral ventricle, and is
THE FORE-BRAIN OR PROSENCEPHALON
809
covered by the epithelial lining of this ca^-ity; the medial part is covered by the
tela chorioidea of the third ventricle, and is destitute of an epithelial covering.
In front, the superior is separated from the medial surface by a salient margin,
the taenia thalami, along which the epithelial lining of the third ventricle is reflected
on to the under surface of the tela chorioidea. Behind, it is limited medially by
a groove, the sulcus habenulae, which intervenes between it and a small triangular
area, termed the trigonum habenulae.
The inferior surface rests upon and is continuous with the upward prolongation
of the tegmentum (subthalamic tegmental region), in front of which it is related to
the substantia innominata of Mejmert.
TluUamus
Lateral ventricle
Caudate ntu:leus
Internal capsule
Lentiform nucleus
Clavfitrum
Insula
Corpus callosum
Choroid plexua of
lateral ventricle
Fornix
Choroid plexus of
third ventricle
Third ventricle
Red nucleus
Substantia nigra
Post. perf. substance
Base of peduncle
Kiicleus of Lut/s
Tcenia hippocampi
Inferior curnu of lateral ventricle
Hippocampus
Caudate nucleus
FiQ. 71T
Gyrus dentatxts
-Coronal section of brain immediately in front of pons.
The medial surface constitutes the upper part of the lateral wall of the third
ventricle, and is connected to the corresponding surface of the opposite thalamus
by a flattened gray band, the massa intermedia (middle or gray commissure). This
mass averages about 1 cm. in its antero-posterior diameter: it sometimes consists
of two parts and occasionally is absent. It contains nerve cells and nerve fibers;
a few of the latter may cross the middle line, but most of them pass toward the
middle line and then curve lateralward on the same side.
The lateral surface is in contact with a thick band of white substance which
forms the occipital part of the internal capsule and separates the thalamus from
the lentiform nucleus of the corpus striatum.
810
NEUROLOGY
Structure. — The thalamus consists chiefly of gray substance, but its upper sur-
face is covered by a layer of white substance, named the stratiun zonale, and its
lateral- surface by a similar layer termed the lateral medullary lamina. Its gray
substance is incompletely subdivided into three parts — anterior, medial, and lateral
— by a white layer, the medial medullary lamina. The anterior part comprises the
anterior tubercle, the medial part lies next the lateral wall of the third ventricle
while the lateral and largest part is interposed between the medullary laminae
and includes the pulvinar. The lateral part is traversed by numerous fibers which
radiate from the thalamus into the internal capsule, and pass through the latter
to the cerebral cortex. These three parts are built up of numerous nuclei, the
connections of many of which are imperfectly known.
Thalamus
Caudate nucleus
Internal capsule
Globus pallidus
Putamen
Claustrum
Insula
Corpus callosum
Lateral ventricle
Choroid plexus
Fornix
Third ventricle
Medial medullary lamina
Intennediate mass
Third ventricle
Optic tract — -^
Amygdaloid nucleus
Fig. 718. — Coronal section of brain through intermediate mass of third ventricle.
Connections. — The thalamus may be regarded as a large ganglionic mass in which
the ascending tracts of the tegmentum and a considerable proportion of the fibers
of the optic tract end, and from the cells of which numerous fibers (thalamocortical)
take origin, and radiate to almost every part of the cerebral cortex. The lemniscus,
together with the other longitudinal strands of the tegmentum, enters its ventral
part: the thalamomammillary fasciculus {bundle of Vicq d'Azyr), from the corpus
mammillare, enters in its anterior tubercle, while many of the fibers of the optic
tract terminate in its posterior end. The thalamus also receives numerous fibers
(corticothalamic) from the cells of the cerebral cortex. • The fibers that arise from
THE FORE-BRAIN OR PROSENCEPHALON
811
the cells of the thalamus form four principal groups or stalks: (a) those of the ante-
rior stalk pass through the frontal part of the internal capsule to the frontal lobe;
(6) the fibers of the posterior stalk {optic radiations) arise in the pulvinar and are
conveyed through the occipital part of the internal capsule to the occipital lobe; (c)
the fibers of the inferior stalk leave the under and medial surfaces of the thalamus,
and pass beneath the lentiform nucleus to the temporal lobe and insula; (d) those
of the parietal stalk pass from the lateral nucleus of the thalamus to the parietal
lobe. Fibers also extend from the thalamus into the corpus striatum — those
destined for the caudate nucleus leave the lateral surface, and those for the lenti-
form nucleus, the inferior surface of the thalamus.
Superior brachium Lateral geniculate body
Inferior bra^hium / / Hedial geniculate body
P^ilviiiar
Pineatbody \ (|" I
Optic tract
Superior collicuU-
Inferior colliai i i_
Frenulum veli ^mJJMBb,
Trochlear nerve
Lateral lemniscus
Superior peduncle
Middle peduncle
lihumboid J'oisa
Clava
Glossopharyngeal and vagus nerves ^ \
Optic commissure
Oculomotor nerve
Trigeminal nerve
Afpustic nerve
Facial nerce
Abducent nerve
Hypoglossal nerve
Accessory nerve
Fig. 719. — Hind- and mid-brains; postero-lateral view.
The "Metathalamus (Fig. 719) comprises the geniculate bodies, which are two in
number — a medial and a lateral — on each side.
The medial geniculate body {corpus geniculatum mecliale; internal geniculate body;
postgeniculatum) lies under cover of the pulvinar of the thalamus and on the lateral
aspect of the corpora quadrigemina. Oval in shape, with its long axis directed
forward and lateralward, it is lighter in color and smaller in size than the lateral.
The inferior brachium from the inferior colliculus disappears under cover of it
while from its lateral extremity a strand of fibers passes to join the optic tract.
Entering it are many acoustic fibers from the lateral lemniscus. The medial
geniculate bodies are connected with one another by the commissure of Gudden,
which passes through the posterior part of the optic chiasma.
The lateral geniculate body {corpus geniculatum laterale; external geniculate body;
pregeniculatum) is an oval elevation on the lateral part of the posterior end of the
thalamus, and is connected with the superior colliculus by the superior brachium.
It is of a dark color, and presents a laminated arrangement consisting of alternate
layers of gray and white substance. It receives numerous fibers from the optic
tract, while other fibers of this tract pass over or through it into the pulvinar.
Its cells are large and pigmented j their axons pass to the visual area in the occipital
part of the cerebral cortex.
812 NEUROLOGY
The superior colliculus, the piilvinar, and the lateral geniculate body receive
many fibers from the optic tracts, and are therefore intimately connected with
sight, constituting what are termed the lower visual centers. Extirpation of the
eyes in a new^ly born animal entails an arrest of the development of these centers,
but has no effect on the medial geniculate bodies or on the inferior colliculi. More-
over, the latter are well-developed in the mole, an animal in which the superior
colliculi are rudimentary.
The Epithalamus comprises the trigonum habenulse, the pineal body, and the
posterior commissure.
The trigonum habenulae is a small depressed triangular area situated in front
of the superior colliculus and on the lateral aspect of the posterior part of the taenia
thalami. It contains a group of nerve cells termed the ganglion habenulse. Fibers
enter it from the stalk of the pineal body, and others, forming what is termed the
habenular commissure, pass across the middle line to the corresponding ganglion
of the opposite side. Most of its fibers are, however, directed dow^nward and form
a bundle, the fasciculus retroflexus of Meynert, which passes medial to the red
nucleus, and, after decussating with the corresponding fasciculus of the opposite
side, ends in the interpeduncular ganglion.
The pineal body (corpus lyineale; epiphysis) is a small, conical, reddish-gray body
which lies in the depression between the superior colliculi. It is placed beneath the
splenium of the corpus callosum, but is separated from this by the tela chorioidea
of the third ventricle, the lower layer of which envelops it. It measures about
8 mm. in length, and its base, directed forAvard, is attached by a stalk or peduncle
of white substance. The stalk of the pineal body divides anteriorly into two
laminae, a dorsal and a ventral, separated from one another by the pineal recess
of the third ventricle. The ventral lamina is continuous with the posterior com-
missure; the dorsal lamina is continuous with the habenular commissure and
divides into two strands the medullary striae, which run forward, one on either
side, along the junction of the medial and upper surfaces of the thalamus to blend
in front with the columns of the fornix.
The posterior commissure is a rounded band of white fibers crossing the middle
line on the dorsal aspect of the upper end of the cerebral aqueduct. Its fibers
acquire their medullary sheaths early, but their connections have not been definitely
determined. INIost of them have their origin in a nucleus, the nucleus of the poste-
rior commissure {nucleus of Darkscheivitsch) , which lies in the central gray substance
of the upper end of the cerebral aqueduct, in front of the nucleus of the oculomotor
nerve. Some are probably derived from the posterior part of the thalamus and from
the superior colliculus, while others are beheved to be continued downward into
the medial longitudinal fasciculus.
The Hypothalamus (Fig. 720) includes the subthalamic tegmental region and
the structures forming the greater part of the floor of the third ventricle, viz., the
corpora mammillaria, tuber cinereum, infundibulum, hypophysis, and optic chiasma.
The subthalamic tegmental region consists of the upward continuation of the
tegmentum; it lies on the ventro-lateral aspect of the thalamus and separates
, it from the fibers of the internal capsule. The red nucleus and the substantia
nigra are prolonged into its lower part; in front it is continuous with the substantia
innominata of Meynert, medially with the gray substance of the floor of the third
ventricle.
It consists from above downward of three strata: (1) stratum dorsale, directly
applied to the under surface of the thalamus and consisting of fine longitudinal
fibers; (2) zona incerta, a continuation forward of the formatio reticularis of the
tegmentum; and (3) the corpus subthalamicum (nucleus of Luys), a brownish mass
presenting a lenticular shape on transverse section, and situated on the dorsal
aspect of the fibers of the base of the cerebral peduncle; it is encapsuled by a lamina
THE FORE-BRAIN OR PROSENCEPHALON
813
of nerve fibers and contains numerous medium-sized nerve cells, the connections
of which are as yet not fully determined.
The corpora mammillaria {corpus albicantia) are two round white masses, each
about the size of a small pea, placed side by side below the gray substance of the
floor of the third ventricle in front of the posterior perforated substance. They
consist of white substance externally and of gray substance internally, the cells of
the latter forming two nuclei, a medial of smaller and a lateral of larger cells. The
white substance is mainly formed by the fibers of the columns of the fornix, which
descend to the base of the brain and end partly in the corpora mammillaria. From
the cells of the gray substance of each mammillary body two fasciculi arise: one,
the thalamomammillary fasciculus {bundle of^ Vicq d'Azyr), passes upward into the
anterior nucleus of the thalamus; the other is directed downward into the tegmen-
tum. Afferent fibers are believed to reach the corpus mammillare from the medial
lemniscus and from the tegmentum.
Tela chorioidea of third venh-ide Posterior eommisHUr/>
Intermediate mass
Interventricular foramen.
Corpora 'juaJriijemina
Pineal body
Splenium
Pia water
Genu /
Rostrum
Anterior commissure /
Lamina terminalis /
Optic recess
Optic chiasma /
Infundibulum
Corpus mamillare
Oeulomotw nerre
Cerebral aqueduct
Fig. 720. — Median sagittal section of brain.
Choroid plexus
Fourth ventricle
The relations of the pia mater are indicated by the red color.
The tuber cinereum is a hollow eminence of gray substance situated between
the corpora mammillaria behind, and the optic chiasma in front. Laterally it is
continuous with the anterior perforated substances and anteriorly with a thin
lamina, the lamina terminalis. From the under surface of the tuber cinereum a
hollow conical process, the infundibulum, projects downward and forward and is
attached to the posterior lobe of the hypophysis.
In the lateral part of the tuber cinereum is a nucleus of nerve cells, the basal optic nucleus
of Meynert, while close to the cavity of the third ventricle are three additional nuclei. Between
the tuber cinereum and the corpora mammillaria a small elevation, with a corresponding de-
pression in the third ventricle, is sometimes seen. Retzius has named it the eminentia sacculahs,
and regards it as a representative of the saccus vasculosus found in this situation in some of
the lower vertebrates.
814
NEUROLOGY
The hypophysis {pituitary body) (Fig. 721) is a reddish-gray, somewhat oval
mass, measuring about 12.5 mm. in its transverse, and about 8 mm. in its antero-
posterior diameter. It is attached to the end of the infundibulum, and is situated
in the fossa hypophyseos.of the sphenoidal bone, where it is retained by a circular
fold of dura mater, the diaphragma sella; tliis fold almost completely roofs in the
fossa, leaving only a small central aperture through which the infundibulum passes.
Lamina
terminalis
Anterior Optic
commissure recess
.-/x-^.
Ant. cerebral artery.
Optic chiasma.
%f^ ^Jnfundibulum
.■Circular sinus
'.Cerebral peduncle
Corpus mammillare
Post, cerebral artery
s::;^Sr Basilar artery
Pons
Anterior lobe,.-^
of hypophysis d , ■ 7 k
Posterior lobe
Fig. 721. — The hypophysis cerebri, in position. Shown in sagittal section.
Optic Chiasma {chia.svia opticum; optic commissure). — The optic chiasma is a
flattened, somewhat quadrilateral band of fibers, situated at the junction of the
floor and anterior wall of the third ventricle. INIost of its fibers have their origins
in the retina, and reach the chiasma through the opticnerves, which are continuous
with its antero-lateral angles. In the chiasma, they undergo a partial decussation
(Fig. 722) ; the fibers from the nasal half of the retina decussate and enter the optic
tract of the opposite side, while the fibers from the temporal half of the retina do
not undergo decussation, but pass back into the optic tract of the same side.
Occupying the posterior part of the commissure, however, is a strand of fibers,
the commissure of Gudden, which is not derived from the optic nerves; it forms a
connecting link between the medial geniculate bodies.
Optic Tracts. — The optic tracts are continued backward and lateralward from
the postero-lateral angles of the optic chiasma. Each passes between the anterior
perforated substance and the tuber cinereum, and, winding around the ventro-
lateral aspect of the cerebral peduncle, divides into a medial and a lateral root.
The former comprises the fibers of Gudden's commissure. The lateral root consists
mainly of afferent fibers which arise in the retina and undergo partial decussation
in the optic chiasma, as described; but it also contains a few fine efferent fibers
which have their origins in the brain and their terminations in the retina, ^yhen
traced backward, the afferent fibers of the lateral root are found to end in the lateral
geniculate body and pulvinar of the thalamus, and in the superior colliculus; and
these three structures constitute the lower visual centers. Fibers arise from the
nerve cells in these centers and pass through the occipital part of the internal
capsule, under the name of the optic radiations, to the cortex of the occipital lobe
of the cerebrum, where the higher or cortical visual center is situated. Some of the
fibers of the optic radiations take an opposite course, arising from the cells of the
occipital cortex and passing to the lower visual centers. Some fibers are detached
from the optic tract, and pass through the cerebral peduncle to the nucleus of
the oculomotor nerve. These may be regarded as the afferent branches for the
THE FORE-BRAIN OR PROSENCEPHALON
815
Sphincter pupillse and Ciliaris muscles. Other fibers have been described as
reaching the cerebellum through the superior peduncle; while others, again, are
lost in the pons.
The Third Ventricle {ventriculus tertius) (Figs. 716, 720).— The third ventricle is
a median cleft between the two thalami. Behind, it communicates with the fourth
ventricle through the cerebral aqueduct, and in front with the lateral ventricles
through the interventricular foramen. Somewhat triangular in shape, with the
apex directed backward, it has a roof, a floor, an anterior and a posterior boundary
and a pair of lateral walls.
- Optic nerve
Crossed fibers
Uncrossed fibers
Optic chiasma
Optic tract
Commissure of Chidden
Pulvinar
Lateral geniculate body
-Superior colliculus
Medial geniculate body
Nucleus of oculomotor nerve
Nucleus of trochlear nerve
Nticleus of abducent nerve
Cortex of occipital lobes
FiQ. 722. — Scheme showing central connections of the optic nerves and optic tracts.
The roof (Fig. 723) is formed by a layer of epithelium, which stretches between
the upper edges of the lateral walls of the cavity and is continuous with the epithe-
lial lining of the ventricle. It is covered by and adherent to a fold of pia mater,
named the tela chorioidea of the third ventricle, from the under surface of which
a pair of vascular fringed processes, the choroid plexuses of the third ventricle,
project downward, one on either side of the middle line, and invaginate the
epithelial roof into the ventricular cavity.
The floor slopes downward and forward and is formed mainly by the structures
which constitute the hypothalamus: from before backward these are: the optic
816
NEUROLOGY
chiasma, the tuber cinereum and infundibulum, and the corpora mammillaria.
Behind the last, the floor is formed by the interpeduncular fossa and the tegmenta
of the cerebral peduncles. The ventricle is prolonged downward as a funnel-
shaped recess, the recessus infundibuli, into the infundibulum, and to the apex of
the latter the hypophysis is attached.
The anterior boundary is constituted below by the lamina terminalis, a thin layer
of gray substance stretching from the upper surface of the optic chiasma to the
rostrum of the corpus callosum; above by the columns of the fornix and the anterior
commissure. At the junction of the floor and anterior wall, immediately above
the optic chiasma, the ventricle presents a small angular recess or diverticulum,
the optic recess. Between the columns of the fornix, and above the anterior
commissure, is a second recess termed the vulva. At the junction of the roof and
anterior wall of the ventricle, and situated between the thalami behind and the
columns of the fornix in front, is the interventricular foramen {foramen of Monro)
through which the third communicates with the lateral ventricles.
R P U S:ZZC A:U L 0 S U K;
Epithelial lining
of ventricle
T , 1 /\ ' /null ft" \ ^~-^ Terminal vein
Lateral/ \ / / , ^T^^ -r ... ^ • a x. , . c / ^ Choroid flexiis of
ventricle' \ .■' HfiK THALAMUS / lateral ventricle
Tela chorioidea
Internal cerebral veins
Epithelial lining of ventricle
Choroid plexrises of third ventricle
Third ventricle
FiQ. 723. — Coronal section of lateral and third ventricles. (Diagrammatic.)
The posterior boundary is constituted by the pineal body, the posterior commissure
and the cerebral aqueduct. A small recess, the recessus pinealis, projects into the
stalk of the pineal body, while in front of and above the pineal body is a second
recess, the recessus suprapinealis, consisting of a diverticulum of the epithelium
which forms the ventricular roof.
Each lateral wall consists of an upper portion formed by the medial surface of
the anterior two-thirds of the thalamus, and a lower consisting of an upward
continuation of the gray substance of the ventricular floor. These two parts
correspond to the alar and basal laminae respectively of the lateral wall of the
fore-brain vesicle and are separated from each other by a furrow, the sulcus of
Monro, which extends from the interventricular foramen to the cerebral aqueduct
(pages 741 and 742). The lateral wall is limited above by the taenia thalami. The
columns of the fornix curve downward in front of the interventricular foramen, and
then run in the lateral walls of the ventricle, where, at first, they form distinct
prominences, but subsequently are lost to sight. The lateral walls are joined to
each other across the cavity of the ventricle by a band of gray matter, the massa
intermedia (page 809).
Interpeduncular Fossa (Fig. 724). — This is a somewhat lozenge-shaped area of the
base of the brain, limited in front by the optic chiasma, behind by the antero-
superior surface of the pons, antero-laterally by the converging optic tracts,
THE FORE-BRAIN OR PROSENCEPHALON
817
and postero-laterally by the diverging cerebral peduncles. The structures con-
tained in It have already been described; from behind forward, they are the pos-
terior perforated substance, corpora mamillaria, tuber cinereum, infundibulum,
and hypophysis.
Frontal lobe
Temporal
lobe
Occipital lobe
I'iG. 71-4. — Base of braia.
The Telencephalon. — The telencephalon includes: (1) the cerebral hemispheres
with their cavities, the lateral ventricles; and (2) the pars optica hypothalami and
the anterior portion of the third ventricle (already described under the dienceph-
alon). As previously stated (see page 744), each cerebral hemisphere may be
divided into three fundamental parts, viz., the rhinencephalon, the corpus
striatum, and the neopallium. The rhinencephalon, associated with the sense
of smell, is the oldest part of the telencephalon, and forms almost the whole of
the hemisphere in some of the lower animals, e. g., fishes, amphibians, and
reptiles. In man it is rudimentary, whereas the neopallium undergoes great
development and forms the chief part of the hemisphere.
The Cerebral Hemispheres. — The cerebral hemispheres constitute the largest
part of the brain, and, when viewed together from above, assume the form of
an ovoid mass broader behind than in front, the greatest transverse diameter
corresponding with a line connecting the two parietal eminences. The hemispheres
are separated medially by a deep cleft, named the longitudinal cerebral fissure,
•and each possesses a central cavity, the lateral ventricle.
52
81S
NEUROLOGY
The Longitudinal Cerebral Fissure { fissur a cerebri longitudinaUs: great longitudinal
fissure) contains a sickle-shaped process of dura mater, the falx cerebri. It front
and behind, the fissure extends from the upper to the under surfaces of the hemi-
spheres and completely separates them, but its middle portion separates them for
only about one-half of their vertical extent ; for at this part they are connected across
the middle line by a great central white commissure, the corpus callosum.
In a median sagittal section (Fig. 720) the cut corpus callosum presents the
appearance of a broad, arched band. Its thick posterior end, termed the splenium,
overlaps the mid-brain, but is separated from it by the tela chorioidea of the third
ventricle and ihc pineal body. Its anterior
curved end, termed the genu, gradually tapers
into a thinner portion, the rostrum, which is
continued downward and backward in front of
the anterior commissure to join the lamina
terminalis. Arching backward from immediately
behind the anterior commissure to the under
surface of the splenium is a second white band
named the fornix : between this and the corpus
callosum are the lamina? and cavity of the
septum pellucidum.
Surfaces of the Cerebral Hemispheres. — Each
hemisphere presents three surfaces: lateral,
medial, and inferior.
The lateral surface is convex in adaptation to
the concavity of the corresponding half of the
vault of the cranium. The medial surface is
flat and vertical, and is separated from that
of the opposite hemisphere bj^ the great longi-
tudinal fissure and the falx cerebri. The inferior
surface is of an irregular form, and may be divided
into three areas: anterior, middle, and posterior.
The anterior area, formed by the orbital sur-
face of the frontal lobe, is concave, and rests on
the roof of the orbit and nose; the middle area
is convex, and consists of the under surface of
the temporal lobe: it is adapted to the corre-
sponding half of the middle cranial fossa. The
posterior area is concave, directed medialward
as well as downward, and is named the tentorial
surface, since it rests upon the tentorium cere-
belli, which intervenes between it and the upper
surface of the cerebellum.
These three surfaces are separated from
each other by the following borders: (a)
supero-medial, between the lateral and medial surfaces; (b) infero-lateral, between
the lateral and inferior surfaces; the anterior part of this border separating the
lateral from the orbital surface, is known as the superciliary border; (c) medial
occipital, separating the medial and tentorial surfaces; and {d) medial orbital,
separating the orbital from the medial surface. The anterior end of the hemi-
sphere is named the frontal pole; the posterior, the occipital pole; and the anterior
end of the temporal lobe, the temporal pole. About o cm. in front of the occipital
pole on the infero-lateral border is an indentation or notch, named the preoccipital
notch.
The surfaces of the hemispheres are moulded into a number of irregular emi-
FlQ.
725. — Lateral surface of left cerebral
hemisphere, \-iewed from above.
THE FORE-BRAIN OR PROSENCEPHALON
819
nences, named gyri or convolutions, and separated by furrows termed fissures and
sulci. The furrows are of two kinds, complete and incomplete. The former appear
early in fetal life, are few in number, and are produced by infoldings of the entire
thickness of the brain wall, and give rise to corresponding elevations in the interior
of the ventricle. They comprise the hippocampal fissure, and parts of the calcarine
and collateral fissures. The incomplete furrows are very numerous, and only indent
the subjacent white substance, without producing any corresponding elevations in
the ventricular cavity.
The gyri and their intervening fissures and the sulci are fairly constant in their
arrangement; at the same time they vary within certain limits, not only in different
individuals, but on the two hemispheres of the same brain. The convoluted con-
dition of the surface permits of a great increase of the gray matter without the
sacrifice of much additional space. The number and extent of the gyri, as well
as the depth of the intervening furrows, appear to bear a direct relation to the
intellectual powers of the individual.
Certain of the fissures and sulci are utilized for the purpose of dividing the hemi-
sphere into lobes, and are therefore termed interlobular; includetl under this category
are the lateral cerebral, parietooccipital, calcarine, and collateral fissures, the
central and cingulate sulci, and the sulcus circularis.
Fig. 726. — Lateral surface of left cerebral hemisphere, viewed from the side.
The Lateral Cerebral Fissure {fissura cerebri lateralis [Syhii]; fissure of Sylvius) (Fig.
726) is a well-marked cleft on the inferior and lateral surfaces of the hemisphere,
and consists of a short stem which divides into three rami. The stem is situated
on the base of the brain, and commences in a depression at the lateral angle of the
anterior perforated substance. From this point it extends between the anterior
part of the temporal lobe and the orbital surface of the frontal lobe, and reaches
the lateral surface of the hemisphere. Here it divides into three rami: an anterior
horizontal, an anterior ascending, and a posterior. The anterior horizontal ramus
passes forward for about 2.5 cm. into the inferior frontal gyrus, while the anterior
ascending ramus extends upward into the same convolution for about an equal
distance. The posterior ramus is the longest; it runs backward and slightly upward
for about 7 cm., and ends by an upward inflexion in the parietal lobe.
The Central Sulcus (sidcits centralis [Rolafidi]; fissure of Rolando; central fissure)
820
NEUROLOGY
(Figs. 725, 72G) is situated about the middle of the lateral surface of the hemisphere,
and begins in or near the longitudinal cerebral fissure, a little behind its mid-point.
It runs sinuously downward and forward, and ends a little above the posterior
ramus of the lateral fissure, and about 2.5 cm. behind the anterior ascending ramus
of the same fissure. It described two chief curves: a superior genu with its con-
cavity directed forward, and an inferior genu with its concavity directed backward.
The central sulcus forms an angle opening forward of about 70° with the median
plane.
The Parietooccipital Fissure {fissura jmrietooccipitalis). — Only a small part of this
fissure is seen on the lateral surface of the hemisphere, its chief part being on the
medial surface.
The lateral part of the parietooccipital fissure (Fig. 726) is situated about 5 cm.
in front of the occipital pole of the hemisphere, and measures about 1.25 cm. in
length.
Fig. 727. — Medial surface of left cerebral hemisphere.
The medial part of the parietooccipital fissure (Fig. 727) runs downward and for-
ward as a deep cleft on the medial surface of the hemisphere, and joins the calcarine
fissure below and behind the posterior end of the corpus callosum. In most cases
it contains a submerged gyrus.
The Calcarine Fissure (fissura calcarina) (Fig. 727) is on the medial surface of
the hemisphere. It begins near the occipital pole in two converging rami, and runs
forward to a point a little below the splenium of the corpus callosum, where it is
joined at an acute angle by the medial part of the parietooccipital fissure. The
anterior part of this fissure gives rise to the prominence of the calcar avis in the
posterior cornu of the lateral ventricle.
The Cingulate Sulcus (sulcus cinguli; callosomarginal fissure) (Fig. 727) is on the
medial surface of the hemisphere; it begins below the anterior end of the corpus
callosum and runs upward and forward nearly parallel to the rostrum of this body
and, curving in front of the genu, is continued backward above the corpus callosum,
and finally ascends to the supero-medial border of the hemisphere a short distance
behind the upper end of the central sulcus. It separates the superior frontal from
the cingulate gyrus.
The Collateral Fissure (fissura coUaieralis) (Fig. 727) is on the tentorial surface
of the hemisphere and extends from near the occipital pole to within a short dis-
tance of the temporal pole. Behind, it lies below and lateral to the calcarine fissure,
THE FORE-BRAIN OR PROSENCEPHALON
821
from which it is separated by the lingual gyrus; in front, it is situated between the
hippocampal gyrus and the anterior part of the fusiform gyrus.
The Sulcus Circularis (circumimular fissure) (Fig. 731) is on the lower and lateral
surfaces of the hemisphere: it surrounds the insula and separates it from the
frontal, parietal, and temporal lobes.
Lobes of the Hemispheres.— By means of these fissures and sulci, assisted by
certain arbitrary lines, each hemisphere is divided into the following lobes: the
frontal, the parietal, the temporal, the occipital, the limbic, and the insula.
Frontal Lobe (lobus frontalis). ^On the lateral surface of the hemisphere this lobe
extends from the frontal pole to the central sulcus, the latter separating it from
the parietal lobe. Below, it is limited by the posterior ramus of the lateral
fissure, which intervenes between it and the central lobe. On the medial sur-
face, it is separated from the cingulate gyrus by the cingulate sulcus; and on the
inferior surface, it is bounded behind by the stem of the lateral fissure.
IPITAL F.
Fig. 728. — Principal fissures and lobes of the cerebrum viewed laterally.
The lateral surface of the frontal lobe (Fig. 726) is traversed by three sulci which
divide it into four gyri: the sulci are named the precentral, and the superior and
inferior frontal; the gyri are the anterior central, and the superior, middle, and
inferior frontal. The precentral sulcus runs parallel to the central sulcus, and is
usually divided into an upper and a lower part; between it and the central sulcus is
the anterior central gyrus. PVom the precentral sulcus, the superior and inferior
frontal sulci run forward and downward, and divide the remainder of the lateral
surface of the lobe into three parallel gyri, named, respectively the superior, middle,
and inferior frontal gyri.
The anterior central gyrus (gyrus centralis anterior; ascending frontal convolution;
precentral gyre) is bounded in front by the precentral sulcus, behind by the central
sulcus; it extends from the supero-medial border of the hemisphere to the posterior
ramus of the lateral fissure.
The superior frontal gyrus (gyrus frontalis superior; superfrontal gyre) is situated
above the superior frontal sulcus and is continued on to the medial surface of the
hemisphere. The portion on the lateral surface of the hemisphere is usually more
or less completely subdivided into an upper and a lower part by an antero-
822
NEUROLOGY
posterior sulcus, the paramedial sulcus, which, however, is frequently interrupted
by bridging: gyri.
The middle frontal gyrus {gyrus frontalis medius; medifrontal gyre), between the
superior and inferior frontal sulci, is continuous with the anterior orbital gyrus on
the inferior surface of the hemisphere; it is frequently subdivided into two by a
horizontal sulcus, the medial frontal sulcus of Eberstaller, which ends anteriorly in
a wide bifurcation.
The inferior frontal gyrus {gyrus frontalis inferior; suhfronial gyre) lies below the
inferior frontal sulcus, and extends forward from the lower part of the precentral
sulcus; it is continuous with the lateral and posterior orbital gyri on the under
surface of the lobe. It is subdivided by the anterior horizontal and ascending rami
of the lateral fissure into three parts, viz., (1) the orbital part, below the anterior
horizontal ramus of the fissure; (2) the triangular part {cap of Broca), between
the ascending and horizontal rami; and (3) the basilar part, behind the anterior
ascending ramus. The left inferior frontal gyrus is, as a rule, more highly
developed than the right, and is named the gjrrus of Broca, from the fact that
Broca described it as the center for articulate speech.
The inferior or orbital surface of the frontal lobe is concave, and rests on the orbital
plate of the frontal bone (Fig. 729). It is divided into four orbital gyri by a well-
marked H-shaped orbital sulcus. These are
named, from their position, the medial, anterior,
lateral, and posterior orbital gyri. The medial
orbital gyrus presents a well-marked antero-
posterior sulcus, the olfactory sulcus, for the
olfactory tract; the portion medial to this is
named the straight gyrus, and is continuous with
the superior frontal gyrus on the medial surface.
The medial surface of the frontal lobe is occu-
pied by the medial part of the superior frontal
gyrus {marginal gyrus) (Fig. 727). It lies be-
tween the cingulate sulcus and the supero-medial
margin of the hemisphere. The posterior part
of this gyrus is sometimes marked off by a ver-
tical sulcus, and is distinguished as the paracen-
tral lobule, because it is continuous with the
anterior and posterior central gyri.
Parietal Lobe {lobus j^arietaUs) .—The parietal
lobe is separated from the frontal lobe by the
central sulcus, but its boundaries below and
behind are not so definite. Posteriorly, it is limited by the parietooccipital fissure,
and by a line carried across the hemisphere from the end of this fissure toward
the preoccipital notch. Below, it is separated from the temporal lobe by the
posterior ramus of the lateral fissure, and by a line carried backward from it to
meet the line passing downward to the preoccipital notch.
The lateral surface of the parietal lobe (Fig. 72(5) is cleft by a well-marked furrow,
the intraparietal sulcus of Turner, which consists of an oblique and a horizontal
portion. The oblique part is named the postcentral sulcus, and commences below,
about midway between the lower end of the central sulcus and the upturned end
of the lateral fissure. It runs upward and backward, parallel to the central sulcus,
and is sometimes divided into an upper and a lower ramus. It forms the hinder
limit of the posterior central gyrus.
From about the middle of the postcentral sulcus, or from the upper end of its
inferior ramus, the horizontal portion of the intraparietal sulcus is carried backward
and slightly upward on the parietal lobe, and is prolonged, under the name of the
Fig. 729. — Orbital surface of left frontal lobe.
THE FORE-BRAIN OR PROSENCEPHALON 823
occipital ramus, on to the occipital lobe, where it divides into two parts, which form
nearly a right angle with the main stem and constitute the transverse occipital sulcus.
The part of the parietal lobe above the horizontal portion of the intraparietal
sulcus is named the superior parietal lobule; the part below, the inferior parietal lobule.
The posterior central gyrus {gyrus centralis -j^osterior; ascending parietal convolution;
■postcentral gyre) extends from the longitudinal fissure above to the posterior ramus
of the lateral fissure below. It lies parallel with the anterior central gyrus, Avith
which it is connected below, and also, sometimes, above, the central sulcus.
The superior parietal lobule {lobulus parietalis superior) is bounded in front by
the upper part of the postcentral sulcus, but is usually connected with the pos-
terior central gyrus above the end of the sulcus; behind it is the lateral part of
the parietooccipital fissure, around the end of which it is joined to the occipital
lobe by a curved gyrus, the arcus parietooccipitalis ; below, it is separated from the
inferior parietal lobule by the horizontal portion of the intraparietal sulcus.
The inferior parietal lobule {lobulus parietalis inferior; suhparietal district or lobule)
lies below the horizontal portion of the intraparietal sulcus, and behind the lower
part of the postcentral sulcus. It is divided from before backward into two gyri.
One, the supramarginal, arches over the upturned end of the lateral fissure; it is
continuous in front with the postcentral gyrus, and behind with the superior tem-
poral gyrus. The second, the angular, arches over the posterior end of the superior
temporal sulcus, behind which it is continuous with the middle temporal gyrus.
The medial surface of the parietal lobe (Fig. 727) is bounded behind by the
medial part of the parietooccipital fissure; in front, by the posterior end of the cin-
gulate sulcus; and below, it is separated from the cingulate gyrus by the subparietal
sulcus. It is of small size, and consists of a square-shaped convolution, which is
termed the precuneus or quadrate lobe.
Occipital Lobe (lobus occipitalis). — The occipital lobe is small and pyramidal
in shape; it presents three surfaces: lateral, medial, and tentorial.
The lateral surface is limited in front by the lateral part of the parietooccipital
fissure, and by a line carried from the end of this fissure to the preoccipital notch;
it is traversed by the transverse occipital and the lateral occipital sulci. The
transverse occipital sulcus is continuous with the posterior end of the occipital
ramus of the intraparietal sulcus, and runs across the upper part of the lobe, a
short distance behind the parietooccipital fissure. The lateral occipital sulcus
extends from behind forward, and divides the lateral surface of the occipital lobe
into a superior and an inferior gyrus, which are continuous in front with the parietal
and temporal lobes. ^
The medial surface of the occipital lobe is bounded in front by the medial part
of the parietooccipital fissure, and is traversed by the calcarine fissure, which
subdivides it into the cuneus and the lingual gyrus. The cuneus is a wedge-shaped
area between the calcarine fissure and the medial part of the parietooccipital
fissure. The lingual gyrus lies between the calcarine fissure and the posterior part
of the collateral fissure; behind, it reaches the occipital pole; in front, it is con-
tinued on to the tentorial surface of the temporal lobe, and joins the hippocampal
gyrus.
The tentorial surface of the occipital lobe is limited in front by an imaginary
transverse line through the preoccipital notch, and consists of the posterior part
of the fusiform gyrus {occipitotemporal convolution) and the lower part of the lingual
gyrus, which are separated from each other by the posterior segment of the
collateral fissure.
Temporal Lobe {lobus temporalis). — The temporal lobe presents superior, lateral,
and inferior surfaces.
' Elliot Smith has named the lateral occipital sulcus the sulcus lunatus; he regards it as the representative, in the
human brain, of the " Affenspalte " of the brain of the ape.
824
NEUROLOGY
The superior surface forms the lower limit of the lateral fissure and overlaps
the insula. On opening out the lateral fissure, three or four gyri will be seen spring-
ing from the depth of the hinder end of the fissure, and running obliquely forward
and outward on the posterior part of the upper surface of the superior temporal
gyrus; these are named the transverse temporal gyri (Heschl) (Fig. 730).
The lateral surface (Fig. 726) is bounded above by the posterior ramus of the
lateral fissure, and by the imaginary line continued backward from it; below,
it is limited by the infero-lateral border of the hemisphere. It is divided into
superior, middle, and inferior gyri by the superior and middle temporal sulci.
The superior temporal sulcus runs from before backward across the temporal lobe,
some little distance below, but parallel with, the posterior ramus of the lateral
fissure; and hence it is often termed the parallel sulcus. The middle temporal sulcus
takes the same direction as the superior, but is situated at a lower level, and is
usually subdivided into two or more parts. The superior temporal gyrus lies between
Claustrum
Insula
Transverse temporal gyri
■ Thalamus
Optic tract
Lentiform nucleus
Internal capsule
Fimbria
Tail of Caudate nucleus
//"'%\ — Inferior cornu of lateral
ventricle
FiQ. 730. — Section of brain showing upper surface of temporal lobe.
the posterior ramus of the lateral fissure and the superior temporal sulcus, and is
continuous behind with the supramarginal and angular gyri. The middle temporal
gyrus is placed between the superior and middle temporal sulci, and is joined pos-
teriorly with the angular gyrus. The inferior temporal gyrus is placed below the
middle temporal sulcus, and is connected behind with the inferior occipital gyrus;
it also extends around the infero-lateral border on to the inferior surface of the
temporal lobe, where it is limited by the inferior sulcus.
The inferior surface is concave, and is continuous posteriorly with the tentorial
surface of the occipital lobe. It is traversed by the inferior temporal sulcus, which
extends from near the occipital pole behind, to within a short distance of the tem-
poral pole in front, but is frequently subdivided by bridging gyri. Lateral to this
fissure is the narrow tentorial part of the inferior temporal gyrus, and medial to
it the fusiform gyrus, which extends from the occipital to the temporal pole; this
gyrus is limited medially by the collateral fissure, which separates it from the
lingual gyrus behind and from the hippocampal gyrus in front.
THE FORE-BRAIN OR PROSENCEPHALON 825
The Insula {island of Reil; central lobe) (Fig. 731) lies deeply in the lateral or
Sylvian fissure, and can only be seen when the lips of that fissure are widely sep-
arated, since it is overlapped antl hidden by the gyri which bound the fissure.
These gyri are termed the opercula of the insula ; they are separated from each other
by the three rami of the lateral fissure, and are named the orbital, frontal, fronto-
parietal, and temporal opercula. The orbital operculum lies below the anterior
horizontal ramus of the fissure, the frontal between this and the anterior ascending
ramus, the parietal between the anterior ascending ranms and the upturned end
of the posterior ramus, and the temporal below the posterior ramus. The frontal
operculum is of small size in those cases where the anterior horizontal and ascending
rami of the lateral fissure arise from a common stem. The insula is surrounded
by a deep circular sulcus which separates it from the frontal, parietal, and temporal
lobes. When the opercula have been removed, the insula is seen as a triangular
eminence, the apex of which is directed toward the anterior perforated substance.
It is divided into a larger anterior and a smaller posterior part by a deep sulcus,
which runs backward and upward from the apex of the insula. The anterior
part is subdivided by shallow sulci into three or four short gyri, while the posterior
part is formed by one long gyrus, which is often bifurcaterl at its upper end. The
cortical gray substance of the insula is continuous with that of the different opercula,
while its deep surface corresponds with the lentiform nucleus of the corpus striatum.
FiQ. 731. — The insula of the left side, exposed by removing the opercula.
Limbic Lobe (Fig. 727). — -The term limbic lobe Avas introduced by Broca, and
under it he included the cingulate and hippocampal gyri, which together arch
around the corpus callosum and the hippocampal fissure. These he separated on
the morphological ground that they are well-developed in animals possessing a
keen sense of smell (osmatic animals), such as the dog and fox. They were thus
regarded as a part of the rhinencephalon, but it is now recognized that they belong
to the neopallium; the cingulate gyrus is therefore sometimes described as a part
of the frontal lobe, and the hippocampal as a part of the temporal lobe.
The cingulate gyrus (gyrus cingiili; caUosal convolution) is an arch-shaped convo-
lution, lying in close relation to the superficial surface of the corpus callosum,
from which it is separated by a slit-like fissure, the callosal fissure. It commences
below the rostrum of the corpus callosum, curves around in front of the genu,
extends along the upper surface of the body, and finally turns downward behind
the splenium, where it is connected by a narrow isthmus with the hippocampal
826
NEUROLOGY
gyrus. It is separated from the medial part of the superior frontal gyrus by the
cingulate sulcus, and from the precuneus by the subparietal sulcus.
The hippocampal gyrus {gyrus hipi^tocampi) is bounded above by the hippocampal
fissure, and below by the anterior part of the collateral fissure. Behind, it is con-
tinuous superiorly, through the isthmus, with the cingulate gyrus and inferiorly
with the lingual gyrus. Running in the substance of the cingulate and hippocampal
gyri, and connecting them together, is a tract of arched fibers, named the cingulum
(page 84.3). The anterior extremity of the hippocampal gyrus is recurved in the
form of a hook (uncus), which is separated from the apex of the temporal lobe by
a slight fissure, the incisura temporalis. Although superficially continuous with the
hippocampal gyrus, the uncus forms morphologically a part of the rhinencephalon.
The Hippocampal Fissure {fissura hippocamin; dentate fissure) begins immediately
behind the splenium of the corpus callosum, and runs forward between the hippo-
campal and dentate gyri to end in the uncus. It is a complete fissure (page 819),
and gives rise to the prominence of the hippocampus in the inferior cornu of the
lateral ventricle.
Gyrus supracallosus
Fascia dentata
hippocampi
OLfactoji
Lateral root
Anterior perforated substance
I Uncus
Band of Giacomini
Fig. 732. — Scheme of rhinencephalon.
Rhinencephalon (Fig. 732). — The rhinencephalon comprises the olfactory lobe,
the uncus, the subcallosal and supracallosal gyri, the fascia dentata hippocampi,
the septum pellucidum, the fornix, and the hippocampus.
1 . The Olfactory Lobe {lobus olfadorius) is situated under the inferior or orbital
surface of the frontal lobe. In many vertebrates it constitutes a well-marked
portion of the hemisphere and contains an extension of the lateral ventricle; but
in man and some other mammals it is rudimentary. It consists of the olfactory
bulb and tract, the olfactory trigone, the parolfactory area of Broca, and the anterior
perforated substance.
(a) The olfactory bulb (bulbus olfactorius) is an oval, reddish-gray mass which
rests on the cribriform plate of the ethmoid and forms the anterior expanded
extremity of the olfactory tract. Its under surface receives the olfactory nerves,
which pass upward through the cribriform plate from the olfactory region of the
nasal cavity. Its minute structure is described on page 848.
(6) The olfactory tract {irachis olfadorius) is a narrow white band, triangular
on coronal section, the apex being directed upward. It lies in the olfactory sulcus
on the inferior surface of the frontal lobe, and divides posteriorly into two strise,
a medial and a lateral. The lateral stria is directed across the lateral part of the
THE FORE-BRAIN OR PROSENCEPHALON 827
anterior perforated substance and then bends abruptly mediahvard toward the
uncus of the hippocampal gyrus. The medial stria turns mediahvard behind
the parolfactory area and ends in the subcallosal gyrus; in some cases a small
intermediate stria is seen running backward to the anterior perforated substance.
(c) The olfactory trigone (trigonum olf actor ium) is a small triangular area in front
of the anterior perforated substance. Its apex, directed forward, occupies the
posterior part of the olfactory sulcus, and is brought into view by throwing back
the olfactory tract.
{d) The parolfactory area of Broca {area parolfactoria) is a small triangular field
on the medial surface of the hemisphere in front of the subcallosal gyrus, from which
it is separated by the posterior parolfactory sulcus; it is continuous below with
the olfactory trigone, and above and in front with the cingulate gyrus; it is limited
anteriorly by the anterior parolfactory sulcus.
(e) The anterior perforated substance (substantia perforata anterior) is an irregularly
quadrilateral area in front of the optic tract and behind the olfactory trigone,
from which it is separated by the fissure prima ; medially and in front it is continuous
with the subcallosal gyrus; laterally it is bounded by the lateral stria of the olfactory
tract and is continued into the uncus. Its gray substance is confluent above
with that of the corpus striatum, and is perforated anteriorly by numerous small
bloodvessels.
2. The Uncus has already been described (page 826) as the recurved, hook-like
portion of the hippocampal gyrus.
3. The Subcallosal, Supracallosal, and Dentate Gyri form a rudimentary arch-
shaped lamina of gray substance extending over the corpus callosum and above
the hippocampal gyrus from the anterior perforated substance to the uncus.
(a) The subcallosal gyrus (gyrus subcallosus; peduncle of the corpus callosum) is
a narrow lamina on the medial surface of the hemisphere in front of the lamina
terminalis, behind the parolfactory area, and below the rostrum of the corpus
callosum. It is continuous around the genu of the corpus callosum with the supra-
callosal gyrus.
(b) The supracallosal gyrus {indusium griseum; gyrus epicallosus) consists of a
thin layer of gray substance in contact with the upper surface of the corpus
callosum and continuous laterally w^ith the gray substance of the cingulate gyrus.
It contains two longitudinally directed strands of fibers termed respectively the
medial and lateral longitudinal striae. The supracallosal gyrus is prolonged around
the splenium of the corpus callosum as a delicate lamina, the fasciola cinerea,
which is continuous below with the fascia dentata hippocampi.
(c) The fascia dentata hippocampi (gyrus dentatus) is a narrow band extending
downward and forward above the hippocampal gyrus but separated from it by
the hippocampal fissure; its free margin is notched and overlapped by the fimbria
— the fimbriodentate fissure intervening. Anteriorly it is continued into the notch
of the uncus, where it forms a sharp bend and is then prolonged as a delicate band,
the band of Giacomini, over the uncus, on the lateral surface of which it is lost.
The remaining parts of the rhinencephalon, viz., the septum pellucidum, fornix,
and hippocampus, will be described in connection with the lateral ventricle.
Interior of the Cerebral Hemispheres. — If the upper part of either hemisphere be
removed, at a level about 1.25 cm. above the corpus callosum, the central white sub-
stance will be exposed as an oval-shaped area, the centrum ovale minus, surrounded
by a narrow convoluted margin of gray substance, and studded with numerous
minute red dots (puncta vasculosa), produced by the escape of blood from divided
bloodvessels. If the remaining portions of the hemispheres be slightly drawn apart
a broad band of white substance, the corpus callosum, will be observed, connecting
them at the bottom of the longitudinal fissure; the margins of the hemispheres
which overlap the corpus callosum are called the labia cerebri. Each labrium is
828
NEUROLOGY
part of the cingulate gyrus already described; and the slit-like interval between
it and the upper surface of the corpus callosum is termed the callosal fissure (Fig.
727). If the hemispheres be sliced off to a level with the upper surface of the corpus
callosum, the white substance of that structure will be seen connecting the two
hemispheres. The large expanse of medullary matter now exposed, surrounded by
the convoluted margin of gray substance, is called the centrum ovale majus.
The Corpus Callosum (Fig. 733) is the great transverse commissure which unites
the cerebral hemispheres and roofs in the lateral ventricles. A good conception
of its position and size is obtained by examining a median sagittal section of the
brain (Fig. 720), when it is seen to form an arched structure about 10 cm. long.
Its anterior end is about 4 cm. from the frontal pole, and its posterior end about
6 cm. from the occipital pole of the hemisphere.
Fig. 733. — Corpus callosum from above.
The anterior end is named the genu, and is bent downward and backward in front
of the septum pellucidum ; diminishing rapidly in thickness, it is prolonged backward
under the name of the rostrum, which is connected below with the lamina terminalis.
The anterior cerebral arteries are in contact with the under surface of the rostrum;
they then arch over the front of the genu, and are carried backward above the body
of the corpus callosum.
The posterior end is termed the splenium and constitutes the thickest part of the
corptis callosum. It overlaps the tela chorioidea of the third ventricle and the
mid-brain, and ends in a thick, convex, free border. A sagittal section of
THE FORE-BRAIN OR PROSENCEPHALON
829
the splenium shows that the posterior end of the corpus callosum is acutely bent
forward, the upper and lower parts being applied to each other.
The superior surface is convex from before backward, and is about 2.5 cm. wide.
Its medial part forms the bottom of the longitudinal fissure, and is in contact
posteriorly with the lower border of the falx cerebri. Laterally it is overlapped by
the cingulate gyrus, but is separated from it by the slit-like callosal fissure. It is
traversed by numerous transverse ridges and furrows, and is covered by a thin
layer of gray matter, the supracallosal gyrus, which exhibits on either side of the
middle line the medial and lateral longitudinal striie, already described (page S27).
The inferior surface is concave, and forms on either side of the middle hne the
roof of the lateral ventricle. Medially, this surface is attached in front to the
septum pellucidum; behind this it is fused with the upper surface of the body
of the fornix, while the splenium is in contact with the tela chorioidea.
On either side, the fibers of the corpus callosum radiate in the white substance
and pass to the various parts of the cerebral cortex; those curving forward from the
genu into the frontal lobe constitute the forceps anterior, and those curving backward
into the occipital lobe, the forceps posterior. Between these two parts is the main
body of the fibers which constitute the tapetum and extend laterally on either side
into the temporal lobe, and cover in the central part of the lateral ventricle.
Cerebral aqtieduct
Fourth ventricle
Fig. 73-t. — Scheme showing relations of the ventricles to the surface of the brain.
The Lateral Ventricles (ventricnlus lateralis) (Fig. 734).' — The two lateral ventricles
are irregular cavities situated in the lower and medial parts of the cerebral hemi-
spheres, one on either side of the middle line. The}' are separated from each other
by a median vertical partition, the septum pellucidum, but communicate with the
third ventricle and indirectly with each other through the interventricular foramen.
They are lined by a thin, diaphanous membrane, the ependyma, covered by ciliated
epithehum, and contain cerebrospinal fluid, which, even in health, may be secreted
in considerable amount. Each lateral ventricle consists of a central part or body,
and three prolongations from it, termed cornua (Figs. 735, 736).
The central part (pars centralis ventriculi lateralis; cella) (Fig. 737) of the lateral
ventricle extends from the interventricular foramen to the splenium of the corpus
830
NEUROLOGY
callosum. It is an irregularly curved cavity, triangular on transverse section,
with a roof, a floor, and a medial wall. The roof is formed by the under surface of
the corpus callosum ; the floor by the following parts, enumerated in their order of
position, from before backward: the caudate nucleus of the corpus striatum, the
Third ventricle
Suprapineal recess
Fig. 735. — Drawing of a cast of the ventricular cavities, viewed from above. (Retzius.)
stria terminalis and the terminal vein, the lateral portion of the upper surface of
the thalamus, the choroid plexus, and the lateral part of the fornix; the medial
wall is the posterior part of the septum pellucidum, which separates it from the
opposite ventricle.
IniervoUricidar joramen
commissure
Suprapineal recess
Cerebral aqueduct
recess
Infundibuium
Lateral recess
FiQ 736. — Drawing of a cast of the ventricular cavities, viewed from the side. (Retzius.)
The anterior cornu (cornu anteriiis; anterior horn; precorjiu) (Fig. 736) passes
forward and lateralward, with a slight inclination downward, from the interventric-
ular foramen into the frontal lobe, curving around the anterior end of the caudate
nucleus. Its floor is formed by the upper surface of the; reflected portion of the
THE FORE-BRAIN OR PROSENCEPHALON
831
corpus callosum, the rostrum. It is bounded medially by the anterior portion
of the septum pellucidum, and laterally by the head of the caudate nucleus. Its
apex reaches the posterior surface of the genu of the corpus callosum.
The posterior cornu {cornu posterius; yostcornu) (Figs. 737, 738) passes into the
occipital lobe, its direction being backward and laterahvard, and then mediahvard.
Its roof is formed by the fibers of the corpus callosum passing to the temporal and
occipital lobes. On its medial wall is a longitudinal eminence, the calcar avis
{hippocampus minor) ,\\\\\ch. is an involution of the ventricular wall produced by
the calcarine fissure. Above this the forceps posterior of the corpus callosum,
sweeping around to enter the occipital lobe, causes another projection, termed the
bulb of the posterior cornu. The calcar avis and bulb of the posterior cornu are
extremely variable in their degree of development; in some cases they are ill-
defined, in others prominent.
Fig. 737. — Central part and anterior and posterior cornua of lateral ventricles exposed from above.
The inferior cornu [cornu inferior; descending horn; middle horn; medicornu) (Fig.
739), the largest of the three, traverses the temporal lobe of the brain, forming
in its course a curve around the posterior end of the thalamus. It passes at first
backward, laterahvard, and downward, and then curves forward to within 2.5 cm.
of the apex of the temporal lobe, its direction being fairly well indicated on the
surface of the brain by that of the superior temporal sulcus. Its roof is formed
chiefly by the inferior surface of the tapetum of the corpus callosum, but the tail
of the caudate nucleus and the stria terminalis also extend forward in the roof of
the inferior cornu to its extremity ; the tail of the caudate nucleus ioins the
832
NEUROLOGY
putamen. Its floor presents the following parts: the hippocampus, the fimbria
hippocampi, the collateral eminence, and the choroid plexus. When the
Bulb of posterior corni
Posterior cornu
Calcar avis
Collateral eminence
Calcarine fissure
Collateral fissure
Fig. 738. — Coronal section through posterior cornua of lateral ventricle
choroid plexus is removed, a cleft-like opening is left along the medial wall of
the inferior cornu; this cleft constitutes the lower part of the choroidal fissure.
Choroid plexus
Bulb of posterior cornu
Calcar avis
Lateral
cerebral
fissure -^^M^^^^^^^™.™ ^^mm^\
\ Collateral eminence
Fiiribria hippocampi
Uippocampus
Fig. 739. — Posterior and inferior cornua of left lateral ventricle exposed from the side.
The hippocampus (hippocampus major) (Figs. 739, 740) is a curved eminence,
about 5 cm. long, which extends throughout the entire length of the floor of the
THE FORE-BRAIN OR PROSENCEPHALON
833
inferior cornu. Its lower end is enlarged, and presents two or three rounded eleva-
tions or digitations which give it a paw-like appearance, and hence it is named
the pes hippocampi. If a transverse section be made through the hippocampus,
It will be seen that this eminence is produced by the folding of the wall of the
hemisphere to form the hippocampal fissure. The main mass of the hippocampus
consists of gray substance, but on its ventricular surface is a thin white layer,
the alveus, which is continuous with the fimbria hippocampi.
The collateral eminence (cminentia coUateralis) (Fig. 740) is an elongated
swelling lying lateral to and parallel with the hippocampus. It corresponds with
the middle part of the collateral fissure, and its size depends on the depth and
direction of this fissure. It is continuous behind with a flattened triangular area,
the trigonum collaterale, situated between the posterior and inferior cornua.
The fimbria hippocampi is a continuation of the crus of the fornix, and will be
discussed with that body; a description of the choroid plexus will be found on
page 840.
,.»^'
liU^
//
\^
l.n"-"^'"'
Fig. 740. — Inferior and posterior cornua,
viewed from above.
Fig. 741. — Two \'iews of a model of the striatum:
lateral aspect; B, mesal aspect.
-4,
The corpus striatum has received its name from the striped appearance which
a section of its anterior part presents, in consequence of diverging white fibers
being mixed with the gray substance which forms its chief mass. A part of the
corpus striatum is imbedded in the white substance of the hemisphere, and is
therefore external to the ventricle; it is termed the extraventricular portion, or the
lentiform nucleus ; the remainder, howe^■e^, projects into the ventricle, and is named
the intraventricular portion, or the caudate nucleus (Fig. 737).
The caudate nucleus {nucleus can datus; caudatum) (Figs. 741, 742) is a pear-shaped,
highly arched gray mass; its broad extremity, or head, is directed forward into the
anterior cornu of the lateral ventricle, and is continuous with the anterior perforated
substance and with the anterior end of the lentiform nucleus; its narrow end,
or tail, is directed backward on the lateral side of the thalamus, from which it is
53
834
NEUROLOGY
separated by the stria terminalis and the terminal vein. It is then continued
downward into the roof of the inferior cornu, and ends in the putamen near the
apex of the temporal lobe. It is covered by the lining of the ventricle, and crossed
by some veins of considerable size. It is separated from the lentiform nucleus,
in the greater part of its extent, by a thick lamina of white substance, called the
internal capsule, but the two portions of the corpus striatum are united in front
(Figs. 743, 744).
Genu of corpus callosum
Anterior cornu of lateral ventricle
Caudate nucleus
Septum pellucidum
Into-nal capsule (frontal part)
Column of fornix
Genu of internal capsule
Putamen
Globus pallidus
Internal capsule (occipital part)
Thalannus
Tail of caudate nucleus
Uippocainpus
Inferior cornu of lateral ventricle
Area striata
Posterior cornu of lateral ventricle
Exteriial capstUe
Claustrum
Insula
Oplic radiation
Fig. 712. — Horizontal section of right cerebral hemisphere.
The lentiform nucleus {nucleus leniiformis; lenticular nucleus; lenticula) (Fig. 741)
is lateral to the caudate nucleus and thalamus, and is seen only in sections of the
hemisphere. When divided horizontally, it exhibits, to some extent, the appearance
of a biconvex lens (Fig. 742), while a coronal section of its central part presents a
somewhat triangular outline. It is shorter than the caudate nucleus and does not
extend as far forward. It is bounded laterally by a lamina of white substance
called the external capsule, and lateral to this is a thin layer of gray substance
termed the claustrum. Its anterior end is continuous with the lower part of the
head of the caudate nucleus and with the anterior perforated substance.
In a coronal section through the middle of the lentiform nucleus, two medullary
laminae are seen dividing it into three parts. The lateral and largest part is of a
reddish color, and is known as the putamen, while the medial and intermediate are of
THE FORE-BRAIN OR PROSENCEPHALON
835
a yellowish tint, and together constitute the globus pallidus; all three are marked by
fine radiating white fibers, which are most distinct in the putamen (Fig. 744).
The gray substance of the corpus striatum is traversed by nerve fibers, some
of which originate in it. The cells are multipolar, both large and small; those of
the lentiform nucleus contain yellow pigment. The caudate and lentiform nuclei
are not only directly continuous with each other anteriorly, but are connected to
each other by numerous fibers. The corpus striatum is also connected: (1) to the
cerebral cortex, by what are termed the corticostriate fibers; (2) to the thalamus,
by fibers which pass through the internal capsule, and by a strand named the
ansa lentiformis; (3) to the cerebral peduncle, by fibers which leave the lower
aspect of the caudate and lentiform nuclei.
Superior frontal gyrus
Middle frontal
gyrus
Corpus callosuin
Anterior corini
Septum pellueidum
Caudate nucleus
Internal capsule
Lentiform nucleu
Sulcus olfactorius
Insula
Temporal lobt
Inferior frontal gyrui
Fia. 743. — Coronal section through anterior cornua of lateral ventricles.
The claustrum (Figs. 742, 744) is a thin layer of gray substance, situated on the
lateral surface of the external capsule. Its transverse section is triangular, with
the apex directed upward. Its medial surface, contiguous to the external capsule,
is smooth, but its lateral surface presents ridges and furrows corresponding with
the gy ri s nd sulci of the insula, with which it is in close relationship. The claustrum
is regarded as a detached portion of the gray substance of the insula, from which
it is separated by a layer of white fibers, the capsula extrema (bayid of Baillarger).
Its cells are small and spindle-shaped, and contain yellow pigment; they are similar
to those of the deepest layer of the cortex.
The nucleus amygdalae (amygdala) (Fig. 741) , is an ovoid gray mass, situated at the
lower end of the roof of the inferior cornu. It is merely a localized thickening of the
836
NEUROLOGY
gray cortex, continuous with that of the uncus; in front it is continuous with the
putamen, behind with the stria terminahs and the tail of the caudate nucleus.
The internal capsule {caysula interna) (Figs. 745, 746) is a flattened band of white
fibers, between the lentiform nucleus on the lateral side and the caudate nucleus
and thalamus on the medial side. In horizontal section (Figs. 742) it is seen to be
somewhat abruptly curved, with its convexity inward; the prominence of the curve
is called the genu, and projects between the caudate nucleus and the thalamus.
The portion in front of the genu is termed the frontal part, and separates the len-
tiform from the caudate nucleus; the portion behind the genu is the occipital part,
and separates the lentiform nucleus from the thalamus.
Corpus callosum
Anterior cornu
Cavity of septum
pellucidum
Columns of
fornix
Anterior
commissure
Third ventricle.
Optic
chiasma
Caudate nucleus
^ • Internal capsvle
Putamen
^ — Globus pallidus
-M — Claustrum
-—Insula
FiQ. 744. — Coronal section of brain through anterior commissure.
The frontal part of the internal capsule contains: (1) fibers running from the
thalamus to the frontal lobe; (2) fibers connecting the lentiform and caudate
nuclei; (3) fibers connecting the cortex with the corpus striatum; and (4) fibers
passing from the frontal lobe through the medial fifth of the ba.se of the cerebral
peduncle to the nuclei pontis. The fibers in the region of the genu are named
the geniculate fibers; they originate in the motor part of the cerebral cortex, and,
after passing downward through the base of the cerebral peduncle with the cerebro-
spinal fibers, undergo decussation and end in the motor nuclei of the cranial
nerves of the opposite side. The anterior two-thirds of the occipital part of the
internal capsule contains the cerebrospinal fibers, which arise in the motor area
of the cerebral cortex and, passing downward through the middle three-fifths of
the base of the cerebral peduncle, are continued into the pyramids of the medulla
oblongata. The posterior third of the occipital part contains: (1) sensory fibers,
largely derived from the thalamus, though some may be continued upward from
THE FORE-BRAIN OR PROSENCEPHALON
837
the medial lemniscus; (2) the fibers of optic radiation, from the lower visual centers
to the cortex of the occipital lobe; (3) acoustic fibers, from the lateral lemniscus to
the temporal lobe; and (4) fibers which pass from the occipital and temporal lobes
to the nuclei pontis.
The fibers of the internal capsule radiate widely as they pass to and from the
various parts of the cerebral cortex, forming the corona radiata (Fig. 745) and
intermingling with the fibers of the corpus callosum.
^ The external capsule (capsula externa) (Fig. 742) is a lamina of white substance,
situated lateral to the lentiform nucleus, between it and the claustrum, and con-
tinuous with the internal capsule below and behind the lentiform nucleus. It
probably contains fibers derived from the thalamus, the anterior commissure, and
the subthalamic region.
R. oculomotor nerve
L. oculomotor nerve
Superior peduncle
Pyramid
Olive
Fig. 745. — Dissection showing the course of the cerebrospinal fibers. (E. B. Jamieson.)
Inferior peduncle
The substantia innominata of Meynert is a stratum consisting partly of gray and
partly of white substance, which lies below the anterior part of the thalamus
and lentiform nucleus. It consists of three layers, superior, middle, and inferior.
The superior layer is named the ansa lentiformis, and its fibers, derived from the
medullary lamina of the lentiform nucleus, pass medially to end in the thalamus
and subthalamic region, while others are said to end in the tegmentum and red
nucleus. The middle laver consists of nerve cells and nerve fibers; fibers enter it
from the parietal lobe through the external capsule, while others are said to con-
nect it with the medial longitudinal fasciculus. The inferior layer forms the main
part of the inferior stalk of the thalamus, and connects this body with the temporal
lobe and the insula.
The stria terminalis {toniia semicircularis) is a narrow band of white substance
situated in the depression between the caudate nucleus and the thalamus. Ante-
riorly, its fibers are partly continued into the column of the fornix; some, however,
pass over the anterior commissure to the gray substance between the caudate
838
NEUROLOGY
THALAMO-
FRONTAL
TRACT
geniculate
portion of
motor tract
(for muscles
of face and
TONGUE
nucleus and septum pellucidum, while others are said to enter the caudate nucleus.
Posteriorly, it is continued into the roof of the inferior cornu of the lateral ventricle,
at the extremity of which it enters the nucleus amygdalae. Superficial to it is a
large vein, the terminal vein {vein of the corpus striatum), which receives numerous
tributaries from the corpus striatum and thalamus; it runs forward to the inter-
ventricular foramen and there joins with the vein of the choroid plexus to form
the corresponding internal cerebral
vein. On the surface of the ter-
minal vein is a narrow white band,
named the lamina affixa.
The Fornix (Figs. 720, 747, 748)
is a longitudinal, arch-shaped lam-
ella of white substance, situated
below the corpus callosum, and
continuous with it behind, but
separated from it in front by the
septum pellucidum. It may be
described as consisting of two
symmetrical bands, one for either
heinisphere. The two portions are
not united to each other in front
and behind, but their central parts
are joined together in the middle
line. The anterior parts are called
the columns of the fornix; the inter-
mediate united portions, the body;
and the posterior parts, the crura.
The body (corpus fornicis) of the
fornix is triangular, narrow in front,
and broad behind. The medial part
of its upper surface is connected to
the septum pellucidum in front and
to the corpus callosum behind. The
lateral portion of this surface forms
part of the floor of the lateral ven-
tricle, and is covered by the ven-
tricular epithelium. Its lateral edge
overlaps the choroid plexus, and is
continuous with the epithelial cov-
ering of this structure. The under
surface rests upon the tela chori-
oidea of the third ventricle, which
separates it from the epithelial roof
of that cavity, and from the medial
portions of the upper surfaces of the
thalami. Below, the lateral portions
of the body of the fornix are joined
by a thin triangular lamina, named the psalterium {hjra). This lamina contains
some transverse fibers which connect the two hippocampi across the middle line
and constitute the hippocampal commissure. Between the psalterium and the corpus
callosum a horizontal cleft, the so-called ventricle of the fornix {ventricle of Verga),
is sometimes found.
The columns (columna fornicis; anterior pillars; fornicolumns) of the fornix arch
downward in front of the interventricular foramen and behind the anterior commis-
FlG. 746. — Diagram of the tracts in the internal capsule.
Motor tract red. The sensory tract (blue) is not direct, but
formed of neurons receiving impulses from below in the thala-
mus and transmitting them to the cortex. The optic radiation
(occipitothalamic) is shown in violet.
THE FORE-BRAIN OR PROSENCEPHALON
839
sure, and each descends through the gray substance in the lateral wall of the third
ventricle to the base of the brain, where it ends in the corpus mammillare. From
the cells of the corpus mammillare the thalamomammillary fasciculus {bundle of Vicq
. PILLARS
FORNIX
UNCUS
H>PPOCAMP0S
Fig. 7^7.— D
iagram of the fornix. (Spitzka.^
Cavity of septum pdlucidum
Optic chiasma
Optic nerve
Tuber cinereum
Optic tract
Corpora
mammiUaria
Corpus
callosum
(under surface)
Fimbria
hippocampi
Fia. 748. — The fornix and corpus callosum from below. (From a specimen in the Department of Human
Anatomy of the University of Oxford.)
d'Azyr) takes origin and is prolonged into the anterior nucleus of the thalamus.
The column of the fornix and the thalamomammillary fasciculus together form a loop
resembling the figure 8, but the continuity of the loop is broken in the corpus
840 NEUROLOGY
mammillare. The column of the fornix is joined by the stria medullaris of the pineal
body and by the superficial fibers of the stria terminalis, and is said to receive
also fibers from the septum pellucidum. Zuckerkandl describes an olfactory fascic-
ulus \Vhich becomes detached from the main portion of the column of the fornix,
and passes downward in front of the anterior commissure to the base of the brain,
where it divides into two bundles, one joining the medial stria of the olfactory
tract; the other joins the subcallosal gyrus, and through it reaches the hippocampal
gyrus.
The crura {cms fornicis; posterior pillars) of the fornix are prolonged backward
from the body. They are flattened bands, and at their commencement are inti-
mately connected with the under surface of the corpus callosum. Diverging from
one another, each curves around the posterior end of the thalamus, and passes
downward and forward into the inferior cornu of the lateral ventricle (Fig. 750).
Here it lies along the concavity of the hippocampus, on the surface of which some
of its fibers are spread out to form the alveus, while the remainder are continued
as a narrow white band, the fimbria hippocampi, which is prolonged into the uncus
of the hippocampal gyrus. The inner edge of the fimbria overlaps the fascia
dentata hippocampi {dentate gyrus) (page 827), from which it is separated by the
fimbriodentate fissure ; from its lateral margin, which is thin and ragged, the ventric-
ular epithelium is reflected over the choroid plexus as the latter projects into the
chorioidal fissure.
Interventricular Foramen {foramen of Monro). — Between the columns of the fornix
and the anterior ends of the thalami, an oval aperture is present on either side:
this is the interventricular foramen, and through it the lateral ventricles communi-
cate with the third ventricle. Behind the epithelial lining of the foramen the choroid
plexuses of the lateral ventricles are joined across the middle line.
The Anterior Commissure {precommissure) is a bundle of white fibers, connecting
the two cerebral hemispheres across the middle line, and placed in front of the
columns of the fornix. On sagittal section it is oval in shape, its long diameter
being vertical and measuring about 5 mm. Its fibers can be traced lateralward
and backward on either side beneath the corpus striatum into the substance of
the temporal lobe. It serves in this way to connect the two temporal lobes, but
it also contains decussating fibers from the olfactorv tracts.
The Septum Pellucidum {septum lucid urn) (Fig. 720) is a thin, vertically placed
partition consisting of two laminse, separated in the greater part of their extent
by a narrow chink or interval, the cavity of the septum pellucidum. It is attached,
above, to the under surface of the corpus callosum; below, to the anterior part of
the fornix behind, and the reflected portion of the corpus callosum in front. It is
triangular in form, broad in front and narrow behind; its inferior angle corre-
sponds with the upper part of the anterior commissure. The lateral surface of each
lamina is directed toward the body and anterior cornu of the lateral ventricle,
and is covered by the ependyma of that cavity.
The cavity of the septum pellucidum {cavu772 septi pellucidi; pseudocele; fifth
ventricle) is generally regarded as part of the longitudinal cerebral fissure, which
has become shut oft" by the union of the hemispheres in the formation of the corpus
callosum above and the fornix below. Each half of the septum therefore forms
part of the medial wall of the hemisphere, and consists of a medial layer of gray
substance, derived from that of the cortex, and a lateral layer of white substance
continuous with that of the cerebral hemispheres. This cavity is not developed
from the cavity of the cerebral vesicles, and never communicates with the ventricles
of the brain.
The Choroid Plexus of the Lateral Ventricle {plexus cJwrioideus teniriculus later-
alis; paraplexus) (Fig. 750j is a highly vascular, fringe-like process of pia mater,
which projects into the ventricular cavity. The plexus, however, is everywhere
THE FORE-BRAIN OR PROSENCEPHALON
841
covered by a layer of epithelium continuous with the epithehal lining of the
ventricle. It extends from the interventricular foramen, where it is joined
with the plexus of the opposite ventricle, to the end of the inferior cornu. The
part in relation to the body of the ventricle forms the vascular fringed margin
of a triangular process of pia mater, named the tela chorioidea of the third
ventricle, and projects from under cover of the lateral edge of the fornix. It
lies upon the upper surface of the thalamus, from which the epithelium is reflected
over the plexus on to the edge of the fornix (Fig. 723). The portion in relation
to the inferior cornu lies in the concavity of the hippocampus and o\'erlaps the
fimbria hippocampi : from the lateral edge of the fimbria the epithelium is reflected
over the plexus on to the roof of the cornu (Fig. 749). It consists of minute and
highly vascular villous processes, each with an afferent and an efferent vessel. The
arteries of the plexus are: (a) the anterior choroidal, a branch of the internal carotid,
which enters the plexus at the end of the inferior cornu; and (b) the posterior
choroidal, one or two small branches of the posterior cerebral, which pass forward
under the splenium. The veins of the choroid plexus unite to form a tortuous vein,
which courses from behind forward to the interventricular foramen and there joins
with the terminal vein to form the corresponding internal cerebral vein.
Tail of cavdate nucleus
Pia mater
Finibria
Fimbriodentate
fissure
Alveus
Fascia dentata
hippocampi
Dentate fissure
Fig. 74'J
Choroid plextis
Epithelial lining of ventricle
-Coronal section of inferior horn of lateral ventricle. (Diagrammatic.)
When the choroid plexus is pulled aw^ay, the continuity between its epithelial
covering and the epithelial lining of the ventricle is severed, and a cleft-like space
is produced. This is named the choroidal fissure; like the plexus, it extends from
the interventricular foramen to the end of the inferior cornu. The upper part of
the fissure, i. e., the part nearest the interveiitricular foramen is situated between
the lateral edge of the fornix and the upper surface of the thalamus; farther back
at the beginning of the inferior cornu it is between the commencement of the fim-
bria hippocampi and the posterior end of the thalamus, while in the inferior cornu it
lies between the fimbria in the floor and the stria terminalis in the roof of the cornu.
The tela chorioidea of the third ventricle (tela chorioidea ventriculi tertii; velum
interpositum) (Fig. 750) is a double fold of pia mater, triangular in shape, which
lies beneath the fornix. The lateral portions of its lower surface rest upon the
thalami, while its medial portion is in contact with the epithelial roof of the third
ventricle. Its apex is situated at the interventricular foramen ; its base corresponds
with the splenium of the corpus callosum, and occupies the interval between that
structure above and the corpora quadrigemina and pineal body below. This
842
NEUROLOGY
interval, together with the lower portions of the choroidal fissures, is sometimes
spoken of as the transverse fissure of the brain. At its base the two layers of the
velum separate from each other, and are continuous with the pia mater investing
the brain in this region. Its lateral margins are modified to form the highly vas-
cular choroid plexuses of the lateral ventricles. It is supplied by the anterior and
posterior choroidal arteries already described. The veins of the tela chorioidea are
named the internal cerebral veins (venoe Galeni) ; they are two in number, and run
backward between its layers, each being formed at the interventricular foramen by
the union of the terminal vein with the choroidal vein. The internal cerebral
veins unite posteriorly in a single trunk, the great cerebral vein {vena magna Galeni),
which passes backward beneath the splenium and ends in the straight sinus.
Fig.
750. — Tela chorioidea of the third veulriult;, aud the cuuruid plexus of the left lateral ventricle, exposed
from above.
Structure of the Cerebral Hemispheres. — The cerebral hemispheres are composed
of gray and white substance: the former covers their surface, and is termed the
cortex; the latter occupies the interior of the hemispheres.
The white substance consists of medullated fibers, varying in size, and arranged
in bundles separated by neuroglia. They may be divided, according to their
course and connections, into three distinct systems. (1) Projection fibers connect
the hemisphere with the lower parts of the brain and with the medulla spinalis.
(2) Transverse or commissural fibers unite the two hemispheres. (3) Association
fibers connect different structures in the same hemisphere; these are, in many
THE FORE-BRAIN OR PROSENCEPHALON
843
instances, collateral branches of the projection fibers, but others are the axons
of independent cells.
1 The projection fibers consist of efferent and afferent fibers unitin^^ the cortex
with the lower parts of the brain and with the medulla spinalis. The principal
efferent strands are: (1) the motor tract, occupying the genu and anterior two-thirds
of the occipital part of the internal capsule, and consisting of (a) the geniculate
fibers, which decussate and end in the motor nuclei of the cranial nerves of the
opposite side; and (b) the cerebrospinal fibers, which are prolonged through the
pyramid of the medulla oblongata into the medulla spinalis: (2) the corticopontine
fibers, ending in the nuclei pontis. The chief afferent fibers are: (1) those of the
lemniscus which are not interrupted in the thalamus; (2) those of the superior
cerebellar peduncle which are not interrupted in the red nucleus and thalamus;
(3) numerous fibers arising within the thalamus, and passing through its stalks
to the different parts of the cortex (page 810) ; (4) optic and acoustic fibers, the
former passing to the occipital, the latter to the temporal lobe.
2. The transverse or commissural fibers connect the two hemispheres. They
include: (a) the transverse fibers of the corpus callosum, (6) the anterior commissure,
(c) the posterior commissure, and (d) the lyra or hippocampal commissure; they
have already been described.
Fig. 751. — Diagram showing principal systems of association fibers in the cerebrum.
3. The association fibers (Fig. 751) unite different parts of the same hemi-
sphere, and are of two kinds: (1) those connecting adjacent gyri, short association
fibers ; (2) those passing between more distant parts, long association fibers.
The short association fibers lie immediately beneath the gray substance of the
cortex of the hemispheres, and connect together adjacent gyri.
The long association fibers include the following: {a) the uncinate fasciculus;
(6) the cingulum; (c) the superior longitudinal fasciculus; {d) the inferior longi-
tudinal fasciculus; {e) the perpendicular fasciculus; (/) the occipitofrontal
fasciculus; and {g) the fornix.
(a) The uncinate fasciculus passes across the bottom of the lateral fissure, and
unites the gyri of the frontal lobe with the anterior end of the temporal lobe.
(6) The cingulum is a band of white matter contained within the cingulate
gyrus. Beginning in front at the anterior perforated substance, it passes forward
and upward parallel with the rostrum, winds around the genu, runs backward above
the corpus callosum, turns around the splenium, and ends in the hippocampal gyrus.
844
NEUROLOGY
iV
(c) The superior longitudinal fascicidus passes backward from the frontal lobe
above the lentiform nucleus and insula; some of its fibers end in the occipital
lobe, and others curve downward and forward into the temporal lobe.
Fig. 752. — Dissection of cortex and brain-stem showing association fibers and island of Reil after removal of its super-
ficial gray substance.
(d) The inferior longitudinal fasciculus connects the temporal and occipital
lobes, running along the lateral walls of the inferior and posterior cornua of the
lateral ventricle.
Olivo-cerebellar fibers
Nuclei grac. et
cuneatus
Vent, spinocere-
bellar fas.
Fig. 753. — Deep dissection of cortex and brain-stem.
{e) The perpendicular fasciculus runs vertically through the front part of the
occipital lobe, and connects the inferior parietal lobule with the fusiform gyrus.
(/) The occipitofrontal fasciculus passes backward from the frontal lobe, along
the lateral border of the caudate nucleus, and on the mesial aspect of the corona
THE FORE-BRAIX OR PROSENCEPHALON 845
radiata; its fibers radiate in a fan-like manner and pass into the occipital and tem-
poral lobes lateral to the posterior and inferior cornua. Dejerine regards the fibers
of the tapetum as being derived from this fasciculus, and not from the corpus
callosum.
(g) The fornix connects the hippocampal gyrus with the corpus mammillare
and, by means of the thaiamomammillary fasciculus, with the thalamus (see page
839). Through the fibers of the hippocampal commissure it probably also unites
the opposite hippocampal gyri.
The gray substance of the hemisphere is divided into: (1) that of the cerebral
cortex, and (2) that of the caudate nucleus, the lentiform nucleus, the claustrum,
and the nucleus amygdalae.
Structure of the Cerebral Cortex (Fig. 754).— The cerebral cortex differs in thickness and
structure in different parts of the hemisphere. It is thinner in the occipital region than in the
anterior and posterior central gyri, and it is also much thinner at the bottom of the sulci than
on the top of the g>-ri. Again, the minute structure of the anterior central differs from that of
the posterior central gyrus, and areas possessing a specialized type of cortex can be mapped out
in the occipital lobe.
On examining a section of the cortex with a lens, it is seen to consist of alternating white and
gray layers thus disposed from the surface inward: (1) a thin layer of white substance; (2) a
layer of gray substance; (3) a second white laj^er (outer band of Baillarger or band of Gennari);
(4) a second gray layer; (5) a third white layer [inner band of Baillarger); (6) a third gray layer,
which rests on the medullary substance of the gyrus.
The cortex is made up of nerve cells of varying size and shape, and of nerve fibers which are
either medullated or naked axis-cylinders, imbedded in a matrix of neuroglia.
Nerve Cells. — According to Cajal, the nerve cells are arranged in four layers, named from the
surface inwartl as follows: (1) the molecular layer, (2) the layer of small pyramidal cells, (3)
the layer of large pyramidal cells, (4) the layer of polymorphous cells.
The Molecular Layer. — In this layer the cells are polygonal, triangular, or fusiform in shape.
Each polygonal cell gives off some four or five dendrites, while its axon may arise direct!}'' from
the cell or from one of its dendrites. Each triangular cell gives off two or three dendrites, from
one of which the axon arises. The fusiform cells are placed with their long axes parallel to the
surface and are mostly bipolar, each pole being prolonged into a dendrite, which runs horizontally
for some distance and furnishes ascending branches. Their- axons, two or thi'ee in number, arise
from the dendrites, and, like them, take a horizontal course, giving off numerous ascending
collaterals. The distribution of the axons and dendrites of all three sets of cells is hmited to the
molecular layer.
The Layer of Small and the Layer of Large Pyramidal Cells. — The cells in these two layers
may be studied together, since, with the exception of the difference in size and the more super-
ficial position of the smaller cells, they resemble each other. The average length of the small
cells is from 10 to 15,"; that of the large cells from 20 to 30". The body of each cell is pyramidal
in shape, its base being directed to the deeper parts and its apex toward the surface. It contains
granular pigment, and stains deeply with ordinary reagents. The nucleus is of large size, and
round or oval in shape. The base of the cell gives off the axis cylinder, and this runs into the
central white substance, giving off collaterals in its course, and is distributed as a projection,
commissural, or association fiber. The apical and basal parts of the cell give off dendrites; the
apical dendrite is directed toward the surface, and ends in the molecular layer by dividing into
numerous branches, all of which may be seen, when prepared by the silver or methylene-blue
method, to be studded with projecting bristle-like processes. The largest p>Tamidal cells are
found in the upper part of the anterior central g\Tus and in the paracentral lobule; they are
often arranged in groups or nests of from three to five, and are named the gia?if cells of Betz.
In the former situation they may exceed 50m in length and 40,u in breadth, while in the para-
central lobule the}' may attain a length of 65m.
Layer of Polymorphous Cells. — The cells in this layer, as their name implies, are very irregular
in contour; they may be fusiform, oval, triangular, or star-shaped. Their dendrites are directed
outward, but do not reach so far as the molecular layer; their axons pass into the subjacent white
matter.
There are two other kinds of cells in the cerebral cortex. They are: (a) the cells of Golgi,
the a.xons of which divide immediately after their origins into a large number of branches, which
are directed toward the surface of the cortex; ib) the cells of Martinotti, which are chiefly found
in the polymorphous layer; their dendrites are short, and may have an ascending or descending
course, while their axons pass out into the molecular layer and form an extensive horizontal
arborization.
846
NEUROLOGY
Nerve Fibers. — These fill up a large part of the intervals between the cells, and may be medul-
lated or non-medullated — the latter comprising the axons of the smallest pyramidal cells and
the cells of Golgi. In their direction the fibers may be either tangential or radial. The tangential
fibers run parallel to the surface of the hemisphere, intersecting the radial fibers at a right angle.
They constitute several strata, of which the following are the more important: (1) a stratum
of white fibers covering the superficial aspect of the molecular layer (plexus of Exner) ; (2) the
band of Bechterew, in the outer part of the layer of small pyramidal cells; (3) the band of Gennari
Molecular
layer
Layer of
small
'pyramidal
cells
Layer of
large
•pyramidal
cells
Layer of
polymorphous
cells
"'Plexus of Exner
Band of Bechterew
Outer hand of Bail-
larger, or hand of
Genjiari
Fig. 754. — Cerebral cortex.
- Vertical fibers ,
Internal band of
Baillarger
Deep tangential
fibers
White medullary
substance
(Poirier.) To the left, the groups of cells; to the right, the systems of fibers. Quite
to the left of the figure a sensory nerve fiber is shown.
or external band of Baillarger, running through the layer of large pyramidal cells; (4) the internal
band of Baillarger, between the layer of large pyramidal cells and the polymorphous layer; (5)
the deep tangential fib'ers, in the lower part of the polymorphous layer. The tangential fibers
consist of (a) the collaterals of the pyramidal and polymorphous cells and of the cells of Martinotti;
(6) the branching axons of Golgi's cells; (c) the collaterals and terminal arborizations of the
projection, commissural, or association fibers. The radial fibers. — Some of these, viz., the axons
of the pyramidal and polymorphous cells, descend into the central white matter, while others,
THE FORE-BRAIN OR PROSENCEPHALON
847
the terminations of the projection, commissural, or association fibers, ascend to end in the cortex.
The axons of the cells of Martinotti are also ascending fibers.
Special Types of Cerebral Cortex.— It has been already pointed out that the minute structure
of the cortex differs m different regions of the hemisphere; and A. W. Campbell' has endeavored
to prove, as the result of an exhaustive examination of a series of human and anthropoid brains,
"that there exists a direct correlation between physiological function and histological structure."
The principal regions where the "typical" structure is departed from will now be referred to.
1. In the calcarine fissure and the gyri bounding it, the internal band of Baillargcr is absent,
while the band of Gennari is of considerable thickness, and forms a characteristic feature of this
region of the cortex. If a section be examined microscopically, an additional layer of cells is
seen to be interpolated between the molecular layer and the layer of small pyramidal cells. This
extra layer consists of two or three strata of fusiform cells, the long axes of which are at right
angles to the surface; each cell gives off two dendrites, external and internal, from the latter of
which the axon arises and passes into the white central substance. In the layer of small pyramidal
cells, fusiform cells, identical with the above, are seen, as well as ovoid or star-like cells with
ascending axons (cells of Martinotti). This is the visual area of the cortex, and it has been shown
by J. S. Bolton^ that in old-standing cases of optic atrophy the thickness of Gennari's band is
reduced by nearly 50 per cent.
White suhitnnce dor-tnl part)
.Neuroglia
White avhstance (ventral
■part)
■^'rs^'- Medullary layer
_^_ ^i^-^j^,;^^."Ti
.. '''""-*^!r"'^'~S^\iu^'""''^^^^- J'r- ^ft\--^iitral cells
Molecular
layer
Glomerular layer
Layer of olfactory nerve fibers
Fig. 755. — Coronal section of olfactory bulb. (Schwalbe.)
A. W. Campbell says: "Histologically, two distinct types of cortex can be made out in the
occipital lobe. The first of these coats the walls and bounding convolutions of the calcarine
fissure, and is distinguished by the well-known line of Gennari or Vicq d'Azyr; the second area
forms an investing zone a centimetre or more broad around the first, and is characterized by a
remarkable wealth of fibers, as well as by curious pyriform cells of large size richly stocked with
chromophilic elements — cells which seem to have escaped the observation of Ram6n y Cajal,
Bolton, and others who have worked at this region. As to the functions of these two regions
there is abundant evidence, anatomical, embryological, and pathological, to show that the first
or calcarine area is that to which visual sensations primarily pass, and we are gradually obtain-
ing proof to the effect that the second investing area is constituted for the interpretation and
further elaboration of these sensations. These areas therefore deserve the names visuo-sensory
and visuo-psychic."
2. The anterior central gyrus is characterized by the presence of the giant cells of Betz and
by "a wealth of nerve fibers immeasurably superior to that of any other part" (Campbell), and
in these respects differs from the posterior central gyrus. These two gyri, together with the
paracentral lobule, were long regarded as constituting the "motor areas" of the hemisphere;
but Sherrington and Gruiibaum have shown^ that in the chimpanzee the motor area never extends
on to the free face of the posterior central gyrus, but occupies the entire length of the anterior
central gyrus, and in most cases the greater part or the whole of its width. It extends into the
depth of the central sulcus, occupying the anterior wall, and in some places the floor, and in
some extending even into the deeper part of the posterior wall of the sulcus.
' Histological Studies on the Localization of Cerebral Function, Cambridge University Press
- Philosophical Transactions of Royal Society, Series B, cxciii, 165.
^ Transactions of the Pathological Society of London, vol. liii.
848
NEUROLOGY
3. In the hippocampus the molecular layer is very thick and contains a large number of Golgi
cells. It has been divided into three strata: (a) s. convolutum or s. granulosum, containing
many tangential fibers; (b) s. lacunosum, presenting numerous vascular spaces; (c) s. radiatum,
exhibiting a rich plexus of fibrils. The two layers of pyramidal cells are condensed into one,
and the cells are mostly of large size. The axons of the ceUs in the poljmiorphous layer may
run in an ascending, a descending, or a horizontal direction. Between the polymorphous layer
and the ventricular ependyma is the white substance of the alveus.
4. In the fascia dentata hippocampi or dentate gyrus the molecular layer contains some pyrami-
dal cells, while the layer of pyramidal cells is almost entirely represented by small ovoid cells.
5. The Olfactory Bulb. — In many of the lower animals this contains a cavity which communi-
cates through the olfactory tract with the lateral ventricle. In man the original cavity is fiUed
up by neuroglia and its wall becomes thickened, but much more so on its ventral than on its
dorsal aspect. Its dorsal part contains a small amount of gray and white substance, but it is
scanty and ill-defined. A section through the ventral part (Fig. 755) shows it to consist of the
followmg layers from without inward:
FiQ. 756. — Areas of localization on lateral surface of heniispliere. Motor area in red. Area of general sensations
in blue. Auditory area in green. Visual area in yellow. The psychic portions are in lighter tints.
1. A layer of oKactory nerve fibers, which are the non-medullated axons prolonged from the
olfactory cells of the nasal cavity, and reach the bulb by passing through the cribriform plate
of the ethmoid bone. At first they cover the bulb, and then penetrate it to end by forming
synapses with the dendrites of the mitral cells, presently to be described.
2. Glomerular Layer. — This contains numerous spheroidal reticulated enlargements, termed
glomeruli, produced by the branching and arborization of the processes of the olfactory nerve
fibres with the descending dendrites of the mitral cells.
3. Molecular Layer. — This is formed of a matrix of neuroglia, imbedded in which are the mitral
cells. These cells are pyramidal in shape, and the basal part of each gives off a thick dendrite
which descends into the glomerular layer, where it arborizes as indicated above, and others which
interlace with similar dendrites of neighboring mitral cells. The axons pass through the next
layer into the white matter of the bulb, and after becoming bent on themselves at a right angle,
are continued into the olfactory tract.
4. Nerve Fiber Layer. — This lies next the central core of neuroglia, and its fibers consist of
the axons or afferent processes of the mitral cells passing to the brain; some efferent fibers are,
however, also present, and end in the molecular layer, but nothing is known as to their exact
origin.
Weight of the Encephalon. — The average weight of the brain, in the adult male, is about 1380
gms.; that of the female, about 1250 gms. In the male, the maximum weight out of 278 cases
was 1840 gms. and the minimum weight 964 gms. The maximum weight of the adult female
brain, out of 191 cases, was 1585 gms. and the minimum weight 879 gms. The brain increases
rapidly during the first four years of life, and reaches its maximum weight by about the twentieth
year. As age advances, the brain decreases slowly in weight; in old age the decrease takes place
more rapidly, to the extent of about 28 gms.
COMPOSITION AND CENTRAL CONNECTIONS OF SPINAL NERVES 849
The human brain is heavier than that of any of the lower animals, except the elephant and
whale. The brain of the former weighs from 3.5 to 5.4 kilogm., and that of a whale, in a speci-
men 19 metres long, weighed rather more than 6.7 kilogm.
Cerebral Localization. — Physiological and pathological research have now gone far to prove
that a considerable part of the surface of the brain may be mapped out into a series of more
or less definite areas, each of which is intimately connected with some well-defined function.
The chief areas are indicated in Figs. 756 and 757.
Motor Areas. — The motor area occupies the anterior central and frontal gyri and the para-
central lobule. The centers for the lower hmb are located on the uppermost part of the anterior
central gyrus and its continuation on to the paracentral lobule; those for the trunk are on the
upper portion, and those for the upper hmb on the middle portion of the anterior central gyrus.
The facial centers are situated on the lower part of the anterior central gyrus, those for the tongue,
larynx, muscles of mastication, and pharynx on the frontal operculum, while those for the head
and neck occupy the posterior end of the middle frontal gyrus.
Fig. 757. — Areas of localization on medial surface of hemisphere. Motor area in red. Area of general sensations
in blue. Visual area in yellow. Olfactory area in purple. The psychic portions are in lighter tints.
Sensory Areas. — Tactile and temperature senses are located on the posterior central gyrus,
while the sense of form and sohdity is on the superior parietal lobule and precuneus. With
regard to the special senses, the area for the sense of taste is probably related to the uncus and
hippocampal gyrus. The auditory area occupies the middle third of the superior temporal gyrus
and the adjacent gyri in the lateral fissure; the visual area, the calcarine fissure and cuneus; the
olfactory area, the rhinencephalon. As special centers of much importance may be noted: the
emissive center for speech on the left inferior frontal and anterior central gyri (Broca) ; the auditory
receptive center on the tran.sverse and superior temporal gjTi, and the visual receptive center
on the lingual gyrus and cuneus.
COMPOSITION AND CENTRAL CONNECTIONS OF THE SPINAL NERVES.
The typical spinal nerve consists of at least four types of fibers, the somatic sensory,
sympathetic afferent or sensory, somatic motor and sympathetic efferent or pregan-
glionic. The somatic sensory fibers, afferent fibers, arise from cells in the spinal
ganglia and are fomid in all the spinal nerves, except occasionally the first cervical,
and conduct impulses of pain, touch and temperature from the surface of the body
through the posterior roots to the spinal cord and impulses of muscle sense, tendon
sense and joint sense from the deeper structures. The sympathetic afterent fibers,
conduct sensory impulses from the viscera through the rami communicantes and
posterior" roots to the spinal cord. They are probably limited to the white rami
connected with the spinal nerves in two groups, viz., the first thoracic to the second
54
850
NEUROLOGY
lumbar and the second sacral to the fourth sacral nerves. The somatic motor
fibers, efferent fibers, arise from cells in the anterior column of the spinal cord and
pass out through the anterior roots to the voluntary muscles. The sympathetic
efferent fibers, probably arise from cells in the lateral column or the base of the
anterior column and emerge through the anterior roots and white rami communi-
cantes. These are preganglionic fibers which end in various sympathetic ganglia
from which postganglionic fibers conduct the motor impulses to the smooth muscles
of the viscera and vessels and secretory impulses to the glands. These fibers are
also limited to two regions, the first thoracic to the second lumbar and the second
sacral to the fourth sacral nerves.
The afferent fibers which pass into the spinal cord establish various types of
connections, some within the cord itself for spinal reflexes, others for reflexes con-
nected with higher centers in the brain, while still others conduct impulses of
conscious sensation by a series of neurons to the cerebral cortex.
■spina' lemniscus
correlation neuronel
funiculus dorsalis
( ) spg^
correlation neurone 2
^T) sp.g.2
sKin
spg.5
correJation neurone3
so a.4-
Fig. 758. — Diagram of the spinal cord reflex apparatus. Some of the connections of a single afferent neuron from
the skin (d.r.2) are indicated: d.r.2, dorsal root from second spinal ganglion; m, muscles; sp.g.l to sp.oA, spinal
ganglia; v.r.l^ to v.rA, ventral roots. (After Herrick.)
The Intrinsic Spinal Reflex Paths. — The collaterals and terminals of the ascend-
ing and descending branches of the posterior root fibers which leave the fasciculus
cuneatus to enter the gray matter of the spinal cord end in various ways. Many end
in the dorsal column, some near its apex, others in the substance of Rolando, others
in the intermediate region between the dorsal and ventral columns, others traverse
the whol 3 thickness of the gray matter to reach the ventral column, others end in the
dorsal nucleus, and others pass through the gray commissure to the dorsal column
of the opposite side. All of these collaterals and terminals end in connection with
cells or dendrites of cells in the gray columns. The axons of these cells have various
destinations, some pass out into the lateral and ventral funiculi and turn upward
to reach the brain. Those concerned with the intrinsic spinal reflexes come into
relation either directly or indirectly with motor cells in the anterior column. It is
very unlikely that either the terminals or collaterals of the dorsal root fibers effect
simple direct connections with the motor cells of the ventral column, there is at
least one if not se\-eral intercalated neurons in the path. These intercalated or
correlation neurons may have short axons that do not pass out of the gray matter
or the axons may pass out into the proper fasciculi and extend for varying distances
COMPOSITION AND CENTRAL CONNECTIONS OF SPINAL NERVES 851
up and dow-n or in both directions giving ofF collaterals and finally terminating in
the gray matter of the same or the opposite side. The shortest fibers of the proper
fasciculi lie close to the gray matter, the longest ones are nearer the porij)hery of
the proper fasciculi and are more or less intermingled with the long ascending and
descending fasciculi which occupy the more marginal regions of the spinal cord.
Each sensory neuron, with its ascending and descending branches, giving oft" as
it does many collaterals into the gray matter, each one of which may form a synapse
with one or several correlation neurons, is thus brought into relation with many
correlation neurons and each one of these in turn, with its ascending and descending
branches and their numerous collaterals, is brought into relation, either directly
or through the intercalation of additional correlation neurons, with great numbers
of motor cells in the anterior column. The great complexity of these so-called
simple reflex mechanisms, in the least complex portion of the nervous system the
spinal cord, renders them extremely difficult of exact analysis.
The association or correlation neurons are concerned not only with the reflex
mechanisms of the spinal cord but play an equally important role in the trans-
mission of impulses from the higher centers in the brain to the motor neurons of the
spinal cord.
The complex mechanisms just described are probably concerned not so much in
the contraction of individual muscles as in the complicated action of groups of
muscles concerned in the enormous number of movements, which the limbs and
trunk exhibit in the course of our daily life.
Sensory Pathways from the Spinal Cord to the Brain. — The posterior root fibers
conducting the impulses of consciaus muscle sense, tendon sense and joint sense,
those impulses which have to do with the coordination and adjustment of muscular
movements, ascend in the fasciculus gracilis and fasciculus cuneatus to the nucleus
gracilis and nucleus cuneatus in the medulla oblongata (Fig. 759).
In the nucleus gracilis and nucleus cuneatus synaptic relations are found with
neurons whose cell bodies are located in these nuclei and whose axons pass by way
of the internal arcuate fibers, cross in the raphe to the opposite side in the region
between the olives and turn abruptly upward to form the medial lemniscus or medial
fillet. The medial fillet passes upward in the ventral part of the formatio reticularis
through the medulla oblongata, pons and mid-brain to the principal sensory nucleus
of the ventro-lateral region of the thalamus. Here the terminals form synapses
with neurons of the third order whose axons pass through the internal capsule and
corona radiata to the somatic sensory area of the cortex in the post-central gyrus.
Fibers conducting the impulses of unconscious muscle sense pass to the cerebellum
partly by way of the fasciculus gracilis and fasciculus cuneatus to the nucleus
gracilis and nucleus cuneatus, thence neurons of the second order convey the
impulses either via the dorsal external arcuate fibers directly into the inferior
peduncle of the cerebellum or via the ventral external arcuate fibers which are
continued from the internal arcuate fibers through the ventral part of the raphe
and after crossing the midline emerge on the surface of the medulla in the ventral
sulcus between the p\Tamids or in the groove between the p\Tamid and the olive.
They pass over the lateral surface of the medulla and olive to reach the inferior
peduncle through which they pass to the cerebellum.
Other fibers conducting impulses of unconscious muscle sense pass upward in the
dorsal spinocerebellar fasciculus, which arises from cells in the nucleus dorsalis.
The posterior root fibers conducting these impulses pass into the fasciculus cuneatus
and the collaterals from them to the nucleus dorsalis are said to come almost
exclusiveh- from the middle area of the fasciculus cuneatus. They form by their
multiple division baskets about the individual cells of the nucleus dorsalis, each
fiber coming in relation with the bodies and dendrites of several cells. The axons
of the second order pass into the dorsal spinocerebellar fasciculus of the same side
852
NEUROLOGY
and ascend along the lateral surface of the spinal cord and medulla oblongata until
they arrive at the level of the olive, they then curve backward beneath the external
arcuate fibers into the inferior peduncle and pass into the cerebellum. Here they
give off collaterals to the dentate nucleus and finally terminate in the cortex of the
dorsal and superior portion of the vermis, partly on the same side, but to a great
Medial lemniscus
Sensory decussation
Fasciculus cunealus
Fascictdiis gracilis
Nucleus ciineaiiis
Nwcleus gracilis
— • Posterior nerve roots
Fig. 759. — The sensory tract. (Modified from Poirier.)
extent by way of a large commissure to the opposite side. The fibers lose their
myelin sheaths as they enter the gray substance and terminate by end ramifications
among the nerve cells and their processes. Some of the fibers are said to end in
the nucleus dentatus and the roof nuclei of the cerebellum (the nucleus globosus,
nucleus emboliformis and nucleus fastigius) and others pass through them to ter-
minate in the inferior vermis. A few fibers of the dorsal spinocerebellar fasciculus
COMPOSITION AND CENTRAL CONNECTIONS OF SPINAL NERVES 853
are said not to enter the inferior peduncle but to pass with the ventral spinocere-
belhir fascieukis. The cerebeHar reflex arc is supposed to be completed by the fibers
of the superior peduncle which pass from the cerebellum to the red imcleus of the
mid-brain where some of their terminals and collaterals form synapses with neurons
whose axons descend to the spinal cord in the rubrospinal fasciculus. The terminal
and collaterals of this fasciculus end either directly or indirectly about the motor
cells in the anterior column.
The ventral spinocerebellar fasciculus, since most of its fibers pass to the cere-
bellum, is also supposed to be concerned in the conduction of unconscious muscle
sense. The location of its cells of origin is uncertain. They are probably in or near
the dorsal nucleus of the same and the opposite side; various other locations are
given, the dorsal column, the intermediate zone of the gray matter and the central
portion of the anterior colunm. The neurons of the first order whose central fibers
enter the fasciculus cuneatus from the dorsal roots send collaterals and terminals
to form synapses with these cells. The fibers which come from the opposite gray
columns cross some in the white and some in the gray commissure and pass with
fibers from the same side through the lateral funiculus to the marginal region
ventral to the dorsal spinocerebellar fasciculus. The fasciculus begins about the
level of the third lumbar nerve and continues upward on the lateral surface of
the spinal cord and medulla oblongata until it passes under cover of the external
arcuate fibers. It passes just dorsal to the olive and above this joins the lateral
edge of the lateral lemniscus along which it runs, ventral to the roots of the trigem-
inal nerve, almost to the level of the superior coUiculus, it then crosses over the
superior peduncle, turns abruptly backward along its medial border, enters the
cerebellum with it and ends in the vermis of the same and the opposite side. Some
of its fibers are said to join the dorsal spinocerebellar fasciculus in the medulla
oblongata and enter the cerebellum through the inferior peduncle. A number of
fibers are said to continue upward in the dorsolateral part of the tegmentum as
far as the superior coUiculus and a few pass to the thalamus. They probably form
part of the sensory or higher reflex path.
The posterior root fibers conducting impulses of pain and temperature probably
terminate in the posterior column or the intermediate region of the gray matter
soon after they enter the spinal cord. The neurons of the second order are supposed
to pass through the anterior commissure to the superficial antero-lateral fasciculus
(tract of Gowers) and pass upward in that portion of it kno\^^^ as the lateral spino-
thalamic fasciculus. This fasciculus lies along the medial side of the ventral spino-
cerebellar fasciculus. It is stated by some authors that the pain fibers pass upward
in the antero-lateral ground bundles. In some of the lower mammals this pathway
carries the pain fibers upward by a series of neurons some of which cross to the
opposite side, so that in part there is a double path. In man, however, the lateral
spmothalamic fasciculus is probably the most important pathway. On reaching the
medulla these fibers continue upward through the formatio reticularis in the neigh-
borhood of the median fillet to the thalamus, probably its ventro-lateral region.
Whether higher neurons convey the pain impulses to the cortex through the internal
capsule is uncertain. The pathway is probably more complex and Head is of the
opinion that our sensations of pain are essentially thalamic. The pain and temper-
ature pathways in the lateral spinothalamic fasciculus are not so closely inter-
mingled but that one can be destroyed Avithout injury to the other.
Ransom suggests that the non-medullated fibers of the posterior roots, which
turn into Lissauer's tract and ascend or descend for short distances not exceeding
one or two segments anrl finally end in the substantia gelatinosa, are in part at
least pain fibers and that the fasciculus of Lissauer and the substantia gelatinosa
represent part of the mechanism for reflexes associated with pain conduction and
reception while the fibers to the higher centers pass up in the spinothalamic tract.
854 NEUROLOGY
The fibers of tactile discrimination, according to Head and Thompson, pass up in
the fascicukis cuneatus and t'ascicuhis gracilis of the same side and follow the path
of the muscle-sense fibers. The axons of the second order arising in the nucleus
cuneatus and gracilis cross with the internal arcuate fibers and ascend to the thalamus
with the medial lemniscus, thence by neurons of higher order the impulses are carried
to the somatic sensory area of the cortex through the internal capsule. The other
touch fibers, shortly after entering the spinal cord, terminate in the dorsal column
or intermediate gray matter. Neurons of the second order send their axons through
the anterior commissure to pass upward in the antero-lateral funiculus probably
in the ventral spinothalamic fasciculus. In the medulla they join or pass upward
in the neighborhood of the medial lemniscus to the thalamus and thence by neurons
of higher order to the somatic sensory area of the cortex.
The remaining ascending fasciculi form a part of the complex kno\\n as the super-
ficial antero-lateral fasciculus {trad of Gowers). The spinotectal fasciculus, as its
name indicates, is supposed to have its origin in the gray matter of tlie cord and
terminations in the superior anrl inferior (?) colliculi of the mid-brain serving for
reflexes between the cord and the visceral and auditory centers of the mid-brain.
The spino-olivary fasciculus {olivospinal; bulbospinai Ilelwegs bundle) is likewise
of unkno^^^l constitution and function; there is uncertainty even in regard to the
direction of its fibers.
Sympathetic afferent fibers (visceral afferent: viscerosensory; splanchnic afferent)
enter the spinal cord by the posterior roots of the thoracic and first two or three
lumbar nerves and the second to the fourth sacral nerves. The fibers pass to these
nerves from the peripheral s\Tnpathetic system through the white rami communi-
cantes. Some of the cell bodies of these afferent fibers are located in the spinal
ganglia and others are in the sympathetic ganglia. Some of the aft'erent sympa-
thetic fibers end about the cell bodies of somatic sensory neurons and visceral
impulses are thus transmitted to these neurons which contluct them as well as their
own special impulses to the spinal cord. Other sympathetic aft'erent neurons
whose cell bodies are located in the spinal ganglia send collaterals to neighboring
cells of somatic sensory neurons and thus have a double path of transmission to
the spinal cord. Such an arrangement provides a mechanism for some of the
referred pains.
These sympathetic aft'erent fibers presumably divide on entering the spinal cord
into ascending and descending branches. Their distribution and termination
within the spinal cord are unknown. Some of them probably e\'entually come into
relation with the sympathetic efterent fibers whose cell bodies are located in the
lateral cohunn. Our knowledge concerning both the termination and origin of
these fibers is very unsatisfactory.
The sympathetic efferent fibers {splanchnic motor; viscera-motor; preganglionic fibers)
are supposed to arise from cells in the intermediate zone between the dorsal
and ventral gray columns and in the intermedio-lateral column at the margin of
the lateral column. These preganglionic sympathetic fibers are not distributed
throughout the entire series of spinal nerves but are confined to two groups, the
thoraco-lumbar from the first thoracic to the second or third Imnbar nerves and
the sacral group from the second to the fourth sacral nerves. They pass out with
the anterior root fibers and through the rami communicantes to end in sympathetic
ganglia. The impulses are distributed from cells in these ganglia through post-
ganglionic fibers to the smooth muscles and glands. The thoraco-lumbar outflow
and the sacral outflow form two distinct functional groups which are considered
more fully under the sympathetic system.
COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 855
COMPOSITION AND CENTRAL CONNECTIONS OF THE CRANIAL NERVES.
The cranial nerves are more varied in their composition than the spinal nerves.
Some, for example, contain somatic motor fibers only, others contain the various
types of fibers found in the spinal nerves, namely, somatic motor, sxinpathetic
efferent, somatic sensory and sympathetic sensory. In addition there are included
the nerves of the special senses, namely, the nerves of smell, sight, hearing, equili-
bration and taste.
The Hypoglossal Nerve ( XII cranial) consists of somatic motor fibers only and
supplies the muscles of tiie tongue. Its axons arise from cells in the hjTpoglossal
nucleus and pass forward between the white reticular formation and the gray
reticular formation to emerge from the antero-lateral sulcus of the medulla. The
hypoglossal nuclei of the two sides are connected by many commissural fibers and
also by dendrites of motor cells which extend across the midline to the opposite
nucleus. The hypoglossal nucleus recei^•es either directly or indirectly numerous
collaterals and terminals from the opposite pATamidal tract (cortico-bulbar or cerebro-
bulbar fibers) which con\ey voluntary motor impulses from the cerebral cortex.
Many reflex collaterals enter the nucleus from the secondary sensory paths of the
trigeminal and vagus and probably also from the ner\'us intermedius and the glosso-
pharyngeal. Collaterals from the posterior longitudinal bundle and the ventral
longitudinal bundle are said to pass to the nucleus.
The Accessory Nerve (XI cranial) contains somatic motor fibers. The spinal part
arises from lateral cell groups in the anterior column near its dorso-lateral margin in
the upper five or six segments of the cord, its roots pass through the lateral funiculus
to the lateral surface of the cord. It supplies the Trapezius and Sternocleido-
mastoideus. The cranial part arises from the nucleus ambiguus, the continuation in
the medulla oblongata of the lateral cell groups of the anterior column of the spinal
cord from which the spinal part has origin. The upper part of the nucleus ambiguus
gives motor fibers to the vagus and glossopharjTigeal nerves. The cranial part
sends it fibers through the ^•agus to the lar^•ngeal nerves to supply the muscles of
the larynx. The root fibers of the cranial part of the accessory nerve pass anterior
to the spinal tract of the trigeminal while those of the vagus pass through or dorsal
to the trigeminal root, and emerge in the line of the postero-lateral sulcus. The
nucleus of origin of the spinal part undoubtedly receives either directly or indirectly
terminals and collaterals controlling ^'oluntary movements from the p^Tamidal
tracts. It is probable that terminals and collaterals reach the nucleus either directly
or indirectly from the rubrospinal and the vestibulospinal tracts. It is also con-
nected indirectly with the spinal somatic sensory nerves by association fibers of the
proper fasciculi. The cranial part receives indirectly or directly terminals and col-
laterals from the opposite pyramidal tract and form the terminal sensory nuclei of
the cranial nerves. A few fibers of the cranial part are said to arise in the dorsal
nucleus of the vagus and are thus sympathetic efterent. They are said to join the
vagus nerve.
The Vagus Nerve (A" cranial) contains somatic sensory, sjTnpathetic afferent,
somatic motor, sympathetic efferent and (taste fibers?) , The afterent fibers (somatic
sensory, sympathetic, and taste) have their cells of origin in the jugular ganglion
and in the nodosal ganglion (ganglion of the trunk) and on entering the medulla
divide into ascending and descending branches as do the sensory fibers of the pos-
terior roots of the spinal nerves after they enter the spinal cord.
(1) The somatic sensory fibers are few in number, convey impulses from a limited
area of the skin on the back of the ear and posterior part of the external auditory
meatus, and probably join the spinal tract of the trigeminal nerve to terminate in
its nucleus. Connections are probably established through the central path of
the trigeminal with the thalamus and somatic sensory area of the cortex for the
S56 NEUROLOGY
conscious recognition of impulses. The descending fibers in the spinal tract of the
trigeminal terminating in the nucleus of the tract probably establish relations
through connecting neurons with motor nuclei in the anterior column of the spinal
cord and with motor nuclei of the medulla.
(2) The sympathetic afferent fibers are usually described as terminating in the
dorsal nucleus of the vagus and glossopharyngeal. Some authors, however, believe
they join the tractus solitarius and terminate in its nucleus. These afferent fibers
convey impulses from the heart, the pancreas, and probably from the stomach,
esophagus and respiratory tract. Their terminals in the dorsal nucleus come into
relation with neurons whose axons probably descend into the spinal cord, conveying
impulses to the motor nuclei supplying fibers to the muscles of respiration, i. e.,
the phrenic nerve and the nerves to the intercostal and levatores costarum muscles.
Other axons probably convey vasomotor impulses to certain sympathetic efferent
neurons throughout the spinal cord. The dorsal nucleus (nucleus of the ala cinerea)
and the posterior continuation of it into the commissural nucleus of the ala cinerea
constitute probably the so-called respiratory and vaso-motor center of the medulla.
The shorter reflex neurons of the dorsal nucleus probably effect connections
either directly or indirectly with motor cells of the \'agus itself and other cranial
nerves.
(3) Taste fibers conducting impulses from the epiglottis and larynx are supposed
to pass in the vagus and to join the tractus solitarius, finally terminating in the
nucleus of the tractus solitarius. It is not certain that this nucleus represents the
primary terminal center for taste and some authors maintain that the taste fibers
terminate in the dorsal nucleus. The secondary ascending pathways from the
primary gustatory nucleus to the cortex as well as the location of the cortical
center for taste are unkno\Mi. A gustatory center has been described near the ante-
rior end of the temporal lobe. The nucleus of the tractus solitarius is connected
with motor centers of the pons, medulla and spinal cord for the reactions of mastica-
tion and swallowing.
(4) Somatic motor fibers lo the cross striated muscles of the pharynx and larynx
arise in the nucleus ambiguus. This nucleus undoubtedly receives either directly
or indirectly collaterals or terminals from the opposite pyramidal tract controlling
the voluntary movements of the pharynx and larynx. The reflex path\vays con-
veying impulses from the terminal sensory nuclei are unknown, but probably form
part of the intricate maze of fibers constituting the reticular formation.
(5) Sympathetic efferent fibers arise from cells in the dorsal nucleus (nucleus of
the ala cinerea). These are preganglionic hbers of the sympathetic system and all
terminate in sympathetic ganglia from which postganglionic fibers are distributed to
various organs, i. e., motor fibers to the esophagus, stomach, small intestine, gall-
bladder, and to the lungs; inhibitory fibers to the heart; secretory fibers to the
stomach and pancreas. The dorsal nucleus not only receives terminals of sym-
pathetic afferent fibers for reflexes but undoubtedly receives terminals and collaterals
from man>' other sources, but the exact pathways are at present unkno^^^l.
The Glossopharyngeal Nerve {IX cranial) is similar to the vagus nerve as regards
its central connections and is usually described with it. It contains somatic sensory,
sympathetic afferent, taste, somatic motor and sym])athetic efferent fibers. The
afferent sensory fibers arise from cells in the superior ganglion and in the petrosal
ganglion. The same uncertainty exists concerning the nuclei of termination and
nuclei of origin of the various components as for the vagus.
(1) The somatic sensory fibers are few in number. Some are distributed with
the auricular branch of the vagus to the external ear; others probably pass to the
pharynx and fauces. They are supposed to join the spinal tract of the trigeminal
and terminate in its nucleus. The connections are similar to those of the somatic
sensory fibers of the \'agus.
COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 857
(2) Sympathetic afferent fibers from the pharynx and middle ear are supposed to
terminate in the dorsal nucleus. Connections are probably established with motor
nuclei concerned in chewing and swallowing; very little is known, however, about
the connections with other parts of the l)rain.
(3) Taste fibers from the tongue probably terminate in the nucleus of the tractus
solitarius. These fibers together with similar fibers from the facial (nervus inter-
medins) and the vagus are supposed to form the tractus solitarius and terminate
in its nucleus. The central connections have been considered under the vagus.
(4) Somatic motor fibers to the St>lopharyngcus muscle arise in the upper end
of the nucleus ambiguus. The existence of these fibers in the roots of the glosso-
pharyngeal is uncertain, as there are other paths by which such fibers might reach
the glossopharyngeal from the vagus. The sources of impidses passing to the
nucleus ambiguus are considered under the vagus.
(5) Sympathetic efferent fibers {motor and secretory fibers) arise from the nucleus
dorsalis. Some authors believe that the secretory fibers to the parotid gland arise
from a distinct nucleus, the inferior salivatory nucleus, situated near the dorsal
nucleus. The preganglionic fibers from this nucleus terminate in the otic ganglion;
the postganglionic fibers from the otic ganglion pass to the parotid gland.
The Acoustic Nerve {VIII crnnial) consists of two distinct nerves the cochlear
nerve, the nerve of hearing, and the vestibular nerve, the nerve of equilibration.
6 14
14 6
i '2
Fig.
12 liJ
760. — Terminal nuclei of the cochlear nerve, with their upper connections. (Schematic.) The vestibular
nerve with its terminal nuclei and their efferent fibers have been suppressed. On the other hand, in order not to
obscure the trapezoid body, the efferent fibers of the terminal nuclei on the right side have been resected in a consid-
erable portion of their extent. The trapezoid body, therefore, shows only one-half of its fibers, viz., those which
come from the left. 1. Vestibular nerve, divided at its entrance into the medulla oblongata. 2. Cochlear nerve. 3. ■
Accessory nucleus of acoustic nerve. 4. Tuberculum acusticum. 5. Efferent fibers of accessory nucleus. 6. Efferent
fibers of tuberculum acusticum, forming the striae meduUares, with 6', their direct bundle going to the superior
olivary nucleus of the same side; 6", their decussating bundles going to the superior olivary nucleus of the opposite
side. 7. Superior olivary nucleus. 8. Trapezoid body. 9. Trapezoid nucleus. 10. Central acoustic tract (lateral
lemniscus). 11. Raph6. 12. Cerebrospinal fasciculus. 13. Fourth ventricle. 14. Inferior peduncle. (Testut.)
The Cochlear Nerve arises from bipolar cells in the spiral ganglion of the cochlea;
the peripheral fibers end in the organ of Corti, the central fibers bifurcate as they
enter the cochlear nucleus ; the short ascending branches end in the ventral portion
of the nucleus, the longer descending branches terminate in the dorsal portion of
the nucleus. From the dorsal portion of the cochlear nucleus axons arise which
pass across the dorsal aspect of the inferior peduncle and the floor of the fourth
ventricle, the striae meduUares, to the median sulcus. Here they dip into the sub-
stance of the pons, cross the median plane, and join the lateral lemniscus. Some
858 NEUROLOGY
of the fibers terminate in the superior olivary nucleus. The fibers of the striae
medullares are not always visible on the floor of the rhomboid fossa. From the
ventral portion of the cochlear nucleus axons pass into the trapezoid body, here
some of them end in the superior olivary nucleus of the same side, others cross the
midline and end in the superior olivary nucleus of the opposite side or pass by these
nuclei, giving off collaterals to them, and join the lateral lemniscus. Other fibers
either terminate in or give oft' collaterals to the nucleus of the trapezoid body of
the same or the opposite side. Other fibers from the ventral portion of the cochlear
nucleus pass dorsal to the inferior peduncle and then dip into the substance of the
pons to join the trapezoid body or the superior olivary nucleus of the same side.
From the superior olivary nucleus of the same and opposite sides axons join the
lateral lemniscus. 'Collaterals and probably terminals also pass from the lateral
lemniscus to other nuclei in its path and receive in turn axons from these nuclei.
They are the accessory nucleus, the medial preolivary nucleus, the lateral pre-
olivary or semilunar nucleus and the nucleus of the lateral lemniscus.
The trapezoid body consists of horizontal fibers in the ventral part of the formatio
reticularis of the lower part of the pons behind its deep transverse fibers and the
pyramid bundles. The axons come from the dorsal and ventral portions of the
cochlear nucleus. After crossing the raphe, where they decussate with those from
the opposite side, they turn upward to form the lateral lemniscus. Fibers from the
strife medullares contribute to the trapezoid body, in addition it sends terminals
or collaterals to and receives axons from the superior olivary nucleus, the nucleus
of the trapezoid body, the lateral preolivary or semilunar nucleus and the mesial
preolivary nucleus.
The cochlear nucleus, the terminal nucleus for the nerve of hearing, is usually
described as consisting of a larger dorsal nucleus on the dorsal and lateral aspect of
the inferior peduncle forming a prominent projection, the acoustic tubercle, and a
ventral or accessory cochlear nucleus more ventral to the inferior peduncle. The
two nuclei are continuous and are merely portions of one large nucleus. The axons
from cells of the spiral ganglion of the cochlear nerve on reaching the nucleus
divide into ascending and descending branches which enter the \-entral and dorsal
nuclei respectively. Axons from the large fusiform cells of the dorsal nucleus pass
partly by way of the striae medullares to the trapezoid body and lateral lemniscus
and the nuclei associated with the former, and partly transversely beneath the
inferior peduncle and spinal tract of the trigeminal to the trapezoid body. Axons
from the ventral cochlear nucleus pass partly by the striae medullares but for the
most part horizontally to the trapezoid body.
The superior olivary nucleus is a small mass of gray matter situated on the dorsal
surface of the lateral part of the trapezoid body. Some of its axons pass backward
to the abducent nucleus, this bundle is kno^\m as the peduncle of the superior
olivary nucleus. Other fibers from the nucfeus join the posterior longitudinal
bimdle and terminate in the nuclei of the trochlear and oculomotor nerves. The
majority of its axons, after giving oft" collaterals to the nucleus itself join the lateral
lemniscus of the same side, other axons pass in the trapezoid body toward the ven-
tral portion of the cochlear nucleus.
The nucleus of the trapezoid body lies between the root fibers of the abducent nerve
and the superior "olivary nucleus. Its cells lie among the fibers of the trapezoid
body. In it termhiate fibers and collaterals of the trapezoid body w^hich come
from the cochlear nucleus of the opposite and probably the same side and from the
opposite trapezoid nucleus. They terminate in the nucleus of the trapezoid body
in diftuse arborizations and peculiar end plaques or acoustic calyces of yellowish
color which fuse with the cell bodies. Its cells are round and of medium size; their
axons pass into the trapezoid body, cross the median line and probably join the
lateral fillet.
COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 859
The lateral preolivary or semilunar nucleus lies ventral to the superior olivary
riucleus. In it end ternunals and collaterals of the trapezoid body and probably
fibers of the opposite cochlear nucleus. Its axons mingle with the trapezoid body
and join the lateral fillet.
The mesial preolivary nucleus is in contact with the ventral side of the nucleus
of the trapezoid body. It receives many collaterals from the trapezoid body. Its
cells are smaller than those of the trapezoid nucleus, their axons ioin the lateral
fillet.
The lateral lemniscus {lateral fillet) , the continuation upward of the central path
of hearing, consists of fibers which come from the cochlear nuclei of the same and
the opposite side by way of the trapezoid body and from the preolivary nuclei. It
lies in the ventral or ventro-lateral part of the reticular formation of the pons, at
first ventral then lateral to the median fillet. Above the pons these ascending fibers
come to the surface at the side of the reticular formation in the trigonum lemnisci
and are covered by a layer of ependyma. This part of the lateral lenmiscus is
known as the fillet of Reil. On reaching the level of the inferior colliculus the dorsal
fibers which overlie the superior peduncle decussate in the velum meduUare anterius
with similar fibers of the opposite side. Numerous small masses of cells are scattered
along the jjath of the lateral lemniscus above the superior olivary nucleus and con-
stitute lower and upper nuclei of the lateral lemniscus. They are supplied with
many collaterals and possibly terminals from the fibers of the lemniscus. The axons
of the lower nucleus of the lateral lemniscus, which arise from the larger stellate or
spindle-shaped cells, with long, smooth, much branched dendrites, are said by some
authors to join the lateral lemniscus, but according to Cajal they pass medially
toward the raphe; their termination is unkno\vn. The cells of the upper nucleus
of the lateral lemniscus are more scattered. The same uncertainty exists in regard
to their termination.
The fibers of the lateral lemniscus end by terminals or collaterals in the inferior
colliculus and the medial geniculate body. A few of the fibers are said to pass by
the inferior colliculus to terminate in the middle portion of the stratum griseum of
the superior colliculus, and are probably concerned with reflex movements of the
eyes depending on acoustic stimuli.
The inferior colliculi (lourr or posterior qvadrigcminal bodies) are important
auditory reflex centers. Each consists of a compact nucleus of gray matter covered
by a superficial white layer and separated from the central gi*ay matter about
the aqueduct by a thin, deep, white layer. Many of the axons which appear in the
superficial white layer ascend through the inferior brachium to the medial genicu-
late body. Others mainly from large cells in the dorso-mesial part of the nucleus
pass through the deep white layer into the tegmentum of the same and the opposite
side and descend. Their termination is unknown, but they probably constitute an
auditory reflex path to the lower motor centers, perhaps descending into the spinal
cord with the tectospinal fasciculus. Other axons are said to descend in the lateral
lemniscus to the various nuclei in the auditory path (Held) and probably to motor
nuclei of the medulla and spinal cord.
The medial geniculate body receives terminals and collaterals from the lateral
lemniscus (the central auditory path) and also large numbers of axons from the
inferior colliculus of the same side and a few from the opposite side. It is thus a
station in the central auditory path. A large proportion of its axons pass forward
beneath the optic tract to join the corona radiata and then sweep backward and
lateralward as the auditory radiation to terminate in the cortex of the superior
temporal gyrus. V. Monakow holds that Golgi cells type II are interpolated between
the terminations of the incoming fibers to the medial geniculate body and the cells
located there which give rise to the fibers of the auditory radiation. The medial
geniculate bodies are united by the long, slender commissure of Gudden. These
860
NEUROLOGY
J i:
fibers join the optic tract as it passes over the edge of the medial geniculate and
passes through the posterior part of the optic chiasma. It is probably a commissure
connected with the auditory system.
The Vestibular Nerve (vestibvlar root, Till crania}) arise from the bipolar cells
in the vestibular ganglion (Scarpa's ganglion). The peripheral fibers end in the
semicircular canals, the saccule and the utricle, the end-organs concerned with
mechanism for the maintenance of bodily equilibrium. The central fibers enter
the medulla oblongata and pass between the inferior peduncle and the spinal tract
of the trigeminal. They bifurcate into ascending and descending branches as do
the dorsal root fibers of all the spinal nerves and all afterent cranial nerves. The
descending branches terminate in the dorsal (medial) vestibular nucleus, the
principal nucleus of the vestibular nerve. This nucleus is prolonged do\\iiward
into a descending portion in which end terminals and collaterals of the descending
branch. The ascending branches pass to Deiters's nucleus, to Bechterew's nucleus
and through the inferior peduncle
6 of the cerebellum to the nucleus
^ -• tecti of the opposite side.
The dorsal vestibular nucleus
{medial or principal nucleus) is a
large mass of small cells in the
floor of the fourth ventricle under
the area acustica, located partly
in the medulla and partly in the
pons. The striae medullares cross
the upper part of it. It is sepa-
rated from the median plane by
the nucleus intercalatus. Its axons
pass into the posterior longitudi-
nal bundle of the same and the
opposite side and ascend to ter-
minate in the nucleus abducens
of the same side and in the troch-
lear nucleus and the oculo-motor
nucleus of the opposite side, and
to the motor nuclei of the trigem-
inal on both sides. The descending
portion, the nucleus of the descend-
ing tract extends do\\Tiward as far as the upper end of the nucleus gracilis, and the
decussation of the medial lemniscus. It is sometimes called the inferior vestibular
nucleus. INIany of its axons cross the midline and probably ascend with the medial
lemniscus to the ventro-lateral region of the thalamus.
The lateral vestibular nucleus {Deiters's nnclevs) is the continuation upward and
laterahvard of the principal nucleus, and in it terminate many of the ascending
branches of the vestibular nerve. It consists of very large multipolar cells whose
axons form an important ])art of the posterior longitudinal bundle of the same and
the opposite sid?. The axons bifurcate as they enter the posterior longitudinal
bundle, the ascending branches send terminals and collaterals to the motor nuclei
of the abducens, trochlear and oculomotor nerves, and are concerned in coordinating
the movements of the eyes with alterations in the position of the head ; the descending
branches pass do^ni in the posterior longitudinal bundle into the anterior funiculus
of the spinal cord as the vestibulospinal fasciculus (anterior marginal bundle) and
are distributed to motor nuclei of the anterior column by terminals and collaterals.
Other fibers are said to pass directly to the ^•estibulospinal fasciculus without
passing into the posterior longitudinal bundle. The fibers which pass into the
Fig. 761. — Terminal nuclei of the vestibular nerve, with their
upper connections. (Schematic.) 1. Cochlear ncrvp, with its
two nuclei. 2. Accessory nucleus. 3. Tuberculum acusticum.
4. Vestibular nerve. 5. Internal nucleus. 6. Nucleus of Deiters.
7. Nucleus of Bechterew. 8. Inferior or descending root of
acoustic. 9. Ascending cerebellar fibers. 10. Fibers going to
raphfi. 11. Fibers taking an oblique course. 12. Lemniscus. 13.
Inferior sensory root of trigeminal. 14. Cerebrospinal fasciculus.
15. Raph6. 16. Fourth ventricle. 17. Inferior peduncle. Origin
of striEe medullares. (Testut.)
COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 861
vestibulospinal fasciculus are intimately concerned with equilibratory reflexes.
Other axons from Deiters's nucleus are supposed to cross and ascend in tlie opposite
medial lemniscus to the ventro-lateral nuclei of the thahimus; still other fibers pass
into the cerebellum with the inferior peduncle and are distributed to the cortex of
the vermis and the roof nuclei of the cerebellum; according to Cajal they merely
pass through the nucleus fastigii on their way to the cortex of the vermis and the
hemisphere.
The superior vestibular nucleus {Bechtereio's nvcJens) is the dorso-lateral part of
the vestibular nucleus and receives collaterals and terminals from the ascending
branches of the vestibular nerve. Its axons terminate in much the same manner
as do those from the lateral nucleus.
The Facial Nerve (]'// cranial) consists of somatic sensory, sympathetic afferent,
taste, somatic motor and s\Tnpathetic efferent fibers. The afferent or sensory
fibers arise from cells in the geniculate ganglion. This portion of the nerve is often
described as the nervus intermedins.
(1) The somatic sensory fibers are few in number and convey sensory impulses
from the middle ear region. Their existence has not been fulh' confirmed. Their
central termination is likewise uncertain, it is possible that they join the spinal
tract of the trigeminal as do the somatic sensory fibers of the vagus and glosso-
pharyngeal.
(2) The sympathetic afferent fibers are likewise few in number and of unknown
termination.
(3) Taste fibers convey impulses from the anterior two-thirds of the tongue via
the chorda tympani. They are supposed to join the tractus solitarius and termi-
nate in its nucleus. The central connections of this nucleus have already' been
considered.
(4) Somatic motor fibers, supplying the muscles derived from the hyoid arch,
arise from the large multipolar cells of the nucleus of the facial nerve. This nucleus
is serially homologous with the nucleus ambiguus and lateral part of the anterior
column of the spinal cord. Voluntary impulses from the cerebral cortex are con-
veyed by terminals and collaterals of the p\Tamidal tract of the opposite side,
indirectly, that is with the interpolation of a connecting neuron, to the facial
nucleus. This nucleus undoubtedly receives many reflex fibers from various
sources, i. e., from the superior colliculus via the ventral longitudinal bundle
{iectospinal jasdcuhis) for optic reflexes; from the inferior colliculus via the auditory
reflex path; and indirectly from the terminal sensory nuclei of the brain-stem.
Through the posterior longitudinal bundle it is intimateh' connected with other
motor nuclei of the brain-stem.
(5) Sympathetic efferent fibers {preganglionic fibers) arise according to some
authors from the small cells of the facial nucleus, or according to others from a
special nucleus of cells scattered in the reticular formation, dorso-medial to the
facial nucleus. This is sometimes called the superior salivatory nucleus. These
preganglionic fibers are distributed partly via the chorda tympani and lingual nerves
to the submaxillary ganglion, thence by postganglionic (vasodilator) fibers to the
submaxillary and sublingual glands. Some of the preganglionic fibers pass to the
sphenopalatine ganglion via the great superficial petrosal nerve.
The Abducens Nerve (F/ cranial) contains somatic motor fibers only which
supply the lateral rectus muscle of the eye. The fibers arise from the nucleus of
the abducens nerve and pass ventrally through the formatio reticularis of the pons
to emerge in the transverse groove between the caudal edge of the pons and the
p>Tamid. The nucleus is serially homologous with the nuclei of the trochlear and
oculomotor above and with the hypoglossal and medial part of the anterior column
of the spinal cord below. It is situated close to the floor of the fourth ventricle,
just above the level of the stria meduUares. Voluntary impulses from the cerebral
862 NEUROLOGY
cortex are conducted by the p>Tamidal tract fibers (corticopontine fibers). These
fibers probably terminate in relation with association neurons which control the
coordinated action of all the eye muscles. This association and coordination
mechanism is interposed between the terminals and collaterals of the voluntary
fibers and the neurons within the nuclei of origin of the motor fibers to the eye
muscles. The fibers of the posterior longitudinal bundle are supposed to play an
unportant role in the coordination of the movements of the eyeball. ^Yhether it is
concerned only with co5rdinations between the vestibular apparatus and the eye
or with more extensive coordinations is unkno^\^l. Many fibers of the posterior
longitudinal bundle have their origin in the terminal nuclei of the vestibular nerve
and from the posterior longitudinal bundle many collaterals and terminals are
given off to the abducent nucleus as well as to the trochlear and oculomotor nuclei.
The abducens nucleus probably receives collaterals and terminals from the ventral
longitudinal bundle (tectospinal fasciculus) ; fibers which have their origin in the
superior colliculus, the primary visual center, and are concerned with visual reflexes.
Others probably come from the reflex auditory center in the inferior colliculus and
from other sensory nuclei of the brain-stem.
The Trigeminal Nerve (T cranial) contains somatic motor and somatic sensory
fibers. The motor fibers arise in the motor nucleus of the trigeminal and pass
ventro-laterally through the pons to supply the muscles of mastication. The sensory
fibers arise from the unipolar cells of the semilunar ganglion ; the peripheral branches
of the T-shaped fibers are distributed to the face and anterior two-thirds of the
head; the central fibers pass into the pons with the motor root and bifurcate into
ascending and descending branches which terminate in the sensory nuclei of the
trigeminal.
The motor nucleus of the trigeminal is situated in the upper part of the pons
beneath the lateral angle of the fourth ventricle. It is serially homologous with
the facial nucleus and the nucleus ambiguus (motor nucleus of the vagus and glosso-
pharyngeal) which belong to the motor nuclei of the lateral somatic group. The
axons arise from large pigmented multipolar cells. The motor nucleus receives
reflex collaterals and terminals, (1) from the terminal nucleus of the trigeminal of
the same and a few from the opposite side, via the central sensory tract (trigemino-
thalamic tract); (2) from the mesencephalic root of the trigeminal; (3) from the
posterior longitudinal bundle ; (4) and probably from fibers in the f ormatio reticu-
laris. It also receives collaterals and terminals from the opposite pyramidal tract
(corticopontine fibers) for voluntary movements. There is probably a connecting
or association neuron interposed between these fibers and the motor neurons.
The terminal sensory nucleus consists of an enlarged upper end, the main sensory
nucleus, and a long more slender descending portion which passes do^^^l through
the pons and medulla to become continuous with the dorsal part of the posterior
column of the gray matter especially the substantia gelatinosa of the spinal cord.
This descending portion consists mainly of substantia gelatinosa and is called the
nucleus of the spinal tract of the trigeminal nerve.
The main sensory nucleus lies lateral to the motor nucleus beneath the superior
peduncle. It receives the short ascending branches of the sensory root. The
descending branches which form the tractus spinalis, pass dowm through the pons
and medulla on the lateral side of the nucleus of the tractus spinalis, in which they
end by collaterals and terminals, into the spinal cord on the level of the second
cervical segment. It decreases rapidly in size as it descends. At first it is located
between the emergent part of the facial nerve and the vestibular nerve, then between
the nucleus of the facial nerve and the inferior peduncle. Lower dowai in the upper
part of the medulla it lies beneath the inferior peduncle and is broken up into
bundles by the oli\ocerebellar fibers and the roots of the ninth and tenth cranial
nerves. Finalh- it comes to the surface of the medulla under the tubercle of
COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 863
Rolando and continues in this position lateral to the fasciculus cuneatus as far as
the upper jiart of the cervical region where it disappears.
The cells of the sensory nucleus are of large and medium size and send their
axons into the formatio reticularis where they form a distinct bundle, the central
path of the trigeminal {trigerninothalamic tract), which passes upward tlirough the
formatio reticularis and tegmentum to the ventro-lateral part of the thalamus.
]\Iost of the fibers cross to the trigeminothalamic tract of the opposite side. This
tract lies dorsal to the medial fillet; approaches close to it in the tegmentum and
terminates in a distinct part of the thalamus. From the thalamus impulses are
conveyed to the somatic sensory area of the cortex by axons of cells in the thalamus
through the internal capsule and corona radiata. Many collaterals are given off
in the medulla and pass from the trigeminothalamic tract to the motor nuclei,
especially to the nucleus ambiguus, the facial nucleus and the motor nucleus of the
trigeminal.
The somatic sensory fibers of the \'agus, the glossopharyngeal and the facial
nerves probabh' end in the nucleus of the descending tract of the trigeminal and
their cortical impulses are probably carried up hi the central sensory path of the
trigeminal;
The mesencephalic root {descending root of the trigeminal) arises from unipolar
cells arranged in scattered groups in a column at the lateral edge of the central
gray matter surrounding the upper end of the fourth ventricle and the cerebral
aqueduct. They have usually been considered as motor fibers that join the motor
root, but Johnston claims that they join the sensory root of the trigeminal, that they
develop in the alar, not in the basal lamina, and that the pear-shaped miipolar
cells are sensory in type.
The Trochlear Nerve (71' cranial) contains somatic motor fibers only. It supplies
the superior oblique muscle of the eye. Its nucleus of origin, trochlear nucleus,
is a small, oval mass situated in the ventral part of the central gray matter o^ the
cerebral aqueduct at the level of the upper part of the inferior colliculus. The
axons from the nucleus pass dowmward in the tegmentum toward the pons, but
turn abruptly dorsalward before reaching it, and pass into the superior medullary
velum, in which they cross horiz^ontally, to decussate with the nerve of the opposite
side, and emerges from the surface of the velum, immediately behind the inferior
colliculus. The cells of the trochlear nucleus are large, irregular and yellowish in
color. The nuclei of the two sides are separated by the raphe through which
dendrites extend from one nucleus to the other. They receive many collaterals
and terminals from the posterior longitudinal bundle which lies on the ventral
side of the nucleus.
There are no branches from the fibers of the p\Tamidal tracts to these nuclei;
the volitional pathway must be an indirect one, as is the case with other motor
nuclei.
The Oculomotor Nerve (/// cranial) contains somatic motor fibers to the Obliquus
inferior, Rectus inferior. Rectus superior. Levator palpebrse superioris and Rectus
medialis muscles and sympathetic efferent fibers (preganglionic fibers) to the
ciliary ganglion. The postganglionic fibers connected with these supply the ciliary
muscle and the sphincter of the iris. The axons arise from the nucleus of the
oculomotor nerve and pass in bundles through the posterior longitudinal bundle,
the tegmentum, the red nucleus and the medial margin of the substantia nigra in a
series of curves and finally emerge from the oculomotor sulcus on the medial side
of the cerebral peduncle.
The oculomotor nucleus lies in the gray substance of the floor of the cerebral
aqueduct subjacent to the superior colliculus and extends in front of the aqueduct
a short distance into the floor of the third ventricle. The inferior end is continuous
with the trochlear nucleus. It is from 6 to 10 mm. in length. It is intimately
864
NEUROLOGY
d
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r\V
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related to the posterior longitudinal bundle which lies against its ventro-lateral
aspect and many of its cells lie among the fibers of the posterior longitudinal bundle.
The nucleus of the oculomotor nerve contains several distinct groups of cells which
diflfer in size and appearance from each other and are supposed to send their axons
each to a separate muscle. IVIuch uncertainty still exists as to which group supplies
which muscle. There are seven of these groups or nuclei on either side of the mid-
line and one medial nucleus. The cells of the anterior nuclei are smaller and are
supposed to give oft" the sympathetic efferent axons. The majority of fibers arise
from the nucleus of the same side some, however, cross from the opposite side and
are supposed to supply the Rectus medialis muscle. Since oculomotor and abducens
nuclei are intimately connected by the posterior longitudinal bundle this decussa-
tion of fibers to the Medial rectus may facili-
tate the conjugate mo\'ements of the eyes in
which the IMedial and Lateral recti are espe-
cially involved.
IVIany collaterals and terminals are given off
to the oculomotor nucleus from the posterior
longitudinal bundle and thus connect it with
the vestibular nucleus, the trochlear and ab-
ducens nuclei and probably with other cranial
nuclei. Fibers from the visual reflex center in
the superior colliculus pass to the nucleus. It
is also connected with the cortex of the occip-
ital lobe of the cerebrum by fibers which
pass through the optic radiation. The path-
way for voluntary motor impulses is probably
similar to that for the abducent nerve.
The Optic Nerve or Nerve of Sight (77 cranial)
consists chiefly of coarse fibers which arise
from the ganglionic layer of the retina. They
constitute the third neuron in the series com-
posing the visual path and are supposed to
convey only ^'isual impressions. A niunber of
fine fibers also pass in the optic nerve from
the retina to the primary centers and are sup-
posed to be concerned in the pupillary re-
flexes. There are in addition a few fibers which
pass from the brain to the retina ; they are sup-
posed to control chemical changes in the retina
and the movements of the pigment cells and cones. Each optic nerve has, accord-
ing to Salzer, about 500,000 fibers.
In the optic chiasma the nerves from the medial half of each retina cross to enter
the opposite optic tract, while the nerves from the lateral half of each retina pass
into the optic tract of the same side. The crossed fibers tend to occupy the medial
side of each optic nerve, but in the chiasma and in the optic tract they are more
intermingled. The optic tract is attached to the tuber cinereum and lamina
terminalis and also to the cerebral peduncle as it crosses obliquely over its under
surface. These are not functional connections. A small band of fibers from the
medial geniculate body joins the optic tract as the latter passes over it and crosses
to the opposite tract and medial geniculate body in the posterior part of the chiasma.
This is the commissure of Gudden and is probably connected with the auditory
system.
Most of the fibers of the optic tract terminate in the lateral geniculate body,
some pass through the superior brachium to the superior colliculus, and others
S:..:5":
Fig. 762. — Figure showing the different groups
of cells, which constitute, according to Perlia,
the nucleus of origin of the oculomotor nerve.
1. Posterior dorsal nucleus. 1'. Posterior ven-
tral nucleus. 2. Anterior dorsal nucleus. 2'. Ante-
rior ventral nucleus. 3. Central nucleus. 4.
Nucleus of Edinger and Westphal. 5. Antero-
internal nucleus. 6. Antero-external nucleus. 8.
Crossed fibers. 9. Trochlear nerve, with 9', its
nucleus of origin, and 9", its decussation. 10.
Third ventricle. M, M. Median line. (Testut.)
COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 8(55
either pass over or through the lateral geniculate bo(l>' to the ijulvinar of the
thalamus. These end-stations are often called the primary visual centers.
The lateral geniculate body consists of medium-sized pigme"nted nerve cells
arranged in several layers by the penetrating fibers of the optic tract. Their axons
pass upward beneath the longer fibers of the optic tract, the taniia semicircularis,
the caudate nucleus and the posterior horn of the lateral ventricle where they join
the optic radiation of Gratiolet. They pass backward and medially to terminate
in the visuo-sensory cortex in the immediate neighborhood of the ciilcarine fissure
- Optic nerve
Croased fibers
Uncrossed fibers
Optic chiasma
Optic tract
Commissure of Gudden
Pulvinar
Lateral geniculate body
Superior collicul-us
Medial geniculate body
Nucleus of oculomotor nerve
Nucleus of trochlear nerve
Nucleus of abducent nerve
Cortex of occipital lobes
Fig. 763. — Scheme showing central connections of the optic nerves and optic tracts.
of the occipital lobe. This center is connected with the one in the opposite side by
commissural fibers which course in the optic radiation and the splenium of the corpus
callosum. Association fibers connect it with other regions of the cortex of the same
side.
The region of the pulvinar in which optic tract fibers terminate resembles in
structure the lateral geniculate body. Its axons also have a similar course though
in a somewhat more dorsal plane.
The superior colliculus receives fibers from the optic tract through the superior
brachium. Some enter by the superficial white layer (stratum zonale), others
appear to dip down into the gray cap (stratum cinereum) while others probably
■55
866 NEUROLOGY
decussate across the midline to the opposite colliciilus. Other fibers from the
superior brachium pass into the stratum opticum (upper gray-white layer). Some
of these turn upward into the gray cap while others terminate among the cells
of this layer. Since the superior colliculi appear to be the central organs con-'
cerned in the control of eye-muscle movements and eye-muscle reflexes we should
expect to find them receiving fibers from other sensory paths. Many fibers pass to
the superior coUiculus from the medial fillet as the latter jjasses through the teg-
mentum bringing the superior colliculus into relation with the sensory fibers of the
spinal cord. Fibers from the central sensory path of the trigeminal probably pass
with these. Part of the ventral spinocerebellar tract (Gowers) is said to pass up
through the reticular formation of the pons and mid-brain toward the superior
colliculus and the thalamus. The superior colliculus is intimately connected with
the central auditor>' path (the lateral lemniscus), as part of its fibers pass the
inferior colliculus and terminate in the superior colliculus. They are probably
concerned with reflex movements of the eyes depending on auditory stimuli. The
superior colliculus is said to receive fibers from the stria medullaris thalamis of
the opposite side which pass through the commissura habenulse and turn back
to the roof of the mid-brain, especially to the superior colliculus. By this path
both the primary and cortical olfactory centers are brought into relation with the
eye-muscle reflex apparatus.
The fibers which pass to the nuclei of the eye muscles arise from large cells in
the stratum opticum and stratum lemnisci and pass around the ventral aspect
of the central gray matter where most of them cross the midline in the fountain
decussation of ^Nleynert, and then turn do^Miward to form the ventral longitudinal
bundle. This bundle runs dowTi partly through the red nucleus, in the formatio
reticularis, ventral to the posterior longitudinal bundle of the mid-brain, pons and
medulla oblongata into the ventral funiculus of the spinal cord where it is known
as the tectospinal fasciculus. Some of the fibers are said to pass doAm with the
rubrospinal tract in the lateral funiculus. Some fibers do not decussate but pass
down in the ventral longitudinal bundle of the same side on which they arise unless
possibly they come from the opposite colliculus over the aqueduct. From the
ventral longitudinal bundle collaterals are gi\-en off to the nuclei of the eye muscles,
the oculomotor, the trochlear and the abducens. Many collaterals pass to the red
nucleus, and are probably concerned with the reflexes of the rubrospinal tract.
The fibers of the tectospinal tract end by collaterals and terminals either directly
or indirectly among the motor cells in the anterior column of the spinal cord.
The superior colliculus recei\es fibers from the visual sensory area of the occipital
cortex; they pass in the optic radiation. ProbabK' no fibers pass from the superior
colliculus to the \'isual sensory cortex.
The Olfactory Nerves (7 cranial) or nerves of smell arise from spindle-shaped
bipolar cells in the surface epithelium of the olfactory region of the nasal cavity.
The non-medullated axons jwss ujnvard in groups through luunerous foramina in
the cribriform jilate to the olfactory bulb; here several fibers, each ending in a tuft
of terminal filaments, come into relation with the brush-like end of a single den-
drite from a mitral cell. This interlacing gives rise to the olfactory glomeruli of the
bulb. The termination of several or many olfactory fibers in a shigle glomerulus
where they form synai)ses with the dendrites of one or two mitral cells provides for
the summation of stimuli in the mitral cells and accounts in part at least for the
detection by the olfactory organs of very dilute solutions. Lateral arborizations
of the dendrites of the mitral cells and the connection of neighboring glomeruli by
the axons of small cells of the glomeruli and the return of impulses of the mitral
cells by collaterals either directly or through the interpolation of granule cells to the
dendrites of the mitral cells reinforce the discharge of the mitral cells along their
axons. The axons turn abruptly backward in the deep fiber layer of the bulb to
COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 867
form the olfactory tract. The olfactory tract is continued into the olfactory
trigone, just in front of the anterior perforated substance. The axons of the mitral
cells on reaching the olfactory- trigone separate into three bundles, the lateral
olfactory stria, the medial olfactory stria and the less marked intermedial olfactory
stria.
The lateral olfactory striae curve lateralward, a few of the fibers end in the
olfactory trigone and the antero-lateral portion of the anterior perforated substance.
INIost of the fibers, howe\-er, pass into the uncus, the anterior end of the hippo-
campal g>Tus, and there end in the complicated cortex of the hippocampal gyri.
The lateral stride more or less disappear as they cross the antero-lateral region of
the anterior perforated substance.
The gi-eater mass of the fibers of the olfactory tract pass into the lateral stria.
Numerous collaterals are given into the plexiform layer of the subfrontal cortex,
over which the striae pass on their way to the uncus, where they intermingle with
the apical dendrons of the medium-sized and small p^tamidal cells of the pyramidal
layer of this subfrontal or frontal olfactory cortex. The axons give rise to projection
fibers which take an antero-posterior direction to the subthalamic region sending
collaterals and terminal branches to the stria medullaris and others toward the
thalamus. Some of the fibers extend farther back and are belie^'ed to reach the
pons and medulla oblongata.
Most of the fibers of the lateral olfactory stria pass to the hippocampal region
of the cortex, especially to the gyrus hippocampi, which ma>' be regarded as the
main ending place of the secondary olfactory path deri\'ed from axons of the mitral
cells.
The fibers of the medial olfactory striae terminate for the most part in the par-
olfactory area {Brocas area), a few end in the subcallosal gyrus and a few in the
anterior perforated substance and the adjoining part of the septum pellucidum.
Some of the fibers pass into the anterior commissure (pars olfactoria) to the olfac-
tory tract of the opposite side where they end partly within the granular layer
and partly in the neighborhood of the glomeruli of the olfactory bulb, thus con-
necting the bulbs of the two sides.
The intermediate olfactory striae are as a rule scarcely visible, the fibers terminate
in the anterior perforated substance, a few are said to continue to the uncus.
The trigonum olfactorium, anterior perforated substance and the adjoining
part of the septum pellucidum are important primary olfactory centers, especially
for olfactory refiexes; in these centers terminate many axons from the mitral cells
of the olfactory bulb. In addition the gray substance of the olfactory tract and the
g}TUs subcallosus receive terminals of the mitral cells.
The pathways from these centers to lower centers in the brain-stem and spinal
cord are only partially knowai. The most direct path, the tractus olfactomesen-
cephalicus (basal olfactory bundle of Wallenburg), is supposed to arise from cells in
the gray substance of the olfactory tract, the olfactory trigone, the anterior per-
forated substance and the adjoining part of the septum pellucidum. The fibers
are said to pass direct to the tuber cinereum, to the corpus mammillare, to the brain-
stem and the spinal cord. The fibers which enter the mammillary body probably
come into relation with cells whose axons give rise to the fasciculus mammillo-
tegmentalis {mammiUo-tecjinental bundle of Giidden) which is supposed to end in
the gray substance of the tegmentum and of the aqueduct; some of its fibers are
said to join the posterior longitudinal bundle and others to extend as far as the
reticular formation of the pons.
Some of the fibers of the medial olfactory stria came into relation with cells
in the parolfactory area of Broca and in the anterior perforated substance, whose
axons course in the medullary stria of the thalamus. As the axons pass through
the lower part of the septum pellucidum they are joined by other fibers whose cells
868 NEUROLOGY
receive impulses from the mitral cells. Thes 3 fibers of the medullary stria end for
the most part in the habenular nucleus of the same side, some, however, cross in the
habenular commissure (dorsal part of the posterior commissure) to the habenular
nucleus of the opposite side. A few fibers of the medullary stria are said to pass
by the habenular nucleus to the roof of the mid-brain, especially the superior col-
liculus, while a few others come into relation with the posterior longitudinal bundle
and association tracts of the mesencephalon.
The ganglion of the habenulse located in the trigonum habenulje just in front of
the superior colliculus contains a mesial nucleus with small cells and a lateral
nucleus with larger cells. The axons of these cells are grouped together in a bundle,
the fasciculus retroflexus of Meynert, which passes ventrally medial to the red
nucleus and terminates in a small medial ganglion in the substantia perforata
posterior, immediately in front of the pons, called the interpeduncular ganglion.
The interpeduncular ganglion has rather large nerve cells whose axons curve
backward and downward as the tegmental bundle of Gudden, to end partly in the
dorsal tegmental nucleus and surrounding gray substance where they come into
relation with association neurons and the dorsal longitudinal bundle of Schiitz.
The majority of the axons that arise from the mitral cells of the olfactory bulb
and course in the olfactory tract course in the lateral olfactory stria to the uncus
and hippocampal gyrus, and terminate in the cortex. Other fibers probably pass
to the uncus and hippocampal g\Tus from the primary olfactory centers in the
trigonum and anterior perforated substance. The g\Tus hippocampus is continued
through the isthmus into the gyrus cinguli which passes over the corpus callosum to
the area parolfactoria. The cortical portions of these gyri are connected together
by a thick association bundle, the cingulum, that lies buried in the depth of the
g>Tus cinguli extending forward to the parolfactory area and backward into the
hippocampal region. The axons from the g>Tus cinguli pass into the cingulum,
many of them bifurcate, the anterior branches together with the axons which run
in that direction are traceable as far forward as the anterior part of the septum
pellucidum and the anterior end of the corpus striatum, where some of them are
incorporated with projection fibers passing toward the- internal capsule. The
branches and axons which pass backward terminate partly in the hippocampus,
the dentate gyrus and hippocampal g>'rus. Shorter association fibers connect
various sections of the g^-rus fornicatus (cingulate g>TUs, isthmus, and hippocampal
g\'rus) and these with other regions of the cortex. These gyri constitute the cortical
center for smell.
The dentate gyrus which may be considered as a modified part of the hippo-
campus is partially separated from the gyrus hippocampus by the hippocampal fis-
sure and from the fimbria by the fimbrio-dentate sulcus; it is intimately connected
with the hippocampal gyrus and the hippocampus. When followed backward the
dentate gA'rus separates from the fimbria at the splenium, loses its incisions and
knobs, and as the fasciola cinerea passes o\'er the splenium onto the dorsal surface
of the corpus callosum and spreads out into a thin layer of gray substance knowii
as the indusium, which can be traced forward around the genu of the corpus
callosum into the g;\Tus subcallosus. The white matter of the indusium knowni
as the medial longitudinal striae {nerves of Lancisi) and the lateral longitudinal striae,
are related to the indusimn somewhat as the cingulum is to the g>Tus cinguli.
Axons from the indusium pass into the longitudinal stria^, some running forward
and others backward while some after entering the medial longitudinal stria, pierce
the corpus callosum to join the fornix. Some of the fibers which pass forward
extend around the front of the corpus callosum and the anterior commissure, then
curve doMiiward, according to Cajal, to enter the corpus striatum where they join
the olfactory projection-path. Other fibers are said to arise in the parolfactory
area, the gyrus subcallosus and the anterior perforated substance {diagonal band of
COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 869
Broca) nnd course backward in the longitudinal striiB to the dentate g>'rus and
the hippocampal region. The indusium is usualh' considered as a rudimentary
part of the rhinenccphalon.
The olfactory projection fibers which arise from the pyramid cells of the uncus and
hippocampus and from the i)olymorphic cells of the dentiite gyrus form a dense
stratum on the ventricular surface, especially on the hippocampus, called the alveus.
These fibers pass over into the fimbria and are continued into the fornix. About
one-fourth of all the fibers of the fimbria are large projection fibers, the other three-
fourths consist of fine commissural fibers wliich pass from the hii)pocampus of one
side through the fimbria and hippocampal commissure {ventral psaltcriim or lyre),
to the fimbria and hippocampus of the opposite side where they penetrate the pyram-
idal layer and terminate in the stratum radiatum. The fibers which course m the
fornix pass forward and downward into the corpora mammillare where numerous
collaterals are given off and a few terminate. Most of the fibers in the fornix,
however, pass through the corpora, cross the middle line and turn downward in
the reticular formation in which they are said to be traceable as far as the pons and
possibly farther. As the fornix passes beneath the corpus callosum it receives
fibers from the longitudinal striae of the indusium and from the cingulum; these are
the perforating fibers of the fornix which pass through the corpus callosum and
course in the fornix toward the mammillary body. As the fornix passes the anterior
end of the thalamus a few fibers are given off to the stria meduUaris of the thalamus
and turn back in the stria to the habenular ganglion of the same and the opposite
side, having probably the same relation that the reflex fibers have which arise from
the primary- centers and course in the stria medullaris of the thalamus. Aside from
the fibers of the fornix which pass through the mammillary body to decussate and
descend (as the mammillo-mesencephalic fasciculus), many fibers are said to pass
into the bimdle of Vicq d'Azyr, and one bundle of fibers is said to pass from the
fornix to the tuber cinereum.
The mammillary bodies receive collaterals and terminals then from the cortical
centers via the fornix and probably other collaterals and terminals are received
directly from the primary centers through the tractus olfactomesencephalicus.
According to Cajal fibers also reach the mammillary body through the peduncle
of the corpus mammillare from the arcuate fibers of the tegmentmn and from the
main fillet. The fornix probably brings the cortical centers into relation with the
reflex path that runs from the primary centers to the mammillary body and the
tuber cinereum.
The bundle of Vicq d'Azyr (mammillo-thalamic fasciciihis) arises from cells in both
the medial and lateral nuclei of the mammillary body and by fibers that are directly
continued from the fornix. There axons divide within the gray matter; the coarser
branches pass into the anterior nucleus of the thalamus as the bundle of Vicq d'Azyr,
the finer branches pass downward as the mammillo-tegmental bundle of Gudden.
The bundle of Vicq d'Azyr spreads out fan-like as it terminates in the anterior
or dorsal nucleus of the thalamus. A few of the fibers pass through the dorsal
nucleus to the angular nucleus of the thalamus. The axons from tliese nuclei are
supposed to form part of the thalamocortical system.
The mammillo-tegmental bundle has already been considered under the olfactory
reflex paths.
The amygdaloid nucleus and the taenia semicircularis {stria terminalis) probably
belong to the central olfactory apparatus. The taenia semicircularis extends from
the region of the anterior perforated substance to the nucleus amygdalae. Its
anterior connections are not clearly understood. Fibers are said to arise from cells
in the anterior perforated substance ; some of the fibers pass in front of the anterior
commissure, others join the fornix for a short distance as they pass behind the
anterior commissure. The two strands ultimately join to form the taenia and pass
870 NEUROLOGY
backward in the groove between the caudate nucleus and the thalamus to the
amygdaloid nucleus. Other fibers are said to pass in the opposite direction from
the amygdaloid nucleus to the thalamus.
PATHWAYS FROM THE BRAIN TO THE SPINAL CORD.
The descending fasciculi which con\"ey impulses from the higher centers to the
spinal cord and located in the lateral and ventral funiculi.
The Motor Tract (Fig. 76-i), conveying voluntary impulses, arises from the
pyramid cells situated in the motor area of the cortex, the anterior central and the
posterior portions of the frontal gyri and the paracentral lobule. The fibers are
at first somewhat widely diffused, but as they descend through the corona radiata
they gradually approach each other, and pass between the lentiform nucleus and
thalamus, in the genu and anterior two-thirds of the occipital part of the inter-
nal capsule; those in the genu are named the geniculate fibers, while the remainder
constitute the cerebrospinal fibers; proceeding downward they enter the middle
three-fifths of the base of the cerebral peduncle. The geniculate fibers cross the
middle line, and end by arborizing around the cells of the motor nuclei of the cra-
nial nerves. The cerebrospinal fibers are continued downward into the pyramids
of the medulla oblongata, and the transit of the fibers from the medulla oblongata
is efi'ected by two paths. The fibers nearest to the anterior median fissure cross
the middle line, forming the decussation of the pyramids, and descend in the
opposite side of the medulla spinalis, as the lateral cerebrospinal fasciculus {crossed
pyramidal tract). Throughout the length of the medulla spinalis fibers from this
column pass into the gray substance, to terminate either directly or indirectly
around the motor cells of the anterior column. The more laterally placed portion of
the tract does not decussate in the medulla oblongata, but descends as the anterior
cerebrospinal fasciculus {direct pyramidal tract) ; these fibers, however, end in the ante-
rior gray column of the opposite side of the medulla spinalis by passing across in the
anterior white commissure. There is considerable variation in the extent to which
decussation takes place in the medulla oblongata; about two-thirds or three-fourths
of the fibers usually decussate in the medulla oblongata and the remainder in the
medulla spinalis.
The axons of the motor cells in the anterior column pass out as the fibers of the
anterior roots of the spinal nerves, along which the impulses are conducted to the
muscles of the trunk and limbs.
From this it will be seen that all the fibers of the motor tract pass to the nuclei
of the motor nerves on the opposite side of the brain or medulla spinalis, a fact
which explains why a lesion involving the motor area of one side causes paralysis
of the muscles of the opposite side of the body. Further, it will be seen that there
is a break in the continuity of the motor chain; in the case of the cranial nerves
this break occurs in the nuclei of these nerves; and in the case of the spinal nerves,
in the anterior gray column of the medulla spinalis. For clinical purposes it is
convenient to emphasize this break and divide the motor tract into two portions:
(1) a series of upper motor neurons which comprises the motor cells in the cortex
and their descending fibers down to the nuclei of the motor nerves; (2) a series
of lower motor neurons which includes the cells of the nuclei of the motor cerebral
nerves or the cells of the anterior columns of the medulla spinalis and their axis-
cylinder processes to the periphery.
The rubrospinal fasciculus arises from the large cells of the red nucleus. The fibers
cross the raphe of the mid-brain in the decussation of Forel and descend in the
formatio reticularis of the pons and medulla dorsal to the medial lemniscus and as
they pass into the spinal cord come to lie in a position ventral to the crossed p>Tam-
idal tracts in the lateral funiculus. The rubrospmal fibers end either directly or
PATHWAYS FROM THE BRAIN TO THE SPINAL CORD
871
indirectly by terminals and collaterals about the motor cells in the anterior column
on the side opposite from their origin in the red nucleus. A few are said to pass
do\Mi on the same side. Since the red nucleus is intimateh- related to the cerebellum
by terminals and collaterals of the superior i)eduncle which arises in the dentate
nucleus of the cerebellum, the rubrospinal fasciculus is supposed to be concerned
Geniculate fibers
Motor area of
cortex
Internal
capsvle
Decussation of pyramids
Anterior cerebrospinal fasciculus
Lateral cerebrospinal fascicidius
V - - •» Anterior nerve roots
Flo. 764. — The motor tract. (Modified from Poirier.)
with cerebellar reflexes, complex motor coordinations necessary in locomotion and
equilibrium. The aft'erent paths concerned in these reflexes have already been
partly considered, namely, the dorsal and ventral spinocerebellar fasciculi, and
probably some of the fibers of the posterior funiculi which reach the cerebellum by
the inferior peduncle.
The tectospinal fasciculus arises from the superior colliculus of the roof (tectum)
872 NEUROLOGY
of the mid-brain. The axons come from large cells in the stratum opticum and
stratum lemnisci and sweep ventrally around the central gray matter of the aque-
duct, cross the raphe in the fountain decussation of Meynert and turn doAMiMard
in the tegmentimi in the ventral longitudinal bundle. Some of the fibers do not
cross in the raphe but pass do\\ii on the same side; it is uncertain whether they come
from the superior colliculus of the same side or arch over the aqueduct from the
colliculus of the opposite side. The tectospinal fasciculus which comprises the
major part of the ventral longitudinal bundle passes dovn\ through the tegmentum
and reticular formation of the pons and medulla oblongata \'entral to the medial
longitudinal bundle. In the medulla the two bundles are more or less intermingled
and the tectospinal portion is continued into the antero-lateral funiculus of the
spinal cord ventral to the rubrospinal fasciculus with which some of its fibers are
intermingled. Some of the fibers of the tectospinal fasciculus pass through the red
nucleus giving off collaterals to it, others are gi^•en off to the motor nuclei of the
cranial nerves and in the spinal cord they terminate either directly or indirectly
by terminals and collaterals among the nuclei of the anterior column. Since the
superior colliculus is an important optic reflex center, this tract is probably con-
cerned in optic reflexes; and possibly also with auditory reflexes since some of the
fibers of the central auditory path, the lateral lemniscus, terminate in the superior
colliculus.
The vestibulospinal fasciculus (part of the anterior margiyiaJ foscintJjif; or Loeiren-
ihaVs tract) situated chiefly in the marginal part of the anterior finiiculus is mainly
derived from the cells of the terminal nuclei of the vestibular nerve, probably
Deiters's and Bechterew's, and some of its fibers are supposed to come from the
nucleus fastigius (roof nucleus of the cerebellum). The latter nucleus is intimately
connected with Dieters's and Bechterew's nuclei. The vestibulospinal fasciculus
is concerned with equilibratory reflexes. Its terminals and collaterals end about
the motor cells in the anterior column. It extends to the sacral region of the cord.
Its fibers are intermingled with the ascending spinothalamic fasciculus, with the
anterior proper fasciculus and laterally with the tectospinal fasciculus. Its fibers
are supposed to be both crossed and uncrossed. In the brain-stem it is associated
with the dorsal longitudinal bundle.
The pontospinal fasciculus {Bcchtcrew) arises from the cells in the reticular forma-
tion of the pons from the same and the opposite side and is associated in the brain-
stem with the ventral longitudinal bundle. In the cord it is intermingled with the
fibers of the vestibulospinal fasciculus in the anterior funiculus. Not much is known
about this tract.
There are probabh' other descending fasciculi such as the thalamospinal but not
much is knoAMi about them.
MENINGES OF THE BRAIN AND MEDULLA SPINALIS.
The brain and medulla spinalis are enclosed within three membranes. These
are named from without inward : the dura mater, the arachnoid, and the pia mater.
The Dura Mater.
The dura mater is a thick and dense inelastic membrane. The portion which
encloses the brain differs in several essential particulars from that which surrounds
the medulla spinalis, and therefore it is necessary to describe them separately;
but at the same time it must be distinctly understood that the two form one com-
plete membrane, and are continuous with each other at the foramen magnum.
The Cranial Dura Mater (dura mater encephali; dura of the braui) lines the
interior of the skull, and serves the twofold purpose of an internal periosteum
THE DURA MATER
873
to the bones, and a membrane for the protection of the brain. It is composed of
two layers, an inner or meningeal and an outer or endosteal, closely connected
together, except in certain situations, where, as already described (page ()o4),
they separate to form sinuses for the passage of venous blood. Its outer surface
is rough and fibrillated, and adheres closely to the inner surfaces of the bones,
the adhesions being most marked opposite the sutures and at the base of the skull
its inner surface is smooth and lined by a layer of endothelium. It sends inward
four processes which divide the cavity of the skull into a series of freely communicat-
ing compartments, for the lodgement and protection of the difl'erent parts of the
brain; and it is prolonged to the outer surface of the skull, through the various
foramina which exist at the base, and thus becomes continuous with the peri-
cranium; its fibrous layer forms sheaths for the nerves which pass through these
apertures. Around the margin of the foramen magnum it is closely adherent to
the bone, and is continuous with the spinal dura mater.
Great cerebral vein
Glossophanjmjeal nerve
Vagus ■nerve
Accessory nerve
Acoustic nerve |
Facial nerce \
Abdiicent nerve Trigeminal nerve
Fig. 765. — Dura mater and its processes exposed by removing part of the right half of the skull and the brain.
Optic nerves
Ophthalmic artery
Diaphragma sellce
Oculomotor nerves
Trochlear nerve
Processes. — The processes of the cranial dura mater, which projects into the
cavity of the skull, are formed by reduplications of the inner or meningeal layer
of the membrane, and are four in number: the falx cerebri, the tentorium cerebeUi,
the falx cerebeUi, and the diaphragma sellae.
The falx cerebri (Fig. 765), so named from its sickle-like form, is a strong, arched
process which descends vertically in the longitudinal fissure between the cerebral
hemispheres. It is narrow in front, where it is attached to the crista galli of the
ethmoid; and broad behind, where it is connected with the upper surface of the
874
NEUROLOGY
tentorium cerebelli. Its upper margin is convex, and attached to the inner surface
of the skull in the middle line, as far back as the internal occipital protuberance;
it contains the superior sagittal sinus. Its lower margin is free and concave, and
contains the inferior sagittal sinus.
The tentorium cerebelli (Fig. 766) is an arched lamina, elevated in the middle,
and inclining downward toward the circumference. It covers the superior surface
of the cerebellum, and supports the occipital lobes of the brain. Its anterior border
is free and concave, and bounds a large oval opening, the incisura tentorii, for the
transmission of the cerebral peduncles. It is attached, behind, by its convex border,
to the transverse ridges upon the inner surface of the occipital bone, and there
encloses the transverse sinuses; in front, to the superior angle of the petrous part
Optic nerve
Diaphragma selloB
Free margin of tentorium \
Internal carotid artery
Oculomotor nerve
Attached margin of tentorium
Fig.
End of superior sagittal sinus
766. — Tentorium cerebelli seen from above.
of the temporal bone on either side, enclosing the superior petrosal sinuses. At
the apex of the petrous part of the temporal bone the free and attached borders
meet, and, crossing one another, are continued forward to be fixed to the anterior
and posterior clinoid processes respectively. To the middle line of its upper surface
the posterior border of the falx cerebri is attached, the straight sinus being placed
at their line of junction.
The falx cerebelli is a small triangular process of dura mater, received into the
posterior cerebellar notch. Its base is attached, above, to the under and back part
of the tentorium; its posterior margin, to the lower division of the vertical crest
on the inner surface of the occipital bone. As it descends, it sometimes divides
into two smaller folds, which are lost on the sides of the foramen magnum.
The diaphragma sellae is a small circular horizontal fold, which roofs in the sella
turcica and almost completely covers the hypophysis; a small central opening
transmits the infundibulum.
THE DURA MATER
875
Structure. — The cranial dura mater consists of white fibrous tissue and elastic fibers arranged
in flattened lamin* which are imperfectly separated by lacninar spaces and bloodvessels into
two layers, endosteal and meningeal. The endosteal layer is the internal periosteum for the
cranial bones, and contains the bloodvessels for their supply. At the margin of the foramen
magnum it is continuous with the periosteum lining the vertebral canal. The meningeal or
supporting layer is lined on its inner surface by a layer of nucleated flattened niesothelium,
similar to that found on serous membranes.
The arteries of the dura mater are very numerous. Those in the anterior fossa are the anterior
meningeal branches of the anterior and posterior ethmoidal and internal carotid, and a branch
from the middle meningeal. Those in the middle fossa are the middle and accessory meningeal
of the internal maxillary; a branch from the ascending pharyngeal, which enters the skull through
the foramen lacerum; branches from the internal carotid, and a recurrent branch from the lacrimal.
Those in the posterior fossa are meningeal branches from the occipital, one entering the skull
through the jugular foramen, and another through the mastoid foramen; the posterior meningeal
from the vertebral; occasional meningeal branches from the ascending pharyngeal, entering the
skull through the jugular foramen and hypoglossal canal; and a branch from the middle meningeal.
The veins returning the blood from the cranial dura mater anastomose with the diploic veins
and end in the various sinuses. Many of the meningeal veins do not open directly into the sinuses,
but indirectly through a series of ampullae, termed venous lacunae. These are found on either
side of the superior sagittal sinus, especially near its middle portion, and are often invaginated
by arachnoid granulations; they also exist near the transverse and straight sinuses. They
communicate with the underlying cerebral veins, and also with the diploic and emissary veins.
The nerves of the cranial dura mater are filaments from the semilunar ganglion, from the
ophthalmic, maxillary, mandibular, vagus, and hypoglossal nerves, and from the sympathetic.
The Spinal Dura Mater {dura mater spinalis; spinal dura) (Fig. 767) forms a
loose sheath around the medulla spinalis, and represents only the inner or meningeal
layer of the cranial dura mater; the outer or endosteal layer ceases at the foramen
magnum, its place being taken by the periosteum lining the vertebral canal. The
spinal dura mater is separated from the arachnoid by a potential cavity, the sub-
dural cavity; the two membranes are, in fact, in contact with each other, except
where they are separated by a minute quantity of
fluid, which serves to moisten the apposed surfaces.
It is separated from the wall of the vertebral canal
by a space, the epidural space, which contains a quan-
tity of loose areolar tissue and a plexus of veins; the
situation of these veins between the dura mater and
the periosteum of the vertebrae corresponds therefore
to that of the cranial sinuses between the meningeal
and endosteal layers of the cranial dura mater. The
spinal dura mater is attached to the circumference of
the foramen magnum, and to the second and third
cervical vertebrae; it is also connected to the pos-
terior longitudinal ligament, especially near the lower
end of the vertebral canal, by fibrous slips. The
subdural cavity ends at the lower border of the second
sacral vertebra; below this level the dura mater closely
invests the filum terminale and descends to the back of
the coccyx, where it blends with the periosteum. The
sheath of dura mater is much larger than is necessary
for the accommodation of its contents, and its size is
greater in the cervical and lumbar regions than in
the thoracic. On each side may be seen the double
openings which transmit the two roots of the corre-
sponding spinal nerve, the dura mater being continued
in the form of tubular prolongations on them as they pass through the interverte-
bral foramina. These prolongations are short in the upper part of the vertebral
column, but gradually become longer below, forming a number of tubes of fibrous
membrane, which enclose the lower spinal nerves and are contained in the verte-
bral canal.
Dura I'lalcr
Fia.
767. — The medulla spinalis and
its membranes.
S76 NEUROLOGY
Structiire. — The spinal dura mater resembles in structure the meningeal or supporting layer
of the cranial dura mater, consisting of white fibrous and elastic tissue arranged in banda or
lamellae which, for the most part, are parallel with one another and have a longitudinal arrange-
ment. Its internal surface is smooth and covered by a layer of mesothelium. It is sparingly
supplied with bloodvessels, and a few nerves have been traced into it.
The Arachnoid.
The arachnoid is a delicate membrane enveloping the brain and medulla spinalis
and lying between the pia mater internally and the dura mater externally; it is
separated from the pia mater by the subarachnoid cavity, which is filled with
cerebrospinal fluid.
The Cranial Part (arachnoidea encephali) of the arachnoid invests the brain
loosely, and does not dip into the sulci between the gyri, nor into the fissures, with
the exception of the longitudinal. On the upper surface of the brain the arachnoid
is thin and transparent; at the base it is thicker, and slightly opaque toward the
central part, where it extends across between the two temporal lobes in front
of the pons, so as to leave a considerable interval between it and the brain.
The Spinal Part {arachnoidea spinalis) of the arachnoid is a thin, delicate, tubular
membrane loosely investing the medulla spinalis. Above, it is continuous with
the cranial arachnoid; below, it widens out and invests the cauda equina and the
nerves proceeding from it. It is separated from the dura mater by the subdural
space, but here and there this space is traversed by isolated connective-tissue
trabeculae, which are most numerous on the posterior surface of the medulla spinalis.
The arachnoid surrounds the cranial and spinal nerves, and encloses them
in loose sheaths as far as their points of exit from the skull and vertebral canal.
Structure. — The arachnoid consists of bimdles of white fibrous and elastic tissue intimately
blended together. Its outer surface is covered with a layer of low cuboidal mesothelium. The
inner surface and the trabecuhr are likewise covered by a somewhat low type of cuboidal meso-
thelium which in places are flattened to a pavement type. Vessels of considerable size, but few
in number, and, according to Bochdalek, a rich ple.xus of nerves derived from the motor root
of the trigeminal, the facial, and the accessorj- nerves, are found in the arachnoid.
The Subarachnoid Cavity {camnn subarachnoideale; subarachnoid space) is the
interval between the arachnoid and pia mater. It is occupied by a spongy tissue
consisting of trabecule of delicate connective tissue, and intercommunicating
channels in which the subarachnoid fluid is contained. This cavity is small on the
surface of the hemispheres of the brain; on the summit of each gyrus the pia mater
and the arachnoid are in close contact; but in the sulci between the gyri, triangular
spaces are left, in which the subarachnoid trabecular tissue is found, for the pia
mater dips into the sulci, whereas the arachnoid bridges across them from gyrus to
gyrus. At certain parts of the base of the brain, the arachnoid is separated from the
pia mater by wide intervals, which communicate freely with each other and are
named subarachnoid cistemse; in these the subarachnoid tissue is less abundant.
Subarachnoid Cisternae (cisternal subarachnoidales) (Fig. 768).^ — The cistema
cerebellomedullaris (cistema magna) is triangular on sagittal section, and results
from the arachnoid bridging over the interval between the medulla oblongata
and the under surfaces of the hemispheres of the cerebellum; it is continuous
with the subarachnoid cavity of the medulla spinalis at the level of the foramen
magnum. The cistema pontis is a considerable space on the ventral aspect of the
pons. It contains the basilar artery, and is continuous behind with the subarach-
noid cavity of the medulla spinalis, and with the cisterna cerebellomedullaris; and
in front of the pons with the cisterna interpeduncularis. The cistema interpeduncu-
laris {cisterna basalis) is a wide cavity where the arachnoid extends across between
the two temporal lobes. It encloses the cerebral peduncles and the structures
contained in the interpeduncular fossa, and contains the arterial circle of Willis.
THE ARACHNOID
877
In front, the cisterna interpeduncularis extends forward across the optic chiasma,
forming the cisterna chiasmatis, and on to the upper surface of the corpus callosum,
for the arachnoid stretches across from one cerebral hemisphere to the other immedi-
ately beneath the free border of the falx cerebri, and thus leaves a space in which
the anterior cerebral arteries are contained. The cisterna fossae cerebri lateralis is
formed in front of either temporal lobe by the arachnoid bridging across the lateral
fissure. This cavity contains the middle cerebral artery. The cisterna venae
magnae cerebri occupies the interval between the splenium of the corpus callosum
and the superior surface of the cerebellum; it extends between the layers of the tela
chorioidea of the third ventricle and contains the great cerebral vein.
Optic chiasma
Cisterna interpeduncularis
Fourth ventricle
Cisterna pontis
Cisterna
certhellomedullaris
Fig. 768. — Diagram shcrvrtng the positions of the three principal subarachnoid cistemae.
The subarachnoid cavity communicates with the general ventricular cavity
of the brain by three openings; one, the foramen of Majendie, is in the middle line
at the inferior part of the roof of the fourth ventricle; the other two are at the
extremities of the lateral recesses of that ventricle, behind the upper roots of the
glossopha^^^lgeal nerves and are kno^^^l as the foramina of Luschka. It is still some-
what uncertain whether these foramina are actual openings or merely modified areas
of the inferior \elum which permit the passage of the cerebrospinal fluid from the
ventricle into the subarachnoid spaces as through a permeable membrane.
The spinal part of the subarachnoid cavity is a very wide interval, and is the
largest at the lower part of the vertebral canal, where the arachnoid encloses
the nerves which form the cauda equina. Above, it is continuous with the cranial
subarachnoid cavity; below, it ends at the level of the lower border of the second
sacral vertebra. It is partially divided by a longitudinal septum, the subarachnoid
septum, which connects the arachnoid with the pia mater opposite the posterior
median sulcus of the medulla spinalis, and forms a partition, incomplete and cribri-
form above, but more perfect in the thoracic region. The spinal subarachnoid
cavity is further subdivided by the ligamentum denticulatum, which will be described
with the pia mater.
The cerebrospinal fluid is a clear limpid fluid, having a saltish taste, and a shghtly alkaline
reaction. According to Lassaigne, it consists of 98.5 parts of water, the remaining 1.5 per cent,
being soUd matters, animal and saline. It varies in quantity, being most abundant in old persons,
and is quickly secreted.
878
NEUROLOGY
The Arachnoid Villi {granulaiiones arachnoideales ; glandid(FPacchioni; Pacchio-
nian bodies) (Fig. 769) are small, fleshy-looking elevations, usually collected into
clusters of variable size, Avhich are present upon the outer surface of the dura
mater, in the vicinity of the superior sagittal sinus, and in some other situations.
Upon laj'ing open the sagittal sinus and the venous lacunae on either side of it
villi will be found protruding into its interior. They are not seen in infancy,
and Aery rarely until the third year. They are usually found after the seventh
year; and from this period they increase in number and size as age advances.
They are not glandular in structure, but are enlarged normal villi of the arach-
noid. As they grow they push the thinned dura mater before them, and cause
absorption of the bone from pressure, and so produce the pits or depressions
on the inner wall of the calvarium.
Emissary vein
Venous lacuna \ Sujt. sagittal sinus
Cerebral vein
Meningeal vein
Arachnoid granulation
Subdural cavity
Subarachnoid cavity
Falx cerebri
Pia mater
mm
y--:::-.^:<T-'
Fig. 769. — Diagrammatic representation of a section across the top of the skull, showing the membranes of the
brain, etc. (Modified from Testut.)
mm.,..
Dura mater
Arachnoid
- Cerebral cortex
Structure. — An arachnoidal \t11us represents an invasion of the dura by the arachnoid mem-
brane, the latter penetrates the dura in such a manner that the arachnoid mesothelial cells come
to lie directly beneath the vascular endothelium of the great dural sinuses. It consists of the
follo^\'ing parts: (1) In the interior is a core of subarachnoid tissue, continuous with the mesh-
work of the general subarachnoid tissue through a narrow pedicle, by which the xiWus, is attached
to the arachnoid. (2) Around this tissue is a layer of arachnoid membrane, limiting and enclosing
the subarachnoid tissue. (3) Outside this is the thinned wall of the lacuna, wliich is separated
from the arachnoid by a potential space which corresponds to and is continuous \\\\h the subdural
ca\'ity. (4) And finally, if the villus projects into the sagittal sinus, it will be covered by the
greatly thinned wall of the sinus which may consist merely of endothelium. It will be seen, there-
fore, that fluid injected into the subarachnoid cavity will find its way into these \\\\\, and it has
been found experimentally that it passes from the \\\\i into the venous sinuses into which they
project.
The Pia Mater.
The pia mater is a vascular membrane, consisting of a minute plexus of blood-
vessels, held together by an extremely fine areolar tissue and covered by a reflexion
of the mesothelial cells from the arachnoid trabecuUe. It is an incomplete mem-
THE PI A MATER
879
brane, absent probably at the foramen of Majendie and the two foramina of Luschka
and perforated in a pecuHar manner by all the bloodvessels as they enter or leave
the nerxous system. In the perixascular spaces, the pia apjiarently enters as a
mesothelial lining of the outer surface of the space; a variable distiince from the
exterior these cells become unrecognizable and are apparently lacking, replaced by
neuroglia elements. The inner walls of these perivascular spaces seem likewise
covered for a certain distance b>' the mesothelial cells, reflected with the vessels
from the arachnoid covering of these vascular channels as they traverse the sub-
arachnoid spaces.
The Cranial Pia, Mater (pia mater encephali; pia of the brain) invests the entire
surface of the brain, dips between the cerebral gyri and cerebellar laminae, and is
invaginated to form the tela chorioidea of the third ventricle, and the choroid
plexuses of the lateral and third ventricles (pages 840 and 841); as it passes over
the roof of the fourth ventricle, it forms the tela chorioidea and the choroid
plexuses of this ventricle. On the cerebellum the membrane is more delicate; the
vessels from its deep surface are shorter, and its relations to the cortex are not
so intimate.
Subdural cavity
Pia mater
Arachnoid ,^
Dura mater
Subdural cavity
FiQ. 770. — Diagrammatic transverse section of the medulla spinalis and its membranes.
The Spinal Pia Mater (pia mater sjmialis; pia of the cord) (Figs. 767, 770) is
thicker, firmer, and less vascular than the cranial pia mater: this is due to the fact
that it consists of two layers, the outer or additional one being composed of bundles
of connective-tissue fibers, arranged for the most part longitudinally^. Between
the layers are cleft-like spaces which communicate with the subarachnoid cavity,
and a number of bloodvessels which are enclosed in perivascular lymphatic sheaths.
The spinal pia mater covers the entire surface of the medulla spinalis, and is very
intimately adherent to it; in front it sends a process backward into the anterior
fissure. A longitudinal fibrous band, called the linea splendens, extends along the
middle line of the anterior surface; and a somewhat similar band, the ligamentum
denticulatum, is situated on either side. Below the conus medullaris, the pia mater
is continued as a long, slender filament (filum terminale), which descends through
the center of the mass of nerves forming the cauda equina. It blends with the
dura mater at the level of the lower border of the second sacral vertebra, and extends
downward as far as the base of the coccyx, where it fuses with the periosteum. It
assists in maintaining the medulla spinalis in its position during the movements
of the trunk, and is, from this circumstance, called the central ligament of the
medulla spinalis.
The pia m.ater forms sheaths for the cranial and spinal nerves; these sheaths
are closely connected with the nerves, and blend with their common membranous
investments.
880 . NEUROLOGY
The ligamentum denticulatum {dentate ligament) (Fig. 767) is a narrow fibrous
band situated on either side of the medulla spinahs throughout its entire length,
and separating the anterior from the posterior nerve roots. Its medial border is
continuous with the pia mater at the side of the medulla spinalis. Its lateral
border presents a series of triangular tooth-like processes, the points of which are
fixed at intervals to the dura mater. These processes are twenty-one in rmmber,
on either side, the first being attached to the dura mater, opposite the margin
of the foramen magnum, between the vertebral artery and the hypoglossal nerve;
and the last near the lower end of the medulla spinalis.
THE CEREBROSPINAL FLUID. ^
The cerebrospinal fluid, for the most part elaborated by the choroid plexuses,
is poured into the cerebral ventricles which are lined by smooth ependyma. That
portion of the fluid formed in the lateral ventricles escapes by the foramen of Monro
into the third ventricle and thence by the aqueduct into the fourth ventricle.
Likewise an ascending current of fluid apparently occurs in the central canal of
the spinal cord; this, representing a possible product of the ependyma, may be added
to the intraventricular supply. From the fourth ventricle the fluid is poured into
the subarachnoid spaces through the medial foramen of Majendie and the two
lateral foramina of Luschka. There is no evidence that functional communications
between the cerebral ventricles and the subarachnoid spaces exist in any region
except from the fourth ventricle.
In addition to the elaboration of the cerebrospinal fluid by the choroid plexuses,
there seems fairly well established a second source of the fluid from the nervous
system itself. The bloodvessels that enter and leave the brain are surrounded by
perivascular channels. It seems most likely that the outer wall of these channels is
lined by a continuation inward of the pial mesothelium while the inner wall is
probably derived from the mesothelial covering of the vessels, which are thus
protected throughout the subarachnoid spaces. These mesothelial cells continue
inward only a short distance, neuroglia cells probably replacing on the outer surface
the mesothelial elements. Through these perivascular channels there is probably
a small amount of fluid flowing from nerve-cell to subarachnoid space. The chemical
difterences between the subarachnoid fluid (product of choroid plexuses and peri-
vascular system) and the ventricular fluid (product of choroid plexuses alone)
indicate that the products of nerve-metabolism are poured into the subarachnoid
space.
The absorption of the cerebrospinal fluid is a dual process, being chiefly a rapid
drainage through the arachnoid villi into the great dural sinuses, and, in small part,
a slow escape into the true lymphatic vessels, by way of an abundant but indirect
perineural course.
In general the arachnoid channels are equipped as fluid retainers with unques-
tionable powers of difl'usion or absorption in regard to certain elements in the
normal cerebrospinal fluid, deriving in this way a cellular nutrition.
The subdural space (between arachnoid and dura) is usually considered to be a
part of the cerebrospinal channels. It is a very small space, the two limiting sur-
faces being separated by merely a capillary layer of fluid. ^Vhether this fluid is
exactly similar to the cerebrospinal fluid is very difficult to ascertain. Likewise
our knowledge of the connections between the subdural and subarachnoid spaces
is hardly definite. In some ways the subdural space may be likened to a serous
cavity. The inner surface of the dura is covered by flattened polygonal mesothelial
cells but the outer surface of the arachnoid is covered by somewhat cuboidal meso-
thelium. The fluid of the subdural space has probably a local origin from the cells
lining it.
Weed. L. H , Anat. Record, 1917, 12.
THE OLFACTORY NERVES
881
THE CRANIAL NERVES (NERVI CEREBRALES; CEREBRAL NERVES).
There are twelve pairs of cranial nerves; they are attached to the brain and
are transmitted through foramina in the base of the cranium. The difi'erent pairs
are named from before backward as follows:
1st. Olfactory. 7th. Facial.
2d. Optic. 8th. Acoustic.
3d. Oculomotor. 9th. Glossopharyngeal.
4th. Trochlear. 10th. Vagus.
5th. Trigeminal. 11th. Accessory.
6th. Abducent. 12th. Hypoglossal.
The area of attachment of a cranial nerve to the surface of the brain is termed
its superficial or apparent origin. The fibers of the nerve can be traced into the sub-
stance of the brain to a special nucleus of gray substance. The motor or efferent
cranial nerves arise within the brain from groups of nerve cells which constitute
their nuclei of origin. The sensory or afferent cranial nerves arise from groups
of nerve cells outside the brain; these nerve cells may be grouped to form ganglia
on the trunks of the nerves or may be situated in peripheral sensory organs such
as the nose and eye. The central processes of these cells run into the brain, and
there end by arborizing around nerve cells, which are grouped to form nuclei of
termination. The nuclei of origin of the motor nerves and the nuclei of termination
of the sensory nerves are brought into relationship with the cerebral cortex, the
former through the geniculate fibers of the internal capsule, the latter through
the lemniscus. The geniculate fibers arise from the cells of the motor area of the
cortex, and, after crossing the middle line, end by arborizing around the cells of the
nuclei of origin of the motor cranial nerves. On the other hand, fibers arise from
the celFs of the nuclei of termination of the sensory nerves, and after crossing to
the opposite side, join the lemniscus, and thus connect these nuclei, directly or
indirectly, with the cerebral cortex.
THE OLFACTORY NERVES (NN. OLFACTORII; FIRST NERVE) (Fig. 771).
The olfactory nerves or nerves of smell are distributed to the mucous membrane
of the olfactory region of the nasal cavity : this region comprises the superior nasal
Fibers of olfactory
tract
Mitral cells
;— Glomeruli
Olfactory cell
Olfactory
epithelium
FiQ. 771. — Nerves of septum of nose. Right side.
Fig. 772. — Plan of olfactory neurons.
concha, and the corresponding part of the nasal septum. . The nerves originate
from the central or deep processes of the olfactory, cells of the nasal mucous mem-
56
882
NEUROLOGY
brane. They form a plexiform net-work in the mucous membrane, and are then
collected into about twenty branches, which pierce the cribriform plate of the eth-
moid bone in two groups, a lateral and a medial group, and end in the glomeruli
of the olfactory bulb (Fig. 772). Each branch receives tubular sheaths from the
dura mater and pia mater, the former being lost in the periosteum of the nose,
the latter in the neurolemma of the nerve.
The olfactory nerves are non-medullated, and consist of axis-cylinders surrounded
by nucleated sheaths, in which, however, there are fewer nuclei than are found in
the sheaths of ordinary non-medullated nerve fibers.
The olfactory center in the cortex is generally associated with the rhinencephalon
(page 826).
The olfactary nerves are developed from the cells of the ectoderm which lines
the olfactory pits; these cells undergo proliferation and give rise to what are termed
the olfactory cells of the nose. The axons of the olfactory cells grow into the over-
lying olfactory bulb and form the olfactory nerves.
THE OPTIC NERVE (N. OPTICUS; SECOND NERVE) (Fig. 773).
The optic nerve, or nerve of sight, consists mainly of fibers derived from the gan-
glionic cells of the retina. These axons terminate in arborizations around the cells
in the lateral geniculate body, pulvinar, and
superior colliculus which constitute the lower
or primary visual centers. From the cells of
the lateral geniculate body and the pulvinar
fibers pass to the cortical visual center, situated
in the cuneus and in the neighborhood of the
calcarine fissure. A few fibers of the opti^ nerve,
of small caliber, pass from the primary centers
to the retina and are supposed to govern
chemical changes in the retina and also the
movements of some of its elements (pigment
cells and cones) . There are also a few fine fibers,
afferent fibers, extending from the retina to the
brain, that are supposed to be concerned in
pupillary reflexes.
The optic nerve is peculiar in that its fibers
and ganglion cells are probably third in the
series of neurons from the receptors to the
brain. Consequently the optic nerve corre-
sponds rather to a tract of fibers Avithin the brain than to the other cranial
nerves. Its fibers pass backward and medialward through the orbit and optic
foramen to the optic commissure where they partially decussate. The mixed fibers
from the two nerves are continued in the optic tracts, the primary visual centers
of the brain.
The orbital portion of the optic nerve is from 20 mm. to 80 mm. in length and has
a slightly sinuous course to allow for movements of the eyeball. It is invested by
an outer sheath of dura mater and an inner sheath from the arachnoid which are
attached to the sclera around the area where the nerve fibers pierce the choroid
and sclera of the bulb. A little behhid the bulb of the eye the central artery of the
retina with its accompanying vein perforates the optic nerve, and runs within it
to the retina. As the nerve enters the optic foramen its dural sheath becomes
continuous with that lining the orbit and the optic foramen. In the optic foramen
the ophthalmic artery lies below and to its outer side. The intercranial portion
of the optic nerve is about 10 mm. in length.
Fig. 773. — The left optic nerve and the
optic tracts.
THE OPTIC NERVE
883
The Optic Chiasma (chiasma opticum), somewhat quadrilateral in form, rests
upon the tuberculum sellse and on the anterior part of the diaphragma sellae.
It is in relation, above, with the lamina terminalis; behind, with the tuber cinereum;
on either side, with the anterior perforated substance. Within the chiasma, the
optic nerves undergo a partial decussation. The fibers forming the medial part of
each tract and posterior part of the chiasma have no connection with the optic
nerves. They simply cross in the chiasma, and connect the medial geniculate
bodies of the two sides; they form the commissure of Gudden. The remaining and
principal part of the chiasma consists of two sets of fibers, crossed and uncrossed.
The crossed fibers which are the more numerous, occupy the central part of the
chiasma, and pass from the optic nerve of one side to the optic tract of the other,
decussating in the chiasma with similar fibers of the opposite optic nerve. The
uncrossed fibers occupy the lateral part of the chiasma, and pass from the nerve
of one side into the tract of the same side.^
Optic nerve
Crossed fibers
Uncrossed fibers
Optic chiasma
Optic tract
Commissure of Gvdden
Pulrinar
Lateral geniculate body
Superior colliculus
Medial geniculate body
Nii£leus of oculomotor nerve
Nucleiis of trocMear nerve
Nucleus of abducent nerve
Cortex of occipital lobes
Fig. 774. — Scheme showing central connections of the optic nerves and optic tracts.
The crossed fibers of the optic nerve tend to occupy the medial side of the nerve
and the uncrossed fibers the lateral side. In the optic tract, however, tiie fibers
are much more intermingled.
1 A specimen of congenital absence of the optic chiasma is to be found in the Museum of the Westminister Hospital.
See also Henle, Nervenlehre, p 393, ed. 2. »
884
NEUROLOGY
The Optic Tract (Fig. 774), passes backward and outward from the optic chiasma
over the tuber cinereum and anterior perforated space to the cerebral peduncle
and winds obliquely across its under surface. Its fibers terminate in the lateral
geniculate body, the pulvinar and the superior colliculus. It is adherent to the
tuber cinereum and the cerebral pedvmcle as it passes over them. In the region of
the lateral geniculate body it splits into two bands. The medial and smaller one is
a part of the commissure of Gudden and ends in the medial geniculate body.
From its mode of development, and from its structure, the optic nerve must be regarded as a
prolongation of the brain substance, rather than as an ordinary cerebrospinal nerve. As it
passes from the brain it receives sheaths from the three cerebral membranes, a perineural
sheath from the pia mater, an intermediate sheath from the arachnoid, and an outer sheath
from the dura mater, which is also connected with the periosteum as it passes through the
optic foramen. These sheaths are separated from each other bj' cavities which communicate
with the subdural and subarachnoid cavities respectively. The innermost or perineural sheath
sends a process around the arteria centralis retina? into the interior of the nerve, and enters
intimately into its structure.
THE OCULOMOTOR NERVE (N. OCULOMOTORIUS ; THIRD NERVE)
(Figs. 775, 776, 777).
The oculomotor nerve supplies somatic motor fibers to all the ocular muscles,
except the Obliquus superior and Rectus lateralis; it also supplies through its
connections with the ciliary ganglion, sympathetic motor fibers to the Sphincter
pupillge and the Ciliaris muscles.
: LEVATOR PALPEBR/E
ECTUS SUPERIOR
To Caxx^mous pleTus
iary ganglion
Short ciliary
ECTUS MEDiAUra
ECTUS INFERIOR
OBLIQUUS INFERIOR
Fig. 775
-Plan of oculomotor nerve.
The fibers of the oculomotor ner\e arise from a nucleus which lies in the gray
substance of the floor of the cerebral aqueduct and extends in front of the aqueduct
for a short distance into the floor of the third ^■entricle. From this nucleus the
fibers pass forward through the tegmentum, the red nucleus, and the medial part
of the substantia nigra, forming a series of curves with a lateral convexity, and
emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.
The nucleus of the oculomotor nerve does not consist of a continuous column
of cells, but is broken up into a number of smaller nuclei, which are arranged in
two groups, anterior and posterior. Those of the posterior group are six in number,
five of which are symmetrical on the two sides of the middle line, while the sixth
is centrally placed and is common to the nerves of both sides. The anterior group
consists of two nuclei, an antero-medial and an antero-lateral (Fig. 762).
The nucleus of the oculomotor nerve, considered from a physiological standpoint,
can be subdivided into several smaller groups of cells, each group controlling a
particular muscle.
On emerging from the brain, the nerve is invested with a sheath of pia mater,
and enclosed in a prolongation from the arachnoid. It passes between the superior
cerebellar and posterior cerebral arteries, and then pierces the dura mater in front
THE TROCHLEAR NERVE
885
of and lateral to the posterior clinoid process, passing between the free and attached
borders of the tentorium cerebelli. It runs along the lateral wall of the cavernous
sinus, above the other orbital nerves, receiving in its course one or two filaments
from the cavernous plexus of the sympathetic, and a communicating branch from
the ophthalmic division of the trigeminal. It then divides into two branches,
which enter the orbit through the superior orbital fissure, between the two heads
of the Rectus lateralis. Here the nerve is placed below the trochlear nerve and
the frontal and lacrimal branches of the ophthalmic nerve, while the nasociliary
nerve is placed between its two rami.
The superior ramus, the smaller, passes medialward over the optic nerve, and
supplies the Rectus superior and Levator palpebral superioris. The inferior ramus,
the larger, divides into three branches. One passes beneath the optic nerve to the
Rectus medialis; another, to the Rectus inferior; the third and longest runs for-
ward between the Recti inferior and lateralis to the Obliquus inferior. From
the last a short thick branch is given off to the lower part of the ciliary ganglion,
and forms its short root. All these branches enter the muscles on their ocular
surfaces, with the exception of the nerve to the Obliquus inferior, which enters
the muscle at its posterior border.
Infra-
trochlear
nerve
THE TROCHLEAR NERVE {N. TROCHLEARIS; FOURTH NERVE) (Fig. 776).
The trochlear nerve, the smallest of the cranial nerves, supplies the Obliquus
superior oculi.
It arises from a nucleus situated in the
floor of the cerebral aqueduct, opposite
the upper part of the inferior colliculus.
From its origin it runs downward through
the tegmentum, and then turns backward
into the upper part of the anterior medul-
lary velum. Here it decussates with its
fellow of the opposite side and emerges
from the surface of the velum at the side
of the frenulum veli, immediately behind
the inferior -colliculus.
The nerve is directed across the super-
ior cerebellar peduncle, and then winds
forward around the cerebral peduncle,
immediately above the pons, pierces the
dura mater in the free border of the ten-
torium cerebelli, just behind, and lateral
to, the posterior clinoid process, and
passes forward in the lateral wall of the
cavernous sinus, between the oculomotor
nerve and the ophthalmic division of the
trigeminal. It crosses the oculomotor
nerve, and enters the orbit through the
superior orbital fissure. It now becomes
the highest of all the nerves, and lies
medial to the frontal nerve. In the orbit
it passes medialward, above the origin of
the Levator palpebrte superioris, and
finally enters the orbital surface of the
Obliquus superior.
In the lateral wall of the cavernous sinus the trochlear nerve forms communica-
tions with the ophthalmic division of the trigeminal and with the cavernous plexus
Fig.
Motor roo
Sensory root
776. — Nerve3 of the orbit.
Recurrent
filament to
dura moier
Seen from above.
886 NEUROLOGY
of the sympathetic. In the superior orbital fissure it occasionally gives off a
branch to the lacrimal nerve. It gives off a recurrent branch which passes back-
ward between the layers of the tentorium cerebelli and divides into two or three
filaments which may be traced as far as the wall of the transverse sinus.
THE TRIGEMINAL NERVE (N. TRIGEMINUS; FIFTH OR TRIFACIAL
NERVE).
The trigeminal nerve is the largest cranial nerve and is the great sensory nerve
of the head and face, and the motor nerve of the muscles of mastication.
It emerges from the side of the pons, near its upper border, by a small motor
and a large sensory root — the former being situated in front of and medial to the
latter.
Motor Root. — The fibers of the motor root arise from two nuclei, a superior and
an inferior. The superior nucleus consists of a strand of cells occupying the whole
length of the lateral portion of the gray substance of the cerebral aqueduct. The
inferior or chief nucleus is situated in the upper part of the pons, close to its dorsal
surface, and along the line of the lateral margin of the rhomboid fossa. The fibers
from the superior nucleus constitute the mesencephalic root : they descend through
the mid-brain, and, entering the pons, join with the fibers from the lower
nucleus, and the motor root, thus formed, passes forward through the pons to its
point of emergence. It is uncertain whether the mesencephalic root is motor or
sensory.
Sensory Root. — The fibers of the sensory root arise from the cells of the semilunar
ganglion which lies in a cavity of the dura mater near the apex of the petrous part
of the temporal bone. They pass backward below the superior petrosal sinus
and tentorium cerebelli, and, entering the pons, divide into upper and lower roots.
The upper root ends partly in a nucleus which is situated in the pons lateral to the
lower motor nucleus, and partlj^ in the locus ca^ruleus; the lower root descends
through the pons and medulla oblongata, and ends in the upper part of the sub-
stantia gelatinosa of Rolando. This lower root is sometimes named the spinal
root of the nerve. Medullation of the fibers of the sensory root begins about the
fifth month of fetal life, but the whole of its fibers are not medullatied until the
third month after birth.
The Semilunar Ganglion {ganglion semihtnare [Gasseri]; Gasserian ganglion) occu-
pies a cavity {cavum Meckelii) in the dura mater covering the trigeminal impression
near the apex of the petrous part of the temporal bone. It is somewhat crescentic in
shape, with its convexity directed forward : medially, it is in relation with the inter-
nal carotid artery and the posterior part of the cavernous sinus. The motor root
runs in front of and medial to the sensory root, and passes beneath the ganglion;
it leaves the skull through the foramen ovale, and, immediately below this
foramen, joins the mandibular nerve. The greater superficial petrosal nerve lies
also underneath the ganglion.
The ganglion receives, on its medial side, filaments from the carotid plexus
of th^ sympathetic. It give oft' minute branches to the tentorium cerebelli, and to
the dura mater in the middle fossa of the cranium. From its convex border, which
is directed forward and lateralward, three large nerves proceed, viz., the ophthalmic,
maxillary, and mandibular. The ophthalmic and maxillary consist exclusively
of sensory fibers; the mandibular is joined outside the cranium by the motor root.
Associated with the three divisions of the trigeminal nerve are four small ganglia.
The ciliary ganglion is connected with the ophthalmic nerve; the sphenopalatine
ganglion with the maxillary nerve; and the otic and submaxillary ganglia with the
mandibular nerve. All four receive sensory filaments from the trigeminal, and
THE TRIGEMINAL NERVE
887
motor and sympathetic filaments from various sources; these filaments are called
the roots of the ganglia.
The Ophthalmic Nerve {n. ophthalmicus) (Figs. 776, 777), or first division of the
trigeminal, is a sensory nerve. It supplies branches to the cornea, ciliary body,
and iris; to the lacrimal gland and conjunctiva; to the part of the mucous membrane
of the nasal cavity; and to the skin of the eyelids, eyebrow, forehead, and nose.
It is the smallest of the three divisions of the trigeminal, and arises from the upper
part of the semilunar ganglion as a short, flattened band, about 2.5 cm. long,
which passes forward along the lateral wall of the cavernous sinus, below the
oculomotor and trochlear nerves; just before entering the orbit, through the supe-
rior orbital fissure, it divides into three branches, lacrimal, frontal, and nasociliary.
The ophthalmic nerve is joined by filaments from the cavernous plexus of the
sympathetic, and communicates with the oculomotor, trochlear, and abducent
nerves; it gives oft' a recurrent filament which passes between the layers of the
tentorium.
Internal carotid artery
and carotid plexus
Upper division of
oc ulomolor nerve
Sensory
root
Motor root
Fig. 777. — Nerves of the orl)it, aud tlie ciliary ganglion. Side view.
The Lacrimal Nerve (w. lacrimalis) is the smallest of the three branches of the
ophthalmic. It sometimes receives a filament from the trochlear nerve, but this
is possibly derived from the branch which goes from the ophthalmic to the troch-
lear nerve. It passes forward in a separate tube of dura mater, and enters the orbit
through the narrowest part of the superior orbital fissure. In the orbit it runs
along the upper border of the Rectus lateralis, with the lacrimal artery, and com-
municates with the zygomatic branch of the maxillary nerve. It enters the lacrimal
gland and gives off several filaments, which supply the gland and the conjunctiva.
Finally it pierces the orbital septum, and ends in the skin of the upper eyelid,
joining with filaments of the facial nerve. The lacrimal nerve is occasionally
absent, and its place is then taken by the zygomaticotemporal branch of the max-
illary. Sometimes the latter branch is absent, and a continuation of the lacrimal
is substituted for it.
The Frontal Nerve (?i. frontalis) is the largest branch of the ophthalmic, and may
be regarded, both from its size and direction, as the continuation of the nerve.
It enters the orbit through the superior orbital fissure, and runs forward between
the Levator palpebnie superioris and the periosteum. Midway between the apex
and base of the orbit it divides into two branches, supratrochlear and supraorbital.
888 NEUROLOGY
The supratrochlear nerve {n. supratrochlearis) , the smaller of the two, passes
above the pulley of the Obliquus superior, and gives oft* a descending filament, to
join the infratrochlear branch of the nasociliary nerve. It then escapes from the
orbit between the pulley of the Obliquus superior and the supraorbital foramen,
curves up on to the forehead close to the bone, ascends beneath the Corrugator
and Frontalis, and dividing into branches which pierce these muscles, it supplies
the skin of the lower part of the forehead close to the middle line and sends
filaments to the conjunctiva and skin of the upper eyelid.
The supraorbital nerve {n. siipraorhitalis) passes through the supraorbital foramen,
and gives off, in this situation, palpebral filaments to the upper eyelid. It then
ascends upon the forehead, and ends in two branches, a medial and a lateral,
which supply the integument of the scalp, reaching nearly as far back as the lamb-
doidal suture; they are at first situated beneath the Frontalis, the medial branch
perforating the muscle, the lateral branch the galea aponeurotica. Both branches
supply small twigs to the pericranium.
The Nasociliary Nerve {n. nasociliaris; 7iasal nerve) is intermediate in size between
the frontal and lacrimal, and is more deeply placed. It enters the orbit between
the two heads of the Rectus lateralis, and between the superior and inferior rami
of the oculomotor nerve. It passes across the optic nerve and runs obliquely
beneath the Rectus superior and Obliquus superior, to the medial wall of the orbital
cavity. Here it passes through the anterior ethmoidal foramen, and, entering
the cavity of the cranium, traverses a shallow groove on the lateral margin of the
front part of the cribriform plate of the ethmoid bone, and runs down, through
a slit at the side of the crista galli, into the nasal cavity. It supplies internal
nasal branches to the mucous membrane of the front part of the septum and lateral
wall of the nasal cavity. Finally, it emerges, as the external nasal branch, between
the lower border of the nasal bone and the lateral nasal cartilage, and, passing
down beneath the Xasalis muscle, supplies the skin of the ala and apex of the nose.
The nasociliary nerve gives ofi' the following branches, viz. : the long root of the
ciliary ganglion, the long ciliary, and the ethmoidal nerves.
The long root of the ciliary ganglion (radix longa ganglii ciliaris) usually arises
from the nasociliary between the two heads of the Rectus lateralis. It passes
forward on the lateral side of the optic nerve, and enters the postero-superior angle
of the ciliary ganglion; it is sometimes joined by a filament from the cavernous
plexus of the sympathetic, or from the superior ramus of the trochlear ner.ve.
The long ciliary nerves {mi. ciliares longi), two or three in number, are given off
from the nasociliary, as it crosses the optic nerve. They accompany the short
ciliary nerves from the ciliary ganglion, pierce the posterior part of the sclera,
and running forward between it and the choroid, are distributed to the iris and
cornea. The long ciliary nerves are supposed to contain s\Tapathetic fibers from
the superior cervical ganglion to the Dilator pupilla? muscle.
The infratrochlear nerve {n. infratrochlearis) is given off from the nasociliary
just before it enters the anterior ethmoidal foramen. It runs forward along the
upper border of the Rectus medialis, and is joined, near the pulley of the Obliquus
superior, by a filament from the supratrochlear nerve. It then passes to the
medial angle of the eye, and supplies the skin of the eyelids and side of the nose,
the conjunctiva, lacrimal sac, and caruncula lacrimalis.
The ethmoidal branches (nn. ethmoidales) supply the ethmoidal cells; the posterior
branch leaves the orbital cavity through the posterior ethmoidal foramen and gives
some filaments to the sphenoidal sinus.
The Ciliary Ganglion {ophthalmic or leniieidar ganglion) (Figs. 775, 777). — The
ciliary ganglion is a small, sympathetic ganglion, of a reddish-gray color, and about
the size of a pin's head; it is situated at the back part of the orbit, in some loose
fat between the optic nerve and the Rectus lateralis muscle, lying generally on the
lateral side of the ophthalmic artery.
THE TRIGEMINAL NERVE 889
Its roots are three in number, and enter its posterior border. One, the long
or sensory root, is derived from the nasocihary nerve, and joins its postero-superior
angle. The second, the short or motor root, is a thick nerve (occasionally divided
into two parts) derived from the branch of the oculomotor nerve to the Obliquus
inferior, and connected with the postero-inferior angle of the ganglion. The motor
root is supposed to contain sympathetic efferent hbers (preganglionic fibers) from
the nucleus of the third nerve in the mid-brain to the ciliary ganglion where they
form s>7iapses with neurons whose fibers (postganglionic) pass to the Ciliary muscle
and to wSphincter muscle of the pupil. The third, the sympathetic root, is a slender
filament from the cavernous plexus of the sympathetic; it is frequently blended
with the long root. According to Tiedemann, the ciliary ganglion receives a twig
of communication from the sphenopalatine ganglion.
Its branches are the short ciliary nerves. These are delicate filaments, from six
to ten in number, which arise from the forepart of the ganglion in two bundles
connected with its superior and inferior angles; the lower bundle is the larger.
They run forward with the ciliary arteries in a wavy course, one set above and the
other below the optic nerve, and are accompanied by the long ciliary nerves from
the nasociliary. They pierce the sclera at the back part of the bulb of the eye, pass
forward in delicate grooves on the inner surface of the sclera, and are distributed
to the Ciliaris muscle, iris, and cornea. Tiedemann has described a small branch
as penetrating the optic nerve with the arteria centralis retinae.
The Maxillary Nerve (n. maxillaris; superior maxillary nerve) (Fig. 778), or
second division of the trigeminal, is a sensory nerve. It is intermediate, both in
position and size, between the ophthalmic and mandibular. It begins at the middle
of the semilunar ganglion as a flattened plexiform band, and, passing horizontally
forward, it leaves the skull through the foramen rotundum, where it becomes more
cylindrical in form, and firmer in texture. It then crosses the pterygopalatine
fossa, inclines lateralward on the back of the maxilla, and enters the orbit through
the inferior orbital fissure; it traverses the infraorbital groove and canal in the
floor of the orbit, and appears upon the face at the infraorbital foramen. ^ At
its termination, the nerve lies beneath the Quadratus labii superioris, and divides
into a leash of branches which spread out upon the side of the nose, the lower
eyelid, and the upper lip, joining with filaments of the facial nerve.
Branches. — Its branches may be divided into four groups, according as they are
given off in the cranium, in the pterygopalatine fossa, in the infraorbital canal, or
on the face.
In the Cranium .... Middle meningeal,
{Zygomatic.
Sphenopalatine.
Posterior superior alveolar.
^ , -r e 1-1^1 1 Anterior superior alveolar.
In the Infraorbital Canal . . j Middle superior alveolar.
[ Inferior palpebral.
On the Face \ External nasal.
[Superior labial.
The Middle Meningeal Nerve (n. meningeus medius; meningeal or dural branch) is
given off from the maxillary nerve directly after its origin from the semilunar
ganglion; it accompanies the middle meningeal artery and supplies the dura mater.
The Zygomatic Nerve (n. zygomaticus; temporomalar nerve; orbital nerve) arises
in the pterygopalatine fossa, enters the orbit by the inferior orbital fissure,
and divides at the back of that cavity into two branches, zygomaticotemporal and
zygomaticofacial.
» After it enters the infraorbital canal, the nerve is frequently called the infToorbital.
890
NEUROLOGY
The zygomaticotemporal branch {ramus zygomaticotemporalis; temporal branch)
runs along the lateral wall of the orbit in a groove in the zygomatic bone, receives
a branch of communication from the lacrimal, and, passing through a foramen
in the zygomatic bone, enters the temporal fossa. It ascends between the bone,
and substance of the Temporalis muscle, pierces the temporal fascia about 2.5 cm.
above the zygomatic arch, and is distributed to the skin of the side of the fore-
head, and communicates with the facial nerve and with the auriculotemporal
branch of the mandibular nerve. As it pierces the temporal fascia, it gives off a
slender twig, which runs between the two layers of the fascia to the lateral angle
of the orbit.
Sensory root
Motor root
AuricvlotemporaL
nerve
FiQ. 778. — Distribution of tlie maxillarj' and mandibular nerves, and the submaxillary ganglion.
The zygomaticofacial branch {ramus zygomaiicofacialis; malar branch) passes
along the infero-lateral angle of the orbit, emerges upon the face through a foramen
in the zygomatic bone, and, perforating the Orbicularis oculi, supplies the skin on
the prominence of the cheek. It joins with the facial nerve and with the inferior
palpebral branches of the maxillary.
The Sphenopalatine Branches {mi. sphenopalatini), two in number, descend to the
sphenopalatine ganglion.
The Posterior Superior Alveolar Branches [rami alveolares superiores posteriores;
posterior superior dental branches) arise from the trunk of the nerve just before
it enters the infraorbital groove; they are generally two in number, but sometimes
arise by a single trunk. They descend on the tuberosity of the maxilla and give off
several twigs to the gums and neighboring parts of the mucous membrane of the
cheek. They then enter the posterior alveolar canals on the infratemporal surface
THE TRIGEMINAL NERVE
891
of the maxilla, and, passing from behind forward in the substance of the bone,
communicate with the middle superior alveolar nerve, and give off branches to the
lining membrane of the maxillary sinus and three twigs to each molar tooth; these
twigs enter the foramina at the apices of the roots of the teeth.
The Middle Superior Alveolar Branch {ramus alveolaris superior medius; middle
superior denial branch), is given off from the nerve in the posterior part of the infra-
orbital canal, and runs downward and forward in a canal in the lateral wall of the
maxillary sinus to supply the two premolar teeth. It forms a superior dental plexus
with the anterior and posterior superior alveolar branches.
The Anterior Superior Alveolar Branch {ramus alveolaris superior anteriores; ante-
rior superior ^ denial branch), of considerable size, is given off from the nerve just
before its exit from the infraorbital foramen; it descends in a canal in the anterior
wall of the maxillary sinus, and divides into branches which supply the incisor
and canine teeth. It communicates with the middle superior alveolar branch,
and gives off a nasal branch, which passes through a minute canal in the lateral wall
of the inferior meatus, and supplies the mucous membrane of the anterior part of
the inferior meatus and the floor of the nasal cavity, communicating with the nasal
branches from the sphenopalatine ganglion.
POSTERIOR
DENTAL
ORBITAL
BRANCH CUT
SPHENOPALATINE
• TYMPANIC
SUPERIOR CERVICAL
GANGLION OF THE
SYMPATHETIC
Fig. 779. — Alveolar branches of superior maxillary nerve and sphenopalatine ganglion. (Testut )
The Inferior Palpebral Branches {rami palpebrals inferiores; palpebral branches)
ascend behind the Orbicularis oculi. They supply the skin and conjunctiva of the
lower eyelid, joining at the lateral angle of the orbit with the facial and zygomatico-
facial nerves.
The External Nasal Branches {rami nasales externi) supply the skin of the side
of the nose and of the septum mobile nasi, and join with the terminal twigs of the
nasociliary nerve.
The Superior Labial Branches {rami labiales superior es; labial branches), the largest
and most numerous, descend behind the Quadratus labii superioris, and are dis-
tributed to the skin of the upper lip, the mucous membrane of the mouth, and labial
glands. They are joined, immediately beneath the orbit, by filaments from the
facial nerve, forming with them the infraorbital plexus.
Sphenopalatine Ganglion {ganglion of Meckel) (Fig. 780). — ^The sphenopalatine
ganglion, the largest of the s^inpathetic ganglia associated with the branches of the
trigeminal nerve, is deeply placed in the pterygopalatine fossa, close to the spheno-
892
NEUROLOGY
palatine foramen. It is triangular or heart-shaped, of a reddish-gra}^ color, and is
situated just below the maxillary nerve as it crosses the fossa. It receives a sensory,
a motor, and a sympathetic root.
Its sensory root is derived from two sphenopalatine branches of the maxillary
nerve; their fibers, for the most part, pass directly into the palatine nerves; a few,
however, enter the ganglion, constituting its sensory root. Its motor root is probably
derived from the nervus intermedins through the greater superficial petrosal nerve
and is supposed to consist in part of sympathetic efferent (preganglionic) fibers
from the medulla. In the sphenopalatine ganglion they form synapses with neurons
whose postganglionic axons, vasodilator and secretory fibers, are distributed with
the deep branches of the trigeminal to the mucous membrane of the nose, soft
palate, tonsils, uvula, roof of the mouth, upper lip and gums, and to the upper part
of the phar\aix. Its sympathetic root is derived from the carotid plexus through the
deep petrosal nerve. These two nerves join to form the nerve of the pterygoid
canal before their entrance into the ganglion.
Terminal
nasopalat;
nerve
Fig. 780. — The sphenopalatine ganglion and its branches. i
The greater superficial petrosal nerve (??. 'petrosiis suyerficialis major; large super-
ficial petrosal nerve) is given oft' from the genicular ganglion of the facial nerve; it
passes through the hiatus of the facial canal, enters the cranial cavity, and runs
forward beneath the dura mater in a groove on the anterior surface of the petrous
portion of the temporal bone. It then enters the cartilaginous substance which
fills the foramen lacerum, and joining with the deep petrosal branch forms the
nerve of the pterygoid canal.
The deep petrosal nerve {n. peirosus profundus; large deep petrosal nerve) is given
off from the carotid plexus, and runs through the carotid canal lateral to the internal
carotid artery. It then enters the cartilaginous substance which fills the foramen
lacerum, and joins with the greater superficial petrosal nerve to form the nerve
of the pterygoid canal.
The nerve of the pterygoid canal (?i. canalis pterygoidei [Vidii]; Vidian nerve).
THE TRIGEMINAL NERVE 893
formed by the junction of the two preceding nerves in the cartilaginous substance
which fills the foramen lacerum, passes forward, through the pterygoid canal, with
the corresponding artery, and is joined by a small ascending sphenoidal branch
from the otic ganglion. Finally, it enters the pterygopalatine fossa, and joins
the posterior angle of the sphenopalatine ganglion.
Branches of Distribution. — These are divisible into four groups, viz., orbital,
palatine, posterior superior nasal, and pharsmgeal.
The orbital branches {rami orhitales; ascending branches) are two or three delicate
filaments, which enter the orbit by the inferior orbital fissure, and supply the peri-
osteum. According to Luschka, some filaments pass through foramina in the fronto-
ethmoidal suture to supply the mucous membrane of the posterior ethmoidal and
sphenoidal sinuses.
The palatine nerves (wn. 'palatini; descending branches) are distributed to the roof
of the mouth, soft palate, tonsil, and lining membrane of the nasal cavity. Most
of their fibers are derived from the sphenopalatine branches of the maxillary nerve.
They are three in number : anterior, middle, and posterior.
The anterior palatine nerve (n. jmlatinus anterior) descends through the pterygo-
palatine canal, emerges upon the hard palate through the greater palatine foramen,
and passes forward in a groove in the hard palate, nearly as far as the incisor teeth.
It supplies the gums, the mucous membrane and glands of the hard palate, and
communicates in front with the terminal filaments of the nasopalatine nerve.
While in the pterygopalatine canal, it gives off posterior inferior nasal branches,
which enter the nasal cavity through openings in the palatine bone, and ramify
over the inferior nasal concha and middle and inferior meatuses; at its exit from
the canal, a palatine branch is distributed to both surfaces of the soft palate.
The middle palatine nerve {n. palatiyius medius) emerges through one of the minor
palatine canals and distributes branches to the uvula, tonsil, and soft palate. It is
occasionally wanting.
The posterior palatine nerve {n. palatinus posterior) descends through the pterygo-
palatine canal, and emerges by a separate opening behind the greater palatine
foramen; it supplies the soft palate, tonsil, and uvula. The middle and posterior
palatine join with the tonsillar branches of the glossopharyngeal to form a plexus
(circulus tonsillaris) around the tonsil.
The posterior superior nasal branches {rami nasales posteriores superiores) are dis-
tributed to the septum and lateral wall of the nasal fossa. They enter the posterior
part of the nasal cavity by the sphenopalatine foramen and supply the mucous
membrane covering the superior and middle nasal conchae, the lining of the poste-
rior ethmoidal cells, and the posterior part of the septum. One branch, longer
and larger than the others, is named the nasopalatine nerve. It enters the nasal
cavity through the sphenopalatine foramen, passes across the roof of the nasal
cavity below the orifice of the sphenoidal sinus to reach the septum, and then runs
obliquely downward and forward between the periosteum and mucous membrane
of the lower part of the septum. It descends to the roof of the mouth through the
incisive canal and communicates with the corresponding nerve of the opposite
side and with the anterior palatine nerve. It furnishes a few filaments to the
mucous membrane of the nasal septum.
The pharyngeal nerve {pterygopalatine nerve) is a small branch arising from the
posterior part of the ganglion. It passes through the pharyngeal canal with the
pharyngeal branch of the internal maxillary artery, and is distributed to the mucous
membrane of the nasal part of the pharynx, behind the auditory tube.
The mandibular nerve {n. mandibularis; inferior maxillary nerve) (Figs. 77S,
781) supplies the teeth and gums of the mandible, the skin of the temporal region,
the auricula, the lower lip, the lower part of the face, and the muscles of mastica-
tion; it also supplies the mucous membrane of the anterior two-thirds of the tongue.
894
NEUROLOGY
It is the largest of the three divisions of the fifth, and is made up of two roots: a
large, sensory root proceeding from the inferior angle of the semilunar ganglion,
and a small motor root (the motor part of the trigeminal), which passes beneath the
ganglion, and unites with the sensory root, just after its exit through the foramen
ovale. Immediately beneath the base of the skull, the nerve gives off from its
medial side a recurrent branch (nervus spinosus) and the nerve to the Pterygoideus
internus, and then divides into two trunks, an anterior and a posterior.
The NervTis Spinosus {recurrent or meningeal branch) enters the skull through the
foramen spinosum with the middle meningeal artery. It divides into two branches,
anterior and posterior, which accompany the main divisions of the artery and
supply the dura mater; the posterior branch also supplies the mucous lining of
the mastoid cells; the anterior communicates with the meningeal branch of the
maxillary nerve.
ANTERIOR
AURICULAR
BRANCHES TO
MEATUS
PAROTID
BRANCHES
COMMUNICATING
TO FACIAL
POSTERIOR TEMPORAL
ZYGOMATICOFACIAL
TEMPORAL BRANCH
OF BUCCAL
INFRAORBITAL
ARTICULAR
BUCCINATOR
INFERIOR
ALVEOLAR
MYLOHYOID LINGUAL
Fig. 781. — Mandibular division of the trifacial nerve. (Testut.)
The Internal Pterygoid Nerve {n. pterygoideus internus). — The nerve to the Ptery-
goideus internus is a slender branch, which enters the deep surface of the muscle;
•it gives off one or two filaments to the otic ganglion.
The anterior and smaller division of the mandibular nerve receives nearly the
whole of the fibers of the motor root of the nerve, and supplies the muscles of
mastication and the skin and mucous membrane of the cheek. Its branches are
the masseteric, deep temporal, buccinator, and external pterygoid.
The Masseteric Nerve (??. massctericus) passes lateralward, above the Pterygoideus
externus, in front of the temporomandibular articulation, and behind the tendon
of the Temporalis; it crosses the mandibular notch with the masseteric artery,
to the deep surface of the Masseter, in which it ramifies nearly as far as its anterior
border. It gives a filament to the temporomandibular joint.
I
THE TRIGEMINAL NERVE 895
The Deep Temporal Nerves {nn. temporales profundi) are two in number, anterior
and posterior. They pass above the upper border of the Pterygoideus externus
and enter the deep surface of the Temporalis. The posterior branch, of small size,
is placed at the back of the temporal fossa, and sometimes arises in common with
the masseteric nerve. The anterior branch is frequently given oft' from the buccina-
tor nerve, and then turns upward over the upper head of the Pterygoideus externus.
Frequently a third or intermediate branch is present.
The Buccinator Nerve (w. buccinatorvs; long buccal nerve) passes forward between
the two heads of the Pterygoideus externus, and downward beneath or through
the lower part of the Temporalis; it emerges from under the anterior border of the
Masseter, ramifies on the surface of the Buccinator, and unites with the buccal
branches of the facial nerve. It supplies a branch to the Pterygoideus externus
during its passage through that muscle, and may give off the anterior deep temporal
nerve. The buccinator nerve supplies the skin over the Buccinator, and the mucous
membrane lining its inner surface.
External Pterygoid Nerve (n. pterygoideus externum). — The nerve to the Ptery-
goideus externus frequently arises in conjunction with the buccinator nerve,
but it may be given oft' separately from the anterior division of the mandibular
nerve. It enters the deep surface of the muscle.
The posterior and larger division of the mandibular nerve is for the most part
sensory, but receives a few filaments from the motor root. It divides into auriculo-
temporal, lingual, and inferior alveolar nerves.
The Auriculotemporal Nerve {n. auriculotemporalis) generally arises by two roots,
between which the middle meningeal artery ascends. It runs backward beneath
the Pterygoideus externus to the medial side of the neck of the mandible. It then
turns upward with the superficial temporal artery, between the auricula and con-
dyle of the mandible, under cover of the parotid gland; escaping from beneath
the gland, it ascends over the zygomatic arch, and divides into superficial temporal
branches.
The branches of communication of the auriculotemporal nerve are with the facial
nerve and with the otic ganglion. The branches to the facial, usually two in number,
pass forward from behind the neck of the mandible and join the facial nerve at
the posterior border of the Masseter. The filaments to the otic ganglion are derived
from the roots of the auriculotemporal nerve close to their origin.
Its branches of distribution are:
Anterior auricular. Articular.
Branches to the external acoustic meatus. Parotid.
Superficial temporal.
The anterior auricular branches (wn. auriculares anteriores) are usually two in
number; they supply the front of the upper part of the auricula, being distributed
principally to the skin covering the front of the helix and tragus.
The branches to the external acoustic meatus {n. meatus auditor ii externi) , two in
number, enter the meatus between its bony and cartilaginous portions and supply
the skin lining it; the upper one sends a filament to the tympanic membrane.
The articular branches consist of one or two twigs which enter the posterior part
of the temporomandibular joint.
The parotid branches {rami parotidei) supply the parotid gland.
The superficial temporal branches (rami teinporales superfidales) accompany the
superficial temporal artery to the vertex of the skull; they supply the skin of the
temporal region and communicate with the facial and zygomaticotemporal nerves.
The Lingual Nerve {n. Ungualis) supplies the mucous membrane of the anterior
two-thirds of the tongue. It lies at first beneath the Pterygoideus externus, medial
to and in front of the inferior alveolar nerve, and is occasionally joined to this
896
NEUROLOGY
nerve by a branch which may cross the internal maxillary artery. The chorda
tympani also joins it at an acute angle in this situation. The nerve then passes
between the Pterygoideus internus and the ramus of the mandible, and crosses
obliquely to the side of the tongue over the Constrictor pharyngis superior and
Styloglossus, and then between the Hyoglossus and deep part of the submaxillary
gland; it finally runs across the duct of the submaxillary gland, and along the tongue
to its tip, lying immediately beneath the mucous membrane.
Its branches of communication are with the facial (through the chorda tympani),
the inferior alveolar and hypoglossal nerves, and the submaxillary ganglion. The
branches to the submaxillary ganglion are two or three in number; those connected
with the hypoglossal nerve form a plexus at the anterior margin of the Hyoglossus.
SMALL PETROE
OTIC GANGLION
BRANCH TO TEN
SOH PALATI
NERVE TO IN
TERNAL PTERV-
aoiD
BRANCH FROM
QANQLION TO
SUBLINGUAL
QLANO
NCH TO TEN-
SOR TYMPANI
BRANCH TO AURIC-
ULO-TEMPORAL
RANCH TO TEN-
SOR PALATI
CHORDA TYMPANI
MIDDLE MENINGEAL
ART. WITH SYMPA-
THETIC PLEXUS
AURICULO-TEM-
PORAL
MALL PETROSAL
RANCH TO TEN-
SOR TYMPANI
TIC GANGLION
TO CHOR-
TYMPANI
LOOP BETWEEN
LINGUAL AND
HYPOGLOSSAL
SYMPATHETIC
ROOT OF
GANGLION
SUBMAXILLARY
GANGLION
NERVE TO
TtNSOR PALATI
Fig. 782. — Mandibular division of trifacial nerve, seen 'rom the middle line.
the otic ganglion. (Testut.)
The small figure is an enlarged view of
Its branches of distribution supply the sublingual gland, the mucous membrane
of the mouth, the gums, and the mucous membrane of the anterior two-thirds of
the tongue; the terminal filaments communicate, at the tip of the tongue, with
the hypoglossal nerve.
The Inferior Alveolar Nerve (n. alveolarw inferior; inferior dejiial nerve) (Fig. 782) is
the largest branch of the mandibular nerve. It descends with the inferior alveolar
artery, at first beneath the Pterygoideus externus, and then between the spheno-
mandibular ligament and the ramus of the mandible to the mandibular foramen.
It then passes forward in the mandibular canal, beneath the teeth, as far as the
mental foramen, where it divides into two terminal branches, incisive and mental.
The branches of the inferior alveolar nerve are the mylohyoid, dental, incisive,
and mental.
The mylohyoid nerve {n. mylohyoideu's) is derived from the inferior alveolar just
THE TRIGEMINAL NERVE
897
before it enters the mandibular foramen. It descends in a groove on the deep
surface of the ramus of the mandible, and reaching the undet surface of the
Mylohyoideus supplies this muscle and the anterior bell}' of the Digastricus.
The dental branches supply the molar and premolar teeth. They correspond
in number to the roots of those teeth; each nerve entering the orifice at the point
of the root, and supplying the pulp of the tooth; above the alveolar nerve they form
an inferior dental plexus.
The incisive branch is continued onward within the bone, and supplies the canine
and incisor teeth.
The mental nerve (?t. mentalis) emerges at the mental foramen, and divides
beneath the Triangularis muscle into three branches; one descends to the skin of
the chin, and two ascend to the skin and mucous membrane of the lower lip; these
branches communicate freely with the facial nerve.
Two small ganglia, the otic and the submaxillary, are connected with the man-
dibular nerve.
Fig. 783. — The otic ganglion and its branches.
Otic GangUon {ganglion oticum) (Fig. 783). — The otic ganglion is a small, oval-
shaped, flattened ganglion of a reddish-gray color, situated immediately below
the foramen ovale; it lies on the medial surface of the mandibular nerve, and
surrounds the origin of the nerve to the Pterygoideus internus. It is in relation,
laterally, with the trunk of the mandibular nerve at the point where the motor and
sensory roots join; medially, with the cartilaginous part of the auditory tube,
and the origin of the Tensor veli palatini; yosteriorly, with the middle meningeal
artery.
Branches of Communication. — It is connected by two or three short filaments
uith the nerve to the Pterygoideus internus, from which it may obtain a motor,
and possibly a sensory root. It communicates with the glossopLaryngeal and facial
nerves, through the lesser superficial petrosal nerve continued from the tympanic
plexus, and through this nerve it probably receives a root from the glosso-
pharyngeal and a motor root from the facial; its sympathetic root consists of a
filament from the plexus surrounding the middle meningeal artery. The fibers
from the glossopharxTigeal which pass to the otic ganglion in the small superficial
petrosal are supposed to be sympathetic efferent (preganglionic) fibers from the
57
898
NEUROLOGY
dorsal nucleus or inferior salivatory nucleus of the medulla. Fibers (postganglionic)
from the otic ganglion with which these form synapses are supposed to pass with
the auriculotemporal nerve to the parotid gland. A slender filament (sphenoidal)
ascends from it to the nerve of the Pterygoid canal, and a small branch connects
it with the chorda tympani.
Its branches of distribution are: a filament to the Tensor tympani, and one to
the Tensor veli palatini. The former passes backward, lateral to the auditory
tube; the latter arises from the ganglion, near the origin of the nerve to the Ptery-
goideus internus, and is directed forward. The fibers of these nerves are, however,
mainly derived from the nerve to the Pterygoideus internus.
LACRIMAL N
SUPRATROCHLEAR N
SUPRAORBITAL N.
INFRATROCHLEAR N
NASAL NERVE
INFRAORBITAL
NERVE
BUCCAL NERVE
MENTAL NERVE-
TEMPORAL BR.
OF TEMPORO-MALAR
MALAR BR. OF
TEMPORO -MALAR
AURICULO-TEMPORAL
NERVE
Fig. 784. — Sensory areas of the head, showing the general distribution of the three divisions of the fifth nerve.
(Modified from Testut.)
Submaxillary Ganglion {ganglion submaxillare) (Fig. 778).- — The submaxillary
ganglion is of small size and is fusiform in shape. It is situated above the deep
portion of the submaxillary gland, on the hyoglossus, near the posterior border
of the Mylohyoideus, and is connected by filaments with the lower border of the
lingual nerve. It is suspended from the lingual nerve by two filaments which join
the anterior and posterior parts of the ganglion. Through the posterior of these
it receives a branch from the chorda timpani nerve which runs in the sheath of
the lingual; these are sympathetic efferent (preganglionic) fibers from the facial
nucleus or the superior salivatory nucleus of the medulla oblongata that terminate
•in the submaxillary ganglion. The postganglionic fibers pass to the submaxillary
gland, it communicates with the sympathetic by filaments from the sympathetic
plexus around the external maxillary artery.
Its branches of distribution are five or six in number; they arise from the lower
part of the ganglion, and supply the mucous membrane of the mouth and the duct
of the submaxillary gland, some being lost in the submaxillary gland. The branch
of communication from the lingual to the forepart of the ganglion is by some
regarded as a branch of distribution, through which filaments pass from the gan-
glion to the lingual nerve, and by it are conveyed to the sublingual gland and the
tongue.
THE ABDUCENT NERVE
899
Trigeminal Nerve Reflexes. — Pains referred to various branches of the trigeminal nerve are of
very frequent occurrence, and should always lead to a careful examination in order to discover
a local cause. As a general rule the diffusion of pain over the various branches of the nerve is
at first confined to one only of the main divisions, and the search for the causative lesion should
always commence with a thorough examination of all those parts which are supplied by that
division; although in severe cases pain may radiate over the branches of the other main divisions.
The commonest example of this condition is the neuralgia which is so often associated with
dental caries — here, although the tooth itself may not appear to be painful, the most distressing
referred pains may be experienced, and these are at once relieved by treatment directed to the
affected tooth.
Many other examples of trigeminal reflexes could be quoted, but it will be sufficient to mention
the more common ones. Dealing with the ophthalmic nerve, severe supraorbital pain is com-
monly associated with acute glaucoma or with disease of the frontal or ethmoidal air cells. Malig-
nant growths or empyema of the maxillary antrum, or unhealthy conditions about the inferior
conchtE or the septum of the nose, are often found giving rise to "second division" neuralgia,
and should be always looked for in the absence of dental disease in the maxilla.
It is on the mandibular nerve, however, that some of the most striking reflexes are seen. It
is quite common to meet with patients who complain of pain in the ear, in whom there is no sign
of aural disease, and the cause is usually to be found in a carious tooth in the mandible. More-
over, with an ulcer or cancer of the tongue, often the first pain to be experienced is one which
radiates to the ear and temporal fossa, over the distribution of the auriculotemporal nerve.
THE ABDUCENT NERVE (N. ABDUCENS; SIXTH NERVE) (Fig. 777).
Rectus lateralis-
III. nerve
The abducent nerve supplies the Rectus lateralis oculi.
Its fibers arise from a small nucleus situated in the upper part of the rhomboid
fossa, close to the middle line and beneath the coUiculus facialis. They pass down-
ward and forward through the pons,
and emerge in the furrow between the
lower border of the pons and the upper
end of the pyramid of the medulla ob-
longata.
From the nucleus of the sixth nerve,
fibers are said to pass through the medial
longitudinal fasciculus to the oculomotor
nerve of the opposite side, along which
they are carried to the Rectus medialis.
The Rectus lateralis of one eye and the
Rectus medialis of the other may there-
fore be said to receive their nerves from
the same nucleus (Fig. 785).
The nerve pierces the dura mater on
the dorsum sellse of the sphenoid, runs
through a notch in the bone below the
posterior clinoid process, and passes for-
ward through the cavernous sinus, on
the lateral side of the internal carotid
artery. It enters the orbit through the
superior orbital fissure, above the oph-
thalmic vein, from which it is separated
by a lamina of dura mater. It then
passes between the two heads of the
Rectus lateralis, and enters the ocular
surface of that muscle. The abducent
nerve is joined bv several filaments from
the carotid and cavernous plexuses, and by one from the ophthalmic nerve. The
oculomotor, trochlear, ophthalmic, and abducent nerves bear certam relations to each
Nucleus VI.-
VI. nerve
Nucleus III.
Rhomboid fossa
Fig. 78.5. — Figure showing the mode of innervation
of the Recti medialis and lateralis of the eye (after Duval
and Laborde).
900
NEUROLOGY
other in the cavernous sinus, at the superior orbital fissure, and in the cavity of
the orbit, as follows:
In the cavernous sinus (Fig. 786), the oculomotor, trochlear, and ophthalmic
nerves are placed in the lateral wall of the sinus, in the order given, from above
downward. The abducent nerve lies at the lateral side of the internal carotid
artery. ' As these nerves pass forward to the superior orbital fissure, the oculo-
motor and ophthalmic divide into
internal carotid artery bj-^nches, and the abducent nerve
Cavernous smus i xu xi xi x xi •
approaches the others; so that their
relative positions are considerably
changed.
In the superior orbital fissure (Fig.
787), the trochlear nerve and the
frontal and lacrimal divisions of the
ophthalmic lie in this order from
the medial to the lateral side upon
the same plane; they enter the cavity
of the orbit above the muscles. The
remaining nerves enter the orbit be-
tween the two heads of the Rectus
lateralis. The superior division of
the oculomotor is the highest of these; beneath this lies the nasociliary branch
of the ophthalmic; then the inferior division of the oculomotor; and the abducent
lowest of all.
Oculomotor nerve — /
Trochlear nerve-
Ophthalmic nerve
Abducent nerve
Maxillary nerve
Fig. 786. — Oblique section through the right cavernous
sinus.
Frontal nerve
Sup. ramus of oculomotor nerve
Sup. orbital fissure
Lacrimal nerve
Levator pulpebroe
Nasociliary nerve
I Trochlear nerve
Abducent nerve
Inj. ramus of oculomotor Inf. orbital Optic foramen
nerve fissure
FiQ. 787. — Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.
In the orbit, the trochlear, frontal, and lacrimal nerves lie immediately beneath
the periosteum, the trochlear nerve resting on the Obliquus superior, the frontal
on the Levator palpebrje superioris, and the lacrimal on the Rectus lateralis.
The superior division of the oculomotor nerve lies immediately beneath the Rectus
THE FACIAL NERVE
901
superior, while the nasociliary nerve crosses the optic nerve to reach the medial
wall of the orbit. Beneath these is the optic nerve, surrounded in front by the
ciliary nerves, and having the ciliary ganglion on its lateral side, between it and the
Rectus lateralis. Below the optic nerve are the inferior division of the oculomotor,
and the abducent, the latter lying on the medial surface of the Rectus lateralis.
THE FACIAL NERVE fN. FACIALIS; SEVENTH NERVE) (Figs. 788, 790).
The facial nerve consists of a motor and a sensory part, the latter being frequently
described under the name of the nervus intermedius {yars intermedii of Wrisherg)
(Fig. 788). The two parts emerge at the lower border of the pons in the recess
between the olive and the inferior peduncle, the motor part being the more medial,
immediately to the lateral side of the sensory part is the acoustic nerve.
Nucleus Salivatorius
Genu
Efferent division of
X.Intennediua
Nucleus of
Facial JV
Superior Maxillary X.
Vidian N. \
•ficial Petrosa\ [~ f)
Spheno -
palatine
Ganglion
Glossopharyngeal
Nucleus
To Auricular
Branch of I'agus X.
Post
Auricular Br. -"'
Communicating Branch
To Digastric
lo atylo-hyo.
Afferent Haste) fibers
Efferent iexcito-glandular)
fibers to submaxillary and
sublingual ganglia and glands
Fig. 788. — Plan of the facial and intermediate nerves and their communication with other nerves.
The motor part supplies somatic motor fibers to the muscles of the face, scalp,
and auricle, the Buccinator and Platysma, the Stapedius, the Stylohyoideus,
and posterior belly of the Digastricus; it also contains some sympathetic motor
fibers which constitute the vasodilator nerves of the submaxillary and sublingual
glands, and are conveyed through the chorda tympani ner\e. These are pregan-
glionic fibers of the sympathetic system and terminate in the submaxillary ganglion
and small ganglia in the hilus of the submaxillary gland. From these ganglia
postganglionic fibers are conveyed to these glands. The sensory part contiiins
the fibers of taste for the anterior two-thirds of the tongue and a few somatic
902 NEUROLOGY
sensory fibers from the middle ear region. A few splanchnic sensory fibers are also
present.
The motor root arises from a nucleus which lies deeply in the reticular formation
of the lower part of the pons. This nucleus is situated above the nucleus ambiguus,
behind the superior olivary nucleus, and medial to the spinal tract of the trigemi-
nal nerve. From this origin the fibers pursue a curved course in the substance
of the pons. They first pass backward and medialward toward the rhomboid
fossa, and, reaching the posterior end of the nucleus of the abducent nerve, run
upward close to the middle line beneath the colliculus fasciculus. At the anterior
end of the nucleus of the abducent nerve they make a second bend, and run down-
ward and forward through the pons to their point of emergence between the olive
and the inferior peduncle.
The sensory root arises from the genicular ganglion, which is situated on the genic-
ulum of the facial nerve in the facial canal, behind the hiatus of the canal. The cells
of this ganglion are unipolar, and the single process divides in a T-shaped manner
into central and peripheral branches. The central branches leave the trunk of
the facial nerve in the internal acoustic meatus, and form the sensory root; the
peripheral branches are continued into the chorda tympani and greater super-
ficial petrosal nerves. Entering the brain at the lower border of the pons between
the motor root and the acoustic nerve, the fibers of the sensory root pass into the
substance of the medulla oblongata and end 'in the upper part of the terminal
nucleus of the glossopharyngeal nerve and in the fasciculus solitarius.
External s^iperficial petrosal
Branch to join lesser superficial petrosal
Greater superficial petrosal
Genicular ganglion
Facial
Acoustic ' ' ™%t)fc,4?<«'.'y ?■!!
Fig. 789. — The course and connections of the facial nerve in the temporal bone.
From their superficial attachments to the brain, the two roots of the facial nerve
pass lateralward and forward with the acoustic nerve to the internal acoustic
meatus. In the meatus the motor root lies in a groove on the upper and anterior
surface of the acoustic nerve, the sensory root being placed between them.
At the bottom of the meatus, the facial nerve enters the facial canal, which it
traverses to its termination at the stylomastoid foramen. It is at first directed
lateralward between the cochlea and vestibule toward the medial wall of the
tympanic cavity; it then bends suddenly backward and arches downward behind
the tympanic cavity to the stylomastoid foramen. The point where it changes
its direction is named the geniculum ; it presents a reddish gangliform swelling, the
genicular ganglion {ganglion geniculi; geniculate ganglion; nucleus of the sensory root
of the nerve) (Fig. 789). On emerging from the stylomastoid foramen, the facial
nerve runs forward in the substance of the parotid gland, crosses the external
carotid artery, and divides behind the ramus of the mandible into branches, from
which numerous offsets are distributed over the side of the head, face, and upper
part of the neck, supplying the superficial muscles in these regions. The branches
and their offsets unite to form the parotid plexus.
Branches of Communication. — The branches of communication of the facial nerve
may be arranged as follows:
THE FACIAL NERVE
903
In the internal acoustic
meatus .
At the genicular ganglion
In the facial canal .
At its exit from the stylo-
mastoid foramen .
Behind the ear
On the face
In the neck
With the acoustic nerve.
With the sphenopalatine ganglion by the greater
superficial petrosal nerve.
\\ ith the otic ganglion by a branch which joins
the lesser superficial petrosal nerve.
With the sympathetic on the middle meningeal
. artery.
With the auricular branch of the vagus.
With the glossopharyngeal.
With the vagus.
With the great auricular.
With the auriculotemporal.
With the lesser occipital.
With the trigeminal.
With the cutaneous cervical.
In the internal acoustic meatus some minute filaments pass from the facial to
the acoustic nerve.
The greater superficial petrosal nerve {large superficial 'petrosal nerve) arises from
the genicular ganglion, and consists chiefly of sensory branches which are dis-
tributed to the mucous membrane of the soft palate; but it probably contains a few
motor fibers which form the motor root of the sphenopalatine ganglion. It passes
forward through the hiatus of the facial canal, and runs in a sulcus on the anterior
surface of the petrous portion of the temporal bone beneath the semilunar ganglion,
to the foramen lacerum. It receives a twig from the tympanic plexus, and in the
foramen is joined by the deep petrosal, from the sympathetic plexus on the internal
carotid artery, to form the nerve of the pterygoid canal which passes forward
through the pterygoid canal and ends in the sphenopalatine ganglion. The genicular
ganglion is connected with the otic ganglion by a branch which joins the lesser
superficial petrosal nerve, and also with the sympathetic filaments accompanying
the middle meningeal artery. According to Arnold, a twig passes back from the
ganglion to the acoustic nerve. Just before the facial nerve emerges from the
stylomastoid foramen, it generally receives a twig from the auricular branch of
the vagus.
After its exit from the stylomastoid foramen, the facial nerve sends a twig to
the glossopharyngeal, and communicates with the auricular branch of the vagus,
with the great auricular nerve of the cervical plexus, with the auriculotemporal
nerve in the parotid gland, and with the lesser occipital behind the ear; on the face
with the terminal branches of the trigeminal, and in the neck with the cutaneous
cervical nerve.
Branches of Distribution. — The branches of distribution (Fig. 788) cf the facial
nerve may be thus arranged:
With the facial canal
At its exit from the stylo-
mastoid foramen
On the face
1
Nerve to the Stapedius muscle.
Chorda tympani.
Posterior auricular.
Digastric.
Stylohyoid.
Temporal.
Zygomatic.
Buccal.
Mandibular.
Cervical.
904
NEUROLOGY
The Nerve to the Stapedius {n. stapedius; tympanic branch) arises opposite the
pyramidal eminence (page 1042); it passes through a small canal in this eminence
to reach the muscle.
The Chorda Tympani Nerve is given off from the facial as it passes downward
behind the tympanic cavity, about 6 mm. from the stylomastoid foramen. It
runs upward and forward in a canal, and enters the tympanic cavity, through an
aperture (iter chordae posterius) on its posterior wall, close to the medial surface
of the posterior border of the tympanic membrane and on a level with the upper
Termination
of supratrochlear
]f infratroctilear
rf nasociliary
Fig. 790. — The nerves of the scalp, face, and side of neck.
end of the manubrium of the malleus. It traverses the tympanic cavity, between
the fibrous and mucous layers of the tympanic membrane, crosses the manubrium
of the malleus, and emerges from the cavity through a foramen situated at the inner
end of the petrotympanic fissure, and named the iter chordae anterius {canal of
Hnguier). It then descends between the Pterygoideus externus and internus on
the medial surface of the spina angularis of the sphenoid, which it sometimes
grooves, and joins, at an acute angle, the posterior border of the lingual nerve.
It receives a few efferent fibers from the motor root ; these enter the submaxillary
ganglion, and through it are distributed to the submaxillary and sublingual glands;
THE ACOUSTIC NERVE 905
the majority of its fibers are afferent, and are continued onward through the mus-
cular substance of the tongue to the. mucous membrane covering its anterior
two-thirds; they constitute the nerve of taste for this portion of the tongue. Before
uniting with the Hngual nerve the chorda tympani is joined by a small branch from
the otic ganglion.
The Posterior Auricular Nerve {n. auricularis posterior) arises close to the stylo-
mastoid foramen, and runs upward in front of the mastoid process; here it is joined
by a filament from the auricular branch of the vagus, and communicates with the
posterior branch of the great auricular, and with the lesser occipital. As it ascends
between the external acoustic meatus and mastoid process it divides into auricular
and occipital branches. The auricular branch su})plies the Auricularis posterior
and the intrinsic muscles on the cranial surface of the auricula. The occipital
branch, the larger, passes backward along the superior nuchal line of the occipital
bone, and supplies the Occipitalis.
The Digastric Branch (ramus digastricus) arises close to the stylomastoid foramen,
and divides into several filaments, which supply the posterior belly of the Digas-
tricus; one of these filaments joins the glossopharyngeal nerve.
The Stylohyoid Branch (ramus stijlohyoideus) frequently arises in conjunction
with the digastric branch; it is long and slender, and enters the Stylohyoideus about
its middle.
The Temporal Branches (rami temporales) cross the zygomatic arch to the temporal
region, supplying the Auriculares anterior and superior, and joining with the zygo-
maticotemporal branch of the maxillary, and with the auriculotemporal branch
of the mandibular. The more anterior branches supply the Frontalis, the Orbicu-
laris oculi, and the Corrugator, and join the supraorbital and lacrimal branches
of the ophthalmic.
The Zygomatic Branches (rami zygomatici; malar branches) run across the zygo-
matic bone to tiie lateral angle of the orbit, where they supply the Orbicularis oculi,
and join with filaments from the lacrimal nerve and the zygomaticofacial branch
of the maxillary nerve.
The Buccal Branches (rami buccales; infraorbital branches), of larger size than the
rest, pass horizontally forward to be distributed below the orbit and around the
mouth. The superficial branches run beneath the skin and above the superficial
muscles of the face, which they supply: some are distributed to the Procerus,
joining at the medial angle of the orbit with the infratrochlear and nasociliary
branches of the ophthalmic. The deep branches pass beneath the Zygomaticus and
the Quadratus labii superioris, supplying them and forming an infraorbital plexus with
the infraorbital branch of the maxillary nerve. These branches also supply the
small muscles of the nose. The lower deep branches supply the Buccinator and
Orbicularis oris, and join with filaments of the buccinator branch of the mandibular
nerve.
The Mandibular Branch (ramus marginalis mandibulce) passes forward beneath
the Platysma and Triangularis, supplying the muscles of the lower lip and chin,
and communicating with the mental branch of the inferior alveolar nerve.
The Cervical Branch (ramus colli) runs forward beneath the Platysma, and forms
a series of arches across the side of the neck over the suprahyoid region. One
branch descends to join the cervical cutaneous nerve from the cervical plexus;
others supply the Plat\'sma.
THE ACOUSTIC NERVE (EIGHTH NERVE).
The acoustic nerve consists of two distinct sets of fibers which differ in their
peripheral endings, central connections, functions, and time of meduUation. It is
soft in texture and devoid of neurilemma.
906 NEUROLOGY
Cochlear Nerve. — The cochlear nerve or root, the nerve of hearing, arises from
bipolar cells in the spiral ganglion of the cochlea, situated near the inner edge of
the osseous spiral lamina. The peripheral fibers pass to the organ of Corti. The
central ones pass dowii the modiolus and then through the foramina of the tractus
spiralis foraminosus or through the foramen centrale into the lateral or outer end
of the internal auditory meatus. The nerve passes along the internal auditory
meatus with the vestibular nerve and across the subarachnoid space, just above
the flocculus, almost directly medialward toward the inferior peduncle to terminate
in the cochlear nucleus.
The cochlear nerve is placed lateral to the vestibular root. Its fibers end in two
nuclei: one, the accessory nucleus, lies immediately in front of the inferior peduncle;
the other, the tuberculum acusticum, somewhat lateral to it.
The striae meduUares {striae, acusticce) are the axons of the cells of the tuberculum
acusticum. They pass over the inferior peduncle, and across the rhomboid fossa
to the median sulcus. Here they dip into the substance of the pons, to end around
the cells of the superior olivary nuclei of both sides. There are, however, other
fibers, and these are both direct and crossed, which pass into the lateral lemniscus.
The cells of the accessory nucleus give origin to fibers which run transversely in the
pons and constitute the trapezium. Of the trapezoid fibers some end around the
cells of the superior olivary nucleus or of the trapezoid nucleus of the same or
opposite side, while others, crossed or uncrossed, pass directly into the lateral
lemniscus.
If the further connections of the cochlear nerve of one side, say the left, be con-
sidered, it is found that they lie lateral to the main sensory tract, the lemniscus,
and are therefore termed the lateral lemniscus. The fibers comprising the left
lateral lemniscus arise in the superior olivary and trapezoid nuclei of the same or
opposite side, while others are the uninterrupted fibers already alluded to, and these
are either crossed or uncrossed, the former being the axons of the cells of the right
accessory nucleus or of the cells of the right tuberculum acusticum, while the
latter are derived from the cells of the left nuclei. In the upper part of the lateral
lemniscus there is a collection of nerve cells, the nucleus of the lateral lemniscus,
around the cells of which some of the fibers arborize and from the cells of which
axons originate to continue upward the tract of the lateral lemniscus. The ultimate
ending of the left lateral lemniscus is partly in the opposite medial geniculate
body, and partly in the inferior colliculi. From the cells of these bodies new fibers
arise and ascend in the occipital part of the internal capsule to reach the posterior
three-fifths of the left superior temporal gyrus and the transverse temporal gyri.
Vestibular Nerve. — The vestibular nerve or root, the nerve of equilibration,
arises from bipolar cells in the vestibular ganglion, ganglion of Scarpa, which is
situated in the upper part of the outer end of the internal auditory meatus. The
peripheral fibers divide into three branches: the superior branch passes through
the foramina in the area vestibularis superior and ends in the utricle and in the
ampullfe of the superior and lateral semicircular ducts; the fibers of the inferior
branch traverse the foramina in the area vestibularis inferior and end in the saccule;
the posterior branch runs through the foramen singulare and supplies the ampulla
of the posterior semicircular duct.
THE GLOSSOPHARYNGEAL NERVE (N. GLOSSOPHARYNGEUS; NINTH
NERVE) (Figs. 791, 792, 793).
The glossopharyngeal nerve contains both motor and sensory fibers, and is dis-
tributed, as its name implies, to the tongue and pharynx. It is the nerve of ordinary
sensation to the mucous membrane of the pharynx, fauces, and palatine tonsil, and
the nerve of taste to the posterior part of the tongue. It is attached by three or
THE GLOSSOPHARYNGEAL NERVE
907
Auricular
Tympanic
Pharyngeal
four filaments to the upper part of the medulla oblongata, in the groove between
the olive and the inferior peduncle.
The sensory fibers arise from the cells of the superior and petrous ganglia, which
are situated on the trunk of the nerve, and will be presently described. When
traced into the medulla,
some of the sensory fibers,
probably sympathetic af-
ferent, end by arborizing
around the cells of the
upper part of a nucleus
which lies beneath the ala
cinerea in the lower part of
the rhomboid fossa. Many
of the fibers, probably the
taste fibers, contribute to
form a strand, named the
fasciculus solitarius, which
descends in the medulla
oblongata. Associated with
this strand are numerous
nerve cells, and around
these the fibers of the
fasciculus end. The so-
matic sensory fibers, few in
number, are said to join
the spinal tract of the tri-
geminal nerve.
The somatic motor fibers
spring from the cells of the
nucleus ambiguus, which lies some distance from the surface of the rhomboid fossa
in the lateral part of the medulla and is continuous below with the anterior gray
column of the medulla spinalis. From this nucleus the fibers are first directed
backward, and then they bend forward and lateralward to join the fibers of the
sensory root. The nucleus ambiguus gives origin to the motor branches of the
glossopharyngeal and vagus nerves, ^nd to the cranial part of the accessory nerve.
The sympathetic efferent fibers from the nucleus beneath the ala cinerea, the dorsal
nucleus, are probably both preganglionic motor fibers and preganglionic secretory
fibers of the sympathetic system. The secretory fibers pass to the otic ganglion
and from it secondary neurons are distributed to the parotid gland. Some authors
describe these fibers as arising from a distinct nucleus the inferior salivatory
nucleus, which lies near the dorsal nucleus.
From the medulla oblongata, the glossopharyngeal nerve passes lateralward
across the flocculus, and leaves the skull through the central part of the jugular
foramen, in a separate sheath of the dura mater, lateral to and in front of the vagus
and accessory nerves (Fig. 792). In its passage through the jugular foramen,
it grooves the lower border of the petrous part of the temporal bone; and, at its
exit from the skull, passes forward between the internal jugular vein and internal
carotid artery; it descends in front of the latter vessel, and beneath the styloid
process and the muscles connected with it, to the lower border of the Stylo-
pharyngeus. It then curves forward, forming an arch on the side of the neck
and lying upon the Stylopharyngeus and Constrictor pharyngis medius. Thence
it passes under cover of the Hyoglossus, and is finally distributed to the palatine
tonsil, the mucous membrane of the fauces and base of the tongue, and the
mucous glands of the mouth.
Laryngeal
Fia. 791. — Plan of upper portions of glossopharyngeal, vagus, and
accessory nerves.
908
NEUROLOGY
In passing through the jugular foramen, the nerve presents two ganglia, the
superior and the petrous (Fig. 791).
The Superior Ganglion {ganglion swperius; jugular ganglion) is situated in the
upper part of the groove in which the nerve is lodged during its passage through
the jugular foramen. It is very small, and is usually regarded as a detached
portion of the petrous ganglion.
The Petrous Ganglion {ganglion petrosum; inferior ganglion) is larger than the
superior and is situated in a depression in the lower border of the petrous portion
of the temporal bone.
Trochlear verve
Trigeminal nerve
Facial nerve
Acoustic; nerve
Cerebral peduncle
Superior peduncle
Middle peduncle
Inferior peduncle
Olossopharyngeai,
nerve
VagiiS nerre
Accessory nerve |
(cranial part)
Hypoglossal nerve
Accessory nerve
(spiiwlpart) '
Post, roots of first
cervical nerve
Medulla spinalis
Fasciculus cuneatus
Fasciculus gracilis
Dura mater
(laid open,
Fio. 792. — Upper part of medulla spinalis and hind- and mid-braina; posterior aspect, exposed in situ.
Branches of Communication. — The glossopharyngeal nerve communicates with
the vagus, sympathetic, and facial.
The branches to the vagus are two filaments which arise from the petrous gan-
glion, one passing to the auricular branch, and the other to the jugular ganglion,
of the vagus. The petrous ganglion is connected by a filament with the superior
cervical ganglion of the sympathetic. The branch of communication with the facial
perforates the posterior belly of the Digastricus. It arises from the trunk of the
glossopharyngeal below the petrous ganglion, and joins the facial just after the exit
of that nerve from the stylomastoid foramen.
Branches of Distribution. — The branches of distribution of the glossopharyngeal
are: the tjrmpanic, carotid, pharyngeal, muscular, tonsillar, and lingual.
THE GLOSSOPHARYNGEAL NERVE
909
The Tympanic Nerve (n. tympanicus; nerve of Jacobson) arises from the petrous
ganglion, and ascends to the tympanic cavity through a small canal on the
under surface of the i)etrous
Olossopharyngea I
Vagus
Aocessory !
portion of the temporal bone on
the ridge which separates the
carotid canal from the jugular
fossa. In the tympanic cavity
it divides into branches which
form the tympanic plexus and
are contained in grooves upon
the surface of the promontory.
This plexus gives off: (1) the
lesser sujierficial petrosal nerve;
(2) a branch to join the greater
superficial petrosal nerve; and (3)
branches to the tympanic cavity,
all of which will be described in
connection with the anatomy of
the middle ear.
The Carotid Branches {n. car-
oticotympanicus superior and n.
caroticotympanicus inferior) de-
scend along the trunk of the
internal carotid artery as far as
its origin, communicating with
the pharyngeal branch of the
vagus, and with branches of
the sympathetic.
The Pharyngeal Branches {rami
pharyngei) are three or four fila-
ments which unite, opposite the
Constrictor pharyngis medius,-
with the pharyngeal branches of
the vagus and sympathetic, to
form the pharyngeal plexus;
branches from this plexus per-
forate the muscular coat of the
pharynx and supply its muscles
and mucous membrane.
The Muscular Branch (ramus
stylopharyngeus) is distributed
to the Stylopharyngeus.
The Tonsillar Branches (j-ami
ionsillares) supply the palatine
tonsil, forming around it a plexus
from which filaments are dis-
tributed to the soft palate and
fauces, where they communicate
with the palatine nerves.
The Lingual Branches {rami
linguales) are two in number; one
supplies the papilUe vallatfe and the mucous membrane covering the base of the
tongue; the other supplies the mucous membrane and follicular glands of the
posterior part of the tongue, and communicates with the lingual nerve.
Fig. 793.-
-Course and distribution of the glossopharyngeal,
vagus, and accessory nerves.
910 NEUROLOGY
THE VAGUS NERVE (N. VAGUS; TENTH NERVE; PNEUMOGASTRIC
NERVE) (Figs. 791, 792, 793).
The vagus nerve is composed of both motor and sensory fibers, and has a more
extensive course and distribution than any of the other cranial nerves, since it
passes through the neck and thorax to the abdomen.
The vagus is attached by eight or ten filaments to the medulla oblongata in the
groove between the olive and the inferior peduncle, below the glossopharyngeal.
The sensory fibers arise from the cells of the jugular ganglion and ganglion nodosum
of the nerve, and, when traced into the medulla oblongata mostly end by arborizing
around the cells of the inferior part of a nucleus which lies beneath the ala cinerea
in the lower part of the rhomboid fossa. These are the sympathetic afferent fibers.
Some of the sensory fibers of the glossopharyngeal nerve ha\'e been seen to end in
the upper part of this nucleus. A few of the sensory fibers of the vagus, probably
taste fibers, descend in the fasciculus solitarius and end around its cells. The somatic
sensory fibers, few in number, from the posterior part of the external auditory
meatus and the back of the ear, probably join the spinal tract of the trigeminal as
it descends in the medulla. The somatic motor fibers arise from the cells of the
nucleus ambiguus, already referred to in connection with the motor root of the
glossopharyngeal ner\e.
The sympathetic efferent fibers, distributed probably as preganglionic fibers to
the thoracic and abdominal viscera, i. e., as motor fibers to the bronchial tree,
inliibitory fibers to the heart, motor fibers to the esophagus, stomach, small intes-
tine and gall passages, and as secretory fibers to the stomach and pancreas, arise
from the dorsal nucleus of the vagus.
The filaments of the nerve unite, and form a flat cord, which passes beneath
the flocculus to the jugular foramen, through which it leaves the cranium. In
emerging through this opening, the vagus is accompanied by and contained in
the same sheath of dura mater with the accessory nerve, a septum separating
them from the glossopharyngeal which lies in front (Fig. 792). In this situation
the vagus presents a well-marked ganglionic enlargement, which is called the jugular
ganglion {ganglion of the root); to it the accessory nerve is connected by one or
two filaments. After its exit from the jugular foramen the vagus is joined by the
cranial portion of the accessory nerve, and enlarges into a second gangliform swell-
ing, called the ganglion nodosum {ganglion of the trunk) ; through this the fibers of the
cranial portion of the accessory pass without interruption, being principally
distributed to the pharyngeal and superior laryngeal branches of the vagus, but
some of its fibers descend in the trunk of the vagus, to be distributed with the
recurrent nerve and probably also with the cardiac nerves.
The vagus nerve passes vertically down the neck within the carotid sheath,
lying between the internal jugular vein and internal carotid artery as far as the
upper border of the thyroid cartilage, and then between the same vein and the
common carotid artery to the root of the neck. The further course of the nerve
differs on the two sides of the body.
On the right side, the nerve passes across the subclavian artery between it and
the right innominate vein, and descends by the side of the trachea to the back of
the root of the lung, where it spreads out in the posterior pulmonary plexus. From
the lower part of this plexus two cords descend on the esophagus, and divide to
form, with branches from the opposite nerve, the esophageal plexus. Below, these
branches are collected into a single cord, which runs along the back of the esophagus
enters the abdomen, and is distributed to the postero-inferior surface of the stomach,
joining the left side of the celiac plexus, and sending filaments to the lienal plexus.
On the lejt side, the vagus enters the thorax between the left carotid and sub-
clavian arteries, behind the left innominate vein. It crosses the left side of the
THE VAGUS NERVE 911
arch of the aorta, and descends behind the root of the left lung, forming there
the posterior pulmonary plexus. From this it runs along the anterior surface of the
esophagus, where it unites with the nerve of the right side in the esophageal
plexus, and is continued to the stomach, distributing branches over its antero-
superior surface; some of these extend over the fundus, and others along the lesser
curvature. Filaments from these branches enter the lesser omentum, and join the
hepatic plexus.
The Jugular Ganglion {ganglion jugulare; ganglion of the root) is of a grayish
color, spherical in form, about 4 mm. in diameter.
Branches of Communication.— This ganglion is connected by several delicate
filaments to the cranial portion of the accessory nerve; it also communicates by
a twig with the petrous ganglion of the glossopharyngeal, with the facial nerve
by means of its auricular branch, and with the sympathetic by means of an ascend-
ing filament from the superior cervical ganglion.
The Ganglion Nodosum (ganglion of the trunk; inferior ganglion) is cylindrical
in form, of a reddish color, and 2.5 cm. in length. Passing through it is the cranial
portion of the accessory nerve, which blends with the vagus below the ganglion.
Branches of Communication.— This ganglion is connected with the hypoglossal,
the superior cervical ganglion of the sympathetic, and the loop between the first
and second cervical nerves.
Branches of Distribution. — The branches of distribution of the vagus are:
In the Jugular Fossa JAuHculaf'
Pharyngeal.
In the Neck J Superior laryngeal.
In the Thorax
In the Abdomen
^Recurrent.
Superior cardiac.
Inferior cardiac.
Anterior bronchial.
Posterior bronchial.
Esophageal.
Gastric.
Celiac.
Hepatic.
The Meningeal .Branch {ramus meningeus; dural branch) is a recurrent filament
given off frorh the jugular ganglion; it is distributed to the dura mater in the
posterior fossa of the base of the skull.
The Auricular Branch {ramus auricularis; nerve of Arnold) arises from the jugular
ganglion, and is joined soon after its origin by a filament from the petrous ganglion
of the glossopharyngeal; it passes behind the internal jugular vein, and enters the
mastoid canaliculus on the lateral wall of the jugular fossa. Traversing the sub-
stance of the temporal bone, it crosses the facial canal about 4 mm. above the stylo-
mastoid foramen, and here it gives off an ascending branch which joins the facial
nerve. The nerve reaches the surface by passing through the tympanomastoid
fissure between the mastoid process and the tympanic part of the temporal bone,
and divides into two branches: one joins the posterior auricular nerve, the other
is distributed to the skin of the back of the auricula and to the posterior part of
the external acoustic meatus.
The Pharyngeal Branch {ramus jpharyngeus), the principal motor nerve of the
pharynx, arises from the upper part of the ganglion nodosum, and consists prin-
cipally of filaments from the cranial portion of the accessory nerve. It passes
across the internal carotid artery to the upper border of the Constrictor pharyngis
912 NEUROLOGY
medius, where it divides into numerous filaments, which join with branches from
the glossopharyngeal, sympathetic, and external laryngeal to form the pharyngeal
plexus. From the plexus, branches are distributed to the muscles and mucous
membrane of the pharynx and the muscles of the soft palate, except the Tensor
veli palatini. A minute filament descends and joins the hypoglossal nerve as it
winds around the occipital artery.
The Superior Laryngeal Nerve {n. laryrigeus superior) larger than the preceding,
arises from the middle of the ganglion nodosum and in its course receives a branch
from the superior cervical ganglion of the sympathetic. It descends, by the side of
the pharynx, behind the internal carotid artery, and divides into two branches,
external and internal.
The external branch {ramus externus), the smaller, descends on the larynx, beneath
the Sternothyreoideus, to supply the Cricothyreoideus. It gives branches to the
pharyngeal plexus and the Constrictor pharyngis inferior, and communicates with
the superior cardiac nerve, behind the common carotid artery.
The internal branch {ramus internus) descends to the hyothyroid membrane,
pierces it in company with the superior laryngeal artery, and is distributed to the
mucous membrane of the larynx. Of these branches some are distributed to the
epiglottis, the base of the tongue, and the epiglottic glands; others pass backward,
in the ary epiglottic fold, to supply the mucous membrane surrounding the entrance
of the larynx, and that lining the cavity of the larynx as low down as the vocal
folds. A filament descends beneath the mucous membrane on the inner surface
of the thyroid cartilage and joins the recurrent nerve.
The Recurrent Nerve (??. recurrens; inferior or recurrent laryngeal nerve) arises,
on the right side, in front of the subclavian artery; winds from before back-
ward around that vessel, and ascends obliquely to the side of the trachea behind
the common carotid artery, and either in front of or behind the inferior thyroid
artery. On the left side, it arises on the left of the arch of the aorta, and winds
below the aorta at the point where the ligamentum arteriosum is attached, and then
ascends to the side of the trachea. The nerve on either side ascends in the groove
between the trachea and esophagus, passes under the lower border of the Con-
strictor pharyngis inferior, and enters the larynx behind the articulation of the
inferior cornu of the thyroid cartilage with the cricoid; it is distributed to all the
muscles of the larynx, excepting the Cricothyreoideus. It communicates with the
internal branch of the superior laryngeal nerve, and gives off a few filaments to
the mucous membrane of the lower part of the larynx.
As the recurrent nerve hooks around the subclavian artery or aorta, it gives
off several cardiac filaments to the deep part of the cardiac plexus. As it ascends
in the neck it gives off branches, more numerous on the left than on the right side,
to the mucous membrane and muscular coat of the esophagus; branches to the
mucous membrane and muscular fibers of the trachea; and some pharyngeal
filaments to the Constrictor pharyngis inferior.
The Superior Cardiac Branches {rami cardiaci superiores; cervical cardiac branches),
two or three in number, arise from the vagus, at the upper and lower parts of the
neck.
The upper branches are small, and communicate with the cardiac branches
of the sympathetic. They can be traced to the deep part of the cardiac plexus.
The lower branch arises at the root of the neck, just above the first rib. That
from the right vagus passes in front or by the side of the innominate artery, and
proceeds to the deep part of the cardiac plexus; that from the left runs down across
the left side of the arch of the aorta, and joins the superficial part of the cardiac
plexus.
The Inferior Cardiac Branches {rami cardiaci inferiores; thoracic cardiac branches),
on the right side, arise from the trunk of the vagus as it lies by the side of the
THE ACCESSORY NERVE 913
trachea, and from its recurrent nerve; on the left side from the recurrent nerve only;
passing inward, they end in the deep part of the cardiac plexus.
The Anterior Bronchial Branches {rami bronchiales cmteriorrs; anterior or ventral
pulmonary branches), two or three in number, and of small size, are distributed
on the anterior surface of the root of the lung. They join with filaments from the
sympathetic, and form the anterior pulmonary plexus.
The Posterior Bronchial Branches [rami bronchiales yosteriores ; posterior or dorsal
pulmonary branches), more numerous and larger than the anterior, are distributed
on the posterior surface of the root of the lung; they are joined by filaments from
the third and fourth (sometimes also from the first and second) thoracic ganglia
of the sympathetic trunk, and form the posterior pulmonary plexus. Branches from
this plexus accompany the ramifications of the bronchi through the substance of
the lung.
The Esophageal Branches {rami cesophagei) are given off both above and below
the bronchial branches; the lower are numerous and larger than the upper. They
form, together with the branches from the opposite nerve, the esophageal plexus.
From this plexus filaments are distributed to the back of the pericardium.
The Gastric Branches {rami gastrici) are distributed to the stomach. The right
vagus forms the posterior gastric plexus on the postero-inferior surface of the stomach
and the left the anterior gastric plexus on the antero-superior surface.
The Celiac Branches {rami coeliaci) are mainly derived from the right vagus: they
join the celiac plexus and through it supply branches to the pancreas, spleen,
kidneys, suprarenal bodies, and intestine.
The Hepatic Branches {rami hepatici) arise from the left vagus : they join the hepatic
plexus and through it are conveyed to the liver.
THE ACCESSORY NERVE (N. ACCESSORIUS; ELEVENTH NERVE;
SPINAL ACCESSORY NERVE) (Figs. 792, 793, 794).
The accessory nerve consists of two parts: a cranial and a spinal.
The Cranial Part {ramus internus; accessory portion) is the smaller of the two.
Its fibers arise from the cells of the nucleus ambiguus and emerge as four or five
delicate rootlets from the side of the medulla oblongata, below the roots of the
vagus. It runs lateralward to the jugular foramen, where it interchanges fibers
with the spinal portion or becomes united to it for a short distance; here it is also
connected by one or two filaments with the jugular ganglion of the vagus. It
then passes through the jugular foramen, separates from the spinal portion and
is continued over the surface of the ganglion nodosum of the vagus, to the surface of
which it is adherent, and is distributed principally to the pharyngeal and superior
laryngeal branches of the vagus. Through the pharyngeal branch it probably sup-
plies the Musculus uvuhe and Levator veli palatini. Some few filaments from it
are continued into the trunk of the vagus below the ganglion, to be distributed with
the recurrent nerve and probably also wdth the cardiac nerves.
The Spinal Part {ramus externus; spinal portion) is firm in texture, and its fibers
arise from the motor cells in the lateral part of the anterior column of the gray sub-
stance of the medulla spinalis as low as the fifth cervical nerve. Passing through the
lateral funiculus of the medulla spinalis, they emerge on its surface and unite to
form a single trunk, which ascends between the ligamentum denticulatum and the
posterior roots of the spinal nerves, enters the skull through the foramen magnum,
and is then directed to the jugular foramen, through which it passes, lying in the
same sheath of dura mater as the vagus, but separated from it by a fold of the
arachnoid. In the jugular foramen, it receives one or two filaments from the
cranial part of the nerve, or else joins it for a short distance and then separates from
58
914
NEUROLOGY
it again. As its exit from the jugular foramen, it runs backward in front of the
internal jugular vein in 66.6 per cent, of cases, and behind in it 33.3 per cent.
(Tandler). The nerve then descends obliquely behind the Digastricus and Stylo-
hyoideus to the upper part of the Sternocleidomastoideus; it pierces this muscle,
and courses obliquely across the posterior triangle of the neck, to end in the deep
surface of the Trapezius. As it traverses the Sternocleidomastoideus it gives several
filaments to the muscle, and joins with branches from the second cervical nerve.
In the posterior triangle it unites with the second and third cervical nerves, while
beneath the Trapezius it forms a plexus with the third and fourth cervical nerves,
and from this plexus fibers are distributed to the muscle.
FlQ. 794. — Hypoglossal nerve, cervical plexus, and their branches.
THE HYPOGLOSSAL NERVE (N. HYPOGLOSSUS; TWELFTH NERVE)
(Figs. 794, 795).
The hypoglossal nerve is the motor nerve of the tongue.
Its fibers arise from the cells of the hypoglossal nucleus, which is an upward
prolongation of the base of the anterior column of gray substance of the medulla
spinalis. This nucleus is about 2 cm. in length, and its upper part corresponds
with the trigonum hypoglossi, or lower portion of the medial eminence of the rhom-
boid fossa (page 779). The lower part of the nucleus extends downward into the
closed part of the medulla oblongata, and there lies in relation to the ventro-lateral
THE HYPOGLOSSAL NERVE
915
aspect of the central canal. The fibers run forward through the medulla oblongata,
and emerge m the antero-lateral sulcus between the pyramid and the olive.
Tht rootlets of this nerve are collected into two bundles, which perforate the
dura mater separately, opposite the h>poglossal canal in the occipital bone, and
unite together after their passage through it; in some cases the canal is divided
mto two by a small bony spicule. The nerve descends almost vertically to a point
corresponding with the angle of the mandible. It is at first deeply seated beneath
the mternal carotid artery and internal jugular vein, and intimately connected with
the vagus nerve; it then passes forward between the vein and artery, and lower
To Dura mater
To Ganglion nodosum of vagus
- Hypoglossal nerve
-Branch from first cervical
to hypoglossal
TO MUSCLES
OF TONGUE
To Lingual nerve
TO GENIOHYOIDEUS
TO THYREOHYOIDEUS
TO SUPERIOR BELLY OF OMOHYOIDE.US
TO STERNOHYOIDEUS
TO STERNOTHYREOIDEUS
TO INFERIOR BELLY OF OMOHYOIDEUS
Fig. 795. — Plan of hypoglossal nerve.
down in the neck becomes superficial below the Digastricus. The nerve then loops
around the occipital artery, and crosses the external carotid and lingual arteries
below the tendon of the Digastricus. It passes beneath the tendon of the Digas-
tricus, the Stylohyoideus, and the Mylohyoideus, lying between the last-named
muscle and the Hyoglossus, and communicates at the anterior border of the Hyo-
glossus with the lingual nerve; it is then continued forward in the fibers of the
Genioglossus as far as the tip of the tongue, distributing branches to its muscular
substance.
Branches of Communication.- — Its branches of communication are, wath the
Vagus. First and second cervical nerves.
Sympathetic. Lingual.
The communications with the vagus take place close to the skull, numerous
filaments passing between the hypoglossal and the ganglion nodosum of the vagus
916 NEUROLOGY
through the mass of connective tissue which unites the two nerves. As the nerve
winds around the occipital artery it gives off a filament to the pharyngeal plexus.
The communication with the sympathetic takes place opposite the atlas by
branches derived from the superior cervical ganglion, and in the same situation
the nerve is joined by a filament derived from the loop connecting the first and
second cervical nerves.
The communications with the lingual take place near the anterior border of the
Hyoglossus by numerous filaments which ascend upon the muscle.
Branches of Distribution. — The branches of distribution of the hypoglossal nerve
are:
Meningeal. . Thyrohyoid.
Descending. ' Muscular.
Of these branches, the meningeal, descending, thyrohyoid, and the muscular
twig to the Geniohyoideus, are probably derived mainly from the branch which
passes from the loop between the first and second cervical to join the hypoglossal
(Fig. 795).
Meningeal Branches (dural branches) .^ As the hypoglossal nerve passes through
the hypoglossal canal it gives off, according to Luschka, several filaments to the
dura mater in the posterior fossa of the skull.
The Descending Ramus (ramus descendens; descendens hypoglossi), long and slender,
quits the hypoglossal where it turns around the occipital artery and descends in
front of or in the sheath of the carotid vessels; it gives a branch to the superior
belly of the Omohyoideus, and then joins the communicantes cervicales from the
second and third cervical nerves; just below the middle of the neck, to form a loop,
the ansa hypoglossi. From the convexity of this loop branches pass to supply
the Sternohyoideus, the Sternothyreoideus, and the inferior belly of the Omo-
hyoideus. According to Arnold, another filament descends in front of the vessels
into the thorax, and joins the cardiac and phrenic nerves.
The Thyrohyoid Branch (ramus thyreohyoideus) arises from the hypoglossal near
the posterior border of the hyoglossus; it runs obliquely across the greater cornu
of the hyoid bone, and supplies the Thyreohyoideus muscle.
The Muscular Branches are distributed to the Styloglossus, Hyoglossus, Genio-
hyoideus, and Genioglossus. At the under surface of the tongue numerous slender
branches pass upward into the substance of the organ to supply its intrinsic muscles.
THE SPINAL NERVES (NERVI SPINALES).
The spinal nerves spring from the medulla spinalis, and are transmitted through
the intervertebral foramina. They number thirty-one pairs, which are grouped
as follows: Cervical, 8; Thoracic, 12; Lumbar, 5; Sacral, 5; Coccygeal, 1.
The first cervical nerve emerges from the vertebral canal between the occipital
bone and the atlas, and is therefore called the suboccipital nerve; the eighth issues
between the seventh cervical and first thoracic vertebrae.
Nerve Roots. — Each nerve is attached to the medulla spinalis by two roots,
an anterior or ventral, and a posterior or dorsal, the latter being characterized by
the presence of a ganglion, the spinal ganglion.
The Anterior Root (radix anterior; ventral root) emerges from the anterior surface
of the medulla spinalis as a number of rootlets or filaments (fila radicularia),
which coalesce to form two bundles near the intervertebral foramen.
The Posterior Root (radix posterior; dorsal root) is larger than the anterior owing
to the greater size and number of its rootlets ; these are attached along the postero-
lateral furrow of the medulla spinalis and unite to form two bundles which join
the spinal ganglion. The posterior root of the first cervical nerve is exceptional
in that it is smaller than the anterior; it is occasionally wanting.
THE SPINAL NERVES
917
( ANTERIOR
■^ NERVE
The Spinal Ganglia {ganglion spinale) are collections of nerve cells on the posterior
roots of the spinal nerves. Each ganglion is oval in shape, reddish in color, and
its size bears a proportion to that of the nerve root on which it is situated; it is
bifid medially where it is joined by the two bundles of the posterior nerve root.
The gangUa are usually placed in the intervertebral foramina, immediately outside
the points where the nerve roots perforate the dura mater, but tliere are exceptions
to this rule; thus the ganglia of the first and second cervical nerves lie on the verte-
bral arches of the atlas and axis respectively, those of the sacral nerves are inside
the vertebral canal, wliile that on the posterior root of the coccygeal nerve is placed
within the sheath of dura mater.
Structure (Fig. 638). — The ganglia consist chiefly of unipolar nerve cells, and from these the
fibers of the posterior root take origin — the single process of each cell dividing after a short course
into a central fiber which enters the meduUa spinalis and a peripheral fiber which runs into the
spinal nerve. Two other forms of cells are, however, present, viz.: (a) the cells of Dogiel, whose
axons ramify close to the cell (type II, of Golgi), and are distributed entirely within the ganglion;
and (6) multipolar cells similar to those found in the sympathetic ganglia.
The ganglia of the first cervical nerve may be absent, while small aberrant ganglia consisting
of groups of nerve cells are sometimes found on the posterior roots between the spinal ganglia
and the medulla spinalis.
Each nerve root receives a covering from the pia mater, and is loosely invested
by the arachnoid, the latter being prolonged as far as the points where the roots
pierce the dura mater. The two roots
pierce the dura mater separately, each
receiving a sheath from this membrane;
where the roots join to form the spinal
nerve this sheath is continuous with the
epineurium of the nerve.
Size and Direction. — The roots of the
upper four cervical nerves are small,
those of the lower four are large. The
posterior roots of the cervical nerves
bear a proportion to the anterior of
three to one, which is greater tban in
the other regions; their individual fila-
ments are also larger than those of the
anterior roots. The posterior root of
the first cervical is an exception to this
rule, being smaller than the anterior
root; in eight per cent, of cases it is
wanting. The roots of the first and
second cervical nerves are short, and
run nearly horizontally to their points
of exit from the vertebral canal. From
the second to the eighth cervical they
are directed obliquely downward, the
obliquity and length of the roots succes-
sively increasing; the distance, however,
between the level of attachment of any
of these roots to the medulla spinalis and
the points of exit of the corresponding
nerves never exceeds the depth of one
vertebra.
The roots of the thoracic nerves, with the exception of the first, are of small
size, and the posterior only slightly exceed the anterior in thickness. They increase
successively in length, from above downward, and in the lower part of the thoracic
posterior")
NERVE y
ROOTS j
POSTERIO
ROOTS
TUM
LATUM
POSTERIOR
ROOTS
POSTERIOR
ROOTS
Fig. 790. — A portion of the spinal cord, showing its
right lateral surface. The dura is opened and arranged to
show the nerve roots. (Testut.)
918
XE UROLOGY
region descend in contact with the medulla spinalis for a distance equal to the height
of at least two vertebrae before they emerge from the vertebral canal.
Fig. 797. — Distribution of cutaneous nerves. Ventral aspect.
The roots of the lower lumbar and upper sacral nerves are the largest, and their
individual filaments the most numerous of all the spinal nerves, while the roots
of the coccygeal nerve are the smallest.
THE SPINAL NERVES
919
The roots of the himbar, sacral, and coccygeal nerves run vertically downward
to their respective exits, and as the medulla spinalis ends near the lower border
FiQ. 798. — Distribution of cutaneous nerves. Dorsal aspect.
of the first lumbar vertebra it follows that the length of the successive roots must
rapidly increase. As already mentioned (page 750), the term cauda equina is applied
to this collection of nerve roots.
920
NEUROLOGY
From the description given it will be seen that the largest nerve roots, and
consequently the largest spinal nerves, are attached to the cervical and lumbar
swellings of the medulla spinalis; these nerves are distributed to the upper and
lower limbs.
Connections with Sympathetic. — Immediately beyond the spinal ganglion, the
anterior and posterior nerve roots unite to form the spinal nerve which emerges
through the intervertebral foramen. Each spinal nerve receives a branch (gray
ramus communicans) from the adjacent ganglion of the sympathetic trunk, while
the thoracic, and the first and second lumbar nerves each contribute a branch
(white ramus communicans) to the adjoining sympathetic ganglion. The second,
third, and fourth sacral nerves also supply white rami; these, however, are not
connected with the ganglia of the sympathetic trunk, but run directly into the
pelvic plexuses of the sympathetic.
\ Sympathetie
— V — ganglion
Spinal nerve
Posterior
nerve root
Sympathetic
cord
Anterior
nerve root
Sympathetic
ganglion
Fig. 799. — Scheme showing structure of a typical spinal nerve. 1. Somatic efferent. 2. Somatic afferent. 3,4,5.
Sympathetic efferent. 6, 7. Sympathetic afferent.
Structure. — Each typical spinal nerve contains fibers belonging to two systems, viz., the
somatic, and the sympathetic or splanchnic, as well as fibers connecting these systems with each
other (Fig. 799).
1. The somatic fibers are efferent and afferent. The efferent fibers originate in the cells of the
anterior column of the medulla spinahs, and run outward through the anterior nerve roots to the
•spinal nerve. They convey impulses to the voluntary muscles, and are continuous from their
origin to their peripheral distribution. The afferent fibers convey impressions inward from the
skin, etc., and originate in the unipolar nerve cells of the spinal ganglia. The single processes
of these cells divide into peripheral and central fibers, and the latter enter the medulla spinahs
through the posterior nerve roots.
2. The sympathetic fibers are also efferent and afferent. The efferent fibers, preganglionic fibers,
originate in the lateral column of the medulla spinalis, and are conveyed through the anterior
nerve root and the white ramus communicans to the corresponding ganglion of the sympathetic
trunk; here they may end by forming synapses around its cells, or may run through the ganglion
to end in another of the ganglia of the sympathetic trunk, or in a more distally placed ganglion
THE CERVICAL NERVES
921
in one of the sympathetic plexuses. In all cases they end by forming synapses around other nerve
cells. From the cells of the gangha of the sympathetic trunk other fibers, postganglionic fibers,
take origin; some of these run through the gray rami communicantos to join the spinal nerves, along
which they are carried to the bloodvessels of the trunk and limbs, while others pass to the viscera,
either directly or after interruption in one of the distal ganglia. The afferent fibers are derived
partly from the unipolar cells and partly from the nmltipolar cells of the spinal ganglia. Their per-
ipheral processes are carred through the white rami communicantes, and after pa.ssing through one
or more sympathetic ganglia (but always without interrupticni in them) finally end in the ti.s.sues of
the viscera. The central processes of the unipolar cells enter the medulla si)inalis through the
posterior nerve root and form synapses around either somatic or sympathet ic efferent neurons, thus
completing reflex arcs. The dendrites of the multipolar nerve cells form synapses around the cells
of type II (cells of Dogiel) in the spinal ganglia, and by this path the original impulse is transferred
from the s>TTipathetic to the somatic system, through which it is conveyed to the sensorium.
Divisions. — After emerging from the intervertebral foramen, each spinal nerve
gives off a small meningeal branch which reenters the vertebral canal through the
intervertebral foramen and supplies the vertebrae and their ligaments, and the
bloodvessels of the medulla spinalis and its membranes. The spinal nerve then
splits into a posterior or dorsal, and an anterior or ventral division, each receiving
fibres from both nerve roots.
POSTERIOR DIVISIONS OF THE SPINAL NERVES (RAMI POSTERIORES).
The posterior divisions are as a rule smaller than the anterior. They are directed
backward, and, with the exceptions of those of the fir.st cervical, the fourth and
fifth sacral, and the coccygeal, divide into medial and lateral branches for the supply
of the muscles and skin (Figs. 800, 801, 802) of the posterior part of the trunk.
GREAT OCCIPI.
TAL NERVE
RECTUS CAPITIS
LATERALIS
ANTERIOR PRIMARY DIVI-
SION OF FIRST CERVICAL
VERTEBRAL ARTERY
OUT
OBLIQUUS
SUPERIOR
RPNCH TO COMPLEXUS — 001
VERTEBRAL ARTERY
POSTERIOR PRIMARY DIVI
8I0N OF FIRST CERViCALl
POSTERIOR PRIMARY DIVISION
OF FIRST CERVICAL
ANASTOMOTIC BRANCH
ANASTOMOTIC
THIRD CERVICAL
Fig. 800. — Posterior primary divisions of the upper three cervical nerves. (Testut.)
The Cervical Nerves (Nn. Cervicales).
The posterior division of the first cervical or suboccipital nerve is larger than
the anterior di\ision, and emerges abo\e the posterior arch of the atlas and beneath
the vertebral artery. It enters the suboccipital triangle and supplies the muscles
which bound this triangle, viz., the Rectus capitis posterior major, and the Obliqui
superior and inferior; it gives branches also to the Rectus capitis posterior minor
922
NEUROLOGY
and the Semispinalis capitis. A filament from the branch to the Obliquus inferior
joins the posterior division of the second cervical nerve.
The nerve occasionally gives off a cutaneous branch which accompanies the occipital artery
to the scalp, and communicates with the greater and lesser occipital nerves.
Fjo 801 —Diagram of the distribution of Fio. 802.— Areas of distribution of the cutaneous branches of the
the cutaneous branches of the posterior posterior divisions of the spinal nerves The areas of the medial
divisions of the spinal nerves. branches are in black, those of the lateral in red. (H. M. Johnston.)
The posterior division of the second cervical nerve is much larger than the
anterior division, and is the greatest of all the cervical posterior divisions. It
emerges between the posterior arch of the atlas and the lamina of the axis, below
the Obliquus inferior. It supplies a twig to this muscle, receives a communicating
filament from the posterior division of the first cervical, and then divides into a
large medial and a small lateral branch.
THE THORACIC NERVES 923
The medial branch {rarrms medialis; internal branch), called from its size and
distribution the greater occipital nerve {n. occipitalis major; great occipital nerve),
ascends obliquely between the Obliquus inferior and the Semispinalis capitis, and
pierces the latter muscle and the Trapezius near their attachments to the occipital
bone (Fig. 801). It is then joined by a filament from the medial branch of the
posterior division of the third cervical, and, ascending on the back of the head
with the occipital artery, divides into branches which communicate with the lesser
occipital nerve and supply the skin of the scalp as far forward as the vertex of the
skull. It gives off muscular branches to the Semispinalis capitis, and occasionally
a twig to the back of the auricula. The lateral branch (ramus lateralis; external
branch) supplies filaments to the Splenius, Longus capitis, and Semispinalis capitis,
and is often joined by the corresponding branch of the third cervical.
The posterior division of the third cervical is intermediate in size between those
of the second and fourth. Its medial branch runs between the Semispinalis capitis
and cervicis, and, piercing the Splenius and Trapezius, ends in the skin. While
under the Trapezius it gives off a branch called the third occipital nerve, which pierces
the Trapezius and ends in the skin of the lower part of the back of the head (Fig.
801). It lies medial to the greater occipital and communicates with it. The
lateral branch often joins that of the second cervical.
The posterior division of the suboccipital, and the medial branches of the posterior division
of the second and third cervical nerves are sometimes joined by commimicating loops to form
the posterior cervical plexus (Cruveilhier) .
The posterior divisions of the lower five cervical nerves divide into medial
and lateral branches. The medial branches of the fourth and fifth run between the
Semispinales cervicis and capitis, and, having reached the spinous processes,
pierce the Splenius and Trapezius to end in the skin (Fig. 801). Sometimes the
branch of the fifth fails to reach the skin. Those of the lower three nerves are
small, and end in the Semispinales cervicis and capitis, Multifidus, and Inter-
spinales. The lateral branches of the lower five nerves supply the Iliocostalis
cervicis, Longissimus cervicis, and Longissimus capitis.
The Thoracic Nerves (Nn. Thoracales).
The medial branches (ramus medialis; internal branch) of the posterior divisions of
the upper six thoracic nerves run between the Semispinalis dorsi and Multifidus,
which they supply; they then pierce the Rhomboidei and Trapezius, and reach
the skin by the sides of the spinous processes (Fig. 801). The medial branches
of the lower six are distributed chiefly to the Multifidus and Longissimus dorsi,
occasionally they give off filaments to the skin near the middle line.
The lateral branches (ramus lateralis; external branch) increase in size from above
downward. They run through or beneath the Longissimus dorsi to the interval
between it and the Iliocostales, and supply these muscles; the lower five or six
also give off cutaneous branches which pierce the Serratus posterior inferior and
Latissimus dorsi in a line with the angles of the ribs (Fig. 801). The lateral
branches of a variable number of the upper thoracic nerves also give filaments
to the skin. The lateral branch of the twelfth thoracic, after sending a filament
medialward along the iliac crest, passes downward to the skin of the buttock.
The medial cutaneous branches of the posterior divisions of the thoracic nerves descend for
some distance close to the spinous processes before reaching the skin, while the lateral branches
travel downward for a considerable distance — it may be as much as the breadth of four ribs —
before they become superficial; the branch from the twelfth thoracic, for instance, reaches the
skin only a Uttle way above the iUac crest.'
See article by H. M. Johnston, Journal of Anatomy and Physiology, vol. xliii.
924
NEUROLOGY
The Lumbar Nerves (Nn. Lumbales).
The medial branches of the posterior divisions of the lumbar nerves run close to the
articular processes of the vertebrae and end in the ^lultifidus.
The lateral branches supply the Sacrospinalis. The upper three give off cutaneous
nerves which pierce the aponeurosis of the Latissimus dorsi at the lateral border of
the Sacrospinalis and descend across the posterior part of the iliac crest to the skin
of the buttock (Fig. 801), some of their twigs running as far as the level of the
greater trochanter.
OF LOWER SACRAL NERVES
Fig. 803. — The. posterior divisions of the sacral nerves.
The Sacral Nerves (Nn. Sacrales).
The posterior divisions of the sacral nerves {rami 'posteriores) (Fig. 803) are
small, and diminish in size from above downward; they emerge, except the last,
through the posterior sacral foramina. The upper Three are covered at their points
of exit by the INIultiiidus, and divide into medial and lateral branches.
The medial branches are small, and end in the Multifidus.
The lateral branches join with one another and with the lateral branches of the
posterior divisions of the last lumbar and fourth sacral to form loops on the dorsal
surface of the sacrum. From these loops branches run to the dorsal surface of the
sacrotuberous ligament and form a second series of loops under the Glutaeus maxi-
mus. From this second series cutaneous branches, two or three in number, pierce
the Gluta^us maximus along a line drawn from the posterior superior iliac spine to
the tip of the cocc\'x; they supply the skin over the posterior part of the buttock.
The posterior divisions of the lower two sacral nerves are small and lie below the
INIultifidus. They do not divide into medial and lateral branches, but unite with
each other and with the posterior division of the coccygeal nerve to form loops on
the back of the sacrum ; filaments from these loops supply the skin over the coccyx.
THE CERVICAL NERVES
925
The Coccygeal Nerve (N. Coccygeus).
The posterior division of the coccygeal nerve {ramus posterior) does not divide
into a medial and a lateral branch, but receives, as already stated, a communicating
branch from the last sacral; it is distributed to the skin over the back of the coccyx.
ANTERIOR DIVISIONS OF THE SPINAL NERVES (RAMI ANTERIORES).
The anterior divisions of the spinal nerves supply the antero-lateral parts of the
trunk, and the limbs; they are for the most part larger than the posterior divisions.
In the thoracic region they run independently of one another, but in the cervical,
lumbar, and sacral regions they unite near their origins to form plexuses.
The Cervical Nerves (Nn. Cervicales).
The anterior divisions of the cervical nerves (raini anteriores) , with the exception
of the first, pass outward between the Intertransversarii anterior and posterior,
lying on the grooved upper surfaces of the transverse processes of the vertebrae.
The anterior division of the first or suboccipital nerve issues from the vertebral canal
above the posterior arch of the atlas and runs forward around the lateral aspect
of its superior articular process, medial to the vertebral artery. In most cases it
descends medial to and in front of the Rectus capitis lateralis, but occasionally it
pierces the muscle.
The anterior divisions of the upper four cervical nerves unite to form the cervical
plexus, and each receives a gray ramus communicans from the superior cervical
ganglion of the sympathetic trunk. Those of the lower four cervical, together with
the greater part of the first thoracic, form the brachial plexus. They each receive
a gray ramus communicans, those for the fifth and sixth being derived from the
middle, and those for the seventh and eighth from the lowest, cervical ganglion
of the sympathetic trunk.
The Cervical Plexus {plexus cervicalis) (Fig. 804). — The cervical plexus is formed
by the anterior divisions of the upper four cervical nerves; each nerve, except
the first, divides into an upper and a lower branch, and the branches unite to form
three loops. The plexus is situated opposite the upper four cervical vertebrae, in
front of the Levator scapuhie and Scalenus medius, and covered by the Sterno-
cleidomastoideus.
Its branches are divided into two groups, superficial and deep, and are here
given in tabular form; the figures following the names indicate the nerves from
which the different branches take origin:
Smaller occipital
Great auricular .
I Cutaneous cervical
.Supraclavicular
Superficial
Internal
Deep
Communicating
Muscular
With hypoglossal
vagus
2 C
2, 3, C.
2, 3, C.
3, 4, C.
1, 2, C.
1, 2, C.
1,2,3,4,0.
" sympathetic
Rectus capitis lateralis 1, C
Rectus capitis anterior 1, 2, C.
External
Longus capitis . . 1, 2, 3, C.
Communicantes cervi-
cales . . . 2, 3, C.
.Phrenic . . . 3, 4, 5, C.
Communicating with accessory . . . 2, 3, 4, C.
Sternocleidomastoideus 2, C.
Trapezius . . . 3, 4, C.
[Muscular . • j Levator scapulae . . 3, 4, C.
(Scalenus medius . 3, 4, C.
926
NEUROLOGY
Superficial Branches of the Cervical Plexus (Fig. 805). — The Smaller Occipital
Nerve (/i. occipitalis' minor; small occipital nerve) arises from the second cervical
nerve, sometimes also from the third; it curves around and ascends along the
posterior border of the Sternocleidomastoideus. Near the cranium it perforates
the deep fascia, and is continued upward along the side of the head behind the
auricula, supplying the skin and communicating with the greater occipital, the
great auricular, and the posterior auricular branch of the facial. The smaller
occipital varies in size, and is sometimes duplicated.
R.C.A. MIN.
R. A. MAJ.
COMMUNICATING TO
HYPOGLOSSAL
SYMPATHETIC
LONGUS COLU *
/ RECTUS ANT. MAJOR
TO GENIOHYOID
TO THYROHYOID
SUBMANDIBULAR
BR. OF FACIAL
f;
LEVATOR ANGULI SCAP.
A SCALENUS MEDIUS
FROM SYMPATHETIC
TRAPEZIUS
Fig. 804. — ^Plan of the cer\-ical plexus. (Gerrish.)
It gives off an auricular branch, which supplies the skin of the upper and back
part of the auricula, communicating with the mastoid branch of the great auricular.
This branch is occasionally derived from the greater occipital nerve.
The Great Auricular Nerve {n. aiiricularis magnus) is the largest of the ascending
branches. It arises from the second and third cervical nerves, winds around the
posterior border of the Sternocleidomastoideus, and, after perforating the deep
THE CERVICAL NERVES
927
fascia, ascends upon that muscle beneath the Platysma to the parotid gland, where
it divides into an anterior and a posterior bfanch.
The anterior branch {rannts anterior; facial branch) is distributed to the skin of
the face over the parotid gland, and communicates in the substance of the gland
with the facial nerve.
Termination
of supratrochlear
of infralrochlear
of nasociliary
Fig. 805. — The nerves of the scalp, face, and side of neck.
The posterior branch {ramus posterior; mastoid branch) supplies the skin over the
mastoid process and on the back of the auricula, except at its upper part; a filament
pierces the auricula to reach its lateral surface, where it is distributed to the lobule
I and lower part of the concha. The posterior branch communicates with the smaller
occipital, the auricular branch of the vagus, and the posterior auricular branch
of the facial.
The Cutaneous Cervical (n. cidanevs colli; svperficial or transverse cervical nerve)
arises from the second and third cervical nerves, turns around the posterior border
of the Sternocleidomastoideus about its middle, and, passing obliquely forward
beneath the external jugular vein to the anterior border of the muscle, it perforates
the deep cervical fascia, and divides beneath the Platysma into ascending and
descending branches, which are distributed to the antero-lateral parts of the neck.
The ascending branches {rami superiores) pass upward to the submaxillary region.
928 NEUROLOGY
and form a plexus with the cervical branch of the facial nerve beneath the Platysma;
others pierce that muscle, and are distributed to the skin of the upper and front
part of the neck.
The descending branches {rami inferiores) pierce the Platysma, and are distributed
to the skin of the side and front of the neck, as low as the sternum.
The Supraclavicular Nerves {nn. supraclaviculares; descending branches) arise from
the third and fourth cer\ical nerves; they emerge beneath the posterior border
of the.Sternocleidomastoideus,.and descend in the posterior triangle of the neck
beneath the Platysma and deep cervical fascia. Near the clavicle they perforate
the fascia and Platysma to become cutaneous, and are arranged, according to
their position, into three groups — anterior, middle and posterior.
The anterior supraclavicular nerves (nn. supraclaviculares anteriores; suprasternal
nerves) cross obliquely over the external jugular vein and the clavicular and sternal
heads of the Sternocleidomastoideus, and supply the skin as far as the middle line.
They furnish one or two filaments to the sternoclavicular joint.
The middle supraclavicular nerves (nn. supraclaviculares medii; supraclavicular
nerves) cross the clavicle, and supply the skin over the Pectoralis major and Del-
toideus, communicating with the cutaneous branches of the upper intercostal nerves.
The postevioT sui>rsicl&yicula,Tnerves (nn . supraclaviculares posteriores; supra-acromial
nerves) pass obliquely across the outer surface of the Trapezius and the acromion,
and supply the skin of the upper and posterior parts of the shoulder.
Deep Branches of the Cervical Plexus. Internal Series. — The Communicating
Branches consist of several filaments, which pass from the loop between the first
and second cervical nerves to the vagus, hypoglossal, and sympathetic. The branch
to the hypoglossal ultimately leaves that nerve as a series of branches, viz., the
descending ramus, the nerve to the Thyreohyoideus and the nerve, to the Genio-
hyoideus (see page 916). A communicating branch also passes from the fourth
to the fifth cervical, while each of the first four cervical nerves receives a gray
ramus communicans from the superior cervical ganglion of the sympathetic.
Muscular Branches supply the Longus capitis, Rectus capitis anterior, and Rectus
capitis lateralis.
The Communicantes Cervicales {commmiicanies hypoglossi) (Fig. 804) consist
usually of two filaments, one derived from the second, and the other from the third
cervical. These filaments join to form the descendens cervicalis, which passes
downward on the lateral side of the internal jugular ^•ein, crosses in front of the
Aein a little below the middle of the neck, and forms a loop (ansa hypoglossi) with
the descending ramus of the hypoglossal in front of the sheath of the carotid
vessels (see page 916). Occasionally, the loop is formed within the sheath.
The Phrenic Nerve (n. phrenicus; internal respiratory nerve of Bell) contains njotor
and sensory fibers in the proportion of about two to one. It arises chiefly from the
fourth cervical nerve, but receives a branch from the third and another from the
fifth; the fibers from the fifth occasionally come through the nerve to the Sub-
clavius. It descends to the root of the neck, running obliquely across the front
of the Scalenus anterior, and beneath the Sternocleidomastoideus, the inferior
belly of the Omohyoideus, and the transverse cervical and transverse scapular
vessels. It next passes in front of the first part of the subclavian artery, between
it and the subclavian vein, and, as it enters the thorax, crosses the internal mam-
mary artery near its origin. ^Vithin the thorax, it descends nearly vertically in
front of the root of the lung, and then between the pericardium and the medias-
tinal pleura, to the diaphragm, where it divides into branches, which pierce
that muscle, and are distributed to its under surface. In the thorax it is accom-
panied by the pericardiacophrenic branch of the internal mammary artery.
The two phrenic nerves differ in their length, and also in their relations at the
upper part of the thorax.
THE CERVICAL NERVES
929
The right nerve is situated more deeply, and is shorter and more vertical in
direction than the left; it lies lateral to the right innominate vein and superior
vena cava.
The left nerve is rather longer than the right, from the inclination of the heart
to the left side, and from the diaphragm being lower on this than on the right side.
At the root of the neck it is crossed by the thoracic duct; in the superior mediastinal
cavity it lies between the left common carotid and left subclavian arteries, and
crosses superficial to the vagus on the left side of the arch of the aorta.
PERICARO
BRAN
RAMIFICATIONS
OF PHRENIC
Fig. 806. — The phrenic nerve and its relations with the vagus nerve.
Each nerve supplies filaments to the pericardium and pleura, and at the root
of the neck is joined by a filament from the sympathetic, and, occasionally, by
one from the ansa hypoglossi. Branches have been described as passing to the
peritoneum.
From the right nerve, one or two filaments pass to join in a small phrenic ganglion
with phrenic branches of the celiac plexus; and branches from this ganglion are
59
930
NEUROLOGY
distributed to the falciform and coronary ligaments of the liver, the suprarenal
gland, inferior vena cava, and right atrium. From the left nerve, filaments pass to
join the phrenic branches of the celiac plexus, but without any ganglionic enlarge-
ment; and a twig is distributed to the left suprarenal gland.
Deep Branches of the Cervical Plexus. External Series. — Communicating
Branches. — The external series of deep branches of the cervical plexus communi-
cates with the accessory nerve, in the substance of the Sternocleidomastoideus,
in the posterior triangle, and beneath the Trapezius.
Muscular Branches are distributed to the Sternocleidomastoideus, Trapezius,
Levator scapula?, and Scalenus medius.
The branch for the Sternocleidomastoideus is derived from the second cervical;
the Trapezius and Levator scapulse receive branches from the third and fourth.
The Scalenus medius receives twigs either from the third or fourth, or occasionally
from both.
Frow.'WC,
To Rhomboidei-
Tojoin the phrenic ■
Suprascapular
To Subclavius
Latfral anterior
thoracic
Musculo-
cutaneous
Axillary
Median
To Longus colli
and Scalcni
To Lonrjus colli
and Scaleni
To Longus colli
and Scaleni
Long thoracic
To Longus colli
and Scaleni
Ulnar J Medial brachial
Medial antibrachial cutaneous
cutaneous
Fig. 807. — Plan of brachial plexus.
The Brachial Plexus (plexus brachialis) (Fig. 807). — The brachial plexus is
formed by the union of the anterior divisions of the lower four cervical nerves and
the greater part of the anterior division of the first thoracic nerve; the fourth cer-
vical usually gives a branch to the fifth cervical, and the first thoracic frequently
receives one from the second thoracic. The plexus extends 'from the lower part
of the side of the neck to the axilla. The nerves which form it are nearly equal in
size, but their mode of communication is subject to some variation. The following
is, however, the most constant arrangement* The fifth and sixth cervical unite
soon after their exit from the intervertebral foramina to form a trunk. The eighth
cervical and first thoracic also unite to form one trunk, while the seventh cervical
THE CERVICAL NERVES
931
runs out alone. Three trunks — upper, middle, and lower — are thus formed, and,
as they pass beneath the clavicle, each splits into an anterior and a posterior divi-
sion.'^ Tlie anterior divisions of the upper and middle trunks unite to form a cord,
which is situated on the lateral side of the second part of the axillary artery, and
is called the lateral cord or fasciculus of the plexus. The anterior division of the
lower trunk passes down on the medial side of the axillary artery, and forms the
medial cord or fasciculus of the brachial plexus. The posterior divisions of all three
trunks unite to form tiie posterior cord or fasciculus of the plexus, which is situated
behind the second portion of the axillary artery.
Relations. — In the neck, the brachial plexus lies in the posterior triangle, being covered by the
skin, Platysma, and deep fascia; it is crossed by the supraclavicular nerves, the inferior belly
of the Omohyoideus, the external jugular vein, and the transverse cervical artery. It emerges
between the Scaleni anterior and medius; its upper part lies above the third part of the sub-
clavian artery, while the trunk formed by the union of the eighth cervical and first thoracic is
placed behind the artery; the plexus next passes behind the clavicle, the Subclavius, and the trans-
verse scapular vessels, and lies upon the first digitation of the Serratus anterior, and the Sub-
scapularis. In the axilla it is placed lateral to the first portion of the axillary artery; it surrounds
the second part of the artery, one cord lying medial to it, one lateral to it, and one behind it;
at the lower part of the axilla it gives off its terminal branches to the upper limb.
ANTE
DIVISK
JRTH CER\i
^k AN
SUPRASCAPULAR
DESCENDING
BRANCH OF
HYPOGLOSSAL
SA
HYPOGLOSSI
PHRENIC
THYROID
AXIS
INTERNAL
MAMMARY
ARTERY
SUBCLAVIAN
BRANCH TO
PHRENIC
ANTERIOR
THORACIC
Fig. SOS. — The rifjht brachial plexus with its short branches, viewed from in front. The Sternoniastoid and Trapezius
muscles have been completely, the Omohyoid and Subclavius have been partially, removed; a piece has been sawed out
of the clavicle; the Pectoralis muscles have been incised and reflected. (Spalteholz.)
Branches of Communication.^ — Close to their exit from the intervertebral foramina
the fifth and sixth cervical nerves each receive a gray ramus communicans from
the middle cervical ganglion of the sympathetic trunk, and the seventh and eighth
cervical similar twigs from the inferior ganglion. The first thoracic nerve receives
a gray ramus from, and contributes a white ramus to, the first thoracic ganglion.
1 The posterior division of the lower trunk ia very much smaller than the others, and is frequently derived entirely
from the eighth cervical nerve.
932
NEUROLOGY
On the Scalenus anterior the phrenic nerve is joined by a branch from the fifth
cervical.
Branches of Distribution. — The branches of distribution of the brachial plexus
may be arranged into two groups, viz., those given off above and those below the
clavicle.
Supraclavicular Branches.
Dorsal scapular 5 C.
Suprascapular 5, 6 C.
Nerve to Subclavius 5, 6 C.
Long thoracic 5, 6, 7 C.
To Longus colli and Scaleni 5, 6, 7, 8 C.
MUSCULOCUTANEOUS
NERVC
INTERCOSTO-HUMERAL
NERVES
LESSER INTERNAL
CUTANEOUS NERVES
NERVES
LATERAL CUTA-
NEOUS BRANCH
OF FOURTH
INTERCOSTAL
LATERAL CUTANEOUS
BRANCH OF
THIRD INTERCOSTAL
LONG THORACIC
NERVE
Fig. 809. — The right brachial plexus (infraclavicular portion) in the axillary fossa; viewed from below and in
front. The Pectoralis major and minor muscles have been in large part removed; their attachments have been
reflected. (Spalteholz.)
The Dorsal Scapular Nerve (n. dorsalis scapulce; nerve to the Rhomhoidei; posterior
scapidar nerve) arises from the fifth cervical, pierces the Scalenus medius, passes
beneath the Levator scapulse, to which it occasionally gives a twig, and ends in
the Rhomboidei.
The Suprascapular (w. svprascapularis) (Fig. 818) arises from the trunk formed
by the union of the fifth and sixth cervical nerves. It runs lateralward beneath
the Trapezius and the Omohyoideus, and enters the supraspinatous fossa through
the suprascapular notch, below, the superior transverse scapular ligament; it then
passes beneath the Supraspinatus, and curves around the lateral border of the
spine of the scapula to the infraspinatous fossa. In the supraspinatous fossa it
gives off two branches to the Supraspinatus muscle, and an articular filament
to the shoulder-joint; and in the infraspinatous fossa it gives off two branches
THE CERVICAL NERVES
933
to the Infraspinatous muscle, besides some filaments to the shoulder-joint and
scapula.
The_ Nerve to the Subclavius (n. suhclamus) is a small filament, which arises from
the pomt of junction of the fifth and sixth cervical nerves; it descends to the muscle
in front of the third part of the subclavian artery and the lower trunk of the plexus,
and is usually connected by a filament with the phrenic nerve.
The Long Thoracic Nerve (/?. thoracalis longus; external respiratory nerve of Bell;
posterior thoracic nerve) (Fig. 816) supplies the Serratus anterior. It usually arises
by three roots from the fifth, sixth, and seventh cervical nerves; but the root from
the seventh nerve may be absent. The roots from the fifth and sixth nerves pierce
the Scalenus medius, while that from the seventh passes in front of the muscle.
The nerve descends behind the brachial plexus and the axillary vessels, resting
on the outer surface of the Serratus anterior. It extends along the side of the thorax
to the lower border of that muscle, supplying filaments to each of its digitations.
The branches for the Longus colli and Scaleni arise from the lower four cervical
nerves at their exit from the intervertebral foramina.
Infraclavicular Branches.
The infraclavicular branches are derived from the three cords of the brachial
plexus, but the fasciculi of the nerves may be traced through the plexus to the spinal
nerves from which they originate. They are as follows:
Lateral cord
Medial cord
Posterior cord
Musculocutaneous
\ Lateral anterior thoracic
[Lateral head of median .
Medial anterior thoracic
Medial antibrachial cutaneous
iVIedial brachial cutaneous
Ulnar
Medial head of median
Upper subscapular .
Lower subscapular .
Thoracodorsal .
Axillary
Radial
5, 6, 7 C.
5, 6, 7 C.
6, 7C.
8 C, 1 T.
5, 6C.
5, 6C.
5, 6, 7 C.
5, 6C.
6, 7, 8 C, 1 T.
The Anterior Thoracic Nerves {nn. thoracales anteriores) (Fig. 816) supply the
Pectorales major and minor.
The lateral anterior thoracic {fasciculus lateralis) the larger of the two, arises
from the lateral cord of the brachial plexus, and through it from the fifth, sixth,
and seventh cervical nerves. It passes across the axillary artery and vein, pierces the
coracoclavicular fascia, and is distributed to the deep surface of the Pectoralis
major. It sends a filament to join the medial anterior thoracic and form with it
a loop in front of the first part of the axillary artery.
The medial anterior thoracic {fasciculus medialis) arises from the medial cord of
the plexus and through it from the eighth cervical and first thoracic. It passes
behind the first part of the axillary artery, curves forward between the axillary
artery and vein, and unites in front of the artery with a filament from the lateral
nerve. It then enters the deep surface of the Pectoralis minor, where it divides
into a number of branches, which supply the muscle. Two or three branches pierce
the muscle and erid in the Pectoralis major.
The Subscapular Nerves {nn. suhscapidares) , two in number, spring from the
posterior cord of the plexus and through it from the fifth and sixth cervical nerves.
934
NEUROLOGY
The upper subscapular (sJiort subscapular), the smaller enters the upper part of
the Subscapularis, and is frequently represented by two branches.
The lower subscapular supplies the lower part of the Subscapularis, and ends in
the Teres major; the latter muscle is sometimes supplied by a separate branch.
The Thoracodorsal Nerve {». thoracodorsalis; middle or long subscapular nerve),
a branch of the posterior cord of the plexus, derives its fibers from the fifth, sixth,
and seventh cervical nerves; it follows the course of the subscapular artery, along
the posterior wall of the axilla to the Latissimus dorsi, in which it may be traced
as far as the lower border of the muscle.
UPERIOR BRANCH
OF AXJLLARY
NFERIOR BRANCH
OF AXILLARY
CUTANEOUS
BRANCHES
Fig. 810. — Suprascapular and axillary nerves of right side, seen from behind. (Testut.)
The Axillary Nerve {n. axillaris; circumflex nerve) (Fig. 818) arises from the pos-
terior cord of the brachial plexus, and its fibers are derived from the fifth and sixth
cervical nerves. It lies at first behind the axillarv arter^•, and in front of the
Subscapularis, and passes downward to the lower border of that muscle. It then
winds backward, in company with the posterior humeral circumflex artery, through
a quadrilateral space bounded above by the Subscapularis, below by the Teres
major, medially by the long head of the Triceps brachii, and laterally by the
surgical neck of the humerus, and divides into an anterior and a posterior branch.
The anterior branch (upper branch) winds around the surgical neck of the humerus,
beneath the Deltoideus, with the posterior humeral circumflex ^"essels, as far as
the anterior border of that muscle, supplying it, and giving off a few small cuta-
neous branches, which pierce the muscle and ramify in the skin covering its lower
part.
The posterior branch {lower branch) supplies the Teres minor and the posterior
part of the Deltoideus; upon the branch to the Teres minor an oval enlargement
(pseudoganglion) usually exists. The posterior branch then pierces the deep fascia
and is continued as the lateral brachial cutaneous nerve, which sweeps around the
posterior border of the Deltoideus and supplies the skin over the lower two-thirds
of the posterior part of this muscle, as well as that covering the long head of the
Triceps brachii (Figs 811, S13).
THE CERVICAL NERVES
935
The trunk of the axillary nerve gives off an articular filament which enters
the shoulder-joint below the Subscapularis.
The Musculocutaneous Nerve (n. musculocidaneus) (Fig. 816) arises from the
lateral cord of the brachial plexus, opposite the lower border of the Pectoralis
Super fie. br
of radial—
C. 6. 7. 8.
Fig. 811. — Cutaneous nerves of right upper
extremity. Anterior view.
Fig. 812. — Diagram of segmental distribution of the cutaneous
nerves of the right upper extremity. Anterior view.
minor, its fibers being derived from the fifth, sixth, and seventh cervical nerves.
It pierces the Coracobrachialis muscle and passes obliquely between the Biceps
brachii and the Brachialis, to the lateral side of the arm; a little above the elbow
it pierces the deep fascia lateral to the tendon of the Biceps brachii and is continued
into the forearm as the lateral antibrachial cutaneous nerve. In its course through
936
NEUROLOGY
the arm it supplies the Coracobrachiahs, Biceps brachii, and the greater part of the
Brachialis. The branch to the Coracobrachiahs is given off from the nerve close
to its origin, and in some instances as a separate filament from the lateral cord
of the plexus; it is derived from the se^■enth cervical nerve. The branches to the
Biceps brachii and Brachialis are given oft' after the musculocutaneous has pierced
Intercosio
brachial
T. 2.
Medial
brachial
cutaneous
T. 1. i'.
FIg. 813. — Cutaneous nerves of right upper
extremity. Posterior view.
Median
C. 5.6.7.8.
Fig. 814. — Diagram of segmental distribution of the cuta-
neous nerves of the right upper extremity. Posterior view.
the Coracobrachiahs; that supplying the Brachialis gives a filament to the elbow-
joint. The nerve also sends a small branch to the bone, which enters the nutrient
foramen with the accompanying artery.
The lateral antibrachial cutaneous nerve {n. cnianeus antihrachii cutaneous lateralis;
branch of musculocutaneous nerve) passes behind the cephalic vein, and divides,
opposite the elbow-joint, into a volar and a dorsal branch (Figs. 811, 813).
THE CERVICAL NERVES 937
The volar branch {ramus volaris; anterior branch) descends along the radial border
of the forearm to the wrist, and supplies the skin over the lateral half of its volar
surface. At the wrist-joint it is placed in front of the raxlial artery, and some
filaments, piercing the deep fascia, accompany that \essel to the dorsal surface of
the carpus. The ner\e then passes downward to the ball of the thumb, where it
ends in cutaneous filaments. It communicates with the superficial branch of the
radial nerve, and with the palmar cutaneous branch of the median nerve.
The dorsal branch {ramus dorsalis; 'posterior branch) descends, along the dorsal
surface of the radial side of the forearm to the wrist. It supplies the skin of the
lower two-thirds of the dorso-lateral surface of the forearm, communicating with
the superficial branch of the radial nerve and the dorsal antibrachial cutaneous
branch of the radial.
The musculocutaneous nerve presents frequent irregularities. It may adhere
for some distance to the median and then pass outward, beneath the Biceps brachii,
instead of through the Coracobrachialis. Some of the fibers of the median may
run for some distance in the musculocutaneous and then leave it to join their
proper trunk; less frequently the reverse is the case, and the median sends a branch
to join the musculocutaneous. The nerve may pass under the Coracobrachialis
or through the Biceps brachii. Occasionally it gives a filament to the Pronator
teres, and it supplies the dorsal surface of the thumb when the superficial branch
of the radial nerve is absent.
The Medial Antibrachial Cutaneous Nerve (n. ciitaneus antibrachii medialis; internal
cutaneous nerve) (Fig. 816) arises from the medial cord of the brachial plexus. It
derives its fibers from the eighth cervical and first thoracic nerves, and at its com-
mencement is placed medial to the axillary artery. It gives off, near the axilla, a
filament, which pierces the fascia and supplies the integument covering the Biceps
brachii, nearly as far as the elbow. The nerve then runs down the ulnar side of the
arm medial to the brachial artery, pierces the deep fascia with the basilic vein,
about the middle of the arm, and divides into a volar and an ulnar branch.
The volar branch {ramus volaris; anterior branch), the larger, passes usually in front
of, but occasionally behind, the vena mediana cubiti {median basilic vein). It then
descends on the front of the ulnar side of the forearm, distributing filaments to the
skin as far as the wrist, and communicating with the palmar cutaneous branch of
the ulnar nerve (Fig. 811).
The ulnar branch {ramus idnaris; posterior branch) passes obliquely downward on
the medial side of the l)asilic ^ein, in front of the medial epicondyle of the humerus,
to the back of the forearm, and descends on its ulnar side as far as the wrist, dis-
tributing filaments to the skin. It communicates with the medial brachial cutaneous,
the dorsal antibrachial cutaneous branch of the radial, and the dorsal branch of
the ulnar (Fig. 813).
The Medial Brachial Cutaneous Nerve {)i. cutaneus brachii medialis; lesser internal
cutaneous nerve; nerve of Wrisberg) is distributed to the skin on the ulnar side of the
arm (Figs. 811, 813). It is the smallest branch of the brachial plexus, and arising
from the medial cord receives its fibers from the eighth cer\ical and first thoracic
ner^•es. It passes through the axilla, at first lying behind, and then medial to the
axillary \em, and communicates with the intercostobrachial ner^•e. It descends
along the medial side of the brachial artery to the middle of the arm, where it pierces
the deep fascia, and is distributed to the skin of the back of the lower third of the
arm, extending as far as the elbow, where some filaments are lost in the skin in
front of the medial epicondyle, and others over the olecranon. It communicates
with the ulnar branch of the medial antibrachial cutaneous nerve.
In some cases the medial brachial cutaneous and intercostobrachial are connected bj- two or
three filaments, which form a plexus in the axilla. In other cases the intercostobrachial is of
large size, and takes the place of the medial brachial cutaneous, receiving merelj- a filament of
commmiication from the brachial plexus, which represents the latter nerve; in a few cases, this
filament is wanting.
938 NEUROLOGY
The Median Nerve (/?. medianus) (Fig. 816) extends along the middle of the arm
and forearm to the hand. It arises by two roots, one from the lateral and one from
the medial cord of the brachial plexus; these embrace the lower part of the axillary
artery, uniting either in front of or lateral to that vessel. Its fibers are derived
from the sixth, seventh, and eighth cervical and first thoracic nerves. As it descends
through the arm, it lies at first lateral to the brachial artery; about the level of the
insertion of the Coracobrachialis it crosses the artery, usually in front of, but occasion-
all}' behind it, and lies on its medial side at the bend of the elbow, where it is situated
behind the lacertus fibrosus {bicipital fascia) , and is separated from the elbow-joint
by the Brachialis. In the forearm it passes between the two heads of the Pronator
teres and crosses the ulnar artery, but is separated from this vessel by the deep
head of the Pronator teres. It descends beneath the Flexor digitorum sublimis, ■
lying on the Flexor digitorum profundus, to within 5 cm. of the transverse carpal
ligament; here it becomes more superficial, and is situated between the tendons of
the Flexor digitorum sublimis and Flexor carpi radialis. In this situation it lies
behind, and rather to the radial side of, the tendon of the Palmaris longus, and is
covered by the skin and fascia. It then passes behind the transverse carpal liga-
ment into the palm of the hand. In its course through the forearm it is accompanied
by the median artery, a branch of the volar interroseous artery.
Branches. — With the exception of the nerve to the Pronator teres, which some-
times arises above the elbow-joint, the median nerve gives off no branches in
the arm. As it passes in front of the elbow, it supplies one or two twigs to the
joint.
In the forearm its branches are: muscular, volar interosseous, and palmar.
The muscular branches {rami viusculares) are derived from the nerve near the
elbow and supply all the superficial muscles on the front of the forearm, except
the Flexor carpi ulnaris.
The volar interosseous nerve (/i. interosseus [antibrachii] volaris; anterior inter-
osseous nerve) supplies the deep muscles on the front of the forearm, except the ulnar
half of the Flexor digitorum profundus. It accompanies the volar interosseous
artery along the front of the interosseous membrane, in the interval between the
Flexor pollicis longus and Flexor digitorum profundus, supplying the whole of the
former and the radial half of the latter, and ending below in the Pronator quadratus
and wrist-joint.
The palmar branch {ramus cutaneits palmaris n. mediani) of the median nerve arises
at the lower part of the forearm. It pierces the volar carpal ligament, and divides into
a lateral and a medial branch ; the lateral branch supplies the skin over the ball of
the thumb, and communicates with the volar branch of the lateral antibrachial
cutaneous nerve; the medial branch supplies the skin of the palm and communi-
cates with the palmar cutaneous branch of the ulnar.
In the palm of the hand the median nerve is covered by the skin and the palmar
aponeurosis, and rests on the tendons of the Flexor muscles. Immediately after
emerging from under the transverse carpal ligament the nerve becomes enlarged
and flattened and splits into a smaller, lateral, and a larger, medial portion. The
lateral portion supplies a short, stout branch to certain of the muscles of the ball of
the thumb, viz., the Abductor brevis, the Opponens, and the superficial head of the
Flexor brevis, and then divides irito three proper volar digital nerves; two of these
supply the sides of the thumb, while the third gives a twig to the first Lumbricalis
and is distributed to the radial side of the index finger. The medial portion of the
nerve divides into two common volar digital nerves. The first of these gives a twig
to the second Lumbricalis and runs toward the cleft between the index and middle
fingers, where it divides into two proper digital nerves for the adjoining sides of
these digits; the second runs toward the cleft between the middle and ring fingers,
and splits into two proper digital nerves for the adjoining sides of these digits;
THE CERVICAL NERVES
939
it communicates with a branch from the ulnar nerve and sometimes sends a twig
to the third LumbricaHs.
Each proper digital nerve, opposite the base of the first phalanx, gives ofT a
dorsal branch which joins the dorsal digital nerve from the superficial branch of
the radial nerve, and supplies the integument on the dorsal aspect of the last
phalanx. At the end of the digit, the proper digital nerve divides into two
branches, one of which supplies the pulp of the finger, the other ramifies around
and beneath the nail. The proper digital nerves, as they run along the fingers, are
placed superficial to the corresponding arteries.
ULNAR
POSTERIOR BRANC
OF RADIAL
MEDIA
ANTERIOR BRANCH
OF RADIAL
PALMAR CUTANEOUS
OF MEDIAN
MUSCULAR TO ABDUCTOR,
OPPONENS. AMD FLEXOR
BREVIS POLLICIS
SUPERFICIAL BRANCH
OF ULNAR
COLLATERALS
TO THUMB
COMMUNICATING
TO MEDIAN
Fig. 815. — Superficial palmar nerves. (Testut.)
The Ulnar Nerve (/(. nlnaris) (Fig. 816) is placed along the medial side of the limb,
and is distributed to the muscles and skin of the forearm and hand. It arises
from the medial cord of the brachial plexus, and derives its fibers from the eighth
cervical and first thoracic nerves. It is smaller than the median, and lies at first
behind it, but diverges from it in its course down the arm. At its origin it lies
940
NEUROLOGY
medial to the axillary artery, and bears the same relation to the brachial artery
as far as the middle of the arm. Here it pierces the medial intermuscular septum,
Lateral anterior thoracic
Ulnar
Med. antibrach. cutaneous
Radial
Deep br. 0/ radial
Su-perfic. br. of radial
Volar i)Uerosseotis
1
Fig. 816. — Nerves of the left upper extremity.
THE CERVICAL NERVES
941
runs obliquely across the medial head of the Triceps brachii, and descends to the
groove between the medial epicondyle and the olecranon, accompanied by the
superior ulnar collateral artery. At the elbow, it rests upon the back of the medial
epicondyle, and enters the forearm between the two heads of the Flexor carpi
ulnaris. In the forearm, it descends along the ulnar side lying upon the Flexor
digitorum profundus; its upper half is covered by the Flexor carpi ulnaris, its lower
VOLAR
NTEROSSEOUS
RADIAL*
LNAR NERVE
INTERNAL BRANCH
OF RADIAL
EXTERNAL BRANCil
OF RADIAL
BRANCH Of-- ANTERIOR
NTEROSSEOUS TO
WRIST JOINT
TERMINATION OF )
ULNAR IN THUMB
MUSCLES
RVE TO THIRD
D FOURTH
MBRICALS
Fig. 817. — Deep palmar nerves. (Testut.)
half lies on the lateral side of the muscle, covered by the integument and fascia. In
the upjier third of the forearm, it is separated from the ulnar artery by a consider-
able interval, but in the rest of its extent lies close to the medial side of the artery.
About 5 cm. above the wrist it ends by dividing into a dorsal and a volar branch.
The branches of the ulnar nerve are: articular to the elbow-joint, muscular,
palmar cutaneous, dorsal, and volar.
942
NEUROLOGY
Axillary
Radial
The articular branches to the elbow-joint are several small filaments which arise
from the nerve as it lies in the g^oo^•e between the medial epicondyle and olecranon.
The muscular branches {rami
Suprascapular ^^ musculares) two in number, arise
near the elbow : one supplies the
Flexor carpi ulnaris; the other,
the ulnar half of the Flexor
digitorum profundus.
The palmar cutaneous branch
{ramus cutancus palmaris) arises
about the middle of the forearm,
and descends on the ulnar arterv,
giving off some filaments to the
vessel. It perforates the volar
carpal ligament and ends in the
skin of the palm, communicating
with the palmar branch of the
median nerve.
The dorsal hrsinch {ramus dor-
salis manus) arises about 5 cm.
above the wrist ; it passes back-
ward beneath the Flexor carpi
ulnaris, perforates the deep fas-
cia, and, running along the ulnar
side of the back of the wrist
and hand, divides into two dor-
sal digital branches; one supplies
the ulnar side of the little finger;
the other, the adjacent sides of
the little and ring fingers. It
also sends a twig to join that
given by the superficial branch
of the radial nerve for the ad-
joining sides of the middle and
ring fingers, and assists in sup-
plying them. A branch is dis-
tributed to the metacarpal region
of the hand, communicating
with a twig of the superficial
branch of the radial nerve (Fig.
813).
On the little finger the dor-
sal digital branches extend only
as far as the base of the ter-
minal phalanx, and on the ring
finger as far as the base of the
second phalanx; the more distal
parts of these digits are supplied by dorsal branches derived from the proper volar
digital branches of the ulnar nerve.
The volar branch {ramus rolaris manus) crosses the transverse carpal ligament
on the lateral side of the pisiform bone, medial to and a little behind the ulnar
artery. It ends by dividing into a superficial and a deep branch.
The superficial branch {ramus superficialis [n. ulnaris] (supplies the Palmaris
brevis, and the skin on the ulnar side of the hand, and divides into a proper volar
Deep branch
of radial
FiQ. 818. — The suprascapular, axillary, and radial nerves.
THE CERVICAL NERVES 943
digital branch for the ulnar side of the little finger, and a common volar digital
branch which gives a communicating twig to the median nerve and divides into
two proper digital nerves for the adjoining sides of the little and ring fingers (Fig.
811). The proper digital branches are distributed to the fingers in the same
manner as those of the median.
The deep branch {ramus profundus) accompanied by the deep branch of the ulnar
artery, passes between the Abductor digiti quinti and Flexor digiti quinti brevis;
it then perforates the Opponens digiti quinti and follows the course of the deep
volar arch beneath the Flexor tendons. At its origin it supplies the three short
muscles of the little finger. As it crosses the deep part of the hand, it supplies all
the Interossei and the third and fourth Lumbricales; it ends by supplying the Ad-
ductores pollicis and the medial head of the Flexor pollicis brevis. It also sends
articular filaments to the wrist-joint.
It has been pointed out that the ulnar part of the Flexor digitorum profundus
is supplied by the ulnar nerve; the third and fourth Lumbricales, which are con-
nected with the tendons of this part of the muscle, are supplied by the same
nerve. In like manner the lateral part of the Flexor digitorum profundus and
the first and second Lumbricales are supplied by the median nerve; the third
Lumbricalis frequently receives an additional twig from the median nerve.
The Radial Nerve (n. radialis; musculospiral nerve) (Fig. 818), the largest branch
of the brachial plexus, is the continuation of the posterior cord of the plexus. Its
fibres are derived from the fifth, sixth, seventh, and eighth cervical and first thoracic
nerves. It descends behind the first part of the axillary artery and the upper part
of the brachial artery, and in front of the tendons of the Latissimus dorsi and Teres
major. It then winds around from the medial to the lateral side of the humerus in
a groove with the a. profunda brachii, between the medial and lateral heads of the
Triceps brachii. It pierces the lateral intermuscular septum, and passes between
the Brachialis and Brachioradialis to the front of the lateral epicondyle, where
it divides into a superficial and a deep branch.
The branches of the musculospiral nerve are:
JNIuscular. Superficial.
Cutaneous. ■ Deep.
The muscular branches (ravii musculares) supply the Triceps brachii, Ancon.TUS,
Brachioradialis, Extensor carpi radialis longus, and Brachialis, and are grouped as
medial, posterior, and lateral.
The medial muscular branches supply the medial and long heads of the Triceps
brachii. That to the medial head is a long, slender filament, which lies close to the
ulnar nerve as far as the lower third of the arm, and is therefore frequently spoken
of as the ulnar collateral nerve.
The posterior muscular branch, of large size, arises from the nerve in the groove
between the Triceps brachii and the humerus. It divides into filaments, which
supply the medial and lateral heads of the Triceps brachii and the Anconseus
muscles. The branch for the latter muscle is a long, slender filament, which descends
in the substance of the medial head of the Triceps brachii.
The lateral muscular branches supply the Brachioradialis, Extensor carpi radialis
longus, and the lateral part of the Brachialis.
The cutaneous branches are two in number, the posterior brachial cutaneous
and the dorsal antibrachial cutaneous.
The posterior brachial cutaneous nerve (n. cutaneus brachii posterior; internal
cutaneous branch of musculospiral) arises in the axilla, with the medial muscular
branch. It is of small size, and passes through the axilla to the medial side of
the area supplying the skin on its dorsal surface nearly as far as the olecranon.
In its course it crosses behind, and communicates with, the intercostobrachial.
944 NEUROLOGY
The dorsal antibrachial cutaneous nerve (??. cuianens antibrachii dorsaUs; external
cutaneous branch of ))insculosi)iral) perforates the lateral head of the Triceps brachii at
its attachment to the humerus. The upper and smaller branch of the nerve passes
to the front of the elbow, lying close to the cephalic vein, and supplies the skin
of the lower half of the arm (Fig. 811). The lower branch pierces the deep fascia
below the insertion of the Deltoideus, and descends along the lateral side of the
arm and elbow, and then along the back of the forearm to the wrist, supplying
the skin in its course, and joining, near its termination, with the dorsal branch
of the lateral antibrachial cutaneous nerve (Fig. 813).
The Superficial Branch of the Radial Nerve (ramus snperfirialis radial nerve)
passes along the front of the radial side of the forearm to the commencement of
its lower third. It lies at first slightly lateral to the radial artery, concealed
beneath the Brachioradialis. In the middle third of the forearm, it lies behind the
same muscle, close to the lateral side of the artery. It quits the artery about 7 cm.
above the wrist, passes beneath the tendon of the Brachioradialis, and, piercing
the deep fascia, divides into two branches (Fig. 813).
The lateral branch, the smaller, supplies the skin of the radial side and ball
of the thumb, joining with the volar branch of the lateral antibrachial cutaneous
nerve.
The medial branch communicates, above the wrist, with the dorsal branch of the
lateral antibrachial cutaneous, and, on the back of the hand, with the dorsal
branch of the ulnar nerve. It then divides into four digital nerves, which are
distributed as follows: the first supplies the ulnar side of the thumb; the second,
the radial side of the index finger; the third, the adjoining sides of the index and
middle fingers; the fourth communicates with a filament from the dorsal branch
of the ulnar nerve, and supplies the adjacent sides of the middle and ring
fingers.^
The Deep Branch of the Radial Nerve (n. interosseus dorsalis; dorsal or posterior
interosseous nerve) winds to the back .of the forearm around the lateral side of the
radius between the two planes of fibers of the Supinator, and is prolonged down-
ward between the superficial and deep layers of muscles, to the middle of the
forearm. Considerably diminished in size, it descends, as the dorsal interosseous
nerve, on the interosseous membrane, in front of the Extensor pollicis longus, to the
back of the carpus, where it presents a gangliform enlargement from which filaments
are distributed to the ligaments and articulations of the carpus. It supplies all
the muscles on the radial side and dorsal surface of the forearm, excepting the
Ancona?us, Brachioradialis, and Extenosr carpi radialis longus.
The Thoracic Nerves (Nn. Thoracales).
The anterior divisions of the thoracic nerves (rami anteriores; ventral divisions)
are twelve in number on either side. Eleven of them are situated between the ribs,
and are therefore termed intercostal; the twelfth lies below the last rib. Each nerve
is connected with the adjoining ganglion of the sympathetic trunk by a gray and a
white ramus communicans. The intercostal nerves are distributed chiefly to the
parietes of the thorax and abdomen, and differ from the anterior divisions of the
other spinal nerves, in that each pursues an independent course, i. e., there is no
plexus formation. The first two nerves supply fibers to the upper limb in addition
to their thoracic branches; the next four are limited in their distribution to the
parietes of the thorax; the lower five supply the parietes of the thorax and abdomen.
The twelfth thoracic is distributed to the abdominal wall and the skin of the buttock.
' According to Hutchison, the digital nerve to the thumb reaches only as high as the root of the nail; the one to the
forefinger as high as the middle of the second phalanx; and the one to the middle and ring fingers not higher than the
first phalangeal joint. — London Hosp. Gaz., iii, 319.
THE THORACIC NERVES
945
The First Thoracic Nerve, — The anterior division of the first thoracic nerve divides
into two branches: one, the larger, leaves the thorax in front of the neck of the first
rib, and enters the brachial plexus; the other and smaller branch, the first intercostal
nerve, runs along the first intercostal space, and ends on the front of the chest as
the first anterior cutaneous branch of the thorax. Occasionally this anterior cuta-
neous branch is wanting. The first intercostal nerve as a rule gives off no lateral
cutaneous branch; but sometimes it sends a small branch to communicate with
the intercostobrachial. From the second thoracic nerve it frequently receives a
connecting twig, which ascends over the neck of the second rib.
Posterior division
Lateral cutaneous
Fig. 819.-
Anterior cutaneous
-Diagram of the course and branches of a tj-pica intercostal nerve.
The Upper Thoracic Nerves {nn. intercostales) . — The anterior divisions of the
second, third, fourth, fifth, and sixth thoracic nerves, and the small branch from the
first thoracic, are confined to the parietes of the thorax, and are named thoracic
intercostal nerves. They pass forward (Fig. 819) in the intercostal spaces below the
intercostal vessels. At the back of the chest they lie between the pleura and the
posterior intercostal membranes, but soon pierce the latter and run between the
two planes of Intercostal muscles as far as the middle of the rib. They then enter
the substance of the Intercostales interni, and, running amidst their fibers as far as
the costal cartilages, they gain the inner surfaces of the muscles and lie between
them and the pleura. Near the sternum, they cross in front of the internal mammary
artery and Transversus thoracis muscle, pierce the Intercostales interni, the anterior
intercostal membranes, and Pectoralis major, and supply the integument of the
front of the thorax and over the mamma, forming the anterior cutaneous branches
of the thorax; the branch from the second nerve unites with the anterior supra-
clavicular nerves of the cervical plexus.
Branches. — Numerous slender muscular filaments supply the Intercostales, the
Subcostales, the Levatores costarum, the Serratus posterior superior, and the Trans-
versus thoracis. At the front of the thorax some of these branches cross the costal
cartilages from one intercostal space to another.
Lateral cutaneous branches {rami cutanei laterales) are derived from the intercostal
nerves, about midway between the vertebrae and sternum; they pierce the Inter-
60
946
NEUROLOGY
costales externi and Serratus anterior, and divide into anterior and posterior
branches. The anterior branches run forward to the side and the forepart of the
chest, supplying the skin and the mamma; those of the fifth and sixth nerves
INTEROOSTO-
BRACHIAL
ANTERIOR CUTANEOUS
J NERVES OF THORAX
LATERAL CUTA-
NEOUS OF III TO
XI THORACIC )
LATERA
NEOUS
THORACIC
ANT. CUTANEOUS
OF X, XI, AND
XII THORACIC
Fig. 820. — Cutaneous distribution oi thoracic nerves. (Testut.)
supply the upper digitations of the Obliquus externus abdominis. The posterior
branches run backward, and supply the skin over the scapula and Latissimus dorsi.
The lateral cutaneous branch of the second intercostal nerve does not divide,
like the others, into an anterior and a posterior branch; it is named the intercosto-
THE THORACIC NERVES
947
brachial nerve (Fig. 816). It pierces the Intercostalis externus and the Serratus
anterior, crosses the axilla to the medial side of the arm, and joins with a filament
from the medial brachial cutaneous nerve. It then i)ierces the fascia, and supplies
the skin of the upper half of the medial and posterior part of the arm, communicat-
INTERCOSTO
BRACHIAL
LATERAL CUTANEOUS^)
BRANCHES OF III '
TO XI THOHACIC
LATERAL CUTA-1
NEOUS OF XI
THORACIO
ILIOHYPOGASTRI
Fig. 821. — Intercostal nerves, the superficial muscles having been removed. (Testut).
ing with the posterior brachial cutaneous branch of the radial nerve. The size
of the intercostobrachial nerve is in inverse proportion to that of the medial brachial
cutaneous nerve. A second intercostobrachial nerve is frequently given off from
the lateral cutaneous branch of the third intercostal; it supplies filaments to the
axilla and medial side of the arm.
948 NEUROLOGY
The Lower Thoracic Nerves. — The anterior divisions of the seventh, eighth, ninth,
tenth, and eleventh thoracic nerves are continued anteriorly from the intercostal
spaces into the abdominal wall; hence they are named thoracicoabdominal inter-
costal nerves. They have the same arrangement as the upper ones as far as the
anterior ends of the intercostal spaces, where they pass behind the costal cartilages,
and between the Obliquus internus and Transversus abdominis, to the sheath of
the Rectus abdominis, which they perforate. They supply the Rectus abdominis
and end as the anterior cutaneous branches of the abdomen; they supply the skin
of the front of the abdomen. The lower intercostal nerves supply the Intercostales
and abdominal muscles; the last three send branches to the Serratus posterior
inferior. About the middle of their course they give off lateral cutaneous branches.
These pierce the Intercostales externi and the Obliquus externus abdominis, in the
same line as the lateral cutaneous branches of the upper thoracic nerves, and divide
into anterior and posterior branches, which are distributed to the skin of the abdo-
men and back; the anterior branches supply the digitations of the Obliquus externus
abdominis, and extend downward and forward nearly as far as the margin of the
Rectus abdominis; the posterior branches pass backward to supply the skin over
the Latissimus dorsi.
The anterior division of the twelfth thoracic nerve is larger than the others; it
runs along the lower border of the twelfth rib, often gives a communicating branch
to the first lumbar nerve, and passes under the lateral lumbocostal arch. It then
runs in front of the Quadratus lumborum, perforates the Trans\ersus, and passes
forward between it and the Obliquus internus to be distributed in the same manner
as the lower intercostal nerves. It communicates with the iliohypogastric nerve
of the lumbar plexus, and gives a branch to the Pyramidalis. The lateral cutaneous
branch of the last thoracic nerve is large, and does not divide into an anterior and
a posterior branch. It perforates the Obliqui internus and externus, descends o^■e^
the iliac crest in front of the lateral cutaneous branch of the iliohypogastric (Fig.
819), and is distributed to the skin of the front part of the gluteal region, some of
its filaments extending as low as the greater trochanter.
The Lumbosacral Plexus (Plexus Lumbosacralis).
The anterior divisions of the lumbar, sacral, and coccygeal nerves form the
lumbosacral plexus, the first lumbar nerve being frequently joined by a branch
from the twelfth thoracic. For descriptive purposes this plexus is usually divided
into three parts — the lumbar, sacral, and pudendal plexuses.
The Lumbar Nerves (Nn. Lumbales).
The anterior -divisions of the lumbar nerves {rami anteriores) increase in size
from above downward. They are joined, near their origins, by gray rami com-
municantes from the lumbar ganglia of the sympathetic trunk. These rami consist
of long, slender branches which accompany the lumbar arteries around the sides of
the vertebral bodies, beneath the Psoas major. Their arrangement is somewhat
irregular: one ganglion may give rami to two lumbar nerves, or one lumbar nerve
may receive rami from two ganglia. The first and second, and sometimes the
third and fourth lumbar nerves are each connected with the lumbar part of the
sympathetic trunk by a white ramus communicans.
The nerves pass obliquely outward behind the Psoas major, or between its
fasciculi, distributing filaments to it and the Quadratus lumborum. The first
three and the greater part of the fourth are connected together in this situation
by anastomotic loops, and form the lumbar plexus. The smaller part of the fourth
joins with the fifth to form the lumbosacral trunk, which assists in the formation
i
THE LUMBAR NERVES
949
of the sacral plexus. The fourth nerve is named the nervus furcalis, from the fact
that it is subdi\i(led between the two plexuses. ^
The Lumbar Plexus^ (plexus lumbalis) (Figs. 822, 823, 824).— The lumbar plexus is
formed by the loops of communication between the anterior divisions of the first
three and the greater part of the fourth lumbar nerves; the first lumbar often
receives a branch from the last thoracic nerve. It is situated in the posterior part
of the Psoas major, in front of the transverse processes of the lumbar vertebrae.
— From 12lh thoracic
— lit lumbar
Iliohypogastric
Jlioinguiiial
Gemtofemoral
Lat, femoral cuianecus
To Psoas and
lliacus
2nd lumbar
3rd lumhar
■iih lumbar
otk lumbar
Femoral
Accessory obturator
Obturator
Lumbosacral trunk
Fig. 822. — Plan of lumbar plexus.
The mode in which the plexus is arranged varies in different subjects. It differs
from the brachial plexus in not forming an intricate interlacement, but the several
nerves of distribution arise from one or more of the spinal nerves, in the following
manner: the first lumbar nerve, frequently supplemented by a twig from the last
thoracic, splits into an upper and lower branch; the upper and larger branch divides
into the iliohypogastric and ilioinguinal nerves; the lower and smaller branch
unites with a branch of the second lumbar to form the genitofemoral nerve. The
remainder of the second nerve, and the third and fourth nerves, divide into ventral
and dorsal divisions. The ventral division of the second unites with the ventral
divisions of the third and fourth nerves to form the obturator nerve. The dorsal
divisions of the second and third nerves divide into two branches, a smaller branch
from each uniting to form the lateral femoral cutaneous nerve, and a larger branch
from each joining with the dorsal division of the fourth nerve to form the femoral
1 In most cases the fourth lumbar is the nervus furcalis; but this arrangement is frequently departed from. The
third is occasionally the lowest nerve which enters the lumbar plexus, giving at the same time some fibers to the sacral
plexus, and thus formiftg the nervus furcalis; or both the third and fourth may be furcal nerves. When this occurs,
the plexus is termed Aiff^ or prefixed. More frequently the fifth nervals divided between the lumbar and sacral plexuses,
and constitutes the nervus furcalis; and when this takes place, the plexus is distinguished as a low or posCfixed plexus.
These variations necessarily produce corresponding modifications in the sacral plexus.
2 Bardeen, Amer. Jour. Anat., 1907, vol. vi.
950
NEUROLOGY
nerve. The accessory obturator, when it exists, is formed by the union of two small
branches given off from the third and fourth nerves.
.\\&V\\ w i'lL IJM , ,
Fig. 823. — The lumbar plexus and its branches.
The branches of the lumbar plexus may therefore be arranged as follows:
Iliohypogastric
Ihoinguinal .
Genitofemoral
1 L.-
IL.
1, 2L.
Dorsal divisions.
Lateral femoral cutaneous 2, 3 L.
Femoral 2, 3, 4 L.
Ventral divisions.
Obturator 2, 3, 4 L.
Accessory obturator 3, 4 L.
The Iliohypogastric Nerve {n. iliohypogastricus) arises from the first lumbar nerve.
It emerges from the upper part of the lateral border of the Psoas major, and crosses
obliquely in front of the Quadratus lumborum to the iliac crest. It then perforates
the posterior part of the Transversus abdominis, near the crest of the ilium, and
THE LUMBAR NERVES
951
divides between that muscle and the Obliquus internus abdominis into a lateral
and an anterior cutaneous branch.
The lateral cutaneous branch (ramus cutaneus lateralis; iliac branch) pierces the
Obliqui internus and externus immediately above the iliac crest, and is distributed
to the skin of the gluteal region, behind the lateral cutaneous branch of the last
thoracic nerve (Fig. 830) ; the size of this branch bears an inverse proportion to that
of the lateral cutaneous branch of the last thoracic nerve.
FIRST LUMBAR'
NERVE TO QUADRA
TUS LUMSORUM
TRANSVERSA LIS j-
OBLIQUUS INTERNUS -|\
OBLIQUUS EXTERNUS
SECOND LUMBAR
ILIOHYPOGASTRIC
THIRD LUMBAR
ILIAC BRANCH OF
ILIOHYPOGASTRIC
ABDOMINAL BRANCH
OF I
THORACIC / r\ )l^i|
LUMBAR PORTION
/OF SYMPATHETIC
TWELFTH THORACIC
FOURTH LUMBAR
FIFTH LUMBAR
ILIOINGUINAL
LATERAL FEMORAL
CUTANEO
OBTURATOR NERVE
EXTERNAL SPERMATIC
BRANCH OF GENITO-
FEMORAL
LUMBOINGUINAL BRANCH
OF GENITOFEMORAL
POSTERIOR BRANCH OF
LATERAL FEMORAL
CUTANEOUS
ANTERIOR BRANCH OF
LATERAL FEMORAL
CUTANEOUS
— ' ff- d', ^' Bi^
. BRANCH / ^'=. ij" J^
LIOHYPO. I f'Ri'Mk^^
ILIOHYPOGASTRIC
ILIOINGUINAL
GENITOFEMORAL
"''-^^'^ — RAMUS COMMU-
LAT. FEMORAL
CUTANEOUS
GENITOFEMORAL
EXTERNAL SPERMATIC
BRANCH
LUMBOINGUINAL BRANCH
APONEUROSIS OF EX-
TERNAL OBLIQUE
DORSAL NERVE
OF PENIS
Fig. 824. — Deep and superficial dissection of the lumbar plexus. (Testut.;
The anterior cutaneous branch (ramus cutaneus anterior; hypogastric branch)
(Fig. 825) continues onward between the Obliquus internus and Transversus. It
then pierces the Obliquus internus, becomes cutaneous by perforating the aponeu-
rosis of the Obliquus externus about 2.5 cm. above the subcutaneous inguinal ring,
and is distributed to the skin of the hypogastric region.
The iliohypogastric nerve communicates with the last thoracic and ilioinguinal
nerves.
952
NEUROLOGY
The Ilioinguinal Nerve («. iUoinguinaJis), smaller than the preceding, arises with
it from the first lumbar nerve. It emerges from the lateral border of the Psoas
*^
A
Sfpog
h
-. vA
? •-:
lU
Sural-
rUl
Deep peroncEal
s
Deep
peronceal
L.U.5.
FiQ. 825. — Cutaneous nerves of right lower extremity.
Front view.
Fig. 826. — Diagram of segmental distribution of
the cutaneous nerves of the right lower extremity-
Front ^new.
THE LUMBAR NERVES 953
major just below the iliohypogastric, and, passing obliquely across the Quadratus
lumborum and Iliacus, perforates the Transversus abdominis, near the anterior
part of the iliac crest, and communicates with the iliohypogastric nerve between the
Transversus and the Obliquus internus. The nerve then pierces the Obliquus
internus, distributing filaments to it, and, accompanying the spermatic cord through
the subcutaneous inguinal ring, is distributed to the skin of the upper and medial
part of the thigh, to the skin over the root of the penis and upper part of the scrotum
in the male, and to the skin covering the mons pubis and labium majus in the female.
The size of this nerve is in inverse proportion to that of the iliohypogastric. Occa-
sionally it is very small, and ends by joining the iliohypogastric; in such cases, a
branch from the iliohypogastric takes the place of the ilioinguinal, or the latter
nerve may be altogether absent.
The Genitofemoral Nerve {n. genitofemoral^^- genitocrural nerve) arises from the
first and second lumbar nerves. It passes obliquely through the substance of the
Psoas major, and emerges from its medial border, close to the vertebral column,
opposite the fibrocartilage between the third and fourth lumbar vertebrae; it
then descends on the surface of the Psoas major, under cover of the peritoneum,
and divides into the external spermatic and lumboinguinal nerves. Occasionally
these two nerves emerge separately through the substance of the Psoas.
The external spermatic nerve {n. sperrnaiicus externus; genital branch of genito-
femoral) passes outward on the Psoas major, and pierces the fascia transversalis, or
passes through the abdominal inguinal ring; it then descends behind the spermatic
cord to the scrotum, supplies the Cremaster, and gives a few filaments to the skin
of the scrotum. In the female, it accompanies the round ligament of the uterus,
and is lost upon it.
The lumboinguinal nerve («. lumhoinguinalis; femoral or crural branch of genito-
femoral) descends on the external iliac artery, sending a few filaments around it,
and, passing beneath the inguinal ligament, enters the sheath of the femoral vessels,
lying superficial and lateral to the femoral artery. It pierces the anterior layer of
the sheath of the vessels and the fascia lata, and supplies the skin of the anterior
surface of the upper part of the thigh (Fig. 825). On the front of the thigh it
communicates with the anterior cutaneous branches of the femoral nerve. A few
filaments from the lumboinguinal nerve may be traced to the femoral artery.
The Lateral Femoral Cutaneous Nerve (w. cutaneus femoralis lateralis; external
cutaneous nerve) arises from the dorsal divisions of the second and third lumbar
nerves. It emerges from the lateral border of the Psoas major about its middle,
and crosses the Iliacus obliquely, toward the anterior superior iliac spine. It then
passes under the inguinal ligament and over the Sartorius muscle into the thigh,
where it divides into two branches, an anterior and a posterior (Fig. 825).
The anterior branch becomes superficial about 10 cm. below the inguinal ligament,
and divides into branches which are distributed to the skin of the anterior and
lateral parts of the thigh, as far as the knee.. The terminal filaments of this nerve
frequently communicate with the anterior cutaneous branches of the femoral nerve,
and with the infrapatellar branch of the saphenous nerve, forming with them the
patellar plexus.
The posterior branch pierces the fascia lata, and subdivides into filaments which
pass backward across the lateral and posterior surfaces of the thigh, supplying
the skin from the level of the greater trochanter to the middle of the thigh.
The Obturator Nerve (ti. obturatorius) arises from the ventral divisions of the
second, third, and fourth lumbar nerves; the branch from the third is the largest,
while that from the second is often very small. It descends through the fibers
of the Psoas major, and emerges from its medial border near the brim of the pelvis ;
it then passes behind the common iliac vessels, and on the lateral side of the hypo-
gastric vessels and ureter, which separate it from the ureter, and runs along the
954
NEUROLOGY
Lateral
femoral
cutaneous '
Femoral
Psoas major
Ant.
cutanexms-
':<-■
;V
Anterior division
of obturator
Med. hr. of ant.
cutaneous
PE M ORI J
//W
%
lateral wall of the lesser pelvis, above and in front of the obturator vessels, to
the upper part of the obturator foramen. Here it enters the thigh, and divides
into an anterior and a posterior
liacus branch, which are separated at
first by some of the fibers of the
Obturator externus, and lower
down by the Adductor brevis.
The anterior branch {ramus
anterior) (Fig. 827) leaves the
pelvis in front of the Obturator
externus and descends in front of
the Adductor brevis, and behind
the Pectineus and Adductor
longus ; at the lower border of.
the latter muscle it communi-
cates with the anterior cutaneous
and saphenous branches of the
femoral nerve, forming a kind of
plexus. It then descends upon
the femoral artery, to which it
■ Sapiienaus Jg finally distributed. Near the
obturator foramen the nerve gives
off an articular branch to the hip-
joint. Behind the Pectineus, it
distributes branches to the Ad-
ductor longus and Gracilis, and
usually to the Adductor brevis,
and in rare cases to the Pecti-
neus ; it receives a communicating
branch from the accessory ob-
turator nerve when that nerve is
present.
Occasionally the communicat-
Superjicial g i|!W; \ "Ijill ing branch to the anterior cuta-
peroneal-^ g^^^ \ l|||||j^ ncous and Saphenous branches of
the femoral is continued down,
as a cutaneous branch, to the
thigh and leg. When this is so, it
Deep __Wll 1 (II If emerges from beneath the lower
peroneal \|\^V 1 111 1 border of the Adductor longus,
descends along the posterior
margin of the Sartorius to the
medial side of the knee, where it
pierces the deep fascia, communi-
cates with the saphenous nerve,
and is distributed to the skin of
the tibial side of the leg as low
down as its middle.
The posterior branch (ramus
posterior) pierces the anterior
part of the Obturator externus,
and supplies this muscle; it then
passes behind the Adductor brevis
Fig. 827.— Nerves of the right lower extremity. Front view. OH the frOUt of the AdductOF
THE LUMBAR NERVES 955
magnus, where it divides into numerous muscular branches which are distributed
to the Adductor magnus and the Adductor brevis when the latter does not receive
a branch from the anterior division of the nerve. It usually gives off an articular
filament to the knee-joint.
The articular branch for the knee-joint is sometimes absent; it either perforates
the lower part of the Adductor magnus, or passes through the opening which trans-
mits the femoral artery, and enters the popliteal fossa; it then descends upon the
popliteal artery, as far as the back part of the knee-joint, where it perforates the
oblique popliteal ligament, and is distributed to the synovial membrane. It gives
filaments to the popliteal artery.
The Accessory Obturator Nerve (n. obturatorius accessorius) (Fig. 823) is present
in about 29 per cent, of cases. It is of small size, and arises from the ventral divi-
sions of the third and fourth lumbar nerves. It descends along the medial border
of the Psoas major, crosses the superior ramus of the pubis, and passes under the
Pectineus, where it divides into numerous branches. One of these supplies the
Pectineus, penetrating its deep surface, another is distributed to the hip-joint;
while a third communicates with the anterior branch of the obturator nerve.
Occasionally the accessory obturator nerve is very small and is lost in the capsule
of the hip-joint. When it is absent, the hip-joint receives two branches from the
obturator nerve.
The Femoral Nerve {n. femoralis; anterior crural nerve) (Fig. 827), the largest
branch of the lumbar plexus, arises from the dorsal divisions of the second, third,
and fourth lumbar nerves. It descends through the fibers of the Psoas major,
emerging from the muscle at the lower part of its lateral border, and passes down
between it and the Iliacus, behind the iliac fascia; it then runs beneath the inguinal
ligament, into the thigh, and splits into an anterior and a posterior division. Under
the inguinal ligament, it is separated from the femoral artery by a portion of the
Psoas major.
Within the abdomen the femoral nerve gives off small branches to the Iliacus,
and a branch which is distributed upon the upper part of the femoral artery; the
latter branch may arise in the thigh.
In the thigh the anterior division of the femoral nerve gives off anterior cuta-
neous and muscular branches. The anterior cutaneous branches comprise the
intermediate and medial cutaneous nerves (Fig. 825).
The intermediate cutaneous nerve (ramus cutanevs anterior; middle cutaneous
nerve) pierces the fascia lata (and generally the Sartorius) about 7.5 cm. below
the inguinal ligament, and divides into two branches which descend in immediate
proximity along the forepart of the thigh, to supply the skin as low as the front
of the knee. Here thev communicate with the medial cutaneous nerve and the
infrapatellar branch of the saphenous, to form the patellar plexus. In the upper
part of the thigh the lateral branch of the intermediate cutaneous communicates
with the lumboinguinal branch of the genitofemoral nerve.
The medial cutaneous nerve (ramus cutaneus anterior; internal cutaneous nerve)
passes obliquely across the upper part of the sheath of the femoral artery, and divides
in front, or at the medial side of that vessel, into two branches, an anterior and a
posterior. The anterior branch runs downward on the Sartorius, perforates the
fascia lata at the lower third of the thigh, and divides into two branches: one
supplies the integument as low down as the medial side of the knee; the other
crosses to the lateral side of the patella, communicating in its course w^ith the infra-
patellar branch of the saphenous nerve. The posterior branch descends along the
medial border of the Sartorius muscle to the knee, where it pierces the fascia lata,
communicates with the saphenous nerve, and gives off several cutaneous branches.
It then passes down to supply the integument of the medial side of the leg. Beneath
the fascia lata, at the lower border of the Adductor longus, it joins to form a plexi-
956 NEUROLOGY
form net-work (subsartorial plexus) with branches of the saphenous and obturator
nerves. ^Vhen the communicating branch from the obturator nerve is large and
continued to the integument of the leg, the posterior branch of the medial cutaneous
is small, and terminates in the plexus, occasionally giving off a few cutaneous
filaments. The medial cutaneous nerve, before dividing, gives off a few filaments,
which pierce the fascia lata, to supply the integument of the medial side of the
thigh, accompanying the long saphenous vein. One of these filaments passes
through the saphenous opening; a second becomes subcutaneous about the middle
of the thigh; a third pierces the fascia at its lower third.
Muscular Branches (rami musculares). — The nerve to the Pectineus arises
immediately below the inguinal ligament, and passes behind the femoral sheath to
enter the anterior surface of the muscle; it is often duplicated. The nerve to the
Sartorius arises in common with the intermediate cutaneous.
The posterior division of the femoral nerve gives off the saphenous ners'e, and
muscular and articular branches.
The Saphenous Nerve (n. saphenus; long or internal saphenous nerve) (Fig. 827)
is the largest cutaneous branch of the femoral nerve. It approaches the femoral
artery where this vessel passes beneath the Sartorius, and lies in front of it, behind
the aponeurotic covering of the adductor canal, as far as the opening in the lower
part of the Adductor magnus. Here it quits the artery, and emerges from behind
the lower edge of the aponeurotic covering of the canal; it descends vertically
along the medial side of the knee behind the Sartorius, pierces the fascia lata,
between the tendons of the Sartorius and Gracilis, and becomes subcutaneous.
The nerve then passes along the tibial side of the leg, accompanied by the great
saphenous vein, descends behind the medial border of the tibia, and, at the lower
third of the leg, divides into two branches : one continues its course along the margin
of the tibia, and ends at the ankle; the other passes in front of the ankle, and is
distributed to the skin on the medial side of the foot, as far as the ball of the great
toe, communicating with the medial branch of the superficial peroneal nerve.
Branches. — The saphenous nerve, about the middle of the thigh, gives off a
branch which joins the subsartorial plexus.
At the medial side of the knee it gives off a large infrapatellar branch, which
pierces the Sartorius and fascia lata, and is distributed to the skin in front of the
patella. This nerve commimicates above the knee with the anterior cutaneous
branches of the femoral nerve; below the knee, with other branches of the saphenous;
and, on the lateral side of the joint, with branches of the lateral femoral cutaneous
nerve, forming a plexiform net-work, the plexus patellae. The infrapatellar branch
is occasionally small, and ends by joining the anterior cutaneous branches of the
femoral, which supply its place in front of the knee.
Below the knee, the branches of the saphenous nerve are distributed to the skin
of the front and medial side of the leg, communicating with the cutaneous branches
of the femoral, or with filaments from the obturator nerve.
The muscular branches supply the four parts of the Quadriceps femoris. The
branch to the Rectus femoris enters the upper part of the deep surface of the muscle,
and supplies a filament to the hip-joint. The branch to the Vastus laterahs, of
large size, accompanies the descending branch of the lateral femoral circumfiex
artery to the lower part of the muscle. It gives oft' an articular filament to the
knee-joint. The branch to the Vastus medialis descends lateral to the femoral
vessels in company with the saphenous nerve. It enters the muscle about its middle,
and gives off a filament, which can usually be traced downward, on the surface of
the muscle, to the knee-joint. The branches to the Vastus intermedius, two or
three in number, enter the anterior surface of the muscle about the middle of the
thigh; a filament from one of these descends through the muscle to the Articularis
genu and the knee-joint. The articular branch to the hip-joint is derived from the
nerve to the Rectus femoris.
I
THE SACRAL AXD COCCYGEAL NERVES 957
The articular branches to the knee-joint are three in number. One, a long slender
filament, is derived from the nerve to the Vastus lateralis; it penetrates the capsule
of the joint on its anterior aspect. Another, derived from the nerve to the Vastus
medialis, can usually be traced downward on the surface of this muscle to near the
joint; it then penetrates the muscular fibers, and accompanies the articular branch
of the hi.ijhest genicular artery, pierces the medial side of the articular capsule,
and supplies the synovial membrane. The third branch is derived from the nerve
to the Vastus intermedius.
The Sacral and Coccygeal Nerves (Nn. Sacrales et Coccygeus).
The anterior divisions of the sacral and coccygeal nerves (rami antcriores) form
the sacral and pudendal plexuses. The anterior divisions of the upper four sacral
nerves enter the pelvis through the anterior sacral foramina, that of the fifth
between the sacrum and coccyx, while that of the coccygeal nerve curves forward
below the rudimentary transverse process of the first piece of the coccyx. The
first and second sacral nerves are large; the third, fourth, and fifth diminish pro-
gressively from above downward. Each receives a gray ramus communicans
from the corresponding ganglion of the sympathetic trunk, while from the third
and frequently from the second and the fourth sacral nerves, a white ramus com-
municans is given to the pelvic plexuses of the sympathetic.
The Sacral Plexus (plexus sncralis) (Fig. 828).— The sacral plexus is formed by
the lumbosacral trunk, the anterior division of the first, and portions of the anterior
divisions of the second and third sacral nerves.
The lumbosacral trunk comprises the whole of the anterior division of the fifth
and a part of that of the fourth lumbar nerve; it appears at the medial margin of
the Psoas major and runs downward over the pelvic brim to join the first sacral
nerve. The anterior division of the third sacral nerve divides into an upper and a
lower branch, the former entering the sacral and the latter the pudendal plexus.
The nerves forming the sacral plexus converge toward the lower part of the greater
sciatic foramen, and unite to form a flattened band, from the anterior and posterior
surfaces of which several branches arise. The band itself is continued as the sciatic
nerve, which splits on the back of the thigh into the tibial and common peroneal
nerves; these two nerves sometimes arise separately from the plexus, and in all
cases their independence can be shown by dissection.
Relations. — The sacral plexus hes on the back of the pelvis between the Piriformis and the
pelvic fascia (Fig. S29) ; in front of it are the hypogastric vessels, the ureter and the sigmoid colon.
The superior gluteal vessels run between the lumbosacral trunk and the first sacral nerve, and the
inferior gluteal vessels between the second and third sacral nerves.
All the nerves entering the plexus, with the exception of the third sacral, spht into ventral
and dorsal divisions, and the nerves arising from these are as follows:
Ventral divisions. Dorsal divisions.
Nerve to Quadratus femoris 1 4. c t 1 c
and Gemellus inferior / ' '
5 L, 1, 2 S.
Xerve to Obturator internus
and Gemellus superior
Nerve to Piriformis (1) 2 S.
Superior gluteal 4, 5 L, 1 S.
Inferior gluteal • 5 L, 1, 2 S.
Posterior femoral cutaneous 2, 3 S . . . 1, 2 S.
c, . ,. / Tibial . . . 4, 5 L, 1, 2, 3 S.
bciatic I Common peroneal 4, 5 L, 1. 2 S.
The Nerve to the Quadratus Femoris and Gemellus Inferior arises from the ventral
divisions of the fourth and fifth lumbar and first sacral nerves: it leaves the pelvis
958
NEUROLOGY
through the greater sciatic foramen, below the Piriformis, and runs down in front of
the sciatic nerve, the Gemelli, and the tendon of the Obturator internus, and enters
the anterior surfaces of the muscles; it gives an articular branch to the hip-joint.
Superior gluteal
Inferior gluteal
To Piriformis
ith Lumbar
5th Lumbar
1st Sacral
. Commnn
I peroneal
Sciatic i
\ Tibial
To Quadratus femoris and
Inferior gemellus
To Obturator internus and
Superior gemellus
Post. fern, cutaneous
Perforating cutaneous
2nd Sacral
Visceral br.
Zrd Sacral
Visceral br.
Uh Sacral
Visceral br.
5th Sacral
Coccygeal
Pudendal
To Levator ani, Coccygeus and
Sphincter ani externus
Fia. 828. — Plan of sacral and pudendal plexuses.
The Nerve to the Obturator Internus and Gemellus Superior arises from the ventral
divisions of the fifth lumbar and first and second sacral nerves. It leaves the pelvis
through the greater sciatic foramen below the Piriformis, and gives off the branch
to the Gemellus superior, which enters the upper part of the posterior surface of
the muscle. It then crosses the ischial spine, reenters the pelvis through the
lesser sciatic foramen, and pierces the pelvic surface of the Obturator internus.
THE SACRAL AND COCCYGEAL NERVES
959
The Nerve to the Piriformis arises from the dorsal division of the second sacral
nerve, or the dorsal divisions of the first and second sacral nerves, and enters
the anterior surface of the muscle; this nerve may he double.
Sympathetic
trunk
Fig. 829. — Dissection of side wall of pelvis showing sacral and pudendal plexuses. ' (Testut.)
The Superior Gluteal Nerve (n. glutcpus superior) arises from the dorsal division.s
of the fourth and fiftli lumbar and first sacral nerves: it leaves the pelvis through
the greater sciatic foramen above the Piriformis, accompanied by the superior
gluteal vessels, and divides into a superior and an inferior branch. The superior
branch accompanies the upper branch of the deep division of the superior gluteal
artery and ends in the Gluttvus minimus. The inferior branch runs with the lower
branch of the deep division of the superior gluteal artery across the Glutaeus
minimus; it gives filaments to the Gluta?i medius and minimus, and ends in the
Tensor fasciae latse.
The Inferior Gluteal Nerve (w. glutosus inferior) arises from the dorsal divisions
of the fifth lumbar and first and second sacral nerves : it leaves the pelvis through
the greater sciatic foramen, below the Piriformis, and divides into branches which
enter the deep surface of the Glutteus maximus.
The Posterior Femoral Cutaneous Nerve (/i. cutaneiis femoralis posterior; small
sciatic nerve) is distributed to the skin of the perineum and posterior surface of
the thigh and leg. It arises partly from the dorsal divisions of the first and second,
and from the ventral divisions of the second and third sacral nerves, and issues from
960 NEUROLOGY
the pelvis through the greater sciatic foramen below the Piriformis. It then descends
beneath the Glutseus maximus with the inferior gluteal artery, and runs down the
back of the thigh beneath the fascia lata, and over the long head of the Biceps
femoris to the back of the knee; here it pierces the deep fascia and accompanies
the small saphenous vein to about the middle of the back of the leg, its terminal
twigs communicating with the sural nerve.
Its branches are all cutaneous, and are distributed to the gluteal region, the peri-
neum, and the back of the thigh and leg.
The gluteal branches {nn. clwiium inferiores) , three or four in number, turn upward
around the lower border of the Gluteus maximus, and supply the skin covering
the lower and lateral part of that muscle.
The perineal branches (rami perineales) are distributed to the skin at the upper
and medial side of the thigh. One long perineal branch, inferior pudendal {Io7ig
scrotal nerve) , curves forward below and in front of the ischial tuberosity, pierces
the fascia lata, and runs forward beneath the superficial fascia of the perineum to
the skin of the scrotum in the male, and of the labium majus in the female. It
communicates with the inferior hemorrhoidal and posterior scrotal nerves.
The branches to the back of the thigh and leg consist of numerous filaments derived
from both sides of the nerve, and distributed to the skin covering the back and
medial side of the thigh, the popliteal fossa, and the upper part of the back of the
leg (Fig. 830).
The Sciatic {n. ischiadicus; great sciatic nerve) (Fig. 832) supplies nearly the whole
of the skin of the leg, the muscles of the back of the thigh, and those of the leg
and foot. It is the largest nerve in the body, measuring 2 cm. in breadth, and is
the continuation of the flattened band of the sacral plexus. It passes out of the
pelvis through the greater sciatic foramen, below the Piriformis muscle. It descends
between the greater trochanter of the femur and the tuberosity of the ischium, and
along the back of the thigh to about its lower third, where it divides into two large
branches, the tibial and common peroneal nerves. This division may take place
at any point between the sacral plexus and the lower third of the thigh. When it
occurs at the plexus, the common peroneal nerve usually pierces the Piriformis.
In the upper part of its course the nerve rests upon the posterior surface of the
ischium, the nerve to the Quadratus femoris, the Obturator internus and Gemelli,
and the Quadratus femoris; it is accompanied by the posterior femoral cutaneous
nerve and the inferior gluteal artery, and is covered by the Gluti^us maximus.
Lower down, it lies upon the Adductor magnus, and is crossed obliquely by the
long head of the Biceps femoris.
The nerve gives off articular and muscular branches.
The articular branches (rami articulares) arise from the upper part of the nerve
and supply the hip-joint, perforating the posterior part of its capsule; they are
sometimes derived from the sacral plexus.
The muscular branches (rami musculares) are distributed to the Biceps femoris,
Semitendinosus, Semimembranosus, and Adductor magnus. The nerve to the short
head of the Biceps femoris comes from the common peroneal part of the sciatic,
while the other muscular branches arise from the tibial portion, as may be seen in
those cases where there is a high division of the sciatic nerve.
The Tibial Nerve (n. tibialis; internal popliteal nerve) (Fig. 832) the larger of the
two terminal branches of the sciatic, arises from the anterior branches of the
fourth and fifth lumbar and first, second, and third sacral nerves. It descends
along the back of the thigh and through the middle of the popliteal fossa, to the lower
part of the Popliteus muscle, where it passes with the popliteal artery beneath the
arch of the Soleus. It then runs along the back of the leg with the posterior
tibial vessels to the interval between the medial malleolus and the heel, where it
divides beneath the laciniate ligament into the medial and lateral plantar nerves.
THE SACRAL AND COCCYGEAL NERVES
961
In the thigh it is overlapped by the hamstring muscles above, and then becomes
more superficial, and lies lateral to, and some distance from, the popliteal vessels;
°^^y
:>
N i I
Tibial
S.1.2.
Fig. 830. — Cutaneous nerves of right lower
extremity. Posterior view.
61
Fio. 831. — Diagram of the segmental distribution of the
cutaneous nerves of the right lower extremity. Posterior
view.
962
NEUROLOGY
i.UiT,l WJ I'
Superior
gluteal ' v ><■
Pvdendal .
Nerve to
obturator intemus
Post. fern. _
cutaneous
Perineal _
branch
^
Great ci\
' Track,
^FE-Mi'/I
Descending
cutanecms
Tibial
Med. sural
cutaneous
Tibial
li
.^
Common
jKroneal
Peroneal
anastomotic
Medial ^}
calcaneal
Fig. 832. — Nerves of the right lower extremity
Posterior view.
opposite the knee-joint, it is in close
relation with these vessels, and crosses
to the medial side of the artery. In the
leg it is covered in the upper part of
its course by the muscles of the calf;
lower down by the skin, the superficial
and deep fasciae. It is placed on the
deep muscles, and lies at first to the
medial side of the posterior tibial
artery, but soon crosses that vessel and
descends on its lateral side as far as
the ankle. In the lower third of the
leg it- runs parallel with the medial
margin of the tendo calcaneus.
The branches of this nerve are : artic-
ular, muscular, medial sural cutaneous,
medial calcaneal, medial and lateral
plantar.
Articular branches (rami articular es) ,
usually three in number, supply the
knee-joint; two of these accompany
the superior and inferior medial genic-
ular arteries; and a third, the middle
genicular artery. Just above the bi-
furcation of the nerve an articular
branch is given off to the ankle-joint.
Muscular branches {rami musculares) ,
four or five in number, arise from the
nerve as it lies between the two heads
of the Gastrocnemius muscle; they
supply that muscle, and the Plantaris,
Soleus, and Popliteus. The branch
for the Popliteus turns around the lower
border and is distributed to the deep
surface of the muscle. Lower down,
muscular branches arise separately or
by a common trunk and supply the
Soleus, Tibialis posterior. Flexor digi-
torum longus, and Flexor hallucis
longus; the branch to the last muscle
accompanies the peroneal artery; that
to the Soleus enters the deep surface
of the muscle.
The medial sural cutaneous nerve (n.
cutaneus surw medialis; n. communi-
cans tibialis) descends between the
two heads of the Gastrocnemius, and,
about the middle of the back of the
leg, pierces the deep fascia, and unites
with the anastomotic ramus of the
common peroneal to form the sural
nerve (Fig. 830).
• N. B. — In this diagram the medial sura cutaneous and peroneal anastomotic are not in their normal position.
They have been displaced by the removal of the superficial muscles.
THE SACRAL AND COCCYGEAL NERVES 963
The sural nerve {n. suralis; short saphenous nerve), formed by the junction of the
medial sural cutaneous with the peroneal anastomotic branch, passes downward
near the lateral margin of the tendo calcaneus, lying close to the small saphenous
vein, to the interval between the lateral malleolus and the calcaneus. It runs
forward below the lateral malleolus, and is continued as the lateral dorsal cutaneous
nerve along the lateral side of the foot and little toe, communicating on the dorsum
of the foot with the intermediate dorsal cutaneous nerve, a branch of the superficial
peroneal. In the leg, its branches communicate with those of the posterior femoral
cutaneous.
The medial calcaneal branches {rami calcanei mediales; internal calcaneal branches)
perforate the laciniate ligament, and supply the skin of the heel and medial side
of the sole of the foot.
The medial plantar nerve {n. plantaris medialis; internal plantar nerve) (Fig. 833),
the larger of the two terminal divisions of the tibial nerve, accompanies the medial
plantar artery. From its origin under the laciniate ligament it passes under cover
of the Abductor hallucis, and, appearing between this muscle and the Flexor digi-
torum brevis, gives off a proper digital plantar nerve and finally divides opposite
the bases of the metatarsal bones into three common digital plantar nerves.
Branches. — The branches of the medial plantar nerve are: (1) cutaneous,
(2) muscular, (3) articular, (4) a proper digital nerve to the medial side of the great
toe, and (5) three common digital nerves.
The cutaneous branches pierce the plantar aponeurosis between the Abductor
hallucis and the Flexor digitorum brevis and are distributed to the skin of the sole
of the foot.
The muscular branches supply the Abductor hallucis, the Flexor digitorum brevis,
the Flexor hallucis brevis, and the first Lumbricalis; those for the Abductor hallucis
and Flexor digitorum brevis arise from the trunk of the nerve near its origin and
enter the deep surfaces of the muscles; the branch of the Flexor hallucis brevis
springs from the proper digital nerve to the medial side of the great toe, and that
for the first Lumbricalis from the first common digital nerve.
The articular branches supply the articulations of the tarsus and metatarsus.
The proper digital nerve of the great toe (nn. digitales plantares proprii; plantar
digital branches) supplies the Flexor hallucis brevis and the skin on the medial side
of the great toe.
The three common digital nerves (nn. digitales plantares communes) pass between
the divisions of the plantar aponeurosis, and each splits into two proper digital
nerves — those of the first common digital nerve supply the adjacent sides of the
great and second toes; those of the second, the adjacent sides of the second and
third toes; and those of the third, the adjacent sides of the third and fourth toes.
The third common digital nerve receives a communicating branch from the lateral
plantar nerve; the first gives a twig to the first Lumbricalis. Each proper digital
nerve gives off cutaneous and articular filaments; and opposite the last phalanx
sends upward a dorsal branch, which supplies the structures around the nail,
the continuation of the nerve being distributed to the ball of the toe. It will be
observed that these digital nerves are similar in their distribution to those of the
median nerve in the hand.
The Lateral Plantar Nerve (n. plantaris lateralis; external plantar nerve) (Fig.
833) supplies the skin of the fifth toe and lateral half of the fourth, as well as most
of the deep muscles, its distribution being similar to that of the ulnar nerve in the
hand. It passes obliquely forward with the lateral plantar artery to the lateral
side of the foot, lying between the Flexor digitorum brevis and Quadratus plantae;
and, in the interval between the former muscle and the Abductor digiti quinti,
divides into a superficial and a deep branch. Before its division, it supplies the
Quadratus plantee and Abductor digiti quinti.
964
NEUROLOGY
*
The superficial branch (ramjis superficialis) splits into a proper and a common
digital nerve; the proper digital nerve supplies the lateral side of the little toe,
the Flexor digiti quinti brevis, and the two
Interossei of the fourth intermetatarsal space;
the common digital nerve communicates with
the third common digital branch of the medial
plantar nerve and divides into two proper
If Ai^i A\^v--w-T--Tp7™Bit ^inritar digital ucrvcs which supply the adjoining
JiedJat A\\ auADRA'Ti;s||^ plantar o » ^i » ^, , nelY .
plantar k\\^\KKd''^f-/ I I Sides 01 the lourth and farth toes.
Lateral
plantar
Deep
hraivch
Saphenous
L. 3. U.
Fia. 833. — The plantar nerves.
Fig. 834. — Diagram of the segmental distribution of the
cutaneous nerves of the sole of the foot.
The deep branch {ramus profundus; museitlar branch) accompanies the lateral
plantar artery on the deep surface of the tendons of the Flexor muscles and the
Adductor hallucis, and supplies all the Interossei (except those in the fourth
metatarsal space), the second, third, and fourth Lumbricales, and the Adductor
hallucis.
The Common Peroneal Nerve (n. peroncrus communis: external popliteal nerve;
peroneal nerve) (Fig. 832), about one-half the size of the tibial, is derived from the
dorsal branches of the fourth and fifth lumbar and the first and second sacral
nerves. It descends obliquely along the lateral side of the popliteal fossa to the head
of the fibula, close to the medial margin of the Biceps femoris muscle. It lies
between the tendon of the Biceps femoris and lateral head of the Gastrocnemius
muscle, winds around the neck of the fibula, between the Peromeus longus and the
bone, and divides beneath the muscle into the superficial and deep peroneal nerves.
Previous to its division it gives off articular and lateral sural cutaneous nerves.
The articular branches (rami articidares) are three in number; two of these accom-
pany the superior and inferior lateral genicular arteries to the knee; the upper one
occasionally arises from the trunk of the sciatic .lerve. The third {recurrent)
articular nerve is given off at the point of division of the common peroneal nerve;
it ascends Avith the anterior recurrent tibial artery through the Tibialis anterior to
the front of the knee.
The lateral sural cutaneous nerve {n. cutaneus surer lateralis; lateral cutaneous
branch) supplies the skin on the posterior and lateral surfaces of the leg; one
branch, the peroneal anastomotic («. communicar.s fibularis) , arises near the head
of the fibula, crosses the lateral head of the Gastrocnemius to the middle of the
THE SACRAL AND COCCYGEAL NERVES
965
; PATELLAR BRANCH OF
\ SAPHENOUS NERVE
COMMON PERC
NEAL NERVE
SUPERFICIAL
PERONEAL NERVE
-SAPHENOUS NERVE
m
Vm
3eEP PERONEAL
NERVE
CUTANEOUS BRANCH I
OF SUPERFICIAL
PERONEAL J
leg, and joins with the medial sural cutaneous to form the sural nerve. The
peroneal anastomotic is occasionally continued down as a separate branch as far
as the heel.
The Deep Peroneal Nerve {n. lieronoeus yrofumlus; anterior tibial nerve) (Fig.
827) begins at the bifurcation of the common peroneal nerve, between the fibula
and upper part of the Perona&us
longus, passes obliquely forward
beneath the Extensor digitorum
longus to the front of the inter-
osseous membrane, and comes
into relation with the anterior
tibial artery above the middle
of the leg; it then descends with
the artery to the front of the
ankle-joint, where it divides into
a lateral and a medial terminal
branch. It lies at first on the
lateral side of the anterior tibial
artery, then in front of it, and
again on its lateral side at the
ankle-joint.
In the leg, the deep peroneal
nerve supplies muscular branches
to the Tibialis anterior, Extensor
digitorum longus, Perona?us ter-
tius, and Extensor hallucis pro-
p ius, and an articular branch to
the ankle-joint.
The lateral terminal branch
{external or tarsal branch) passes
across the tarsus, beneath the
i^iXtensor digitorum brevis, and, \fp,\
having become enlarged like the
dorsal interosseous nerve at the
wrist, supplies the Extensor digi-
torumbrevis. From the enlarge-
ment three minute interosseous
branches are given off, which sup-
ply the tarsal joints and the
metatarsophalangeal joints of
the second, third, and fourth
toes. The first of these sends a
filament to the second Inter-
osseus dorsalis muscle.
The medial terminal branch
(internal branch) accompanies
the dorsalis pedis artery along
the dorsum of the foot, and, at
the first interosseous space, di- fiq.
vides into two dorsal digital
nerves (nn. digitales dorsales hallucis lateralis et digiti secundi medialis) which supply
the adjacent sides of the great and second toes, communicating with the medial
dorsal cutaneous branch of the superficial peroneal nerve. Before it divides it
gives off to the first space an interosseous branch which supplies the metatarso-
.LATEPAL BRANCH OF
DEEP PERONEAL
-MEDIAL TERMINAL
BRANCH
-DIGITORUM
SURAL NCRVE
Ic
BRANCHES OF
SUPERFICIAL PERONEAL
835. — Deep nerves of the front of the leg.
(Testut.
966
NEUROLOGY
MEOrAL DORSAL CUTA-
NEOUS 6RANChl
OF SUPERFICIAL DEEP
PERONEAL PERONEAL
INTERMEDIAL DORSAL
CUTANEOUS B
OF SUPERFICIAL
PERONEAL
SAPHENOUS VEIN
HENOUS
CRVE
LATERAL BRANCH
OF DEEP PERONEAL
phalangeal joint of the great toe and sends a filament to the first Interosseous
dorsalis muscle.
The Superficial Peroneal Nerve (n. peronopus superficiaUs; musculocutaneous nerve)
(Figs. 827, 835) supplies the Peronei longus and brevis and the skin over the greater
part of the dorsum of the foot. It passes forward between the Perona?i and the
Extensor digitorum longus, pierces the deep fascia at the lower third of the leg, and
divides into a medial and an inter-
mediate dorsal cutaneous nerve. In
its course between the muscles, the
nerve gives off muscular branches
to the Perona?i longus and brevis,
and cutaneous filaments to the
integument of the lower part of
the leg.
The medial dorsal cutaneous
nerve {n. cutaneus dursalis medialis;
internal dorsal cutaneous branch)
passes in front of the ankle-joint,
and divides into two dorsal digital
branches, one of which supplies
the medial side of the great toe,
the other, the adjacent side of the
second and third toes. It also
supplies the integument of the
medial side of the foot and ankle,
and communicates with the saphe-
nous nerve, and with the deep
peroneal nerve (Fig. 825).
The intermediate dorsal cuta-
neous nerve {n. cut a ne us dorsalis
intermedius; external dorsal cuta-
neous branch), the smaller, passes
along the lateral part of the dor-
sum of the foot, and divides into
dorsal digital branches, which sup-
ply the contiguous sides of the
third and fourth, and of the
fourth and fifth toes. It also
supplies the skin of the lateral
side of the foot and ankle, and communicates with the sural nerve (Fig. 825).
The branches of the superficial peroneal nerve supply the skin of the dorsal
surfaces of all the toes excepting the lateral side of the little toe, and the adjoining
sides of the great and second toes, the former being supplied by the lateral dorsal
cutaneous nerve from the sural nerve, and the latter by the medial branch of the
deep peroneal nerve. Frequently some of the lateral branches of the superficial
"peroneal are absent, and their places are then taken by branches of the sural
nerve.
The Pudendal Plexus {plexus pudendus) (Fig. 828).— The pudendal plexus is
not sharply marked off from the sacral plexus, and as a consequence some of the
branches which spring from it may arise in conjunction with those of the sacral
plexus. It lies on the posterior wall of the pelvis, and is usually formed by branches
from the anterior divisions of the second and third sacral nerves, the whole of the
anterior divisions of the fourth and fifth sacral nerves, and the coccygeal nerve.
TAR NERVE
BRANCHES OF INTERNAL
PLANTAR NERVE
Fig. 836. — Nerves of the dorsum of the foot. (Testut.)
THE SACRAL AND COCCYGEAL NERVES
967
It gives off the following branches:
Perforating cutaneous
Pudendal . . . .
Visceral . . . .
Muscular . . , .
Anococcygeal
2, 3S.
2, 3, 4 S.
3, 4 S.
4S.
4, 5 S. and Cocc.
LATERAL FEMORAL
GENITO-
FEMORA
FIFTH
LUMBAR
SYMPATHETIC
.•;.'i\ " TRUNK
^."'"\ LUMBO-SACRAL
3
EXTERNAL SPER-
MATIC BRANCH OF
GENITO-CRURAL
LUMBO-INGUINAL
BRANCH OF
GENITO-CRURAL
CORD
SUPERIOR
^''" GLUTEAL
_^^ RAMUS
COMMUNICANS
VISCERAL
BRANCHES
NERVE TO
LEVATOR ANI
...HEMORRHOIDAL BRANCH
OF PUDIC
PUDENDAL
PERINEAL
POST. FEMORAL
EXTERNAL SUPER-
FICIAL PERINEAL
NTERNAL SUPER-
FICIAL PERINEAL
LEFT DORSAL-
DORSAL NERVE...
OF PENIS
NERVE TO BULB
INFERIOR
PUDENDAL
Fig. S37. — Sacral plexus of the right side. (Testut).
The Perforating Cutaneous Nerve (n. chinhirn inferior medialis) usually arises from
the posterior surface of the second and third sacral nerves. It pierces the lower
part of the sacrotuberous ligament, and winding around the inferior border of the
Gluta^us maximus supplies the skin covering the medial and lower parts of that
muscle.
The perforating cutaneous nerv^e may arise from the pudendal or it may be absent; in the
latter case its place maj^ be taken by a branch from the posterior femoral cutaneous nerve or by
a branch from the third and fourth, or fourth and fifth, sacral nerves.
The Pudendal Nerve {n. jnidendus; internal p^tdic nerve) derives its fibers from the
ventral branches of the second, third, and fourth sacral nerves. It passes between
the Piriformis and Coccygeus muscles and leaves the pelvis through the lower part
of the greater sciatic foramen. It then crosses the spine of the ischium, and
reenters the pelvis through the lesser sciatic foramen. It accompanies the internal
pudendal vessels upward and forward along the lateral wall of the ischiorectal
968 NEUROLOGY
fossa, being contained in a sheath of the obturator fascia termed Alcock's canal,
and divides into two terminal branches, viz., the perineal nerve, and the dorsal nerve
of the penis or clitoris. Before its division it gives off the inferior hemorrhoidal nerve.
The inferior hemorrhoidal nerve (n. hcpmorrhoidaUs inferior) occasionally arises
directly from the sacral plexus; it crosses the ischiorectal fossa, with the inferior
hemorrhoidal vessels, toward the anal canal and the lower end of the rectum,
and is distributed to the Sphincter ani externus and to the integument around the
anus. Branches of this nerve communicate with the perineal branch of the posterior
femoral cutaneous and with the posterior scrotal nerves at the forepart of
the perineum.
The perineal nerve (n. perinei), the inferior and larger of the two terminal branches
of the pudendal, is situated below the internal pudendal artery. It accompanies
the perineal artery and divides into posterior scrotal (or labial) and muscular branches.
The posterior scrotal (or labial) branches {nn. scrotales (or labiales) posteriores;
superficial peroneal nerves) are two in number, medial and lateral. They pierce
the fascia of the urogenital diaphragm, and run forward along the lateral part of
the urethral triangle in company with the posterior scrotal branches of the perineal
artery; they are distributed to the skin of the scrotum and communicate with the
perineal branch of the posterior femoral cutaneous nerve. These nerves supply the
labium majus in the female.
The muscular branches are distributed to the Transversus perinrei superficialis.
Bulbocavernous, Ischiocavernosus, and Constrictor urethnr. A branch, the
nerve to the bulb, given off from the nerve to the Bulbocavernosus, pierces this
muscle, and supplies the corpus cavernosum urethrae, ending in the mucous
membrane of the urethra.
The dorsal nerve of the penis {n. dorsalis penis) is the deepest division of the puden-
dal nerve; it accompanies the internal pudendal artery along the ramus of the
ischium; it then runs forward along the margin of the inferior ramus of the pubis,
between the superior and inferior layers of the fascia of the urogenital diaphragm.
Piercing the inferior layer it gives a branch to the corpus cavernosum penis, and
passes forward, in company with the dorsal aytery of the penis, between the layers
of the suspensory ligament, on to the dorsum of the penis, and ends on the glans
penis. In the female this nerve is very small, and supplies the clitoris {ii. dorsalis
clitoridis).
The Visceral Branches arise from the third and fourth, and sometimes from the
second, sacral nerves, and are distributed to the bladder and rectum and, in the
female, to the vagina ; they communicate with the pelvic plexuses of the sympathetic.
The Muscular Branches are derived from the fourth sacral, and supply the Levator
ani, Coccygeus, and Sphincter ani externus. The branches to the Levator ani
and Coccygeus enter their pelvic surfaces; that to the Sphincter ani externus
(perineal branch) reaches the ischiorectal fossa by piercing the Coccygeus or by
passing between it and the Levator ani. Cutaneous filaments from this branch
supply the skin between the anus and the coccyx.
Anococcygeal Nerves (nji. anococcygei). — The fifth sacral nerve receives a com-
municating filament from the fourth, and unites with the coccygeal nerve to form
the coccygeal plexus. From this plexus the anococcygeal nerves take origin; they
consist of a few fine filaments which pierce the sacrotuberous ligament to supply
the skin in the region of the coccyx.
THE SYMPATHETIC NERVOUS SYSTEM.
The sympathetic nervous system (Fig. 838) innervates all the smooth muscles and
the various glands of the body, and the striated muscle of the heart. The efferent
.sjinpathetic fibers which leave the central nervous system in comiection with
THE SYMPATHETIC NERVOUS SYSTEM
969
certain of the cranial and spinal nerves all end in sympathetic ganglia and are
known as preganglionic fibers. From these ganglia postganglionic fibers arise and
Maxillary nerve
Ciliary gangli(m
Sphenopalatine ganglion
Superior cervicai. ganglion of sympathetic
Cervical plexus
Brachial plexus
Greater splanchnic
nerve
Lesser splanchnic
nerve
Lurnbar plexus
Sacral plexus
Pharyngeal plexus
Middle cervical ganglion of
sympathetic
Inferior cervical ganglion of
sympathetic
Recurrent nerve
Bronchial plexus
- Cardiac plexus
(Esophageal plexus
Coronary plexuses
Left vagiis nerve
Gastric plexus
C celiac plexus
Superior mesenteric
plexus
Aortic plexus
Inferior mesenteric
plexus
Hypogastric plexus
Pelvic plexus
Bladder
Vesical plexus
Fig 838. — The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses.
(After Schwalbe.)
conduct impulses to the different organs. In addition, afferent or ssnsory fibers
^connect many of these structures "with the central nervous system.
970 NEUROLOGY
The peripheral portion of the sympathetic nervous system is characterized by
the presence of numerous gangha and comphcated plexuses. These ganglia are
connected with the central nervous system by three groups of SATiipathetic efferent
or preganglionic fibers, i. e., the cranial, the thoracolumbar, and the sacral. These
outflows of sjTnpathetic fibers are separated by intervals where no connections
exist. The cranial and sacral SATnpathetics are often grouped together owing to
the resemblance between the reactions produced by stimulating them and by the
effects of certain drugs. Acetyl-choline, for example, when injected intravenously
in very small doses, produces the same effect as the stimulation of the cranial or
sacral sympathetics, while the introduction of adrenalin produces the same effect
as the stimulation of the thoracolumbar s^-mpathetics. ]Much of our present
knowledge of the s^inpathetic ner\'ous system has been acquired through the appli-
cation of various drugs, especially nicotine which paralyzes the connections or
synapses between the preganglionic and postganglionic fibers of the s^^npathetic
nerves. When it is injected into the general circidation all such s\Tiapses are
paralyzed ; when it is applied locally on a ganglion only the s^^lapses occurring in
that particular ganglion are paralyzed.
Langley,^ who has contributed greatly to our knowledge, adopted a terminology
somewhat dift'erent from that used here and still different from that used by the
pharmacologists. This has led to considerable confusion, as shoA^ii by the arrange-
ment of the terms in the following columns. Gaskell has used the term involuntary
nervous svstem.-
Gray.
Langley.
Meyer and Gottlieb.'
Sympathetic nervous system.
Autonomic nervous system.
Vegetative nervous system.
Cranio-sacral sympathetics.
Parasy mpat hetics .
Autonomic.
(
Oculomotor sympathetics.
Tectal autonomics.
Cranial autonomics.
»
Facial sympathetics.
1
, '
GlossopharjTigeal sympathetics.
f Bulbar autonomics.
j
Vagal sympathetics.
I
)
Sacral sympathetics.
Sacral autonomics.
Sacral autonomics.
Thoracolumbar sympathetics.
Sympathetic.
Sympathetic.
)
Thoracic autonomic.
Enteric.
Enteric.
Enteric.
THE CRANIAL SYMPATHETICS.
The cranial sympathetics include s\-mpathetic efferent fibers in the oculomotor,
facial, glossophar^Tigeal and vagus nerves, as well as sympathetic afferent in the
last three ner\-es.
The Sympathetic Efferent Fibers of the Oculomotor Nerve probably arise from cells
in the anterior part of the oculomotor nucleus which is located in the tegmentum
of the mid-brain. These preganglionic fibers run mth the third nerve into the orbit
and pass to the ciliary ganglion where they terminate by forming s^^lapses wdth
sympathetic motor neurons whose axons, postganglionic fibers, proceed as the short
ciliary nerves to the eyeball. Here they supply motor fibers to the Ciliaris muscle
and the Sphincter pupillse muscle. So far as kno\Mi there are no sympathetic
afferent fibers connected with the nerve.
The Sympathetic Efferent Fibers of the Facial Nerve are supposed to arise from the
small cells of the facial nucleus. According to some authors tlie fibers to the sali-
vary glands arise from a special nucleus, the superior salivatory nucleus, consisting
of cells scattered in the reticular formation, dorso-medial to the facial nucleus.
These preganglionic fibers are distributed partly through the chorda tj-mpani and
1 Schafer. Textbook of Physiology, 1900.
2 Gaskell, W. H., The Involuntary Nervous System, London, 1916.
• Die Experimentelle Pharmakologie, 1910.
THE CRANIAL SYMPATHETICS
971
lingual nerves to the submaxillary ganglion where they terminate about the cell
bodies of neurons whose axons as postganglionic fibers conduct secretory and vaso-
Midbrain
Medulla
Eye
Lacrimal gland
\jlJ C'^^^ Submaxillary gland
c-ff^ Sublingual gland
Otic ^<^A'
/O) Vj^^ Mucous mem,.. mouth
^^ ~~~~~-~-r<'<^>i^ Parotid gland
Heart
Larynx
Trachea
Bronchi
Esophagus
Stomach
Bloodves, of abd.
Liver and dttcts
Pancreas ,
Adrenal
Small intestine
Large intestine
Rectum
Kidney
Bladder
Sexual organs
External genitalia
Fig. 839. — Diagram of efferent sympathetic nervous system. Blue, cranial and sacral outflow. Red, thoraco-
humeral outflow. , Postganglionic fibers to spinal and cranial nerves to supply vasomotors to head, trunk and
limbs, motor fibers to smooth muscles of skin and fibers to sweat glands. (Modified after Meyer and Gottlieb.)
972
NEUROLOGY
dilator impulses to the submaxillary and sublingual glands. Other preganglionic
fibers of the facial nerve pass via the great superficial petrosal nerve to the spheno-
palatine ganglion where they form synapses with neurons whose postganglionic
fibers are distributed with the superior maxillary nerve as vasodilator and secretory
fibers to the mucous membrane of the nose, soft palate, tonsils, u\Tila, roof of the
mouth, upper lips and gums, parotid and orbital glands.
There are supposed to be a few sNTnpathetic afferent fibers connected with the
facial nerve, whose cell bodies lie in the geniculate ganglion, but very little is known
about them.
Short ciliary nerve to ciliary muscle
Ciliary ganglion
Midbrain
Medulla
Short ciliary nerve to
Sphincter pupillce
I. TJioracic ganglion
Sympathetic efferent {preganglionic) fibers
Fig. 840. — Sympathetic connections of the ciliarj- and superior cervical ganglia.
The Sympathetic Afferent Fibers of the Glossopharyngeal Nerve are supposed to arise
either in the dorsal nucleus (nucleus ala cinerea) or in a distinct nucleus, the inferior
salivatory nucleus, situated near the dorsal nucleus. These preganglionic fibers
pass into the t>'mpanic branch of the glossophar^^lgeal and then with the small
superficial jjetrosal nerve to the otic ganglion. Postganglionic fibers, vasodilator
and secretory fibers, are distributed to the parotid gland, to the mucous membrane
and its glands on the tongue, the floor of the mouth, and the lower gums.
S3nnpathetic Afferent Fibers, whose cells of origin lie in the superior or inferior
ganglion of the trunk, are supposed to terminate in the dorsal nucleus. Very little
is knoAAii of the peripheral distribution of these fibers.
The Sympathetic Efferent Fibers of the Vagus Nerve are supposed to arise in the
dorsal nucleus (nucleus ala cinerea). These preganglionic fibers are all supposed to
end in sjTnpathetic ganglia situated in or near the organs supplied by the vagus s\Tn-
THE SACRAL SYMPATHETICS
973
pathetics. The inhibitory fibers to the heart probably terminate in the small ganglia
of the heart wall especially the atrium, from which inhibitory postganglionic fibers
are distributed to the musculature. The preganglionic motor fibers to the esophagus,
the stomach, the small intestine, and the greater part of the large intestine are
supposed to terminate in the plexuses of Auerbach, from which postganglionic
fibers are distributed to the smooth muscles of these organs. Other fibers i)ass to
the smooth muscles of the bronchial tree and to the gall-bladder and its ducts.
In addition the vagus is believed to contain secretory fibers to the stomach and
pancreas. It probably contains many other efferent fibers than those enumerated
above.
Greater superior petrosal
Sphenopalatine ganglion
Lacrimal
gland
Fig. S41. — Sympathetic connections of the sphenopalatine and superior cervical ganglia.
Sympathetic Afferent Fibers of the Vagus, whose cells of origin lie in the jugular
ganglion or the ganglion nodosmn, probably terminate in the dorsal nucleus of the
medulla oblongata or according to some authors in the nucleus of the tractus
solitarius. Peripherally the fibers are supposed to be distributed to the various
organs supplied by the sympathetic eft'erent fibers.
THE SACRAL SYMPATHETICS.
The Sacral Sympathetic Efferent Fibers leave the spinal cord with the anterior roots
of the secontl, third and fourth sacral nerves. These small medullated preganglionic
fibers are collected together in the pelvis into the nervus erigentes or pelvic nerve
974
NEUROLOGY
which proceeds to the hypogastric or pelvic plexuses from which postganglionic
fibers are distributed to the pelvic viscera. INIotor fibers pass to the smooth muscle
of the descending colon, rectum, anus and bladder. Vasodilators are distributed
to these organs and to the external genitalia, while inhibitory fibers probably pass
to the smooth muscles of the external genitalia. Afferent sympathetic fibers conduct
impulses from the pelvic viscera to the second, third and fourth sacral nerves.
Their cells of origin lie in the spinal ganglia.
Chorda tympani
- Submaxillary ganglion
Sublingual gland
Submaxillary gland
I.Th
Fig. 842. — Sympathetic connections of the submaxillary and superior cervical ganglia.
THE THORACOLUMBAR SYMPATHETICS.
The thoracolumbar sympathetic fibers arise from the dorso-lateral region of the
anterior column of the gray matter of the spinal cord and pass with the anterior
roots of all the thoracic and the upper two or three lumbar spinal nerves. These
preganglionic fibers enter the white rami communicantes and proceed to the
sympathetic trunk where many of them end in its ganglia, others pass to the pre-
vertebral plexuses and terminate in its collateral ganglia. The postganglionic
fibers have a wide distribution. The vasoconstrictor fibers to the bloodvessels of the
skin of the trunk and limbs, for example, leave the spinal cord as preganglionic
fibers in all the thoracic and the upper two or tlu-ee lumbar spinal nerves and
terminate in the ganglia of the sympathetic trunk, either in the ganglion directly
connected with its ramus or in neighboring ganglia. Postganglionic fibers arise
THE THORACOLUMBAR SYMPATHETICS
975
in these ganglia, pass through gray rami commimicantes to all the spinal nerves,
and are distributed with their cutaneous branches, ultimately leaving these branches
to join the small arteries. The postganglionic fibers do not necessarily return to
the same spinal nerves which contain the corresponding preganglionic fibers. The
vasoconstrictor fibers to the head come from the upper thoracic nerves, the pre-
ganglionic fibers end in the superior cervical ganglion. The postganglionic fibers
pass through the internal carotid nerve and branch from it to join the sensory
branches of the various cranial nerves, especially the trigeminal nerve; other fibers
to the deep structures and the salivary glands probably accompany the arteries.
—Auriculotemporal
Parotid gland
-+ -Tympanic nerve
Fig. 843. — Sympathetic connections of the otic and superior cer\-ical ganglia.
The postganglionic vasoconstrictor fibers to the bloodvessels of the abdominal
viscera arise in the prevertebral or collateral ganglia in which terminate many
preganglionic fibers. Vasoconstrictor fibers to the pelvic viscera arise from the
inferior mesenteric ganglia.
The pilomotor fibers to the hairs and the motor fibers to the sweat glands appar-
ently have a distribution similar to that of the vasoconstrictors of the skin.
A vasoconstrictor center has been located by the physiologists in the neighbor-
hood of the facial nucleus. Axons from its cells are supposed to descend in the spinal
cord to terminate about cell bodies of the preganglionic fibers located in the dorso-
lateral portion of the anterior column of the thoracic and upper lumbar region.
The motor supply to the dilator pupillse muscle of the eye comes from pregan-
976' NEUROLOGY
glionic sympathetic fibers which leave the spinal cord with the anterior roots of the
upper thoracic nerves. These fibers pass to the sympathetic trunk through the
white rami communicantes and terminate in the superior cervical ganglion. Post-
ganglionic fibers from the superior cervical ganglion pass through the internal
carotid nerve and the ophthalmic division of the trigeminal nerve to the orbit
where the long ciliary nerves conduct the impulses to the eyeball and the dilator
pupillee muscle. The cell bodies of these preganglionic fibers are connected with
fibers which descend from the mid-brain.
Other postganglionic fibers from the superior cervical ganglion are distributed as
secretory fibers to the salivary glands, the lacrimal glands and to the small glands
of the mucous membrane of the nose, mouth and phar^-nx.
The thoracic SATnpathetics supply accelerator nerves to the heart. They are
supposed to emerge from the spinal cord in the anterior roots of the upper four or
five thoracic nerves and pass with the white rami to the first thoracic ganglion,
here some terminate, others pass in the ansa subclavia to the inferior cervical
ganglion. The postganglionic fibers pass from these ganglia partly through the
ansa subcla\ia to the heart, on their way they intermingle with sympathetic fibers
from the vagus to form the cardiac plexus.
Inhibitory fibers to the smooth musculature of the stomach, the small intestine
and most of the large intestine are supposed to emerge in the anterior roots of the
lower thoracic and upper lumbar ner^'es. These fibers pass through the white rami
and s^^npathetic trunk and are conveyed by the splanchnic nerves to the pre-
vertebral plexus where they terminate in the collateral ganglia. From the celiac and
superior mesenteric ganglia postganglionic fibers (inhibitory) are distributed to the
stomach, the small intestine and most of the large intestine. Inhibitory fibers to
the descending colon, the rectum and Internal sphincter ani are probably post-
ganglionic fibers from the inferior mesenteric ganglion.
The thoracolumbar sympathetics are characterized by the presence of numerous
ganglia which may be divided into two groups, central and collateral.
The central ganglia are arranged in two vertical rows, one on either side of the
middle line, situated partly in front and partly at the sides of the vertebral column.
Each ganglion is joined by intervening nervous cords to adjacent ganglia so that
two chains, the sympathetic trunks, are formed. The collateral ganglia are found
in connection with three great prevertebral plexuses, placed within the thorax,
abdomen, and pelvis respectively.
The sympathetic trunks (iruncus sympathicns; gangliated cord) extend from the
base of the skull to the coccyx. The cephalic end of each is continued upward
through the carotid canal into the skull, and forms a plexus on the internal carotid
artery; the caudal ends of the trunks converge and end in a single ganglion, the
ganglion impar, placed in front of the coccjtc. The ganglia of each trunk are dis-
tinguished as cervical, thoracic, lumbar, and sacral and, except in the neck, they
closely correspond in number to the vertebrae. They are arranged thus:
Cervical portion .... ... 3 ganglia
Thoracic " 12
Lumbar " -4
Sacral " 4 or 5
(t
In the neck the ganglia lie in front of the transverse processes of the vertebrae;
in the thoracic region in front of the heads of the ribs; in the lumbar region on the
sides of the vertebral bodies; and in the sacral region in front of the sacrum.
Connections with the Spinal Nerves. — Communications are established between
the sympathetic and spinal nerves through what are known as the gray and white
rami communicantes (Fig. 799); the gray rami convey sympathetic fibers into the
spinal nerves and the white rami transmit spinal fibers into the sj'mpathetic.
THE CEPHALIC PORTION OF THE SYMPATHETIC SYSTEM 977
Each spinal nerve receives a gray ramus communicans from the sympathetic
trunk, but white rami are not supplied by all the spinal nerves. White rami are
derived from the first thoracic to the first lumbar nerves inclusive, while the
visceral branches which run from the second, third, and fourth sacral nerves directly
to the pelvic plexuses of the sympathetic belong to this category. The fibers which
reach the sympathetic through the white rami communicantes are medullated;
those which spring from the cells of the sympathetic ganglia are almost entirely
non-medullated. The sympathetic nerves consist of efi'erent and afferent fibers, the
origin and course of which are described on page 920).
The three great gangliated plexuses {collateral ganglia) are situated in front of
the vertebral column in the thoracic, abdominal, and pelvic regions, and are named,
respectively, the cardiac, the solar or epigastric, and the hypogastric plexuses.
They consist of collections of nerves and ganglia; the nerves being derived from
the sympathetic trunks and from the cerebrospinal nerves. They distribute
branches to the viscera.
Development. — The ganglion cells of the sympathetic system are derived from
the cells of the neural crests. As these crests move forward along the sides of the
neural tube and become segmented off to form the spinal ganglia, certain cells
detach themselves from the ventral margins of the crests and migrate toward the
sides of the aorta, where some of them are grouped to form the ganglia of the
sympathetic trunks, while others undergo a further migration and form the ganglia
of the prevertebral and visceral plexuses. The ciliary, sphenopalatine, otic, and
submaxillary ganglia which are found on the branches of the trigeminal nerve are
formed by groups of cells which have migrated from the part of the neural crest
which gives rise to the semilunar ganglion. Some of the cells of the ciliary ganglion
are said to migrate from the neural tube along the oculomotor nerve.
THE CEPHALIC PORTION OF THE SYMPATHETIC SYSTEM (PARS
CEPHALIC A S. SYMPATHICI).
The cephalic portion of the sympathetic system begins as the internal carotid
nerve, which appears to be a direct prolongation of the superior cervical ganglion.
It is soft in texture, and of a reddish color. It ascends by the side of the internal
carotid artery, and, entering the carotid canal in the temporal bone, divides into
two branches, which lie one on the lateral and the other on the medial side of that
vessel.
The lateral branch, the larger of the two, distributes filaments to the internal
carotid artery, and forms the internal carotid plexus.
The medial branch also distributes filaments to the internal carotid artery, and,
continuing onward, forms the cavernous plexus.
The internal carotid plexus {plexus caroticus inter nus; carotid plexus) is situated
on the lateral side of the internal carotid artery, and in the plexus there occasionally
exists a small gangliform swelling, the carotid ganglion, on the under surface of
the artery. The internal carotid plexus communicates with the semilunar gan-
glion, the abducent nerve, and the sphenopalatine ganglion; it distributes filaments
to the wall of the carotid artery, and also communicates with the tympanic branch
of the glossopharyngeal nerve.
The communicating branches with the abducent nerve consist of one or two
filaments which join that nerve as it lies upon the lateral side of the internal carotid
artery. The communication with the sphenopalatine ganglion is effected by a
branch, the deep petrosal, gwen off from the plexus on the lateral side of the artery;
this branch passes through the cartilage filling up the foramen lacerum, and joins
the greater superficial petrosal to form the nerve of the pterygoid canal (Vidian
nerve), which passes through the pterygoid canal to the sphenopalatine ganglion.
62
978 NEUROLOGY
The communication with the tympanic branch of the glossopharyngeal nerve is
eflfected by the caroticotympanic, which may consist of two or three delicate
filaments.
The cavernous plexus {ylexus cavernosus) is situated below and medial to that
part of the internal carotid artery which is placed by the side of the sella turcica
in the cavernous sinus, and is formed chiefly by the medial division of the internal
carotid nerve. It communicates with the oculomotor, the trochlear, the ophthalmic
and the abducent nerves, and with the ciliary ganglion, and distributes filaments to
the wall of the internal carotid artery. The branch of communication with the
oculomotor nerve joins that ner\e at its point of division; the branch to the troch-
lear nerve joins it as it lies on the lateral wall of the cavernous sinus; other filaments
are connected with the under surface of the ophthalmic nerve; and a second fila-
ment joins the abducent nerve.
The filaments of connection with the ciliary ganglion arise from the anterior part
of the cavernous plexus and enter the orbit through the superior orbital fissure;
they may join the nasociliary branch of the ophthalmic nerve, or be continued for-
ward as a separate branch.
The terminal filaments from the internal carotid and cavernous plexuses are
prolonged as plexuses around the anterior and middle cerebral arteries and the
ophthalmic artery; along the former vessels, they may be traced to the pia mater;
along the latter, into the orbit, where they accompany each of the branches of the
vessel. The filaments prolonged on to the anterior communicating artery connect
the sympathetic nerves of the right and left sides.
THE CERVICAL PORTION OF THE SYMPATHETIC SYSTEM (PARS
CERVICALIS S. SYMPATHICI).
The cervical portion of the sympathetic trunk consists of three ganglia, distin-
guished, according to their positions, as the superior, middle, and inferior ganglia,
connected by intervening cords. This portion receives no white rami communi-
cantes from the cervical spinal nerves; its spinal fibers are derived from the white
rami of the upper thoracic nerves, and enter the corresponding thoracic ganglia
of the sympathetic trunk, through which they ascend into the neck.
The superior cervical ganglion {ganglion cervicale superius), the largest of the
three, is placed opposite the second and third cervical vertebrae. It is of a reddish-
gray color, and usually fusiform in shape; sometimes broad and flattened, and occa-
sionally constricted at intervals; it is believed to be formed by the coalescence
of four ganglia, corresponding to the upper four cervical nerves. It is in relation,
in front, with the sheath of the internal carotid artery and internal jugular vein;
behind, with the Longus capitis muscle.
Its branches may be divided into inferior, lateral, medial, and anterior.
The Inferior Branch communicates with the middle cervical ganglion.
The Lateral Branches {external branches) consist of gray rami communicantes to
the upper four cervical nerves and to certain of the cranial nerves. Sometimes the
branch to the fourth cervical nerve may come from the trunk connecting the
upper and middle cervical ganglia. The branches to the cranial nerves consist
of delicate filaments, which run to the ganglion nodosum of the vagus, and to the
hypoglossal nerve. A filament, the jugular nerve, passes upward to the base of
the skull, and divides to join the petrous ganglion of the glossopharyngeal, and the
jugular ganglion of the vagus.
The Medial Branches {internal branches) are peripheral, and are the lamygo-
pharyngeal branches and the superior cardiac nerve.
The laryngopharyngeal branches {rami laryngoyharyngei) pass to the side of the
THE CERVICAL PORTION OF THE SYMPATHETIC SYSTEM 979
CAVERNOUS PLEXUS
MAXILLARY NERVE
SPHENOPALAflNE
GANGLION
CERVICAL
NERVE
pharynx, where they join with branches from the glossopharyngeal, vagus, and
external laryngeal nerves to form the pharyngeal plexus.
The superior cardiac nerve (n. cardiacus superior) arises by two or more branches
from the superior cervical ganglion, and occasionally receives a filament from the
trunk between the first and second cervical ganglia. It runs down the neck behind
the common carotid artery, and in front of the Longus colli muscle; and crosses
in front of the inferior thyroid
artery, and recurrent nerve.
The course of the nerves on the
two sides then differ. The right
nerve, at the root of the neck,
passes either in front of or behind
the subclavian artery, and along
the innominate artery to the
back of the arch of the aorta,
where it joins the deep part of
the cardiac plexus. It is con-
nected with other branches of
the sympathetic; about the
middle of the neck it receives
filaments from the external
laryngeal nerve; lower down,
one or two twigs from the
vagus; and as it enters the
thorax it is joined by a fila-
ment from the recurrent nerve.
Filaments from the nerve com-
municate with the thyroid
branches from the middle cer-
vical ganglion. The left nerve,
in the thorax, runs in front of
the left common carotid artery
and across the left side of the
arch of the aorta, to the super-
ficial part of the cardiac plexus.
The Anterior Branches {nn.
carotid exierni) ramify upon
the common carotid artery and
upon the external carotid artery
and its branches, forming around each a delicate plexus, on the nerves composing
which small ganglia are occasionally found. The plexuses accompanying some
of these arteries have important communications with other nerves. That sur-
rounding the external maxillary artery communicates with the submaxillary gan-
glion by a filament; and that accompanying the middle meningeal artery sends an
offset to the otic ganglion, and a second, the external petrosal nerve, to the genicular
ganglion of the facial nerve.
The middle cervical ganglion {ganglion cervicale medium) is the smallest of the
three cervical ganglia, and is occasionally wanting. It is placed opposite the sixth
cervical vertebra, usually in front of, or close to, the inferior thyroid artery. It
is probably formed by the coalescence of two ganglia corresponding to the fifth
and sixth cervical nerves.
It sends gray rami communicantes to the fifth and sixth cervical nerves, and
gives off the middle cardiac nerve.
The Middle Cardiac Nerve (n. cardiacus medius; great cardiac nerve), the largest
LOWER CERVICAL
GANGLION
INFERIOR CARDIAC
NERVE
FIRST
THORACIC
NERVE
Fig. 844. — Diagram of the cervical sympathetic. (Testut.)
980
NEUROLOGY
of the three cardiac nerves, arises from the middle cervical ganglion, or from the
trunk between the middle and inferior ganglia. On the right side it descends behind
the common carotid artery, and at the root of the neck runs either in front of or
behind the subclavian artery; it then descends on the trachea, receives a few
filaments from the recurrent nerve, and joins the right half of the deep part of the
cardiac plexus. In the neck, it communicates with the superior cardiac and recur-
rent nerves. On the left side, the middle cardiac nerve enters the chest between
the left carotid and subclavian arteries, and joins the left half of the deep part
of the cardiac plexus.
THORACIC NERVES.
RAMI COMMUNICANTES
VISCERAL
BRANCHES
INFERIOR CER-
VICAL GANGLION
VISCERAL
BRANCHES
THORACIC CHAIN
OF GANGLIA
i
SPLANCHNIC
GANGLION
GREATER
SPLANCHNIC
LESSER
SPLANCHNIC
RIGHT VAGUS
LOWEST
SPLANCHNIC
BR»NCH OF VAGUS
TO CELIAC GANGLION
CELIAC AXIS
SEMILUNAR GANGLION
SUPERIOR MESENTERIC
ARTERY AND PLEXUS
CELIAC PLEXUS
GUADRATUS
LUMBORUM
RENAL PLEXUS
Fig. 845. — Plan of right sympathetic cord and splanchnic nerves. (Testut.)
J
The inferior cervical ganglion (ganglion cervicale inferius) is situated between
the base of the transverse process of the last cervical vertebra and the neck of the
first rib, on the medial side of the costocervical artery. Its form is irregular; it is
larger in size than the preceding, and is frequently fused with the first thoracic
ganglion. It is probably formed by the coalescence of two ganglia which corre-
spond to the seventh and eighth cervical nerves. It is connected to the middle
THE THORACIC PORTION OF THE SYMPATHETIC SYSTEM 981
cervical ganglion by two or more cords, one of which forms a loop around the sub-
clavian artery and supplies offsets to it. This loop is named the ansa subclavia
(I leussoiii).
The ganglion sends gray rami communicantes to the seventh and eighth cervical
nerves.
It gives off the inferior cardiac nerve, and offsets to bloodvessels.
The inferior cardiac nerve (n. cardiacus inferior) arises from either the inferior
cervical or the first thoracic ganglion. It descends behind the subclavian artery
and along the front of the trachea, to join the deep part of the cardiac plexus. It
communicates freely behind the subclavian artery with the recurrent nerve and
the middle cardiac nerve.
The offsets to bloodvessels form plexuses on the subclavian artery and its branches.
The plexus on the vertebral artery is continued on to the basilar, posterior cerebral,
and cerebellar arteries. The plexus on the inferior thyroid artery accompanies
the artery to the thyroid gland, and communicates with the recurrent and external
laryngeal nerves, with the superior cardiac nerve, and with the plexus on the
common carotid artery.
THE THORACIC PORTION OF THE SYMPATHETIC SYSTEM (PARS
THORACALIS S. SMYPATHICI) (Fig. 846).
The thoracic portion of the sympathetic trunk consists of a series of ganglia,
which usually correspond in number to that of the vertebrae; but, on account
of the occasional coalescence of two ganglia, their number is uncertain. The
thoracic ganglia rest against the heads of the ribs, and are covered by the costal
pleura; the last two, however, are more anterior than the rest, and are placed on
the sides of the bodies of the eleventh and twelfth thoracic vertebrae. The ganglia
are small in size, and of a grayish color. The first, larger than the others, is of
an elongated form, and frequently blended with the inferior cervical ganglion.
They are connected together by the intervening portions of the trunk.
Two rami communicantes, a white and a gray, connect each ganglion with its
corresponding spinal nerve.
The branches from the vpper five ganglia are very small; they supply filaments
to the thoracic aorta and its branches. Twigs from the second, third, and fourth
ganglia enter the posterior pulmonary plexus.
The branches from the lower sevoi ganglia are large, and white in color; they
distribute filaments to the aorta, and unite to form the greater, the lesser, and the
lowest splanchnic nerves.
The greater splanchnic nerve {71. splanchnicus major; great splanchnic nerve) is
white in color, firm in texture, and of a considerable size; it is formed by branches
from the fifth to the ninth or tenth thoracic ganglia, but the fibers in the higher
roots may be traced upward in the sympathetic trunk as far as the first or second
thoracic ganglion. It descends obliquely on the bodies of the vertebrae, perforates
the crus of the diaphragm, and ends in the celiac ganglion. A ganglion (ganglion
splanchnicum) exists on this nerve opposite the eleventh or twelfth thoracic vertebra.
The lesser splanchnic nerve (/?. splanchnicus minor) is formed by filaments from
the ninth and tenth, and sometimes the eleventh thoracic ganglia, and from the
cord between them. It pierces the diaphragm with the preceding nerve, and
joins the aorticorenal ganglion.
The lowest splanchnic nerve {n. splanchnicus imus; least splanchnic nerve) arises
from the last thoracic ganglion, and, piercing the diaphragm, ends in the renal
plexus.
A striking analogy exists between the splanchnic and the cardiac nerves. The
cardiac nerves are three in number; they arise from all three cervical ganglia,
982
NEUROLOGY
and are distributed to a large and important organ in the thoracic cavity. The
splanchnic nerves, also three in number, are connected probably with all the thoracic
ganglia, and are distributed to important organs in the abdominal cavity.
Highest intercostal artery
tercostal vein
Rami communicantes
artcriosuna.
Fig. 846. — Thoracic portion of the sympathetic trunk.
• THE ABDOMINAL PORTION OF THE SYMPATHETIC SYSTEM (PARS
ABDOMINALIS S. SYMPATHICI; LUMBAR PORTION OF
GANGLIA TED CORD) (Fig. 847).
The abdominal portion of the sympathetic trunk is situated in front of the ver-
tebral column, along the medial margin of the Psoas major. It consists usually of
four lumbar ganglia, connected together by interganglionic cords. It is continuous
above with the thoracic portion beneath the medial lumbocostal arch, and
below with the pelvic portion behind the common iliac artery. The ganglia are
of small size, and placed much nearer the median line than are the thoracic ganglia.
THE ABDOMINAL PORTION OF THE SYMPATHETIC SYSTEM 983
Gray rami communicantes pass from all the ganglia to the lumbar spinal nerves.
The first and second, and sometimes the third, lumbar nerves send white rami
DiapJiragmatic
ganglion
Hepatic
arlMiry
Suprarenal gl
Greater
splanchnic
nerve
Right
celiac
ganglion
Aorticorenal ganglion
Lowest splanchnic
nerve
Senal artery
Communicating branch — -^'!\ ,
Branch to aortic plexus
Left celiac ganglion
Superior mesenteric
artery
^Greater splanchnic nerve
Lesser splanchnic
nerve
Aorticorenal
ganglion
Renal artery
Superior mesenteric
ganglion
Branch to aortic plexus
Sympathetic trunk
Inferior mesenteric artery
Inferior mesenteric
ganglion
Sacrovertehral angle
Common iliac vein
Common iliac artery
Fig. 847 — Abdominal portion of the sympathetic trunk, with tlie celiac and hjrpogastric plexuses. (Henle )
984 NEUROLOGY ^
communicantes to the corresponding ganglia. The rami commiinicantes are of
considerable length, and accompany the lumbar arteries around the sides of the
bodies of the vertebrae, passing beneath the fibrous arches from which some of the
fibers of the Psoas major arise.
Of the branches of distribution, some pass in front of the aorta, and join the aortic
plexus; others descend in front of the common iliac arteries, and assist in forming
the hypogastric plexus.
THE PELVIC PORTION OF THE SYMPATHETIC SYSTEM (PARS !
PELVINA S. SYMPATHICI). »
The pelvic portion of each sympathetic trunk is situated in front of the sacrum,
medial to the anterior sacral foramina. It consists of four or five small sacral
ganglia, connected together by interganglionic cords, and continuous above with
the abdominal portion. Below, the two pelvic sympathetic trunks converge, and
end on the front of the coccyx in a small ganglion, the ganglion impar.
Gray rami communicantes pass from the ganglia to the sacral and coccygeal
nerves. No white rami communicantes are given to this part of the gangliated
cord, but the visceral branches which arise from the third and fourth, and sometimes
from the second, sacral, and run directly to the pelvic plexuses, are regarded as
white rami communicantes.
The branches of distribution communicate on the front of the sacrum with the
corresponding branches from- the opposite side; some, from the first two ganglia,
pass to join the pelvic plexus, and others form a plexus, which accompanies the
middle sacral artery and sends filaments to the glomus coccygeum (coccygeal body).
THE GREAT PLEXUSES OF THE SYMPATHETIC SYSTEM. ''
The great plexuses of the sympathetic are aggregations of nerves and ganglia,
situated in the thoracic, abdominal, and pelvic cavities, and named the cardiac,
celiac, and hypogastric plexuses. They consist not only of sympathetic fibers
derived from the ganglia, but of fibers from the medulla spinalis, which are con-
veyed through the white rami communicantes. From the plexuses branches are
given to the thoracic, abdominal, and pelvic viscera.
The Cardiac Plexus (Plexus Cardiacus) (Fig. 838).
The cardiac plexus is situated at the base of the heart, and is divided into a super-
ficial part, which lies in the concavity of the aortic arch, and a deep part, between
the aortic arch and the trachea. The two parts are, however, closely connected.
The superficial part of the cardiac plexus lies beneath the arch of the aorta,
in front of the right pulmonary artery. It is formed by the superior cardiac branch
of the left sympathetic and the lower superior cervical cardiac branch of the left
vagus. A small ganglion, the cardiac ganglion of Wrisberg, is occasionally found
connected with these nerves at their point of junction. This ganglion, when
present, is situated immediately beneath the arch of the aorta, on the right side
of the ligamentum arteriosum. The superficial part of the cardiac plexus gives
branches (a) to the deep part of the plexus; (6) to the anterior coronary plexus;
and (c) to the left anterior pulmonary plexus.
The deep part of the cardiac plexus is situated in front of the bifurcation of
the trachea, above the point of division of the pulmonary artery, and behind the
aortic arch. It is formed by the cardiac nerves derived from the cervical ganglia
of the sympathetic, and the cardiac branches of the vagus and recurrent nerves.
The only cardiac nerves which do not enter into the formation of the deep part
THE CELIAC PLEXUS 985
of the cardiac plexus are the superior cardiac nerve of the left sympathetic, and the
lower of the two superior cervical cardiac branches from the left vagus, which pass
to the superficial part of the plexus.
The branches from the right half of the deep part of the cardiac plexus pass,
some in front of, and others behind, the right pulmonary artery; the former, the
more numerous, transmit a few filaments to the anterior pulmonary plexus, and
are then continued onward to form part of the anterior coronary plexus; those
behind the pulmonary artery distribute a few filaments to the right atrium, and are
then continued onward to form part of the posterior coronary plexus.
The left half of the deep part of the plexus is connected with the superficial part
of the cardiac plexus, and gives filaments to the left atrium, and to the anterior
pulmonary plexus, and is then continued to form the greater part of the posterior
coronary plexus.
The Posterior Coronary Plexus {plexus coronarius posterior; left coronary plexus)
is larger than the anterior, and accompanies the left coronary artery; it is chiefly
formed by filaments prolonged from the left half of the deep part of the cardiac
plexus, and by a few from the right half. It gives branches to the left atrium and
ventricle.
The Anterior Coronary Plexus {plexus coronarius anterior; right coronary plexus)
is formed partly from the superficial and partly from the deep parts of the cardiac
plexus. It accompanies the right coronary artery, and gives branches to the right
atrium and ventricle.
The Celiac Plexus (Plexus Coeliacus; Solar Plexus) (Figs. 838, 848).
The celiac plexus, the largest of the three sjTnpathetic plexuses, is situated at
the level of the upper part of the first lumbar vertebra and is composed of two
large ganglia, the celiac ganglia, and a dense net-work of nerve fibers uniting them
together. It surrounds the celiac artery and the root of the superior mesenteric
artery. It lies behind the stomach and the omental bursa, in front of the crura
of the diaphragm and the commencement of the abdominal aorta, and between
the suprarenal glands. The plexus and the ganglia receive the greater and lesser
splanchnic nerves of both sides and some filaments from the right vagus, and give
off numerous secondary plexuses along the neighboring arteries.
The Celiac Ganglia {ganglia coeliaca; semilunar ganglia) are two large irregularly-
shaped masses having the appearance of lymph glands and placed one on either
side of the middle line in front of the crura of the diaphragm close to the supra-
renal glands, that on the right side being placed behind the inferior vena cava. The
upper part of each ganglion is joined by the greater splanchnic nerve, while the
lower part, which is segmented off and named the aorticorenal ganglion, receives
the lesser splanchnic nerve and gives off the greater part of the renal plexus.
The secondary plexuses springing from or connected with the celiac plexus are
the
Phrenic. Renal.
Hepatic. Spermatic.
Lienal. Superior mesenteric.
Superior gastric. Abdominal aortic.
Suprarenal. Inferior mesenteric.
The phrenic plexus {plexus phrenicus) accompanies the inferior phrenic artery
to the diaphragm, some filaments passing to the suprarenal gland. It arises
from the upper part of the celiac ganglion, and is larger on the right than on the
left side. It receives one or two branches from the phrenic nerve. At the point
of junction of the right phrenic plexus with the phrenic nerve is a small ganglion
986
NEUROLOGY
(ganglion phrenicum). This plexus distributes branches to the inferior vena cava,
and to the suprarenal and hepatic plexuses.
The hepatic plexus {plexus hepaticus), the largest offset from the celiac plexus,
receives filaments from the left vagus and right phrenic nerves. It accompanies
the hepatic artery, ramifying upon its branches, and upon those of the portal vein
in the substance of the liver. Branches from this plexus accompany all the divisions
of the hepatic artery. A considerable plexus accompanies the gastroduodenal
artery and is continued as the inferior gastric plexus on the right gastroepiploic
artery along the greater curvature of the stomach, where it unites with offshoots
from the lienal plexus.
Phrenic
plexus
Celiac Left
plexus vagus
Right vagus
Hepatic
plexus
Common
bile-duct
Superior
mesenteric
plexus
Aortic
plexus
, Gastric plexus
Phrenic
plexus
Suprarenal
plexus
Lienal
plexus
Phrenic
ganglion
Greater
splanchnic
Celiac
ganglion
Renal plexus
Superior
mesenteric
ganglion
Spermatic
plexus
Lumbar
rf7^ " ganglia
Inferior
mesenteric
plexus
Fig. 848. — The celiac ganglia with the sympathetic plexuses of the abdominal viscera radiating from the ganglia.
(Toldt.)
t
The lienal plexus {plexus lienalis; splenic plexus) is formed by branches from the
celiac plexus, the left celiac ganglion, and from the right vagus nerve. It accom-
panies the lienal artery to the spleen, giving off, in its course, subsidiary plexuses
along the various branches of the artery.
THE HYPOGASTRIC PLEXUS 987
The superior gastric plexus (plexus gastricus superior; gastric or coronary plexus)
accompanies the left gastric artery along the lesser curvature of the stomach, and
joins with branches from the left vagus.
The suprarenal plexus {plexus suprarenalis) is formed by branches from the
celiac plexus, from the celiac ganglion, and from the phrenic and greater splanchnic
nerves, a ganglion being formed at the point of junction with the latter nerve.
The plexus supplies the suprarenal gland, being distributed chiefly to its medullary
portion; its branches are remarkable for their large size in comparison with that
of the organ they supply.
The renal plexus {plexus renalis) is formed by filaments from the celiac plexus,
the aorticorenal ganglion, and the aortic plexus. It is joined also by the smallest
splanchnic nerve. The nerves from these sources, fifteen or twenty in number,
have a few ganglia developed upon them. They accompany the branches of the
renal artery into the kidney; some filaments are distributed to the spermatic
plexus and, on the right side, to the inferior vena cava.
The spermatic plexus {plexus spermaticus) is derived from the renal plexus,
receiving branches from the aortic plexus. It accompanies the internal spermatic
artery to the testis. In the female, the ovarian plexus {plexus arterio' ovaricce)
arises from the renal plexus, and is distributed to the ovary, and fundus of the
uterus.
The superior mesenteric plexus (plexus mesentericus superior) is a continuation
of the lower part of the celiac plexus, receiving a branch from the junction of the
right vagus nerve with the plexus. It surrounds the superior mesenteric artery,
accompanies it into the mesentery, and divides into a number of secondary plexuses,
which are distributed to all the parts supplied by the artery, viz., pancreatic branches
to the pancreas; intestinal branches to the small intestine; and ileocolic, right
colic, and middle colic branches, which supply the corresponding parts of the great
intestine. The nerves composing this plexus are white in color and firm in texture;
in the upper part of the plexus close to the origin of the superior mesenteric artery
is a ganglion (ganglion mesentericum superius).
The abdominal aortic plexus (plexus aorticus abdominalis; aortic plexus) is formed
by branches derived, on either side, from the celiac plexus and ganglia, and receives
filaments from some of the lumbar ganglia. It is situated upon the sides and front of
the aorta, between the origins of the superior and inferior mesenteric arteries. From
this plexus arise part of the spermatic, the inferior mesenteric, and the hypogastric
plexuses; it also distributes filaments to the inferior vena cava.
The inferior mesenteric plexus (plexus mesentericus inferior) is derived chiefly
from the aortic plexus. It surrounds the inferior mesenteric artery, and divides
into a number of secondary plexuses, which are distributed to all the parts supplied
by the artery, viz., the left colic and sigmoid plexuses, which supply the descending
and sigmoid parts of the colon; and the superior hemorrhoidal plexus, which supplies
the rectum and joins in the pelvis with branches from the pelvic plexuses.
The Hypogastric Plexus (Plexus Hypogastricus) (Fig. 8.38).
The hypogastric plexus is situated in front of the last lumbar vertebra and the
promontory of the sacrum, between the two common iliac arteries, and is formed
by the union of numerous filaments, which descend on either side from the aortic
plexus, and from the lumbar ganglia; it divides, below, into two lateral portions
which are named the pelvic plexuses.
The Pelvic Plexuses (Fig. 838).- — The pelvic plexuses supply the viscera of the
pelvic cavity, and are situated at the sides of the rectum in the male, and at the
sides of the rectum and vagina in the female. They are formed on either side by
a continuation of the hypogastric plexus, by the sacral sympathetic efi'erent fibers
988
NEUROLOGY
from the second, third, and fourth sacral nerves, and by a few filaments from the
first two sacral ganglia. At the points of junction of these nerves small ganglia are
found. From these plexuses numerous branches are distributed to the viscera of
the pelvis. They accompany the branches of the hypogastric artery.
The Middle Hemorrhoidal Plexus {ylexus hccmorrhoidaUs mcdius) arises from the
upper part of the pelvic plexus. It supplies the rectum, and joins with branches
of the superior hemorrhoidal plexus.
nREATER SPLANCHNIC,
LOWEST THORACIC
GANGLION
UPPER LUMBAR
GANGLION
RENAL PLEXUS
ABDOMINAL AORTA-
AORTIC PLEXUS
LUMBAR SYMPATHETIC
VENA CAVA INFERIOR-..,
COMMISSURE BETWEEN
AORTIC AND HYPIiGAS-
TRIC PLEXUSES
COMMON ILIAC-
ARTERY ,
UPPER SACRAL ./
GANGLION
RECTUM
HYPOGASTRIC
PLEXUS
CELIAC PLEXUS
SUPERIOR MESEN-
TERIC PLEXUS
SMALL IN-
TESTINE
INFERIOR MESEN-
TERIC PLEXUS
SIGMOID
COLON
VESICAL
PLEXUS
BLADDER
-URETER
VESICULA
SEMINALIS
SPERMATIC
PLEXUS
PROSTATE
Fig. 849. — Lower half of right sympathetic cord. (Testut after Hirschfeld.)
The Vesical Plexus (plexus vesicalis) arises from the forepart of the pelvic plexus.
The nerves composing it are numerous, and contain a large proportion of spinal
nerve fibers. They accompany the vesical arteries, and are distributed to the sides
and fundus of the bladder. Numerous filaments also pass to the vesiculae seminales
and ductus deferentes; those accompanying the ductus deferens join, on the sper-
matic cord, with branches from the spermatic plexus.
The Prostatic Plexus {i)Icxus inostaticus) is continued from the lower part of the
pelvic plexus. The nerves composing it are of large size. They are distributed
to the prostate vesiculje seminales and the corpora cavernosa of the penis and
urethra. The nerves supplying the corpora cavernosa consist of two sets, the
THE HYPOGASTRIC PLEXUS 989
lesser and greater cavernous nerves, which arise from the forepart of the prostatic
plexus, and, after joining with branches from the puden(hil nerve, pas? forward
beneath the pubic arch.
The lesser cavernous nerves {nn. cavernosi penis minores; small cavernous nerves)
perforate the fibrous co\ering of the penis, near its root.
The greater cavernous nerve (w. cavernosus penis major; large cavernous plexus)
passes forward along the dorsum of the penis, joins with the dorsal nerve of the
penis, and is distributed to the corpora cavernosa.
The Vaginal Plexus arises from the lower part of the pelvic plexus. It is distributed
to the walls of the vagina, to the erectile tissue of the vestibule, and to the clitoris.
The nerves composing this plexus contain, like the vesical, a large proportion of
spinal nerve fibers.
The Uterine Plexus accompanies the uterine artery to the side of the uterus,
between the layers of the broad ligament; it communicates with the ovarian plexus.
BIBLIOGRAPHY.
Barker, L. F. : The Nervoas System and its Constituent Neurons, 1901.
Herrick, C. J.: An Introduction to Neurology, 1915.
HuBER, G. C: Lectures on the Sympathetic Nervous System, Jour. Comp. Neur., 1897, vii,
73-145.
Ramon y Cajal, S.: Histologie du Systeme Nerveux, Paris, 1909.
Sherrington, C. S.: The Integrative Action of the Nervous System, 1908.
Streeter, G. L.: The Development of the Nervous System, Keibel and Mall, Manual of
Human Embryology, 1912.
1
t
THE ORGANS OF THE SENSES AND
THE COMMON INTEGUMENT.
rPHE organs of the senses may be divided into (a) those of the special senses of
J- taste, smell, sight, and hearing, and (b) those associated with the general sensa-
tions of heat, cold, pain, pressure, etc.
THE PERIPHERAL ORGANS OF THE SPECIAL SENSES.
THE ORGAN OF TASTE (ORGANON GUSTUS).
The peripheral gustatory or taste organs consist of certain modified epithelial
cells arranged in flask-shaped groups termed gustatory calyculi (taste-buds), which
are found on the tongue and adjacent parts. They occupy nests in the stratified
epithelium, and are present in large numbers on the sides of the papillae vallatae
(Fig. 850), and to a less extent on their opposed walls. They are also found on the
Central lamina of
corium
Lateral lamina
Gustatory calyculus
Section across a sinus-
like vein, traversing
whole length of folium p,i;i:,
Scrolls
!; Serous gland
va.t,.
^"^■"""•^ Nerve bundles '"^'^■^'^-
Fig. 850. — Vertical section of papilla foliata of the rabbit, crossing the folia. (Ranvier.)
fungiform papillae over the back part and sides of the tongue, and in the general
epithelial covering of the same areas. They are very plentiful over the fimbriae
linguae, and are also present on the under surface of the soft palate, and on the
posterior surface of the epiglottis.
Structure. — Each taste bud is flask-like in shape (Fig. 851), its broad base resting on the corium,
and its neck opening by an orifice, the gustatory pore, between the cells of the epithelium. The
bud is formed by two kinds of cells: supporting cells and gustatory cells. The supporting cells
are mostly arranged like the staves of a cask, and form an outer envelope for the bud. Some,
however, are found in the interior of the bud between the gustatory cells. The gustatory cells
occupy the central portion of the bud; they are spindle-shaped, and each possesses a large spherical
(991)
992 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
nucleus near the middle of the cell. The peripheral end of the cell terminates at the gustatory
pore in a fine hair-Uke filament, the gustatory hair. The central process passes toward the deep
extremity of the bud, and there ends in single or bifurcated varicosities. The nerve fibrils after
losing their medullary sheaths enter the taste bud, and end in fine extremities between the gusta-
tory cells; other nerve fibrils ramify between the supporting cells and terminate in fine extremities;
these, however, are believed to be nerves of ordinary sensation and not gustatory.
Gustatory pore and
gustatory hfiirs
Fig. 851. — Taste-bud, highly magnified.
Nerves of Taste. — -The chorda tympani nerve, derived from the sensory root of the facial, is
the nerve of taste for the anterior two-thirds of the tongue; the nerve for the posterior third
is the glossopharyngeal.
THE ORGAN OF SMELL (ORGANON OLFACTORroS; THE NOSE).
The peripheral olfactory organ or organ of smell consists of two parts: an outer,
the external nose, which projects from the center of the face; and an internal,, the
nasal cavity, which is divided by. a septum into right and left nasal chambers.
The External Nose (Nasus Externus; Outer Nose).
The external nose is pyramidal in form, and its upper angle or root is connected
directly A\nth the forehead ; its free angle is termed the apex. Its base is perforated
by two elliptical orifices, the nares, separated from each other by an antero-posterior
septum, the columna. The margins of the nares are provided with a number of
stiff hairs, or vibrissae, which arrest the passage of foreign substances carried with
the current of air intended for respiration. The lateral surfaces of the nose form,
by their union in the middle line, the dorsum nasi, the direction of which varies
considerably in different individuals; the upper part of the dorsum is supported
by the nasal bones, and is named the bridge. The lateral surface ends below in
a rounded eminence, the ala nasi.
Structure. — The frame-work of the external nose is composed of bones and cartilages; it is
covered by the integument, and lined by mucous membrane.
The bony frame-work occupies the upper part of the organ ; it consists of the nasal bones, and
the frontal jjrocesses of the maxillaj.
The cartilaginous frame-work {cartilagines nasi) consists of five large pieces, viz., the cartilage
of the septum, the two lateral and the two greater alar cartilages, and several smaller pieces,
the lesser alar cartilages (Figs. 852, 853, 854). The various cartilages are connected to each other
and to the bones by a tough fibrous membrane.
The cartilage of the septum (cartilago septi nasi) is somewhat quadrilateral in form, thicker at
its margins than at its center, and completes the separation between the nasal cavities in front.
Its anterior margin, thickest above, is connected with the nasal bones, and is continuous with
the anterior margins of the lateral cartilages; below, it is connected to the medial crura of the
greater alar cartilages by fibrous tissue. Its posterior margin is connected with the perpendicular
plate of the ethmoid; its inferior margin with the vomer and the palatine processes of the maxillae.
THE EXTERNAL NOSE
993
It may be prolonged backward (especially in children) as a narrow process, the sphenoidal pro-
cess, for some distance between the vomer and perpendicular plate of the ethmoid. The septal
cartilage does not reach as far as the lowest part of the nasal septum. This is formed by the
medial crura of the greater alar cartilages and by the
skin; it is freely movable, and hence is termed the
septum mobile nasi.
The lateral cartilage {cartilago nasi lateralis; upper
lateral cartilage) is situated below the inferior margin
of the nasal bone, and is flattened, and triangular in
shape. Its anterior margin is thicker than the pos-
terior, and is continuous above with the cartilage of
the septum, but separated from it below by a
narrow fissure; its superior margin is attached to
the nasal bone and the frontal process of the max-
illa; its inferior margin is connected by fibrous
tissue with the greater alar cartilage.
The greater alar cartilage {cartilago alaris major;
lower lateral cartilage) is a thin, flexible plate, sit-
uated immediately below the preceding, and bent
upon itself in such a manner as to form the medial
and lateral walls of the naris of its own side. The
portion which forms the medial wall (cms mediale)
is loosely connected with the corresponding portion
of the opposite cartilage, the two forming, together
with the thickened integument and subjacent tis-
sue, the septimi mobile nasi. The part which
forms the lateral wall {cms laterale) is curved to
correspond with the ala of the nose; it is oval and
flattened, narrow behind, where it is connected with the frontal process of the maxilla by a tough
fibrous membrane, in which are found three or four small cartilaginous plates, the lesser alar
cartilages (cartilagines alares minores; sesamoid cartilages). Above, it is connected by fibrous
tissue to the lateral cartilage and front part of the cartilage of the septum; below, it falls short
of the margin of the naris, the ala being completed by fatty and fibrous tissue covered by skin.
In front, the greater alar cartilages are separated by a notch which corresponds with the apex
of the nose.
Fig. 852. — Cartilages of the nose. Side view.
Greater alar
cartilage
Lesser alar
cartilages
Fio. 853. — Cartilages of the nose, seen from below.
FiQ. 854. — Bones and cartilages of septum of no.se.
Right side.
The muscles acting on the external nose have been described in the section on Myology.
The integument of the dorsum and sides of the nose is thin, and loosely connected with the
subjacent parts; but over the tip and alae it is thicker and more firmly adherent, and is furnished
with a large number of sebaceous follicles, the orifices of which are usually very distinct.
The arteries of the external nose are the alar and septal branches of the external maxillary,
which supply the alae and septum; the dorsum and sides being supphed from the dorsal nasal
branch of the ophthalmic and the infraorbital branch of the internal maxillary. The veins end in
the anterior facial and ophthalmic veins.
The nerves for the muscles of the nose are derived from the facial, while the skin receives
branches from the infratrochlear and nasociliary branches of the ophthalmic, and from the infra-
orbital of the maxillary.
63
994
ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
I
The Nasal Cavity (Cavum Nasi; Nasal Fossa).
The nasal chambers are situated one on either side of the median plane. They
open in front through the nares, and communicate behind through the choanse
with the nasal part of the pharynx. The nares are somewhat pear-shaped apertures,
each measuring about 2.5 cm. antero-posteriorly and 1.25 cm. transversely at its
widest part. The choanse are two oval openings each measuring 2.5 cm. in the
vertical, and 1.25 cm. in the transverse direction in a well-developed adult skull.
For the description of the bony boundaries of the nasal cavities, see pages 194
and 195.
Inside the aperture of the nostril is a slight dilatation, the vestibule, bounded
laterally by the ala and lateral crus of the greater alar cartilage, and medially by
the medial crus of the same cartilage. It is lined by skin containing hairs and
sebaceous glands, and extends as a small recess toward the apex of the nose. Each
nasal cavity, above and behind the vestibule, is divided into two parts: an olfactory
region, consisting of the superior nasal concha and the opposed part of the septum,
and a respiratory region, which comprises the rest of the cavit}-.
Spkcno-eihmoidal recess
Pharyngeal orifice of andUory tube Pharyngeal recess
Fig. 85.5. — Lateral wall of nasal cavity.
'Lateral Wall (Figs. 855, 856). — On the lateral wall are the superior, middle, and
inferior nasal conchae, and below and lateral to each concha is the correspond-
ing nasal passage or meatus. Above the superior concha is a narrow recess,
the sphenoethmoidal recess, into which the sphenoidal sinus opens. The superior
meatus is a short oblique passage extending about half-way along the upper border
of the middle concha ; the posterior ethmoidal cells open into the front part of this
meatus. The middle meatus is below and lateral to the middle concha, and is
continued anteriorly into a shallow depression, situated above the vestibule and
named the atrium of the middle meatus. On raising or removing the middle concha
THE NASAL CAVITY
995
the lateral wall of this meatus is fully displayed. On it is a rounded elevation,
the bulla ethmoidalis, and below and in front of this is a curved cleft, the hiatus
semilunaris.
The bulla ethmoidalis is caused by the bulging of tiie middle ethmoidal cells
which open on or immediately above it, and the size of the bulla varies with that
of its contained cells.
Bristle in infundihulum
lljjiy ^ Cut edge of middle concha
■' / Hiatus semilunaris
' Btdla ethmoidalis
Opening of middle ethmoidal cells
Cut edge of superior concha
Openings of posterior ethmoidal cells
Bribtle in opening of sphenoidal sinus
Bristle in nasolacrimal canal ^ ■, ^
r, • .T . ■ . A Cut edge of
Bristle m opening of -^^^^-^^ ^^Jj^^
maxillary sinus
Orifice of
auditory
tube
Pharyngeal recess
FiQ. 856. — Lateral wall of nasal cavity; the three nasal conchae have been removed.
The hiatus semilunaris is bounded inferiorly by the sharp concave margin of the
uncinate process of the ethmoid bone, and leads into a curved channel, the infundih-
ulum, bounded above by the bulla ethmoidalis and below by the lateral surface
of the uncinate process of the ethmoid. The anterior ethmoidal cells open into the
front part of the infundibulum, and this in slightly over 50 per cent, of subjects
is directly continuous with the frontonasal duct or passage leading from the frontal
^ air sinus; but when the anterior end of the uncinate process fuses with the front
[ part of the bulla, this continuity is interrupted and the frontonasal duct then opens
I directly into the anterior end of the middle meatus.
' Below the bulla ethmoidalis, and partly hidden by the inferior end of the uncinate
process, is the ostium maxillare, or opening from the maxillary sinus; in a frontal
section this opening is seen to be placed near the roof of the sinus. An accessory
opening from the sinus is frequently present below the posterior end of the middle
nasal concha. The inferior meatus is below and lateral to the inferior nasal concha;
the nasolacrimal duct opens into this meatus under cover of the anterior part of
the inferior concha.
Medial Wall (Fig. 854). — The medial wall or septum is frequently more or
less deflected from the median plane, thus lessening the size of one nasal cavity
996 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
and increasing that of the other; ridges or spurs of bone growing into one or other
cavity from the septum are also sometimes present. Immediately o^•er the incisive
canal at the lower edge of the cartilage of the septum a depression, the nasopalatine
recess, is seen. In the septum close to this recess a minute orifice may be discerned;
it leads backward into a blind pouch, the rudimentary vomeronasal organ of Jacobson,
which is supported by a strip of cartilage, the vomeronasal cartilage. This organ
is well-developed in many of the lower animals, where it apparently plays a part
in the sense of smell, since it is supplied by twigs of the olfactory nerve and lined
by epithelium similar to that in the olfactory region of the nose.
The roof of the nasal cavity is narrow from side to side, except at its posterior
part, and may be di^•ided, from behind forward, into sphenoidal, ethmoidal, and
frontonasal parts, after the bones which form it.
The floor is concave from side to side and almost horizontal antero-posteriorly;
its anterior three-fourths are formed by the palatine process of the maxilla, its
posterior fourth by the horizontal process of the palatine bone. In its antero-
medial part, directly over the incisive foramen, a small depression, the nasopalatine
recess, is sometimes seen; it points downward and forward and occupies the
position of a canal which connected the nasal with the buccal cavity in early
fetal life.
The Mucous Membrane (membrana mucosa nasi). — The nasal mucous membrane
lines the nasal cavities, and is intimately adherent to the periosteum or perichon-
drium. It is continuous with the skin through the nares, and with the mucous
membrane of the nasal part of the pharynx through the choanse. From the nasal
cavity its continuity with the conjunctiva may be traced, through the nasolacrimal
and lacrimal ducts; and with the frontal, ethmoidal, sphenoidal, and maxillary
sinuses, through the several openings in the meatuses. The mucous membrane
is thickest, and most vascular, over the nasal conchae. It is also thick over the
septum ; but it is very thin in the meatuses on the floor of the nasal cavities, and in
the various sinuses.
Owing to the thickness of the greater part of this membrane, the nasal cavities
are much narrower, and the middle and inferior nasal conchae appear larger and
more prominent than in the skeleton; also the various apertures communicating
with the meatuses are considerably narrowed.
Structure of the Mucous Membiane (Fig. 857). — The epithelium covering the mucous mem-
brane differs in its character according to the functions of the part of the nose in which it is found.
In the respiratory region it is columnar and ciliated. Interspersed among the columnar cells
are goblet or mucin cells, while between their bases are found smaller pyramidal cells. Beneath
the epithelium and its basement membrane is a fibrous layer infiltrated with lymph corpuscles,
so as to form in many parts a diffuse adenoid tissue, and under this a nearly continuous layer
of small and larger glands, some mucous and some serous, the ducts of which open upon the
surface. In the olfactory region the mucous membrane is yellowish in color and the epithelial
cells are columnar and non-ciliated; they are of two kinds, supporting cells and olfactorj^ cells.
The supporting cells contain oval nuclei, which are situated in the deeper parts of the cells and
constitute the zone of oval nuclei; the superficial part of each cell is columnar, and contains
granules of yellow pigment, while its deep part is prolonged as a delicate process which ramifies
and communicates with similar processes from neighboring cells, so as to form a net -work in the
mucous membrane. Lying between the deep processes of the supporting cells are a number of
bipolar nerve cells, the olfactory cells, each consisting of a small amount of granular protoplasm
with a large spherical nucleus, and possessing two processes — a superficial one which runs between
the columnar epithehal cells, and projects on the surface of the mucous membrane as a fine,
hair-Uke process, the olfactory hair ; the other or deep process runs inward, is frequently beaded,
and is continued as the axon of an olfactory nerve fiber. Beneath the epithehum, and extending
through the thickness of the mucous membrane, is a layer of tubular, often branched, glands,
the glands of Bowman, identical in structure with serous glands. The epithelial cells of the nose,
fauces and respiratory passages play an important role in the maintenance of an equable tempera-
ture, by the moisture with which they keep the surface always slightly lubricated.
Vessels and Nerves. — The arteries of the nasal cavities are the anterior and posterior eth-
moidal branches of the ophthalmic, which supply the ethmoidal cells, frontal sinuses, and roof
THE NASAL CAVITY
997
of the nose; the sphenopalatine branch of the internal maxillary, which supplies the mucous
membrane covering the conchse, the meatuses and septum; the septal branch of the superior labial
of the external maxillary; the infraorbital and alveolar branches of the internal maxillary, which
supply the lining membrane of the maxillary sinus; and the pharyngeal branch of the same artery,
distributed to the sphenoidal sinus. The ramifications of these vessels form a close plexiform
net-work, beneath and ia the substance of the mucous membrane.
Epitheliu;
Nerve bundles
Glands of Bow-t-^^j^j
man
Nerve bundles
Fig. 857. — Section of the olfactory mucous membrane. (Cadiat.)
The veins form a close cavernous plexus beneath the mucous membrane. This plexus is especi-
ally well-marked over the lower part of the septum and over the middle and inferior conchse. Some
of the veins open into the sphenopalatine vein; others join the anterior facial vein; some accom-
pany the ethmoidal arteries, and end in the
ophthalmic veins; and, lastly, a few communi-
cate with the veins on the orbital surface of the
frontal lobe of the brain, through the foramina
in the cribriform plate of the ethmoid bone;
when the foramen cecum is patent it transmits
a vein to the superior sagittal sinus.
The l3anphatics have already been described
(p. 695).
The nerves of ordinary sensation are: the
nasociliary branch of the ophthalmic, filaments
from the anterior alveolar branch of the max-
illary, the nerve of the pterygoid canal, the
nasopalatine, the anterior palatine, and nasal
branches of the sphenopalatine ganglion.
The nasociliary branch of the ophthalmic
distributes filaments to the forepart of the
septum and lateral wall of the nasal cavity.
Filaments from the anterior alveolar nerve
supply the inferior meatus and inferior concha.
The nerve of the pterygoid canal supplies the
upper and back part of the septum, and superior
concha; and the upper nasal branches from the sphenopalatine ganglion have a similar distri-
bution. The nasopalatine nerve supphes the middle of the septum. The anterior palatine
nerve supphes the lower nasal branches to the middle and inferior conchae.
The olfactory, the special nerve of the sense of smell, is distributed to the olfactory region.
Its fibers arise from the bipolar olfactory cells and are destitute of medullary sheaths. They
unite in fasciculi which form a plexus beneath the mucous membrane and then ascend in grooves
or canals in the ethmoid bone; they pass into the skull through the foramina in the cribriform
plate of the ethmoid and enter the under surface of the olfactory bulb, in which they ramify
and form synapses with the dendrites of the mitral cells (Fig. 772).
Fig. 858. — Nerves of septum of nose. Right side
998
ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
The Accessory Sinuses of the Nose (Sinus Paranasales) (Figs. 855, 856, 859).
The accessory sinuses or air cells of the nose are the frontal, ethmoidal, sphe-
noidal, and maxillary; they vary in size and form in different individuals, and
are lined by ciliated mucous membrane directly continuous with that of the nasal
cavities.
The Frontal Sinuses {sinus frontales), situated behind the superciliary arches,
are rarely symmetrical, and the septum between them frequently deviates to one
or other side of the middle line. Their average measurements are as foltows:
height, 3 cm.; breadth, 2.5 cm.; depth from before backward, 2.5 cm. Each opens
into the anterior part of the corresponding middle meatus of the nose through the
frontonasal duct which traverses the anterior part of the labyrinth of the ethmoid.
Absent at birth, they are generally fairly well developed between the seventh and
eighth years, but only reach their full size after puberty.
Superior concha
Ethmoidal air cell
— Swperic/r
meatus
Middle
concha
Middle
meatics
Septum
nasi
Inferior
concha
Maxillary
simis
Inferior
meatus
Fi(i. 859. — Coronal section of nasal cavities.
The Ethmoidal Air Cells {cellulcp ethnoidales) consist of numerous thin-walled
cavities situated in the ethmoidal labyrinth and completed by the frontal, maxilla,
lacrimal, sphenoidal, and palatine. They lie between the upper parts of the nasal
cavities and the orbits, and are separated from these cavities by thin bony
laminae. On either side they are arranged in three groups, anterior, middle, and
posterior. The anterior and middle groups open into the middle meatus of the
nose, the former by way of the infundibulum, the latter on or above the bulla
ethmoidalis. The posterior cells open into the superior meatus under cover of
the superior nasal concha; sometimes one or more opens into the sphenoidal sinus.
The ethmoidal cells begin to develop during fetal life.
The Sphenoidal Sinuses [sinus sphenoidales) contained within the body of the
sphenoid vary in size and shape; owing to the lateral displacement of the inter-
THE ACCESSORY SINUSES OF THE NOSE
999
vening septum they are rarely symmetrical. The following are their average
measurements: vertical height, 2.2 cm.; transverse breadth, 2 cm.; antero-posterior
depth, 2.2 cm. When exceptionally large they may extend into the roots of the
Ethmoidal infundibulum ,
Ant. ethmoidal air cells i
Post, ethmoidal air ce
Primitive frontal sinus
Xasolacrimal duct
-Maxillary sinus
Fig. 860.' — Specimen from a ehild eight days old. By sagittal sections removing the lateral portion of frontal bone,
lamina papyracea of ethmoid, and lateral portion of maxilla- — the sinus maxillaris, oellulse ethmoidalcs. anterior and pos-
terior, infundibulum ethmoidale, and the primitive sinus frontalis are brought into view. (Davis.)
pterygoid processes or great wings, and may invade the basilar part of the occipital
bone. Each sinus communicates with the sphenoethmoidal recess by means of
an aperture in the upper part of its anterior wall. They are present as minute
cavities at birth, but their main development takes place after puberty.
Ant. ethmoidal air cells
Post, ethmoidal air celh
Optic foramen _ —
Int. carotid art. -;;::,^. ^^^^
Oculomotor nerr>
Trochlear nen ■
Gasserian ganglion
Frontul sinus developing
from a frontal cell
V Ethmoidal infundibulum
-; Fossa of lacrimul sac
Maxillary ostium
>-C^
1^
Abducens nerve
Int. carotid art.
Fig 8()1. — Specimen from a child one year, four months, and seven days old. Lateral view of frontal,
ethmoidal, and maxillary sinus areas. (Davis.)
The Maxillary Sinus {sinus maxillaris; antrum of Ilighmore), the largest of the
accessory sinuses of the nose, is a pyramidal cavity in the body of the maxilla.
Its base is formed by the lateral wall of the nasal cavity, and its apex extends into
the zygomatic process. Its roof or orbital wall is frequently ridged by the infra-
Davis, W. H. Nasal Accessory Sinuses in Man, 1914.
4
1000 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
orbital canal, while its floor is formed by the alveolar process and is usually | to 10
mm. below the level of the floor of the nose; projecting- into the floor are several
conical ele\'ations corresponding with the roots of the first and second molar teeth,
and in some cases the floor is perforated by one or more of these roots. The size
of the sinus A'aries in different skulls, and even on the two sides of the same skull.
The adult capacity varies from 9.5 c.c. to 20 c.f^., average about 14.75 c.c. The fol-
lowing measurements are those of an average-sized sinus: vertical height opposite
the first molar tooth, 3.75 cm.; transverse breadth, 2.5 cm.; antero-posterior depth,
3 cm. In the antero-superior part of its base is an opening through which it com-
municates with the lower part of the hiatus semilunaris ; a second orifice is frequently
seen in, or immediately behind, the hiatus. The maxillary sinus appears as a shal-
low groove on the medial surface of the bone about the fourth month of fetal life,
but does not reach its full size until after the second dentition.^ At birth it measures
about 7 mm. in the dorso-ventral direction and at twenty months about 20 mm.^
Frontal sinus
Frontal ostium
Infundibulum cells
Fossa of lacrimul sar
Maxillary ostium
Maxillary septum -
,Ant. ethmoidal air cells
.Post, ethmoidal air cells
Fig. 862. — Specimen from a child eight years, eight months, and one day old. Lateral view of frontal, ethmoidal and
maxillary sinus areas, the lateral portion of each having been removed by sagittal cuts. Note that the sinus frontalis
developed directly from the infundibulum ethmoidale. Note also t he incomplete septa in the sinus maxillaris. (Da\'is.)
THE ORGAN OF SIGHT (ORG ANON VISUS; THE EYE).
The bulb of the eye (bulbus oculi; eyeball), or organ of sight, is contained in the
cavity of the orbit, where it is protected from injury and moved by the ocular
muscles. Associated with it are certain accessory structures, viz., the muscles,
fasciae, eyebrows, eyelids, conjunctiva, and lacrimal apparatus.
The bulb of the eye is imbedded in the fat of the orbit, but is separated from it
by a thin membranous sac, the fascia bulbi (page 1024). It is composed of segments
of two spheres of different sizes. The anterior segment is one of a small sphere;
' The various measurements of the accessory sinuses of the nose are based on those given by Aldren Turner in his
Accessory Sinuses of the Nose.
2 Schaeffer, J. P., Am. Jour. Anat., 1910, x.
THE ORGAN OF SIGHT
1001
it is transparent, and forms about one-sixth of the bulb. It is more prominent
than the posterior segment, which is one of a larger sphere, and is opaque, and forms
about five-sixths of the bulb. The term anterior pole is applied to the central point
of the anterior curvature of the bulb, and that of posterior pole to the central i)oint
of its posterior curvature; a line joining the two poles forms the optic axis. The
axes of the two bulbs are nearly parallel, and therefore do not correspond to the
Cavity of fore-hrain
Invagination of
ectoderm to form
lens rudiment
Pig>nented layer of retina
^^^'^^-^If^rgin of optic cup
Nervous layer of retina
Optic vesicle
Fig. 863. — Transverse section of head of chick embryo of forty-eiglit liours' incubation. (Duval.)
axes of the orbits, which are directed forward and lateralward. The optic nerves
follow the direction of the axes of the orbits, and are therefore not parallel; each
enters its eyeball 3 mm. to the nasal side and a little below the level of the posterior
pole. The bulb measures rather more in its transverse and antero-posterior diame-
ters than in its vertical diameter, the former amounting to about 24 mm., the latter
to about 23.5 mm. ; in the female all three diameters are rather less than in the male;
its antero-posterior diameter at
Cavity of fore-brain
Pigmented layer
of retina
Ectoderm
Lens
Nervous layer of
retina
birth is about 17.5 mm., and at
puberty from 20 to 21 mm.
Development. — The eyes begin
to develop as a pair of diverticula
from the lateral aspects of the fore-
brain. These diverticula make their
appearance before the closure of the
anterior end of the neural tube;
after the closure of the tube they are
known as the optic vesicles. They
project toward the sides of the
head, and the peripheral part of
each expands to form a hollow
bulb, while the proximal part re-
mains narrow and constitutes the
optic stalk (Figs. 863, 864). The
ectoderm overlying the bulb be-
comes thickened, invaginated, and finally severed from the ectodermal covering
of the head as a vesicle of cells, the lens vesicle, which constitutes the rudi-
ment of the crystalline lens. The outer wall of the bulb becomes thickened and
invaginated, and the bulb is thus converted into a cup, the optic cup, consisting
of two strata of cells (Fig. 864). These two strata are continuous with each
other at the cup margin, which ultimately overlaps the front of the lens and
reaches as far forward as the future aperture of the pupil. The invagination is not
limited to the outer wall of the bulb, but involves also its postero-inferior surface
Fig.
Optic stalk
864. — Transverse section of head of chick embrj-o of
fifty-two hours' incubation. (Duval.)
1002 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
and extends in the form of a groove for some distance along the optic stalk, so that,
for a time, a gap or fissure, the choroidal fissure, exists in the lower part of the
cup (Fig. 865). Through the groove and fissure the mesoderm extends into the
optic stalk and cup, and in this mesoderm a bloodvessel is developed; during the
seventh week the groove and fissure are closed and the vessel forms the central
artery of the retina. Sometimes the choroidal fissure persists, and when this
occurs the choroid and iris in the region of the fissure remain undeveloped, giving
rise to the condition known as colohoma of the choroid or iris.
Thalamencephalon — i
Optic stalk
Telencephalon
Edge of optic cup
Choroidal fissure
Arteria centralis
retina:
Fig. 865. — Optic cup and choroidal fissure seen from below, from a human embr>-o of about four weeks.
(Kollmann.)
The retina is developed from the optic cup. The outer stratum of the cup
persists as a single layer of cells which assume a columnar shape, acquire pigment,
and form the pigmented layer of the retina; the pigment first appears in the cells
near the edge of the cup. The cells of the inner stratum proliferate and form a
layer of considerable thickness from which the nervous elements and the susten-
tacular fibers of the retina, together with a portion of the vitreous body, are
developed. In that portion of the cup which overlaps the lens the inner stratum is
not differentiated into nervous elements, but forms a layer of columnar cells which
is applied to the pigmented layer, and these two strata form the pars ciliaris and
pars iridica retinae.
The cells of the inner or retinal layer of the optic cup become differentiated into spongioblasts
and germinal cells, and the latter by their subdivisions give rise to neuroblasts. From the spongio-
blasts the sustentacular fibers of Miiller, the outer and inner limiting membranes, together with
the groundwork of the molecular layers of the retina are formed. The neuroblasts become
arranged to form the ganghonic and nuclear layers. The laj-er of rods and cones is first developed
in the central part of the optic cup, and from there gradually extends toward the cup margin.
All the layers of the retina are completed by the eighth month of fetal life.
The optic stalk is converted into the optic nerve by the obliteration of its cavity
and the growth of nerve fibers into it. Most of these fibers are centripetal, and
grow backward into the optic stalk from the nerve cells of the retina, but a few
extend in the opposite direction and are derived from nerve cells in the brain. The
fibers of the optic nerve receive their medullary sheaths about the tenth week after
birth. The optic chiasma is formed by the meeting and partial decussation of the
fibers of the two optic nerves. Behind the chiasma the fibers grow backward as
the optic tracts to the thalami and mid-brain.
The crystalline lens is developed from the lens vesicle, which recedes within the
THE ORGAN OF SIGHT
1003
margin of the cup, and becomes separated from the overlying ectoderm by mes-
oderm. The cells forming the posterior wall of the vesicle lengthen and are con-
verted into the lens fibers, which grow forward and fill up the cavity of the vesicle
(Fig. 866). The cells forming the anterior wall retain their cellular character, and
form the epithelium on the anterior surface of the adult lens. By the second month
the lens is invested by a vascular mesodermal capsule, the capsula vasculosa lentis;
the bloodvessels supplying the posterior part of this capsule are derived from the
hyaloid artery; those for the anterior part from the anterior ciliary arteries; the
portion of the capsule which covers the front of the lens is named the pupillary
membrane. By the sixth month all the vessels of the capsule are atrophied except
the hyaloid artery, which disappears during the ninth month; the position of this
artery is indicated in the adult by the hyaloid canal, which reaches from the optic
disk to the posterior surface of the lens. With the loss of its bloodvessels the cap-
sula vasculosa lentis disappears, but sometimes the pupillary membrane persists
at birth, giving rise to the condition termed congenital atresia of the pupil.
Rudiment of choroid
Rectus muscle
Optic nerve
Retina
Pigmented layer
Vitreous body
(shrunken)
Cornea
Membrana pupillarta
Pars ciiiaris and pars iridica retincB
Fig. 866. — Horizontal section through the eye of an eighteen days' embryo rabbit.
X 30. (Kolliker.)
The vitreous body is developed between the lens and the optic cup. The lens
rudiment and the optic vesicle are at first in contact with each other, but after the
closure of the lens vesicle and the formation of the optic cup the former withdraws
itself from the retinal layer of the cup; the two, however, remain connected by a net-
work of delicate protoplasmic processes. This network, derived partly from the cells
of the lens and partly from those of the retinal layer of the cup, constitutes the
primitive vitreous body (Figs.. 867, 868). At first these protoplasmic processes
spring from the whole of the retinal layer of the cup, but later are limited to the
ciliary region, where by a process of condensation they appear to form the zonula
ciiiaris. The mesoderm which enters the cup through the choroidal fissure and
around the equator of the lens becomes intimately united with this reticular tissue,
and contributes to form the vitreous body, which is therefore derived partly from
the ectoderm and partly from the mesoderm.
1004 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
Pigmented Mesodermal
layer of part of Rudiment
Upper eychd retina vitreous body of sclera
Primitive
vitreous
o ^ ""TO
^^'
^ ;■; J- © a®® 9
Mesoderm
.*^'
Ectodermal Nervous layer
part of of retina
vitreous body
Fig. 867.— Sagittal section ol eye of human embryo of six weeks. (Kollmann.)
Lens
Blood-vessel
^'f : t '•r'. V- V
Retina
.*.";i- '
ili-^ij^v
optic cup
FiQ 868. — Section of developing eye of trout. (Szily.)
THE TUNICS OF THE EYE 1005
The anterior chamber of the eye appears as a cleft in the mesoderm separating
the lens from the overlying ectoderm. The layer of mesoderm in front of the cleft
forms the substantia propria of the cornea, that behind the cleft the stroma of the
iris and the pupillary membrane. The fibers of the ciliary muscle are derived from
the mesoderm, but those of the Sphincter and Dilatator pupilhe are of ectodermal
origin, being developed from the cells of the pupillary part of the optic cup.
The sclera and choroid are derived from the mesoderm surrounding the optic cup.
The eyelids are formed as small cutaneous folds (Figs. 8G6, 867), which about
the middle of the third month come together and unite in front of the cornea.
They remain united until about the end of the sixth montli.
The lacrimal sac and nasolacrimal duct result from a thickening of the ectoderm
in the groove, nasooptic furrow, between the lateral nasal and maxillary processes.
This thickening forms a solid cord of cells which sinks into the mesoderm; during
the third month the central cells of the cord break down, and a lumen, the naso-
lacrimal duct, is established. The lacrimal ducts arise as buds from the upper part
of the cord of cells and secondarily establish openings {'puncta lacrimalia) on the
margins of the lids. The epithelium of the cornea and conjunctiva, and that which
lines the ducts and alveoli of the lacrimal gland, are of ectodermal origin, as are
also the eyelashes and the lining cells of the glands which open on the lid-margins.
The Tunics of the Eye (Fig. 869).
From without inward the three tunics are: (1) A fibrous tunic, consisting of the
sclera behind and the cornea in front; (2) a vascular pigmented tunic, comprising,
from behind forward, the choroid, ciliary body, and iris; and (3) a nervous tunic,
the retina.
The Fibrous Tunic (tunica fibrosa oculi). — The sclera and cornea (Fig. 869)
form the fibrous tunic of the bulb of the eye; the sclera is opaque, and constitutes
the posterior five-sixths of the tunic; the cornea is transparent, and forms the
anterior sixth.
The Sclera. — The sclera has received its name from its extreme density and hard-
ness; it is a firm, unyielding membrane, serving to maintain the form of the bulb.
It is much thicker behind than in front; the thickness of its posterior part is 1 mm.
Its external surface is of white color, and is in contact with the inner surface of the
fascia of the bulb; it is quite smooth, except at the points- where the Recti and
Obliqui are inserted into it; its anterior part is covered by the conjunctival mem-
brane. Its inner surface is brown in color and marked by grooves, in which the
ciliary nerves and vessels are lodged; it is separated from the outer surface of the
choroid by an extensive lymph space (spatium peri chorioide ale) which is traversed
by an exceedingly fine cellular tissue, the lamina suprachorioidea. Behind it is
pierced by the optic nerve, and is continuous through the fibrous sheath of this
nerve with the dura mater. Where the optic nerve passes through the sclera, the
latter forms a thin cribriform lamina, the lamina cribrosa sclerse; the minute orifices
in this lamina serve for the transmission of the nervous filaments, and the fibrous
septa dividing them from one another are continuous with the membranous pro-
cesses which separate the bundles of nerve fibers. One of these openings, larger
than the rest, occupies the center of the lamina; it transmits the central artery
and vein of the retina. Around the entrance of the optic nerve are numerous
small apertures for the transmission of the ciliary vessels and nerves, and about
midway between this entrance and the sclerocorneal junction are four or five
large apertures for the transmission of veins (venae vorticosse). In front, the sclera
is directly continuous with the cornea, the line of union being termed the sclero-
corneal junction. In the inner part of the sclera close to this junction is a circular
canal, the sinus venosus sclerse (canal of Schlemm). In a meridional section of this
1006 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
region this sinus presents the appearance of a cleft, the outer wall of which consists
of the firm tissue of the sclera, while its inner wall is formed by a triangular mass
of trabecular tissue (Fig. 870) ; the apex of the mass is directed forward and is con-
tinuous with the posterior elastic lamina of the cornea. The sinus is lined by
endothelium and communicates externally with the anterior ciliary \'eins.
The aqueous humor drains into the scleral sinuses by passage through the
"pectinate villi" which are analogous in structure and function to the arachnoid
villi of the cerebral meninges.^
Sulciis circularis cornea
Posterior chamber
Sulcus circularis comeee
/
Ciliary body
Rectus
lateralis
Zonular spaces
Hyaloid canai
Btctus
medialis
'-;— Sclera
Choroid
Fovea centralis
Nerve sheath
Fig. 869. — ^Horizohtal section of the eyeball.
A. centralis retincB
Optic nerve
Structure. — The sclera is formed of white fibrous tissue intermixed with fine elastic fibers;
flattened connective-tissue corpuscles, some of which are pigmented, are contained in cell spaces
between the fibers. The fibers are aggregated into bundles, which are arranged chiefly in a
longitudinal direction. Its vessels are not numerous, the capillaries being of small size, uniting
at long and wide intervals. Its nerves are derived from the ciliary nerves, but their exact mode
of ending is not known.
The Cornea. — The cornea is the projecting transparent part of the external tunic,
and forms the anterior sixth of the surface of the bulb. It is almost circular in
outline, occasionally a little broader in the transverse than in the vertical direction.
It is convex anteriorly and projects like a dome in front of the sclera. Its degree
of curvature varies in different individuals, and in the same individual at different
periods of life, being more pronounced in youth than in advanced life. The cornea
is dense and of uniform thickness throughout; its posterior surface is perfectly
circular in outline, and exceeds the anterior surface slightly in diameter. Imme-
diately in front of the sclero-corneal junction the cornea bulges inward as a thickened
rim, and behind this there is a distinct furrow between the attachment of the iris
and the sclero-corneal junction. This furrow has been named by Arthur Thomson^
1 Wegefarth. Jour. Med. Research, September, 1914.
-" Atlas of the Eye, Clarendon Press, Oxford, 1912.
THE TUNICS OF THE EYE
1007
the sulcus circularis corneae; it is bounded externally by the trabecular tissue
already described as forming the inner wall of the sinus venosus sclerae. Between
this tissue and the anterior surface of the attached margin of the iris is an angular
recess, named the iridial angle or filtration angle of the eye (Fig. S70). Immediately
outside the filtration angle is a projecting rim of scleral tissue which appears in a
meridional section as a small triangular area, termed the scleral spur. Its base
is continuous with the inner surface of the sclera immediately to the outer side of the
filtration angle and its apex is directed forward and inward. To the anterior sloping
margin of this spur are attached the bundles of trabecular tissue just referred to;
from its posterior margin the meridional fibers of the Ciliaris muscle arise.
Si7ius venous sclera;
Trabecular tissue
Cornea
Sclera
Scleral vein
Radial muscular fibers / , i nr •,■ , ,-, ,- ^, w •
Qf l^lg / J I Menaional jibers oj Cuiaris
Circular fibers of Cilians I Scleral spur
Iridial angle
Fia. 870. — Enlarged general view of the iridial angle. (Arthur Thomson.)
Structure (Fig. 871). — The cornea consists from before backward of four layers, viz.: d^
the corneal epithelium, continuous with that of the conjunctiva; (2) the substantia propria
(3) the posterior elastic lamina; and (4) the endothelium of the anterior chamber.
The corneal epitheUum {epithelium cornea; anterior layer) covers the front of the cornea and
consists of several layers of cells. The cells of the deepest layer are columnar; then follow two or
three layers of polyhedral cells, the majority of which are prickle cells similar to those found in
the stratum mucosum of the cuticle. Lastly, there are three or four layers of squamous cells,
with flattened nuclei.
The substantia propria is fibrous, tough, unyielding, and perfectly transparent. It is com-
posed of about sixty flattened lamella?, superimposed one on another. These lamellai are made
up of bundles of modified connective tissue, the fibers of which are directly continuous with those
of the sclera. The fibers of each lamella are for the most part parallel with one another, but at
right angles to those of adjacent lamellae. Fibers, however, frequently pass from one 5amella
to the next.
1008 , ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
The lamellae are connected with each other by an interstitial cement substance; in which are
spaces, the corneal spaces. These are stellate in shape and communicate with one another by
numerous offsets. Each contains a cell, the corneal corpuscle, resembhng in form the space in
which it is lodged, but not entirely fiUing it.
b»^;ugaaJ:.aa&Jfciri»t"i-^i^-tsiA^JLgX.aa.^JL^jt.a^£^ — i
Fig. 871. — Vertical section of human cornea from near the margin. (Waldeyer.) Magnified. 1. Epithelium.
2. Anterior elastic lamina. 3. substantia propria. 4. Posterior elastic lamina. 5. Endothelium of the anterior
chamber, a. Oblique fibers in the anterior layer of the substantia propria, b. Lamellae the fibers of which are cut
across, producing a dotted appearance, c. Corneal corpuscles appearing fusiform in section, d. Lamellae the fibers
of which are cut longitudinally, e. Transition to the sclera, with more distinct fibrillation, and surmounted by a
thicker epithelium. /. Small bloodvessels cut across near the margin of the cornea.
The layer immediately beneath the corneal epithelium presents certain characteristics which
have led some anatomists to regard it as a distinct membrane, and it has been named the anterior
elastic lamina {lamina elastica anterior; anterior limiting layer; Bowman's membrane). It differs,
however, from the posterior elastic lamina, in presenting evidence of fibrillar structure, and in
not having the same tendency to curl inward, or to undergo fracture, when detached from the
other layers of the cornea. It consists of extremely closely interwoven fibrils, similar to those
found in the substantia propria, but contains no corneal corpuscles. It may be regarded as a
condensed part of the substantia propria.
The posterior elastic lamina (lamina elastica posterior; membrane of Descemet; membrane of
Demours) covers the posterior surface of the substantia propria, and is an elastic, transparent
homogeneous membrane, of extreme thinness, which is not rendered opaque by either water,
alcohol, or acids. When stripped from the substantia propria it curls up, or rolls upon itself
with the attached surface innermost.
At the margin of the cornea the posterior elastic lamina breaks up into fibers which form
the trabecular tissue already described; the spaces between the trabeculae are termed the
THE TUNICS OF THE EYE
1009
spaces of the angle of the iris {spaces of Fontana); they communicato with the sinus venosus
sclerae and with tlie anterior chamber at the filtration angle. Sonic of the fibers of this trabecular
tissue are continued into the substance of the iris, forming the pectinate ligament of the iris;
while others are connected with tlu> forepart of the sclera and choroid.
The endothelium of the anterior chamber {endothelium camera' anterioris; posterior layer;
corneal endothelium) covers the posterior surface of the elastic lamina, is reflected on to the
front of the iris, and also lines the spaces of the angle of the iris; it consists of a single stratum
of polygonal, flattened, nucleated cells.
Vessels and Nerves. — The cornea is a non- vascular structure; the capillary vessels ending in
loops at its circumference are derived from the anterior ciharv arteries. Lymphatic vessels have
not yet been demonstrated in it, but are
represented by the channels in which the
bundles of nerves run; these channels are
hned by an endothehum. The nerves are
numerous and are derived from the ciliary
nerves. Around the periphery of the cor-
nea they form an annular plexus, from
which fibers enter the substantia propria.
They lose their medullary sheaths and
ramify throughout its substance in a deli-
cate net-work, and their terminal filaments
form a firm and closer jilexus on the sur-
face of the cornea proper, beneath the
epithelium. This is termed the subepithe-
lial plexus, and from it fibrils are given off
which ramify between the epithelial cells,
forming an intraepithelial plexus.
The Vascular Tunic {tunica vascu-
losa oculi) (Figs. 872, 873, 874).—
The vascular tunic of the eye is
formed from behind forward by the
choroid, the ciliary body, and the iris.
The choroid invests the posterior
five-sixths of the bulb, and extends
as far forward as the ora serrata of
the retina. The ciliary body connects
the choroid to the circumference of
the iris. The iris is a circular diaphragm behind the cornea, and presents near
its center a rounded aperture, the pupil.
Anterior ciliary artery
Fig, 872. — The choroid and iria. (Enlarged.)
Short ciliary arteries
Anterior ciliary artery
Fig. 873.— The arteries of the choroid and iris. The greater part of the sclera has been removed. (Enlarged.)
The Choroid {cJwrioidea) .—The choroid is a thin, highly vascular membrane, of
a dark brown or chocolate color, investing the posterior five-sixths of the globe;
64
1010 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
it is pierced behind by the optic nerve, and in this situation is firmly adherent to
the sclera. It is thicker behind than in front. Its outer surface is loosely connected
by the lamina suprachorioidea with the sclera ; its inner surface is attached to the
pigmented layer of the retina.
Structure. — The choroid consists mainly of a dense capillary plexus, and of small arteries
and veins carrying blood to and returning it from this plexus. On its external surface is a thin
membrane the lamina suprachorioidea, composed of delicate non-vascular lamellae — each lamella
consisting of a net-work of fine elastic fibers among which are branched pigment cells. The spaces
between the lamellae are lined by endothelium, and open freely into the perichoroidal lymph
space, which, in its turn, communicates with the periscleral space by the perforations in the
sclera through which the vessels and nerves are transmitted.
Internal to this lamina is the choroid proper, consisting of two layers: an outer, composed
of small arteries and veins, with pigment cells interspersed between them; and an inner, consist-
ing of a capillary plexus. The outer layer {lamina vasculosa) consists, in part, of the larger branches
■ of the short ciliary arteries which run forward between the veins, before they bend inward to end
in the capillaries, but is formed principally of veins, named, from their arrangement, the venae
vorticosae. They converge to four or
five equidistant trunks, which pierce the
sclera about midway between the sclero-
corneal junction and the entrance of the
optic nerve. Interspersed between the
vessels are dark star-shaped pigment
cells, the processes of which, communicat-
ing with those of neighboring cells, form
a dehcate net-work or stroma, which
toward the inner surface of the choroid
loses its pigmentary character. The
inner layer {lamina choriocapillaris) con-
sists of an exceedingly fine capillary
plexus, formed by the short ciliary vessels;
the net-work is closer and finer in the pos-
terior than in the anterior part of the
choroid. About 1.25 cm. behind the
cornea its meshes become larger, and are
continuous with those of the ciliary
processes. These two laminae are con-
nected by a stratum intermedium con-
sisting of fine elastic fibers. On the inner
surface of the lamina choriocapillaris is
a very thin, structureless, or faintly
fibrous membrane, called the lamina basaUs; it is closely connected with the stroma of the
choroid, and separates it from the pigmentary layer of the retina.
One of the functions of the choroid is to provide nutrition for the retina, and to convey vessels
and nerves to the ciliary body and iris.
Tapetum. — This name is apphed to the outer and posterior part of the choroid, which in many
animals presents an iridescent appearance.
The Ciliary Body {corpiis ciliare). — The ciliary body comprises the orbiculus
ciliaris, the ciliary processes, and the Ciliaris muscle.
The orbiculus ciliaris is a zone of about 4 mm. in width, directly continuous
with the anterior part of the choroid; it presents numerous ridges arranged in a
radial manner (Fig. 875).
The ciliary processes {processus ciliares) are formed by the inward folding of the
various layers of the choroid, i. e., the choroid proper and the lamina basalis, and
are received between corresponding foldings of the suspensory ligament of the lens.
They are arranged in a circle, and form a sort of frill behind the iris, around the
margin of the lens (Fig. 875). They vary from sixty to eighty in number, lie side
by side, and may be divided into large and small; the former are about 2.5 mm.
in length, and the latter, consisting of about one-third of the entire number, are
situated in spaces between them, but without regular arrangement. They are
attached by their periphery to three or four of the ridges of the orbiculus ciliaris,
and are continuous with the layers of the choroid: their opposite extremities are
free and rounded, and are directed toward the posterior chamber of the eyeball and
Fig. 874. — The veins of the choroid. (Enlarged.)
THE TUNICS OF THE EYE
1011
circumference of the lens. In front, they are continuous with the periphery- of the
iris. Their posterior surfaces are connected with the suspensory ligament of the
lens.
Ora serrata
Pm f ciliaris retinw
Ciliary process
Orhiculus
ciliaris
Retina
Choroid
Sclera
Fig. 875. — Interior of anterior half of bulb of eve.
Structure. — The ciliary processes (Figs. 876, 877) are similar in structure to the choroid, but
the vessels are larger, and have chiefly a longitudinal direction. Their posterior surfaces are
covered by a bilaminar layer of black pigment cells,
which is continued forward from the retina, and is
named the pars ciliaris retinae. In the stroma of the
ciliary processes there are also stellate pigment cells, ^^^^^^/
but these are not so numerous as in the choroid itself.
According to Henderson the aqueous humor is a
secretion formed by the active intervention of the
epithelial cells lining the apices of the ciliary processes.^
The Ciliaris muscle {m. ciliaris; Bowman's
muscle) consists of unstriped fibers : it forms a
grayish, semitransparent, circular band, about
3 mm. broad, on the outer surface of the fore-
part of the choroid. It is thickest in front, and
consists of two sets of fibers, meridional and
circular. The meridional fibers, much the more
numerous, arise from the posterior margin of
the scleral spur (page 1007); they run back-
ward, and are attached to the ciliary processes
and orbiculus ciliaris. One bundle, according
to Waldeyer, is inserted into the sclera. The
circular fibers are internal to the meridional
ones, and in a meridional section appear as a
triangular zone behind the filtration angle and
close to the circumference of the iris. They
are well-developed in hypermetropic, but are
rudimentary or absent in myopic eyes. The
Ciliaris muscle is the chief agent in accom-
modation, i. e., in adjusting the eye to the vision of near objects. When it con-
tracts it draws forward the ciliary processes, relaxes the suspensory ligament of
the lens, and thus allows the lens to become more convex.
1 Henderson, T., Glaucoma, London, 1910.
Fig. 876. — Vessels of the choroid, ciliary pro-
cesses, and iris of a child. (Arnold.) Magnified
10 times, a. Capillary net-work of the posterior
part of the choroid, ending at h, the ora serrata.
c. Arteries of the corona ciliaris, supplying the
ciliary processes, d, and passing into the iris e.
f. The capillary net-work clo.se to the pupillary
margin of the iris.
1012 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
The Iris. — The iris has received its name from its various colors in different
individuals. It is a thin, circular, contractile disk, suspended in the aqueous
humor between the cornea and lens, and perforated a little to the nasal side qf its
center by a circular aperture, the pupil. By its periphery it is continuous with
the ciliary body, and is also connected with the posterior elastic lamina of the
'iff
Cornea
Lens
Fig. 877. — Diagram of the bloodvessels of the eye, as seen in a horizontal section. (Leber, after Stohr.)
Course of vasa centralia retinae: a. Arteria. a.' Vena centralis retinse. b. Anastomosis with vessels of outer coats.
c. Anastomosis with branches of short posterior ciliary arteries, d. Anastomosis with chorioideal vessels.
Course of vasa ciliar. postic. brev. : I. Arterisp, and Ii. 'V'ensB ciliar. postic. brev. II. Episcleral artery. IIi. Episcleral
vein. III. Capillaries of lamina choriocapillaris.
Course of vasa ciliar. postic. long.: 1. a. ciliar. post, longa. 2. Circulus iridis major cut acrcss. 3. Branches tociliary
body. 4. Branches to iris.
Course of vasa ciliar. ant.: a. Arteria. ai. Vena ciliar. ant. h. Junction with the circulus iridis major, r. Junction
with lamina choriocapill. d. Arterial, and rfi. Venous episcleral branches, f. Arterial, andu. Venous branches to
conjunctiva sclerae. /. Arterial, and/i. Venous branches to corneal border. V. Vena vorticosa. S. Transverse section
of sinus venosus sclera.
cornea by means of the pectinate ligament; its surfaces are flattened, and look
forward and backward, the anterior toward the cornea, the posterior toward the
ciliary processes and lens. The iris divides the space between the lens and the
cornea into an anterior and a posterior chamber. The anterior chamber of the eye
is bounded in front by the posterior surface of the cornea; behind by the front of
the iris and the central part of the lens. The posterior chamber is a narrow chink
THE TUNICS OF THE EYE 1013
behind the peripheral part of the iris, and in front of the suspensory ligament
of the lens and the ciliary processes. In the adult the two chambers communi-
cate through the pupil, but in the fetus up to the seventh month they are sei)ar-
ated by the membrana pupillaris.
Structure. — The iris is composed of the following structures:
1. In front is a layer of flattened endothelial cells placed on a delicate hyaline basement mem-
brane. This layer is continuous with the endothelium covering the posterior elastic lamina of
the cornea, and in individuals with dark-colored irides the cells contain pigment granules.
2. The stroma (stroma iridis) of the iris consists of fibers and cells. The former are made up
of delicate bundles of fibrous tissue; a few fibers at the circumference of the iris have a circular
direction; but the majority radiate toward the pupil, forming by their interlacement, delicate
meshes, in which the vessels and nerves are contained. Interspersed between the bundles of
connective tissue are numerous branched cells with fine processes. In dark eyes many of them
contain pigment granules, but in blue eyes and the eyes of albinos they are unpigmented.
3. The muscular fibers are involuntary, and consist of circular and radiating fibers. The
circular fibers form the Sphincter pupilla?; they are arranged in a narrow band about 1 mm. in
width which surrounds the margin of the pupil toward the posterior surface of the iris; those
near the free margin are closely aggregated ; those near the periphery of the band are somewhat
separated and form incomplete circles. The radiating fibers form the Dilatator pupiUa'; they
converge from the circumference toward the center, and blend with the circular fibers near the
margin of the pupil.
ANTERIOR CILIARY ARTERIES
LONG CILIARY
i ARTERV
ANTERIOR CILIARY ARTERIES
Fig. 878. — Iris, front view.
. 4. The posterior surface of the iris is of a deep purple tint, being covered by two layers of
I pigmented columnar epithelium, continuous at the periphery of the iris with the pars ciharis
retinjB. This pigmented epithelium is named the pars iridica retinae, or, from the resemblance
of its color to that of a ripe grape, the uvea.
The color of the iris is produced by the reflection of light from dark pigment ceUs underlying
a translucent tissue, and is therefore determined by the amount of the pigment and its distribu-
tion throughout the texture of the iris. The number and the situation of the pigment cells differ
in different irides. In the albino pigment is absent; in the various shades of blue eyes the pigment
cells are confined to the posterior surface of the iris, whereas in gray, brown, and black eyes
pigment is found also in the cells of the stroma and in those of the endothelium on the front of
the iris.
The iris may be absent, either in part or altogether as a congenital condition, and in some
instances the pupillary membrane may remain persistent, though it is rarely complete. Again,
the iris may be the seat of a malformation, termed coloboma, which consists in a deficiency or
1
1014 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
cleft, clearly due in a great number of cases to an arrest in development. In these cases the
cleft is found at the lower aspect, extending directly dowTiward from the pupil, and the gap
frequently extends through the choroid to the porus opticus. In some rarer cases the gap is
found in other parts of the iris, and is not then associated with any deficiency of the choroid.
Vessels and Nerves. — The arteries of the iris are derived from the long and anterior ciliary
arteries, and from the vessels of the ciliary processes (see p. 571). Each of the two long ciliary
arteries, having reached the attached margin of the iris, divides into an upper and lower branch;
these anastomose with corresponding branches from the opposite side and thus encircle the iris;
into this vascular circle {circylus arteriosus major) the anterior ciliary arteries pour their blood,
and from it vessels converge to the free margin of the iris, and there communicate and form a
second circle (circulus arteriosus minor) (Figs. 877 and 878).
The nerves of the choroid and iris are the long and short ciliary; the former being branches
of the nasociliary nerve, the latter of the cihary ganghon. They pierce the sclera around the
entrance of the optic nerve, run forward in the perichoroidal space, and supply the bloodvessels
of the choroid. After reaching the iris they form a plexus around its attached margin; from this
are derived non-medullated fibers which end in the Sphincter and Dilatator pupillse; their exact
mode of termination has not been ascertained. Other fibers from the plexus end in a net-work
on the anterior surface of the iris. The fibers derived through the motor root of the ciliary ganglion
from the oculomotor nerve, supply the Sphincter, while those derived from the sympathetic supply
the Dilatator.
Membrana Pupillaris. — In the fetus, the pupil is closed by a delicate vascular
membrane, the membrana pupillaris, which divides the space in which the iris is
suspended into two distinct chambers. The vessels of this membrane are partly
derived from those of the margin of the iris and partly from those of the capsule
of the lens; they have a looped arrangement, and converge toward each other with-
out anastomosing. About the sixth month the membrane begins to disappear
by absorption from the center toward the circumference, and at birth only a few
fragments are present; in exceptional cases it persists.
Optic disc
Macula Iviea
Sclera
Choroid
Retina
Fic' 879.— Interior of posterior half of bulb of left eye. The veins are darker in appearance than the arteries.
The Retina {tunica interna).— The retina is a delicate nervous membrane, upon
which the images of external objects are received. Its outer surface is m contact
with the choroid; its inner with the hyaloid membrane of the vitreous body. Be-
hind it is continuous with the optic nerve; it gradually diminishes in thickness
from' behind forward, and extends nearly as far as the ciliary body, where it appears
to end in a jagged margin, the ora serrata. Here the nervous tissues of the retina
-end but a thin prolongation of the membrane extends forward over the back ot
THE TUNICS OF THE EYE
1015
the ciliary processes and iris, forming the pars ciliaris retinae and pars iridica retinae
already referred to. This forward prolongation consists of the pigmentary layer
of the retina together with a stratnm of cohimnar epithelium. The retina is soft,
semitransparent, and of a purple tint in the fresh state, owing to the presence of a
coloring material named rhodopsin or visual purple; but it soon becomes clouded,
opaque, and bleached when exposed to sunlight. Exactly in the center of the
posterior part of the retina, corresponding to the axis of the eye, and at a point
in which the sense of vision is most perfect, is an oval yellowish area, the macula
lutea; in the macula is a central depression, the fovea centralis (Fig. 879). At the
fovea centralis the retina is exceedingly thin, and the dark color of the choroid is
distinctly seen through it. About 3 mm. to the nasal side of the macula hit*
is the entrance of the optic nerve (optic disk), the circumference of which is slightly
raised to form an eminence {colliculus nervi opiici) (Fig. 880) ; the arteria centralis
retina? pierces the center of the disk. This is the only part of the surface of the
retina which is insensitive to light, and it is termed the blind spot.
Lamina crihmsa Colliculus nervi optiei
of sclera
Retina
Choroid
Sclera
Posterior
short ciliary
artery and
vein
Pial sheath "^\
Arachnoid
sheath
Dural sheath
Intervaginal space.
Bu tidies of
optic nerve
Central artery and
vein of retina
Fig. 8S0. — The terminal i)ortion of the optic nerve and its entrance into the eyeball, in horizontal section. (Toldt.)
Structure (Figs. 881, 882). — The retina consists of an outer pigmented layer and an inner
nervous stratum or retina proper.
The pigmented layer consists of a single stratimi of cells. When viewed from the outer surface
these cells are smooth and hexagonal in shape; when seen in section each ceU consists of an outer
non-pigmented part containing a large oval nucleus and an inner pigmented portion which extends
as a series of straight thread-like processes between the rods, this being especially the case when
the eye is exposed to light. In the eyes of albinos the cells of this layer are destitute of pigment.
Retina Proper. — The nervous structures of the retina proper are supported by a series of non-
nervous or sustentacular fibers, and, when examined microscopically by means of sections made
perpendicularly to the surface of the retina, are found to consist of seven layers, named from
within outward as follows:
1. Stratum opticum.
2. Ganglionic layer.
3. Inner plexiform layer.
4. Inner nuclear layer, or layer of inner granules.
5. Outer plexiform layer.
6. Outer nuclear layer, or layer of outer granules.
7. Layer of rods and cones.
1. The stratiun opticum or layer of nerve fibers is formed by the expansion of the fibers of the
optic nerve; it is thickest near the porus opticus, gradually diminishing toward the ora serrata.
1016 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
As the nerve fibers pass through the lamina cribrosa sclerse they loFe their medullary sheaths
and are continued onward through the choroid and retina as simple axis-cyhnders. When they
reach the internal surface of the retina they radiate from their point of entrance over this sur-
face grouped in bundles, and in many places arranged in plexuses. Most of the fibers are
centripetal, and are the direct continuations of the axis-cylinder processes of the cells of the
ganglionic layer, but a few of them
Memhrana limitans
^ — interna
'/:-'' YS^Stratum opticum
Fibers of Muller
are centrifugal and ramify in the
inner plexiform and inner nuclear
layers, where they end in enlarged
extremities.
2. The ganglionic layer consists
of a single layer of large ganglion
cells, except in the macula lutea,
where there are several strata. The
cells are somewhat flask-shaped; the
rounded internal surface of each
resting on the stratum opticum, and
sending off an axon which is pro-
longed into it. From the opposite
end numerous dendrites extend into
the inner plexiform layer, where
they branch and form flattened
arborizations at different levels.
The ganglion cells vary much in
size, and the dendrites of the smaller ones as a rule arborize in the inner plexiform layer as soon
as they enter it; while those of the larger cells ramify close to the inner nuclear layer.
3. The inner plexiform layer is made up of a dense reticulum of minute fibrils formed by the
interlacement of the dendrites of the ganglion cells with those of the cells of the inner nuclear
layer; within this reticulum a few branched spongioblasts are sometimes imbedded.
Jilewbrana
limitans interna —
Stratum opticum —
Ga ngl ion ic layer--
r^i Ganglionic layer
. Inner plexiform layer
Inner nuclear layer
Outer plexiform layei
^ Outer nuclear layer
Memhrana limitans
externa
Layer of rods and
cones
.Pigmented layer
Fig. 881. — Section of retina. (Magnified.)
Inner plexiform ...^
layer
Centrifugal fibre ''
Inner nuclear
layer
Fibre of Mailer -
Outer plexiform ..A
layer '
Outer nxiclear
layer
Membrana
limitans externa
Layer of rods
and cones
Diffuse amacrine
cell
-.Amacrine cells
■> Horizontal cell
7 Rod granules
.--■ ----- --—" Cone granules
o I' o' t' Piotnented layer
Fig. 882. — Plan of retinal neurons. (After Cajal.)
4. The inner nuclear layer or layer of inner granules is made up of a number of closely packed
cells, of which there are three varieties, viz. : bipolar cells, horizontal cells, and amacrine cells.
The bipolar cells, by far the most numerous, are round or oval in shape, and each is prolonged
into an inner and an outer process. They are divisible into rod bipolars and cone bipolars. The
THE TUNICS OF THE EYE 1017
inner processes of the rod bipolars run through the inner plexiform layer and arborize around
the bodies of the cells of the ganglionic layer; their outer processes end in the outer plexiform
layer in tufts of fibrils around the button-like ends of the inner processes of the rod granules.
The inner processes of the cone bipolars ramify in the inner plexiform layer in contact with the
dendrites of the ganglionic cells.
The horizontal cells Ue in the outer part of the inner nuclear layer and possess somewhat
flattened cell bodies. Their dendrites divide into numerous branches in the outer plexiform
layer, while their axons run horizontally for some distance and finally ramify in the same layer.
The amacrine cells are placed in the inner part of the inner nuclear layer, and are so named
because they have not yet been shown to possess axis-cylinder processes. Their dendrites undergo
extensive ramification in the inner plexiform layer.
5. The outer plexiform layer is much thinner than the inner; but, like it, consists of a dense
net-work of minute fibrils derived from the processes of the horizontal cells of the preceding layer,
and the outer processes of the rod and cone bipolar granules, which ramify in it, forming arboriza-
tions around the enlarged ends of the rod fibers and with the branched foot plates of the cone
fibers.
6. The outer nuclear layer or layer of outer granules, like the inner nuclear layer, contains
several strata of oval nuclear bodies; they are of two kinds, viz.: rod and cone granules, so
named on account of their being respectively connected with the rods and cones of the next layer.
The rod granules are much the more numerous, and are placed at different levels throughout
the layer. Their nuclei present a pecuhar cross-striped appearance, and prolonged from either
extremity of each cell is a fine process; the outer process is continuous with a single rod of the
layer of rods and cones; the inner ends in the outer plexiform layer in an enlarged extremity, and
is imbedded in the tuft into which the outer processes of the rod bipolar cells break up. In its
course it presents numerous varicosities. The cone granules, fewer in number than the rod
granules, are placed close to the membrana limitans externa, through which they are continuous
with the cones of the layer of rods and cones. They do not present any cross-striation, ,but con-
tain a pyriform nucleus, which almost completely fills the cell. From the inner extremity of the
granule a thick process passes into the outer plexiform layer, and there expands into a pyramidal
enlargement or foot plate, from which are given off numerous fine fibrils, that come in contact
with the outer processes of the cone bipolars.
7. The Layer of Rods and Cones {Jacob's membrane). — The elements composing this layer are
of two kinds, rods and cones, the former being much more numerous than the latter except in
the macula lutea. The rods are cylindrical, of nearly uniform thickness, and are arranged per-
pendicularly to the surface. Each rod consists of two segments, an outer and inner, of about
equal lengths. The segments differ from each other as regards refraction and in their behavior
toward coloring reagents; the inner segment is stained by carmine, iodine, etc.; the outer segment
is not stained by these reagents, but is colored yellowish brown by osmic acid. The outer segment
is marked by transverse striae, and tends to break up into a number of thin disks superimposed
on one another; it also exhibits faint longitudinal markings. The deeper part of the inner seg-
ment is indistinctly granular; its more superficial part presents a longitudinal striation, being
composed of fine, bright, highly refracting fibrils. The visual purple or rhodopsin is found only
in the outer segments.
The cones are conical or flask-shaped, their broad ends resting upon the membrana limitans
externa, the narrow-pointed extremity being turned to the choroid. Like the rods, each is made
up of two segments, outer and inner; the outer segment is a short conical process, which, hke
the outer segment of the rod, exhibits transverse striae. The inner segment resembles the inner
segment of the rods in structure, presenting a superficial striated and deep granular part, but
differs from it in size and shape, being bulged out laterally and flask-shaped. The chemical
and optical characters of the two portions are identical with those of the rods.
Supporting Frame-work of the Retina. — The nervous layers of the retina are connected together
by a supporting frame-work, formed by the sustentacular fibers of MiiUer; these fibers pass
through all the nervous layers, except that of the rods and cones. Each begins on the inner surface
of the retina by an expanded, often forked base, which sometimes contains a spheroidal body
staining deeply with hematoxylin, the edges of the bases of adjoining fibers being united to form
the membra;na limitans interna. As the fibers pass through the nerve fiber and ganghonic layers
they give off a few lateral branches; in the inner nuclear layer they give off numerous lateral
processes for the support of the bipolar cells, while in the outer nuclear layer they form a net-
work around the rod- and cone-fibrils, and unite to form the membrana limitans externa at the
bases of the rods and cones. At the level of the inner nuclear layer each sustentacular fiber
contains a clear oval nucleus.
Macula Lutea and Fovea Centralis. — In the macula lutea the nerve fibers are wanting as a
continuous layer, the ganglionic layer consists of several strata of cells, there are no rods, but
only cones, which are longer and narrower than in other parts, and in the outer nuclear layer
there are only cone-granules, the processes of which are very long and arranged in curved hnes.
In the fovea centrahs the only parts present are (1) the cones; (2) the outer nuclear layer, the
1018 ORGAXS OF THE SENSES AND THE COMMON INTEGUMENT
cone-fibers of which are ahnost horizontal in direction; (3) an exceedingly thin inner plexiform
layer. The pigmented layer is thicker and its pigment more pronounced than elsewhere. The
color of the macula seems to imbue all the layers except that of the rods and cones; it is of a rich
yellow, deepest toward the center of the macula, and does not appear to be due to pigment cells,
but simply to a staining of the constituent parts.
At the ora serrata the nervous layers of the retina end abruptly, and the retina is continued
onward as a single layer of columnar cells covered by the pigmented layer. This double laj'er is
known as the pars ciliaris retinae, and can be traced forward from the ciliary processes on to the
back of the iris, where it is termed the pars iridica retinae or uvea.
The arteria centralis retinae (Fig. 879) and its accompanying vein pierce the optic nerve, and
enter the bulb of the eye through the porus opticus. The artery immediately bifurcates into
an upper and a lower branch, and each of these again divides into a medial or nasal and a lateral
or temporal branch, which at first run between the hyaloid membrane and the nervous laj'er;
but they soon enter the latter, and pass forward, dividing dichotomouslj-. From these branches
a minute capillary plexus is given off, which does not extend beyond the inner nuclear lajer.
The macula receives two small branches (superior and inferior macular arteries) from the tem-
poral branches and small twigs directly from the central artery; these do not, however, reach
as far as the fovea centraUs, which has no bloodvessels. The branches of the arteria centrahs
retina^ do not anastomose with each other^in other words they are terminal arteries. In the
fetus, a small vessel, the arteria hyaloidea, passes forward as a continuation of the arteria centralis
retinae through the vitreous humor to the posterior surface* of the capsule of the lens.
The Refracting Media.
The refracting media are three, viz. : '
Aqueous humor. Vitreous body. Crystalline lens.
The Aqueous Humor {humor aqueus). — The aqueous humor fills the anterior
and posterior chambers of the eyeball. It is small in quantity, has an alkaline
reaction, and consists mainly of water, less than one-fiftieth of its weight being
solid matter, chiefly chloride of sodium.
The Vitreous Body (corpus vitreum). — The vitreous body forms about four-
fifths of the bulb of the eve. It fills the concavitv of the retina, and is hollowed
in front, forming a deep concavity, the hyaloid fossa, for the reception of the lens.
It is transparent, of the consistence of thin jelly, and is composed of an albuminous
fluid enclosed in a delicate transparent membrane, the hyaloid membrane. It has
been supposed, by Hannover, that from its surface numerous thin lamella? are
prolonged inward in a radiating manner, forming spaces in which the fluid is con-
tained. In the adult, these lamellae cannot.be detected even after careful micro-
scopic examination in the fresh state, but in preparations hardened in weak chromic
acid it is possible to make out a distinct lamellation at the periphery of the body.
In the center of the vitreous body, running from the entrance of the optic nerve
to the posterior surface of the lens, is a canal, the hyaloid canal, filled with lymph
and lined by a prolongation of the hyaloid membrane. This canal, in the embryonic
vitreous bodv, conveved the arteria hvaloidea from the central arterv of the retina
to the back of the lens. The fluid from the vitreous body is nearly pure water; it
contains, however, some salts, and a little albumin.
The hyaloid membrane envelopes the vitreous body. The portion in front of the
ora serrata is thickened by the accession of radial fibers and is termed the zonula
ciliaris {zonule of Zinn). Here it presents a series of radially arranged furrows,
in which the ciliary processes are accommodated and to which they adhere, as is
shown by the fact that when they are removed some of their pigment remains
attached to the zonula. The zonula ciliaris splits into two layers, one of which
is thin and lines the hyaloid fossa; the other is named the suspensory ligament
of the lens: it is thicker, and passes over the ciliary body to be attached to the cap-
sule of the lens a short distance in front of its equator. Scattered and delicate
fibers are also attached to the region of the equator itself. This ligament retains
the lens in position, and is relaxed by the^ contraction of the meridional fibers of
the Ciliaris muscle, so that the lens is allowed to become more convex. Behind
THE REFRACTING MEDIA
1019
the suspensory ligament there is a sacculated canal, the spatia zonularis {canal
ofFetit) which encircles the equator of the lens; it can he easily inflated through
a line blowpipe inserted under the suspensory ligament.
No bloodyessels penetrate the vitreous body"; so that its nutrition must be carried
on by vessels ot the retina and ciliary processes, situated upon its exterior.
INSERTION OF
TENDON OFSUPERIOR_
RECTUS MUSCLE
PTICA
ATA
PAHS CILIARIS RETINJE
ANTERIOR CILIARY
ARTERI ES AND
VEINS
CIRCULAR
MAJOR
\
ANGLE OF
ANTERIOR
CHAMBER
CANAL OF iv,'>''/
SCHLEMM
POSTERIOR
SURFACE
OF CORNEA
EPITHELIUM —
OF CORNEA
ANTERIOR-
ELASTIC
LAMINA
CONJUNCTIVA
EPISCLERAL
CONNECTIVE-
TISSUE
LIGAMENTUM
PECTINATUM
IRIDIS
RIMA
COR
EDG
COR
IRIS (
i:or surfacL)
CORTICAL SUBSTANCE
OF LENS
POSTERIOR ELASTIC
LAMINA
SPHINCTER
OF PUPIL
ROMA OF IRIS
PIGMENTARY
LAYERS OF IRIS
Fig. 883. — -The upper half of a sagittal section through the front of the eyeball.
The Crystalline Lens {lens crystaUina). — The crystalline lens, enclosed in its
capsule, is situated immediately behind the iris, in front of the vitreous body,
and encircled by the ciliary processes, which slightly overlap its margin.
The capsule of the lens (capsula lentis) is a transparent, structureless membrane
which clo.sely surrounds the lens, and is thicker in front than behind. It is brittle
but highly elastic, and when ruptured the edges roll up with the outer surface
innermost. It rests, behind, in the hyaloid fossa in the forepart of the vitreous
body; in front, it is in contact with the free border of the iris, but recedes from it
at the circumference, thus forming the posterior chamber of the eye; it is retained
in its position chiefly by the suspensory ligament of the lens, already described.
The lens is a transparent, biconvex body, the convexity of its anterior being
less than that of its posterior surface. The central points of these surfaces are
termed respectively the anterior and posterior poles; a line connecting the poles
constitutes the axis of the lens, while the marginal circumference is termed the
equator.
1020 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
Structure. — The lens is made up of soft cortical substance and a firm, central part, the nucleus
(Fig. 884). Faint lines (radii lentis) radiate from the poles to the equator. In the adult there
may be six or more of these lines, but in the fetus they are only
three in number and diverge from each other at angles of 120°
(Fig. 885) ; on the anterior sui-f ace one line ascends vertically
and the other two diverge downward; on the posterior sur-
face one ray descends vertically and the other two diverge
upward. They correspond with the free edges of an equal
number of septa composed of an amorphous substance, which
dip into the substance of the lens. When the lens has been
hardened it is seen to consist of a series of concentrically
arranged laminae, each of which is interrupted at the septa
referred to. Each lamina is built up of a number of hexagonal,
ribbon-like lens fibers, the edges of which are more or less ser-
rated— the serrations fitting between those of neighboring
fibers, while the ends of the fibers come into apposition at
the septa. The fibers run in a curved manner from the septa
on the anterior surface to those on the posterior surface.
No fibers pass from pole to pole; they are arranged in such
a way that those which begin near the pole on one surface
FlQ. 884. — The crystalline lens, hardened and divided. (Enlarged.)
A. B.
Fig. 885. — -Diagram to show tlie direction and arrangement of the
radiating lines on the front and baclc of the fetal lens. A. From the
front. B. From the back.
Fig. 887. — Section through the margin
i?,^ OCR r> CI • « ^L 1 . !.,» . , of the lens, showing the transition of
i'lG. 88b— ITofale views of the lena at different periods of life. the epithelium into the lens fibers.
1. In the fetus. 2. In adult life. .3 In old age. (Babuchin.)
of the lens end near the peripheral extremity of the plane on the other, and vice versa. The
fibers of the outer layers of the lens are nucleated, and together form a nuclear layer, most
distinct toward the equator. The anterior surface of the lens is covered by a layer of transparent,
columiiar, nucleated epithelium. At the equator the cells become elongated, and their gradual
transition into lens fibers can be traced (Fig. 887).
THE ACCESSORY ORGANS OF THE EYE
1021
In the fetus, the lens is nearly spherical, and has a slightly reddish tint; it is soft and breaks
down readily on the slightest pressure. A small branch from tlie art(>ria centrahs retime runs
forward, as already mentioned, through the vitreous body to the posterior part of the capsule
of the lens, where its branches radiate and form a plexiform network, which covers the posterior
surface of the capsule, and they are continuous around the margin of the capsule with the vessels
of the pupillary membrane, and with those of the iris. In the adult, the lens is colorless, trans-
parent, firm in texture, and devoid of vessels. In old age it becomes flattened on both surfaces,
sUghtly opaque, of an amber tint, and increased in density (Fig. 886).
Vessels and Nerves.— The arteries of the bulb of the eye are the long, short, and anterior
cihary arteries, and the arteria centralis retina. They have already been described (see p. 571).
The ciliary veins are seen on the outer surface of the choroid, and are named, from their arrange-
ment, the venae vorhcosa;; they converge to four or five equidistant trunks which pierce the
sclera midway between the -sclero-corneal junction and the porus opticus. Another set of veins
accompanies the anterior ciliary arteries. All of these veins open into the ophthalmic veins.
The ciliary nerves are derived from the nasocihary nerve and from the ciliary ganglion.
The Accessory Organs of the Eye (Organa Oculi Accessoria).
The accessory organs of the eye include the ocular muscles, the fasciae, the eye-
brows, the eyelids, the conjunctiva, and the lacrimal apparatus.
The Ocular Muscles (musculi ocwii).— The ocuhir muscles are the:
Levator palpebn^ superioris. Rectus medialis.
Rectus superior. Rectus lateralis.
Rectus inferior. Obliquus superior.
Obliquus inferior.
Tendon of Obliquus superior
Orbital plate of frontal bone
Levator palpehrce superioris
Rectus superior
Orbicularis ocidi
Optic nerve
Rectus inferior
Roof of maxillary sinus
Obliquus inferior
\WI^^ 'Superior tarsus
Upper eyelid
Lower eyelid
^ Inferior tarsus
Orbicularis ocidi
Fig. 888. — Sagittal section of right orbital cavity.
The Levator palpebrse superioris (Fig. 888) is thin, flat, and triangular in shape.
It arises from the under surface of the small wing of the sphenoid, above and in
front of the optic foramen, from which it is separated by the origin of the Rectus
superior. At its origin, it is narrow and tendinous, but soon becomes broad and
fleshy, and ends anteriorly in a wide aponeurosis which splits into three lamellae.
The superficial lamella blends with the upper part of the orbital septum, and is pro-
longed forward above the superior tarsus to the palpebral part of the Orbicularis
oculi, and to the deep surface of the skin of the upper eyelid. The middle lamella,
largely made up of non-striped muscular fibers, is inserted into the upper margin
of the superior tarsus, while the deepest lamella blends with an expansion from
the sheath of the Rectus superior and with it is attached to the superior fornix
of the conjunctiva.
1022 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
Whitnall' has pointed out that the upper part of the sheath of the Levator palpebral becomes
thickened in front and forms, above the anterior part of the muscle, a transverse Hgamentous
band which is attached to the sides of the orbital cavity. On the medial side it is mainly fixed
to the pulley of the Obliquus superior, but some fibers are attached to the bone behind the pulley
and a slip passes forward and bridges over the supraorbital notch; on the lateral side it is fixed
to the capsule of the lacrimal gland and to the frontal bone. In front of the transverse ligament-
ous band the sheath is continued over the aponeurosis of the Levator palpebriE, as a thin con-
nective-tissue layer which is fixed to the upper orbital margin immediatly behind the attach-
ment of the orbital septum. When the Levator palpebrte contracts, the lateral and medial parts
of the ligamentous band are stretched and check the action of the muscle; the retraction of the
upper eyelid is checked also by the orbital septum coming into contact with the transverse part
of the ligamentous band.
Pig. 889. — Muscles of the right orbit.
The four Recti (Fig. 889) arise from a fibrous ring {annidits taidineus communis)
which surrounds the upper, medial, and h)wer margins of the optic foramen and
encircles the optic nerve (Fig. 890). The ring is completed by a tendinous bridge
prolonged over the lower and medial part of the superior orbital fissure and attached
to a tubercle on the margin of the great wing of the sphenoid, bounding the fissure.
Two specialized parts of this fibrous ring may be made out: a lower, the ligament
or tendon of Zinn, which gives origin to the llectus inferior, part of the Rectus in-
ternus, and the lower head of origin of the Rectus lateralis; and an upper, which
gives origin to the Rectus superior, the rest of the Rectus medialis, and the upper
head of the Rectus lateralis. This upper band is sometimes termed the superior
tendon of Lockwood. Each muscle passes forward in the position implied by its
name, to be inserted by a tendinous expansion into the sclera, about G mm. from the
margin of the cornea. Between the two heads of the Rectus lateralis is a narrow
interval, through Avhich pass the two divisions of the oculomotor nerve, the naso-
ciliary nerve, the abducent nerve, and the ophthalmic vein. Although these
muscles present a common origin and are inserted in a similar manner into the
sclera, there are certain differences to be observed in them as regards their length
and breadth. The Rectus medialis is the broadest, the Rectus lateralis the longest,
and the Rectus superior the thinnest and narrowest.
The Obliquus oculi superior {superior oblicpie) is a fusiform muscle, placed at the
upper and medial side of the orbit. It arises immediately above the margin of the
optic foramen, above and medial to the origin of the Rectus superior, and, passing
forward, ends in a rounded tendon, which plays in a fibrocartilaginous ring or pulley
attached to the trochlear fovea of the frontal bone. The contiguous surfaces of
the tendon and ring are lined by a delicate mucous sheath, and enclosed in a thin
1 Journal of Anatomy and Physiology, vol. xlv.
THE ACCESSORY ORGANS OF THE EYE
1023
fibrous investment. The tendon is reflected backward, laterahvard, and downward
laeneath the Rectus superior to the lateral part of the bulb of the eye, and is inserted
into the sclera, behind the equator of the eyeball, the insertion of the muscle lying
between the Rectus superior and Rectus lateralis.
The Obliquus oculi inferior (inferior oblique) is a thin, narrow muscle, placed near
the anterior margin of the floor of the orbit. It arises from the orbital surface of
the maxilla, lateral to the lacrimal groove. Passing laterahvard, backward, and
upward, at first between the Rectus inferior and the floor of the orbit, and then
between the bulb of the eye and the Rectus lateralis, it is inserted into the lateral
part of the sclera between the Rectus superior and Rectus lateralis, near to, but
somewhat behind the insertion of the Obliquus superior.
Frontal nerve
Sup. ramtof of oculomotor nerve
Sup. orbital fissure
Lacrimal nerve
Levator palpebrw super,
j Nasociliary nerve
Trocldear nerve
Trochlea
Abducent nerve
Inf. ramus of oculomotor Inf. orbital Optic foramen
nerve fissure
Fi<5. 890. — Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.
Nerves. — The Levator palpebrae superioris, Obliquus inferior, and the Recti superior, inferior,
and medialis are supphed by the oculomotor nerve; the ObHquus superior, by the trochlear
nerve; the Rectus laterahs, by the abducent nerve.
Actions. — The Levator palpebr£s raises the upper eyeUd, and is the direct antagonist of the
Orbicularis ocali. The four Recti are attached to the bulb of the eye in such a manner that,
acting singly, they will tiu-n its corneal surface either upward, downward, medialward, or lateral-
ward, as expressed by their names. The movement produced by the Rectus superior or Rectus
inferior is not quite a simple one, for inasmuch as each passes obhquely lateralward and forward
to the bulb of the eye, the elevation or depression of the cornea is accompanied by a certain
deviation medialward, with a slight amount of rotation. These latter movements are corrected
by the Obhqui, the Obliquus inferior correcting the medial deviation caused by the Rectus superior
and the Obliquus superior that caused by the Rectus inferior. The contraction of the Rectus
laterahs or Rectus medialis, on the other hand, produces a purely horizontal movement. If any
two neighboring Recti of one eye act together they carry the globe of the eye in the diagonal of
these directions, viz., upward and medialward, upward and lateralward, downward and medial-
ward, or downward and lateralward. Sometimes the corresponding Recti of the two eyes act
in unison, and at other times the opposite Recti act together. Thus, in turning the eyes to the
right, the Rectus laterahs of the right eye will act in imison with the Rectus mediahs of the left
eye; but if both eyes are directed to an object in the middle line at a short distance, the two Recti
mediales will act in unison. The movement of circumduction, as in looking around a room, is
performed by the successive actions of the four Recti. The Obhqui rotate the eyeball on its
antero-posterior axis, the superior directing the cornea downward and lateralward, and the
1024 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
inferior directing it upward and lateralward; these movenaents are required for the correct viewing
of an object when the head is moved laterally, as from shoulder to shoulder, in order that the
picture may fall in all respects on the same part of the retina of either eye.
A layer of non-striped muscle, the Orbitalis muscle of H. jMiiller, may be seen
bridging across the inferior orbital fissure.
Oplic yierve —
Fascia bulb i -
i;pr\- Cornea
{h J — Superior tarsus
Inferior tarsus
Fig. 891. — The right eye in sagittal section, showing the fascia bulbi (semidiagrammatic). (Testut.)
The Fascia Bulb (capsule of Tenon) (Fig. 891) is a thin membrane which envelops
the bulb of the eye from the optic nerve to the ciliary region, separating it from
the orbital fat and forming a socket in which it plays. Its inner surface is smooth,
arid is separated from the outer surface of the sclera by the periscleral lymph space.
This lymph space is continuous with the subdural and subarachnoid cavities,
and is traversed by delicate bands of connective tissue which extend between the
fascia and the sclera. The fascia is perforated behind by the ciliary vessels and
nerves, and fuses with the sheath of the optic nerve and with the sclera around the
entrance of the optic nerve. In front it blends with the ocular conjunctiva, and
with it is attached to the ciliary region of the eyeball. It is perforated by the
tendons of the ocular muscles, and is reflected backward on each as a tubular
sheath. The sheath of the Obliquus superior is carried as far as the fibrous pulley
of that muscle; that on the Obliquus inferior reaches as far as the floor of the
orbit, to which it gives off a slip. The sheaths on the Recti are gradually lost in
the perimysium, but they give off important expansions. The expansion from the
Rectus superior blends with the tendon of the Levator palpebne; that of the
Rectus inferior is attached to the inferior tarsus. The expansions from the sheaths
of the Recti lateralis and medialis are strong, especially that from the latter muscle,
and are attached to the lacrimal and zygomatic bones respectively. As they prob-
ably check the actions of these two Recti they have been named the medial and
lateral check ligaments. Lockwood has described a thickening of the lower part
THE ACCESSORY ORGANS OF THE EYE 1025
of the facia bulbi, wliich he has named the suspensory ligament of the eye. It is
slung like a hammock below the eyeball, being expanded in the center, and narrow
at its extremities which are attached to the zygomatic and lacrimal bones
respectively.^
The Orbital Fascia forms the periosteum of the orbit. It is loosely connected
to the bones and can be readily separated from them. Behind, it is united with
the dura mater by processes which pass through the optic foramen and superior
orbital fissure, and with the sheath of the optic nerve. In front, it is connected
with the periosteum at the margin of the orbit, and sends off a process which
assists in forming the orbital septum. From it two processes are given off; one to
enclose the lacrimal gland, the other to hold the pulley of the Obliquus superior in
position .
The Eyebrows {supercilia) are two arched eminences of integument, which sur-
mount the upper circumference of the orbits, and support numerous short, thick
hairs, directed obliquely on the surface. The eyebrows consist of thickened integu-
ment, connected beneath with the Orbicularis oculi, Corrugator, and Frontalis
muscles.
The Eyelids {palpehrce) are two thin, movable folds, placed in front of the eye,
protecting it from injury by their closure. The upper eyelid is the larger, and the
more movable of the two, and is furnished with an elevator muscle, the Levator
palpebrffi superioris. Wlien the eyelids are open, an elliptical space, the palpebral
fissure {rima palpebrarum) , is left between their margins, the angles of which corre-
spond to the junctions of the upper and lower eyelids, and are called the palpebral
commissures or canthj.
The lateral palpebral commissure (commissura palpebrarum lateralis; external
canthiis) is more acute than the medial, and the eyelids here lie in close contact
with the bulb of the eye: but the medial palpebral commissure {commissura
palpebrarum medialis; internal canthus) is prolonged for a short distance toward the
nose, and the two eyelids are separated by a triangular space, the lacus lacrimalis
(Fig. 892). At the basal angles of the lacus lacrimalis, on the margin of each
eyelid, is a small conical elevation, the lacrimal papilla, the apex of which is pierced
by a small orifice, the pimctum lacrimale, the commencement of the lacrimal duct.
The eyelashes (cilia) are attached to the free edges of the eyelids; they are short,
thick, curved hairs, arranged in a double or triple row: those of the upper eyelid,
more numerous and longer than those of the lower, curve upward; those of the lower
eyelid curve downward, so that they do not interlace in closing the lids. Near
the attachment of the eyelashes are the openings of a number of glands, the ciliary
glands, arranged in several rows close to the free margin of the lid; they are regarded
as enlarged and modified sudoriferous glands.
Structure of the Eyelids. — The eyelids are composed of the following structures taken in their
order from without inward: integument, areolar tissue, fibers of the Orbicularis oculi, tarsus,
orbital septum, tarsal glands and conjunctiva. The upper eyelid has, in addition, the aponeu-
rosis of the Levator palpebrae superioris (Fig. 893).
The integument is extremely thin, and continuous at the margins of the eyelids with the con-
junctiva.
The subcutaneous areolar tissue is very lax and delicate, and seldom contains any fat.
The palpebral fibers of the Orbicularis oculi are thin, pale in color, and possess an involuntary
action.
The tarsi {tarsal plates) (Fig. 894) are two thin, elongated plates of dense connective tissue,
about 2.5 cm. in length; one is placed in each eyelid, and contributes to its form and support.
The superior tarsus {tarsus superior; superior tarsal plate), the larger, is of a semilunar form, about
10 mm. in breadth at the center, and gradually narrowing toward its extremities. To the
anterior surface of this plate the aponeurosis of the Levator palpebra' superioris is attached. The
inferior tarsus {tarsus inferior; inferior tarsal plate), the smaller, is thin, elliptical in form, and
' C. B. Lockwood, Journal of Anatomy and Physiology, vol. xx.
65
1026 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
has a vertical diameter of about 5 mm. The free or ciHary margins of these plates are thick and
straight. The attached or orbital margins are connected to the circumference of the orbit by
the orbital septum. The lateral angles are attached to the zygomatic bone by the lateral palpe-
bral raphe. The medial angles of the two plates end at the lacus lacrimalis, and are attached to
the frontal process of the maxilla by the medial palpebral ligament (page 381).
The orbital septum (septum orbitale; palpebral ligament) is a membranous sheet, attached to
the edge of the orbit, where it is continuous with the periosteum. In the upper eyelid it blends
Piinctum lacrimale
Plica semilvnans
Canincula
Punctum lacrimale
Openings of tarsal
(/lands
FiQ. 892.-
-Front of left eye witli e.xelic'.s separated to show
medial canthus.
by its peripheral circumference with the tendon
of the Levator palpebra; superioris and the
superior tarsus, in the lower eyelid with the infe-
rior tarsus. Medially it is thin, and, becoming
separated from the medial palpebral ligament, is
fixed to the lacrimal bone immediately behind
the lacrimal sac. The septum is perforated by
the vessels and nerves which pass from the orbital
cavity to the face and scalp. The eyelids are
richly supplied with blood.
The Tarsal Glands (gland ulcp tarsales
[Meibomi]] Meibomian glands) (Fig. 895).
— The tarsal glands are situated upon the
inner surfaces of the eyelids, between the
tarsi and conjunctiva, and may be dis-
tinctly seen through the latter on everting
the eyelids, presenting an appearance like
parallel strings of pearls. There are about
thirty in the upper eyelid, and somewhat
fewer in the lower. They are imbedded in grooves in the inner surfaces of the
tarsi, and correspond in length with the breadth of these plates; they are, con-
secfuently, longer in the upper than in the lower eyelid. Their ducts open on the
free magins of the lids by minute foramina.
Structure. — The tarsal glands are modified sebaceous glands, each consisting of a single straight
tube or follicle, with numerous small lateral diverticula. The tubes are supported by a basement
membrane, and are lined at their mouths by stratified epithelium; the deeper parts of the tubes
and the lateral offshoots are lined by a layer of polyhedral cells.
The conjunctiva is the mucous membrane of the eye. It lines the inner surfaces
of the eyelids or palpebne, and is reflected over the forepart of the sclera and cornea.
Fig. 89.3. — Sagittal section through the upper
eyelid. (After Waldeyer.) a. Skin. b. Orbicularis
oculi. 6'. Marginal fasciculus of Orbicularis (ciliary
bundle), c. Levator palpebrse. d. Conjunctiva,
e. Tarsus. /. Tarsal gland, g. Sebaceous gland.
h. Eyelashes, i. Small hairs of skin. Sweat
glands, k. Posterior tarsal glands.
THE ACCESSORY ORGANS OF THE EYE
1027
The Palpebral Portion {tunica conjunctiva palpebrarum) is thick, opaque, highly
vascular, and covered with numerous papillae, its deeper part presenting a
considerable amount of lymphoid tissue. At the margins of the lids it becomes
continuous with the lining membrane of the ducts of the tarsal glands, and, through
the lacrimal ducts, with the lining membrane of the lacrimal sac and nasolacrimal
Lacrimal artery
and nerve
Lateral pal-
pebral raphe
Supraorbital vessels
and nerve
Lacrimal sac
Medial palpebral
ligament
Fig. 894. — The tarsi and their ligaments. Right eye; front view.
duct. At the lateral angle of the upper eyelid the ducts of the lacrimal gland open
on its free surface; and at the medial angle it forms a semilunar fold, the plica
semilunaris. The line of reflection of the conjunctiva from the upper eyelid on
to the bulb of the eye is named the superior fornix, and that from the lower lid the
inferior fornix.
Puncta lacrimalia
Fig. 895. — The tarsal glands, etc., seen from the inner surface of the eyelids.
The Bulbar Portion {tunica conjunctiva hulhi). — Upon the sclera the conjunctiva
is loosely connected to the bulb of the eye; it is thin, transparent, destitute of
papillie, and only slightly vascular. Upon the cornea, the conjunctiva consists
only of epithelium, constituting the epithelium of the cornea, already described
(see page 1007). Lymphatics arise in the conjunctiva in a delicate zone around
the cornea, and run to the ocular conjunctiva.
1028 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
In and near the fornices, but more plentiful in the upper than in the lower eyelid,
a number of convoluted tubular glands open on the surface of the conjunctiva.
Other glands, analogous to lymphoid follicles, and called by Henle trachoma glands,
are found in the conjunctiva, and, according to Strohmeyer, are chiefly situated
near the medial palpebral commissure. They were first described by Brush, in
his description of Peyer's patches of the small intestine, as "identical structures
existing in the under eyelid of the ox."
The caruncula lacrimalis is a small, reddish, conical-shaped body, situated at
the medial palpebral commissure, and filling up the lacus lacrimalis. It consists
of a small island of skin containing sebaceous and sudoriferous glands, and is the
source of the whitish secretion which constantly collects in this region. A few
slender hairs are attached to its surface. Lateral to the caruncula is a slight semi-
lunar fold of conjunctiva, the concavity of which is directed toward the cornea;
it is called the plica semilunaris. ]\Iiiller found smooth muscular fibers in this fold;
in some of the domesticated animals it contains a thin plate of cartilage.
The nerves in the conjunctiva are numerous and form rich plexuses. According
to Krause they terminate in a peculiar form of tactile corpuscle, which he terms
"terminal bulb."
The Lacrimal Apparatus (apparatus lacrimalis) (Fig. 896) consists of (a) the
lacrimal gland, which secretes the tears, and its excretory ducts, which convey the
fluid to the surface of the eye; (b) the lacrimal ducts, the lacrimal sac, and the naso-
lacrimal duct, bv which the fluid is conveved into the cavitv of the nose.
The Lacrimal Gland (glandula lacrimalis) . — The lacrimal gland is lodged in the
lacrimal fossa, on the medial side of the zygomatic process of the frontal bone.
It is of an oval form, about the size and shape of an almond, and consists of two
portions, described as the superior and inferior lacrimal glands. The superior
lacrimal gland is connected to the periosteum of the orbit by a few fibrous bands,
and rests upon the tendons of the Recti superioris and lateralis, which separate it
from the bulb of the eye. The inferior lacrimal gland is separated from the superior
by a fibrous septum, and projects into the back part of the upper eyelid, where
its deep surface is related to the conjunctiva. The ducts of the glands, from six
to twelve in number, run obliquely beneath the conjunctiva for a short distance,
and open along the upper and lateral half of the superior conjunctival fornix.
Structures of the Lacrimal Gland (Fig. 897). — In structure and general appearance the lacrimal
resembles the serous saUvary glands (p. 1136). In the recent state the cells are so crowded with
granules that their Umits can hardly be defined. They contain oval nuclei, and the cell proto-
plasm is finely fibrillated.
The Lacrimal Ducts {ductus lacrimalis; lacrimal canals).- — ^The lacrimal ducts, one
in each eyelid, commence at minute orifices, termed pimcta lacrimalia, on the
summits of the papillae lacrimales, seen on the margins of the lids at the lateral
extremity of the lacus lacrimalis. The superior duct, the smaller and shorter of the
two, at first ascends, and then bends at an acute angle, and passes medialward
and downward to the lacrimal sac. The inferior duct at first descends, and then
runs almost horizontally to the lacrimal sac. At the angles they are dilated into
ampullae ; their walls are dense in structure and their mucous lining is covered by
stratified squamous epithelium, placed on a basement membrane. Outside the
latter is a layer of striped muscle, continuous with the lacrimal part of the Orbic-
ularis oculi; at the base of each lacrimal papilla the muscular fibers are circu-
larly arranged and form a kind of sphincter.
The Lacrimal Sac (saccus lacrimalis). — The lacrimal sac is the upper dilated end
of the nasolacrimal duct, and is lodged in a deep groove formed by the lacrimal bone
and frontal process of the maxilla. It is oval in form and measures from 12 to 15
mm. in length; its upper end is closed and rounded; its lower is continued into the
nasolacrimal duct. Its superficial surface is covered by a fibrous expansion derived
THE ORGAN OF HEARING
1029
from the medial palpebral ligament, and its deep surface is crossed by the lacrimal
part of the Orbicularis oculi (page 380), which is attached to the crest on the
lacrimal bone.
Structure. — The lacrimal sac consists of a fibrous elastic coat, lined internally by mucous
membrane: the latter is continuous, through the lacrimal ducts, with the conjunctiva, and
through the nasolacrimal duct with the mucous membrane of the nasal cavity.
The Nasolacrimal Duct {ductus nasolacrimalis ; nasal duct). — The nasolacrimal
duct is a membranous canal, about 18 mm. in length, which extends from the lower
part of the lacrimal sac to the inferior
meatus of the nose, where it ends by a
somewhat expanded orifice, provided
with an imperfect valve, the plica
lacrimalis ( Hasneri) , formed by a fold
of the mucous membrane. It is con-
tained in an osseous canal, formed by
Fia. 896. — The lacrimal apparatus. Right side.
Fia. 897. — Alveoli of lacrimal gland.
the maxilla, the lacrimal bone, and the inferior nasal concha; it is narrower in
the middle than at either end, and is directed downward, backward, and a little
lateralward. The mucous lining of the lacrimal sac and nasolacrimal duct is
covered with columnar epithelium, which in places is ciliated.
THE ORGAN OF HEARING (ORG ANON AUDITUS; THE EAR).
The ear, or organ of hearing, is divisible into three parts: the external ear, the
middle ear or tympanic cavity, and the internal ear or labyrinth.
Cavity of hind-brain
Auditory pit
_ Ectoderm
Fig. 898. — Section through the head of a human
embryo, about twelve days old, in the region of the
hind-bcain. (Kollmann.)
Hind-brain
Auditory
vesicle
Fig. 899. — Section through hind-brain and audi-
tory vesiclea of an embryo more advanced than that
of Fig. B98. (After His.)
The Development of the Ear. — The first rudiment of the internal ear appears
shortly after that of the eye, in the form of a patch of thickened ectoderm, the
auditory plate, over the region of the hind-brain. The auditory plate becomes
depressed and converted into the auditory pit (Fig. 898). The mouth of the pit is
1030 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
then closed, and thus a shut sac, the auditory vesicle, is formed (Fig. 899) ; from it
the epithelial lining of the membranous labyrinth is derived. The vesicle becomes
pear-shaped, and the neck of the flask is obliterated (Fig. 900). From the vesicle
Endolymph ^^^^^^j ^^^^^^
Endolymph .
Neural tube
Vestib.
Vestib. pouch'
■•'pouch
d. sc. sup
4-3 mm. front
■Coch. pouch
6.6 mm. lateral
Lateral groove
d. sc. lat.
'Coclilea
9 mm. lateral
13 mm. lateral
20 mm,, laleral
SO mm. lateral
Fig. 900. — Lateral views of membranous labyrinth and acoustic complex. X 25 dia. (Streeter.) absorpt. focu,
area of ■wall where absorption is complete; amp., ampulla membranacea; cr^is, crus commune; (/. sr. Int., ductus semi-
circularis lateralis; d. sc. post., ductus semicircularis posterior; (/. sr. sup., ductus semicircular superior: coch. or coclilea.
ductus cochlearis; duct, endolymph, ductus endolymphaticus; (/. reunieus, ductus reuniens Henseni; evdol. or endohimphs
appendix endolymphaticus; rec. utr., recessus utriculi; sncc, sacculus; sac. endol., saccus endolymphaticus; sii\us utr. lat.,
sinus utriculi lateralis; utric, utriculus; restib. p., vestibular pouch.
certain diverticula are given off which form the various parts of the membranous
labyrinth. One from the middle part forms the ductus and saccus endolymphaticus,
another from the anterior end gradually elongates, and, forming a tube coiled on
THE ORGAN OF HEARING
1031
itself, becomes the cochlear duct, the vestibular extremity of which is subsequently
constricted to form the canalis reuniens. Three others appear as disk-like evagi-
nations on the surface of the vesicle; the central parts of the walls of the disks
coalesce and disappear, while the peripheral portions persist to form the semi-
Endolymph n . , i
Endolymph
Vestib. pouch-.
i^estib. pouch..
Coch. pouch ■■
6.6 mm. median
Cochlea''
■—Uiric.-sacc.
9 mm. median
11 mm. median
13 mm. median
Reuniens
20 mm. median SO mm. median
Fig. 901. — Median views of membranous lab>Tinth and acoustic complex in liunian embryos. X 25 dia. (Streeter.)
circular ducts; of these the superior is the first and the lateral the last to be com-
pleted (Fig. 902). The central part of the vesicle represents the membranous
vestibule, and is subdivided by a constriction into a smaller ventral part, the
saccule, and a larger dorsal and posterior part, the utricle. This subdivision is
1032 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
effected by a fold which extends deeply into the proximal part of the ductus
endolymphaticus, with the result that the utricle and saccule ultimately com-
municate with each other by means of a Y-shaped canal. The saccule opens
into the cochlear duct, through the canalis reuniens, and the semicircular ducts
communicate with the utricle.
Ductus endolymphaticus
Superior semi-
circular duct
Utricle
^ 1- \i x'j^ .^' r,,«:'=-^~«7F;r^ Saccule
, , - xW^ M a ^m Lateral semi-
cochleare --, -_^^,^ ^^ i • 7 J 4
— ^ ^"^ ^v=» a — circular duct
■^Ductus cochlearis
Fig. 902. — Transverse section through head of fetal sheep, in the region of the labyrinth. X 30. (After Boettcher.)
The mesodermal tissue surrounding the various parts of the epithelial labyrinth
is converted into a cartilaginous ear-capsule, and this is finally ossified to form the
bony labyrinth. Between the cartilaginous capsule and the epithelial structures
is a stratum of mesodermal tissue which is differentiated into three layers, viz..
s Emhrijonic
■g '.s connective tissue
im^. -Cochlear duct
Ligamentum spirale
Scala tympani
Epithelium of the spiral
organ of Corti
Fig. 903. — Xransverse section of the cochlear duct of a fetal cat. (After Boettcher and Ayres.)
an outer, forming the periosteal lining of the bony labyrinth; an inner, in direct
contact with the epithelial structures; and an intermediate, consisting of gelatinous
tissue: by the absorption of this latter tissue the perilymphatic spaces are developed.
The modiolus and osseous spiral lamina of the cochlea are not preformed in cartil-
age but are ossified directly from connective tissue.
THE EXTERNAL EAR 1033
The middle ear and auditory tube are developed from the first pharyngeal pouch.
The entodermal lining of the dorsal end of this pouch is in contact with the ecto-
derm of the corresponding pharyngeal groove; by the extension of the mesoderm
between these two layers the tympanic membrane is formed. During the sixth or
seventh month the tympanic antrum appears as an upward and backward expan-
sion of the tympanic cavity. With regard to the exact mode of development
of the ossicles of the middle ear there is some difference of opinion. The view
generally held is that the malleus is developed from the proximal end of the
mandibular (Meckel's) cartilage (Fig. 43), the incus in the proximal end of the
mandibular arch, and that the stapes is formed from the proximal end of the hyoid
arch. The malleus, Avith the exception of its anterior process is ossified from a single
center which appears near the neck of the bone; the anterior process is ossified
separately in membrane and joins the main part of the bone about the sixth month
of fetal life. The incus is ossified from one center which appears in the upper
part of its long crus and ultimately extends into its lenticular process. The
stapes first appears as a ring {annidvs stapedivs) encircling a small vessel, the stape-
dial artery, which subsequently undergoes atrophy; it is ossified from a single
center which appears in its base.
The external acoustic meatus is developed from the first branchial groove. The
lower part of this groove extends inward as a funnel-shaped tube (primary meatus)
from which the cartilaginous portion and a small part of the roof of the osseous
portion of the meatus are developed. From the lower part of the funnel-shaped
tube an epithelial lamina extends downward and inward along the inferior wall of
the primitive tympanic cavity; by the splitting of this lamina the inner part of
the meatus (secondary meatus) is produced, while the inner portion of the lamins
forms the cutaneous stratum of the tympanic membrane. The auricula or pinna
is developed by the gradual differentiation of tubercles which appear around the
margin of the first branchial groove. The rudiment of the acoustic nerve appears
about the end of the third week as a group of ganglion cells closely applied to the
cephalic edge of the auditory vesicle. Whether these cells are derived from the
ectoderm adjoining the auditory vesicle, or have migrated from the wall of the
neural tube, is as yet uncertain. The ganglion gradually splits into two parts,
the vestibular ganglion and the spiral ganglion. The peripheral branches of the
vestibular ganglion pass in two divisions, the pars superior giving rami to the
superior ampulla of the superior semicircular duct, to the lateral ampulla and to
the utricle; and the pars inferior giving rami to the saccule and the posterior
ampulla. The proximal fibers of the vestibular ganglion form the vestibular nerve;
the proximal fibers of the spiral ganglion form the cochlear nerve.
The External Ear.
The external ear consists of the expanded portion named the auricula or pinna,
and the external acoustic meatus. The former projects from the side of the head
and serves to collect the vibrations of the air by which sound is produced; the latter
leads inward from the bottom of the auricula and conducts the vibrations to the
tympanic cavity.
The Auricula or Pinna (Fig. 904) is of an ovoid form, with its larger end directed
upward. Its lateral surface is irregularly concave, directed slightly forward, and
presents numerous eminences and depressions to which names have been assigned.
The prominent rim of the auricula is called the helix; where the helix turns down-
ward behind, a small tubercle, the auricular tubercle of Darwin, is frequently seen; this
tubercle is very evident about the sixth month of fetal life when the whole auric-
ula has a close resemblance to that of some of the adult monkeys. Another
curved prominence, parallel with and in front of the helix, is called the antihelix ;
1034 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
this divides above into two crura, between which is a triangular depression, the
fossa triangularis. The narrow-curved depression between the hehx and the antihelix
is called the scapha; the antihelix describes a curve
around a deep, capacious cavity, the concha, which is
partially divided into two parts by the crus or com-
mencement of the helix; the upper part is termed the
cymba conchse, the lower part the cavum conchae.
In front of the concha, and projecting backward over
the meatus, is a small pointed eminence, the tragus,
so called from its being generally covered on its under
surface with a tuft of hair, resembling a goat's beard.
Opposite the tragus, and separated from it by the
intertragic notch, is a small tubercle, the antltragus.
Below this is the lobule, composed of tough areolar
and adipose tissues, and wanting the firmness and
elasticity of the rest of the auricula.
The cranial surface of the auricula presents ele-
vations which correspond to the depressions on its
lateral surface and after which they are named,
e. g., eminentia conchae, eminentia triangularis,
etc.
Fig. 904,
-The auricula,
surface.
Lateral
Structure. — The auricula is composed of a thin plate of yellow fibrocartilage, covered with
integument, and connected to the surrounding parts by ligaments and muscles; and to the com-
mencement of the external acoustic meatus by fibrous tissue.
The skin is thin, closely adherent to the cartilage, and covered with fine hairs furnished with
sebaceous glands, which are most numerous in the concha and scaphoid fossa. On the tragus
and antitragus the hairs are strong and numerous. The skin of the auricula is continuous with
that lining the external acoustic meatus.
Spina helicis i
r^^^Twr
Sulcus antihelicis transversxLS
Eminentia conchce
Cartilage of
meatus
Ponticulus
Cauda helicis
Fig. 905. — Cranial surface of cartilage of right auricula.
TJie cartilage of the auricula (cartilago auricuhe; cartilage of the pinna) (Figs. 905, 906) con-
sists of a single piece; it gives form to this part of the ear, and upon its surface are found the
eminences and depressions above described. It is absent from the lobule; it is deficient, also,
between the tragus and beginning of the hehx, the gap being filled up by dense fibrous tissue.
At the front part of the aiu-icula, where the hehx bends upward, is a small projection of cartilage,
called the spina helicis, while in the lower part of the helix the cartilage is prolonged downward
as a tail-hke process, the Cauda helicis; this is separated from the antihelix by a fissure, the
fissura antitragoheUcina. The cranial aspect of the cartilage exliibits a transverse furrow, the
sulcus antihelicis transversus, which corresponds with the inferior crus of the antihehx and
separates the eminentia conchae from the eminentia triangularis. The eminentia conchae is
crossed by a vertical ridge (ponticulus), which gives attachment to the Auricularis posterior
THE EXTERNAL EAR
1035
muscle. In the cartilage of the auricula are two fissures, one behind the crus heficis and another
in the tragus.
The ligaments of fhe auricula {ligamenti auricularia [Valsalva]; liqamcnls of the pinna) consist
of two sets: (1) extnnsic, connecting it to the side of the head; (2) intrinsic, connecting various
parts of its cartilage together.
The extrinsic ligaments are two in number, anterior and posterior. The anterior ligament
extends from the tragus and spina helicis to the root of the zygomatic process of the temporal
bone. The posterior ligament passes from the posterior surface of the concha to the outer surface
of the mastoid process.
The chief intrinsic ligaments are: (a) a strong fibrous band, stretching from the tragus to the
commencement of the helix, completing the meatus in front, and partly encirchng the boundary
of the concha; and (b) a band between the antihelix and the Cauda heUcis. Other less important
bands are found on the cranial surface of the pinna.
The muscles of the auricula (Fig. 906) consist of two sets: (1) the extrinsic, which connect it
with the skull and scalp and move the auricula as a whole; and (2) the intrinsic, which extend
from one part of the auricle to another.
The extrinsic muscles are the Auriculares anterior, superior, and posterior.
The Auricularis anterior (Attrahens
aurem), the smallest of the three, is thin,
fan-shaped, and its fibers are pale and in-
distinct. It arises from the lateral edge
of the galea aponeurotica, and its fibers
converge to be inserted into a projection
on the front of the helix.
The Auricularis superior {Attolens
aurem), the largest of the three, is thin
and fan-shaped. Its fibers arise from the
galea aponeurotica, and converge to be
inserted by a thin, flattened tendon into
the upper part of the cranial surface of the
auricula.
The Auricularis posterior (Retrahens
aurem) consists of two or three fleshy
fasciculi, which arise from the mastoid
portion of the temporal bone by short
aponeurotic fibers. They are inserted into
the lower part of the cranial surface of
the concha.
Actions. — In man, these muscleg possess
very little action: the Auricularis anterior
draws the auricula forward and upward;
the Auricularis superior slightly raises it;
and the Auricularis posterio.'' draws it
backward.
The intrinsic muscles are the:
Helicis major.
Helicis minor.
Tragicus .
Antitragicus.
Transversus auriculae.
Obliquus auriculae.
Fig. 906. — The muscles of the auricula.
The Helicis major is a narrow vertical band situated upon the anterior margin of the helix.
It arises below, from the spina helicis, and is inserted into the anterior border of the helix,
just where it is about to curve backward.
The Helicis minor is an oblique fasciculus, covering the crus helicis.
The Tragicus is a short, flattened vertical band on the lateral surface of the tragus.
The Antitragicus arises from the outer part of the antitragus, and is inserted into the Cauda
helicis and antihehx.
The Transversus auriculae is placed on the cranial surface of the pinna. It consists of scattered
fibers, partly tendinous and partly muscular, extending from the eminentia conchie to the promi-
nence corresponding with the scapha.
The Obliquus auricula', also on the cranial surface, consists of a few fibers extending from
the upper and back part of the concha to the convexity immediately above it.
Nerves. — The Auriculares anterior and superior and the intrinsic muscles on the lateral surface
are supplied by the temporal branch of the facial nerve, the Auricularis posterior and the intrinsic
muscles on the cranial surface by the posterior auricular branch of the same nerve.
1036 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
The arteries of the auricula are the posterior auricular from the external carotid, the anterior
auricular from the superficial temporal, and a branch from the occipital artery.
The veins accompany the corresponding arteries.
The sensory nerves are: the great auricular, from the cervical plexus; the auricular branch
of the vagus; the auriculotemporal branch of the mandibular nerve; and the lesser occipital
from the cervical plexus.
Cartilage of auricula
ic
Incus
Malleus
I Tympanic cavity
Tensor tympani
Tympanic membrane
Cartilaginous
part of cxt.
acoustic meatus
Bony part of
ext. acoustic
meatus
Fig. 907. — External and middle ear, opened from the front. Right side.
The External Acoustic Meatus (meatus acustiais externns; external auditory canal
or meatus) extends from the bottom of the concha to the tympanic membrane (Figs.
907, 908). It is about 4 cm. in length if measured from the tragus; from the bottom
of the concha its length is about 2.5 cm. It forms an S-shaped curve, and is directed
at first iu'vard, forward, and slightly upward {yars externa); it then passes inward
and backv/ard {pars media), and lastly is carried inward, forward, and slightly
downward {pars interna). It is an oval cylindrical canal, the greatest diameter
being directed downward and backward at the external orifice, but nearly hori-
zontally at the inner end. It presents two constrictions, one near the inner end
of the cartilaginous portion, and another, the isthmus, in the osseous portion, about
2 cm. from the bottom of the concha. The tympanic membrane, which closes the
inner end of the meatus, is obliquely directed ; in consequence of this the floor and
anterior wall of the meatus are longer than the roof and posterior wall.
,The external acoustic meatus is formed partly by cartilage and membrane,
and partly by bone, and is lined by skin.
The cartilaginous portion {meatus ooisticus externns cartilagineus) is about 8 mm.
in length; it is continuous with the cartilage of the auricula, and firmly attached
to the circumference of the auditory process of the temporal bone. The cartilage
is deficient at the upper and back part of the meatus, its place being supplied by
fibrous membrane; two or three deep fissures are present in the anterior part of the
cartilage.
The osseous portion {meatus acusticus externns osseus) is about 16 mm. in length,
and is narrower than the cartilaginous portion. It is directed inward and a little
THE MIDDLE EAR OR TYMPANIC CAVITY
1037
forward, forming in its course a slight curve the convexity of which is upward and
backward. Its inner end is smaller than the outer, and sloped, the anterior wall
projecting beyond the posterior for about 4 mm.; it is marked, except at its upper
part, b>' a narrow groove, the tympanic sulcus, in which the circumference of the
tympanic membrane is attached. Its outer end is dilated and rough in the greater
part of its circumference, for the attachment of the cartilage of the auricula. The
front and lower parts of the osseous portion are formed by a curved plate of bone,
the tympanic part of the temporal, which, in the fetus, exists as a separate ring
(annulus tympanicus,) incomplete at its upper part (page 146).
Auditory tube
Condyle of mandible
Internal carotid
artery
Internal acoustic
meatus
of parotid gland
Tragus
- External acoustic
meatus
Tympanic caviti
Tympanic membrane
Masto
Helix
Transverse sinus
Fig. 908. — Horizontal section through left ear; upper half of section.
The skin lining the meatus is very thin; adheres closely to the cartilaginous
and osseous portions of the tube, and covers the outer surface of the tympanic
membrane. After maceration, the thin pouch of epidermis, when withdrawn,
preserves the form of the meatus. In the thick subcutaneous tissue of the cartil-
aginous part of the meatus are numerous ceruminous glands, which secrete the
ear-wax; their structure resembles that of the sudoriferous glands.
Relations of the Meatus. — In front of the osseous part is the condyle of the mandible, which
however, is frequently separated from the cartilaginous part by a portion of the parotid gland.
The movements of the jaw influence to some extent the lumen of this latter portion. Behind the
osseous part are the ma.stoid air cells, separated from the meatus by a thin laj-er of bone.
The arteries supplying the meatus are branches from the posterior auricular, internal maxillary,
and temporal.
The nerves are chiefly derived from the auriculotemporal branch of the mandibular nerve
and the auricular branch of the vagus.
The Middle Ear or Tympanic Cavity (Cavum Tympani; Drum;
Tympanum) .
The middle ear or tympanic cavity is an irregular, laterally compressed space
within the temporal bone. It is filled with air, which is conveyed to it from the
nasal part of the pharynx through the auditory tube. It contains a chain of mov-
able bolies, which connect its lateral to its medial wall, and serve to convey the
vibrations communicated to the tympanic membrane across the cavity to the
internal ear.
1038 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
The tympanic cavity consists of two parts: the tympanic cavity proper, opposite
the tympanic membrane, and the attic or epitympanic recess, above the level of
the membrane; the hitter contains the upper half of the malleus and the greater
part of the incus. Including the attic, the vertical and antero-posterior diameters
of the cavity are each about 15 mm. The transverse diameter measures about
6 mm. above and 4 mm. below; opposite the center of the tympanic membrane
it is only about 2 mm. The tympanic cavity is bounded lateralh* by the tympanic
membrane; medially, by the lateral wall of the internal ear; it communicates,
behind, with the tympanic antrum and through it with the mastoid air cells, and
in front with the auditory tube (Fig. 907).
The Tegmental Wall or Roof (paries tegmentalis) is formed by a thin plate of bone,
the tegmen tympani, which separates the cranial and tympanic cavities. It is
situated on the anterior surface of the petrous portion of the temporal bone close
to its angle of junction with the squama temporalis; it is prolonged backward so
as to roof in the tympanic antrum, and forward to cover in the semicanal for the
Tensor tympani muscle. Its lateral edge corresponds with the remains of the
petrosquamous suture.
The Jugular Wall or Floor {paries jugnlaris) is narrow, and consists of a thin plate
of bone (fundus tympani) which separates the tympanic cavity from the jugular
fossa. It presents, near the labyrinthic wall, a small aperture for the passage of
the tympanic branch of the glossopharyngeal nerve.
Post, malleolar fold
Long crus of incus Pars flaccida
Manuhrium
of malleus ^~^M
Posiero-superior iflT
Lat. proc. of malleus
Ant. ynallcolar fold
quadrant ■ ,■ \^W^ ^^Mii Antero-superior
Postero-inferior ||*- ^^T^lJ^BZ ^ 9"«^^''«"'
quadrant M~~ /^ ^^°
of light
A ntero-inferior quadrant
Fig. 909. — Right tympanic membrane as seen through a speculum.
The Membranous or Lateral Wall (paries memhranacea; outer wall) is formed
mainly by the tympanic membrane, partly by the ring of bone into which this
membrane is inserted. This ring of bone is incomplete at its upper part, forming
a notch (notch of Rivinus), close to which are three small apertures: the iter chordae
posterius, the petrotympanic fissure, and the iter chordae anterius.
The iter chordae posterius (apertura tympanica canaliculi chordoe) is situated in
thp angle of junction between the mastoid and membranous wall of the tympanic
cavity immediately behind the tympanic membrane and on a level with the upper
end of the manubrium of the malleus; it leads into a minute canal, which descends
in front of the canal for the facial nerve, and ends in that canal near the stylo-
mastoid foramen. Through it the chorda tympani nerve enters the tympanic
cavity.
The petrot3rmpanic fissure (fissiira petrotympanica; Glaserian fissure) opens just
above and in front of the ring of bone into which the tympanic membrane is
inserted; in this situation it is a mere slit about 2 mm. in length. It lodges
the anterior process and anterior ligament of the malleus, and gives passage to the
anterior tympanic branch of the internal maxillary artery.
THE MIDDLE EAR OR TYMPANIC CAVITY
1039
The iter chordae anterius {canal of Ilugxder) is placed at the medial end of the
petrotympanic fissure; through it the chorda tympani nerve leaves the tympanic
cavity.
The Tympanic Membrane {memhrana tymjpani) (Figs. 909, 910) separates the
tympanic cavity from the bottom of the external acoustic meatus. It is a thin,
semitransparent membrane, nearly oval
in form, somewhat broader above than
below, and directed very obliquely down-
ward and inward so as to form an angle
of about fifty-five degrees with the floor
of the meatus. Its longest diameter is
downward and forward, and measures
from 9 to 10 mm.; its shortest diameter
measures from 8 to 9 mm. The greater
part of its circumference is thickened,
and forms a fibrocartilaginous ring which is
fixed in the tympanic sulcus at the inner
end of the meatus. This sulcus is defi-
cient superiorly at the notch of Rivinus,
and from the ends of this notch two bands,
the anterior and posterior malleolar folds,
are prolonged to the lateral process of the
malleus. The small, somewhat triangular
part of the membrane situated above these
folds is lax and thin, and is named the
pars flaccida ; in it a small orifice is some-
times seen. The manubrium of the malleus
is firmly attached to the medial surface of
the membrane as far as its center, which
it draws toward the tympanic cavity; the
lateral surface of the membrane is thus
concave, and the most depressed part of
this concavity is named the umbo.
Structure. — The tympanic membrane is com-
posed of three strata: a lateral (cutaneous), an
intermediate (fibrous), and a medial (mucous).
integument lining the meatus. The fibrous stratum consists of two layers: a radiate stratum,
Fig. 910. — The tympanic membrane viewed from
within. (Testut.) The malleus has been resected
immediately beyond its lateral process, in order to
show the tympanomalleolar folds and the membrana
flaccida. 1. Tympanic membrane. 2. Umbo. 3.
Handle of the malleus. 4. Lateral process. 5. Anterior
tympanomalleolar fold. 6. Posterior tympanomalleolar
fold. 7. Pars flaccida. 8. Anterior pouch of Troltsch.
9. Posterior pouch of Troltsch. 10. Fibrocartilaginous
ring. 11. Petrotympanic fissure. 12. Auditory tube.
13. Iter chorda; posterius. 14. Iter chordae anterius.
15 Fossa incudis for short crus of the incus. 16. Pro-
minentia styloidea.
The cutaneous stratum is derived from the
Chorda iympani.
Fig. 911. — View of the inner wall of the tympanum (enlarged.)
the fibers of which diverge from the manubrium of the malleus, and a circular stratum, the
fibers of which are plentiful around the circumference but sparse and scattered near the center
1040 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
of the membrane. Branched or dendritic fibers, as pointed out b}- Griiber, are also present
especially in the posterior half of the membrane.
Vessels and Nerves. — The arteries of the tympanic membrane are derived from the deep
auricular branch of the internal maxillary, which ramifies beneath the cutaneous stratum; and
from the stylomastoid branch of the posterior auricular, and tympanic branch of the internal
maxillary, which are distributed on the mucous surface. The superficial veins open into the
external jugular; those on the deep surface drain partly into the transverse sinus and veins of
the dura mater, and partly into a plexus on the auditory tube. The membrane receives its
chief nerve supply from the auriculotemporal branch of the mandibular; the auricular branch of
the vagus, and the tympanic branch of the glossopharjoigeal also supply it.i
SUPERIOR LIGAMENT
OF MALLEOLUS
EPITYMPANIC
RECESS
NE
MA
ANTERIOR LIGAMENT
AND ANTERIOR
PROCESS OF
MALLEOLUS
INSERTION
OF TENSOR
TYMPANI
GLASERTAN
FISSURE
ARTICULAR SURFACE
FOR BODY OF INCUS
FLACCID PORTION OF
MEMBRANA TYMPANI
POSTERIOR
^^_____-TY M P A N I C
" ' SPINE
TYMPANIC
ORIFICE
OF CANAL
FOR CHORDS
TYMPANI
NERVE
EUSTACHIAN
TUBE
TENSE PORTION OF
MEMBRANA TYMPAN
Fig. 912. — The right membrana tympani with the hammer and the chorda tympani, ^•iewed from within, from behind,
and from above, ^-^palteholz )
The Labyrinthic or Medial Wall (parks labyrinthica; inner wall) (Fig. 913) is
vertical in direction, and presents for examination the fenestras vestibuli and
cochleae, the promontory, and the prominence of the facial canal.
The fenestra vestibuli (fenestra oralis) is a reniform opening leading from the
tympanic cavity into the vestibule of the internal ear; its long diameter is horizontal,
and its convex border is upward. In the recent state it is occupied by the base of
the stapes, the circumference of which is fixed by the annular ligament to the margin
of the foramen.
The fenestra cochleae (fenestra rotunda) is situated below and a little behind the
fenestra vestibuli, from which it is separated by a rounded elevation, the promontory.
It is placed at the bottom of a funnel-shaped depression and, in the macerated bone,
leads into the cochlea of the internal ear; in the fresh state it is closed by a mem-
brane, the secondary tympanic membrane, which is concave toward the tympanic
cavity, convex toward the cochlea. This membrane consists of three layers: an
' Wilson, J. G., -American Journal of Anatomy, 1911, xi.
THE MIDDLE EAR OR TYMPANIC CAVITY
1041
external, or mucous, derived from the mucous lining of the tympanic cavity; an
internal, from the lining membrane of the cochlea; and an intermediate, or fibrous
laver.
Tympanic antrum
Tegmen tympani
Praminence of lateral semicircular canal
Prominence of facial canal
Fenestra vestibuli
Bristle in semicanal for Tensor tympani
Septum canalis musculotubarii
Bristle in hiatus of facial canal
Carotid canal
Bony part of auditory tube
Promontory
Bristle in pyra?uid
Fenestra cochlecB
Sulcus tympanicus
Mastoid cells ^"'^''^ *" stylomastoid foramen
Fia. 913. — Coronal section of right temporal bone.
JUNCTION BETWEEN MAS-
TOID ANTRUM AND
EPITYMPANIC BECESS
TEGMEN
TYMPANI
EPITYMPANIC
RECESS
PROMINENCE OF EXTERNAL
SEMICIRCULAR CANAL
PROMINENCE OF AQUEDUCT
OF FjALLOPIUS
TENDON OF
STAP.EDIUS MUSCLE
PLICA
STAPEDIUS
PROCESSUS
COCHLEARIFORMIS
y^ TENSOR TYMPANI
MUSCLE (cut through)
WALL OF
LABYRINTH
POSTERIOR
SINUS
PYRAMIDAL
EMINENCE
TYMPANIC
SINUS
FOSSULA OF
FENESTRA ROTUNDA
JUGULAR
WALL
TYMPANIC
PLEXUS
Fig 914.— The medial wall and part of the posterior and anterior walls of the right tympanic cavity, lateral view.
(Spalteholz.J
66
1042 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
The promontory (promontormvi) is a rounded hollow prominence, formed by the
projection outward of the first turn of the cochlea ; it is placed between the f enestrte,
and is furrowed on its surface by small grooves, for the lodgement of branches of the
tympanic plexus. A minute spicule of bone frequently connects the promontory
to the pyramidal eminence.
The prominence of the facial canal (prominentia canali^' facialis; prominence of
aqueduct of Fallopius) indicates the position of the bony canal in which the
facial nerve is contained; this canal traverses the labyrinthic wall of the tympanic
cavity above the fenestra vestibuli, and behind that opening curves nearly
vertically downward along the mastoid wall.
The mastoid or posterior wall (paries masioidea) is wider above than below, and
presents for examination the entrance to the tympanic antrum, the pyramidal eminence,
and the fossa incudis.
The entrance to the antnmi is a large irregular aperture, which leads backward
from the epitympanic recess into a considerable air space, named the tympanic
or mastoid antriim (see page 142). The antrum communicates behind and below
with the mastoid air cells, which ^•ary considerably in number, size, and form;
the antrum and mastoid air cells are lined by mucous membrane, continuous with
that lining the tympanic cavity. On the medial wall of the entrance to the antrum
is a rounded eminence, situated above and behind the prominence of the facial
canal; it corresponds with the position of the ampuUated ends of the superior and
lateral semicircular canals.
The pyramidal eminence {eminentia pyramidalis; pyramid) is situated immedi-
ately behind the fenestra vestibuli, and in front of the vertical portion of the facial
canal; it is hollow, and contains the Stapedius muscle; its summit projects forward
toward the fenestra vestibuli, and is pierced by a small aperture which transmits
the tendon of the muscle. The cavity in the pyramidal eminence is prolonged
downward and backward in front of the facial canal, and communicates with it
by a minute aperture which transmits a twig from the facial nerve to the Stapedius
muscle.
The fossa incudis is a small depression in the lower and back part of the epi-
tympanic recess; it lodges the short crus of the incus.
The Carotid or Anterior Wall (paries carotica) is wider above than below; it corre-
sponds with the carotid canal, from which it is separated by a thin plate of bone
perforated by the tympanic branch of the internal carotid artery, and by the deep
petrosal nerve which connects the sympathetic plexus on the internal carotid
artery with the tympanic plexus on the promontory. At the upper part of the
anterior wall are the orifice of the semicanal for the Tensor tympani muscle and
the tympanic orifice of the auditory tube, separated from each other by a thin
horizontal plate of bone, the septum canalis musculotubarii. These canals run from
the tympanic cavity forward and downward to the retiring angle between the
squama and the petrous portion of the temporal bone.
The semicanal for the Tensor tympani (semicanalis m. tensor is tympani) is the
superior and the smaller of the two; it is cylindrical and lies beneath the tegmen
tj'mpani. It extends on to the labyrinthic wall of the tympanic cavity and ends
immediately above the fenestra vestibuli.
The septum canalis musculotubarii (processus cochleariformis) passes backward
below this semicanal, forming its lateral wall and floor; it expands above the ante-
rior end of the fenestra vestibuli and terminates there by curving laterally so as
to form a pulley over which the tendon of the muscle passes.
The auditory tube (tuba auditiva; Eustachian tube) is the channel through which
the tympanic cavity communicates with the nasal part of the pharynx. Its length
is about 36 mm., and its direction is downward, forward, and medialward, forming
an angle of about 45 degrees with the sagittal plane and one of from 30 to 40 degrees
THE MIDDLE EAR OR TYMPANIC CAVITY
1043
with the horizontal plane. It is formed partlv of bone, partly of cartilage and fibrous
tissue (Figs. 819, 915).
The osseous portion {pars osseo ivbw anditivop) is about 12 mm. in length. It
begins in the carotid wall of the tympanic cavity, below the septum canalis muscuio-
tubarii, and, gradually narrowing, ends at the angle of junction of the squama and
the petrous portion of the temporal bone, its extremity presenting a jagged margin
which serves for the attachment of the cartilaginous portion.
TENSOR TVMPANI
INCUS
MEMBRANA
TYMPANI
RYNGEAL OPEN
ING OF TUBE
Fig. 915. — Auditory tube, laid open by a cut in its long axis. (Testut.)
The cartilaginous portion {yars cartilaginea tvhw auditivcp), about 24 mm. in length,
is formed of a triangular plate of elastic fibrocartilage, the apex of which is attached
to the margin of the medial end of the osseous portion of the tube, while its base
lies directly under the mucous membrane of the nasal part of the pharynx, where
it forms an elevation, the torus tubarius or cushion, behind the pharyngeal orifice of
the tube. The upper edge of the cartilage is curled upon itself, being bent laterally
so as to present on transverse section the appearance of a hook ; a groove or furrow
is thus produced, which is open below and laterally, and this part of the canal is
completed by fibrous membrane. The cartilage lies in a groove between the petrous
part of the temporal and the great wing of the sphenoid; this groove ends opposite
the middle of the medial pterygoid plate. The cartilaginous and bony portions of
the tube are not in the same plane, the former inclining downward a little more
than the latter. The diameter of the tube is not uniform throughout, being greatest
at the pharyngeal orifice, least at the junction of the bony and cartilaginous por-
tions, and again increased toward the tympanic cavity; the narrowest part of the
tube is termed the isthmus. The position and relations of the pharyngeal orifice
are described with the nasal part of the pharynx. The mucous membrane of the
tube is continuous in front with that of the nasal part of the pharynx, and behind
\yith that of the tympanic cavity; it is covered with ciliated epithelium and is thin
in the osseous portion, while in the cartilaginous portion it contains many mucous
glands and near the pharyngeal orifice a considerable amount of adenoid tissue,
which has been named by Gerlach the tube tonsil. The tube is opened during deglu-
1044 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
tition by the Salpingopharjngeus and Dilatator tubse. The latter arises from the
hook of the cartilage and from the membranous part of the tube, and blends below
with the Tensor veli palatini.
Head
Lateral
process
A nterior
process
The Auditory Ossicles (Ossicula Auditus).
The tympanic cavity contains a chain of three movable ossicles, the malleus,
incus, and stapes. The first is attached to the tympanic membrane, the last to
the circumference of the fenestra vestibuli, the incus being placed between and
connected to both by delicate articulations.
The Malleus (Fig. 916), so named from its fancied resemblance to a hammer,
consists of a head, neck, and three processes, viz., the manubrium, the anterior and
lateral processes.
The head (capituhim mallei) is the large upper extremity of the bone; it is oval
in shape, and articulates posteriorly with the incus, being free in the rest of its
extent. The facet for articu-
lation with the incus is con-
stricted near the middle, and
consists of an upper larger and
lower smaller part, which form
nearly a right angle with each
other. Opposite the constric-
tion the lower margin of the
facet projects in the form of a
process, the cog-tooth or spur oi
the malleus.
The neck {collnm mallei) is
the narrow contracted part just
beneath the head ; below it, is a
a prominence, to which the
various processes are attached.
The manubrium mallei (handle) is connected by its lateral margin with the tym-
panic membrane. It is directed downward, medialward, and backward; it decreases
in size toward its free end, which is curved slightly forward, and flattened trans-
versely. On its medial side, near its upper end, is a slight projection, into which
the tendon of the Tensor tympani is inserted.
The anterior process (processus anterior [Folii]; processus gracilis) is a delicate
spicule, which springs from the eminence below the neck and is directed forward
to the petrotympanic fissure, to which it is connected by ligamentous fibers. In
the fetus this is the longest process of the malleus, and is in direct continuity with
the cartilage of ]\Ieckel.
The lateral process (processus lateralis; processjis brevis) is a slight conical projec-
tion, which springs from the root of the manubrium; it is directed laterally, and is
attached to the upper part of the tympanic membrane and, by means of the ante-
rior and posterior malleolar folds, to the extremities of the notch of Rivinus.
The Incus (Fig. 917) has received its name from its supposed resemblance to
an anvil, but it is more like a premolar tooth, with two roots, which differ in
length, and are widely separated from each other. It consists of a body and two
crura.
The body (corpus incudis) is somewhat cubical but compressed transversely.
On its anterior surface is a deeply concavo-convex facet, which articulates with
the head of the malleus.
The two crura diverge from one another nearly at right angles.
The short cms (crus breve; short process), somewhat conical in shape, projects
FiQ. 916. — Left malleus. A. From behind. B. From within.
THE AUDITORY OSSICLES
1045
almost horizontally backward, and is attached to the fossa incudis, in the lower
and back part of the epitympanic recess.
The long cms (cms longum; long process) descends nearly vertically behind and
parallel to the manubrium of the malleus, and, bending medialward, ends in a
rounded projection, the lenticular process, which is tipped with cartilage, and
articulates with the head of the stapes.
The Stapes (Fig. 918), so called from its resemblance to a stirrup, consists of a
head, neck, two crura, and a base.
The head {capituhun stapedis) presents a depression, which is covered by cartilage,
and articulates with the lenticular process of the incus.
The neck, the constricted part of the bone succeeding the head, gives insertion
to the tendon of the Stapedius muscle.
The two crura {cms anterivs and cms posterivs) diverge from the neck and are
connected at their ends by a flattened oval plate, the base (basis stapedis), which
forms the foot-plate of the stirrup and is fixed to the margin of the fenestra vestibuli
by a ring of ligamentous fibers. Of the two crura the anterior is shorter and less
curved than the posterior.
Short crus
Facet for
malleus -^/i
Long crus — ^
Head
Neck
Body \^ Lent icular
process
A
Fig. 017. — Left incus. ^-1. From within. B. From
the front.
Anterior crus
Posterior crus
Base
£
Fig. 918. — A. Left stapes. B. Base of stapes, medial
surface.
Articulations of the Auditory Ossicles (articidationes ossiculorvm auditus). —
The incudomalleolar joint is a saddle-shaped diarthrosis; it is surrounded by an
articular capsule, and the joint cavity is incompletely divided into two by a wedge-
shaped articular disk or meniscus. The incudostapedial joint is an enarthrosis,
surrounded by an articular capsule; some observers have described an articular
disk or meniscus in this joint; others regard the joint as a syndesmosis.
Ligaments of the Ossicles (ligamenta ossiculorum auditus). — The ossicles are
connected with the walls of the tympanic cavit}^ by ligaments: three for the
malleus, and one each for the incus and stapes.
The anterior ligament of the malleus (Ug. mallei anterius) is attached by one end
to the neck of the malleus, just above the anterior process, and by the other to
the anterior wall of the tympanic cavity, close to the petrotympanic fissure, some
of its fibers being prolonged through the fissure to reach the spina angularis of the
sphenoid.
The superior ligament of the malleus (Ug. mallei superius) is a delicate, round
bundle which descends from the roof of the epitympanic recess to the head of the
malleus.
The lateral ligament of the malleus (Ug. mallei laterale; external ligament of the
malleus) is a triangular band passing from the posterior part of the notch of Rivinus
to the head of the malleus. Helmholtz described the anterior ligament and the
posterior part of the lateral ligament as forming together the axis ligament around
which the malleus rotates.
The posterior ligament of the incus (Ug. incudis posterius) is a short, thick band
connecting the end of the short crus of the incus to the fossa incudis.
1046 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
A superior ligament of the incus {lig. incudis suyerius) has been described, but it
is little more than a fold of mucous membrane.
The vestibular surface and the circumference of the base of the stapes are covered
with hyaline cartilage; that encircling the base is attached to the margin of the
fenestra vestibuli by a fibrous ring, the annular
ligament of the base of the stapes {lig. annulare
baseos stapedis) .
The Muscles of the Tympanic Cavity (m usculi
ossiculoruvi and it us) are the Tensor tympani
and Stapedius.
The Tensor tympani, the larger, is contained
in the bony canal al)ove the osseous portion of
the auditory tube, from which it is separated
by the septum canalis musculotubarii. It
arises from the cartilaginous portion of the
auditory tube and the adjoining part of the
great wing of the sphenoid, as well as from the
osseous canal in which it is contained. Passing
backward through the canal, it ends in a slen-
der tendon which enters the tympanic cavity,
makes a sharp bend around the extremity of
the septum, and is inserted into the manubrium
of the malleus, near its root. It is supplied
by a branch of the mandibular nerve through
the otic ganglion.
The Stapedius arises from the wall of a con-
ical cavity, hollowed out of the interior of the
pyramidal eminence; its tendon emerges from
the orifice at the apex of the eminence, and, passing forward, is inserted into the
posterior surface of the neck of the stapes. It is supplied by a branch of the facial
nerve.
Fig. 919. — Chain of ossicles and their liga-
ments, seen from the front in a vortical, tran.s-
verse section of the tympanum. (Testut.)
Actions. — The Tensor tympani draws the tympanic membrane medialward, and thus increases
its tension. The Stapedius pulls the head of the stapes backward and thus causes the base of
the bone to rotate on a vertical axis drawn through its own center; the back part of the base is
pressed inward toward the vestibule, while the forepart is withdrawn from it. By the action of
the muscle the tension of the fluid within the intt'rnal ear is probably increased.
The Mucous Membrane of the Tympanic Cavity is continuous with that of the pharynx, through
the auditory tube. It invests the auditory ossicles, and the muscles and nerves contained in
the tympanic cavity; forms the medial layer of the tympanic membrane, and the lateral layer
of the secondary tympanic membrane, and is reflected into the tympanic antrum and mastoid
cells, which it Unes throughout. It forms several vascular folds, which extend from the walls
of the tympanic cavity of the ossicles; of these, one descends from the roof of the
cavity to the head of the malleus and upper margin of the body of the incus, a second
invests the Stapedius muscle: other folds invest the chorda tympani nerve and the Tensor
tympani muscle. These folds separate off pouch-like cavities, and give the interior of the tym-
panum a somewhat honey-combed appearance. One of these pouches, the pouch of Prussak,
is wgU-marked and lies between the neck of the malleus and the membrana fiaccida. Two other
recesses may be mentioned: they are formed by the mucous membrane which envelops the
chorda tympani nerve and are situated, one in front of, and the other behind the manubrium of
the malleus; they are named the anterior and posterior recesses of Troltsch. In the tympanic
cavity this membrane is pale, thin, slightly vascular, and covered for the most part with colum-
nar ciliated epithelium, but over the pyramidal eminence, ossicles, and tympanic membrane
it possesses a flattened non-ciliated epithelium. In the tympanic antrum and mastoid cells
its epithelium is also non-ciliated. In the osseous portion of the auditory tube the membrane is
thin; but in the cartilaginous portion it is very thick, highly vascular, and provided with numerous
mucous glands; the epithelium which hues the tube is columnar and ciliated.
Vessels and Nerves. — The arteries are six in number. Two of them are larger than the others,
viz., the tympanic branch of the internal maxillary, which supplies the tympanic membrane;
THE INTERNAL EAR OR LABYRINTH 1047
and the stylomastoid branch of the posterior auricular, which supplies the back part of the
tympanic cavity and mastoid cells. The smaller arteries are — the petrosal branch of the middle
meningeal, which enters through the hiatus of the facial canal; a branch from the ascending
pharyngeal, and another from the artery of the pterygoid canal, which accompany the auditory
tube; arid the tympanic branch from the internal carotid, given ofT in the carotid canal and
perforating the thin anterior wall of the tympanic cavity. The veins terminate in the pterygoid
plexus and the superior petrosal sinus. The nerves constitute the tympanic plexus, which
ramifies upon the surface of the promontory. The plexus is formed by (1) the tympanic branch
of the glossopharyngeal; (2) the caroticotympanic nerves; (3) the smaller superficial petrosal
nerve; and (4) a branch which joins the greater superficial petrosal.
The tympanic branch of the glossopharyngeal (Jacobson's nerve) enters the tympanic cavity
by an aperture in its floor close to the labyrinthic wall, and divides into branches which
ramify on the promontory and enter into the forriuation of the tympanic plexus. The superior
and inferior caroticotympanic nerves from the carotid plexus of the sympathetic pass through
the wall of the carotid canal, and join the branches of the tympanic branch of the glossopharyn-
geal. The branch to the greater superficial petrosal passes through an opening on the laby-
rinthic wall, in front of the fenestra vestibuli. The smaller superficial petrosal nerve, from
the otic ganglion, passes backward through a foramen in the middle fossa of the base of the
skull (sometimes through the foramen ovale), and enters the anterior surface of the petrous
part of the temporal bone through a small aperture, situated lateral to the hiatus of the facial
canal; it courses downward through the bone, past the genicular ganglion of the facial nerve,
receiving a connecting filament from it, and enters the tympanic cavity, where it communicates
with the tympanic branch of the glossopharyngeal, and assists in forming the tympanic plexus.
The branches of distribution of the tympanic plexus are supplied to the mucous membrane
of the tympanic cavity; a branch passes to the fenestra vestibuli, another to the fenestra cochlea',
and a third to the auditory tube. The smaller superficial petrosal may be looked upon as the
continuation of the tympanic branch of the glossopharyngeal through the plexus to the otic
ganglion.
In addition to the tympanic plexus there are the nerves supplying the muscles. The Tensor
tympani is supplied by a branch from the mandibular through the otic ganghon, and the Stapedius
by a branch from the facial.
The chorda tympani nerve crosses the tympanic cavity. It is given off from the sensory part
of the facial, about 6 mm. before the nerve emerges from the stylomastoid foramen. It runs
from below upward and forward in a canal, and enters the tympanic cavity through the iter
chordae posterius, and becomes invested with mucous membrane. It traverses the tympanic
cavity, crossing medial to the tympanic membrane and over the upper part of the manubrium
of the malleus to the carotid wall, where it emerges through the iter chordae anterius (canal
of Huguier).
The Internal Ear or Labyrinth (Auris Interna).
The internal ear is the essential part of the organ of hearing, receiving the ultimate
distribution of the auditory nerve. It is called the labyrinth, from the complexity
of its shape, and consists of two parts: the osseous labyrinth, a series of cavities
within the petrous part of the temporal bone, and the membranous labyrinth, a
series of communicating membranous sacs and ducts, contained within the bon\'
cavities.
The Osseous Labyrinth {lahijriuthus ossens) (Figs. 920, 921). — The osseous
labyrinth consists of three parts: the vestibule, semicircular canals, and cochlea.
These are cavities hollowed out of the substance of the bone, and lined by
periosteum; they contain a clear fluid, the perilymph, in which the membranous
labyrinth is situated.
The Vestibule (vestibulum). — The vestibule is the central part of the osseous
labyrinth, and is situated medial to the tympanic cavity, behind the cochlea, and
in front of the semicircular canals. It is somewhat ovoid in shape, but flattened
transverseh^; it measures about 5 mm. from before backward, the same from above
downward, and about 3 mm. across. In its lateral or tympanic icall is the fenestra
vestibuli, closed, in the fresh state, by the base of the stapes and annular ligament.
On its medial wall, at the forepart, is a small circular depression, the recessus
sphsericus, which is perforated, at its anterior and inferior part, by several minute
holes (macula cribrosa media) for the passage of filaments of the acoustic nerve
to the saccule; and behind this depression is an oblique ridge, the crista vestibuli,
1048 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
the anterior end of which is named the pyramid of the vestibule. This ridge bifur-
cates below to enclose a small depression, the fossa cochlearis, which is perforated
by a number of holes for the passage of filaments of the acoustic nerve which supply
the vestibular end of the ductus cochlearis. As the hinder part of the medial wall
is the orifice of the aquaeductus vestibuli, which extends to the posterior surface of
Fig. 920. — Right osseous labyrinth. Lateral \-iew.
the petrous portion of the temporal bone. It transmits a small vein, and contains
a tubular prolongation of the membranous labyrinth, the ductus endolymphaticus,
which ends in a cul-de-sac between the layers of the dura mater within the cranial
cavity. On the vpper wall or roof is a transversely oval depression, the recessus
ellipticus, separated from the recessus sphtericus by the crista vestibuli already
mentioned. The pyramid and adjoining part of the recessus ellipticus are perforated
Recessus ellipticus
Recessus sphcericus
Orifice of aquccductus vestibuli I 7^^e^
„ 77 • / Orifice of aoiiceductus cochleae
t ossa cochlearis / </ j z
Cochlear fenestra
Fig. 921. — Interior of right osseous labyrinth.
by a number of holes (macula cribrosa superior). The apertures in the pyramid
transmit the nerves to the utricle; those in the recessus ellipticus the nerves to the
ampullae of the superior and lateral semicircular ducts. Behind are the five orifices
of the semicircular canals. In jront is an elliptical opening, which communicates
with the scala vestibuli of the cochlea.
THE INTERNAL EAR OR LABYRINTH
1049
The Bony Semicircular Canals {canaJes semi circular es ossei). — The bony semi-
circular canals are three in number, superior, posterior, and lateral, and are situated
above and behind the vestibule. They are unequal in length, compressed from side
to side, and each describes the greater part of a circle. Each measures about
0.8 mm. in diameter, and presents a dilatation at one end, called the ampulla, which
measures more than twice the diameter of the tube. They open into the vestibule
by five orifices, one of the apertures being common to two of the canals.
Plane of superior
^ semicircular canal
Acoustic
nerve
--^^X'-^f\- Facial
nerve
\'
t
I
Fig. 922. — Position of the right bony labyrinth of the ear in the skull, viewed from above.
sidered transparent and the labyrinth drawn in from a rorrosion preparation.
The temporal bone is con-
(Spalteholz.)
The superior semicircular canal {canalis semicircular is superior), 15 to 20 mm.
in length, is vertical in direction, and is placed transversely to the long axis of the
petrous portion of the temporal bone, on the anterior surface of which its arch
forms a round projection. It describes about two-thirds of a circle. Its lateral
extremity is ampullated, and opens into the upper part of the vestibule; the oppo-
site end joins with the upper part of the posterior canal to form the cms commune,
which opens into the upper nd medial part of the vestibule.
The posterior semicircular canal (canalis semicircular is posterior), also vertical, is
directed backward, nearly parallel to the posterior surface of the petrous bone;
it is the longest of the three, measuring from 18 to 22 mm.; its lower or ampullated
end opens into the lower and back part of the vestibule, its upper into the crus
commune already mentioned.
The lateral or horizontal canal (canalis se7nicircularis lateralis; external semicircular
canal) is the shortest of the three. It measures from 12 to 15 mm., and its arch
is directed horizontally backward and lateralward; thus each semicircular canal
stands at right angles to the other two. Its ampullated end corresponds to the
1050 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
upper and lateral angle of the vestibule, just above the fenestra vestibuli, where
it opens close to the ampullated end of the superior canal; its opposite end opens
at the upper and back part of the vestibule. The lateral canal of one ear is very
nearly in the same plane as that of the other; while the superior canal of one ear
is nearly parallel to the posterior canal of the other.
Helicotrema
Cupuln
Lamina spiralis
/ ■ ossea „ . .,
Tympanic cavity
Scala vestibuli
Scala tympani
Vestibular fenestra
Fissura vestibuli
■ Recessus
spha;ricus
Fossa cochlearis
Lat. semicircular
I canal
Vestibule
Post, semicircular
canal
Aqjurductus
vestibuli
Reces suscepticus
Fig. 923. — The cochlea and vestibule, viewed from above. All the hard parts which form the roof of the internal
ear have been removed with the saw.
The Cochlea (Figs. 922, 923). — The cochlea bears some resemblance to a common
snail-shell; it forms the anterior part of the labyrinth, is conical in form, and placed
almost horizontally in front of the vestibule; its apex {cvpula) is directed forward
and lateralward, with a slight inclination downward, toward the upper and front
part of the labyrinthic Avail of the tympanic cavity; its base corresponds with the
bottom of the internal acoustic meatus, and is perforated by numerous apertures
for the passage of the cochlear division of the acoustic nerve. It measures about
5 mm. from base to apex, and its breadth across the base is about 9 mm. It con-
sists of a conical shaped central axis, the modiolus; of a canal, the inner wall of which
is formed by the central axis, wound spirally around it for two turns and tliree-
quarters, from the base to the apex; and of a delicate lamina, the osseous spiral
lamina, which projects from the modiolus,, and, following the windings of the canal,
partially subdivides it into two. In the recent state a membrane, the basilar
membrane, stretches from the free border of this lamina to the outer wall of the bony
cochlea and completely separates the canal into two passages, which, however,
communicate with each other at the apex of the modiolus by a small opening
named the helicotrema.
The modiolus is the conical central axis or pillar of the cochlea. Its base is broad,
and appears at the bottom of the internal acoustic meatus, where it corresponds
with the area cochlete; it is perforated by numerous orifices, which transmit fila-
ments of the cochlear division of the acoustic nerve; the nerves for the first turn
and a half pass through the foramina of the tractus spiralis foraminosus; those
for the apical turn, through the foramen centrale. The canals of the tractus
spiralis foraminosus pass up through the modiolus and successively bend outward
THE INTERNAL EAR OR LABYRINTH 1051
to reach the attached margin of the lamina spiralis ossea. Here they become
enlarged, and by their apposition form the spiral canal of the modiolus, which
follows the course of the attached margin of the osseous spiral lamina and lodges
the spiral ganglion (ganglion of Corti). The foramen centrale is continued into
a canal which runs up the middle of the modiolus to its apex. The modiolus
diminishes rapidly in size in the second and succeeding coil.
The bony canal of the cochlea takes two turns and three-quarters around the
modiolus. It is about 30 mm. in length, and diminishes gradually in diameter
from the base to the summit, where it terminates in the cupula, which forms the
apex of the cochlea. The beginning of this canal is about o mm. in diameter;
it diverges from the modiolus toward the tympanic cavity and vestibule, and
presents three openings. One, the fenestra cochleae, communicates with the tym-
panic cavity — in the fresh state this aperture is closed by the secondary tympanic
membrane ; another, of an elliptical form, opens into the vestibule. The third is the
aperture of the aqua?ductus cochlese, leading to a minute funnel-shaped canal,
which opens on the inferior surface of the petrous part of the temporal bone
and transmits a small vein, and also forms a communication between the
subarachnoid cavity and the scala tympani.
The osseous spiral lamina (lamina spiralis ossea) is a bony shelf or ledge which pro-
jects from the modiolus into the interior of the canal, and, like the canal, takes two-
and three-quarter turns around the modiolus. It reaches about half-way toward
the outer wall of the tube, and partially divides its cavity into two passages or
scala?, of which the upi^er is named the scala vestibuli, while the lower is termed
the scala tympani. Near the summit of the cochlea the lamina ends in a hook-
shaped process, the hamulus laminae spiralis; this assists in forming the boundary
of a small opening, the helicotrema, through which the two scaLie communicate
with each other. From the spiral canal of the modiolus numerous canals pass out-
ward through the osseous spiral lamina as far as its free edge. In the lower part
of the first turn a second bony lamina, the secondary spiral lamina, projects inward
from the outer wall of the bony tube; it does not, however, reach the primary
osseous spiral lamina, so that if viewed from the vestibule a narrow fissure, the
vestibule fissure, is seen between them.
The osseous labyrinth is lined by an exceedingly thin fibro-serous membrane;
its attached surface is rough and fibrous, and closely adherent to the bone; its
free surface is smooth and pale, covered with a layer of epithelium, and secretes
a thin, limpid fluid, the perilymph. A delicate tubular process of this membrane
is prolonged along the aqueduct of the cochlea to the inner surface of the dura
mater.
The Membranous Labyrinth (lahijrinthus menihranaceus) (Figs. 924, 925, 926). —
The membranous labyrinth is lodged within the bony cavities just described,
and has the same general form as these; it is, however, considerably smaller, and
is partly separated from the bony walls by a quantity of fluid, the perilymph. In
certain places it is fixed to the walls of the cavity. The membranous labyrinth
contains fluid, the endolymph, and on its walls the ramifications of the acoustic
nerve are distributed.
Within the osseous vestibule the membranous labyrinth does not quite preserve
the form of the bony cavity, but consists of two membranous sacs, the utricle,
and the saccule.
The Utricle (utriculus). — ^The utricle, the larger of the two, is of an oblong form,
compressed transversely, and occupies the upper and back part of the vestibule,
lying in contact with the recessus ellipticus and the part below it. That portion
which is lodged m the recess forms a sort of pouch or cul-de-sac, the floor and ante-
rior wall of which are thickened, and form the macula acustica utriculi, which receives
the utricular filaments of the acoustic nerve. The cavity of the utricle communi-
1052 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
cates behind with the semicircular ducts by five orifices. From its anterior wall is
given off the ductus utriculosaccularis, which opens into the ductus endolymphaticus.
The Saccule {sacculus). — The saccule is the smaller of the two vestibular sacs;
it is globular in form, and lies in the recessus spha^ricus near the opening of the
scala vestibuli of the cochlea. Its anterior part exhibits an oval thickening, the
macula acustica sacculi, to which are distributed the saccular filaments of the
acoustic nerve. Its cavity does not directly communicate with that of the utricle.
From the posterior wall a canal, the ductus endolymphaticus, is given off; this duct
is joined by the ductus utriculosaccularis, and then passes along the aquaeductus
vestibuli and ends in a blind pouch (saccus endolymphaticus) on the posterior sur-
face of the petrous portion of the temporal bone, where it is in contact with the
dura mater. From the lower part of the saccule a short tube, the canalis reuniens
of Hensen, passes downward and opens into the ductus cochlearis near its vestibular
extremity (Fig. 924).
AMPULLflt.
DUCTUS
ENDOLYMPHATICUS
Fig. 924. — The membranous labyrinth. (Enlarged.)
The Semicircular Ducts {ductus semicirculares; membranous semicircular canals),
(Figs. 925, 926). — The semicircular ducts are about one-fourth of the diameter
of the osseous canals, but in number, shape, and general form they are precisely
similar, and each presents at one end an ampulla. They open by five orifices into
the utricle, one opening being common to the medial end of the superior and the
upper end of the posterior duct. In the ampullae the wall is thickened, and projects
into the cavity as a fiddle-shaped, transversely placed elevation, the septum trans-
versum, in which the nerves end.
The utricle, saccule, and semicircular ducts are held in position by numerous
fibrous bands which stretch across the space between them and the bony walls.
Structure (Fig. 927). — The walls of the utricle, saccule, and semicircular ducts consist of
three layers. The outer layer is a loose and flocculent structure, apparently composed of ordinary
fibrous tissue containing bloodvessels and some pigment-cells. The middle layer, thicker and
more transparent, forms a homogeneous membrana propria, and presents on its internal surface,
especially in the semicircular ducts, numerous papilliform projections, which, on the addition
of acetic acid, exhibit an appearance of longitudinal fibrillation. The inner layer is formed of
polygonal nucleated epithelial cells. In the maculae of the utricle and saccule, and in the trans-
verse septa of the ampullae of the semicircular ducts, the middle coat is thickened and the epi-
theUum is columnar, and consists. of supporting cells and hair cells. The former are fusiform,
and their deep ends are attached to the membrana propria, while their free extremities are
united to form a thin cuticle. The hair cells are flask-shaped, and their deep, rounded ends do
not reach the membrana propria, but lie between the supporting cells. The deep part of each
contains a large nucleus, while its more superficial part is granular and pigmented. The free end
is surmounted by a long, tapering, hair-like filament, which projects into the cavity. The
THE INTERNAL EAR OR LABYRINTH
1053
filaments of the acoustic nerve enter these parts, and having pierced the outer and middle layers,
they lose their medullary sheaths, and their axis-cylinders ramify between the hair cells.
Fig. 925. — Right human membranous labyrinth, removed from its bony enclosure and viewed from the antero-lateral
aspect. (G. Retzius.)
12
2.3 118,9,10 IfT 5
5 3'G
Fig. 926. — The same from the postero-medial aspect. 1. Lateral semicircular canal; 1', its ampulla; 2. Poste-
rior canal; 2', its ampulla. 3. Superior canal; 3', its ampulla. 4. Conjoined limb of superior and posterior
canals {sitius utriculi superior). 5. Utricle. 5'. Recessus utricuU. 5". Sinus utriculi posterior. 6. Ductus endo-
lymphaticus. 7. Caualis utriculosaccularis. 8. Nerve to ampulla of superior canal. 9. Nerve to ampulla of lateral
canal. 10. Nerve to reces.sus utriculi (in Fig. 925, the three branches appear conjoined). 10'. Ending of nerve in
recessus utriculi. 11. Facial nerve. 12. Lagena cochleiB. 13. Nerve of cochlea within spiral lamina. 14. Basilar
membrane. 15. Nerve fibers to macula of saccule. 10. Nerve to ampulla of posterior canal. 17. Saccule. 18.
Secondary membrane of tympanum. 19. Canalis reuniens. 20. Vestibular end of ductus cochlearis. 23. Section
of the facial and acoustic nerves within internal acoustic meatus (the separation between them is not apparent in the
section). (G. Retzius J
1054 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
Two small rounded bodies termed otoconia, each consisting of a mass of minute crystalline
grains of carbonate of lime, held together in a. mesh of gelatinous tissue, are suspended in
the endolymph in contact wish the free ends of the hairs projecting from the maculae. Accord-
ing to Bowman, a calcareoutmaterial is also sparingly scattered in the cells hning the ampullae
of the semicircular ducts.
Connective tissue binding
duct to periosteum.
■Semicircular duct
■Fibrous band uniting
free surface of duct
to periosteum
Semicircular
canal
Periosteum .
Fig. 927. — Transverse section of a human semicircular canal and duct (after Riidinger).
The Ductus Cochlearis {membranous cochlea; scala media). — The ductus cochlearis
consists of a spirally arranged tube enclosed in the bony canal of the cochlea and
lying along its outer wall.
As already stated, the osseous spiral lamina extends only part of the distance
between the modiolus and the outer wall of the cochlea, while the basilar membrane
stretches from its free edge to the outer wall of the cochlea, and completes the roof
of the scala tympani. A second and more delicate membrane, the vestibular mem-
brane (Rcissneri) extends from the thickened periosteum covering the osseous
spiral lamina to the outer wall of the cochlea, where it is attached at some little
distance above the outer edge of the basilar membrane. A canal is thus shut off
between the scala tympani below and the scala vestibuli above; this is the ductus
cochlearis or scala media (Fig. 928). It is triangular on transverse section, its roof
being formed by the vestibular membrane, its outer wall by the periosteum lining
the bony canal, and its floor by the membrana basilaris and the outer part of the
lamina spiralis ossea. Its extremities are closed; the upper is termed the lagena
and is attached to the cupula at the upper part of the helicotrema; the lower is
lodged in the recessus cochlearis of the vestibule. Near the lower end the ductus
cochlearis is brought into continuity with the saccule by a narrow, short canal,
the canalis reuniens of Hensen (Fig. 924). On the membrana basilaris is situated
the spiral organ of Corti. The vestibular membrane is thin and homogeneous,
and is covered on its upper and under surfaces by a layer of epithelium. The
periosteum, forming the outer wall of the ductus cochlearis, is greatly thickened
and altered in character, and is called the spiral ligament. It projects inward below
as a triangular prominence, the basilar crest, which gives attachment to the outer
edge of the basilar membrane; immediately above the crest is a concavity, the
THE INTERNAL EAR OR LABYRINTH
1055
sulcus spiralis externus. The upper portion of the spiral Hgament contains numerous
capillary loops and small bloodvessels, and is termed the stria vascularis.
The osseous spiral lamina consists of two plates of bone, and between these are
the canals for the transmission of the filaments of the acoustic nerve. On the upper
plate of that part of the lamina which is outside the vestibular membrane, the perios-
teum is thickened to form the limbus laminae spiralis (Fig. 929), this ends externally
Fig. 928. — Diagrammatic longitudinal section of the cochlea.
in a concavity, the sulcus spiralis internus, which represents, on section, the form
of the letter C; the upper part, formed by the overhanging extremity of the limbus,
is named the vestibular lip; the lower part, prolonged and tapering, is called the
tympanic lip, and is perforated by numerous foramina for the passage of the cochlear
nerves. The upper surface of the vestibular lip is intersected at right angles by a
number of furrows, between which are numerous elevations; these present the
appearance of teeth along the free surface and margin of the lip, and have been
Fibres of Cochlear division
of Auditory nerve
Crista Basilaris
Fig. 929. — Floor of ductus cochlearis.
named by Huschke the auditory teeth (Fig. 930). The limbus is covered by a layer
of what appears to be squamous epithelium, but the deeper parts of the cells with
their contained nuclei occupy the intervals between the elevations and between the
auditory teeth. This layer of epithelium is continuous on the one hand with that
lining the sulcus spiralis internus, and on the other with that covering the under
surface of the vestibular membrane.
1056 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
Basilar Membrane. — The basilar membrane stretches from the tympanic lip of
the osseous spiral lamina to the basilar crest and consists of two parts, an inner
and an outer. The inner is thin, and is named the zona arcuata : it supports the spiral
organ of Corti. The outer is thicker and striated, and is termed the zona pectinata.
The under surface of the membrane is covered by a layer of vascular connective
tissue; one of the vessels in this tissue is somewhat larger than the rest, and is
named the vas spirale; it lies below Corti's tunnel.
Fig. 930. — Limbus laminse spiralis and membrana basilaris. (Schematic.) 1, 1'. Upper and lower lamellse
of the lamina spiralis ossea. 2. Limbus laminae spiralis, with a, the teeth of the first row; 6, b', the auditory teeth
of the other rows; c, c', the interdental grooves and the cells which are lodged in them. 3. Sulcus spiralis internus,
with 3', its labium vestibulare, and 3", its labium tympanicum. 4. Foramina nervosa, giving passage to the nerves
from the ganglion spirale or ganglion of Corti. 5. Vas spirale. 6. Zona arcuata, and 6', zona pectinata of the basilar
membrane, with o, its hyaUne layer, B. its connective-tissue layer. 7. Arch of spiral organ, with "', its inner rod, and
7", its outer rod. 8. Feet of the internal rods, from which the cells are removed. 9. Feet of the external rods. 10.
Vestibular membrane, at its origin. (Testut.)
Membrana tecloria
Ovler hair cells
Limbus
Nerve fibers
Outer rod
JBasilar membrane
J A.SVO = o o 0 !<: » °o o 0 o„o
Cells qf Deiters
Fig. 931. — Section through the spiral organ of Corti. Magnified. (G. Retzius.)
The spiral organ of Corti {organon spirale [Corti]; organ of Corti) (Figs. 931, 932)
is composed of a series of epithelial structures placed upon the inner part of the
basilar membrane. The more central of these structures are two rows of rod-like
bodies, the inner and outer rods or pillars of Corti. The bases of the rods are supported
on the basilar membrane, those of the inner row at some distance from those of the
THE INTERNAL EAR OR LABYRINTH
1057
outer; the two rows incline toward each other and, coming into contact above,
enclose between them and the basilar membrane a triangular tunnel, the tunnel
of Corti. On the inner side of the inner rods is a single row of hair cells, and on the
outer side of the outer rods three or four rows of similar cells, together with certain
supporting cells termed the cells of Deiters and Hensen. The free ends of the outer
hair cells occupy a series of apertures in a net-like membrane, the reticular membrane,
and the entire organ is covered by the tectorial membrane.
Rods of Corti.— Each of these consists of a base or foot-plate, and elongated
part or body, and an upper end or head; the body of each rod is finely striated, but
in the head there is an oval non-striated portion which stains deeply with carmine.
Occupying the angles between the rods and the basilar membrane are nucleated
cells which partly envelop the rods and extend on to the floor of Corti's tunnel ;
these may be looked upon as the undifferentiated parts of the cells from which the
rods have been formed.
Fig. 932. — The lamina reticularia and subjacent structures. (Schematic.) A. Internal rod of Corti, with a, its
plate. B. External rod (in yellow). C. Tunnel of Corti. D. IMembrana basilaris. E. Inner hair cells. 1,1' Internal
and external borders of the membrana reticularis. 2, 2', 2". The three rows of circular holes (in blue). 3. First row
of piialanges (in yellow). 4, 4', 4". Second, third, and fourth rows of phalanges (in red). 6, 6'. 6". The three rows
of outer hair cells (in blue). 7, 7', 7". Cells of Deiters. 8. Cells of Hensen and Claudius. (Testut.)
The inner rods number nearly 6000, and their bases rest on the basilar membrane
close to the tympanic lip of the sulcus spiralis internus. The shaft or body of each
is sinously curved and forms an angle of about 60 degrees with the basilar mem-
brane. The head resembles the proximal end of the ulna and presents a deep
concavity which accommodates a convexity on the head of the outer rod. The
head-plate, or portion overhanging the concavity, overlaps the head-plate of the
outer rod.
The outer rods, nearly 4000 in number, are longer and more obliquely set than the
inner, forming with the basilar membrane an angle of about 40 degrees. Their
heads are convex internally; they fit into the concavities on the heads of the inner
rods and are continued outward as thin flattened plates, termed phalangeal processes,
which unite with the phalangeal processes of Deiters' cells to form the reticular
membrane.
Hair Cells. — The hair cells are short columnar cells; their free ends are on a level
with the heads of Corti's rods, and each is surmounted by about twenty hair-like
processes arranged in the form of a crescent with its concavity directed inward.
The deep ends of the cells reach about half-way along Corti's rods, and each con-
67
1058 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
tains a large nucleus; in contact with the deep ends of the hair cells are the terminal
filaments of the cochlear division of the acoustic nerve. The inner hair cells are
arranged in a single row on the medial side of the inner rods, and their diameters
being greater than those of the rods it follows that each hair cell is supported by
more than one rod. The free ends of the inner hair cells are encircled by a cuticular
membrane which is fixed to the heads of the inner rods. Adjoining the inner
hair cells are one or two rows of columnar supporting cells, which, in turn, are con-
tinuous with the cubical cells lining the sulcus spiralis internus. The outer hair cells
number about 12,000, and are nearly twice as long as the inner. In the basal coil
of the cochlea they are arranged in three regular rows; in the apical coil, in four,
somewhat irregular, rows.
Between the rows of the outer hair cells are rows of supporting cells, called the
cells of Deiters; their expanded bases are planted on the basilar membrane, while
the opposite end of each presents a clubbed extremity or phalangeal process. Imme-
diately to the outer side of Deiters' cells are five or six rows of columnar cells, the
supporting cells of Hensen. Their bases are narrow, while their upper parts are
expanded and form a rounded elevation on the floor of the ductus cochlearis.
The columnar cells lying outside Hensen's cells are termed the cells of Claudius.
A space exists between the outer rods of Corti and the adjacent hair cells; this is
called the space of Nuel.
The reticular lamina (Fig. 932) is a delicate frame- work perforated bj- rounded
holes which are occupied by the free ends of the outer hair cells. It extends from
the heads of the outer rods of Corti to the external row of the outer hair cells, and
is formed by several rows of " minute fiddle-shaped cuticular structures," called pha-
langes, between wh ich are circular apertures containing the free ends of the'hair cells.
The inner most row of phalanges consists of the phalangeal processes of the outer
rods of Corti; the outer rows are formed by the modified free ends of Deiters' cells.
Covering the sulcus spiralis internus and the spiral organ of Corti is the tectorial
membrane, which is attached to the limbus lamina^ spiralis close to the inner edge
of the vestibular membrane. Its inner part is thin and overlies the auditory teeth
of Huschke; its outer part is thick, and along its lower surface, oi)posite the inner
hair cells, is a clear band, named Hensen's stripe, due to the intercrossing of its fibers.
The lateral margin of the membrane is much thinner. Hardesty^ considers the
tectorial membrane as the vibrating mechanism in the cochlea. It is inconceivably
delicate and flexible; far more sensiti\-ely flexible in the transverse than in the
longitudinal direction and the readiness with which it bends when touched is beyond
description. It is ectodermal in origin. It consists of fine colorless fibers embedded
in a transparent matrix (the matrix may be a \'ariety of soft keratin), of a soft
collagenous, semisolid character with marked adhesiveness. The general transverse
direction of the fibers inclines from the radius of the cochlea toward the apex.
The acoustic nerve {n. acnsticus; auditory nerve or nerve of hearing) divides near
the bottom of the internal acoustic meatus into an anterior or cochlear and a
posterior or vestibular branch.
The vestibular nerve (n. vestibularis) supplies the utricle, the saccule, and the
ampulla? of the semicircular ducts. On the trunk of the nerve, within the internal
acoustic meatus, is a ganglion, the vestibular ganglion (ganglion of Scarpa); the
fibers of the nerve arise from the cells of this ganglion. On the distal side of the
ganglion the nerve splits into a superior, an inferior, and a posterior branch.^ The
filaments of the superior branch are transmitted through the foramina in the area
vestibularis superior, and end in the macula of the utricle and in the ampullse
of the superior and lateral semicircular ducts; those of the inferior branch traverse
' American Journal of Anatomy, 1908, \'iii.
^ The nerve sometimes splits on the proximal side of the ganglion, and the latter is then divided into three parts,
one on each branch of the nerve.
Nerve fibers passing out
Ganglion Spiral between the two layers of
s pi rale . fibers the lamina spiralis ossea
PERIPHERAL TERMINATIONS OF NERVES OF GENERAL SENSATIONS 1059
the foramina in the area vestibularis inferior, and end in the macula of the saccule.
The posterior branch runs through the foramen singulare at the postero-inferior
part of the bottom of the meatus and divides into filaments for the supply of the
ampulla of the posterior semicircular duct.
The cochlear nerve {n. cochlearis) divides into numerous filaments at the base of the
modiolus; those for the basal and middle coils pass through the foramina in the,
tractus spiralis foraminosis, those for
the apical coil through the canalis cen-
tralis, and the nerves bend outward to
pass between the lamellae of the osseous
spiral lamina. Occupying the spiral
canal of the modiolus is the spiral
ganglion of the cochlea {ganglion of
Corti) (Fig. 933), consisting of bipolar
nerve cells, which constitute the cells
of origin of this nerve. Reaching the
outer edge of the osseous spiral lamina,
the fibers of the nerve pass through
the foramina in the tympanic lip; some
end by arborizing around the bases of
the inner hair cells, while others pass
between Corti's rods and across the tunnel, to end in a similar manner in relation
to the outer hair cells. The cochlear nerve gives off a vestibular branch to
supply the vestibular end of the ductus cochlearis; the filaments of this branch pass
through the foramina in the fossa cochlearis (page 1048).
Vessels. — The arteries of the labyrinth are the internal auditory, from the basilar, and the
stylomastoid, from the posterior am'icular. The internal auditory artery divides at the bottom
of the internal acoustic meatus into two branches: cochlear and vestibular. The cochlear
branch subdivides into twelve or fourteen twigs, which traverse the canals in the modiolus,
and are distributed, in the form of a capillary net -work, in the lamina spiralis and basilar mem-
brane. The vestibular branches are distributed to the utricle, saccule, and semicircular ducts.
The veins of the vestibule and semicircular canals accompany the arteries, and, receiving
those of the cochlea at the base of the modiolus, unite to form the internal auditory veins which
end in the posterior part of the superior petrosal sinus or in the transverse sinus.
Fig. 933. — Part of the cochlear division of the acoustic
nerve, highly magnified. (Henle.)
PERIPHERAL TERMINATIONS OF NERVES OF GENERAL SENSATIONS.
The peripheral terminations of the nerves associated with general sensations, i. e., the mus-
cular sense and the senses of heat, cold, pain, and pressure, are widely distributed throughout
the body. These nerves may end free among the tissue elements, or in special end-organs where
the terminal nerve filaments are enclosed in capsules.
Free nerve-endings occur chiefly in the epidermis and in the epithelium covering certain
mucous membranes; they are well seen also in the stratified squamous epithelium of the cornea,
and are also found in the root-sheaths and papilke of the hairs, and around the bodies of the
sudoriferous glands. When the nerve fiber approaches its termination, the medullary sheath
suddenly disappears, leaving only the axis-cylinder surrounded by the neurolemma. After a time
the fiber loses its neurolemma, and consists only of an axis-cyhnder, which can be seen, in
preparations stained with chloride of gold, to be made up of fine varicose fibrilla. Finallj'-, the
axis-cylinder breaks up into its constituent fibrilUe which often present regular varicosities and
anastomose with one another, and end in small knobs or disks between the epithelial cells.
Under this heading may be classed the tactile disks described by Merkel as occurring in the
epidermis of the pig's snout, where the fibrillar of the axis-cylinder end in cup-shaped disks in
apposition with large epithelial cells.
The special end-organs exhibit great variety in size and shape, but have one feature in common,
viz., the terminal nerve fibrillse are enveloped by a capsule. Included in this gi-oup are the end-
bulbs of Krause, the corpuscles of Grandry, of Pacini, of Golgi and Mazzoni, of Wagner and
Meissner, and the neurotendinous and neuromuscular spindles.
1060 ORGANS OF THE SENSES ANj!) THE COMMON INTEGUMENT
Capsule of corpuscle
The end-bulbs of Krause (Fig. 934) are minute cylindrical or oval bodies, consisting of a
capsule formed by the expansion of the connective-tissue sheath of a medullated fiber, and
containing a soft semifluid core in which the axis-cylinder
terminates either in a bulbous extremity or in a coiled-up
plexiform mass. End-bulbs are found in the conjunctiva
of the eye (where they are spheroidal in shape in man, but
cylindrical in most other animals), in the mucous mem-
brane of the lips and tongue, and in the epineurium of
nerve trunks. They are also found in the penis and the
clitoris, and have received the name of genital corpuscles;
in these situations they have a mulberry-like appearance,
being constricted by connective-tissue septa into from two
to six knob-like masses. In the synovial membranes of
certain joints, e. g., those of the fingers, rounded or oval
end-bulbs occur, and are designated articular end-bulbs.
The tactile corpuscles of Grandry occur in the papillae of
the beak and tongue of birds. Each consists of a capsule
composed of a very delicate, nucleated membrane, and
contains two or more granular, somewhat flattened cells;
between these cells the axis-cylinder ends in flattened disks.
The Pacinian corpuscles (Fig. 935) are found in the
subcutaneous tissue on the nerves of the palm of the hand
and sole of the foot and in the genital organs of both sexes;
they also occur in connection with the nerves of the joints, and in some other situations, as in
the mesentery and pancreas of the cat and along the tibia of the rabbit. Each cf these cor-
puscles is attached to and encloses the termi-
nation of a single nerve fiber. The corpuscle,
which is perfectly visible to the naked eye
(and which can be most easily demonstrated
in the mesentery of a cat), consists of a num-
ber of lamellae or capsules arranged more or
less concentrically around a central clear space,
in which the nerve fiber is contained. Each
lamella is composed of bundles of fine connec-
tive-tissue fibers, and is lined on its inner sur-
face by a single layer of flattened epithelioid
cells. The central clear space, which is elon-
Medullated
nerve fiber
Fig. 934. — End-bulb of Krause. (Klein.)
Fig. 935. — Pacinian corpuscle, with itg system of
capsules and central cavity, a. Arterial twig, end-
ing in capillaries, which form loops in some of the
intercapsular spaces, and one penetrates to the cen-
tral capsule, b. The fibrous tissue of the stalk, n.
Nerve tube advancing to the central capsule, there
losing its white matter, and stretching along the
axis to the opposite end, where it ends by a tubercu-
lated enlargement.
Fig. 936. — Papilla of the hand, treated with acetic
acid. Magnified 3.50 times. A. Side view of a papilla
of the hand. a. Cortical layer. 6. Tactile corpuscle, c.
Small nerve of the papilla, with neurolemma, d. Its two
nervous fibers running with spiral coils around the tactile
corpuscle, e. Apparent termination of one of the.se fibers.
B. A tactile papilla seen from above so as to show its
transverse section, a. Cortical layer. 6. Nerve fiber, c.
Outer layer of the tactile bodj', with nuclei, d. Clear
interior substance.
gated or cylindrical in shape, is filled with a transparent core, in the middle of which the axis-
cylinder traverses the space to near its distal extremity, where it ends in one or more small
knobs. Todd and Bowman have described minute arteries as entering by the sides of the
nerves and forming capillary loops in the intercapsular spaces, and even penetrating into the
central space.
PERIPHERAL TERMINATIONS OF NERVES OF GENERAL SENSATIONS 1061
Herbst has described a nerve-ending somewhat similar to the Pacinian corpuscle, in the mucous
membrane of the tongue of the duck, and in some other situations. It differs, however, from
the Pacinian corpuscle, in being smaller, in its capsules being more closely api)roximated, and
especially in the act that the axis-cylinder in the central clear space is coated with a continuous
row of nuclei. These bodies arc known as the corpuscles of Herbst.
The corpuscles of Golgi and Mazzoni are found in tlu; subcutaneous tissue of the pulp of
the fingers. They differ from Pacinian corpuscles in that their capsules are thinner, their con-
tained cores thicker, and in the latter the axis-cylinders ramify more extensively and end in
flat expansions.
The tactile corpuscles of Wagner and Meissner (Fig. <»;5()) are oval-shaped bodies. Each
is enveloped by a connective-tissue capsule, and imperfect membranous septa derived from this
penetrate the interior. The axis-cylinder passes through the capsule, and after making several
spiral turns around the body of the corpuscle ends in small globular or pyriform enlargements.
Thes3 tactile corpuscles occur in the papilla? of the corium o;' the hand and foot, the front of
the forearm, the skin of the lips, the mucous membrane of the tip of the tongue, the palpebral
conjunctiva, and the skin of the mammary papilla.
Nerve fibers
Terminal ramifications
of axis cylinders
Connective tissue sheath
Fig. 937. — Nerve ending of Ruffini. (After A. Ruffini.)
Corpuscles of Ruffini. — Rufhni described a special variety of nerve-ending in the subcuta-
neous tissue of the human finger (Fig. 93 7); they are principally situated at the junction o" the
corium with the subcutaneous tissue. They are oval in shape, and consist of strong connective-
tissue sheaths, inside which the nerve fibers divide into numerous branches, which show vari-
cosities and end in small free knobs.
The neurotendinous spindles (organs of Golgi) are chiefly found near the junctions of tendons
and muscles. Each is enclosed in a capsule which contains a number of enlarged tendon fasciculi
{intrafusal fasciculi). One or more nerve fibers perforate the side of the capsule and lose their
medullary sheaths; the axis-cylinders subdivide and end between the tendon fibers in irregular
disks or varicosities (Fig. 938).
Nerve fiber
Tendon
bundles
Organ of Golgi, showing
ramification of nerve-fibrils
Mxiscular fibers
Fig. 938. — Organ of Golgi (neurotendinous spindle) from the human tendo calcaneus. (After Ciaccio.)
The neuromuscular spindles are present in the majority of voluntary muscles, and consist
of small bundles of peculiar muscular fibers (intrafusal fibers), embryonic in type, invested by
capsules, within which nerve fibers, experimentally shown to be sensory in origin, terminate.
These neuromuscular spindles vary in length from 0.8 mm. to 5 mm., and have a distinctly
fusiform appearance. The large medullated nerve fibers passing to the end-organ are from
1062 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
one to three or four in number; entering the fibrous capsule, they divide several times, and,
losing their medullary sheaths, ultimately end in naked axis-cylinders encircUng the intrafusal
fibers by flattened expansions, or irregular ovoid or rounded disks (Fig. 939). Neuromuscular
spindles have not yet been demonstrated in the tongue muscles, and only a few exist in the
ocular muscles.
Fig. 939. — Middle third of a terminal plaque in the muscle spindle of an adult cat. (After Ruffini.)
THE COMMON INTEGUMENT (INTEGUMENTUM COMMUNE; SKIN).
The integument (Fig. 940) covers the body and protects the deeper tissues from
injury, from drying and from in^'asion by foreign organisms; it contains the per-
ipheral endings of many of the sensory ner\-es; it plays an important part in the
regulation of the body temperature, and has also limited excretory and absorbing
powers. It consists principally of a layer of vascular connective tissue, named the
corium or cutis vera, and an external covering of epithelium, termed the epidermis
or cuticle. On the surface of the former layer are sensitive and vascular papillae;
within, or beneath it, are certain organs with special functions : namely, the sudorif-
erous and sebaceous glands, and the hair follicles.
The epidermis, cuticle, or scarf skin is non-vascular, and consists of stratified
epithelium (Fig. 941), andisaccurately moulded on the papillary layer of the corium.
It varies in thickness in different parts. In some situations, as in the palms of the
hands and soles of the feet, it is thick, hard, and horny in texture. This may be in
a measure due to the fact that these parts are exposed to intermittent pressure,
but that this is not the only cause is proved by the fact that the condition exists
to a very considerable extent at birth. The more superficial layers of cells, called
the homy layer (stratum corneum), may be separated by maceration from a deeper
stratum, which is called the stratum mucosum, and which consists of several layers
of differently shaped cells. The free surface of the epidermis is marked by a
net-work of linear furrows of variable size, dividing the surface into a number of
polygonal or lozenge-shaped areas. Some of these furrows are large, as opposite the
flexures of the joints, and correspond to the folds in the corium produced by move-
ments. In other situations, as upon the back of the hand, they are exceedingly
fine, and intersect one another at various angles. Upon the palmar surfaces of the
, hands and fingers, and upon the soles of the feet, the epidermal ridges are very dis-
tinct, and are disposed in curves; they depend upon the large size and peculiar
. arrangements of the papillse upon which the epidermis is placed. The function
of these ridges is primarily to increase resistance between contact surfaces for the
purpose of preventing slipping whether in walking or prehension. The direction
of the ridges is at right angles with the force that tends to produce slipping or to
the resultant of such forces when these forces vary in direction.^ In each individual
'Whipple, Inez L., The Ventral Surface of the Mammalian Chiridium, etc., Zeit. f. Morph. u. .-Vnthropol.-
1904, vol. \-ii.
THE COMMON INTEGUMENT
1063
the Knos on the tips of the fingers and thumbs form distinct patterns unlike those of
any other person. A method of determining the identity of a criminal is based on
this fact, impressions ("finger-prints") of these lines being made on paper covered
with soot, or on white paper after first covering the fingers with ink. The deep
surface of the epidermis is accurately moulded upon the papillary layer of the
corium, the papilke being covered by a basement membrane; so that when the
epidermis is removed by maceration, it presents on its under surface a number of
pits or depressions corresponding to the papillae, and ridges corresponding to the
intervals between them. Fine tubular prolongations are continued from this
layer into the ducts of the sudoriferous and sebaceous glands.
Duct of
sudoriferous — .
gland
Tactile
corpuscle'
Duct of
sudoriferous,
gland
Adipose tissue •
Artery ■
Pacinian
corpuscle '
Stratum
coriieum
Stratrnn
hicidmn
Strain m
gramilosum
' Stratum
mucosum
Stratum
germinativum
=^ — Dermis
Sudoriferous
gland
.Nerve
Fig. 940. — A diagrammatic sectional view of the skin (magnified).
The epidermis consists of stratified epithelium which is arranged in four layers
from within outward as follows: (a) stratum mucosum, (6) stratum granulosum, (c)
stratum lucidum, and (f/) stratum corneum.
The stratum mucosum (mucuus layer) is composed of several layers of cells; those
of the deepest layer are columnar in shape and placed perpendicularly on the
surface of the basement membrane, to which they are attached by toothed extrem-
ities ; this deepest layer is sometimes termed the stratum germinativum ; the succeed-
ing strata consist of cells of a more rounded or polyhedral form, the contents of
1064 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
which are soft, opaque, granular, and sqhible in acetic acid. These are known as
prickle cells because of the bridges by which they are connected to one another.
They contain fine fibrils which are continuous across the connecting processes
with corresponding fibrils in adjacent cells. Between the bridges are fine inter-
cellular clefts serving for the passage of lymph, and in these lymph corpuscles or
pigment granules may be found.
The stratum granulosum comprises two or three layers of flattened cells which
contain granules of eleidin, a substance readily stained by hematoxylin or carmine,
and probably an intermediate substance in the formation of keratin. They are
supposed to be cells in a transitional stage between the protoplasmic cells of the
stratum mucosum and the horny cells of the superficial layers.
The stratum lucidimi appears in section as a homogeneous or dimly striated mem-
brane, composed of closely packed cells in which traces of flattened nuclei may be
found, and in which minute granules of a substance named heratohyalin are present.
Stratum comeum-
Stratum lucidum i t
Stratum granulosum ( ^■
1^'
stratum mucosum *
Stratum germinativum
" — Nerve fibrils
Fig. 941. — Section of epidermm. (Ranvier.)
The stratum comeum {horny layer) consists of several layers of horny epithelial
scales in which no nuclei are discernible, and which are unaffected by acetic acid, the
protoplasm having become changed into horny material or keratin. According to
Ranvier they contain granules of a material which has the characteristics of beeswax.
The black color of the skin in the negro, and the tawny color among some of
the white races, is due to the presence of pigment in the cells of the epidermis.
This pigment is more especially distinct in the cells of the stratum mucosum, and
is similar to that found in the cells of the pigmentary layer of the retina. As the
cells approach the surface and desiccate, the color becomes partially lost; the
disappearance of the pigment from the superficial layers of the epidermis is,
however, difficult to explain.
The pigment (melanin) consists of dark bro-vMi or black granules of very small
size, closely packed together within the cells, but not in\olving the nucleus.
The main purpose served by the epidermis is that of protection, as the surface
is worn away new cells are supplied and thus the true skin, the vessels and nerves
which it contains are defended from damage.
THE COMMON INTEGUMENT
1065
The Corium, Cutis Vera, Dermis, or True Skin is tough, flexible, and highly
elastic. It varies in thickness in different parts of the body. Thus it is very
thick in the palms of the hands and soles of the feet; thicker on the posterior aspect
of the body than on the front, and on the lateral than on the medial sides of the
limbs. In the eyelids, scrotum, and penis it is exceedingly thin and delicate.
It consists of felted connective tissue, with a varying amount of elastic fibers
and numerous bloodvessels, lymphatics, and nerves. The connective tissue is
arranged in two layers: a deeper or reticular, and a superficial or papillary. Un-
striped muscular fibers are found in the superficial layers of the corium, wherever
hairs are present, and in the subcutaneous areolar tissue of the scrotum, penis,
labia majora, and nipples. In the nipples the fibers are disposed in bands, closely
reticulated and arranged in superimposed laminae.
RETE
VENOSUM
\
SUBPAPILLARY
NETWORK
-EPIDERMIS
PAPILLARY LAYER-
RETE
VENOSUM
RETE
VENOSUM
Fig. 942. — The distribution of the bloodvessels in the skin of the sole of the foot. (Spaltcholz.)
The reticular layer (stratum reticulare; deep layer) consists of strong interlacing
bands, composed chiefly of white fibrous tissue, but containing some fibers of yellow
elastic tissue, which -vary in number in different parts; and connective-tissue cor-
puscles, which are often to be found flattened against the white fibrous tissue bundles.
Toward the attached surface the fasciculi are large and coarse, and the areolae
left by their interlacement are large, and occupied by adipose tissue and sweat
glands. Below the reticular layer is the subcutaneous areolar tissue, which, except
in a few situations, contains fat.
The papillary layer {stratum papiUare; superficial layer; corpus pap'dlare of the
corium) consists of numerous small, highly sensitive, and vascular eminences,
the papillae, which rise perpendicularly from its surface. The papillae are minute
conical eminences, having rounded or blunted extremities, occasionally divided
into two or more parts, and are received into corresponding pits on the under
surface of the cuticle. On the general surface of the body, more especially in parts
endowed with slight sensibility, they are few in number, and exceedingly minute; but
in some situations, as upon the palmar surfaces of the hands and fingers, and upon
the plantar surfaces of the feet and toes, they are long, of large size, closely aggre-
gated together, and arranged in parallel curved lines, forming the elevated ridges
1066 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
seen on the free surface of the epidermis. Each ridge contains two rows of papillae,
between which the ducts of the sudoriferous glands pass outward to open on the
summit of the ridge. Each papilla consists of very small and closely interlacing
bundles of finely fibrillated tissue, with a few elastic fibers; within this tissue is a
capillary loop, and in some papillae, especially in the palms of the hands and the
fingers, there are tactile corpuscles.
Development. — The epidermis and its appendages, consisting of the hairs, nails,
sebaceous and sweat glands, are developed from the ectoderm, while the corium or
true skin is of mesodermal origin. About, the fifth week the epidermis consists of
two layers of cells, the deeper one corresponding to the rete mucosum. The subcuta-
neous fat appears about the fourth month, and the papilla? of the true skin about the
sixth. A considerable desquamation of epidermis takes place during fetal life, and
this desquamated epidermis, mixed with sebaceous secretion, constitutes the vernix
caseosa, with which the skin is smeared during the last three months of fetal life. The
nails are formed at the third month, and begin to project from the epidermis about
the sixth. The hairs appear between the third and fourth months in the form of
solid downgrowths of the deeper layer of the epidermis, the growing extremities
of which become inverted by papillary projections from the corium. The central
cells of the solid downgrowths undergo alteration to form the hair, while the
peripheral cells are retained to form the lining cells of the hair-follicle. About the
fifth month the fetal hairs (lanugo) appear, first on the head and then on the other
parts; they drop off after birth, and give place to the permanent hairs. The cellular
structures of the sudoriferous and sebaceous glands are formed from the ectoderm,
while the connective tissue and bloodvessels are derived from the mesoderm. All
the sweat-glands are fully formed at birth; they begin to develop as early as the
foiu-th month.
The arteries supplying the skin form a net-work in the subcutaneous tissue, and from this
net-work branches are given off to supply the sudoriferous glands, the hair follicles, and the
fat. Other branches unite in a plexus immediately beneath the corium; from this plexus, fine
capillary vessels pass into the papilhe, forming, in the smaller ones, a single capillary loop, but
in the larger, a more or less convoluted vessel. The lymphatic vessels of the skin form two
net-works, superficial and deep, which communicate with each other and with those of the sub-
cutaneous tissue by oblique branches.
The nerves of the skin terminate partly in the epidermis and partly in the corium; their different
modes of ending are described on pages 1059 to 1061.
THE APPENDAGES OF THE SKIN.
The appendages of the skin are the nails, the hairs, and the sudoriferous and
sebaceous glands with their ducts.
The Nails (ungues) (Fig. 943) are flattened, elastic structures of a horny texture,
placed upon the dorsal surfaces of the terminal phalanges of the fingers and toes.
Each nail is convex on its outer surface, concave within, and is implanted by a
portion, called the root, into a groove in the skin; the exposed portion is called the
body, and the distal extremity the free edge. The nail is firmly adherent to the
corium, being accurately moulded upon its surface; the part beneath the body and
roof of the nail is called the nail matrix, because from it the nail is produced. Under
the greater part of the body of the nail, the matrix is thick, and raised into a series
of longitudinal ridges which are very vascular, and the color is seen through the
transparent tissue. Near the root of the nail, the papillae are smaller, less vascular,
and have no regular arrangement, and here the tissue of the nail is not firmly
adherent to the connective-tissue stratum but only in contact with it; hence this
portion is of a whiter color, and is called the lunula on account of its shape.
The cuticle as it passes forward on the dorsal surface of the finger or toe is
attached to the surface of the nail a little in advance of its root; at the extremity of
THE APPENDAGES OF THE SKIN
1067
the finger it is connected with the under surface of the nail a little beliind its free
edge. The cuticle and the horny substance of the nail (both epidermic structures)
are thus directly continuous with each other. The superficial, horny part of the
nail consists of a greatly thickened stratum iucidum, the stratum corncum forming
merely the thin cuticular fold (eponychium) which overlaps the lunula; the deeper
part consists of the stratum mucosum. The cells in contact with the papillse of the
matrix are columnar in form and arranged perpendicularly to the surface; those
which succeed them are of a rounded or polygonal form, the more superficial ones
becoming broad, thin, and flattened, and so closely packed as to make the limits
of the cells very indistinct. The nails grow in length by the proliferation of the
cells of the stratum mucosum at the root of the nail, and in thickness from that
part of the stratum mucosum which underlies the lunula.
Eponychium «^
^'ail ,
Stratum
mucusum '
Stratum cor-
neum of the'
nail groove
stratum
corneum,
^«> Stratum
granalosum
■ O-
O ■ .."'__ — Cerium
Blood-vessel
Fig. 943. — Longitudinal section through nail and its nail groove (sulcus).
Hairs {pili) are found on nearly every part of the surface of the body, but are
absent from the palms of the hands, the soles of the feet, the dorsal surfaces of the
terminal phalanges, the glans penis, the inner surface of the prepuce, and the
inner surfaces of the labia. They vary much in length, thickness, and color in
different parts of the body and in different races of mankind. In some parts, as
in the skin of the eyelids, they are so short as not to project beyond the follicles
containing them; in others, as upon the scalp, they are of considerable length;
again, in other parts, as the eyelashes, the hairs of the pubic region, and the whiskers
and beard, they are remarkable for their thickness. Straight hairs are stronger
than curly hairs, and present on transverse section a cylindrical or oval outline;
curly hairs, on the other hand, are flattened. A hair consists of a root, the part im-
planted in the skin; and a shaft or scapus, the portion projecting from the surface.
The root of the hair (radix pili) ends in an enlargement, the hair bulb, which is
whiter in color and softer in texture than the shaft, and is lodged in a follicular
involution of the epidermis called the hair follicle (Fig. 944). When the hair is of
considerable length the follicle extends into the subcutaneous cellular tissue. The
hair follicle commences on the surface of the skin with a funnel-shaped opening,
and passes inward in an oblique or curved direction — the latter in curly hairs — to
become dilated at its deep extremity, where it corresponds with the hair bulb.
Opening into the follicle, near its free extremity, are the ducts of one or more
sebaceous glands. At the bottom of each hair follicle is a small conical, vascular
eminence or papilla, similar in every respect to those found upon the surface of the
skin; it is continuous with the dermic layer of the follicle, and is supplied with
nerve fibrils. The hair follicle consists of two coats — an outer or dermic, and an
inner or epidermic.
The outer or dermic coat is formed mainly of fibrous tissue; it is continuous
with the corium, is highly vascular, and supplied by* numerous minute nervous
filaments. It consists of three layers (Fig. 945). The most internal is a hyaline
basement membrane, which is well-marked in the larger hair follicles, but is not
1068 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
very distinct in the follicles of minute hairs; it is limited to the deeper part of the
follicle. Outside this is a compact layer of fibers and spindle-shaped cells arranged
circularly around the follicle; this layer extends from the bottom of the follicle
as high as the entrance of the ducts of the sebaceous glands. Externally is a thick
layer of connective tissue, arranged in longitudinal bundles, forming a more
open texture and corresponding to the reticular part of the corium; in this are
contained the bloodvessels and nerves.
Dermis — •^'Jzus^'-^
Sebaceous gland — •'iS^^^y^;^^'
Cortex of hair
Vessel
Dermic coat
Inner root sheath,
Outer root sheath
Bvlb of hair
Pajnlla of hair
Stratum corneum
~ Stratum lucidum
Stratum granulosum
Stratum 7tiucosum
Stratum
germinativum
Arrector pili
mziscle
■ Dermic coat
• Medulla of hair
Fig. 944.
-.Section of skin, showing the epidermis and dermis; a hair in its follicle; the Arrector pili muscle;
sebaceous glands.
The inner or epidermic coat is closely adherent to the root of the hair, and con-
sists of two strata named respectively the outer and inner root sheaths ; the former
of these corresponds with the stratum mucosum of the epidermis, and resembles
it in the rounded form and soft character of its cells; at the bottom of the hair
follicle these cells become continuous with those of the root of the hair. The inner
root sheath consists of (1) a delicate cuticle next the hair, composed of a single
layer of imbricated scales with atrophied nuclei; (2) one or two layers of horny,
flattened, nucleated cells, known as Huxley's layer; and (3) a single layer of cubical
cells with clear flattened nuclei, called Henle's layer.
The hair bulb is moulded over the papilla and composed of polyhedral epithelial
cells, which as they pass upward into the root of the hair become elongated and
spindle-shaped, except some in the center which remain polyhedral. Some of
these latter cells contain pigment granules which give rise to the color of the hair.
It occasionally happens that these pigment granules completely fill the cells in
THE APPENDAGES OF THE SKIN
10(39
Byaline layer — -- -
Cortex
of hair
Medulla
ofJiuir
Hvxley's
layer
Henle'-i layer
Outer or
dermic coat
the center of the bulb; this gives rise to the dark tract of pigment often found,
of greater or less length, in the axis of the hair.
The shaft of the hair (scapus pili) consists, from within outward, of three parts,
the me(hilla, the cortex, and the cuticle. The medulla is usually' wanting in the
fine hairs covering the surface of
the body, and commonly in those
of the head. It is more opaque
and deeper colored than the cor-
tex when viewed by transmitted
light; but when viewed by re-
flected light it is white. It is
composed of rows of polyhedral
cells, containing granules of elei-
din and frequently air spaces.
The cortex constitutes the chief
part of the shaft; its cells are
elongated and united to form
flattened fusiform fibers which
contain pigment granules in dark
hair, and air in white hair. The
cuticle consists of a single layer
of flat scales which overlap one
another from below upward.
Connected with the hair fol-
licles are minute bundles of in-
voluntary muscular fibers, termed
the Arrectores pilorum. They
arise from the superficial layer
of the corium, and are inserted
into the hair follicle, below the
entrance of the duct of the seba-
ceous gland. They are placed on
the side toward which the hair
slopes, and by their action diminish the obliquity of the follicle and elevate the
hair (Fig. 944). ^ The sebaceous gland is situated in the angle which the Arrector
muscle forms with the superficial portion of the hair follicle, and contraction of the
muscle thus tends to squeeze the sebaceous secretion out from the duct of the gland.
The Sebaceous Glands {glanduloe sehaceoe) are small, sacculated, glandular
organs, lodged in the substance of the corium. The}' are found in most parts of
the skin, but are especially abundant in the scalp and face; they are also very
numerous around the apertures of the anus, nose, mouth, and external ear, but are
wanting in the palms of the hands and soles of the feet. Each gland consists of a
single duct, more or less capacious, which emerges from a cluster of oval or flask-
shaped alveoli which vary from two to five in number, but in some instances there
may be as many as twenty. Each alveolus is composed of a transparent basement
membrane, enclosing a number of epithelial cells. The outer or marginal cells
are small and polyhedral, and are continuous with the cells lining the duct. The
remainder of the alveolus is filled with larger cells, containing fat, except in the
center, where the cells have become broken up, leaving a cavity filled with their
debris and a mass of fatty matter, which constitutes the sebum cutaneum. The
ducts open most frequently into the hair ft)llicles, but occasionally upon the general
surface, as in the labia minora and the free margin of the lips. On the nose and face
Fig. 945. — Transverse section of hair follicle.
' Professor Arthur Thomson, of Oxford, suggests that the contraction of these muscles on follicles which contain
weak, flat hairs will tend to produce a permanent curve in the follicle, and this curve will be impressed on the hair
which ia moulded within it, so that the hair, on emerging through the skin, will be curled. Curved hair follicles are
characteristic of the scalp of the Bushman.
1070 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT
the glands are of large size, distinctly lobulated, and often become much enlarged
from the accumulation of pent-up secretion. The tarsal glands of the eyelids are
elongated sebaceous glands with numerous lateral diverticula.
The Sudoriferous or Sweat Glands (gland ulcp sudoriferw) are found in almost
every part of the skin, and are situated in small pits on the under surface of the
corium, or, more frequently, in the subcutaneous areolar tissue, surrounded by a
quantity of adipose tissue. Each consists of a single tube, the deep part of which
is rolled into an oval or spherical ball, named the body of the gland, while the super-
ficial part, or duct, traverses the corium
--::^?=?^5.=^.( ,^^l^ and cuticle and opens on the surface of
iS^ ^ -<Tsggg^^^^^->l^^^P" the skin by a funnel-shaped aperture.
^^^s<rxg^^^^^^^^^^^^^^ In the superficial layers of the corium
.^^^^^^^^^^^^-^^^^^^^T^'^^^s the duct is straight, but in the deeper
^^^^^^^^^^^^^ '•) .^^ / layers it is convoluted or even twisted ;
"^^^^^^'^^^^^f^^^^^'^^^C^^^^^'^^ where the epidermis is thick, as in the
^^-5^ l^^i^^'' ^{W^f^iX...^^^ palms of the hands and soles of the feet,
'^£-^ii^>^s^^^' ') wN V_X-=.-C— ^ *^^^ P''^^^ ^^ ^^^^ ^^^^ which passes through
^^^^^^^"^^''/"^iQ^^^^^^i^- ^^ ^^ spirally coiled. The size of the
\/w^->\fi^||^ glands varies. They are especially large
AN^^^^^^^v V iK^X^'^!^ in those regions where the amount of
</' -^N^^^nlw •' )/ ' v^(^i^^ d perspiration is great, as in the axillae,
^%_^^^^^y] (^ where they form a thin, mammillated
Fig. 946.— Body of ,1 sudoriferous-gland cut in various laVCr of arcddish Color, which COrfC-
directions. a. Longitudinal section of the proximal part cr>r>nr1c f^vintK'- +r> -the^ cifiiQ + inn r>f +Vif>
of the coiled tube. b. Transverse section of the same. ^pOUUb CXdCtl^^ tO Xne bltUdllOn OI tne
c. Longitudinal section of the distal part of the coiled i^^ir iu this Tcgiou ; thcv are large also
tube. d. Transverse section of the same. (Klein and , . " ' ., o _
Noble Smith.) in the grom. Their number varies.
They are very plentiful on the palms
of the hands, and on the soles of the feet, where the orifices of the ducts are exceed-
ingly regular, and open on the curved ridges; they are least numerous in the neck
and back. On the palm there are about 370 per square centimeter; on the back of
the hand about 200; forehead 175, breast, abdomen and forearm 155, and on the
leg and back from GO to SO per square centimeter. Krause estimates the total
number at about 2,000,000. The average number of sweat glands per square
centimeter of skin area in various races as shown by the fingers is as follows ■}
American (white) 558.2
American (negro) 597.2
Filipino 653.6
Moro 684.4
Negrito (adult) 709.2
Hindu 7:«.2
Negrito (youth) 950.0
They are absent in the deeper portion of the external auditory meatus, the pre-
puce and the glans penis. The tube, both in the body of the gland and in the duct
consists of two layers — ^an outer, of fine areolar tissue, and an inner of epithelium
(Fig. 946). The outer layer is thin and is continuous with the superficial stratum of
the corium. In body of the gland the epithelium consists of a single layer of cubical
cells, between the deep ends of which and the basement membrane is a layer
of longitudinally or obliquely arranged non-striped muscular fibers. The ducts are
destitute of muscular fibers and are composed of a basement membrane lined by two
or three layers of polyhedral cells; the lumen of the duct is coated by a thin cuticle.
When the cuticle is carefullv removed from the surface of the corium, the ducts
may be drawn out in the form of short, thread-like processes on its under surface.
The ceruminous glands of the external acoustic meatus and the ciliary glands at
the margins of the eyelids are modified sudoriferous glands.
' Clark and Lhamon, Anatomical Record, 1917, xii.
SPLANCHNOLOGY.
TINDER this heading are inchided the respiratory, digestive, and urogenital
^ organs, and the ductless glands.
THE RESPIRATORY APPARATUS (APPARATUS RESPIRATORIUS ;
RESPIRATORY SYSTEM i.
The respiratory apparatus consists of the larynx, trachea, bronchi, lungs, and
pleurae.
Development. — The rudiment of the respiratory organs appears as a median
longitudinal groove in the ventral wall of the pharynx. The groove deepens
and its lips fuse to form a septum which grows from below upward and con-
verts the groove into a tube, the laryngo-tracheal tube (Fig. 947), the cephalic
Mouth of olfactory fit
Mediaii part of fronto-
iiatfal process
Processus gldbulari
Hypophysis
\st branchial pouch
Sinus cervical is
Laryngo-tracheal tube
Lung
Eye
Maxillary process
Mandibular arch
Future tympanic
membrane
Hyoid arch
Third arch
Fourth arch
Fig. 947. — The head and neck of a human embryo thirty-two days old, seen from the ventral surface. The floor of
the mouth and pharynx have been removed. (His.)
end of which opens into the pharynx by a slit-like aperture formed by the persistent
anterior part of the groove. The tube is lined by entoderm from which the epithe-
lial lining of the respiratory tract is developed. The cephalic part of the tube
becomes the larynx, and its next succeeding part the trachea, while from its caudal
end two lateral outgrowths, the right and left lung buds, arise, and from them the
bronchi and lungs are developed. The first rudiment of the larynx consists of two
arytenoid swellings, which appear, one on either side of the cephalic end of the laryngo-
tracheal groove, and are continuous in front of the groove with a transverse ridge
(furcula of His) which lies between the ventral ends of the third branchial arches
and from which the epiglottis is subsequently developed (Figs. 980, 981). After
the separation of the trachea from the esophagus the arytenoid swellings come
( 1071 )
1072
SPLANCHNOLOGY
into contact with one another and with the back of the epiglottis, and the entrance
to the larynx assumes the form of a T-shaped cleft, the margins of the cleft adhere
to one another and the laryngeal entrance is for a time occluded. The mesodermal
wall of the tube becomes condensed to form the cartilages of the larynx and trachea.
The ar^'tenoid swellings are differentiated into the arytenoid and corniculate car-
tilages, and the folds joining them to the epiglottis form the aryepiglottic folds
in which the cuneiform cartilages are developed as derivatives of the epiglottis.
The thyroid cartilage appears as two lateral plates, each chondrified from two
centers and united in the mid-ventral line by membrane in which an additional
center of chondrification develops. The cricoid cartilage arises from two cartil-
aginous centers, which soon unite ventrally and gradually extend and ultimately
fuse on the dorsal aspect of the tube.
J. Ernest Frazer^ has made an important investigation on the development of the larynx
and the following are his main conclusions:
The opening of the pulmonary diverticulum lies between the two fifth arch masses and behind
a "central mass" in the middle line — the proximal end of the diverticulum is compressed between
the fifth arch masses. The fifth arch is joined by the fourth to form a "lateral mass" on each
side of the opening, and these "lateral masses" grow forward and overlap the central mass and
so form a secondary transverse cavity, which is really a part of the cavity of the pharynx. The
two parts of the cavity of the larynx are separated in the adult by a line drawn back along the
vocal fold and then upward along the border of the arytenoid eminence to the interarytenoid
notch. The arytenoid and cricoid are developed in the fifth arch mass. The thyroid is primarily
a fourth arch derivative, and if it has a fifth arch element this is a later addition. The epiglottis
is derived from the "central mass," and has a third arch element in its oral and upper aspect;
the arch value of the "central mass" is doubtful.
Fig. 948. — Lung buds from a human embryo of
about four weeks, showing commencing lobulations.
^Hia.)
. \ %^-J^
Fig. 949. — Lungs of a human embryo more
advanced in development. (His.)
The right and left lung buds grow out behind the ducts of Cuvier, and are at
first symmetrical, but their ends soon become lobulated, three lobules appearing
on the right, and two on the left; these subdivisions are the early indications of the
corresponding lobes of the lungs (P'igs. 948, 949). The buds undergo further sub-
division and ramification, and ultimately end in minute expanded extremities —
the infundibula of the lung. After the sixth month the air-sacs begin to make their
appearance on the infundibula in the form of minute pouches. The pulmonary
arteries are derived from the sixth aortic arches. During the course of their
development the lungs migrate in a caudal direction, so that by the time of birth
the bifurcation of the trachea is opposite the fourth thoracic vertebra. As the
lungs grow they project into that part of the celom which will ultimately form the
pleural cavities, and the superficial layer of the mesoderm enveloping the lung
rudiment expands on the growing lung and is converted into the pulmonary pleura.
THE LARYNX.
The larynx or organ of voice is placed at the upper part of the air passage.
It is situated between the trachea and the root of the tongue, at the upper and
' Journal of Anatomy and Physiology, vol. xliv.
THE LARYNX 1073
forepart of the neck, where it presents a considerable projection in the middle
line. It forms the lower part of the anterior wall of the pharynx, and is covered
behind by the mucous lining of that cavity; on either side of it lie the great vessels
of the neck. Its vertical extent corresponds to the fourth, fifth, and sixtR cervical
vertebrae, but it is placed somewhat higher in the female and also during childhood.
Symington found that in infants between six and twelve months of age the tip
of the epiglottis was a little above the level of the fibrocartilage between the
odontoid process and body of the axis, and that between infancy and adult life
the larynx descends for a distance equal to two vertebral bodies and two inter-
vertebral fibrocartilages. According to Sappey the average measurements of the
adult larynx are as follows:
In males. In females.
Length -44 mm. 36 mm.
Transverse diameter .... 43 " 41 "
Antero-posterior diameter ... 36 " 26 "
Circumference . . . . 136 " 112 "
Until puberty the larynx of the male differs little in size from that of the female. In the
female its increase after puberty is only slight; in the male it undergoes considerable increase;
all the cartilages are enlarged and the thyroid cartilage becomes prominent in the middle line of
the neck, while the length of the rima glottidis is nearly doubled.
The larynx is broad above, where it presents the form of a triangular box flattened
behind and at the sides, and bounded in front by a prominent vertical ridge.
Below, it is narrow and cylindrical. It is composed of cartilages, which are con-
nected together by ligaments and moved by numerous muscles. It is lined by
mucous membrane continuous above with that of the pharynx and below with
that of the trachea.
The Cartilages of the Larynx (cartilagines laryngis) (Fig. 950) are nine in number,
three single and three paired, as follows:
Thyroid. Two Corniculate.
Cricoid. Two Cuneiform.
Two Arytenoid. Epiglottis.
The Thyroid Cartilage {cartilago thyreoidea) is the largest cartilage of the larynx.
It consists of two laminae the anterior borders of which are fused with each other
at an acute angle in the middle line of the neck, and form a subcutaneous projec-
tion named the laryngeal prominence (pomum Adami). This prominence is most
distinct at its upper part, and is larger in the male than in the female. Immediately
above it the laminae are separated by a V-shaped notch, the superior thyroid notch.
The laminae are irregularly quadrilateral in shape, and their posterior angles are
prolonged into processes termed the superior and inferior cornua.
The outer surface of each lamina presents an oblique line which runs downward
and forward from the superior thyroid tubercle situated near the root of the
superior cornu, to the inferior thyroid tubercle on the lower border. This line
gives attachment to the Sternothyreoideus, Thyreohyoideus, and Constrictor
pharyngis inferior.
The inner surface is smooth; above and behind, it is slightly concave and covered
by mucous membrane. In front, in the angle formed by the junction of the laminae,
are attached the stem of the epiglottis, the ventricular and vocal ligaments, the
Thyreoarytaenoidei, Thyreoepiglottici and Vocales muscles, and the thyroepiglottic
ligament.
The upper border is concave behind and convex in front; it gives attachment to
the corresponding half of the hyothyroid membrane.
The lower border is concave behind, and nearly straight in front, the two parts
being separated by the inferior thyroid tubercle. A small part of it in and near
68
1074
SPLANCHNOLOGY
EPIGLOTTIS
THYROID
Cornicvlate cartilages
the middle line is connected to the cricoid cartilage by the middle cricothyroid
ligament.
The posterior border, thick and rounded, receives the insertions of the Stylo-
pharyngeus and Pharyngopalatinus. It ends above, in the superior cornu, and
below, in the inferior cornu. The
superior cornu is long and narrow,
directed upward, backward, and
medialward, and ends in a conical
extremity, Avhich gives attachment
to the lateral hyothyroid ligament.
The inferior cornu is short and thick;
it is directed downward, with a slight
inclination forward and medialward,
and presents, on the medial side of
its tip, a small oval articular facet
for articulation with the side of the
cricoid cartilage.
During infancy the laminse of the
thyroid cartilage are joined to each
other by a narrow, lozenge-shaped
strip, named the intrathyroid cartil-
age. This strip extends from the
upper to the lower border of the
cartilage in the middle line, and is
distinguished from the laminae by
being more transparent and more
flexible.
The Cricoid Cartilage (cartilago
cricoidea) is smaller, but thicker and
stronger than the thyroid, and forms
the lower and posterior parts of the
wall of the larynx. It consists of two
parts: a posterior quadrate lamina,
and a narrow anterior arch, one-
fourth or one-fifth of the depth of
the lamina.
The lamina {lamina cartilaginis
cricoidea; posterior 'portion) is deep
and broad, and measures from above
downward about 2 or 3 cm.; on its
posterior surface, in the middle line,
is a vertical ridge to the lower part
of which are attached the longitu-
dinal fibers of the esophagus; and on either side of this a broad depression for the
Cricoaryttenoideus posterior.
The arch {arcus cartilaginis cricoidea^; anterior portion) is narrow and convex,
and measures verticalh' from 5 to 7 mm. ; it affords attachment externallv in front
and at the sides to the Cricothyreiodei, and behind, to part of the Constrictor
pharyngis inferior.
On either side, at the junction of the lamina with the arch, is a small round
articular surface, for articulation with the inferior cornu of the thyroid cartilage.
The lower border of the cricoid cartilage is horizontal, and connected to the
highest ring of the trachea by the cricotracheal ligament.
The upper border runs obliquely upward and backward, owing to the great
Cuneiform cartilage
ARYTENOID
Insertion of
Cricoaryta;noidcus
posterior
Posterior
surface
Arytenoid cartilages, base
CRICOID
Articiilar facet for
arytenoid cartilage
Articular facet for
inferior cornu of
thyroid cartilage
Fio. 950. — The cartilages of tlie larj'nx. Posterior \4ew.
THE LARYNX 1075
depth of the lamina. It gives attachment, in front, to the middle cricothyroid
ligament; at the side, to the conus elasticus and the Cricoarytsenoidei laterales;
behind, it presents, in the middle, a shallow notch, and on either side of this is a
smooth, oval, convex surface, directed upward and lateralward, for articulation
with the base of an arytenoid cartilage.
The inner surface of the cricoid cartilage is smooth, and lined by mucous
membrane.
The Arytenoid Cartilages {cartUagines nrytfrnnideo') are two in number, and sit-
uated at the upper border of the lamina of the cricoid cartilage, at the back of
the larynx. Each is pyramidal in form, and has three surfaces, a base, and an
apex.
The posterior surface is a triangular, smooth, concave, and gives attachment
to the ArytaMioidei obliquus and transversus.
The antero-lateral surface is somewhat convex and rough. On it, near the apex
of the cartilage, is a rounded elevation (colliculus) from which a ridge (crista arcuata)
curves at first backward and then downward and forward to the vocal process.
The lower part of this crest intervenes between two depressions or foveas, an
upper, triangular, and a lower oblong in shape; the latter gives attachment to the
Vocalis muscle.
The medial surface is narrow, smooth, and flattened, covered by mucous mem-
brane, and forms the lateral boundary of the intercartilaginous part of the rima
glottidis.
The base of each cartilage is broad, and on it is a concave smooth surface,
for articulation with the cricoid cartilage. Its lateral angle is short, rounded,
and prominent; it projects backward and lateralward, and is termed the muscular
process; it gives insertion to the Cricoaryta^noideus posterior behind, and to the
Cricoarytienoideus lateralis in front. Its anterior angle, also prominent, but more
pointed, projects horizontal!}' forward; it gives attachment to the vocal ligament,
and is called the vocal process.
The apex of each cartilage is pointed, curved backward and medialward, and
surmounted by a small conical, cartilaginous nodule, the comiculate cartilage.
The Corniculate Cartilages {cart Hag hies corniculatw; cartilages of Santorini) are
two small conical nodules consisting of yellow elastic cartilage, which articulate
with the summits of the arytenoid cartilages and serve to prolong them backward
and medialward. They are situated in the posterior parts of the aryepiglottic
folds of raucous membrane, and are sometimes fused with the arytenoid cartilages.
The Cimeiform Cartilages {cartUagines cuneiformes ; cartilages of Wrishcrg) are two
small, elongated pieces of yellow elastic cartilage, placed one on either side, in the
aryepiglottic fold, where they give rise to small whitish elevations on the surface
of the mucous membrane, just in front of the arytenoid cartilages.
The Epiglottis {cartilago epiglottica) is a thin lamella of fibrocartilage of a yel-
lowish color, shaped like a leaf, and projecting obliquely upward behind the root
of the tongue, in front of the entrance to the larynx. The free extremity is broad
and rounded; the attached part or stem is long, narrow, and connected by the
thyroepiglottic ligament to the angle formed by the two laminse of the thyroid
cartilage, a short distance below the superior thyroid notch. The lower part of
its anterior surface is connected to the upper border of the body of the hyoid
bone by an elastic ligamentous band, the hyoepiglottic ligament.
The anterior or lingual surface is curved forward, and covered on its upper, free
part by mucous membrane which is reflected on to the sides and root of the tongue,
forming a median and two lateral glossoepiglottic folds; the lateral folds are partly
attached to the wall of the pharynx. The depressions between the epiglottis and
the root of the tongue, on either side of the median fold, are named the valleculae.
The lower part of the anterior surface lies behind the hyoid bone, the hyothyroid
1076
SPLANCHNOLOGY
membrane, and upper part of the thyroid cartilage, but is separated from these
structures })y a mass of fatty tissue.
The posterior or laryngeal surface is smooth, concave from side to side, concavo-
convex from above downward; its lower part projects backward as an elevation,
the tubercle or cushion. When the mucous membrane is removed, the surface of
the cartilage is seen to be indented by a number of small pits, in which mucous
glands are lodged. To its sides the aryepiglottic folds are attached.
Structure. — The corniculate and cuneiform cartilages, the epiglottis, and the apices of the
arytenoids at first consist of hyaline cartilage, but later clastic fibers are deposited in the matrix,
converting them into yellow fibrocartilage, which shows little tendency to calcification. The
thjToid, cricoid, and the greater part of the arytenoids consist of hyaline cartilage, and become
more or less ossified as age advances. Ossification commences about the twenty-fifth year in
the thjToid cartilage, and somewhat later in the cricoid and arytenoids; by the sixty-fifth year
these cartilages may be completely converted into bone.
Lateral kyothyroid limment
Internal laryngeal nerve
Cartilago triticea
Su2)eri(>r laryngeal artery
Superior cornu
Thyroid notch
Oblique line
Conus elasticua (lateral parts)
— Middle cricothyroid ligament
Inferior cornu
Fio. 951. — The ligaments of t!ie larynx. Antero-lateral view.
Ligaments. — The ligaments of the larynx (Figs. 951, 952) are extrinsic, i. e., those
connecting the thyroid cartilage and epiglottis with the hyoid bone, and the cricoid
cartilage with the trachea; and intrinsic, those which connect the several cartilages
of the larynx to each other.
Extrinsic Ligaments. — The ligaments connecting the thyroid cartilage with the
hyoid bone are the hyothyroid membrane, and a middle and two lateral hyo-
thyroid ligaments.
The Hyothyroid Membrane [memhrana hyothyreoidca; thyrohyoid membrane) is
a broad, fibro-elastic layer, attached below to the upper border of the thyroid
cartilage and to the front of its superior cornu, and above to the upper margin of
the posterior surface of the body and greater cornua of the hyoid bone, thus passing
behind the posterior surface of the body of the hyoid, and being separated from it
THE LARYNX
10
/ i
by a mucous bursa, which facilitates the upward movement of the larynx flurin<j
deglutition. Its middle thicker part is termed the middle hyothyroid ligament
{ligamentum hyothyreoideum medium; middle thyrohyoid ligament), its lateral thinner
portions are pierced by the superior laryngeal vessels and the internal branch of
the superior laryngeal nerve. Its anterior surface is in relation with the Thyreo-
hyoideus, Sternohyoideus, and Omohvoideus, and with the bod\- of the hvoid
bone.
The Lateral Hyothyroid Ligament {ligamentum hyothyreoideum laterale; lateral
thyrohyoid ligament) is a round elastic cord, which forms the posterior border
of the hyothyroid m-^mbrane and passes between the tip of the superior cornu of
the thyroid cartilage and the extremity of the greater cornu of the hyoid bone.
A small cartilaginous nodule (cartilago iriticea), sometimes bony, is frequently
found in it.
Cartilago triticea
— Byolhyroid membrane
Comiculate cartilage
Arytenoid
Posterior crico-arytenotd
ligament
_ Cricothyroid
articulation
Fig. 952. — Ligaments of the larj'nx. Posterior view.
The Epiglottis is connected with the hyoid bone by an elastic band, the hyo-
epiglottic ligament {ligamentuvi hyoepiglotticnim), which extends from the anterior
surface of the epiglottis to the upper border of the body of the hyoid bone. The
glossoepiglottic folds of mucous membrane (page 1075) may also be considered
as extrinsic ligaments of the epiglottis.
The Cricotracheal Ligament (ligamentum cricotracheale) connects the cricoid car-
tilage with the first ring of the trachea. It resembles the fibrous membrane which
connects the cartilaginous rings of the trachea to each other.
Intrinsic Ligaments. — Beneath the mucous membrane of the larynx is a broad
sheet of fibrous tissue containing many elastic fibers, and termed the elastic membrane
of the larynx. It is subdivided on either side by the interval between the ven-
1078 SPLANCHNOLOGY
tricular and vocal ligaments, the upper portion extends between the arytenoid
cartilage and the epiglottis and is often poorly defined; the lower part is a well-
marked membrane forming, with its fellow of the opposite side, the conus elasticus
which connects the thyroid, cricoid, and arytenoid cartilages to one another.
In addition the joints between the individual cartilages are provided with ligaments.
The Conus Elasticus (cricothyroid membrane) is composed mainly of yellow elastic
tissue. It consists of an anterior and two lateral portions. The anterior part or
middle cricothyroid ligament {ligamentnm cricothyreoidenm viediiim; central part of
cricothyroid membrane) is thick and strong, narrow above and broad below. It
connects together the front parts of the contiguous margins of the thyroid and
cricoid cartilages. It is overlapped on either side by the Cricothyreoideus, but
between these is subcutaneous; it is crossed horizontally by a small anastomotic
arterial arch, formed by the junction of the two cricothyroid arteries, branches
of which pierce it. The lateral portions are thinner and lie close under the mucous
membrane of the larynx; they extend from the superior border of the cricoid cartil-
age to the inferior margin of the vocal ligaments, with which they are continuous.
These ligaments may therefore be regarded as the free borders of the lateral por-
tions of the conus elasticus, and extend from the vocal processes of the arytenoid
cartilages to the angle of the thyroid cartilage about midway between its upper
and lower borders.
An articular capsule, strengthened posteriorly by a well-marked fibrous band,
encloses the articulation of the inferior cornu of the thyroid with the cricoid car-
tilage on either side.
Each arytenoid cartilage is connected to the cricoid by a capsule and a posterior
cricoarytenoid ligament. The capsule (capsula articidaris cricoarytenoidea) is thin
and loose, and is attached to the margins of the articular surfaces. The posterior
cricoarytenoid ligament {ligamentnm cricoarytenoiderim posterius) extends from the
cricoid to tlie medial and back part of the base of the arytenoid.
The thyroepiglottic ligament {ligamentnm thyrcocpiglotticum) is a long, slender,
elastic cord which connects the stem of the epiglottis with the angle of the thyroid
cartilage, immediately beneath the superior thyroid notch, above the attachment
of the ventricular ligaments.
Movements. — The articulation between the inferior cornu of the thjToid cartilage and the
cricoid cartilage on either side is a diarthrodial one, and permits of rotatory and gliding move-
ments. The rotatory movement is one in which the cricoid cartilage rotates upon the inferior
cornua of the thjToid cartilage around an axis passing transversely through both joints.
The gliding movement consists in a limited shifting of the cricoid on the thyroid in different
directions. ♦
The articulation between the arj'^tenoid cartilages and the cricoid is also a diarthrodial one,
and permits of two varieties of movement: one is a rotation of the arytenoid on a vertical axis,
whereby the vocal process is moved lateralward or medialward, and the rima glottidis increased
or diminished; the other is a gliding movement, and allows the arj'tenoid cartilages to approach
or recede from each other; from the direction and slope of the articular surfaces lateral gliding
is accompanied by a forward and downward movement. The two movements of gliding and
rotation are associated, the medial gliding being connected with medialward rotation, and the
lateral gliding with lateralward rotation. The posterior cricoarytenoid ligaments limit the
forward movement of the arytenoid cartilages on the cricoid.
Interior of the Larynx (Figs. 953, 954). — The cavity of the larynx {cavum
laryngis) extends from the laryngeal entrance to the lower border of the cricoid
cartilage where it is continuous with that of the trachea. It is divided into two
parts by the projection of the vocal folds, between which is a narrow triangular
fissure or chink, the rima glottidis. The portion of the cavity of the larynx above
the vocal folds is called the vestibule ; it is wide and triangular in shape, its base
or anterior wall presenting, however, about its center the backward projection
of the tubercle of the epiglottis. It contains the ventricular folds, and between
these and the vocal folds are the ventricles of the larynx. The portion below the
THE LARYNX
1079
GlossocpfglollicirYQ
fold 4.
Aryppiglottic
^ ' fold
Ventricular
and vocal
folds bound-
ing ventricle
[rylenoid
cartilage
Arytcerwideus
m uscle
31, (Idle
cricothijroid
ligament
Fig. 953. — Sagittal section of the larynx and upper part of the
trachea.
vocal folds is at first of an elliptical
form, but lower down it widens out,
assumes a circular form, and is con-
tinuous with the tube of the trachea.
The entrance of the larynx (Fig.
955) is a triangular opening, wide
in front, narrow behind, and sloping
obliquely downward and backward.
It is bounded, in front, by the epi-
glottis; behind, by the apices of the
arytenoid cartilages, the corniculate
ca,rtilages, and the interarytenoid
notch; and on either side, by a fold
of mucous membrane, enclosing
ligamentous and muscular fibers,
stretched between the side of the
epiglottis and the apex of the aryte-
noid cartilage; this is the aryepi-
glottic fold, on the posterior part of
the margin of which the cuneiform
cartilage forms a more or less dis-
tinct whitish prominence, the cunei-
form tubercle.
The Ventricular Folds {plicce ventric-
ulares; superior or false vocal cords)
are two thick folds of mucous membrane, each enclosing a narrovv' band of fibrous
tissue, the ventricular ligament which is attached in front to the angle of the thyroid
cartilage immediately below the attach-
ment of the epiglottis, and behind to the
antero-lateral surface of the arytenoid
cartilage, a short distance above the vocal
process. The lower border of this ligament,
enclosed in mucous membrane, forms a
free crescentic margin, which constitutes
the upper boundary of the ventricle of the
larynx.
The Vocal Folds (plica' vocales; inferior
or true vocal cords) are concerned in the
production of sound, and enclose two
strong bands, named the vocal ligaments
{ligamenta vocales; inferior thyroarytenoid).
Each ligament consists of a band of yellow
elastic tissue, attached in front to the
angle of the thyroid cartilage, and behind
to the vocal process of the arytenoid. Its
lower border is continuous with the thin
lateral part of the conus elasticus. Its
upper border forms the lower boundary
of the ventricle of the larynx. Laterally,
the Vocalis muscle lies parallel with it.
It is covered medially by mucous mem-
brane, which is extremelv thin and closely
9.54.-Corona! section^of^^arynx and upper part adherent tO itS SUrfaCC. ^
Hyoid bone-^
Otftline of
appendix of-
ventricle
Ventricular
fold
Ventricle
Vocal fold
ThyroaryiOB- _
noideus musde'
Fig.
1080
SPLANCHNOLOGY
The Ventricle of the Larynx {ventriculus laryngis [Morgagnii]; laryngeal sirius)
is a fusiform fossa, situated between the ventricular and vocal folds on either side,
and extending nearly their entire length. The fossa is bounded, above, by the free
crescentic edge of the ventricular fold; below, by the straight margin of the vocal
fold; laterally, by the mucous membrane covering the corresponding Thyreoary-
tsenoideus. The anterior part of the ventricle leads up by a narrow opening
into a cecal pouch of mucous membrane of variable size called the appendix.
The appendix of the laryngeal ventricle {appendix ventriculi laryngis; laryngeal
saccule) is a membranous sac, placed between the ventricular fold and the inner
surface of the thyroid cartilage, occasionally extending as far as its upper border
or even higher; it is conical in form, and curved slightly backward. On the surface
of its mucous membrane are the openings of sixty or seventy mucous glands, which
Svlcus terminalis
ev'-'fe,'
li.
•n^* < < t"l
Median glosso-
epiglottic fold
Greater cornu of
hyoid hone
Sup. cornu of fim
thyroid carl. l-liit (
Ventricular fold
Ventricle
Vocal fold ^ ^^*
Pyriform sinits
■ Foramen cecum
■ Vallecula
Lateral glosso-
e'pi glottic fold
TvhercU
Aryepiglottic fold
Glottis
Cuneiform cartilage
Corniculate cartilage
Fig. 055. — The entrance to the larynx, viewed from behind.
are lodged in the submucous areolar tissue. This sac is enclosed in' a fibrous
capsule, continuous below with the ventricular ligament. Its medial surface is
covered by a few delicate muscular fasciculi, which arise from the apex of the
arytenoid cartilage and become lost in the aryepiglottic fold of mucous membrane;
laterally it is separated from the thyroid cartilage by the Thyreoepiglotticus.
These muscles compress the sac, and express the secretion it contains upon the
vocal folds to lubricate their surfaces.
The Rima Glottidis (Fig. 956) is the elongated fissure or chink between the
vocal folds in front, and the bases and vocal processes of the arytenoid cartilages
behind. It is therefore subdivided into a larger anterior intramembranous
part {glottis vocalis), which measures about three-fifths of the length of the
entire aperture, and a posterior intercartilaginous part {glottis respirator ia).
THE LARYNX
1081
Posteriorly it is limited by the mucous membrane passing between the arytenoid
cartilages. The rima glottidis is the narrowest part of the cavity of the larynx,
and its level corresponds with the bases of the arytenoid cartilages. Its length,
in the male, is about 23 mm.; in the female from 17 to 18 mm. The width
and shape of the rima glottidis vary with the movements of the vocal folds
and arytenoid cartilages during respiration and phonation. In the condition
of rest, i. e., when these structures are uninfluenced by muscular action, as in
quiet respiration, the intramcmbranous part is triangular, with its apex in front
and its base behind — the latter being represented by a line, about 8 mm. long,
connecting the anterior ends of the vocal processes, while the medial surfaces of
the arytenoids are parallel to each other, and hence the intercartilaginous part
is rectangular. During extreme adduction of the vocal folds, as in the emission
of a high note, the intramembranous part is reduced to a linear slit by the ap-
position of the vocal folds, while the intercartilaginous part is triangular, its apex
corresponding to the anterior ends of the vocal processes of the arytenoids, which
are approximated by the medial rotation of the cartilages. Conversely in extreme
abduction of the vocal folds, as in forced inspiration, the arj^tenoids and their
Vallecula
Median glosso-epiglottic fold
Epiglottis
/Tubercle of epigloVix
Vocal fold
■ Veyitriciilar fold
Aryepiglottic fola
Cuneiform cartilage
Cunnoulate cartilage
Trachea
Fig. 95(i. — -Laryngoscopic view of interior of larynx,
vocal processes are rotated lateralward, and the intercartilaginous part is trian-
gular in shape but with its apex directed backward. In this condition the entire
glottis is somewhat lozenge-shaped, the sides of the intramembranous part
diverging from before backward, those of the intercartilaginous part diverging
from behind forward — the widest part of the aperture corresponding with the
attachments of the vocal folds to the vocal processes.
Muscles. — The muscles of the larynx are extrinsic, passing between the larynx
and parts around — these have been described in the section on Myology; and
intrinsic, confined entirely to the larynx.
The intrinsic muscles are:
Cricothyreoideus. Cricoaryta>noideus lateralis.
Cricoaryttenoideus posterior. Aryta?noideus.
Thyroarytpenoideus.
The Cricothyreoideus (Cricothyroid) (Fig. 957), triangular in form, arises from the
front and lateral part of the cricoid cartilage; its fibers diverge, and are arranged
in two groups. The lower fibers constitute a pars obliqua and slant backward
and lateralward to the anterior border of the inferior cornu; the anterior fibers,
forming a pars recta, run upward, backward, and lateralward to the posterior part
of the lower border of the lamina of the thyroid cartilage.
1082
SPLANCHNOLOGY
The medial borders of the two muscles are separated by a triangular interval,
occupied by the middle cricothyroid ligament.
The Cricoarytaenoideus posterior {posterior
cricoarytenoid) (Fig. 958) arises from the broad
depression on the corresponding half of the pos-
terior surface of the lamina of the cricoid cartil-
age; its fibers run upward and lateralward,
and converge to be inserted into the back of
the muscular process of the arytenoid cartil-
age. The uppermost fibers are nearly hori
zontal, the middle oblique, and the lowest
almost vertical.
The Cricoarytaenoideus lateralis {lateral
cricoarytenoid) (Fig. 959) is smaller than the
preceding, and of an oblong form. It arises
from the upper border of the arch of the
cricoid cartilage, and, passing obliquely up-
ward and backward, is inserted into the front
of the muscular process of the arytenoid cartil-
age.
The Arytsenoideus (Fig. 958) is a single muscle,
filling up the posterior concave surfaces of the
arytenoid cartilages. It arises from the pos-
terior surface and lateral border of one ary-
FiG. ^^^■-^^^i;^^'^^^fJXmenl^''' '^°''''°° tcuoid Cartilage, and is inserted into the corre-
Tubercle of
epiglottis
ti Cuneiform,
* cartilage
Corniculate
cartilage
yta:-
ideus
Corniculate
cartilages
Crycoarytce-
noideus
posterior
Articular facet for
inferior corn u of
thyroid cartilage
Fig. '958. — Muscles of larynx. Posterior view.
Fig. 959. — Muscles of larynx. Side view. Right lamina
of thjroid cartilage removed.
sponding parts of the opposite cartilage. It consists of oblique and transverse parts.
The Arytsenoideus obUquus, the more superficial, forms two fasciculi, which pass
THE LARYNX
1083
Fig. 960. — Muscles of the larynx, seen from above.
(Enlarged.)
from the base of one cartilage to the apex of the opposite one, and tlierefore
cross each other like the limbs of the letter X; a few fibers are continued around
the lateral margin of the cartilage, and
are prolonged into the aryepiglottic fold ;
they are sometimes describcfl as a sepa-
rate muscle, the Aryepiglotticus. The
Arytaenoideus transversus crosses trans-
versely between the two cartilages.
The Thyreoarytaenoideus {Thyroary-
tenoid) (Figs. 959, 9()0) is a broad, thin,
muscle which lies parallel with and lateral
to the vocal fold, and supports the Avail of
the ventricle and its appendix. It arises
in front from the lower half of the angle
of the thyroid cartilage, and from the
middle cricothyroid ligament. Its fibers
pass backward and lateralward, to be in-
serted into the base and anterior surface
of the arytenoid cartilage. The lower and
deeper fibers of the muscle can be differ-
entiated as a triangular band which is
inserted into the vocal process of the
arytenoid cartilage, and into the adjacent
portion of its anterior surface; it is
termed the Vocahs, and lies parallel with the vocal ligament, to which it is ad-
herent.
A considerable number of the fibers of the Thyreoaryttenoideus are prolonged
into the aryepiglottic fold, where some of them become lost, while others are con-
tinued to the margin of the epiglottis. They have received a distinctive name,
Thyreoepiglotticus, and are sometimes described as a separate muscle. A few fibers
extend along the wall of the ventricle from the lateral wall of the arytenoid cartilage
to the side of the epiglottis, and constitute the Ventricularis muscle.
Actions. — In considering the actions of the muscles of the larynx, they may be conveniently
divided into two groups, vix. : 1 . Those which open and close the glottis. 2. Those which regu-
late the degree of tension of the vocal folds.
The Cricoarytwnoidei posteriores separate the vocal folds, and, consequently, open the glottis,
by rotating the arytenoid cartilages outward around a vertical axis passing through the crico-
arytenoid joints; so that their vocal processes and the vocal folds attached to them become
widely separated.
The CricoaryUvnoidei laterales close the glottis by rotating the arytenoid cartilages mwar !,
so as to approximate their vocal processes.
The Arytmnoideus approximates the arytenoid cartilages, and thus closes the opening of
the glottis, especially at its back part.
The CricothAjreoidei produce tension and elongation of the vocal folds by drawing up the arch
of the cricoid cartilage and tilting back the upper border of its lamina; the distance between the
vocal processes and the angle of the thyroid is thus increased, and the folds are consequently
elongated.
The Thyreoarytamoidei, consisting of two parts having different attachments and different
directions, are rather compUcated as regards their action. Their main use is to draw the aryte-
noid cartilages forward toward the thyroid, and thus shorten and relax the vocal folds. But,
owing to the connection of the deeper portion with the vocal fold, this part, if acting separately,
is" supposed to modify its elasticity and tension, while the lateral portion rotates the arytenoid
cartilage inward, and thus narrows the rima glottidis by bringing the two vocal folds together.
The manner in which the entrance of the larynx is closed during deglutition is referred to
on page 1140.
Mucous Membrane. — The mucous membrane of the larynx is continuous above with that
lining the mouth and pharynx, and is prolonged through the trachea and bronchi into the lungs.
It lines the posterior surface and the upper part of the anterior surface of the epiglottis, to which
1084 SPLANCHNOLOGY
it is closely adherent, and forms the aryepiglottic folds which bound the entrance of the larynx.
It lines the whole of the cavity of the larynx; forms, by its reduplication, the chief part of the
ventricular fold, and, from the ventricle, is continued into the ventricular appendix. It is then
reflected over the vocal ligament, where it is thin, and very intimately adherent; covers the
inner surface of the conus elasticus and cricoid cartilage; and is ultimately continuous ^\^th the
lining membrane of the trachea. The anterior surface and the upper half of the posterior surface
of the epiglottis, the upper part of the arj-epiglottic folds and the vocal folds are covered by
stratified squamous epithelium; all the rest of the laryngeal mucous membrane is covered by
columnar ciliated cells, but patches of stratified squamous epithelium are found in the mucous
membrane above the glottis.
Glands. — The mucous membrane of the larynx is furnished with numerous mucous secreting
glands, the orifices of which are found in nearly every part; they are very plentiful upon the
epiglottis, being lodged in little pits in its substance; they are also found in large numbers along
the margin of the aryepiglottic fold, in front of the arytenoid cartilages, where they are termed
the arytenoid glands. They exist also in large numbers in the ventricular appendages. None
are found on the free edges of the vocal folds.
Vessels and Nerves. — The chief arteries of the larynx are the laryngeal branches derived
from the superior and inferior thjToid. The veins accompany the arteries; those accompanying
the superior laryngeal artery join the superior thjToid vein which opens into the internal jugular
vein; while those accompanying the inferior laryngeal artery join the inferior thjToid vein
which opens into the innominate vein. The Ismaphatic vessels consist of two sets, superior
and inferior. The former accompany the superior laryngeal artery and pierce the hyothjToid
membrane, to end in the glands situated near the bifurcation of the common carotid artery. Of
the latter, some pass through the middle cricothyroid ligament and open into a gland lying in
front of that ligament or in front of the upper part of the trachea, while others pass to the deep
cervical glands and to the glands accompanying the inferior thjToid artery. The nerves are
derived from the internal and external branches of the superior laryngeal nerve, from the
recurrent nerve, and from the sympathetic. The internal laryngeal branch is almost entirely
sensory, but some motor filaments are said to be carried by it to the Arj'ta^noideus. It enters
the larynx by piercing the posterior part of the hj'othyroid membrane above the superior
laryngeal vessels, and divides into a branch which is distributed to both surfaces of the epi-
glottis, a second to the aryepiglottic fold, and a third, the largest, which suppHes the mucous
membrane over the back of the larynx and communicates with the recurrent nerve. The external
laryngeal branch supplies the Cricothyreoideus. The recurrent nerve passes upward beneath
the lower border of the Constrictor pharyngis inferior immediately behind the cricoth>Toid joint.
It supphes aU the muscles of the larynx except the Cricothjreoideus, and perhaps a part of the
Aryta'iioideus. The sensory branches of the laryngeal nerves form subepithelial plexuses, from
which fibers pass to end between the cells covering the mucous membrane.
Over the posterior surface of the epiglottis, in the arj'-epiglottic folds, and less regularly in
some other parts, taste-buds, similar to those in the tongue, are found.
THE TRACHEA AND BRONCHI (Fig. 961).
The trachea or windpipe is a cartilaginous and membranous tube, extending
from the lower part of the larynx, on a level with the sixth cervical vertebra, to the
upper border of the fifth thoracic vertebra, where it divides into the two bronchi,
one for each lung. The trachea is nearly but not quite cylindrical, being flattened
po.steriorly; it measures about 11 cm. in length; its diameter, from side to side,
is from 2 to 2.5 cm., being always greater in the male than in the female. In
the child the trachea 's smaller, more deeply placed, and more movable than
in the adult.
Relations. — The anterior surface of the trachea is convex, and covered, in the neck, from
above downward, by the isthmus of the thyroid gland, the inferior thyroid veins, the arteria
thyroidea ima (when that vessel exists), the Sternothyreoideus and Sternohyoideus muscles,
the cervical fascia, and, more superficially, by the anastomosing branches between the anterior
jugular veins; in the thorax, it is covered from before backward by the manubrium sterni, '
the remains of the thjTnus, the left innominate vein, the aortic arch, the innominate and left
common carotid arteries, and the deep cardiac plexus. Posteriorly it is in contact with the
esophagus. Laterally, in the neck, it is in relation with the common carotid arteries, the right
and left lobes of the thjToid gland, the inferior thj'roid arteries, and the recurrent nerves; in
the thorax, it hes in the superior mediastinum, and is in relation on the right side with the
pleura and right vagus, and near the root of the neck with the innominate artery; on its left side
are the left recurrent nerve, the aortic arch, and the left common carotid and subclavian arteries.
THE TRACHEA AND BRONCHI
1085
The Right Bronchus {hronchus dexter), wider, shorter, and more vertical in direc-
tion than the left, is about 2.5 cm. long, and enters the right lung nearly- opposite
the fifth thoracic vertebra. The azygos vein arches over it from behind; and the
right pulmonary artery lies at first below and then in front of it. About 2 cm.
from its commencement it gives off a branch to the upper lobe of the right lung.
This is termed the eparterial branch of the bronchus, because it arises above the right
pulmonary artery. The bronchus now passes below the artery, and is known as the
hyparterial branch; it divides into two branches for the middle and lower lobes.
Superior
Cornu.
Fia. 961. — Front view of cartilages of larynx, trachea, and bronciii.
The Left Bronchus (bronchus sinister) is smaller in caliber but longer than the
right, being nearly 5 cm. long. It enters the root of the left lung opposite the sixth
thoracic vertebra. It passes beneath the aortic arch, crosses in front of the esoph-
agus, the thoracic duct, and the descending aorta, and has the left pulmonary
artery lying at first above, and then in front of it. The left bronchus has no
eparterial branch, and therefore it has been supposed by some that there is no
upper lobe to the left lung, but that the so-called upper lobe corresponds to the
middle lobe of the right lung.
\
\
\
1086
SPLANCHNOLOGY
The further subdivisions of the bronchi will be considered with the anatomy of
the lung.
If a transverse section be made across the trachea a short distance above its
point of bifurcation, and a bird's-eye view taken of its interior (Fig. 963), the septum
Fig 962 — Bronchi and bronchioles. The lungs have been widely separated and tissue cut away to expose the air-tubes.
(Testut.)
placed at the bottom of the trachea and separating the two bronchi will be seen
to occupy the left of the median line, and the right bronchus appears to be a more
direct continuation of the trachea than the left, so that any solid body dropping
into the trachea would naturally be directed toward the right bronchus. This
tendency is aided by the larger diameter
of the right tube as compared with its
fellow. This fact serves to explain Avhy
a foreign body in the trachea more fre-
quently falls into the right ]>ronchus.^
Structure (Fig. 954) — The trachea and extra-
puhnonary bronchi are composed of imperfect
rings of hyaline cartilage, fibrous tissue, mus-
cular fibers, mucous membrane, and glands.
The cartilages of the trachea vary from sixteen
to twenty in number: each forms an imperfect
ring, which occupies the anterior two-thirds or
so of the circumference of the trachea, being
deficient behind, where the tube is completed by fibrous tissue and unstriped muscular fibers.
The cartilages are placed horizontally above each other, separated by narrow intervals. They
measure about 4 mm. in depth and 1 mm. in thickness. Their outer surfaces are flattened in
a vertical direction, but the internal are convex, the cartilages being thicker in the mid Ue than
FiQ. 963. — Transverse section of the trachea, just
above its bifurcation, with a bird's-eye view of the
interior.
' Reigel asserts that the entry of a foreign body into the If/t bronchus is by no means so infrequent as is generally
supposed. See also Med.-Clii. Trans., Ixxi, 121.
THE PLEVRM
108";
Stratified
ciliated
epithelium
Longititdinat
elastic fibers
glands
:.-;<?\
fc •■■■■ -.;.:' ^''!^^!:'-%iK
at the margins. Two or more of the cartilages often unite, partially or completely, and they
are sometimes bifurcated at their extremities. They are highly elastic, but may become calcified
in advanced hfe. In the right bronchus the cartilages vary in number from six to eight; in the
left, from nme to twelve. They are shorter and narrower than those of the trachea, but have
the same shape and arrangement. The peculiar tracheal cartilages are the first and the last
(Fig. 961).
The ./(>s< cartilaqe is broader than the rest, and often divided at one end; it is connected by
the cricotracheal ligament with the lower border of the cricoid cartilage, with which, or with
the succeeding cartilage, it is sometimes blended.
The last cartilage is thick and broad in the middle, in consequence of its lower border being
prolonged into a triangular hook-shaped process, which curves downward and backward between
the two bronchi. It ends on each side in
an imperfect ring, which encloses the com-
mencement of the bronchus. The cartilage
above the last is somewhat broader than
the others at its center.
The Fibrous Membrane. — The cartilages
are enclosed in an elastic fibrous mem-
brane, which consists of two layers; one,
the thicker, passing over the outer surface
of the ring, the other over the inner sur-
face: at the upper and lower margins of
the cartilages the two layers blend together
to form a single membrane, which connects
the rings one with another. They are thus
invested by the membrane. In the space
behind, between the ends of the rings, the
membrane forms a single layer.
The muscular tissue consists of two
layers of non-striated muscle, longitudinal
and transverse. The longitudinal fibers
are external, and consist of a few scattered
bundles. The transverse fibers (Tracheahs
muscle) are internal, and form a thin layer
which extends transversely between the
ends of the cartilages.
Mucous Membrane. — The mucous mem-
brane is continuous above with that of the
larynx, and below with that of the bron-
chi. It consists of areolar and lymphoid
tissue, and presents a well-marked base-
ment membrane, supporting a stratified
epithelium, the surface layer of which is
columnar and ciliated, while the deeper
layers are composed of oval or rounded
cells. Beneath the basement membrane
there is a distinct layer of longitudinal
elastic fibers with a small amount of intervening areolar tissue. The submucous layer is com-
posed of a loose mesh-work of connective tissue, containing large bloodvessels, nerves, and
mucous glands; the ducts of the latter pierce the overlying layers and open on the surface
(Fig. 9;-l).
Vessels and Nerves. — The trachea is supplied with blood by the inferior thyroid arteries.
The veins end in the th\Toid venous plexus. The nerves are derived from the vagus and the
recurrent nerves, and from the sympathetic; they are distributed to the Trachealis muscles and
between the epithelial cells.
THE PLEUR.ffi.
Each lung is invested by an exceedingly delicate serous membrane, the pleura,
which is arranged in the form of a closed invaginated sac. A portion of the serous
membrane covers the surface of the lung and dips into the fissures between its
lobes; it is called the pulmonary pleura. The rest of the membrane lines the inner
surface of the chest wall, covers the diaphragm, and is reflected over the structures
occupying the middle of the thorax; this portion is termed the parietal pleura. The
two layers are continuous with one another around and below the root of the lung;
Fibrous
membrane
Hyaline
cartilage
Fibrous
membrane
FiQ. 964. — Transverse section of trachea.
1088
SPLANCHNOLOGY
in health they are in actual contact with one another, but the potential space
between them is known as the pleural cavity. When the lung collapses or when
air or fluid collects between the two layers the cavity becomes apparent. The right
and left pleural sacs are entirely separate from one another; between them are all
the thoracic viscera except the lungs, and they only touch each other for a short
distance in front; opposite the second and third pieces of the sternum the interval
between the two sacs is termed the mediastinum.
Different portions of the parietal pleura have received special names which
indicate their position: thus, that portion which lines the inner surfaces of the
ribs and Intercostales is the costal pleura; that clothing the convex surface of the
diaphragm is the diaphragmatic pleura; that which rises into the neck, over the
summit of the lung, is the cupula of the pleura (cervical j)leura) ; and that which is
applied to the other thoracic viscera is the mediastinal pleura.
Lower margin of pleura
Fig. 965. — Front view of thorax, showing the relations of the pleurae and lungs to the chest wall.
Pleura in blue; lungs in purple.
Reflections of the Pleura (Figs. 9G5, 966). — Commencing at the sternum, the
pleura passes lateralward, lines the inner surfaces of the costal cartilages, ribs,
and Intercostales, and at the back part of the thorax passes over the sympathetic
trunk and its branches, and is reflected upon the sides of the bodies of the verte-
brae, where it is separated by a narrow interval, the posterior mediastinum, from
the opposite pleura. From the vertebral column the pleura passes to the side of the
pericardium, which it covers to a slight extent; it then covers the back part of the
root of the lung, from the lower border of which a triangular sheet descends verti-
cally toward the diaphragm. This sheet is the posterior layer of a wide fold,
known as the pulmonary ligament. From the back of the lung root, the pleura
THE PLEURA
1089
subclavian art.
?. innominate vein
may be traced over the costal surface of the king, the apex and base, and also over
the sides of the fissures between the lobes, on to its mediastinal surface and the front
part of its root. It is continued from the lower margin of the root as the anterior
layer of the pulmonary ligament, and from this it is reflected on to the pericardium
(pericardial pleura), and from it to the back of the sternum. Above the level of
the root of tiie lung, however, the mediastinal pleura passes uninterruptedly from
the vertebral column to the sternum over the structures in the superior medias-
tinum. Below, it covers the upper surface of the diaphragm and extends, in
front, as low as the costal cartilage of the seventh rib; at the side of the chest,
to the lower border of the tenth rib on the left side and to the upper border of the
same rib on the right side; and behind, it reaches as low as the twelfth rib, and some-
times even to the transverse process
of the first lumbar vertebra. Above, ,-^-v~_-, Trachea
its cupula projects through the
superior opening of the thorax into
the neck, extending from 2.5 to 5
cm. above the sternal end of the
first rib; this portion of the sac is
strengthened by a dome-like expan-
sion of fascia (Sibson's fascia), at-
tached in front to the inner border
of the first rib, and behind to the
anterior border of the transverse
process of the seventh cervical
vertebra. This is covered and
strengthened b}' a few spreading
muscular fibers derived from the
Scaleni.
In the front of the chest, where
the parietal pleura is reflected back-
ward to the pericardium, the two
pleural sacs are in contact for a
short distance. At the upper part
of the chest, behind the manubrium,
they are separated by an angular
interval; the line of reflection being
represented by a line drawn from
the sternoclavicular articulation to
the mid-point of the junction of
the manubrium with the bodv of the
sternum. From this point the two
pleurae descend in close contact to
the level of the fourth costal cartilages, and the line of reflection on the right side
is continued downward in nearly a straight line to the xiphoid process, and then
turns lateralward, while on the left side the line of reflection diverges lateralward
and is continued downward, close to the left border of the sternum, as far as the
sixth costal cartilage. The inferior limit of the pleura is on a considerably lower
level than the corresponding limit of the lung, but does not extend to the attach-
ment of the diaphragm, so that below the line of reflection of the pleura from the
chest wall on to the diaphragm the latter is in direct contact with the rib cartilages
and the Intercostales interni. ]\Ioreover, in ordinary inspiration the thin inferior
margin of the lung does not extend as low as the line of the pleural reflection, with
the result that the costal and diaphragmatic pleurae are here in contact, the inter-
vening narrow slit being termed the phrenicocostal sinus. A similar condition
69
Lower margin
of -pleura
Lower margin cf lung
Fig. 9GG. — Lateral view of thorax, showing the relations of
the pleurae and lungs to the chiest wall. Pleura in blue; lungs in
purple.
1090 SPLANCHNOLOGY
exists behind the sternum and rib cartilages, where the anterior thin margin of
the lung falls short of the line of pleural reflection, and where the slit-like cavity
between the two layers of pleura forms what is called the costomediastinal sinus.
The line along which the right pleura is reflected from the chest-wall to the
diaphragm starts in front, immediately below the seventh sternocostal joint, and
runs downward and backward behind the seventh costal cartilage so as to cross
the tenth rib in the mid-axillary line, from which it is prolonged to the spinous
process of the twelfth thoracic vertebra. The reflection of the left pleura follows
at first the ascending part of the sixth costal cartilage, and in the rest of its course
is slightly lower than that of the right side.
The free surface of the pleura is smooth, polished, and moistened by a serous
fluid; its attached surface is intimately adherent to the lung, and to the pulmonary
vessels as they emerge from the pericardium; it is also adherent to the upper sur-
face of the diaphragm : throughout the rest of its extent it is easily separable from
the adjacent parts.
The right pleural sac is shorter, wider, and reaches higher in the neck than the
left.
Pulmonary Ligament {ligamenhim pulmonale; liganientum latum pulmonis). —
From the above description it will be seen that the root of the lung is covered in
front, above, and behind by pleura, and that at its lower border the investing
layers come into contact. Here they form a sort of mesenteric fold, the pulmonary
ligament, which extends between the lower part of the mediastinal surface of the
lung and the pericardium. Just above the diaphragm the ligament ends in a free
falciform border. It serves to retain the lower part of the lung in position.
Structure of Pleura. — Like other serous membranes, the pleura is covered by a single layer
of flattened, nucleated cells, united at their edges by cement substance. These cells are modified
connective-tissue corpuscles, and rest on a basement membrane. Beneath the basement mem-
brane there are net-works of yellow elastic and white fibers, imbedded in ground substance which
also contains connective-tissue cells. Bloodvessels, lymphatics, and nerves are distributed in
the substance of the pleura.
Vessels and Nerves. — The arteries of the pleura are derived from the intercostal, internal
mammary, musculophrenic, thymic, pericardiac, and bronchial vessels. The veins correspond
to the arteries. The lymphatics are described on page 719. The nerves are derived from the
phrenic and sympathetic (Luschka). KoUiker states that nerves accompany the ramifications
of the bronchial arteries in the pulmonary pleura.
THE MEDIASTINUM (INTERPLEURAL SPACE).
The mediastinum lies between the right and left pleurae in and near the median
sagittal plane of the chest. It extends from the sternum in front to the vertebral
column behind, and contains all the thoracic viscera excepting the lungs. It may
be divided for purposes of description into two parts: an upper portion, above the
upper level of the pericardium, which is named the superior mediastinum; and a
lower portion, below the upper level of the pericardium. This lower portion is
again subdivided into three parts, viz., that in front of the pericardium, the
anterior mediastimun; that containing the pericardium and its contents, the middle
mediastinum; and that behind the pericardium, the posterior mediastinum.
The Superior Mediastinum (Fig. 907) is that portion of the interpleural space
which lies between the manubrium sterni in front, and the upper thoracic verte-
brae behind. It is bounded below by a slightly oblique plane passing backward
from the junction of the manubrium and body of the sternum to the lower part
of the body of the fourth thoracic vertebra, and laterally by the pleurae. It con-
tains the origins of the Sternohyoidei and Sternothyreoidei and the lower ends of
the Longi colli;- the aortic arch; the innominate artery and the thoracic portions
of the left common carotid and the left subclavian arteries; the innominate veins
THE MEDIASTINUM
1091
and the upper half of the superior vena cava; the left highest intercostal vein; the
vagus, cardiac, phrenic, and left recurrent nerves; the trachea, esophagus, and
thoracic duct; the remains of the thymus, and some lymph glands.
Lt. carotid
Left innominate vein art. Thymus Vagus nerve
Vagus nerve
Vertebra^
art.
Lt. subcla-
vian art.
Eso-
phagus
^ Int. mammary
artery
Ht. inno-
ninate v.
Trachea
Second
rib
Third rib
Fig. 967. — Transverse section through the upper margin of the second thoracic vertebra. (Braune.)
Transvergris thoracis
Internal mammary resgehX
Left phrenic
nerve
Pulmonary pleura
Costal pleura
Sympathetic trunk
Thoracic duct
Azygos vein
Vagus nerves
Fig. 968. — A transverse section of the thorax, showing the contents of the middle and the posterior mediastinum.
The pleural and pericardial cavities are exaggerated since normally there is no space between parietal and visceral pleura
and between pericardium and heart. . . ■ ; ji
1092
SPLANCHNOLOGY
The Anterior Mediastinum (Fig. 968) exists only on the left side where the
left pleura diverges from the mid-sternal line. It is bounded in front by the
sternum, laterally by the pleurae, and behind by the pericardium. It is narrow,
above, but widens out a little below. Its anterior wall is formed by the left Trans-
versus thoracis and the fifth, sixth, and seventh left costal cartilages. It contains
a quantity of loose areolar tissue, some lymphatic vessels which ascend from the
convex surface of the liver, two or three anterior mediastinal lymph glands, and
the small mediastinal branches of the internal mammary artery.
Highest intercostal artery
Highest intercostal vein
Rami convmunicantes
Lig. artenosum
Fig. 969. — The middle and posterior mediastina. Left side.
The Middle Mediastinum (Fig. 908) is the broadest part of the interpleural
space. It contains the heart enclosed in the pericardium, the ascending aorta,
the lower half of the superior vena cava with the azygos vein opening into it,
the bifurcation of the trachea and the two bronchi, the pulmonary artery dividing
THE LUNGS
1093
into its two branches, the right and left pulmonary veins, tlie phrenie nerves,
and some bronchial lymph ghmds.
The Posterior Mediastinum (Figs. 968, 969) is an irregular triangular space
running parallel with the vertebral column; it is bounded in front by the peri-
cardium above, and by the posterior surface of the diaphragm below, behind by
the vertebral column from the lower border of the fourth to the twelfth thoracic
vertebra, and on either side by the mediastinal pleura. It contains the thoracic
part of the descending aorta, the azygos and the two hemiazygos veins, the vagus
and splanchnic nerves, the esophagus, the thoracic duct, and some lyinph glands.
THE LUNGS (PULMONES).
The lungs are the essential organs of respiration; they are two in number, placed
one on either side within the thorax, and separated from each other by the heart
and other contents of the mediastinum (Fig. 970). The substance of the lung is
of a light, porous, spongy texture; it floats in water, and crepitates when handled,
owing to the presence of air in the alveoli ; it is also highly elastic ; hence the retracted
state of these organs when they are removed from the closed cavity of the thorax.
The surface is smooth, shining, and marked out into numerous polyhedral areas,
indicating the lobules of the organ: each of these areas is crossed by numerous
lighter lines.
Cut edge of pericardium
Fig. 970. — Front view of heart and lungs.
At birth the lungs are pinkish white in color; in adult life the color is a dark
slaty gray, mottled in patches; and as age advances, this mottling assumes a black
color. The coloring matter consists of granules of a carbonaceous substance
deposited in the areolar tissue near the surface of the organ. It increases in quan-
1094
SPLANCHNOLOGY
tity as age advances, and is more abundant in males than in females. As a rule,
the posterior border of the lung is darker than the anterior.
The right lung usually weighs about 625 gm., the left 567 gm., but much varia-
tion is met with according to the amount of blood or serous fluid they may contain.
The lungs are heavier in the male than in the female, their proportion to the body
being, in the former, as 1 to 37, in the latter as 1 to 43.
Each lung is conical in shape, and presents for examination an apex, a base,
three borders, and two surfaces.
The apex {apex pu1mo)iis) is rounded, and extends into the root of the neck,
reaching from 2.5 to 4 cm. above the level of the sternal end of the first rib. A
sulcus produced by the subclavian artery as it curves in front of the pleura runs
upward and lateralward immediately below the apex.
The base (basis pulmonis) is broad, concave, and rests upon the convex surface
of the diaphragm, which separates the right lung from the right lobe of the liver,
and the left lung from the left lobe of the liver, the stomach, and the spleen. Since
the diaphragm extends higher on the right than on the left side, the concavity
on the base of the right lung is deeper than that on the left. Laterally and behind,
the base is bounded by a thin, sharp margin which projects for some distance
into the phrenicocostal sinus of the pleura, between the lower ribs and the costal
attachment of the diaphragm. The base of the lung descends during inspiration
and ascends during expiration.
entrance of
-vena azygos
branch of pu l-
"monary artery
Fig 971 — Pulmonary vessels, seen in a dorsal view of the heart and lungs. The lungs have been pulled awaj-
from the median line, and a part of the right lung has been cut awav to displaj- the air-ducts and bloodvessels.
(Testut.)
Surfaces. — The costal surface (fades costaiis; external or thoracic surjace) is
smooth, convex, of considerable extent, and corresponds to the form of the cavity
of the chest, being deeper behind than in front. It is in contact with the costal
pleura, and presents, in specimens which have been hardened in situ, slight grooves
corresponding with the overlying ribs.
THE LUNGS
1095
The mediastinal surface {fades inediastinalis; inner surface) is in contact with
the mediastinal pleura. It presents a deep concavity, the cardiac impression,
which accommodates the pericardium; this is laro;er and deeper on the left than
on the right lung, on account of the heart projecting farther to the left than to the
right side of the median plane. Above and behind tiiis concavity is a triangular
depression named the hilum, where the structures which form the root of the lung
enter and leave the viscus. These structures are invested by pleura, which, below
the hilus and behind the pericardial impression, forms the pulmonary ligament.
On the right lung (Fig. 972), immediately above the hilus, is an arched furrow
which accommodates the azygos vein; while running upward, and then arching
lateralward some little distance below the apex, is a wide groove for the superior
vena cava and right innominate vein; behind this, and nearer the apex, is a furrow
Groove for
innominate artery
Groove for
sup. vena cav^.
Puhrumary
artery
Groove for azygos
vein
Eparterial
bronchus
Ilyparterial
bronchus
- Puhnonary
veins
^Groove for
esophagus
Pulmonary
liyunient
Fig. 972. — Mediastinal surface of right lung.
for the innominate artery. Behind the hilus and the attachment of the pulmonary
ligament is a vertical groove for the esophagus; this groove becomes less distinct
below, owing to the inclination of the lower part of the esophagus to the left of
the middle line. In front and to the right of the lower part of the esophageal
groove is a deep concavity for the extrapericardiac portion of the thoracic part
of the inferior vena cava. On the left lung (Fig. 973), immediately above the hilus,
is a well-marked curved furrow produced by the aortic arch, and running upward
from this toward the apex is a groove accommodating the left subclavian artery;
a slight impression in front of the latter and close to the margin of the lung lodges
the left innominate vein. Behind the hilus and pulmonary ligament is a vertical
furrow produced by the descending aorta, and in front of this, near the base of
the lung, the lower part of the esophagus causes a shallow impression.
1096
SPLANCHNOLOGY
Borders. — -The inferior border {margo inferior) is thin and sharp where it sepa-
rates the base from the costal surface and extends into the phrenicocostal sinus;
medially where it divides the base from the mediastinal surface it is blunt and
rounded.
The posterior border {margo 'posterior) is broad and rounded, and is received into
the deep concavity on either side of the vertebral column. It is much longer
than the anterior border, and projects, below, into the phrenicocostal sinus.
The anterior border (jnargo anterior) is thin and sharp, and overlaps the front
of the pericardium. The anterior border of the right lung is almost vertical, and
projects into the costomediastinal sinus; that of the left presents, below, an angular
notch, the cardiac notch, in which the pericardium is exposed. Opposite this
notch the anterior margin of the left lung is situated some little distance lateral
to the line of reflection of the corresponding part of the pleura.
Groove for left subclavian artery
Groove for left innominate vein
Bronchus
Posterior
border
Pulmonary I
ligament
Pulmonary
artery
Pulmonary
veins
Cardiac notch
Fig. 973. — Mediastinal surface of left lung.
Fissures and Lobes of the Lungs. — The left lung is divided into two lobes,
an upper and a lower, by an interlobular fissure, which extends from the costal
to the mediastinal surface of the lung both above and below the hilus. As seen
on the surface, this fissure begins on the mediastinal surface of the lung at the
upper and posterior part of the hilus, and runs backward and upward to the pos-
terior border, which it crosses at a point about 6 cm. below the apex. It then
extends downward and forward over the costal surface, and reaches the lower
border a little behind its anterior extremity, and its further course can be followed
upward and backward across the mediastinal surface as far as the lower part of
the hilus. The superior lobe lies above and in front of this fissure, and includes the
apex, the anterior border, and a considerable part of the costal surface and the
greater part of the mediastinal surface of the lung. The inferior lobe, the larger
THE LUNGS 1097
of the two, is situated below and behind the fissure, and comprises almost the
whole of the base, a large portion of the costal surface, and the greater part of
the posterior border.
The right lung is divided into three lobes, superior, middle, and inferior, by
two interlobular fissures. One of these separates the inferior from the middle
and superior lobes, and corresponds closely with the fissure in the left lung. Its
direction is, however, more vertical, and it cuts the lower border about 7.5 cm.
behind its anterior extremity. The other fissure separates the superior from the
middle lobe. It begins in the previous fissure near the posterior border of the lung,
and, running horizontally forward, cuts the anterior border on a level with the
sternal end of the fourth costal cartilage; on the mediastinal surface it may be
traced backward to the hilus. The middle lobe, the smallest lobe of the right
lung, is wedge-shaped, and includes the lower part of the anterior border and the
anterior part of the base of the lung.
The right lung, although shorter by 2.5 cm. than the left, in consequence of the
diaphragm rising higher on the right side to accommodate the liver, is broader,
owing to the inclination of the heart to the left side; its total capacity is greater
and it weighs more than the left lung.
The Root of the Lung {radix lyulmonis). — A little above the middle of the medias-
tinal surface of each lung, and nearer its posterior than its anterior border, is its
root, by which the lung is connected to the heart and the trachea. The root is
formed by the bronchus, the pulmonary artery, the pulmonary veins, the bronchial
arteries and veins, the pulmonary plexuses of nerves, lymphatic vessels, bronchial
lymph glands, and areolar tissue, all of which are enclosed by a reflection of the
pleura. The root of the right lung lies behind the superior vena cava and part
of the right atrium, and below the azygos vein. That of the left lung passes
beneath the aortic arch and in front of the descending aorta; the phrenic nerve,
the pericardiacophrenic artery and vein, and the anterior pulmonary plexus, lie
in front of each, and the vagus and posterior pulmonary plexus behind each;
below each is the pulmonary ligament.
The chief structures composing the root of each lung are arranged in a similar
manner from before backward on both sides, viz., the upper of the two pulmonary
veins in front; the pulmonary artery in the middle; and the bronchus, together
with the bronchial vessels, behind. From above downward, on the two sides,
their arrangement differs, thus:
On the right side their position is — eparterial bronchus, pulmonary artery,
hyparterial bronchus, pulmonary veins, but on the left side their position is —
pulmonary artery, bronchus, pulmonary veins. The lower of the two pulmonary
veins, is situated below the bronchus, at the apex or lowest part of the hilus
(Figs. 972, 973).
Divisions of the Bronchi. — Just as the lungs differ from each other in the number
of their lobes, so the bronchi differ in their mode of subdivision.
The right bronchus gives off, about 2.5 cm. from the bifurcation of the trachea,
a branch for the superior lobe. This branch arises above the level of the pulmonary
artery, and is therefore named the eparterial bronchus. All the other divisions
of the main stem come off below the pulmonary artery, and consequently are
termed hyparterial bronchi. The first of these is distributed to the middle lobe,
and the main tube then passes downward and backward into the inferior lobe,
giving off in its course a series of large ventral and small dorsal branches. The
ventral and dorsal branches arise alternately, and are usually eight in number —
four of each kind. The branch to the middle lobe is regarded as the first of the
ventral series.
The left bronchus passes below the level of the pulmonary artery before it divides,
and hence all its branches are hyparterial; it may therefore be looked upon as
1098
SPLANCHNOLOGY
equivalent to that portion of the right bronchus which lies on the distal side of its
eparterial branch. The first branch of the left bronchus arises about 5 cm. from
the bifurcation of the trachea, and is distributed to the superior lobe. The main
stem then enters the inferior lobe, where it divides into ventral and dorsal branches
similar to those in the right lung. The branch to the superior lobe of the left lung
is regarded as the first of the ventral seiies.
Structure. — The lungs are composed of an external serous coat, a subserous areolar tissue
and the pulmonary substance or parenchyma.
The serous coat is the pulmonary pleura (page 1090); it is thin, transparent, and invests the
entire organ as far as the root.
The subserous areolar tissue contains a large proportion of elastic fibers; it invests the entire
surface of the lung, and extends inward between the lobules.
The parenchyma is composed of secondary lobules which, although closely connected together
by an interlobular areolar tissue, are quite distinct from one another, and may be teased
asunder without much difficulty in the fetus. The secondary lobules vary in size; those on
the surface are large, of pyramidal form, the base turned toward the surface; those in the
interior smaller, and of various forms. Each secondary lobule is composed of several primary
lobules, the anatomical units of the lung. The primary lobule consists of an alveolar tluct,
the air spaces connected with it and their bloodvessels, Ivmphatics and nerves.
The intrapulmonary bronchi divide and subdivide throughout the entire organ, the smallest
subdivisions constituting the lobular bronchioles. The larger divisions consist of: (1) an outer
coat of fibrous tissue in which are fovmd at intervals irregular plates of hyaline cartilage, most
developed at the points of division; (2) internal to the fibrous coat, a laj'er of c'rcularly disposed
smooth muscle fibers, the bronchial muscle; and (3) most internally, the mucous membrane,
lined by columnar ciliated epithelium resting on a basement membrane. The corium of the
mucous membrane contains numerous elastic fibers running longitudinally, and a certain amount
of lymphoid tissue; it also contains the ducts of mucous glands, the acini of which lie in the
fibrous coat. The lobular bronchioles differ from the larger tubes in containing no cartilage
and in the fact that the ciliated epithehal cells are cubical in shape. The lobular bronchioles
are about 0.2 mm. in diameter.
Fig 974. — Part of a secondary lobule from the depth of a human lung, showing parts of several primary lobules.
1, bronchiole: 2, respiratory bronchiole; 3, alveolar duct; '4. atria; 5, alveolar sac; (i, alveolus or air cell; ?«, smooth
muscle; a. branch pulmonary artery; r, branch pulmonary vein; s, septum between secondary lobules. Camera
drawing of one 50 M section. X 20 diameters. (Miller.)
Each bronchiole divides into two or more respiratory bronchioles, with scattered alveoli, and
each of these again divides into several alveolar ducts, with a greater number of alveoli con-
nected with them. Each alveolar duct is connected with a variable number of irregularly
spherical spaces, which also ])ossess alveoli, the atria. With each atrium a variable number
(2-5) of alveolar sacs are coimected which bear on all parts of their circumferenca alveoli or air
sacs. (Miller.)
THE LUNGS
1099
The alveoli are lined by a delicate layer of simple squamous epithelium, the cells of which
are united at their edges by cement substance. Between the squames are here and there smaller,
Fig. 975. — Schematic longitudinal section of a primary lobule of the lung (anatomical unit); r. b.. respiratory
bronchiole, al. d.. alveolar duct, at., atria; a. s., alveolar sac, a. alveolus or air cell; p. a ijuliuonary ariery; p. r.,
pulmonary vein; I., lymphatic; I. n., lymph node. (Miller.)
polygonal, nucleated cells Outside the epithelial lining is a little delicate connective tissue
containing numerous elastic fibers and a close net-work of blood capillaries, and forming a common
wall to adjacent alveoli (Fig. 975).
Fia. 976. — Section of luns; of pig embryo, 1.3 cm. Ions, showing the glandular character of the developing alveoli
(J. M. Flint.) X 70. a. interstitial connective tissue, b. A bronchial tube. c. An Alveolus. I. lymphatic clefts.
q. Pleura.
The fetal lung resembles a gland in that the alveoli have a small lumen and are lined by
cubical epithelium (Fig. 976). After the first respiration the alveoli become distended, and the
epithelium takes on the characters described above.
1100 SPLANCHNOLOGY
Vessels and Nerves. — The pulmonary artery conveys the venous blood to the lungs; it divides
into branches which accompany the broncliial tubes and end in a dense capillary net-work in
the walls of the alveoli. In the lung the branches of the pulmonary artery are usualh' above
and in front of a bronchial tube, the vein below.
The pulmonary capillaries form plexuses which lie immediately beneath the lining epithe-
lium, in the walls and septa of the alveoli and of the infundibula. In the septa between the
alveoli the capillary net-work forms a single layer. The capillaries form a very minute net -work,
the meshes of which are smaller than the vessels themselves; their walls are also exceedingly
thin. The arteries of neighboring lobules are independent of each other, but the veins freely
anastomose.
The pulmonary veins commence in the pulmonary capillaries, the radicles coalescing into
larger branches which run through the substance of the lung, independently of the pulmonary
arteries and bronchi. After freely communicating with other branches they form large vessels,
which ultimately come into relation with the arteries and bronchial tubes, and accompany
them to the hilus of the organ. Finally they open into the left atrium of the heart, conveying
oxygenated blood to be distributed to all parts of the body by the aorta.
The bronchial arteries supply blood for the nutrition of the lung; they are derived from the
thoracic aorta or from the upper aortic intercostal arteries, and, accompanying the bronchial
tubes, are distributed to the bronchial glands and upon the walls of the larger bronchial tubes
and pulmonary vessels. Those supplying the bronchial tubes form a capillary plexus in the
muscular coat, from which branches are given off to form a second plexus in the mucous coat;
this plexus communicates with small venous trunks that empty into the pulmonary veins.
Others are distributed in the interlobular areolar tissue, and end partly in the deep, partly
in the superficial, bronchial veins. Lastly, some ramify upon the surface of the lung, beneath
the pleura, where they form a capillary network.
The bronchial vein is formed at the root of the lung, receiving superficial and deep veins corre-
sponding to branches of the bronchial artery. It does not, however, receive all the blood suppUed
by the artery, as some of it passes into the pulmonary veins. It ends on the right side in the
azygos vein, and on the left side in the highest intercostal or in the accessory hemiazygos vein.
The l3rmphatics are described on page 718.
Nerves. — The lungs are supplied from the anterior and posterior pulmonary plexuses, formed
chiefly by branches from the sj'mpathetic and vagus. The filaments from these plexuses accom-
pany the bronchial tubes, supplying efferent fibers to the bronchial muscle and afferent fibers
to the bronchial mucous membrane and probably to the alveoli of the lung. Small ganglia
are found upon these nerves.
THE DIGESTIVE APPARATUS (APPARATUS DIGESTORIUS; ORGANS
OF DIGESTION).
The apparatus for the digestion of the food consists of the digestive tube and of
certain accessory organs.
The Digestive Tube (alimentary canal) is a musculomembranous tube, about
9 metres long, extending from the mouth to the anus, and lined throughout its
entire extent by mucous membrane. It has received different names in the various
parts of its course: at its commencement is the mouth, where provision is made
for the mechanical division of the food {mastication), and for its admixture with
a fluid secreted by the salivary glands (insalivation) ; beyond this are the organs
of deglutition, the pharynx and the esophagus, which convey the food into the
stomach, in which it is stored for a time and in which also the first stages of the
digestive process take place; the stomach is followed by the small intestine, which
is divided for purposes of description into three parts, the duodenum, the jejunum,
and ileum. In the small intestine the process of digestion is completed and the
resulting products are absorbed into the blood and lacteal vessels. Finally the
small intestine ends in the large intestine, which is made up of cecum, colon, rectum,
and anal canal, the last terminating on the surface of the body at the anus.
The accessory organs are the teeth, for purposes of mastication; the three pairs
of salivary glands — the parotid, submaxillary, and sublingual — the secretion from
which mixes with the food in the mouth and converts it into a bolus and acts
chemically on one of its constituents; the liver and pancreas, two large glands
in the abdomen, the secretions of which, in addition to that of numerous minute
glands in the walls of the alimentary canal, assist in the process of digestion.
THE DIGESTIVE APPARATUS
1101
The Development of the Digestive Tube. — The primitive digestive tube con-
sists of two parts, viz.: (1) the fore-gut, within the cephalic flexure, and dorsal
to the heart; and (2) the hind-gut, within the caudal flexure (Fig. 977). Between
these is the wide opening of the yolk-sac, which is gradually narrowed and reduced
to a small foramen leading into the vitelline duct. At first the fore-gut and hind-
gut end blindly. The anterior end of the fore-gut is separated from the stomo-
deum by the buccopharyngeal membrane (Fig. 977); the hind-gut ends in the
cloaca, which is closed by the cloacal membrane.
Thalamencephalon
Optic vesicle
Mid-hrain
Buccopharyngeal
membrane
Pharynx
Auditoi-y pit
Bulbils cordis
Stomach
Stom^deum
Ventricle
- — Liver
Cloaca
Body-stalk
Umbilical vein
Yolk-sac
Hind-gut
Allantois
Umbilical artery
Fig. 977. — Human embryo about fifteen days old. Brain and heart represented from right side. Digestive tube and
yolk sac in median section. (After His.)
The Mouth. — The mouth is developed partly from the stomodeum, and partly
from the floor of the anterior portion of the fore-gut. By the growth of the head
end of the embryo, and the formation of the cephalic flexure, the pericardial area
and the buccopharyngeal membrane come to lie on the ventral surface of the
embryo. With the further expansion of the brain, and the forward bulging of the
pericardium, the buccopharyngeal membrane is depressed between these two
prominences. This depression constitutes the stomodeum (Fig. 977). It is lined
by ectoderm, and is separated from the anterior end of the fore-gut by the bucco-
pharyngeal membrane. This membrane is devoid of mesoderm, being formed
by the apposition of the stomodeal ectoderm with the fore-gut entoderm; at the
end of the third week it disappears, and thus a communication is established
between the mouth and the future pharynx. Xo trace of the membrane is found
in the adult; and the communication just mentioned must not be confused with the
permanent isthmus faucium. The lips, teeth, and gums are formed from the walls
of the stomodeum, but the tongue is developed in the floor of the pharynx.
The visceral arches extend in a ventral direction l)etween the stomodeum and
the pericardium; and with the completion of the mandibular arch and the formation
of the maxillary processes, the mouth assumes the appearance of a pentagonal
orifice. The orifice is bounded in front by the fronto-nasal process, behind by the
1102
SPLANCHNOLOGY
mandibular arch, and laterally by the maxillary processes (Fig. 978). With the
inward growth and fusion of the palatine processes (Figs. 50, 51), the stomodeum
is divided into an upper nasal, and a lower buccal part. Along the free margins
of the processes bounding the mouth cavity a shallow groove appears; this is
termed the primary labial groove, and from the bottom of it a downgrowth of
ectoderm takes place into the underlying mesoderm. The central cells of the
ectodermal downgrowth degenerate and a secondary labial groove is formed; by
the deepening of this, the lips and cheeks are separated from the alveolar processes
of the maxillae and mandible.
The Salivary Glands. — The salivary glands arise as buds from the epithelial
lining of the mouth; the parotid appears during the fourth week in the angle
between the maxillary process and the
mandibular arch; the submaxillary ap-
pears in the sixth week, and the sublin-
gual during the ninth week in the hollow
between the tongue and the mandibular
arch.
The Tongue (Figs. 979 to 981).— The
tongue is developed in the floor of the
pharynx, and consists of an anterior or
buccal and a posterior or pharyngeal part
which are separated in the adult by the
V-shaped sulcus terminalis. During the
third week there appears, immediately
behind the ventral ends of the two halves
of the mandibular arch, a rounded
swelling named the tuberculum impar,
which was described by His as un-
dergoing enlargement to form the
buccal part of the tongue. More re-
cent researches, however, show that
this part of the tongue is mainly, if
not entirely, developed from a pair
of lateral swellings Avhich rise . from
the inner surface of the mandibular arch and meet in the middle line. The tuber-
culum impar is said to form the central part of the tongue immediately in front
Future apex of nose
lllll^ il/ccZmZ nasal process
•i^ Olfactory pit
Lateral nasal process
Globular process
JIaxillary process
';r Stomodeum
Mandibular arch
Fig. 978. — Head end of human embryo of about thirty
to thirty-one days. (From mode! by Peters.)
Lateral tongue Thyroid
swellings diverticulum
Lateral tongue swellings
Entrance to
laryna;
Fig. 979. — Floor of pharynx of human embryo
about twenty-six days old. (From model by
Peters.)
Entrance to
larynx
Arytenoid
swellings
Fig. 980. — Floor of pharynx of human embryo
of about the end of the fourth week. (From
model by Peters.)
of the foramen cecum, but Hammar insists that it is purely a transitory structure
and forms no part of the adult tongue. From the ventral ends of the fourth arch
THE DIGESTIVE APPARATUS
1103
Arytenoid
dwellings
FiQ. 981. — Floor of pharynx of human embryo about thirty
days old. (From model by Peter.)
there arises a second and larger elevation, in the center of which is a median groove
or furrow. This elevation was named by His the furcula, and is at first separated
from the tuberculum impar by a depression, but later by a ridge, the copula,
formed by the forward growth and fusion of the ventral ends of the second and
third arches. The posterior or pharyngeal part of the tongue is developed from
the copula, which extends forward in the form of a V, so as to embrace between its
two limbs the buccal part of the tongue. At the apex of the V a pit-like invagination
occurs, to form the thyroid gland,
and this depression is represented in
the adult by the foramen cecum of
the tongue. In the adult the union
of the anterior and posterior parts
of the tongue is marked by the V-
shaped sulcus terminalis, the apex of
which is at the foramen cecum, while
the two limbs run lateralward and
forward, parallel to, but a little be-
hind, the vallate papilhe.
The Palatine Tonsils. — The palatine
tonsils are developed from the dorsal
angles of the secondbranchialpouches.
The entoderm which lines these pouches grows in the form of a number of solid
buds into the surrounding mesoderm. These buds become hollowed out by the
degeneration and casting off of their central cells, and by this means the tonsillar
crypts are formed. Lymphoid cells accumulate around the crypts, and become
grouped to form the lymphoid follicles; the latter, however, are not well-defined
until after birth.
The Fiirther Development of the Digestive Tube. — The upper part of the fore-gut
becomes dilated to form the pharynx (Fig. 977), in relation to which the branchial
arches are developed (see page 65) ; the succeeding part remains tubular, and with
the descent of the stomach is elongated to form the esophagus. About the fourth
week a fusiform dilatation, the future stomach, makes its appearance, and beyond
this the gut opens freely into the yolk-sac (Fig. 982, A and B). The opening is at
first wide, but is gradually narrowed into a tubular stalk, the yolk-stalk or vitelline
duct. Between the stomach and the mouth of the yolk-sac the liver diverticulum
appears. From the stomach to the rectum the alimentary canal is attached to the
notochord by a band of mesoderm, from which the common mesentery of the gut
is subsequently developed. The stomach has an additional attachment, viz., to
the ventral abdominal v>all as far as the umbilicus by the septum transversum.
The cephalic portion of the septum takes part in the formation of the diaphragm,
while the caudal portion into which the liver grows forms the ventral mesogastrium
(Fig. 984). The stomach undergoes a further dilatation, and its two curvatures
can be recognized (Figs. 983, B, and 984), the greater directed toward the vertebral
column and the lesser toward the anterior wall of the abdomen, while its two
surfaces look to the right and left respectively. Behind the stomach the gut
undergoes great elongation, and forms a V-shaped loop which projects downward
and forward; from the bend or angle of the loop the vitelline duct passes to the
umbilicus (Fig. 984). For a time a considerable part of the loop extends beyond
the abdominal cavity into the umbilical cord, but by the end of the third month
it is w ithdrawn within the cavity. With the lengthening of the tube, the mesoderm,
which attaches it to the future vertebral column and carries the bloodvessels for
the supply of the gut, is thinned and drawn out to form the posterior common
mesentery. The portion of this mesentery attached to the greater curvature of
the stomach is named the dorsal mesogastrium, and the part which suspends the
1104
SPLANCHNOLOGY
colon is termed the mesocolon (Fig. 985). About the sixth week a diverticulum
of the gut appears just behind the opening of the vitelline duct, and indicates
Xotoclwrd Rathke's pouch
Lung diverticulum
Stomach -f
Liver
Opening into
yolk-sac
Allantoisl--
, Mandibular
arch
— Postallantoic part
of hind-gut
Wolffian duct
Lung diverticulum
Esophagus ^
Thyroid gland
Mandibular arch
I I Sotochord
I I
I I
I
Stomach
Pancreas
Bile-duct
Vitelline duct
Allantois
— Rathke's pouch
Postallantoic part
of hind-gut
— Wolffian duct
B
FiQ. 982. — Sketches in profile of two stages in the development of the human digestive tube. (His.)
-•1 X 30. By. 20.
the future cecum and vermiform process. The part of the loop on the distal side
.of the cecal diverticulum increases in diameter and forms the future ascending
THE DIGESTIVE APPARATUS
1105
and transverse portions of the large intestine. Until the fifth month the cecal
diverticulum has a uniform caliber, but from this time onward its distal part
remains rudimentary and forms the vermiform process, while its proximal part
expands to form the cecum. Changes also take place in the shape and position
of the stomach. Its dorsal part or greater curvature, to which the dorsal meso-
Trachea-.
SsopJiagus I
Stomach
Lung
--Trachea
Pancreas
Bile-duct —
SI -shaped loop of
small intestine -
Vitelline duct -
Cloaca. •
Bile-duct
Pancreas
_- Lung
— • •Usophagus
— %—-Stomach
Fig. 983. — -Front view of two successive stages in the development of the digestive tube. (Ilis.)
gastrium is attached, grows much more rapidly than its ventral part or lesser
curvature to which the ventral mesogastrium is fixed. Further, the greater curva-
ture is carried downward and to the left, so that the right surface of the stomach is
now directed backward and the left surface forward (Fig. 986), a change in position
Septum iransversum
Liver
Falciform ligament of liver
Lesser omentum
Umbilical vein.
Umbilical cord
Aorta
Dorsal mesogastrium
Stomach
Intestinal V-shaped loop
Mesentery
Colon
Fig. 984. — The primitive mesentery of a six weeks' human embryo, half schematic. (Kollmann.)
which explains why the left vagus nerve is found on the front, and the right vagus
on the back of the stomach. The dorsal mesogastrium being attached to the greater
curvature must necessarily follow its movements, and hence it becomes greatly
elongated and drawn lateralward and ventralward from the vertebral column,
and, as in the case of the stomach, the right surfaces of both the dorsal and ventral
70
1106
SPLANCHNOLOGY
mesogastria are now directed backward, and the left forward. In this way a pouch,
the bursa omentalis, is formed behind the stomach, and this increases in size as
the digestive tube undergoes further development; the entrance to the pouch
constitutes the future foramen epiploicum or foramen of Winslow. The duodenum
is developed from that part of the tube which immediately succeeds the stomach ;
it undergoes little elongation, being more or less fixed in position by the liver and
pancreas, which arise as diverticula from it. The duodenum is at first suspended
by a mesentery, and projects forward in the form of a loop. The loop and its mes-
entery are subsequently displaced by the transverse colon, so that the right surface
of the duodenal mesentery is directed backward, and, adhering to the parietal
peritoneum, is lost. The remainder of the digestive tube becomes greatly elongated,
and as a consequence the tube is coiled on itself, and this elongation demands a
corresponding increase in the width of the intestinal attachment of the mesentery,
which becomes folded.
Aorta
Ventral mesogastriam
Spleen
Dorsal
mesogastrium
Celiac artery
Pancreas
Superior mesenteric
artery
Mesentery
Inferior mesenteric artery
FiQ. 985.
Hind-gut
-Abdominal part of digestive tube and its attachment to the primitive or common mesenten,'-
embrj-o of six weeks. (After Toldt.)
Human
At this stage the small and large intestines are attached to the vertebral column
by a common mesentery, the coils of the small intestine falling to the right of the
middle line, while the large intestine lies on the left side.^
The gut is now rotated upon itself, so that the large intestine is carried over in
front of the small intestine, and the cecum is placed immediately below the liver;
about the sixth month the cecum descends into the right iliac fossa, and the large
intestine forms an arch consisting of the ascending, transverse, and descending
portions of the colon — the transverse portion crossing in front of the duodenum
and lying just below the greater curvature of the stomach; within this arch the
coils of the small intestine are disposed (Fig. 988). Sometimes the downward
' Sometimes this condition persists throughout life, and it is then found that the duodenum does not cross from the
right to the left side of the vertebral column, but lies entirely on the right side of the median plane, where it is continued
into the jejunum; the arteries to the small intestine (aa. intestinales) also arise from the right instead of the left side
of the superior mesenteric artery.
THE DIGESTIVE APPARATUS
1107
progress of the cecum is arrested, so that in the adult it may be found lying imme-
"diately below the liver instead of in the right iliac region.'
Further changes take place in the bursa omcntalis and in the common mesentery,
and give rise to the peritoneal relations seen in the adult. The bursa omentalis,
which at first reaches only as far as the greater curvature of the stomach, grows
downward to form the greater omentum, and this downward extension lies in front
of the transverse colon and the coils of the small intestine (Fig. 989). Above, before
the pleuro-peritoneal opening is closed, the bursa omentalis sends up a diverticulum
Sth cervical nerve
Ist thoracic
vertebra
Pericardium
Lung
Suprarenal
gland
Stomach
I2th thoracic
nerve
Mesonephros
Kidney
5lh lumbar
nerve
Small
intestine
Great 1 Ureter
Cecum intestine Wolffia7i duct
Fig. 986. — Reconstruction of a human embrj-o of 17 mm. (After Mall.)
on either side of the esophagus; the left diverticulum soon disappears, but the right
is constricted off and persists in most adults as a small sac lying v,ithin the thorax
on the right side of the lower end of the esophagus. The anterior layer of the
transverse mesocolon is at first distinct from the posterior layer of the greater
omentum, but ultimately the two blend, and hence the greater omentum appears as
if attached to the transverse colon (Fig. 990). The mesenteries of the ascending and
descending parts of the colon disappear in the majority of cases, while that of the
small intestine assumes the oblique attachment characteristic of its adult condition.
The lesser omentum is formed, as indicated above, by a thinning of the meso-
derm or ventral mesogastrium, which attaches the stomach and duodenum to the
anterior abdominal wall. By the subsequent growth of the liver this leaf of
mesoderm is divided into two parts, viz., the lesser omentum between the stomach
1108
SPLANCHNOLOGY
and liver, and the falciform and coronary ligaments between the liver and the
abdominal wall and diaphragm (Fig. 989).
The Rectum and Anal Canal. — The hind-gut is at first prolonged backward into
the body-stalk as the tube of the allantois; but, with the growth and flexure of the
ilesogaitrium'
Bile duct
Duodenum
Mesenteiy
Cecum
Small
intestine
Vitelline duct
Greater
curvature
of utomach
Greater
omentum
Point where
intestinal
loops cross
each other
Meso-
gastrium
Duodenum
Mesocolon
Large
intestine
Rectum
Cecum
Vermiform
process
Mesentery
Vitelline dxict
Greater
curvature of
stomach
^:::^r-^ Greater omentum
Point sphere
19 intestinal
loops cross
each other
Mesocolon
Large intestine
Small intestine
Rectum,
Fig. 987. — Diagrams to illustrate two stages in the development of the digestive tube anil its mesentery.
The arrow indicates the entrance to the bursa omentalis.
Fig. 988. — Final disposition of the
intestines and their vascular relations.
(Jonnesco.) A. Aorta. H. Hepatic
artery. M, Col. Branches of superior
mesenteric artery. »«, to'. Branches
of inferior mesenteric artery. 5.
Splenic artery.
Ventral
mesogastrium
Liver
Umbilical vein
Border of
ventral
mesogasirium
Bursa
om,entalis
Pancreas
Dorsal
mesogastrium
Duodenum
Greater
omentum
Transverse
mesocolon
Transverse
colon
Fig. 989. — Schematic figure of the bursa omentalis, etc. Human
emlDryo of eight weeks. (KoUmann.)
Stomach
tail-end of the embryo, the body-stalk, with its contained allantoic tube, is carried
forward to the ventral aspect of the body, and consequently a bend is formed at the
THE DIGESTIVE APPARATUS
1109
junction of the hind-gut and allantois. This bend becomes dihated into a pouch,
which constitutes the entodermal cloaca; into its dorsal part the hind-gut opens,
and from its ventral part the allantois passes forward. At a later stage the Wolffian
and Mullerian ducts open into its ventral portion. The cloaca is, for a time, shut
Diaphragm
Liver
Lesser omenhim
Bursa omtntalis-
Stomach-
Pancrea s
Greater omenUnn
Transverse mesocolon -
Transverse colon "
Diaphragm
I
Liver ;
Small intestine
Duodenum
Lexupr omentum
-- Bursa omentalis
Stomach
— Pancreas
- OUiti'rated part of mesogastritim
— Duodenum
Transverse colon
Mesentery
Small intestine
mesentery
Fig. 990. — Diagrams to illustrate the development of the greater omentum and transverse mesocolon.
off from the anterior by a membrane, the cloacal membrane, formed by the apposi-
tion of the ectoderm and entoderm, and reaching, at first, as far forward as the
future umbilicus. Behind the umbilicus, however, the mesoderm subsequently
extends to form the lower- part of the abdominal wall and symphysis pubis. By
the growth of the surrounding tissues the cloacal membrane comes to lie at the
bottom of a depression, which is lined by ectoderm and named the ectodermal
cloaca (Fig. 991).
The entodermal cloaca is divided into a dorsal and a ventral part by means of a
partition, the urorectal septimi (Fig. 992), which grows downward from the ridge
Wolffian duct
Ectodermal cloaca
Cloacal mcmhran
NotocJwrd
Fig. 991. — Tail end of human embryo from fifteen to
eighteen days old. (From model by Keibel.)
Wolffian duct
Fig. 992. — -Cloaca of human embryo from
twenty-five to twenty-seven days old. (From
model by Keibel.)
separating the allantoic from the cloacal opening of the intestine and ultimately
fuses with the cloacal membrane and divides it into an anal and a urogenital part.
The dorsal part of the cloaca forms the rectum, and the anterior part of the uro-
genital sinus and bladder. For a time a communication named the cloacal duct
1110
SPLANCHNOLOGY
exists between the two parts of the cloaca below the urorectal septum; this duct
occasionally persists as a passage between the rectum and urethra. The anal
canal is formed by an invagination of the ectoderna behind the urorectal septum.
This invagination is termed the proctodeum, and it meets with the entoderm of the
hind-gut and forms with it the anal membrane. By the absorption of this membrane
the anal canal becomes continuous with the rectum (Fig. 993). A small part of the
hind-gut projects backward beyond the anal membrane; it is named the post-anal
gut (Fig. 991), and usually becomes obliterated and disappears.^
Ureter.
Wolffian duct
Miillerian duct
Bladder
SymphyiU pubis
Glarui penis
Urethra
Vertebral column
Fia. 993. — Tail end of human embryo, from eight and a half to nine weeks old.
(From model by KeibelJ
THE MOUTH (CAVUM ORIS; ORAL OR BUCCAL CAVITY).
The cavity of the mouth is placed at the commencement of the digestive tube
(Fig. 994); it is a nearly oval-shaped cavity which consists of two parts: an
outer, smaller portion, the vestibule, and an inner, larger part, the mouth cavity
proper.
The Vestibule (vestibulum oris) is a slit-like space, bounded externally by the
lips and cheeks; internally by the gums and teeth. It communicates with the
surface of the body by the rima or orifice of the mouth. Above and below, it is
limited by the reflection of the mucous membrane from the lips and cheeks to
the gum covering the upper and lower alveolar arch respectively. It receives the
secretion from the parotid salivary glands, and communicates, when the jaws are
closed, with the mouth cavity proper by an aperture on either side behind the
wisdom teeth, and by narrow clefts between opposing teeth.
The Mouth Cavity Proper (cavum oris propmim) (Fig. 1014) is bounded laterally
and in front by the alveolar arches with their contained teeth; behind, it communi-
cates with the pharynx by a constricted aperture termed the isthmus faucium.
It is roofed in by the hard and soft palates, while the greater part of the floor is
formed by the tongue, the remainder by the reflection of the mucous membrane
from, the sides and under surface of the tongue to the gum lining the inner aspect
of the mandible. It receives the secretion from the submaxillary and sublingual
salivary glands.
Structure. — The mucous membrane lining the mouth is continuous with the integument at
the free margin of the lips, and with the mucous lining of the pharynx behind; it is of a rose-
pink tinge during Ufe, and verj' thick where it overlies the hard parts bounding the cavity. It
is covered by stratified squamous epitheUimi.
1 Consult, in this connection, the following article: "A Contribution to the Morphology of the Human Urino-
genital Tract," by D. Berry Hart, M.D., F.R.C.P.E., Journal of Anatomy and Physiology, April, 1901, vol. xxxv.
THE MOUTH
1111
The Lips {labia oris), the two fleshy folds which surround the riraa or orifice of
the mouth, are formed externally of integument and internally of mucous mem-
brane, between which are founcl the Orbicularis oris muscle, the labial vessels,
some nerves, areolar tissue, and fat, and numerous small labial glands. The inner
surface of each lip is connected in the middle line to the corresponding gum by a
fold of mucous membrane, the frenulum — the upper being the larger.
Hypophysi
Pharyngeal
tonsil
Orifice of
auditory tube
Nasal part of
pharynx II l'- '\
Anterior arch nf If X-^'/NN 'v.
atlas ~iiT^sr\\v
Odontoid process
of axis ff
Oral part of
pharynx " Jj^.'
Body of axis
Epiglottis
Laryngeal part
of pharynx tttWvf^
Aryepiglottic fold "'^~''— -
Cricoid cartilage "^
Ijsophagus
Frenulum Ungues
Mylohyoideus muscle
II y Old hone
Thyroid cartilage
Ventricular fold
Vocal fold
Cricoid cartilage
~ Isthmus of thyroid gland
Fig. 994. — Sagittal section of nose mouth, pharynx, and larj'nx.
The Labial Glands (j/Iaiidulcp labiates) are situated between the mucous membrane
and the Orbicularis oris, around the orifice of the mouth. They are circular in form,
and about the size of small peas; their ducts open by minute orifices upon the
mucous membrane. In structure they resemble the salivary glands.
1112 SPLANCHNOLOGY
The Cheeks (hvcccp) form the sides of the face, and are continuous in front with
the lips. They are composed externally of integument; internally of mucous
membrane; and between the two of a muscular stratum, besides a large quantity
of fat, areolar tissue, vessels, nerves, and buccal glands.
Structure. — The mucous membrane lining the cheek is reflected above and below upon the
gums, and is continuous behind with the lining membrane of the soft palate. Opposite the
second molar tooth of the maxilla is a papilla, on the summit of which is the aperture of the
parotid duct. The principal muscle of the cheek is the Buccinator; but other muscles enter into
its formation, viz., the Z^^gomaticus, Risorius, and Platysma.
The buccal glands are placed between the mucous membrane and Buccinator muscle: they
are similar in structure to the labial glands, but smaller. About five, of a larger size than the
rest, are placed between the Masseter and Buccinator muscles around the distal extremity of
the parotid duct; their ducts opeji in the mouth opposite the last molar tooth. They are called
molar glands.
The Gums (gingivce) are composed of dense fibrous tissue, closely connected to
the periosteum of the alveolar processes, and surrounding the necks of the teeth.
They are covered by smooth and vascular mucous membrane, which is remark-
able for its limited sensibility. Around the necks of the teeth this membrane
presents numerous fine papillae, and is reflected into the alveoli, where it is con-
tinuous with the periosteal membrane lining these cavities.
The Palate (palatum) forms the roof of the mouth; it consists of two portions,
the hard palate in front, the soft palate behind.
The Hard Palate (palatvm durum) (Fig. 1014) is bounded in front and at the sides
by the alveolar arches and gums; behind, it is continuous with the soft palate.
It is covered by a dense structure, formed by the periosteum and mucous mem-
brane of the mouth, which are intimately adherent. Along the middle line is a
linear raphe, which ends anteriorly in a small papilla corresponding with the
incisive canal. On either side and in front of the raphe the mucous membrane
is thick, pale in color, and corrugated; behind, it is thin, smooth, and of a deeper
color; it is covered with stratified squamous epithelium, and furnished with
numerous palatal glands, which lie between the mucous membrane and the surface
of the bone.
The Soft Palate (palatum molle) (Fig. 1014) is a movable fold, suspended from the
posterior border of the hard palate, and forming an incomplete septum between
the mouth and pharynx. It consists of a fold of mucous membrane enclosing
muscular fibers, an aponeurosis, vessels, nerves, adenoid tissue, and mucous glands.
When occupjang its usual position, i. e., relaxed and pendent, its anterior surface
is concave, continuous with the roof of the mouth, and marked by a median raphe.
Its posterior surface is convex, and continuous with the mucous membrane covering
the fioor of the nasal cavities. Its upper border is attached to the posterior margin
of the hard palate, and its sides are blended with the pharynx. Its lower border
is free. Its lower portion, which hangs like a curtain between the mouth and
pharynx is termed the palatine velum.
Hanging from the middle of its lower border is a small, conical, pendulous
process, the palatine uvula; and arching lateralward and downward from the base
of the uvula on either side are two curved folds of mucous membrane, containing
muscular fibers, called the arches or pillars of the fauces.
The Teeth (denies) (Figs. 995 to 997). — Man is provided with two sets of teeth,
which make their appearance at difl^erent periods of life. Those of the first set
appear in childhood, and are called the deciduous or milk teeth. Those of the second
set, which also appear at an early period; may continue until old age, and are
named permanent.
The deciduous teeth are twenty in number: four incisors, two canines, and four
molars, in each jaw.
THE MOUTH
1113
The permanent teeth are thirty-two in number: four incisors, two canines, four
premolars, and six molars, in each jaw.
Fig. 995. — Side view of the teeth and jaws.
Incisive, canals
Incisors
Incisive foramen
Foramina cf Scarpa
Palatine process cf maxilla
Horizontal part of palatine bone
\ Greater palatine foramen
Lesser palatine foramina
Premolars
Molars
Fig. 996. — Permanent teeth of upper dental arch,
seen from below.
Fig. 997. — Permanent teeth of right half of
lower dental arch, seen from above.
1114
SPLANCHNOLOGY
The dental formulae may be represented as follows:
Deciduous Teeth.
Upper jaw
mol.
2
can.
1
in. in.
9 9
can.
1
mol.
9
Lower jaw
Upper jaw
1
2 I 2
2
1
- } Total 20
J
Permanent Teeth.
mol. pr. mol. can. in. in.
3 2 12 2
can. pr. mcl. mol
1 2 3
Lower jaw
1
Total 32
3J
General Characteristics. — Each tooth consists of three portions: the crown,
projecting above the gum; the root, imbedded in the alveolus; and the neck, the
constricted portion between the crown and root.
Fig. 998. — MaxiLbe at about one year. (Noyes.)
The roots of the teeth are firmly implanted in depressions within the alveoli;
these depressions are lined with periosteum which invests the tooth as far as the
neck. At the margins of the alveoli, the periosteum is continuous with the fibrous
structure of the gums.
In consequence of the curve of the dental arch, terms such as anterior and
posterior, as applied to the teeth, are misleading and confusing. Special terms
are therefore used to indicate the different surfaces of a tooth: the surface directed
toward the lips or cheek is known as the labial or buccal surface; that directed
toward the tongue is described as the lingual surface; those surfaces which touch
neighboring teeth are termed surfaces of contact. In the case of the incisor and
canine teeth the surfaces of contact are medial and lateral; in the premolar and
molar teeth they are anterior and posterior.
The superior dental arch is larger than the inferior, so that in the normal condi-
tion the teeth in the maxillae slightly overlap those of the mandible both in front
and at the sicffes. Since the upper central incisors are wider than the lower, the
other teeth in the upper arch are thrown somewhat distally, and the two sets do
THE MOUTH
1115
not quite correspond to each other when the mouth is closed: thus the upper
canine tooth rests partly on the lower canine and partly on the first premolar,
and the cusps of the upper molar teeth lie behind the corresponding cusps of the
lower molar teeth. The two series, however, end at nearly the same point behind;
this is mainly because the molars in the upper arch are the smaller.
■pr
fl
'lu
M
Fig. 999. — The complete temporary dentition (about three years), showing the relation of the developing permanent
teeth. (Noyes.)
Fig. 1000. — The complete temporary dentition and the first permanent molar. Note the relation of the bicuspids to
the temporary molars. (In the seventh year.) (Noyes.)
The Permanent Teeth {denies permanentes) (Figs. 1002, 1003). — The Incisors (denies
ineisivi; incisive or cutting teeth) are so named from their presenting a sharp cutting
edge, adapted for biting the food. They are eight in number, and form the four
front teeth in each dental arch.
1116
SPLANCHNOLOGY
The crown is directed vertically, and is chisel-shaped, being bevelled at the expense
of its lingual surface, so as to present a sharp horizontal cutting edge, which,
before being subjected to attrition, presents three small prominent points separated
by two slight notches. It is convex, smooth, and highly polished on its labial
surface; concave on its lingual surface, where, in the teeth of the upper arch, it is
frequently marked by an inverted V-shaped eminence, situated near the gum.
This is known as the basal ridge or cingulum. The neck is constricted. The root
is long, single, conical, transversely flattened, thicker in front than behind, and
slightly grooved on either side in the longitudinal direction.
Fig. 1001. — Front view of the skull shown in Fig. 1000. Note the relation of the perry.anent incisors and cuspids to each
other and the roots of the temporary teeth. (Noyes.)
The upper incisors are larger and stronger than the lower, and are directed
obliquely downward and forward. The central ones are larger than the lateral,
and their roots are more rounded.
The lower incisors are smaller than the upper: the central ones are smaller than
the lateral, and are the smallest of all the incisors. They are placed vertically
and are somewhat bevelled in front, where they have been worn down by contact
with the overlapping edge of the upper teeth. The cingulum is absent.
The Canine Teeth {denies canini) are four in number, two in the upper, and two
in the lower arch, one being placed laterally to each lateral incisor. They are larger
and stronger than the incisors, and their roots sink deeply into the bones, and
cause well-marked prominences upon the surface.
THE MOUTH
111'
The crown is large and conical, very convex on its labial surface, a little hollowed
and uneven on its lingual surface, and tapering to a blunted point or cusp, which
projects beyond the level of the other teeth. The root is single, but longer and
thicker than that of the incisors, conical in form, compressed laterally, and marked
by a slight groove on each side.
Fig. 1002. — Permanent teetli. Right side. (Burchard.)
Superior molars . f
_ Maxillary sinus
First and second
superior pre-
,/ molars
Superior
canines
Lateral and
medial
incisors
First and sec-
ond inferior
premolars
Mandibular canal '
Mental fora-
men
Inferior molars
Fig. 1003. — Tlie permanent teetli, viewed from the right. The external layer of bone has been jiarlly removed and the
maxillary isinus has been opened. (Spalteholz.)
The upper canine teeth (popularly called eye teeth) are larger and longer than
the lower, and usually present a distinct basal ridge.
. The lower canine teeth (popularly called stomach teeth) are placed nearer the
middle line than the upper, so that their summits correspond to the intervals
between the upper canines and the lateral incisors.
1118
SPLANCHNOLOGY
The Premolars or Bicuspid teeth (dentcs prcrniohres) are eight in number, four
in each arch. They are situated lateral to and behind the canine teeth, and are
smaller and shorter than they.
The crown is compressed antero-posteriorly, and surmounted by two pyramidal
eminences or cusps, a labial and a lingual, separated by a groove; hence their name
bicuspid. Of the two cusps the labial is the larger and more prominent. The
neck is oval. The root is generally single, compressed, and presents in front and
behind a deep groove, which indicates a tendency in the root to become double.
The apex is generally bifid.
The upper premolars are larger, and present a greater tendency to the division
of their roots than the lower; this is especially the case in the first upper pre-
molar.
The Molar Teeth {denies molares) are the largest of the permanent set, and their
broad crowns are adapted for grinding and pounding the food. They are twelve
in number; six in each arch, three being placed posterior to each of the second
premolars.
The crown of each is nearly cubical in form, convex on its buccal and lingual
surfaces, flattened on its surfaces of contact; it is surmounted by four or five tuber-
cles, or cusps, separated from each other by a crucial depression; hence the molars
are sometimes termed multicuspids. The neck is distinct, large, and rounded.
Upper Molars. — As a rule the first is the largest, and the third the smallest of
the upper molars. The crown of the first has usually four tubercles; that of the
second, three or four; that of the third, three. Each upper molar has three roots,
and of these two are buccal and nearly parallel to one another; the third is lingual
and diverges from the others as it runs upward. The roots of the third molar
{dejis serotinus or ivisdom-tooth) are more or less fused together.
Loiver Molars. — The lower molars are larger than the upper. On the crown
of the first there are usually five tubercles; on those of the second and third, four
or five. Each lower molar has two roots, an
anterior, nearly vertical, and a posterior,
directed obliquely backward; both roots are
grooved longitudinally, indicating a tendency
to division. The two roots of the third molar
{dens seroti7ius or icisdom tooth) are more or
less united.
The Deciduous Teeth {denies decidni; tem-
porary or milk teeth) (Fig. 1004). — The decid-
uous are smaller than, but, generally speak-
ing, resemble in form, the teeth which bear
the same names in the permanent set. The
hinder of the two molars is the largest of all
the deciduous teeth, and is succeeded by the
second premolar. The first upper molar has only three cusps— two labial, one
lingual; the second upper molar has four cusps. The first lower molar has four
cusps; the second lower molar has five. The roots of the deciduous molars are
smaller and more divergent than those of the permanent molars, but in other
respects bear a strong resemblance to them.
Structure of the Teeth. — On making a vertical section of a tooth (Fig. 1005), a cavity will be
found in the interior of the crown and the center of each root; it opens by a minute orifice at
the extremity of the latter. This is called the pulp cavity, and contains the dental pulp, a loose
connective tissue richly supphed with vessels and nerves, which enter the cavity through the
small aperture at the point of each root. Some of the cells of the pulp are arranged as a layer
on the wall of the pulp cavity; they are named the odontoblasts of Waldeyer, and dm-ing the
development of the tooth, are columnar in shape, but later on, after the dentin is fully formed,
they become flattened and resemble osteoblasts. Each has two fine processes, the outer one
Fig. 1004. — Deciduous teeth. Left side.
THE MOUTH
1119
passing into a dental canaliculus, the inner being continuous with the processes of the connective-
tissue cells of the pulp matrix.
The solid portion of the tooth consists of (1) the ivory or dentin, which forms the bulk of the
tooth; (2) the enamel, which covers the exposed part of the crown; and (3) a thin layer of bone,
the cement or crusta petrosa, which is disposed on the surface of the root.
The dentin (substantia eburnea; ivory) (Fig. 1007) forms the principal mass of a tooth. It is
a modification of osseous tissue, from which it differs, however, in structure. On microscopic
examination it is seen to consist of a number of minute wavy and branching tubes, the dental
canaliculi, imbedded in a dense homogeneous substance, the matrix.
Fig. 1006. — Vertical section of a molar tooth.
Fig. 100.5. — Vertical section of a tooth in silu. X 15.
c is placed in the pulp cavity, opposite the neck of the
tooth; the part above it is the crown, that below is the
root. 1. Enamel with radial and concentric markings.
2. Dentin with tubules and incremental lines. 3. Cement
or crusta petrosa, with bone corpuscles. 4. Dental
periosteum. 5. Mandible.
Crown
Neck
— Boot
Fig. 1007.-
-Vertical section of a premolar tooth.
(Magnified.)
The dental canaliculi (dentinal tubules) (Fig. 1008) are placed parallel with one another, and
open at their inner ends into the pulp cavity. In their course to the periphery they present two
or three curves, and are twisted on themselves in a spiral direction. These canahculi vary in
direction: thus in a tooth of the mandible they are vertical in the upper portion of the crown,
becoming oblique and then horizontal in the neck and upper part of the root, while toward the
lower part of the root they are inclined downward. In their course they divide and subdivide
dichotomously, and, especially in the root, give off minute branches, which join together in
loops in the matrix, or end blindly. Near the periphery of the dentin, the finer ramifications
of the canaliculi terminate imperceptibly by free ends. The dental canaliculi have definite walls,
consisting of an elastic homogeneous membrane, the dentinal sheath of Neumann, which resists
the action of acids; they contain slender cylindrical prolongations of the odontoblasts, first
described by Tomes, and named Tomes' fibers or dentinal fibers.
1120
SPLANCHNOLOGY
Cement
Interglobular
spaces
Dentin
The matrix {intertubular dentin) is translucent, and contains the chief part of the earthy
matter of the dentin. In it are a number of fine fibrils, which are continuous with the fibrils
of the dental pulp. After the earth}' matter has
been removed by steeping a tooth in weak acid,
the animal basis remaining maj' be torn into laminae
which run parallel with the pulp cavity, across the
direction of the tubes. A section of dry dentin often
displays a series of somewhat parallel Unes — the
incremental lines of Salter. These fines are com-
posed of imperfectly calcified dentin arranged in
layers. In consequence of the imperfection in the
calcifying process, little irregular cavities are left,
termed interglobular spaces (Fig. 1008). Normally
a series of these spaces is found toward the outer
surface of the dentin, where they form a layer which
is sometimes known as the granular layer. They
have received their name from the fact that they
are surrounded by minute nodules or globules of
dentin. Other curved fines may be seen parallel to
the surface. These are the lines of Schreger, and
are due to the optical effect of simultaneous curva-
ture of the dentinal fibers.
Chemical Composition. — According to Berzefius
and von Bibra, dentin consists of 28 parts of animal
and 72 parts of earthy matter. The animal matter
is converted by boiling into gelatin. The earthy
matter consists of phosphate of fime, carbonate of
lime, a trace of fluoride of calcium, phosphate of
magnesium, and other salts.
The enamel {snbsta?itia adamantina) is the hardest
and most compact part of the tooth, and forms a
thin crust over the exposed part of the crown, as far
as the commencement of the root. It is thickest on
the grinding surface of the crown, until worn away
by attrition, and becomes thinner toward the neck.
It consists of minute hexagonal rods or columns
termed enamel fibers or enamel prisms (prismata adamantina) . They lie parallel with one
another, resting by one extremity upon the dentin, which presents a number of minute depres-
sions for their reception; and forming the free surface of the crown by the other extremity.
The columns are directed vertically on the summit of the crown, horizontally at the sides; they
are about 4.u in diameter, and pursue a more or less wavy course. Each column is a six-sided
prism and presents numerous dark transverse shadings; these shadings are probably due to the
manner in which the columns are developed in successive stages, producing shallow constric-
tions, as will be subsequently explained. Another series of lines, having a brown appearance,
the parallel striae or colored lines of Retzius, is seen on section. According to Ebner, they are
produced by air in the interprismatic spaces; others believe that they are the result of true
pigmentation.
Numerous minute interstices intervene between the enamel fibers near their dentinal ends,
a provision calculated to allow of the permeation of fluids from the dental canaliculi into the
substance of the enamel.
Chemical Composition. — According to von Bibra, enamel consists of 96.5 per cent, of earthy
matter, and 3.5 per cent, of animal matter. The earthy matter consists of phosphate of lime,
with traces of fluoride of calcium, carbonate of lime, phosphate of magnesium, and other salts.
According to Tomes, the enamel contains the merest trace of organic matter.
The crusta petrosa or cement {substaritia ossea) is disposed as a thin laj'er on the roots of the
teeth, from the termination of the enamel to the apex of each root, where it is usually ^ery thick.
In structure and chemical composition it resembles bone. It contains, sparingly, the lacunae
and canaliculi which characterize true bone; the lacunae placed near the surface receive the
canaliculi radiating from the side of the lacunae toward the periodontal membrane; and those
more deeply placed join with the adjacent dental canaliculi. In the thicker portions of the
crusta petrosa, the lamellae and Haversian canals peculiar to bone are also found.
As age advances, the cement increases in thickness, and gives rise to those bony growths or
exostoses so common in the teeth of the aged; the pulp cavity also becomes partially filled up by
a hard substance, intermediate in structure between dentin and bone {osteodentin, Owen; second-
ary dentin, Tomes). It appears to be formed by a slow conversion of the dental pulp, which
shrinks, or even disappears.
Fig.
lOOS. — Transverse section of a portion of the
root of a canine tooth. X 300.
THE MOUTH
1121
Development of the Teeth (Figs. 1009 to 1012). — In describing the development of the teeth,
the mode of formation of the deciduous teeth must first be considered, and then that of the
permanent series.
"^ "^^'"^-u^rt^ ^, TiT" - ■^>^^
P.p.
Fio. 1009. — Sagittal section through the first lower deciduous molar of a human embryo 30 mm. long. (Rose.)
X 100. L.E.L. Labiodental lamina, here separated from the dental lamina. Z.L. Placed over the shallow dental
furrow, points to the dental lamina, which is spread out below to form the enamel germ of the future tooth. P.p.
Bicuspidate papilla, capped by the enamel germ. Z.S. Condensed tissue forming dental sac. M.E. Mouth epithelium
Fig. 1010. — Similar section through the canine tooth of an embryo 40 mm. long.
dental furrow. The other lettering as in Fig. 1009.
(Rose.) X 100. L.F. Labio
Dental furrow
Remains of enamel germ .^^JMiKfU'^'f'^'^'
Secondary enamel germ
Meckel's cartilage
Enamel organ
Dental 'papilla
\~ Mandible
Fig. 1011. — Verticai section of the mandible of an early human fetus. X 25.
71
1122
SPLANCHNOLOGY
P
I
ep.sch.
Development of the Deciduous Teeth. — The development of the deciduous teeth begins
about the sixth week of fetal life as a thickening of the epithehum along the hne of the future
jaw, the thickening being due to a rapid multiplication of the more deeply situated epithehal
cells. As the cells multiply they extend into the subjacent mesoderm, and thus form a ridge
or strand of cells imbedded in mesoderm. About the seventh week a longitudinal sphtting or
cleavage of this strand of cells takes place, and it becomes divided into two strands; the separa-
tion begins in front and extends laterally, the process occupying four or five weeks. Of the two
strands thus formed, the labial forms the labiodental lamina; while the other, the lingual,
is the ridge of cells in connection with which the teeth, both deciduous and permanent, are
developed. Hence it is known as the dental lamina or common dental germ. It forms a flat
band of cells, which grows into the substance of the embryonic jaw, at first horizontally
inward, and then, as the teeth develop, vertically, i. e., upward in the upper jaw, and
downward in the lower jaw. While still maintaining a horizontal direction it has two edges
— an attached edge, continuous with the epithelium lining the mouth, and a free edge, projecting
inward, and imbedded in the mesodermal tissue of the embryonic jaw. Along its line of
attachment to the buccal epithelium is a shallow groove, the dental furrow.
About the ninth week the dental lamina begins
to develop enlargements along its free border.
These are ten in number in each jaw, and each
corresponds to a future deciduous tooth. They
consist of masses of epithelial cells; and the cells
of the deeper part — that is, the part farthest from
the margin of the jaw — increase rapidly and spread
out in all directions. Each mass thus comes to
assume a club shape, connected with the general
epithelial lining of the mouth by a narrow neck,
embraced by mesoderm. They are now kno^-n as
special dental germs. After a time the lower ex-
panded portion inclines outward, so as to form an
angle with the superficial constricted portion, which
is sometimes known as the neck of the special
dental germ. About the tenth week the meso-
dermal tissue beneath these special dental germs
becomes differentiated into papillae; these grow
upward, and come in contact with the epithelial
cells of the special dental germs, which become
folded over them like a hood or cap. There is,
then, at this stage a papilla (or papillae) which
has already begun to assume somewhat the shape
of the crown of the future tooth, and from which
the dentin and pulp of the tooth are formed, sur-
mounted by a dome or cap of epithehal cells from
which the enamel is derived.
In the meantime, while these changes have been
going on, the dental lamina has been extending
backward behind the special dental germ corre-
sponding to the second deciduous molar tooth,
and at about the seventeenth week it presents an
enlargement, the special dental germ, for the first
permanent molar, soon followed by the formation
of a papilla in the mesodermal tissue for the same tooth. This is followed, about the sixth
month after birth, by a further extension backward of the dental lamina, with the formation
of another enlargement and its corresponding papilla for the second molar. And finally the pro-
cess is repeated for the third molar, its papilla appearing about the fifth year of life.
After the formation of the special dental germs, the dental lamina undergoes atrophic changes
and becomes cribriform, except on the Ungual and lateral aspects of each of the special germs
of the temporary teeth, where it imdergoes a local thickening forming the special dental germ
of each of the successional permanent teeth — i. c., the ten anterior ones in each jaw. Here the
same process goes on as has been described in connection with those of the deciduous teeth:
that is, they recede into the substance of the gum behind the germs of the deciduous teeth. As
they recede they become club-shaped, form expansions at their distal extremities, and finally
meet papillae, which have been formed in the mesoderm, just in the same manner as was the
case in the deciduous teeth. The apex of each papilla indents the dental germ, which encloses
it, and, forming a cap for it, becomes converted into the enamel, while the papilla forms the
dentin and pulp of the permanent tooth.
The special dental germs consist at first of roimded or polyhedral epithehal cells; after the
.e^:
Fig. 1012. — Longitudinal section of the lower part
of a growing tooth, showing the extension of the layer
of adamantoblast.'? beyond the crown to mark off
the limit of formation of the dentin .of thie root.
(Rose.) ad. Adamantoblasts, continuous below with
ep.sch., the epithelial sheath of Hertwig. rf. Dentin.
en. Enamel, od. Odontoblasts, p. Pulp.
THE MOUTH 1123
formation of the papillae, these cells undergo a differentiation into three layers. Those which
are in immediate contact with the papilla become elongated, and form a layer of well-marked
columnar epithehum coating: the papilla. Thoy are the cells which form the enamel fibers,
and are therefore termed enamel cells or adamantoblasts. The cells of the outer layer of the
special dental germ, which are in contact with the inner surface of the dental sac, presently to
be described, are much shorter, cubical in form, and are named the external enamel epithelium.
All the intermediate round cells of the dental germ between these two layers undergo a peculiar
change. They become stellate in shape and develop processes, which unite to form a net-work
into which fluid is secreted; this has the appearance of a jelly, and to it the name of enamel pulp
is given. This transformed special dental germ is now known under the name of enamel organ
(Fig. 1011).
^\ hile these changes are going on, a sac is formed around each enamel organ from the sur-
rounding mesodermal tissue. This is known as the dental sac, and is a vascular membrane
of connective tissue. It grows up from below, and thus encloses the whole tooth germ; as it
grows it causes the neck of the enamel organ to atrojihy and disappear; so that all communi-
cation between the enamel organ and the superficial epithelium is cut off. At this stage there
are vascular papillte surmounted by caps of epithelial cells, the whole being surrounded by
by membranous sacs.
Formation of the Enamel. — The enamel is formed exclusively from the enamel cells or adaman-
toblasts of the special dental germ, either by direct calcification of the coliminar cells, which
become elongated into the hexagonal rods of the enamel; or, as is more generally beUeved, as
a secretion from the adamantoblasts, witliin which calcareous matter is subsequently deposited.
The process begins at the apex of each cusp, at the ends of the enamel cells in contact with
the dental papilla. Here a fine globular deposit takes place, being apparently shed from the end
of the adamantoblasts. It is known by the name of the enamel droplet, and resembles keratin
in its resistance to the action of mineral acids. This droplet then becomes fibrous and calcifies
and forms the first layer of the enamel; a second droplet now appears and calcifies, and so on;
successive droplets of keratin-like material are shed from the adamantoblasts and form successive
layers of enamel, the adamantoblasts gradually receding as each layer is produced, until at the
termination of the process they have almost disappeared. The intermediate cells of the enamel
pulp atrophy and disappear, so that the newly formed calcified material and the external enamel
epithehum come into apposition. This latter layer, however, soon disappears on the emergence
of the tooth beyond the gum. After its disappearance the crown of the tooth is still covered
by a distinct membrane, which persists for some time. This is known as the cuticula dentis, or
Nasmjrth's membrane, and is beheved to be the last-formed layer of enamel derived from the
adamantoblasts, which has not become calcified. It forms a horny layer, which may be sepa-
rated from the subjacent calcified mass by the action of strong acids. It is marked by the hexagonal
impressions of the enamel prisms, and, when stained by nitrate of silver, shows the characteristic
appearance of epithehum.
Fortnation of the Dentin. — While these changes are taking place in the epithelium to form
the enamel, contemporaneous changes occurring in the differentiated mesoderm of the dental
papillae result in the formation of the dentin. As before stated, the first germs of the dentin are
the papillae, corresponding in number to the teeth, formed from the soft mesodermal tissue
which bounds the depressions containing the special enamel germs. The papillae grow upward
into the enamel germs and become covered by them, both being enclosed in a vascular connective
tissue, the dental sac, in the manner above described. Each papilla then constitutes the forma-
tive pulp from which the dentin and permanent pulp are developed; it consists of rounded cells
and is very vascular, and soon begins to assume the shape of the futiu-e tooth. The next step
is the appearance of the odontoblasts, which have a relation to the development of the teeth
similar to that of the osteoblasts to the fomiation of bone. They are formed from the cells
of the periphery of the papilla — that is to say, from the cells in immediate contact with the
adamantoblasts of the special dental germ. These cells become elongated, one end of the
elongated cell resting against the epithelium of the special dental germs, the other being tapered
and oftened branched. By the direct transformation of the peripheral ends of these cells, or
by a secretion from them, a laj'er of uncalcified matrix (predentin) is formed which caps the
cusp or cusps, if there are more than one, of the papillae. This matrix becomes fibrillated, and
in it islets of calcification make their appearance, and coalescing give rise to a continuous layer
of calcified material which covers each cusp and constitutes the first layer of dentin. The odon-
toblasts, having thus formed the first layer, retire toward the center of the papilla, and, as they
do so, produce successive layers of dentin from their peripheral extremities — that is to say,
they form the dentinal matrix in which calcification subsequently takes place. As they thus
recede from the peripher}' of the papilla, they leave behind them filamentous processes of cell
protoplasm, provided with finer side processes; these are surromided by calcified material, and
thus form the dental canaliculi, and, by then- side branches, the anastomosing canahculi: the
processes of protoplasm contained within them constitute the dentinal fibers {Tomes' fibers).
In this way the entire thickness of the dentin is developed, each canahculus being completed
1 124 SPLANCHNOLOG Y
throughout its whole length by a single odontoblast. The central part of the papilla does not
undergo calcification, but persists as the pulp of the tooth. In this process of fornaation of dentin
it has been shown that an uncalcified matrix is first developed, and that in this matrix islets of
calcification appear which subsequently blend together to form a cap to each cusp: in like manner
successive layers are produced, which ultimately become blended with each other. In certain
places this blending is not complete, portions of the matrix remaining uncalcified between the
successive layers; this gives rise to little spaces, which are the interglobular spaces alluded to
above.
Formation of the Cement. — The root of the tooth begins to be formed shortly before the crown
emerges through the gum, but is not completed until some time afterward. It is produced by a
downgrowth of the epithelium of the dental germ, which extends almost as far as the situation
of the apex of the future root, and determines the form of this portion of the tooth. This fold
of epitheUum is known as the epithelial sheath, and on its papillary surface odontoblasts appear,
which in turn form dentin, so that the dentin formation is identical in the crown and root of the
tooth. After the dentin of the root has been developed, the vascular tissues of the dental sac
begin to break through the epitheUal sheath, and spread over the surface of the root as a layer
of bone-forming material. In this osteoblasts make their appearance, and the process of ossi-
fication goes on in identically the same manner as in the ordinary intramembranous ossification
of bone. In this way the cement is formed, and consists of ordinary bone containing canalicuh
and lacunae.
Formation of the Alveoli. — About the fourteenth week of embryonic Kfe the dental lamina
becomes enclosed in a trough or groove of mesodermal tissue, which at first is common to all the
dental germs, but subsequently becomes divided by bony septa into locuh, each loculus con-
taining the special dental germ of a deciduous tooth and its corresponding permanent tooth.
After birth each cavity becomes subdivided, so as to form separate loculi (the future alveoh)
for the deciduous tooth and its corresponding permanent tooth. Although at one time the whole
of the growing tooth is contained in the cavity of the alveolus, the latter never completely encloses
it, since there is always an apertm-e over the top of the cro-mi filled by soft tissue, by which the
dental sac is connected with the surface of the gum, and which in the permanent teeth is called
the gubemaculum dentis.
Development of the Permanent Teeth. — The permanent teeth as regards their development
may be divided into two sets: (1) those which replace the deciduous teeth, and which, like them,
are ten in number in each jaw: these are the successional permanent teeth; and (2) those which
have no deciduous predecessors, but are superadded distal to the temporarj^ dental series. These
are three in number on either side in each jaw, and are termed superadded permanent teeth.
They are the three molars of the permanent set, the molars of the deciduous set being replaced
by the premolars of the permanent set. The development of the successional permanent teeth —
the ten anterior ones in either jaw — has already been indicated. During their development the
permanent teeth, enclosed in their sacs, come to be placed on the lingual side of the deciduous
teeth and more distant from the margin of the futm-e gum, and, as already stated, are separated
from them by bony partitions. As the crown of the permanent tooth grows, absorption of these
bony partitions and of the root of the deciduous tooth takes place, through the agency of osteo-
clasts, which appear at this time, and finally nothing but the crown of the deciduous tooth remains.
This is shed or removed, and the permanent tooth takes its place.
The superadded permanent teeth are developed in the manner already described, by extensions
backward of the posterior part of the dental lamina in each jaw.
Eruption of the Teeth.— When the calcification of the different tissues of the tooth
is sufficiently advanced to enable it to bear the pressure to which it will be afterward
subjected, eruption takes place, the tooth making its way through the gum. The
gum is absorbed by the pressure of the crown of the tooth against it, which is
itself pressed up by the increasing size of the root. At the same time the septa
between the dental sacs ossify, and constitute the alveoli; these firmly embrace
the riecks of the teeth, and afford them a solid basis of support.
The eruption of the deciduous teeth commences about the seventh month after
birth, and is completed about the end of the second year, the teeth of the lower
jaw preceding those of the upper.
The following, according to C. S. Tomes, are the most usual times of eruption:
Lower central incisors
Upper incisors
Lower lateral incisors and first molars
Canines
Second molars .
6 to 9 months.
8 to 10 months.
15 to 21 months.
16 to 20 months.
20 to 24 months.
THE MOUTH
1125
There are, however, considerable variations in these times; thus, according
to Holt:
At the age of 1 vear a child should have 0 teeth.
" uVears " " 12
u 2 " '' " IG
" 2| " " " 20
n
it
i(
Calcification of the permanent teeth proceeds in the following order in the
lower jaw (in the upper jaw it takes place a little later): the first molar, soon
after birth; the central and lateral incisors, and the canine, about six months
after birth; the premolars, at the second year, or a little later; the second molar,
about the end of the second year;- the third molar, about the twelfth year.
The eruption of the permanent teeth takes place at the following periods, the
teeth of the lower jaw preceding those of the upper by short intervals:
First molars 6th vear.
Two central incisors
Two lateral incisors
First premolars
Second premolars
Canines .
Second molars
Third molars
7tli year.
8th year.
9th year.
. 10th year.
11th to 12th year.
12th to 13th year.
17th to 25th vear.
Toward the sixth year, before the shedding of the deciduous teeth begins, there
are twentj'-four teeth in each jaw, viz., the ten deciduous teeth and the crowns
of all the permanent teeth except the third molars.
The Tongue (Ungua). — The tongue is the principal organ of the sense of taste,
and an important organ of speech; it also assists in the mastication and deglutition
of the food. It is situated in the floor of the mouth, within the curve of the
body of the mandible.
Its Root (radix linguw; base) (P'ig. 954) is directed backward, and connected
with the hyoid bone by the Hyoglossi and Genioglossi muscles and the hyoglossal
membrane; with the epiglottis by three folds (glossoe pi glottic) of mucous membrane;
with the soft palate by the glossopalatine arches; and with the pharynx by the
Constrictores pharyngis superiores and the mucous membrane.
Its Apex (apex lingua-; tip), thin and narrow, is directed forward against the
lingual surfaces of the lower incisor teeth.
Its Inferior Surf ace (fades inferior lingnae; imder surface) (Fig. 1013) is connected
with the mandible by the Genioglossi; the mucous membrane is reflected from it
to the lingual surface of the gum and on to the floor of the mouth, where, in the
middle line, it is elevated into a distinct vertical fold, the frenulum linguae. On
either side lateral to the frenulum is a slight fold of the -mucous membrane, the
plica fimbriata, the free edge of which occasionally exhibits a series of fringe-like
processes.
The apex of the tongue, part of the inferior surface, the sides, and dorsum are
free.
The Dorsum of the Tongue (dorsum linguce) (Fig. 1014) is convex and marked by
a median sulcus, which divides it into symmetrical halves; this sulcus ends behind,
about 2.5 cm. from the root of the organ, in a depression, the foramen cecum,
from which a shallow groove, the sulcus terminalis, runs lateralward and forward
on either side to the margin of the tongue. The part of the dorsum of the tongue
in front of this groove, forming about two-thirds of its surface, looks upward, and
is rough and covered with papillae; the posterior third looks backward, and is
1126
SPLANCHNOLOGY
smoother, and contains numerous muciparous glands and lymph follicles (lingual
tonsil). The foramen cecum is the remains of the upper part of the thyroglossal
duct or diverticulum from which the thyroid gland is developed; the pyramidal
lobe of the thyroid gland indicates the position of the lower part of the duct.
The Papillae of the Tongue (Fig. 1014) are projections of the corium. They are
thickly distributed over the anterior two-thirds of its dorsum, giving to this surface
its characteristic roughness. The varieties of papillae met with are the papillae
vallatse, papillae fungiformes, papillae filiformes, antl papillae simplices.
Anterior lingual gland
Lingual nerve
Art. profunda linguae
Vena com, n. hypoglossi ^llj
Longitudinalis inferior
Plica fimbriata
B Vena com. n hypoglossi
Orifice of suhmax. dad
I Plica sublingualis
Fia. 1013.-
-The mouth cavity. The apex of the tongue is turned upward, and on the right side a superficial
dissection of its under surface has been made.
The papillae vallatae (circumvallate papillce) (Fig. 1015) are of large size, and vary
from eight to twelve in number. They are situated on the dorsum of the tongue
immediately in front of the foramen cecum and sulcus terminalis, forming a row
on either side; the two rows run l^ackward and medial ward, and meet in the middle
line, like the limbs of the letter V inverted. Each papilla consists of a projection
of mucous membrane from 1 to 2 mm. wide, attached to the bottom of a circular
depression of the mucous membrane; the margin of the depression is elevated to
form a wall (vallum), and between this and the papilla is a circular sulcus termed
the fossa. The papilla is shaped like a truncated cone, the smaller end being
directed downward and attached to the tongue, the broader part or base projecting
a little above the surface of the tongue and being studded with numerous small
secondary papillae and covered by stratified squamous epithelium.
The papillae fungiformes (fungiform papilloB) (Fig. 1017), more numerous than the
preceding, are found chiefly at the sides and apex, but are scattered irregularly
and sparingly over the dorsum. They are easily recognized, among the other
THE MOUTH
1127
papillae, by their large size, rounded eminences, and deep red color. They are
narrow at their attachment to the tongue, but broad and rounded at their free
extremities, and covered with secondary papillae.
Isthmus
faucivm
Fungiform papillce
Vallate papillce
Fig. 1014. — The mouth cavity. The cheeks have been slit transversely and the tongue pulled forward.
"J^^-V*
Ftg. 101.5. — Ciroumvallate papilla in vertical section, showing arrangement of the taste-buds and nerves.
The papillae filiformes (filiform or conical papillcB) (Fig. 1016) cover the anterior
two-thirds of the dorsum. They are very minute, filiform in shape, and arranged
1128
SPLANCHNOLOGY
in lines parallel with the two rows of the papillae vallatje, excepting at the apex
of the organ, where their direction is transverse. Projecting from their apices
are numerous filamentous processes, or secondary papillte; these are of a whitish
tint, owing to the thickness and density of the epithelium of which they are
composed, which has here undergone a peculiar modification, the cells having be-
Secondari/
papilloe
Artery ^ 7^ y^in
Fig. 1016. — A filiform papilla. JMagnified
Fig. 1017. — Section of a fungiform papilla. Magnified.
come cornified and elongated into dense, imbricated, brush-like processes. They
contain also a number of elastic fibers, which render them firmer and more elastic
than the papillae of mucous membrane generally. The larger and longer papillae
of this group are sometimes termed papillae conicae.
Fig. lOlS. — Semidiagrammatic ^-iew of a portion of the mucous membrane of the tongue. Two fungiform papillae
are shown. On some of the filiform papillae the epithelial prolongations stand erect, in one they are spread out, and in
three they are folded in.
The papillae simplices are similar to those of the skin, and cover the whole of
the mucous membrane of the tongue, as well as the larger papillae. They consist
of closely set microscopic elevations of the corium, each containing a capillary
loop, covered by a layer of epithelium.
Muscles of the Tongue. — The tongue is divided into lateral halves by a median
fibrous septum which extends throughout its entire length and is fixed below to the
THE MOUTH
1129
hyoid bone. In either half there are two sets of muscles, extrinsic and intrinsic;
the former have their origins outside the tongue, the latter are contained entirely
witliin it.
The extrinsic muscles (Fig. 1019) are:
Genioglossus. Chondroglossus.
Ilyoglossus. Styloglossus.
Glossopalatinus.'
Fig. 1019. — Extrinsic muscles of the tongue. Left side.
The Genioglossus {Gcniohyoghssus) is a flat triangular muscle close to and par-
allel with the median plane, its apex corresponding with its point of origin from the
mandible, its base with its insertion into the tongue and hyoid bone. It arises
by a short tendon from the superior mental spine on the inner surface of the sym-
physis menti, immediately above the Geniohyoideus, and from this point spreads
out in a fan-like form. The inferior fibers extend downward, to be attached by a
thin aponeurosis to the upper part of the body of the hyoid bone, a few passing
between the Hyoglossus and Chondroglossus to blend with the Constrictores
pharyngis; the middle fibers pass backward, and the superior ones upward and for-
ward, to enter the whole length of the under surface of the tongue, from the root
to the apex. The muscles of opposite sides are separated at their insertions by the
median fibrous septum of the tongue; in front, they are more or less blended owing
to the decussation of fasciculi in the median plane.
The Hyoglossus, thin and quadrilateral, arises from the side of the body and
from the whole length of the greater cornu of the hyoid bone, and passes almost
vertically upward to enter the side of the tongue, between the Styloglossus and
Longitudinalis inferior. The fibers arising from the body of the hyoid bone overlap
those from the greater cornu.
1 The Glossopalatinus (Palatoglossus) , although one of the muscles of the tongue, is mc-9 closely associated with the
soft palate both in situation and function: it has consequently been described with the muscles of that structure
(p. 1139).
1130
SPLANCHNOLOGY
The Chondroglossus is sometimes described as a part of the Hyoglossus, but is
separated from it by fibers of the Genioglossus, which pass to the side of the
pharynx. It is about 2 cm. long, and arises from the medial side and base of the
lesser cornu and contiguous portion of the body of the hyoid bone, and passes
directly upward to blend with the intrinsic muscular fibers of the tongue, between
the Hyoglossus and Genioglossus.
A small slip of muscular fibers is occasionally found, arising from the cartilago
triticea in the lateral hyothyroid ligament and entering the tongue with the hinder-
most fibers of the Hyoglossus.
The Styloglossus, the shortest and smallest of the three styloid muscles, arises
from the anterior and lateral surfaces of the styloid process, near its apex, and
from the stylomandibular ligament. Passing downward and forward between the
internal and external carotid arteries, it divides upon the side of the tongue
into two portions: one, longitudinal, enters the side of the tongue near its
dorsal surface, blending with the fibers of the Longitudinalis inferior in front of
the Hyoglossus; the other, oblique, overlaps the Hyoglossus and decussates with
its fibers.
The intrinsic muscles (Fig. 1020) are:
Longitudinalis superior.
Longitudinalis inferior.
Transversus.
Verticalis.
The Longitudinalis linguae superior {Superior lingualis) is a thin stratum of oblique
and longitudinal fibers immediately underlying the mucous membrane on the
dorsum of the tongue. It arises from the submucous fibrous layer close to the
epiglottis and from the median fibrous septujm, and runs forward to the edges
of the tongue.
Longitudina- PapillcE
lis superior oftongv£
,0J^" '-X »
Insertion of Transversus.
Styloglossus
Hyoglossus
Longitudinalis inferior
Lingual artery {'^Aj^Ay ''i
Vertical fibers of Genio-
glossus intersecting
Transversus
Septum
Fig. 1020. — Coronal section of tongue, showing intrinsic muscles. (Altered from Krause.)
The Longitudinalis linguae inferior {Inferior lingualis) is a narrow band situated
on the under surface of the tongue between the Genioglossus and Hyoglossus.
It extends from the root to the apex of the tongue: behind, some of its fibers are
connected with the bodv of the hvoid bone ; in f r6nt it blends with the fibers of
the Stvloglossus.
The Transversus linguae ( Transverse lingualis) consists of fibers which arise from
the median fibrous septum and pass lateralward to be inserted into the submucous
fibrous tissue at the sides of the tongue.
THE MOUTH 1131
The Verticalis linguae (Vertical lingimlis) is found only at the borders of the fore-
part of the tongue. Its fibers extend from the upper to the under surface of the
organ.
The median fibrous septum of the tongue is very complete, so that the anastomosis between
the two lingual arteries is not very free.
Nerves. — ^The muscles of the tongue described above are supplied by the hypoglossal nerve.
Actions. — The movements of the tongue, altliough numerous and complicated, may be under-
stood by carefully considering the direction of the fibers of its muscles. The Genioglossi, by means
of their posterior fibers, draw the root of the tongue forward, and protrude the apex from the
mouth. The anterior fibers draw the tongue back into the mouth. The two muscles acting in
their entirety draw the tongue downward, so as to make its superior surface concave from side
to side, forming a channel along which fluids may pass toward the pharynx, as in sucking. The
Hyoglossi depress the tongue, and draw down its sides. The Styloglossi draw the tongue upward
and backward. The Glossopalatini draw the root of the tongue upward. The intrinsic muscles
are mainly concerned in altering the shape of the tongue, whereby it becomes shortened, nar-
rowed, or curved in different directions; thus, the Longitudinalis superior and inferior tend to
shorten the tongue, but the former, in addition, turn the tip and sides upward so as to render
the dorsum concave, while the latter pull the tip downward and render the dorsum convex.
The Transversus narrows and elongates the tongue, and the Verticalis flattens and broadens it.
The complex arrangement of the muscular fibers of the tongue, and the various directions in
which they run, give to this organ the power of assuming the forms necessary for the enuncia-
tion of the different consonantal sounds; and Macahster states "there is reason to believe that
the musculature of the tongue varies in different races owing to the hereditary practice and
habitual use of certain motions required for enunciating the several vernacular languages."
Structure of the Tongue. — The tongue is partly invested by mucous membrane and a sub-
mucous fibrous layer.
The mucous membrane {tunica mucosa lingua) differs in different parts. That covering the
under surface of the organ is thin, smooth, and identical in structure with that lining the rest
of the oral cavity. The mucous membrane of the dorsum of the tongue behind the foramen
cecum and sulcus terminalis is thick and freely movable over the subjacent parts. It contains
a large number of lymphoid follicles, which together constitute what is sometimes termed the
lingual tonsil. Each follicle forms a rounded eminence, the center of which is perforated by a
minute orifice leading into a funnel-shaped cavity or recess; around this recess are grouped
numerous oval or rounded nodules of lymphoid tissue, each enveloped by a capsule derived from
the submucosa, while opening into the bottom of the recesses are also seen the ducts of mucous
glands. The mucous membrane on the anterior part of the dorsum of the tongue is thin, inti-
mately adherent to the muscular tissue, and presents numerous minute surface eminences, the
papillae of the tongue. It consists of a layer of connective tissue, the cerium or mucosa, covered
with epithelium.
The epithelium is of the stratified squamous variety, similar to but much thinner than that
of the skin: and each papilla has a separate investment from root to summit. The deepest cells
may sometimes be detached as a separate layer, corresponding to the rete mucosum, but they
never contain coloring matter.
The cerium consists of a dense felt-work of fibrous connective tissue, with numerous elastic
fibers, firmly connected with the fibrous tissue forming the septa between the muscular bundles
of the tongue. It contains the ramifications of the numerous vessels and nerves from which
the papillae are supplied, large plexuses of lymphatic vessels, and the glands of the tongue.
Structure of the Papillce. — The papillae apparently resemble in structure those of the cutis,
consisting of cone-shaped projections of connective tissue, covered with a thick layer of stratified
squamous epithelium, and containing one or more capillary loops among which nerves are dis-
tributed in great abundance. If the epithelium be removed, it will be found that they are not
simple elevations Uke the papillae of the skin, for the surface of each is studded with minute
conical processes which form secondary papillaj. In the papilla^ vallate, the nerves are numer-
ous and of large size; in the papillae fungiformes they are also numerous, and end in a plexiform
net-work, from which brush-like branches proceed; in the papillae filiformes, their mode of
termination is uncertain.
Glands of the Tongue. — The tongue is provided with mucous and serous glands.
The mucous glands are similar in structure to the labial and buccal glands. They are found
especially at the back part behind the vallate papillae, but are also present at the apex and mar-
ginal parts. In this connection the anterior lingual glands (Blandin or Nuhn) require special
notice. They are situated on the under surface of the apex of the tongue (Fig. 1013), one on either
side of the frenulum, where they are covered by a fasciculus of muscular fibers derived from the
Styloglossus and Longitudinalis inferior. They are from 12 to 25 mm. long, and about 8 mm.
broad, and each opens by three or four ducts on the under surface of the apex.
The serous glands occur only at the back of the tongue in the neighborhood of the taste-buds,
1132
SPLANCHNOLOGY
their ducts opening for the most part into the fossae of the vallate papillae. These glands are
racemose, the duct of each branching into several minute ducts, which end in alveoh, lined by
a single layer of more or less columnar epithelium. Their secretion is of a watery nature, and
probably assists in the distribution of the substaince to be tasted over the taste area. (Ebner.)
The septum consists of a vertical layer of fibrous tissue, extending throughout the entire
length of the median plane of the tongue, though not quite reaching the dorsum. It is thicker
behind than in front, and occasionally contains a small fibrocartilage, about 6 mm. in length.
It is well displayed by making a vertical section across the organ.
The hyoglossal membrane is a strong fibrous lamina, which connects the under surface of
the root of the tongue to the body of the hyoid bone. This membrane receives, in front, some
of the fibers of the Genioglossi.
Taste-buds, the end-organs of the gustatory sense, are scattered over the mucous membrane
of the mouth and tongue at irregular intervals. They occur especially in the sides of the vallate
papillae. In the rabbit there is a localized area at the side of the base of the tongue, the papilla
foliata, in which they are especially abundant (Fig. 1021). They are described under the organs
of the senses (page 991).
Central lamina of — r , .^
corium //>•?
Lateral lamina in which "J^,-
Sinus-like vein travers-_rrjr_^._ ,
ing whole length of ,-^J_-':--
folium
Nerve bundles -35
gland
Fig. 1021. — Vertical section of papilla foliata of the rabbit, passing across the folia. (Ranvier.)
Vessels and Nerves. — The main artery of the tongue is the lingual branch of the external
carotid, but tlie external maxillary and ascending pharyngeal also give branches to it. The
veins open into the internal jugular.
The lymphatics of the tongue have been described on page 696.
The sensory nerves of the tongue are: (1) the lingual branch of the mandibular, which is
distributed to the papilla; at the forepart and sides of the tongue, and forms the nerve of ordinary
sensibility for its anterior two-thirds; (2) the chorda tympani branch of the facial, which runs
in the sheath of the lingual, and is generally regarded as the nerve of taste for the anterior two-
thirds; this nerve is a continuation of the sensory root of the facial {nervus intermedius) ; (3) the
Ungual branch of the glossopharyngeal, which is distributed to the mucous membrane at the
base and sides of the tongue, and to the papilke vallatse, and which supplies both gustatory
filaments and fibers of general sensation to this region; (4) the superior laryngeal, which sends
some fine branches to the root near the epiglottis.
The Salivary Glands (Fig. 1024). — Three large pairs of sahvary glands communi-
cate with the mouth, and pour their secretion into its cavity; they are the parotid,
submaxillary, and sublingual.
Parotid Gland {glandula parotis). — The parotid gland (Figs. 1022, 1023), the largest
of the three, varies in weight from 14 to 28 gm. It lies upon the side of the face,
immediately below and in front of the external ear. The main portion of the gland
is superficial, somewhat flattened and quadrilateral in form, and is placed between
the ramus of the mandible in front and the mastoid process and Sternocleido-
mastoideus behind, overlapping, however, both boundaries. Above, it is broad
and reaches nearly to the zygomatic arch; below, it tapers somewhat to about
THE MOUTH
1133
the level of a line joining the tip of the mastoid process to the angle of the mandible.
The remainder of the" gland is irregularly wedge-shaped, and extends deeply
inward toward the pharyngeal wall.
Superficial temporal art.
Impression for ext. acoustic
meatus
Portion in front of styloid -procetn
Impression for styloid process
Ext. carotid
Portion behind styloid process
Impression for mastoid pro-
cess and Sternocleidomas-
toideus
Impression for Digastricus
Posterior facial
Fig. 1.022. — Right parotid gland. Posterior and deep aspects.
The gland is enclosed within a capsule continuous with the deep cervical fascia;
the layer covering the superficial surface is dense and closely adherent to the
gland; a portion of the fascia, attached to the styloid process and the angle of the
mandible, is thickened to form the stylomandibular ligament which intervenes
between the parotid and submaxillary glands.
Parotid duct
Superfic. temp, artery
Int. mMx. artery
Portion in front cf styloid
process
Portion behind styloid
process
Imjyression for styloid
process
Impression for rnandible
External carotid artery
Posterior facial vein
Fig. 1023. — Right parotid gland. Deep and anterior aspects.
The anterior surface of the gland is moulded on the posterior border of the
ramus of the mandible, clothed by the Pterygoideus internus and ]Masseter. The
inner lip of the groove dips, for a short distance, between the two Pterygoid muscles,
1134 SPLANCHNOLOGY
while the outer lip extends for some distance over the superficial surface of the
Masseter; a small portion of this lip immediately below the zygomatic arch is
usually detached, and is named the accessory part {socia yarotidis) of the gland.
The posterior surface is grooved longitudinally and abuts against the external
acoustic meatus, the mastoid process, and the anterior border of the Sterno-
cleidomastoideus.
The superficial surface, slightly lobulated, is covered by the integument, the
superficial fascia containing the facial branches of the great auricular nerve and
some small lymph glands, and the fascia which forms the capsule of the gland.
The deep surface extends inward by means of two processes, one of which lies
on the Digastricus, styloid process, and the styloid group of muscles, and projects
under the mastoid process and Sternocleidomastoideus; the other is situated in
front of the styloid process, and sometimes passes into the posterior part of the
mandibular fossa behind the temporomandibular joint. The deep surface is in
contact with the internal and external carotid arteries, the internal jugular vein,
and the vagus and glossopharyngeal nerves.
The gland is separated from the pharyngeal wall by some loose connective
tissue.
Structures within the Gland. — The external carotid artery lies at first on the deep
surface, and then in the substance of the gland. The artery gives off its 'posterior
auricular branch which emerges from the gland behind; it then divides into its
terminal branches, the internal maxillary and superficial teinporal; the former runs
forward deep to the neck of the mandible; the latter runs upward across the zygo-
matic arch and gives off its transverse facial branch which emerges from the front
of the gland. Superficial to the arteries are the superficial temporal and internal
maxillary vehis, uniting to form the posterior facial vein; in the lower part of the
gland this vein splits into anterior and posterior divisions. The anterior division
emerges from the gland and unites with the anterior facial to form the common
facial vein; the posterior unites in the gland with the posterior auricular to form
the external jugular vein. On a still more superficial plane is the facial nerve, the
branches of which emerge from the borders of the gland. Branches of the great
auricular nerve pierce the gland to join the facial, while the auriculotemporal nerve
issues from the upper part of the gland.
The parotid duct {ductus parotideus; Stensen's duct) is about 7 cm. long. It
begins by numerous branches from the anterior part of the gland, crosses the ]\lasse-
ter, and at the anterior border of this muscle turns inward nearly at a right angle,
passes through the corpus adiposum of the cheek and pierces the Buccinator; it
then runs for a short distance obliquely forward between the Buccinator and mucous
membrane of the mouth, and opens upon the oral surface of the cheek by a small
orifice, opposite the second upper molar tooth. While crossing the Masseter,
it receives the duct of the accessory portion; in this position it lies between the
branches of the facial nerve; the accessory part of the gland and the transverse
facial artery are above it.
Structure. — ^The parotid duct is dense, its wall being of considerable thickness; its canal is
about the size of a crow-quill, but at its orifice on the oral surface of the cheek its lumen is
greatly reduced in size. It consists of a thick external fibrous coat which contains contractile
fibers, and of an internal or mucous coat lined with short columnar epithehum.
Vessels and Nerves. — The arteries supplying the parotid gland are derived from the external
carotid, and from the branches given off by that vessel in or near its substance. The veins
empty themselves into the external jugular, through some of its tributaries. The lymphatics
end in the superficial and deep cervical lymph glands, passing in their course through two or
three glands, placed on the surface and in the substance of the parotid. The nerves are derived
from the plexus of the sympathetic on the external carotid artery, the facial, the auriculotem-
poral, and the great auricular nerves. It is probable that the branch from the auriculotemporal
nerve is derived from the glossopharyngeal through the otic gangUon. At all events, in some of
the lower animals this has been proved experimentally to be the case.
THE MOUTH
1135
Submaxillary Gland {glandula suhmaxillaris) . — The submaxillary gland (Ing.
1024) is irregular in form and about the size of a walnut. A considerable part of
it is situated in the submaxillary triangle, reaching forward to the anterior belly
of the Digastricus and backward to the stylomandil)ular ligament, which inter-
venes between it and the parotid gland. Above, it extends under cover of the
body of the mandible; below, it usually overlaps the intermediate tendon of
the Digastricus and the insertion of the Stylohyoideus, while from its deep surface
a tongue-like deep process extends forward above the Mylohyoideus muscle.
Its superficial surface consists of an upper and a lower i)art. The upper part
is directed outward, and lies partly against the submaxillary depression on the
inner surface of the body of the m.andible, and partly on the Pterygoideus internus.
The lower part is directed downward and outward, and is covered by the skin,
superficial fascia, Platysma, and deep cervical fascia; it is crossed by the anterior
facial vein and by filaments of the facial nerve ; in contact with it, near the mandible,
are the submaxillary lymph glands.
■^Opening of parotid
duct
Suhmaxillary duct
Anterior facial vein
Fig. 1024. — Dissection, showins salivarj'' glands of right side.
The deep surface is in relation with the Mylohyoideus, Hyoglossus, Styloglossus,
Stylohyoideus, and posterior belly of the Digastricus; in contact with it are the
mvlohvoid nerve and the mvloh\-oid and submental vessels.
The external maxillary artery is imbedded in a groove in the posterior border
of the gland.
The deep process of the gland extends forward between the ^Mylohyoideus
below and externally, and the Hyoglossus and Styloglossus internally; above
it is the lingual nerve and submaxillary ganglion; below it the hypoglossal nerve
and its accompanying vein.
The submaxillary duct (ductus submaxillar is; JVharton's duct) is about 5 cm. long,
r.nd its wall is much thinner than that of the parotid duct. It begins by numerous
1136 SPLAXCHXOLOGY
branches from the deep surface of the gland, and runs forward between the ]\Iylo-
hyoideus and the Hyoglossus and Genioglossus, then between the subHngual
gland and the Genioglossus, and opens by a narrow orifice on the summit of a small
papilla, at the side of the frenulum linguce. On the Hyoglossus it lies between the
lingual and hypoglossal nerves, but at the anterior border of the muscle it is crossed
laterally by the lingual nerve; the terminal branches of the lingual nerve ascend
on its medial side.
Vessels and 'Nerves. — The arteries supplying the submaxillary gland are branches of the
external maxillarj^ and lingual. Its veins follow the course of the arteries. The nerves are
derived from the submaxillary ganglion, through which it receives filaments from the chorda
tympani of the facial nerve and the lingual branch of the mandibular, sometimes from the
mylohyoid branch of the inferior alveolar, and from the sjTnpathetic.
Sublingual Gland {glandnla sublingualis). — The sublingual gland (Fig. 1024) is the
smallest of the three glands. It is situated beneath the mucous membrane of
the floor of the mouth, at the side of the frenulum linguie, in contact with the
sublingual depression on the inner surface of the mandible, close to the symphysis.
It is narrow, flattened, shaped somewhat like an almond, and weighs nearly 2 gm.
It is in relation, above, with the mucous membrane; below, with the iMylohyoideus;
behind, with the deep part of the submaxillary gland; laterally, with the mandible;
and medially, with the Genioglossus, from which it is separated by the lingual nerve
and the submaxillary duct. Its excretory ducts are from eight to twenty in
number. Of the smaller sublingual ducts (ducts of Rivimis), some join the sub-
maxillary duct; others open separately into the mouth, on the elevated crest of
mucous membrane {plica sublingualis) , caused by the projection of the gland, on
either side of the frenulum lingua?. One or more join to form the larger sublingual
duct {diict of Bartholin) , which opens into the submaxillary duct.
Vessels and Nerves. — The subhngual gland is supphed with blood from the sublingual and
submental arteries. ' Its nerves are derived from the lingual, the chorda tympani, and the
sympathetic.
Structure of the Salivary Glands. — The saUvary glands are compound racemose glands,
consisting of numerous lobes, which are made up of smaller lobules, connected together by
dense areolar, tissue, vessels, and ducts. Each lobule consists of the ramifications of a single
duct, the branches ending in dilated ends or alveoh on which the capillaries are distributed.
The alveoli are enclosed by a basement membrane, which is continuous with the membrana
propria of the duct and consists of a net-work of branched and flattened nucleated cells.
The alveoli of the salivary glands are of two kinds, which differ in the appearance of their
secreting cells, in their size, and in the nature of their secretion. (1) The mucous variety secretes
a viscid fluid, which contains mucin; (2) the serous variety secretes a thinner and more watery
fluid. The subhngual gland consists of mucous, the parotid of serous alveoli. The submaxillary
contains both mucous and serous alveoli, the latter, however, preponderating.
The cells in the mucous alveoli are columnar in shape. In the fresh condition thej'^ contain
large granules of mucinogen. In hardened preparations a dehcate protoplasmic net-work is seen,
and the cells are clear and transparent. The nucleus is usually situated near the basement
membrane, and is flattened.
In some alveoli are seen pecuhar crescentic bodies, lying between the cells and the mem-
brana propria. They are termed the crescents of Gianuzzi, or the demilunes of Heidenhain
(Fig. 1025), and are composed of polyhedral granular cells, which Heidenhain regards as young
epithelial cells destined to supply the place of those salivarj- cells which have undergone
disintegration. This view, however, is not accepted by Klein. Fine canahculi pass between
the mucus-secreting cells to reach the demilunes and even penetrate the cells forming these
structures.
In the serous alveoli the cells almost completely fill the cavity, so that there is hardly any
lumen perceptible; they contain secretory granules imbedded in a closely reticulated protoplasm
(Fig. 1026). The cells are more cubical than those of the mucous type; the nucleus of each is
spherical and placed near the center of the ceU, and the granules are smaller.
Both mucous and serous cells vary in appearance according to whether the gland is in a resting
•condition or has been recently active. In the former case the cells are large and contain many
secretory granules; in the latter case thej' are shrunken and contain few granules, chiefly collected
.at the inner ends of the cells. The granules are best seen in fresh preparations.
THE FAUCES
1137
A J/rp*!w ^'V'"'''^ 't^ ^^^^'.^o^ipns by epitheUum which differs httle from the pavement form,
nfvt t J h l^^' u ^P'^h^^'^^^ ^«"s change to the columnar type, and the part of the cell
next the basement membrane is finely striated.
npf^wnit^^^^t "*• V'"" ^?'^'?'^' ^''""^' '"'^ "'^^'y supplied with bloodvessels which form a dense
ti«2 Ti? "itenUveolar spaces. Fine plexuses of nerves are also found in the interlobular
vZ^L. fi^frrfI7^ . P'r"" *^^ basement membrane of the alveoli, and end in branched
IcouZiluZT" T" '^'^ ?'/''•"" '^'"'- ^" ^^^« ^^""^ °^ ^^« submaxillary gland there is
a collection of nerve cells termed Langley's ganglion.
Demilune
Fig. 1025. — Section of submaxillarj- gland of kitten. Duct Fig. 1026. — Human subma.\illary gland. (R. Hei-
semidiagraininatic. X 200. denhain.) At the right is a group of mucous alveoli,
at the left a group of serous alveoli.
Accessory Glands. — Besides the salivary glands proper, numerous other glands are found
in the mouth. Many of these glands are found at the posterior part of the dorsum of the tongue
behind the vallate papillae, and also along its margins as far forward as the apex. Others lie
around and in the palatine tonsil between its crypts, and large numbers are present in the soft
palate, the lips, and cheeks. These glands are of the same structure as the larger salivary glands,
and are of the mucous or mixed type.
THE FAUCES.
The aperture by which the mouth communicates with the pharynx is called
the isthmus f aucium. It is bounded, above, by the soft palate ; below, by the dorsum
of the tongue; and on either side, by the glossopalatine arch.
The glossopalatine arch {arciis glossopalatinns ; anterior pillar of fauces) on either
side runs downward, lateralward, and forward to the side of the base of the tongue,
and is formed by the projection of the Glossopalatinus with its covering mucous
membrane.
The pharsmgopalatine arch {arcus pharyngopalatimts; posterior pillar of fauces) is
larger and projects farther toward the middle line than the anterior; it runs down-
ward, lateralward, and backward to the side of the pharynx, and is formed by the
projection of the Pharyngopalatinus, covered by mucous membrane. On either side
the two arches are separated below by a triangular interval, in Avhich the palatine
tonsil is lodged.
The Palatine Tonsils (tonsillcp palatinoe; tonsil) are two prominent masses situated
one on either side between the glossopalatine and pharyngopalatine arches. Each
tonsil consists fundamentally of an aggregation of lymphoid tissue underlying
the mucous membrane between the palatine arches. The lymphoid mass, however,
72
1138 SPLANCHNOLOGY
does not completely fill the interval between the two arches, so that a small depres-
sion, the supratonsillar fossa, exists at the upper part of the interval. Further,
the tonsil extends for a variable distance under cover of the glossopalatine arch,
and is here covered by a reduplication of mucous membrane; the upper part of this
fold reaches across the supratonsillar fossa, between the two arches, as a thin
fold sometimes termed the plica semilunaris ; the remainder of the fold is called the
plica triangularis. Between the plica triangularis and the surface of the tonsil is
a space known as the tonsillar sinus; in many cases, however, this sinus is obliterated
by its walls becoming adherent. From this description it will be apparent that a
portion of the tonsil is below the level of the surrounding mucous membrane, i. e., is
imbedded, while the remainder projects as the visible tonsil. In the child the
tonsils are relatively (and frequently absolutely) larger than in the adult, and about
one-third of the tonsil is imbedded. After puberty the imbedded portion diminishes
considerably in size and the tonsil assumes a disk-like form, flattened from side
to side; the shape and size of the tonsil, however, vary considerably in different
individuals.
y'f''' i • •*■ r-'- it' -^
sf
Fig. 1027. — Section through one of the crypts of the tonsil. (Stohr.) Magnified. ?. Stratified epithelium of general
surface, continued into crypt. /, /. Nodules of lymphoid tissue — opposite each nodule numbers of lymph cells are
passing into or through the epithelium, s, s. Cells whicli have thus escaped to mix with the saliva as salivary corpuscles.
The medial surface of the tonsil is free except anteriorly, where it is covered by
the plica triangularis; it presents from twelve to fifteen orifices leading into small
crypts or recesses from which numerous follicles branch out into the tonsillar
substance.
The lateral or deep surface is adherent to a fibrous capsule which is continued
into the plica triangularis. It is separated from the inner surface of the Constrictor
pharyngis superior usually by some loose connective tissue; this muscle intervenes
between the tonsil and the external maxillary artery with its tonsillar and ascend-
ing palatine branches. The internal carotid artery lies behind and lateral to the
tonsil at a distance of 20 to 25 mm. from it.
The tonsils form part of a circular band of adenoid tissue which guards the
opening into the. digestive and respiratory tubes. The anterior part of the ring
is formed by the submucous adenoid collections (lingual tonsil) on the posterior
part of the tongue; the lateral portions consist of the palatine tonsils and the ade-
THE FAUCES 1139
noid collections in the vicinity of the auditory tubes, while the ring is completed
behind by the pharyngeal tonsil on the posterior wall of the pharynx. In the
intervals between these main masses are smaller collections of adenoid tissue.
Structure (Fig. 1027). — The follicles of the tonsil are lined by a continuation of the mucous
membrane of the pharynx, covered with stratified squamous epithehum; around each follicle
is a layer of closed capsules consisting of lymphoid tissue imbedded in the subnuicous tissue.
Lymph corpuscles are found in large numbers invading the stratified epithelium. It is probable
that they pass into the mouth and form the so-called salivary corpuscles. Surrounding each
follicle is a close plexus of lym()hatics, from which the lymphatic vessels pass to the deep cervical
glands in the neighborhood of the greater cornu of the hyoid bone, behind and below the angle
of the mandible.
Vessels and Nerves. — The arteries suj)plying the tonsil are the dorsalis lingua; from the
lingual, the ascending palatine and tonsillar from the external maxillary, the ascending pharyn-
geal from the external carotid, the descending palatine branch of the internal maxillary, and a
twig from the small meningeal.
The veins end in the tonsillar plexus, on the lateral side of the tonsil.
The nerves are derived from the sphenopalatine ganghon, and from the glossopharjmgeal.
Palatine Aponeurosis. — Attached to the posterior border of the hard palate is
a thin, firm fibrous lamella which supports the muscles and gives strength to the
soft palate. It is thicker above than below, where it becomes very thin and difficult
to define. Laterally it is continuous with the pharyngeal aponeurosis.
Muscles of the Palate. — The muscles of the palate (Fig. 1028) are:
Levator veli palatini. Glossopalatinus.
Tensor veli palatini. Pharyngopalatinus.
Musculus uvulae.
The Levator veli palatini {Levator jxilati) is a thick, rounded muscle situated
lateral to the choanae. It arises from the under surface of the apex of the petrous
part of the temporal bone and from the medial lamina of the cartilage of the audi-
tory tube. After passing above the upper concave margin of the Constrictor
pharyngis superior it spreads out in the palatine velum, its fibers extending
obliquely downward and medialward to the middle line, where they blend with
those of the opposite side.
The Tensor veli palatini {Tensor 2^oioti) is a broad, thin, ribbon-like muscle
placed lateral to the Levator veli palatini. It arises by a flat lamella from the
scaphoid fossa at the base of the medial pterygoid plate, from the spina angularis
of the sphenoid and from the lateral wall of the cartilage of the auditory tube.
Descending vertically between the medial pterygoid plate and the Pterygoideus
internus it ends in a tendon which winds around the pterygoid hamulus, being
retained in this situation by some of the fibers of origin of the Pterygoideus internus.
Between the tendon and the hamulus is a small bursa. The tendon then passes
medialward and is inserted into the palatine aponeurosis and into the surface
behind the transverse ridge on the horizontal part of the palatine bone.
The Musculus uvulae (Azygos nvnlw) arises from the posterior nasal spine of
the palatine bones and from the palatine aponeurosis; it descends to be inserted
into the uvula.
The Glossopalatinus {Palatoglossus) is a small fleshy fasciculus, narrower in
the middle than at either end, forming, with the mucous membrane covering
its surface, the glossopalatine arch. It arises from the anterior surface of the
soft palate, where it is continuous with the muscle of the opposite side, and passing
downward, forward, and lateralward in front of the palatine tonsil, is inserted
into the side of the tongue, some of its fibers spreading over the dorsum, and
others passing deeply into the substance of the organ to intermingle with the
Transversus linguie.
The Pharyngopalatinus {Palatopharyngetis) is a long, fleshy fasciculus narrower
in the middle than at either end, forming, with the mucous membrane covering
1140
SPLANCHNOLOGY
its surface, the pharyngopalatine arch. It is separated from the Glossopalatinus
by an angular interval, in which the palatine tonsil is lodged. It arises from the
soft palate, where it is divided into two fasciculi by the Levator veli palatini and
Musculus uvula\ The posterior fasciculus lies in contact with the mucous mem-
brane, and joins with that of the opposite muscle in the middle line; the anterior
fasciculus, the thicker, lies in the soft palate between the Levator and Tensor,
and joins in the middle line the corresponding part of the opposite muscle. Passing
lateralward and downward behind the palatine tonsil, the Pharyngopalatinus
joins the Stylopharyngeus, and is inserted with that muscle into the posterior
border of the thyroid cartilage, some of its fibers being lost on the side of the
pharynx and others passing across the middle line posteriorly, to decussate with
the muscle of the opposite side.
Styloid process
Levator vcli
palatini
I Pterygoid liamulxis
— Stylopharynge us
Salpingopharyngeus
Muscvlus uvulce
Entrance to larynx
Fig. 102S. — Dissection of the muscles of the palate from behind.
Nerves. — The Tensor veli palatini is supplied by a branch from the otic ganglion; the remain-
ing muscles of this group are in all probability supplied by the accessory nerve through the
pharyngeal plexus.'
Actions.— During the first stage of deglutition, the bolus of food is driven back into the fauces
by the pressure of the tongue against the hard palate, the base of the tongue being, at the same
time, retracted, and the larynx raised with the pharynx. During the second stage the entrance
to the larynx is closed by the drawing forward of the arytenoid cartilages toward the cushion
•"The Innervation of the Soft Palate," by Aldren Turner, Journal of Anatomy and Physiology, xxiii, 523.
THE PHARYNX 1141
ot the epiglottis — a movement produced b}- the contraction of the Thyreoarytaenoidei, the
Arytaenoidei, and the Aryta^noepiglottidei.
After leaving the tongue the bolus passes on to the posterior or laryngeal surface of the epi-
glottis, and glides along this for a certain distance; then the Glossopalatini, the constrictors of
the fauces, contract behind it; the palatine velum is slightly raised by the Levator veli palatini,
and made tense by the Tensor veli palatini; and the Pharyngopalatini, by their contraction,
pull the pharynx upward over the bolus, ana come nearly together, the uvula filling up the
slight interval between them. By these means the food is prevented from passing into the nasal
part of the pharynx; at the same time, the Pharyngopalatini form an inchned plane, directed
obliquely downward and backward along the under sm-face of which the bolus descends into
the lower part of the pharynx. The Salpingopharyngei raise the upper and lateral parts of the
pharynx — i. e., those parts which are above the points where the Stylopharyngei are attached
to the pharynx.
Mucous Membrane. — The mucous membrane of the soft palate is thin, and covered with strati-
fied .squamous epithelium on both surfaces, excepting near the pharyngeal ostium of the auditory
tube, where it is columnar and ciliated. According to Klein, the mucous membrane on the
nasal surface of the soft palate in the fetus is covered throughout by columnar ciliated epithelium,
which subsequently becomes squamous; some anatomists state that it is covered with columnar
ciliated epithelium, except at its free margin, throughout life. Beneath the mucous membrane
on the oral surface of the soft palate is a considerable amount of adenoid tissue. The palatine
glands form a continuous layer on its posterior surface and around the uvula.
Vessels and Nerves. — The arteries sj.ipplying the palate are the descending palatine branch
of the internal maxillary, the a.«cending palatine branch of the external maxillary, and the pala-
tine branch of the ascending pharyngeal. The veins end chiefly in the pterygoid and tonsillar
plexuses. The lymphatic vessels pass to the deep cervical glands. The sensory nerves are
derived from the palatine and nasopalatine nerves and from the glossopharyngeal.
THE PHARYNX.
The pharynx is that part of the digestive tube which is placed behind the nasal
cavities, mouth, and larynx. It is a musculomembranous tube, somewhat conical
in form, with the base upward, and the apex downward, extending from the under
surface of the skull to the level of the cricoid cartilage in front, and that of the
sixth cervical vertebra behind.
The cavity of the phannx is about 12.5 cm. long, and broader in the transverse
than in the antero-posterior diameter. Its greatest breadth is immediately^ below
the base of the skull, where it projects on either side, behind the pharyngeal ostium
of the auditory tube, as the pharyngeal recess (fossa of Rosenmilller) ; its narrowest
point is at its termination in the esophagus. It is limited, above, by the body
of the sphenoid and basilar part of the occipital bone; below, it is continuous with
the esophagus; posteriorly, it is connected by loose areolar tissue with the cervical
portion of the vertebral column, and the prevertebral fascia covering the Longus
colli and Longus capitis muscles; anteriorly, it is incomplete, and is attached in
succession to the medial pterygoid plate, pterygomandibular raphe, mandible,
tongue, hyoid bone, and thyroid and cricoid cartilages; laterally, it is connected to
the styloid processes and their muscles, and is in contact with the common and
internal carotid arteries, the internal jugular veins, the glossopharyngeal, vagus,
and hypoglossal nerves, and the sympathetic trunks, and above with small parts
of the Pterygoidei interni. Seven cavities communicate with it, viz., the two
nasal cavities, the two tympanic caviti,es, the mouth, the larj-nx, and the esophagus.
The cavity of the pharynx may be subdivided from above downward into three
parts: nasal, oral, and larsmgeal (Fig. 994).
The Nasal Part of the Pharynx (pars nasalis pharyngis; nasopharynx) lies behind
the nose and above the level of the soft palate : it differs from the oral and laryn-
geal parts of the pharynx in that its cavity always remains patent. In front (Fig.
1029) it communicates through the choanae with the nasal cavities. On its lateral
wall is the pharyngeal ostium of the auditory tube, somewhat triangular in shape,
and bounded behind by a firm prominence, the torus or cushion, caused by the
medial end of the cartilage of the tube which elevates the mucous membrane.
1142
SPLANCHNOLOGY
A vertical fold of mucous membrane, the salpingopharyngeal fold, stretches from
the lower part of the torus; it contains the Salpingopharyngeus muscle. A second
and smaller fold, the salpingopalatine fold, stretches from the upper part of the torus
to the palate. Behind the ostium of the auditory tube is a deep recess, the pharyn-
geal recess (fossa of RosenmiiUer) . On the posterior wall is a prominence, best
marked in childhood, produced by a mass of lymphoid tissue, which is known as the
pharyngeal tonsil. Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as far
as the basilar process of the occipital bone; it is known as the pharyngeal bursa.
Nasal septum
Nasal concha;
Pharyngeal recess
Pharyngeal ostium of
auditory tube
Fig. 1029. — Front of nasa part of pharynx, as seen with the laryngoscope.
The Oral Part of the Pharynx (pars oralis yharyngis) reaches from the soft palate
to the level of the hyoid bone. It opens anteriorly, through the isthmus faucium,
into the mouth, while in its lateral wall, between the two palatine arches, is the
palatine tonsil.
The Laryngeal Part of the Pharynx {pars laryngea pharyngis) reaches from the
hyoid bone to the lower border of the cricoid cartilage, where it is continuous with
the esophagus. In front, it presents the triangular entrance of the larynx, the base
of which is directed forward and is formed by the epiglottis, while its lateral boun-
daries are constituted by the aryepiglottic folds. On either side of the laryngeal
orifice is a recess, termed the sinus piriformis, which is bounded medially by the
aryepiglottic fold, laterally by the thyroid cartilage and hyothyroid membrane.
Muscles of the Pharynx. — The muscles of the pharynx (Fig. 1030) are:
Constrictor inferior. Stylopharyngeus.
Constrictor medius. Salpingopharyngeus.
Constrictor superior. Pharyngopalatinus.^
The Constrictor pharyngis inferior (Inferior constrictor) (Figs. 1030, 1031), the thickest
of the three constrictors, arises from the sides of the cricoid and thyroid cartilage.
From the cricoid cartilage it arises in the interval between the Cricothyreoideus
in front, and the articular facet for the inferior cornu of the thyroid cartilage
behind. On the thyroid cartilage it arises from the oblique line on the side of the
lamina, from the surface behind this nearly as far as the posterior border and from
the inferior cornu. From these origins the fibers spread backward and medialward
to be inserted with the muscle of the opposite side into the fibrous raphe in the
posterior median line of the pharynx. The inferior fibers are horizontal and con-
tinuous with the circular fibers of the esophagus; the rest ascend, increasing in
obliquity, and overlap the Constrictor medius.
' The Pharj'ngopalatinus is described with the muscles of the palate (p. 1139).
THE PHARYNX
1143
The Constrictor pharyngis medius (Middle constrictor) (Figs. 1030, 1031) is a fan-
shaped muscle, smaller than the preceding. It arises from the whole length of the
upper border of the greater cornu of the hyoid
bone, from the lesser cornu, and from the
stylohyoid ligament. The fibers diverge from
their origin : the lower ones descend beneath
the Constrictor inferior, the middle fibers
pass transversely, and the upper fibers ascend
and overlap the Constrictor superior. It is
inserted into the posterior median fibrous
raphe, blending in the middle line with the
muscle of the opposite side.
The Constrictor pharyngis superior (Superior
constrictor) (Fig. lOoO, 1031.) is a quadrilateral
muscle, thinner and paler than the other two.
It arises from the lower third of the posterior
margin of the medial pterygoid plate and its
hamulus, from the pterygomandibular raphe,
from the alveolar process of the mandible
above the posterior end of the mylohyoid line,
and by a few fibers from the side of the tongue.
The fibers curve backward to be inserted
into the median raphe, being also prolonged
by means of an aponeurosis to the pharyn-
geal spine on the basilar part of the occip-
ital bone. The superior fibers arch beneath
the Levator veli palatini and the auditory
tube. The interval between the upper
border of the muscle and the base of the
skull is closed by the pharyngeal aponeurosis, and is known as the sinus of
Morgagni.
The Stylopharyngeus (Fig. 1019) is a long, slender muscle, cylindrical above,
flattened below. It arises from the medial side of the base of the styloid process,
passes downward along the side of the pharynx between the Constrictores superior
and medius, and spreads out beneath the mucous membrane. Some of its fibers
are lost in the Constrictor muscles, while others, joining with the Pharyngopalatinus,
are inserted into the posterior border of the thyroid cartilage. The glossopharyn-
geal nerve runs on the lateral side of this muscle, and crosses over it to reach the
tongue.
The Salpingopharyngeus (Fig. 1028) arises from the inferior part of the auditory
tube near its orifice; it passes downward and blends with the posterior fasciculus
of the Pharyngopalatinus.
Nerves. — The Constrictores and Salpingopharyngeus are supphed by branches from the
pharjTigeal plexus, the Constrictor inferior by additional branches from the external laryngeal
and reettTfeftt-Tterves, and the Stylopharyngeus by the glossopharyngeal nerve.
Actions. — When d^Iutition is about to be performed, the pharjTix is dra-^Ti upward and
dilated in different directions, to receive the food propelled into it from the mouth. TheStylo-
pharj'ngei, which are much farther removed from one another at their origin than at their inser-
tion, draw the sides of the pharynx upward and lateralward, and so increase its transverse
diameter; its breadth in the antero-posterior direction is increased by the larynx and tongue
being carried forward in theu" ascent. As soon as the bolus of food is received in the pharynx,
the elevator muscles relax, the pharynx descends, and the Constrictores contract upon the
bolus, and convey it downward into the esophagus.
Structure. — The pharynx is composed of three coats: mucous, fibrous, and muscular.
The pharyngeal aponeurosis, or fibrous coat, is situated between the mucous and muscular
layers. It is thick above where the muscular fibers are wanting, and is firmly connected to the
Fig. 1030. — ^Muscles of the pharynx and cheek.
1144
SPLANCHNOLOGY
basilar portion of the occipital and the petrous portions of the temporal bones. As it descends
it diminishes in thickness, and is gradually lost. It is strengthened posteriorly by a strong fibrous
band, which is attached above to the pharyngeal spine on the under surface of the basilar portion
of the occipital bone, and passes downward, forming a median raphe, which gives attachment
to the Constrictores pharyngis.
The mucous coat is continuous with that Uning the auditory tubes, the nasal cavities, the
mouth, and the larynx. In the nasal part of the pharynx it is covered by columnar ciliated
epithelium; in the oral and laryngeal portions the epithelium is stratified squamous. Beneath
the mucous membrane are found racemose mucous glands; they are especially numerous at the
upper part of the pharynx around the orifices of the auditory tubes.
Fig. 1031. — Muscles of the pharynx, viewed from behind, together with the associated vessels and nerves.
(Modified after Testut.)
THE ESOPHAGUS (Fig. 1032).
The esophagus or gullet is a muscular canal, about 23 to 25 cm. long, extending
from the pharynx to the stomach. It begins in the neck at the lower border of
the cricoid cartilage, opposite the sixth cervical vertebra, descends along the
front of the vertebral column, through the superior and posterior mediastina,
passes through the diaphragm, and, entering the abdomen, ends at the cardiac
THE ESOPHAGUS
1145
orifice of the stomach, opposite the eleventh thoracic vertebra. The general direc-
tion of the esophagus is vertical; but it presents two slight curves in its course.
At its commencement it is placed in the middle line; but it inclines to the left side
as far as the root of the neck, gradually passes to the middle line again at the level
of the fifth thoracic vertebra, and finally deviates to the left as it passes forward
to the esophageal hiatus in the diaphragm. The esophagus also presents
antero-posterior flexures corresponding to the curvatures of the cervical and
thoracic portions of the vertebral column. It is the narrowest part of the diges-
tive tube, and is most contracted at its commencement, and at the point where
it passes through the diaphragm.
SUPERI
CERVIC
GANGLION
INTER
CAROTID
ARTERY
'in SUPERIOR LARVN°
GEAL NERVE
COMMON
CAROTID
ARTERY
PLEURA
PLEURA
INTERNAL
JUGULAR VEIN
TRACHEA
NFCRIOR
THYROID ARTERY
RECURRENT
NERVE
SUBCLAVICULAR
ARTERY
RIGHT CEPHALIC
TRUNK
ESOPHAGUS
LEFT
PULMONARY
ARTERY
LEFT BRONCHUS—
THORACIC DUCT
PLEURA
AZVQOS VEIN
VAGUS NERVE
AZYGOS VEIN
BRONCHIAL
ARTERY
RIGHT PUL-
MONARY VEIN
RIGHT LUNG
INF. VENA CAVA
DIAPHRAGM
Fig. 1032 — The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen
from behind. (Poirier and Charpy.)
Relations. — The cervical portion of the esophagus is in relation, in front, with the trachea;
and at the lower part of the neck, where it projects to the left side, with the thyroid gland; behind,
it rests upon the vertebral column and Longus colU muscles; on either side it is in relation with
the common carotid artery (especially the left, as it inclines to that side), and parts of the lobes
of the th)Toid gland; the recurrent nerves ascend between it and the trachea; to its left side is
the thoracic duct.
The thoracic portion of the esophagus is at first situated in the superior mediastinum be-
tween the trachea and the vertebral column, a little to the left of the median Une. It then
passes behind and to the right of the aortic arch, and descends in the posterior mediastinum
along the right side of the descending aorta, then runs in front and a little to the left of
the aorta, and enters the abdomen through the diaphragm at the level of the tenth thoracic
vertebra. Just before it perforates the diaphragm it presents a distinct dilatation. It is in
1146
SPLANCHNOLOGY
relation, in front, with the trachea, the left bronchus, the pericardium, and the diaphragm;
behind, it rests upon the vertebral column, the Longus colli muscles, the right aortic intercostal
arteries, the thoracic duct, and the hemiazygos veins; and below, near the diaphragm, upon
the front of the aorta. On its left side, in the superior mediastinum, are the terminal part
of the aortic arch, the left subclavian artery, the thoracic duct, and left pleura, while running
upward in the angle between it and the trachea is the left recurrent nerve; below, it is in relation
with the descending thoracic aorta. On its right side are the right pleura, and the azygos vein
which it overlaps. Below the roots of the lungs the vagi descend in close contact with it, the
right nerve passing down behind, and the left nerve in front of it; the two nerves uniting to
form a plexus around the tube.
In the lower part of the posterior mediastinum the thoracic duct hes to the right side
of the esophagus; higher up, it is placed behind it, and, crossing about the level of the fourth
thoracic vertebra, is continued upward on its left side.
The abdominal portion of the esophagus lies in the
esophageal groove on the posterior surface of the left
lobe of the liver. It measui-es about 1.25 cm. in length,
and only its front and left aspects are covered by
peritoneum. It is somewhat conical with its base
apphed to the upper orifice of the stomach, and is
known as the antrum cardiacum.
Structure (Fig. 1033). — The esophagus has four
coats: an external or fibrous, a muscular, a sub-
mucous or areolar, and an internal or mucous coat.
The muscular coat {tunica viuscularis) is composed
of two planes of considerable thickness: an external
of longitudinal and an internal of circular fibers.
The longitudinal fibers are arranged, at the com-
mencement of the tube, in three fasciculi: one in front,
which is attached to the vertical ridge on the posterior
surface of the lamina of the cricoid cartilage; and
one at either side, which is continuous with the mus-
cular fibers of the pharynx: as they descend they blend
together, and form a uniform layer, which covers the
outer surface of the tube.
Accessory slips of muscular fibers pass between the
esophagus and the left pleui-a, where the latter covers
the thoracic aorta, or the root of the left bronchus,
or the back of the pericardium.
The circular fibers are continuous above with the
Constrictor pharyngis inferior; their direction is trans-
verse at the upper and lower parts of the tube, but
obUque in the intermediate part.
The muscular fibers in the upper part of the esoph-
agus are of a red color, and consist chiefly of the striped
variety; but below they consist for the most part of
involuntary fibers.
The areolar or submucous coat {tela submucosa)
connects loosely the mucous and muscular coats. It
contains bloodvessels, nerves, and mucous glands.
The mucous coat {tunica mucosa) is thick, of a reddish color above, and pale below. It is
disposed in longitudinal folds, which disappear on distension of the tube. Its surface is studded
with minute papillae, and it is covered throughout with a thick layer of stratified squamous
epithehum. Beneath the mucous membrane, between it and the areolar coat, is a layer of longi-
tudinally arranged non-striped muscular fibers. This is the muscularls mucosae. At the com-
menoement of the esophagus it is absent, or only represented by a few scattered bundles; lower
down it forms a considerable stratum.
The esophageal glands {glandulw wsophagete) are small compound racemose glands of the
mucous type: they are lodged in the submucous tissue, and each opens upon the surface by a
long excretory duct.
Vessels and Nerves. — The arteries supplying the esophagus are derived from the inferior
thyroid branch of the thyrocervical trunk, from the descending thoracic aorta, from the left
gastric branch of the celiac arterj'^, and from the left inferior phrenic of the abdominal aorta.
They have for the most part a longitudinal direction.
The nerves are derived from the vagi and from the sympathetic trunks; they form a plexus,
in which are groups of gangUon cells, between the two layers of the muscular coats, and also a
second plexus in the submucous tissue.
Fig. 1033. — .Section of the human esophagus.
(From a drawing by V. Horsley.) Moderately
magnified. The section is transverse and from
near the middle of the gullet, a. Fibrous cover-
ing, b. Divnded fibers of longitudinal muscular
coat. c. Transverse muscular fibers, d. Sub-
mucous or areolar layer, e. Muscularis mucosse.
/. AIucous membrane, with vessels and part of a
lymphoid nodule, g. Stratified epithelial lining.
h. Mucous gland, i'. Gland duct. m'. Striated
muscular fibers cut across.
THE ABDOMEN 1147
THE ABDOMEN.
The abdomen is the largest cavity in the body. It is of an oval shape, the extrem-
ities of the oval being directed upward and downward. The upper extremity is
formed by the (haphragm which extends as a dome over the abdomen, so that the
cavity extends high into the bony thorax, reaching on the right side, in the mammary
line, to the upper border of the fifth rib; on the left side it falls below this level by
about 2.5 cm. The lower extremity is formed by the structures which clothe the
inner surface of the bony pelvis, principally the Levator ani and Coccygeus on
either side. These muscles are sometimes termed the diaphragm of the pelvis.
The cavity is wider above than below, and measures more in the vertical than in
the transverse diameter. In order to facilitate description, it is artificially divided
into two parts : an upper and larger part, the abdomen proper; and a lower and smaller
part, the pelvis. These two cavities are not separated from each other, but the
limit between them is marked by the superior aperture of the lesser pelvis.
The abdomen proper differs from the other great cavities of the body in being
bounded for the most part by muscles and fasciae, so that it can vary in capacity
and shape according to the condition of the viscera which it contains; but, in addi-
tion to this, the abdomen varies in form and extent with age and sex. In the adult
male, with moderate distension of the viscera, it is oval in shape, but at the same
time flattened from before backward. In the adult female, with a fully developed
pelvis, it is o\oid with the narrower pole upward, and in young children it is also
ovoid but with the narrower pole downward.
Boundaries. — It is bounded in front and at the sides by the abdominal muscles
and the Iliacus muscles; behind by the vertebral column and the Psoas and
Quadratus lumborum muscles; above by the diaphragm; below by the plane of
the superior aperture of the lesser pelvis. The muscles forming the boundaries
of the cavity are lined upon their inner surfaces by a layer of fascia.
The abdomen contains the greater part of the digestive tube; some of the
accessory organs to digestion, viz., the liver and pancreas; the spleen, the kidneys,
and the suprarenal glands. ]\Iost of these structures, as well as the wall of the
cavity in which they are contained, are more or less covered by an extensive and
complicated serous membrane, the peritoneum.
The Apertm-es in the Walls of the Abdomen. — The apertures in the walls of the
abdomen, for the transmission of structures to or from it, are, in front, the umbilical
(in the fetus), for the transmission of the umbilical vessels, the allantois, and vitel-
line duct; above, the vena caval opening, for the transmission of the inferior vena
cava, the aortic hiatus, for the passage of the aorta, azygos vein, and thoracic duct,
and the esophageal hiatus, for the esophagus and vagi. Below, there are two
apertures on either side: one for the passage of the femoral vessels and lumbo-
inguinal nerve, and the other for the transmission of the spermatic cord in the male,
and the round ligaruent of the uterus in the female.
Regions. — For convenience of description of the viscera, as well as of reference
to the morbid conditions of the contained parts, the abdomen is artificially divided
into nine regions by imaginary planes, two horizontal and two sagittal, passing
through the cavity, the edges of the planes being indicated by lines drawn on the
surface of the body. Of the horizontal planes the upper or transpyloric is indicated
by a line encircling the body at the level of a point midway between the jugular
notch and the symphysis pubis, the lower by a line carried around the trunk at the
level of a point midway between the transpyloric and the symphysis pubis. The
latter is practically the intertubercular plane of Cunningham, who pointed out^
that its level corresponds with the prominent and easily defined tubercle on the
iliac crest about 5 cm. behind the anterior superior iliac spine. By means of these
^ Journal of Anatomy and Physiologj', vol. xxvii.
1148
SPLANCHNOLOGY
imaginary planes the abdomen is divided into three zones, which are named from
above downward the subcostal, umbilical, and hypogastric zones. Each of these is
Fig. 1034. — Front view of the thoracic and abdominal viscera, a. Median plane, b b. Lateral planes, c c. Tratw^
tubercular plane, d d. Subcostal plane, e e. Transpyloric plane.
THE PERITONEUM 1149
further subdivided into three regions by the two sagittal planes, which are indi-
cated on the surface by lines drawn vertically through points half-way between
the anterior superior iliac spines and the symphysis pubis. ^
The middle region of the upjxT zone is called the epigastric; and the two lateral
regions, the right and left hypochondriac. The central region of the middle zone
is the umbilical; and the two lateral regions, the right and left lumbar. The middle
region of the lower zone is the hypogastric or pubic region; and the lateral regions
are the right and left ihac or inguinal (P'ig. 1034).
The pelvis is that portion of the abdominal cavity which lies below and behind
a plane passing through the promontory of the sacrum, linete terminales of the
hip bones, and the pubic crests. It is bounded behind by the sacrum, coccyx,
Piriformes, and the sacrospinous and sacrotuberous ligaments; in front and
laterally by the pubes and ischia and Obturatores interni; above it communicates
with the abdomen j)roper; below it is closed by the Levatores ani and Coccygei and
the urogenital diaphragm. The pelvis contains the urinary bladder, the sigmoid
colon and rectum, a few coils of the small intestine, and some of the generative
organs.
When the anterior abdominal wall is removed, the viscera are partly exposed
as follows: above and to the right side is the liver, situated chiefly under the shelter
of the right ribs and their cartilages, but extending across the middle line and reach-
ing for some distance below the level of the xiphoid process. To the left of the liver
is the stomach, from the lower border of which an apron-like fold of peritoneum,
the greater omentum, descends for a varying distance, and obscures, to a greater
or lesser extent, the other viscera. Below it, however, some of the coils of the small
intestine can generally be seen, while in the right and left iliac regions respectively
the cecum and the iliac colon are partly exposed. The bladder occupies the ante-
rior part of the pelvis, and, if distended, will project above the symphysis pubis;
the rectum lies in the concavity of the sacrimi, but is usually obscured by the coils
of the small intestine. The sigmoid colon lies between the rectum and the bladder.
When the stomach is followed from left to right it is seen to be continuous with
the first part of the small intestine, or duodenum, the point of continuity being
marked by a thickened ring which indicates the position of the pyloric valve.
The duodenum passes toward the under surface of the liver, and then, curving
downward, is lost to sight. If, however, the greater omentum be thrown upward
over the chest, the inferior part of the duodenum will be observed passing across
the vertebral column toward the left side, where it becomes continuous with the
coils of the jejunum and ileum. These measure some 6 meters in length, and if
followed downward the ileum will be seen to end in the right iliac fossa by opening
into the cecum, the commencement of the large intestine. From the cecum the
large intestine takes an arched course, passing at first upward on the right side,
then across the middle line and downward on the left side, and forming respectively
the ascending transverse, and descending parts of the colon. In the pelvis it
assumes the form of a loop, the sigmoid colon, and ends in the rectum.
The spleen lies behind the stomach in the left hypochondriac region, and may
be in part exposed by pulling the stomach over toward the right side.
The glistening appearance of the deep surface of the abdominal wall and of the
surfaces of the exposed viscera is due to the fact that the former is lined, and the
latter are more or less completely covered, by a serous membrane, the peritoneum.
The Peritoneum (Tunica Serosa).
The peritoneum is the largest serous membrane in the body, and consists, in the
male, of a closed sac, a part of which is applied against the abdominal parietes,
'Journal of Anatomy and Physiology, vols, xxxiii, xxxiv, xxxv.
1150 SPLANCHNOLOGY
while the remainder is reflected over the contained viscera. In the female the
peritoneum is not a closed sac, since the free ends of the uterine tubes open directly
into the peritoneal cavity. The part which lines the parietes is named the parietal
portion of the peritoneum; that which is reflected over the contained viscera con-
stitutes the visceral portion of the peritoneum. The free surface of the membrane
is smooth, covered by a layer of flattened mesothelium, and lubricated by a small
quantity of serous fluid. Hence the viscera can glide freely against the wall of the
cavity or upon one another with the least possible amount of friction. The attached
surface is rough, being connected to the viscera and inner surface of the parietes by
means of areolar tissue, termed the subserous areolar tissue. The parietal portion
is loosely connected with the fascial lining of the abdomen and pelvis, but is more
closely adherent to the under surface of the diaphragm, and also in the middle
line of the abdomen.
The space between the parietal and visceral layers of the peritoneum is named
the peritoneal cavity; but under normal conditions this cavity is merely a potential
one, since the parietal and visceral layers are in contact. The peritoneal cavity
gives off a large diverticulum, the omental bursa, which is situated behind the
stomach and adjoining structures; the neck of communication between the cavity
and the bursa is termed the epiploic foramen {foramen of Winslow). Formerly the
main portion of the cavity was described as the greater, and the omental bursa
as the lesser sac.
The peritoneum differs from the other serous membranes of the body in pre-
senting a much more complex arrangement, and one that can be clearly understood
only by following the changes which take place in the digestive tube during its
development.
To trace the membrane from one yiscus to another, and from the viscera to the
parietes, it is necessary to follow its continuity in the vertical and horizontal
directions, and it will be found simpler to describe the main portion of the cavity
and the omental bursa separately.
Vertical Disposition of the Main Peritoneal Cavity (greater sac) (Fig. 1035). — It
is convenient to trace this from the back of the abdominal wall at the level of the
umbilicus. On following the peritoneum upward from this level it is seen to be
reflected around a fibrous cord, the ligamentum teres {obliterated vmhUical vein),
which reaches from the umbilicus to the under surface of the liver. This reflection
forms a somewhat triangular fold, the falciform ligament of the liver, attaching the
upper and anterior surfaces of the liver to the diaphragm and abdominal wall.
\yith the exception of the line of attachment of this ligament the peritoneum
covers the whole of the under surface of the anterior part of the diaphragm,
and is continued from it on to the upper surface of the right lobe of the liver as
the superior layer of the coronary ligament, and on to the upper surface of the left
lobe as the superior layer of the left triangular ligament of the liver. Covering the
upper and anterior surfaces of the liver, it is continued around its sharp margin
on to the under surface, where it presents the following relations: (a) It covers the
under surface of the right lobe and is reflected from the back part of this on to the
right suprarenal gland and upper extremity of the right kidney, forming in this
situation the inferior layer of the coronary ligament; a special fold, the hepatorenal
ligament, is frequently present between the inferior surface of the liver and the
front of the kidney. From the kidney it is carried downward to the duodenum
and right colic flexure and medialward in front of the inferior vena cava, where it
is continuous with the posterior wall of the omental bursa. Between the two layers
of the coronary ligament there is a large triangular surface of the liver devoid of
peritoneal covering; this is named the bare area of the liver, and is attached to the
diaphragm by areolar tissue. Toward the right margin of the liver the two
layers of the coronary ligament gradually approach each other, and ultimately
THE PERITOXEUM
1151
fuse to form a small triangular fold connecting the right lobe of the liver to the
diaphragm, and named the right triangular ligament of the liver. The apex of
the triangular bare area corresponds with the point of meeting of the two layers
of the coronary ligament, its base with the fossa for the inferior vena cava. (6)
It covers the lower surface of the quadrate lobe, the under and lateral surfaces
of the gall-bladder, and the under surface and posterior border of the left lobe; it is
then reflected from the upper surface of the left lobe to the diaphragm as the
inferior layer of the left triangular ligament, and from the porta of the liver and the
fossa for the ductus venosus to the lesser curvature of the stomach and the first
2.5 cm. of the duodenum as the anterior layer of the hepatogastric and hepatoduodenal
ligaments, which together constitute the lesser omentum. If this layer of the lesser
omentum be followed to the right it will be found to turn around the hepatic artery,
bile duct, and portal vein, and become continuous with tlie anterior wall of the
Superior layer of
corollary ligament
Bare area of liver
Inferior layer of
coromiry ligament
Bristle in epij^oic
foramen
Stomach
Transverse colon
Greater omentum
Small intestine
Uterovesical
excavation
Bladder
Vagina
Vterus
Rectovaginal
excavation
Rectum
Fig. 1035. — ^'ertical disposition of the peritoneum. Main cavity, red; omental bursa, blue.
omental bursa, forming a free folded edge of peritoneum. Traced downward, it
covers the antero-superior surface of the stomach and the commencement of the
duodenum, and is carried down into a large free fold, known as the gastrocolic
ligament or greater omentum. Reaching the free margin of this fold, it is reflected
upward to cover the under and posterior surfaces of the transverse colon, and thence
to the posterior abdominal wall as the inferior layer of the transverse mesocolon.
It reaches the abdominal wall at the head and anterior border of the pancreas,
is then carried down over the lower part of the head and over the inferior surface
of the pancreas on the superior mesenteric vessels, and thence to the small intestine
as the anterior layer of the mesentery. It encircles the intestine, and subsequently
may be traced, as the posterior layer of the mesentery, upward and backward
to the abdominal wall. From this it sweeps down over the aorta into the pelvis,
where it invests the sigmoid colon, its reduplication forming the sigmoid mesocolon.
1152
SPLANCHNOLOGY
Leaving first the sides and then the front of the rectum, it is reflected on to the semi-
nal vesicles and fundus of the urinary bladder and, after covering the upper surface
of that viscus, is carried along the medial and lateral umbilical ligaments (Fig.
1036) on to the back of the abdominal wall to the level from which a start w^as made.
M. iliacns
Femoral
nerve
External
iliac
artery
Infernal
iliac
artery
Supravesical
fovea
Lateral
i)i<iuinal
fossa
Femoral
^ fovea
.Superior
vesical
artery
Jltdial
influinal
fovea
Fig. 1036. — Posterior view of the anterior abdominal wall in its lower half. The peritoneum is in plare. and the various
cords are shining through. (After Joessel.)
Between the rectum and the bladder it forms, in the male, a pouch, the recto-
vesical excavation, the bottom of which is slightly below the level of the upper
ends of the vesiculse seminales — i. e., about 7.5 cm. from the orifice of the anus.
\Yhen the bladder is distended, the peritoneum is carried up with the expanded
viscus so that a considerable part of the anterior surface of the latter lies directly
against the abdominal wall without the intervention of peritoneal membrane {i)re-
vesical space of Retzius). In the female the peritoneum is reflected from the rectum
over the posterior vaginal fornix to the cervix and body of the uterus, forming
the rectouterine excavation (jjoiich of Douglas). It is continued over the intestinal
surface and fundus of the uterus on to its vesical surface, which it covers as far as
the junction of the body and cervix uteri, and then to the bladder, forming here
a second, but shallower, pouch, the vesicouterine excavation. It is also reflected
from the sides of the uterus to the lateral walls of the pelvis as two expanded
folds, the broad ligaments of the uterus, in the free margin of each of which is the
uterine tube.
Vertical Disposition of the Omental Bursa {lesser 'peritoneal sac) (Fig. 1035). — A
start may be made in this case on the posterior abdominal wall at the anterior
border of the pancreas. From this region the peritoneum may be followed upward
THE PERITONEUM
1153
over the pancreas on to the inferior surface of the diaphragm, and thence on to the
caudate lobe and caudate process of the Hver to the fossa from the ductus venosus
and the porta of the liver. Traced to the right, it is continuous over the inferior
vena cava with the posterior wall of the main cavity. From the liver it is carried
downward to the lesser curvature of the stomach and the commencement of the
duodenum as the posterior layer of the lesser omentum, and is continuous on the
right, around the hepatic artery, bile duct, and portal vein, with the anterior layer
of this omentum. The posterior layer of the lesser omentum is carried down as a
covering for the postero-inferior surfaces of the stomach and commencement of the
duodenum, and is continued downward as the deep layer of the gastrocolic ligament
or greater omentum. From the free margin of this fold it is reflected upward on
itself to the anterior and superior surfaces of the transverse colon, and thence as
the superior layer of the transverse mesocolon to the anterior border of the pancreas,
the level from which a start was made. It will be seen that the loop formed by
the wall of the omental bursa below the transverse colon follows, and is closely
applied to, the deep surface of that formed by the peritoneum of the main cavity,
and that the greater omentum or large fold of peritoneum which hangs in front
of the small intestine therefore consists of four layers, two anterior and two posterior
separated by the potential cavity of the omental bursa.
Horizontal Disposition of the Peritoneum. — Below the transverse colon the
arrangement is simple, as it includes only the main cavity; above the level of the
transverse colon it is more complicated on account of the existence of the omental
bursa. Below the transverse colon it may be considered in the two regions, viz.,
in the pelvis and in the abdomen proper.
Medial
umbilical ligament
Fig. 1037. — The peritoneum of the male pelvis. (Dixon and Birmingham.)
(1) In the Pelvis. — The peritoneum here follows closely the surfaces of the
pelvic viscera and the inequalities of the pelvic walls, and presents important
differences in the two sexes, (a) In the male (Fig. 1037) it encircles the sigmoid
colon, from which it is reflected to the posterior wall of the pelvis as a fold, the
sigmoid mesocolon. It then leaves the sides and, finally, the front of the rectum,
73
1154
SPLANCHNOLOGY
and is continued on to the upper ends of the seminal vesicles and the bladder;
on either side of the rectum it forms a fossa, the pararectal fossa, which varies in
size with the distension of the rectum. In front of the rectum the peritoneum forms
the rectovesical excavation, which is limited laterally by peritoneal folds extending
from the sides of the bladder to the rectum and sacrum. These folds are known
from their position as the rectovesical or sacrogenital folds. The peritoneum of
the anterior pelvic wall covers the superior surface of the bladder, and on either
side of this viscus forms a depression, termed the paravesical fossa, which is limited
laterally by the fold of peritoneum covering the ductus deferens. The size of this
fossa is dependent on the state of distension of the bladder; when the bladder is
empty, a variable fold of peritoneum, the plica vesicalis transversa, divides the fossa
into two portions. On the peritoneum between the paravesical and pararectal
fossae the only elevations are those produced by the ureters and the hypogastric
vessels, (b) In the female, pararectal and paravesical fossse similar to those in the
male are present: the lateral limit of the paravesical fossa is the peritoneum invest-
ing the round ligament of the uterus. The rectovesical excavation is, however,
divided by the uterus and vagina into a small anterior vesicouterine and a large,
deep, posterior rectouterine excavation. The sacrogenital folds form the margins
of the latter, and are continued on to the back of the uterus to form a transverse
fold, the torus uterinus. The broad ligaments extend from the sides of the uterus
to the lateral walls of the pelvis; they contain in their free margins the uterine
tubes, and in their posterior layers the ovaries. Below, the broad ligaments are
continuous with the peritoneum on the lateral walls of the pelvis. On the lateral
pelvic wall behind the attachment of the broad ligament, in the angle between
the elevations produced by the diverging hypogastric and external iliac vessels is
a slight fossa, the ovarian fossa, in which the ovary normally lies.
Rectus
Small intestine
Mesentenj
Aorta
Inferior vena cava
Ascending colon
Descending colon
Quadratus lumborum
Psoas major I, • ••
•' Hacrospinmis
Fig. 1038. — Horizontal disposition of the peritoneum in the lower part of the abdomen.
(2) In the Lower Abdomen (Fig. 1038). — Starting from the linea alba, below the
level of the transverse colon, and tracing the continuity of the peritoneum in a
horizontal direction to the right, the membrane covers the inner surface of the
abdominal wall almost as far as the lateral border of the Quadratus lumborum;
THE PERITONEUM
1155
it encloses the cecum and vermiform process, and is reflected over the sides and front
of the ascending colon; it may then be traced over the duodenum, Psoas major,
and inferior vena cava toward the middle Hue, whence it passes along the mesen-
teric vessels to invest the small intestine, and back again to the large vessels in
front of the vertebral column, forming the mesentery, between the layers of which
are contained the mesenteric bloodvessels, lacteals, and glands. It is then con-
tinued over the left Psoas; it covers the sides and front of the descending colon,
and, reaching the abdominal wall, is carried on it to the middle line.
Lesser omentum
Falciform ligament of liver
Gastrolienal
ligament
Hepatic artery
bile duct, and
portal vein
Epiploic
foramen
Inferior
vena cava
Phrenicolienal ligament
Aorta
Fig. 1039. — Horizontal disposition of the peritoneum in the upper part of the abdomen.
(3) In the Upper Abdomen (Fig. 1039). — Above the transverse colon the omental
bursa is superadded to the general sac, and the communication of the two cavities
with one another through the epiploic foramen can be demonstrated.
(a) Main Cavity. — Commencing on the posterior abdominal wall at the inferior
vena cava, the peritoneum may be followed to the right over the front of the
suprarenal gland and upper part of the right kidney on to the antero-lateral
abdominal wall. From the middle line of the anterior wall a backwardly directed
fold encircles the obliterated umbilical vein and forms the falciform ligament
of the liver. Continuing to the left, the peritoneum lines the antero-lateral
abdominal wall and covers the lateral part of the front of the left kidney, and is"
reflected to the posterior border of the hilus of the spleen as the posterior layer
of the phrenicolienal ligament. It can then be traced around the surface of the spleen
to the front of the hilus, and thence to the cardiac end of the greater curvature
of the stomach as the anterior layer of the gastrolienal ligament. It covers the
antero-superior surfaces of the stomach and commencement of the duodenum,
and extends up from the lesser curvature of the stomach to the liver as the anterior
layer of the lesser omentum.
(h) Omental Bursa (bursa omentalis; lesser 'peritoneal sac). — On the posterior
abdominal wall the peritoneum of the general cavity is continuous with that of
the omental bursa in front of the inferior vena cava. Starting from here, the
bursa may be traced across the aorta and over the medial part of the front of
the left kidney and diaphragm to the hilus of the spleen as the anterior layer
of the phrenicolienal ligament. From the spleen it is reflected to the stomach as
1 1 56 SPLANCHNOLOGY
the posterior layer of the gastrosplenic ligament. It covers the postero-inferior
surfaces of the stomach and commencement of the duodenum, and extends
upward to the liver as the posterior layer of the lesser omentum; the right margin
of this layer is continuous around the hepatic artery, bile duct, and portal vein,
with the wall of the general cavity.
The epiploic foramen {foramen epiphicinn; foramen of Winslow) is the passage of
communication between the general cavity and the omental bursa. It is bounded
in front by the free border of the lesser omentum, with the common bile duct,
hepatic artery, and portal vein between its two layers; behind by the peritoneum
covering the inferior vena cava; above by the peritoneum on the caudate process
of the liver, and below by the peritoneum covering the commencement of the
duodenum and the hepatic artery, the latter passing forward below the foramen
before ascending between the two layers of the lesser omentum.
The boundaries of the omental bursa will now be evident. It is bounded in front,
from above downward, by the caudate lobe of the liver, the lesser omentum, the
stomach, and the anterior two layers of the greater omentum. Behind, it is limited,
from below upward, by the two posterior layers of the greater omentum, the trans-
verse colon, and the ascending layer of the transverse mesocolon, the upper surface
of the pancreas, the left suprarenal gland, and the upper end of the left kidney.
To the right of the esophageal opening of the stomach it is formed by that part
of the diaphragm which supports the caudate lobe of the liver. Laterally, the
bursa extends from the epiploic foramen to the spleen, where it is limited by
the phrenicolienal and gastrolienal ligaments.
The omental bursa, therefore, consists of a series of pouches or recesses to which
the following terms are applied: (1) the vestibule, a narrow channel continued
from the epiploic foramen, over the head of the pancreas to the gastropancreatic
fold; this fold extends from the omental tuberosity of the pancreas to the right
side of the fundus of the stomach, and contains the left gastric arterv and coronarv
vein; (2) the superior omental recess, between the caudate lobe of the liver and the
diaphragm; (3) the lienal recess, between the spleen and the stomach; (4) the
inferior omental recess, which comprises the remainder of the bursa.
In the fetus the bursa reaches as low as the free margin of the greater omentum,
but in the adult its vertical extent is usually more limited owing to adhesions
between the layers of the omentum. During a considerable part of fetal life the
transverse colon is suspended from the posterior abdominal wall by a mesentery
of its own, the two posterior layers of the greater omentum passing at this stage
in front of the colon. This condition occasionally persists throughout life, but as
a rule adhesion occurs between the mesentery of the transverse colon and the pos-
terior layer of the greater omentimi, with the result that the colon appears to receive
its peritoneal covering by the splitting of the two posterior layers of the latter fold.
In the adult the omental bursa intervenes between the stomach and the structures
on which that viscus lies, and performs therefore the functions of a serous bursa
for the stomach.
Numerous peritoneal folds extend between the various organs or connect them
to the parietes; they serve to hold the viscera in position, and, at the same time,
enclose the vessels and nerves proceeding to them. They are grouped under the
three headings of ligaments, omenta, and mesenteries.
The ligaments will be described with their respective organs.
There are two omenta, the lesser and the greater.
The lesser omentum {omentum minus; small omentum; gastrohepatic omentum) is the
duplicature which extends to the liver from the lesser curvature of the stomach and
the commencement of the duodenum. It is extremely thin, and is continuous with the
two layers of peritoneum which cover respectively the antero-superior and postero-
inferior surfaces of the stomach and first part of the duodenum. When these
two layers reach the lesser curvature of the stomach and the upper border of the
THE PERITONEUM 1157
duodenum, they join together and ascend as a double fold to the porta of the liver;
to the left of the porta the fold is attached to the bottom of the fossa for the ductus
venosus, along which it is carried to the diaphragm, where the two layers separate
to embrace the end of the esophagus. At the right border of the omentum the
two layers are continuous, and form a free margin which constitutes the anterior
boundary of the epiploic foramen. The portion of the lesser omentum extending
between the liver atid stomach is termed the hepatogastric ligament, while that
between the liver and duodenum is the hepatoduodenal ligament. Between the two
layers of the lesser omentum, close to the right free margin, are the hepatic
artery, the common bile duct, the portal vein, lymphatics, and the hepatic plexus of
nerves — all these structures being enclosed in a fibrous capsule (Glisson's capsule).
Between the layers of the lesser omentum, where they are attached to the
stomach, run the right and left gastric vessels.
The greater omentum {omentum majus; great omentum; gastrocolic omentum) is the
largest peritoneal fold. It consists of a double sheet of peritoneum, folded on itself
so that it is made up of four layers. The two layers which descend from the stomach
and commencement of the duodenum pass in front of the small intestines, sometimes
as low down as the pelvis; they then turn upon themselves, and ascend again as
far as the transverse colon, where they separate and enclose that part of the intes-
tine. These individual layers may be easily demonstrated in the young subject,
but in the adult they are more or less inseparably blended. The left border of the
greater omentum is continuous with the gastrolienal ligament; its right border
extends as far as the commencement of the duodenum. The greater omentum is
usually thin, presents a cribriform appearance, and always contains some adipose
tissue, which in fat people accumulates in considerable quantity. Between its
two anterior layers, a short distance from the greater curvature of the stomach,
is the anastomosis between the right and left gastroepiploic vessels.
The mesenteries are: the mesentery proper, the transverse mesocolon, and the
sigmoid mesocolon. In addition to these there are sometimes present an ascending
and a descending mesocolon.
The mesentery proper {mesenterium) is the broad, fan-shaped fold of peritoneum
which connects the convolutions of the jejunum and ileum with the posterior wall
of the abdomen. Its root — the part connected with the structures in front of the
vertebral column — is narrow, about 15 cm. long, and is directed obliquely from the
duodenojejunal flexure at the left side of the second lumbar vertebra to the right
sacroiliac articulation (Fig. 1040). Its intestinal border is about 6 metres long; and
here the two layers separate to enclose the intestine, and form its peritoneal coat.
It is narrow above, but widens rapidly to about 20 cm., and is thrown into numerous
plaits or folds. It suspends the small intestine, and contains between its layers
the intestinal branches of the superior mesenteric artery, with their accompanying
veins and plexuses of nerves, the lacteal vessels, and mesenteric lymph glands.
The transverse mesocolon {mesocolon transversum) is a broad fold, which connects
the transverse colon to the posterior wall of the abdomen. It is continuous with
the two posterior layers of the greater omentum, which, after separating to surround
the transverse colon, join behind it, and are continued backward to the vertebral
column, where they diverge in front of the anterior border of the pancreas. This
fold contains between its layers the vessels which supply the transverse colon.
The sigmoid mesocolon {mesocolon sigmoideian) is the fold of peritoneum which
retains the sigmoid colon in connection with the pelvic wall. Its line of attachment
forms a V-shaped curve, the apex of the curve being placed about the point of
division of the left common iliac artery. The curve begins on the medial side of
the left Psoas major, and runs upward and backward to the apex, from which it
bends sharply downward, and ends in the median plane at the level of the third
sacral vertebra. The sigmoid and superior hemorrhoidal vessels run between the
two lavers of this fold.
1158
SPLANCHNOLOGY
In most cases the peritoneum covers only the front and sides of the ascending
and descending parts of the colon. Sometimes, however, these are surrounded
by the serous membrane and attached to the posterior abdominal wall by an
ascending and a descending mesocolon respectively. A fold of peritoneum, the
phrenicocolic ligament, is continued from the left colic flexure to the diaphragm
opposite the tenth and eleventh ribs; it passes below and serves to support the
spleen, and therefore has received the name of sustentaculum lienis.
E>g!it triangiilnr Falciform ligament
ligatneyU uj itver of liur
Lr/t friangvlar
ligaintiit of liver
Inferior vena cavd .
JSso2>hngus .
Bight phrenic artery ..
\.
Left gastric artery ~
Hepatic artery .-
Liennl artenf .
Pancreas "
Inf. pancdun. artery —
Middle colic "
Superior mesenteric —
DtiOilenmn (horiz. part) —
Aorta —
Duodenum {desc. part) -
Bight a?id left kidneys "
Superior mesen teric ~
Aorta -
Left colic -
night colic —
Intestinal arteries < - 4
" J ]
Sigmoid artery ^ '
Sup. hem,orrhoidal artery -
Common iliac artery
Hypogastric artery
External iliac artery .,— ■
Inf. epigastric artery
Bladder 1&'
— ■ Peritoneum
Extrai>eritoneal tissue
( Diaphragmatic end of
^ t Usser omentum
' Gastrophrenic ligament
^ Phrenirolienal ligament
— Epiploic foramen
-- Duodenum (sup. part)
,^ _^^^'_^Phrenicocolic ligament
///.v^4^ ^J f Dot between two anterior
t layers of greater omentum
Transverse mesocolon
( Bare surface for descend'
\ ing colon
( The two layers of the
1 mesentery proper
Bare surface for ascend-
ing colon
Iliac mesocolon
Sigmoid mesocolon
Bare surface for rectum
( Cut edge of peritoneum
\ on bladder
Fig. 1040. — Diagram devised by Del6pino to show tlie lines along which the peritoneum leaves the wall of the abdomen
, to invest the viscera.
The appendices epiploicse are small pouches of the peritoneum filled with fat
and situated along the colon and upjjer part of the rectum. They are chiefly
appended to the transverse and sigmoid parts of the colon.
Peritoneal Recesses or Fossae {retroperitoneal fosscp). — In certain parts of the
abdominal cavity there are recesses of peritoneum forming culs-de-sac or pouches,
which are of surgical interest in connection with the possibility of the occurrence
of "retroperitoneal" hernise. The largest of these is the omental bursa (already
described), but several others, of smaller size, require mention, and may be divided
into three groups, viz. : duodenal, cecal, and intersigmoid.
I
THE PERITONEUM
1159
1. Duodenal Fossae (Figs. 1041, 1042). — Three are fairly constant, viz.: (a) The
inferior duodenal fossa, present in from 70 to 75 per cent, of cases, is situated
opposite the third hunbar vertebra on the left side of the ascending portion of
the duodenum. Its opening is directed upward, and is bounded by a thin sharp
Inferior
Tneatnteric
vein
Lhwde no jejunal
fold
Superior
duodenal fossa
Inferior
duodenal fossa
Duodenomesocolic
fold
Left colic artery
Fig. 1041. — Superior and inferior duodenal fossa. (Poirier and Charpy.)
fold of peritoneum with a concave margin, called the duodenomesocolic fold. The
tip of the index finger introduced into the fossa under the fold passes some
little distance behind the ascending portion of the duodenum. (6) The superior
duodenal fossa, present in from 40 to 50 per cent, of cases, often coexists with the
inferior one, and its orifice looks downward. It lies on the left of the ascending
Duodenum
Eight
duodeno-
mesocolic
fold
Inferior
mesenteric vein
Left
duodenomesocolic
fold
Left colic artery
Inferior mesenteric artery
Fig. 1042. — Duodenojejunal fossa. (Poirier and Charpy.)
portion of the duodenum, in front of the second lumbar vertebra, and behind a
sickle-shaped fold of peritoneum, the duodenojejunal fold, and has a depth of about
2 cm. (c) The duodenojejunal fossa exists in from 15 to 20 per cent, of cases,
but has never yet been found in conjunction with the other forms of duodenal
1160
SPLANCHNOLOGY
Anterior
Superior ileocecal
ileocecal artery
fold
fossse; it can be seen by pulling the jejunum downward and to the right, after the
transverse colon has been pulled upward. It is bounded above by the pancreas,
to the right by the aorta, and to the left by the kidney; beneath is the left renal
vein. It has a depth of from 2 to 3 cm., and its orifice, directed downward and to
the right, is nearly circular and will admit the tip of the little finger.
2. Cecal Fossae {pericecal folds or fossce). — There are three principal pouches
or recesses in the neighborhood of the cecum (Figs. 1043 to 1045) : (a) The superior
ileocecal fossa is formed by a fold of peritoneum, arching over the branch of the
ileocolic artery which supplies the ileocolic junction. The fossa is a narrow chink
•situated between the mesentery of the small intestine, the ileum, and the small
portion of the cecum behind. (6) The inferior ileocecal fossa is situated behind the
angle of junction of the ileum and cecinu. It is formed by the ileocecal fold of
peritoneum {bloodless fold of Treves), the upper border of which is fixed to the ileum,
opposite its mesenteric attach-
ment, while the lower border,
passing over the ileocecal junc-
tion, joins the mesenteriole of the
vermiform process, and some-
times the process itself. Between
this fold and the mesenteriole
of the vermiform process is the
inferior ileocecal fossa. It is
bounded above by the posterior
surface of the ileum and the me-
sentery ; in front and below by the
ileocecal fold, and behind b}^ the
upper part of the mesenteriole
of the ^'ermiform
The cecal fossa is
mediately behind
which has to be raised to bring
it into view. It varies much in
size and extent. In some cases
it is sufficiently large to admit the index finger, and extends upward behind the
ascending colon in the direction of the kidney; in others it is merelv a shallow
Mesentery
Superior
ileocecal
foatsa
Inferior
ileocecal
fold
Ileum
process, (c)
situated im-
the cecum.
Fig. 1043. — Superior ileocecal fossa. (Poirier and Charpy.)
Inferior
ileocecal fossa
Mesentery
\ Artery to
j vermiform process
Fig.
Mesenteriole of
vermiform process
1044. — Inferior ileocecal fossa. The cecum and ascending colon have been drawn lateralward and downward,
the ileum upward and backward, and the vermiform process downward. (Poirier and Charpy.)
depression. It is bounded on the right by the cecal fold, which is attached by
one edge to the abdominal wall from the lower border of the kidney to the iliac
THE STOMACH
1161
fossa and by the other to the postero-lateral aspect of the colon. In some
instances additional foss.ne, the retrocecal fossae, are present.
3. The intersigmoid fossa (reccs^us intersiginoideus) is constant in the fetus and
during infancy, but disappears in a certain percentage of cases as age advances.
Upon drawing the sigmoid colon upward, the left surface of the sigmoid mesocolon
is exposed, and on it will be seen a funnel-shaped recess of the peritoneum, lying
on the external iliac vessels, in the interspace between the Psoas and Iliacus muscles.
This is the orifice leading to the intersigmoid fossa, which lies behind the sigmoid
mesocolon, and in front of the parietal peritoneum. The fossa varies in size; in
some instances it is a mere dimple, Avhereas in others it will admit the whole of the
index finger.'
Inferior ileocecal
fold
_j — Inferior ileocecal fossa
M Mesenteriole of
vermiform process
Mese ntericoparietal
fold
Cecal fossa
Fig. 1045. — The cecal fossa. The ileum and cecum are drawn backward and upward. (Souligoux )
The Stomach (Ventriculus; Gaster).
The stomach is the most dilated part of the digestive tube, and is situated between
the end of the esophagus and the beginning of the small intestine. It lies in the
epigastric, umbilical, and left hypochondriac regions of the abdomen, and occupies
a recess bounded by the upper abdominal viscera, and completed in front and on
the left side by the anterior abdominal wall and the diaphragm.
The shape and position of the stomach are so greatly modified by changes within
itself and in the surrounding viscera that no one form can be described as typical.
The chief modifications are determined by (1) the amount of the stomach contents,
(2) the stage which the digestive process has reached, (3) the degree of develop-
ment of the gastric musculature, and (4) the condition of the adjacent intestines.
It is, however, possible by comparing a series of stomachs to determine certain
markings more or less common to all (Figs. 1046, 1047, 104S, 1049).
The stomach presents two openings, two borders or curvatures, and two surfaces.
Openings. — The opening by which the esophagus communicates with the
stomach is known as the cardiac orifice, and is situated on the left of the middle
line at the level of the tenth thoracic vertebra. The short abdominal portion of the
esophagus (antrum cardiacum) is conical in shape and curved sharply to the left,
' On the anatomy of these fosss, see the Arris and Gale Lectures by Moynihan, 1899.
1162 SPLANCHNOLOGY
the base of the cone being continuous with the cardiac orifice of the stomach.
The right margin of the esophagus is continuous with the lesser curvature of the
stomach, while the left margin joins the greater curvature at an acute angle, termed
the incisura cardiaca.
The pyloric orifice communicates with the duodenum, and its position is usually
indicated on the surface of the stomach by a circular groove, the duodenopyloric
constriction. This orifice lies to the right of the middle line at the level of the upper
border of the first lumbar vertebra.
Curvatures. — The lesser curvature (curvatura ventriculi minor), extending between
the cardiac and pyloric orifices, forms the right or posterior border of the stomach.
It descends as a continuation of the right margin of the esophagus in front of the
fibers of the right crus of the diaphragm, and then, turning to the right, it crosses
the first lumbar vertebra and ends at the pylorus. Nearer its pyloric than its
cardiac end is a well-marked notch, the incisura angularis, which varies somewhat
in position with the state of distension of the viscus; it serves to separate the
stomach into a right and a left portion. The lesser curvature gives attachment
to the two layers of the hepatogastric ligament, and between these two layers are
the left gastric artery and the right gastric branch of the hepatic artery.
The greater curvature (curvatura ventriculi major) is directed mainly forward,
and is four or five times as long as the lesser curvature. Starting from the cardiac
orifice at the incisura cardiaca, it forms an arch backward, upward, and to the left;
the highest point of the convexity is on a level with the sixth left costal cartilage.
From this level it may be followed downward and forward, with a slight convexity
to the left as low as the cartilage of the ninth rib; it then turns to the right, to the
end of the pylorus. Directly opposite the incisura angularis of the lesser curva-
ture the greater curvature presents a dilatation, which is the left extremity of the
pyloric part; this dilatation is limited on the right by a slight groove, the sulcus
intermedius, which is about 2.5 cm, from the duodenopyloric constriction. The
portion between the sulcus intermedius and the duodenopyloric constriction is
termed the pyloric antrum. At its commencement the greater curvature is covered
by peritoneum continuous with that covering the front of the organ. The left
part of the curvature gives attachment to the gastrolienal ligament, while to its
anterior portion are attached the two layers of the greater omentum, separated
from each other by the gastroepiploic vessels.
Surfaces. — When the stomach is in the contracted condition, its surfaces are
directed upward and downward respectively, but when the viscus is distended they
are directed forward, and backward. They may therefore be described as antero-
superior and postero-inferior.
Antero-superior Surface. — The left half of this surface is in contact with the
diaphragm, which separates it from the base of the left lung, the pericardium,
and the seventh, eighth, and ninth ribs, and intercostal spaces of the left side. The
right half is in relation with the left and quadrate lobes of the liver and with the
anterior abdominal wall. When the stomach is empty, the transverse colon may
lie on the front part of this surface. The whole surface is covered by peritoneum.
The Postero-inferior Surface is in relation with the diaphragm, the spleen,
the I'eft suprarenal gland, the upper part of the front of the left kidney, the anterior
surface of the pancreas, the left colic flexure, and the upper layer of the transverse
mesocolon. These structures form a shallow bed, the stomach bed, on which the
viscus rests. The transverse mesocolon separates the stomach from the duodeno-
jejunal flexure and small intestine. The postero-inferior surface is covered by
peritoneum, except over a small area close to the cardiac orifice; this area is limited
by the lines of attachment of the gastrophrenic ligament, and lies in apposition
with the diaphragm, and frequently with the upper portion of the left supra-
renal gland.
THE STOMACH
1163
Component Parts of the Stomach.^A plane passing through the incisura angularis on the lesser
curvature and the left limit of the opposed dilatation on the greater curvature divides the stomach
into a left portion or body and a right or pyloric portion. The left portion of the body is known
as the fundus, and is marked otT from the remainder of the body by a plane passing horizon-
tally through the cardiac orifice. The jjyloric portion is divided by a plane through the sulcus
intermedius at right angles to the long axis of this portion; the part to the right of this plane
is the pyloric antrum (Fig. 1046).
Antrum cardiacum —\
Incisura aix{jularis
Pylorodxiodenal ~^'/(
openini) / /{
Pyloric antrum
Sulcus intermedius
Pyloric part
Fig. 1046. — Outline of stomach, showing its anatomical
landmarks.
Fig. 1047. — Diagram showing shape and position
of empty stomach. Erect posture. (Hertz )
If the stomach be examined during the process of digestion it will be found divided by a
muscular constriction into a large dilated left portion, and a narrow contracted tubular right
portion. The constriction is in the body of the stomach, and does not follow any of the
anatomical landmarks; indeed, it shifts gradually toward the left as digestion progresses, i. e.,
more of the body is gradually absorbed into the tubular part (Figs. 1047, 1048, 1049).
Fig. 1048. — Diagram showing shape and position of
moderately filled stomach. Erect posture. (Hertz.)
Fig. 1049. — Diagram showing shape and position of
distended stomach. Erect posture. (Hertz.)
Position of the Stomach. — ^The position of the stomach varies with the posture, with the
amount of the stomach contents and with the condition of the intestines on which it rests. In
the erect posture the empty stomach is somewhat J-shaped; the part above the cardiac orifice
is usually distended with gas; the pylorus descends to the level of the second lumbar vertebra
and the most dependent part of the stomach is at the level of the umbilicus, ^'ariation in the
amount of its contents affects mainly the cardiac portion, the pyloric portion remaining in a more
or less contracted condition during the process of digestion. As the stomach fills it tends to
expand forward and downward in the direction of least resistance, but when this is interfered
with by a distended condition of the colon or intestines the fundus presses upward on the liver
and diaphragm and gives rise to the feehngs of oppression and palpitation complained of in
such cases. His^ and Cunningham^ have shown by hardening the viscera in situ that the con-
tracted stomach has a sickle shape, the fundus looking directly backward. The surfaces are
directed upward and downward, the upper surface having, however, a gradual downward slope
to the right. The greater curvature is in front and at a slightly higher level than the lesser.
' Archiv fiir Anatomie und Physiologie, anat. Abth., 1903.
' Transactions of the Royal Society of Edinburgh, vol. xlv, part i.
1164
SPLANCHNOLOGY
The position of the full stomach depends, as already indicated, on the state of the intestines;
when these are empty the fundus expands verticallj'^ and also forward, the pylorus is displaced
toward the right and the whole organ assumes an oblique position, so that its surfaces are directed
more forward and backward. The lowest part of the stomach is at the pyloric vestibule, which
reaches to the region of the umbilicus. Where the intestines interfere with the downward
expansion of the fundus the stomach retains the horizontal position which is characteristic of
the contracted viscus.
Examination of the stomach during life by x-rays has confirmed these findings, and has
demonstrated that, in the erect posture, the full stomach usually presents a hook-Uke appear-
ance, the long axis of the clinical fundus being directed downward, medialward, and forward
toward the umbiUcus, while the pjdoric portion curves upward to the duodenopyloric junction.
Interior of the Stomach. — When examined after death, the stomach is usually fixed at some
temporary stage of the digestive process. A common form is that shown in Fig. 1050. If the
viscus be laid open by a section through the plane of its two curvatures, it is seen to consist of
two segments: (a) a large globular portion on the left and (6) a narrow tubular part on the
right. These correspond to the clinical subdivisions of fundus and pyloric portions already
described, and are separated by a constriction which indents the body and greater curvature,
but does not involve the lesser curvature. To the left of the cardiac orifice is the incisura
cardiaca: the projection of this notch into the cavity of the stomach increases as the organ
distends, and has been supposed to act as a valve preventing regurgitation into the esophagus.
In the pyloric portion are seen: (a) the elevation corresponding to the incisura angularis, and
(6) the circular projection from the duodenopyloric constriction which forms the pj'loric valve;
the separation of the pyloric antrum from the rest of the pyloric part is scarceh' indicated.
Pylonus
Pyloric antrum
Fig. 10.50. — Interior of the stomach. .
The pyloric valve {vahula pylori) is formed by a reduplication of the mucous
membrane of the stomach, covering a muscular ring composed of a thickened por-
tion of the circular layer of the muscular coat. Some of the deeper longitudinal
fibers turn in and interlace with the circular fibers of the valve.
Structure. — The wall of the stomach consists of four coats: serous, muscular, areolar, and
mucous, together with vessels and nerves.
The serous coat {tunica serosa) is derived from the peritoneum, and covers the entire surface
of the organ, excepting along the greater and lesser curvatures at the points of attachment of
the greater and lesser omenta; here the two layers of peritoneum leave a small triangular space,
along which the nutrient vessels and nerves pass. On the posterior surface of the stomach,
close to the cardiac orifice, there is also a small area uncovered by peritoneum, where the organ
is in contact with the under surface of the diaphragm.
The muscular coat {tunica 7miscularis) (Figs. 1051, 1052) is situated immediately beneath the
serous covering, with which it is closely connected. It consists of three sets of smooth muscle
fibers: longitudinal, circular. and oblique.
The longitvxlinal fibers {stratum longitudinale) are the most superficial, and are arranged in
THE STOMACH
1165
two sets. The first set consists of fibers continuous with the longitudinal fibers of the esophagus;
they radiate in a stellate manner from the cardiac orifice and are practically all lost before the
pyloric portion is reached. The second set commences on the body of the stomach and passes
Esophanu,':
Fig. 1051. — The longitudinal and circular muscular fibers of the stomach, viewed from above and in front. (Spalteholz.)
to the right, its fibers becoming more thickly distributed as they approach the pylorus. Some
of the more superficial fibers of this set pass on to the duodenum, but the deeper fibers dip inward
and interlace with the circular fibers of the pyloric valve.
^sophagu
Fig. 1052. — The oblique muscular fibers of the stomach, viewed from above and in front. (Spalteholz.)
The circular fibers (stratum circulare) form a uniform layer over the whole extent of the stomach
beneath the longitudinal fibers. At the pylorus they are most abundant, and are aggregated into
1166 SPLANCHNOLOGY
a circular ring, which projects into the lumen, and forms, with the fold of mucous membrane
covering its surface, the pyloric valve. They are continuous with the circular fibers of the
esophagus, but are sharply marked off from the circular fibers of the duodenum.
The oblique fibers {fibrw obliqucf) internal to the circular layer, are hmited chiefly to the
cardiac end of the stomach, where they are disposed as a thick uniform layer, covering both
surfaces, some passing obUquely from left to right, others from right to left, around the cardiac
end.
The areolar or submucous coat {tela submucosa) consists of a loose, areolar tissue, connecting
the mucous and muscular layers.
The mucous membrane {tunica mucosa) is thick and its siu-face is smooth, soft, and velvety.
In the fresh state it is of a pinkish tinge at the pyloric end, and of a red or reddish-brown color
over the rest of its sm-face. In infancy it is of a brighter huC; the vascular redness being more
marked. It is thin at the cardiac extremity, but thicker toward the pylorus. During the con-
tracted state of the organ it is thrown into numerous plaits or rugae, which, for the most part,
have a longitudinal direction, and are most marked toward the pyloric end of the stomach,
and along the greater curv'ature (Fig. 1050). These folds are entirely obliterated when the organ
becomes distended.
^^^ : ^^ ,\ m cr
r > J u^ -i' ■ -:*«^^J#^
^viSI-fft'
A}-— mm
^i^^l
0
Fig. 1053. — Section of mucous membrane of human stomach, near the cardiac orifice, (v. Ebner, after J. SchafPer.)
X 45. c. Cardiac glands, d. Their ducts, cr. Gland similar to the intestinal glands, with goblet cells, mm. Mucous
membrane, m. Muscularis mucossB. m'. Muscular tissue within the mucous membrane.
Structure of the Mucous Membrane. —V^'hen examined with a lens, the inner surface of the
mucous membrane presents a peculiar honeycomb appearance from being covered with small
shallow depressions or alveoli, of a polygonal or hexagonal form, which vary from 0.12 to 0.25
mm. in diameter. These are the ducts of the gastric glands, and at the bottom of each may be
seen one or more minute orifices, the openings of the gland tubes. The surface of the mucous
membrane is covered bv a single layer of columnar epithehum with occasional goblet cells. This
epithehum commences very abruptly at the cardiac orifice, where there is a sudden transition
from the stratified epithehum of the esophagus. The epithehal lining of the gland ducts is of
the same character and is continuous with the general epithelial lining of the stomach (Fig. 1055).
The Gastric Glands. — The gastric glands are of three kinds: (a) pyloric, (6) cardiac, and (c)
fundus or 0X3mtic glands. They are tubular in character, and are formed of a dehcate basement
membrane, consisting of flattened transparent endothehal cells lined by epithehum. The pyloric
glands (Fig. 1054) are found in the pyloric portion of the stomach. They consist of two or
three short closed tubes opening into a common duct or mouth. These tubes are wavy, and
are about one-half the length of the duct. The duct is lined by columnar cells, continuous
with the epithelium hning the surface of the mucous membrane of the stomach, the tubes
by shorter and more cubical cell which are finely granular. The cardiac glands (Fig. 1053),
few in number, occur close to the cardiac orifice. They are of two kinds: (1) simple tubular
glands resembhng those of the pyloric end of the stomach, but with short ducts; (2) com-
pound racemose glands resembling the duodenal glands. The fimdus glands (Fig. 1055) are
found in the body and fundus of the stomach; they are simple tubes, two or more of which
THE STOMACH
1167
open into a single duct. The duct, however, in tliese glands is shorter tlian in the pyloric
variety, sometimes not amounting to more than one-sixth of the whole length of the gland;
it is lined throughout by columnar epithelium. The gland tubes arc straight and parallel to each
other. At the point where they open into the duct, which is termed the neck, tlie epithehum
alters, and consists of short columnar or polyhedral, granular cells, which almost fill the tube,
so that the lumen becomes suddenly constricted and is continued down as a very fine channel.
They are known as the chief or central cells of the glands. Between these cells and the basement
membrane, larger oval cells, which stain deeply with eosin, are found; these cells are studded
throughout the tube at intervals, giving it a beaded or varicose appearance. These are known
as the parietal or oxyntic cells, and they are connected with the lumen by fine channels which run
mto their substance. Between the glands the mucous membrane consists of a connective-tissue
frame-work, with lymphoid tis.sue. In jjlaces, this latter tissue, especially in early life, is collected
into little masses, whicli to a certain extent resemble the solitary nodules of the intestine, and are
termed the lenticular glands of the stomach. They are not, however, so distinctly circumscribed
as the solitary nodules. Beneath the mucous membrane, and between it and the submucous
coat, is a thin stratum of involuntary nmscular fiber (muscularis niucoscr), which in some parts
consists only of a single longitudinal layer; in others of two layers, an inner circular and an outer
longitudinal.
Fig. 1054. — A pyloric gland, from a section of the
dog's stomach. (Ebstein.) ?n. Mouth, n. Neck. tr.
\ deep portion of a tubule cut transversely.
FiQ. 10.5.5. — .\ fundus gland. A. Transverse section
of gland.
Vessels and Nerves. — The arteries supplying the stomach are: the left gastric, the right
gastric and right gastroepiploic branches of the hepatic, and the left gastroepiploic and short
gastric branches of the lienal. They supply the muscular coat, ramify in the submucous coat, and
are finally distributed to the mucous membrane. The arrangement of the vessels in the mucous
membrane is somewhat peculiar. The arteries break up at the base of the gastric tubules into
a plexus of fine capillaries which run upward between the tubules, anastomosing with each other,
and ending in a plexus of larger capillaries, which surround the mouths of the tubes, and also
form hexagonal meshes around the ducts. From these the veins arise, and pursue a straight
course downward, between the tubules, to the submucous tissue; they end either in the lienal
and superior mesenteric veins, or directly in the portal vein. The lymphatics are numerous:
they consist of a superficial and a deep set, and pass to the lymph glands found along the two
curvatures of the organ (page 706). The nerves are the terminal branches of the right and left
1168
SPLANCHNOLOGY
vagi, the former being distributed upon the back, and the latter upon the front part of the organ.
A great number of branches from the celiac plexus of the sympathetic are also distributed to
it. Nerve plexuses are found in the submucous coat and between the layers of the muscular coat
as in the intestine. From these plexuses fibrils are distributed to the muscular tissue and the
mucous membrane.
The Small Intestine (Intestinum Tenue).
The small intestine is a convoluted tube, extending from the pylorus to the colic
valve, where it ends in the large intestine. It is about 7 metres long,^ and gradually
diminishes in size from its commencement to its termination. .It is contained in
the central and lower part of the abdominal cavity, and is surrounded above and
at the sides by the large intestine; a portion of it extends below the superior
aperture of the pelvis and lies in front of the rectum. It is in relation, in front, with
the greater omentum and abdominal parietes, and is connected to the vertebral
column by a fold of peritoneum, the mesentery. The small intestine is divisible
into three portions: the duodenum, the jejunum, and the ileum.
Fig. 1056. — The duodenum and pancreas.
The Duodenum (Fig. 1056) has received its name from being about equal in
length to the breadth of twelve fingers (25 cm.). It is the shortest, the widest,
and the most fixed part of the small intestine, and has no mesentery, being only
partially covered by peritoneum. Its course presents a remarkable curve, some-
what of the shape of an imperfect circle, so that its termination is not far removed
from its starting-point.
In the adult the course of the duodenum is as follows : commencing at the pylorus
it passes backward, upward, and to the right, beneath the quadrate lobe of the
liver to the neck of the gall-bladder, varying slightly in direction according to the
degree of distension of the stomach: it then takes a sharp curve and descends
along the right margin of the head of the pancreas, for a \ariable distance, generally
to the level of the upper border of the body of the fourth lumbar vertebra. It
' Treves states that, in one hundred cases, the average length of the small intestine in the adult male was 22 feet
6 iriches, and in the adult female 2.3 feet 4 inches; but that it varies very much, the extremes in the male being 31 feet
10 inches, and 15 feet 6 inches. lie states that in the adult the length of the bowel is independent of age, height, and
weight.
THE SMALL INTESTINE
1169
now takes a second bend, and passes from right to left across the vertebral cohiran,
having a slight incHnation upward; and on the left side of the vertebral column
it ascends for about 2.5 cm., and then ends opposite the second lumbar vertebra
in the jejunum. As it unites with the jejunum it turns abruptly forward, forming
the duodendojejunal flexure. From the above description it will be seen that the
duodenum may be tlivided into four portions: superior, descending, horizontal,
and ascending.
Relations. — The superior portion (pars superior; first portion) is about 5 cm. long.
Beginning at the pylorus, it ends at the neck of the gall-bladder. It is the most
movable of the four portions. It is almost completely covered by peritoneum, but a
small part of its posterior surface near the neck of the gall-bladder and the inferior
Fig. 1057
Probe i?i pancreatic duct
Probe in common bile-duct
— Interior of the descending portion of the duodenum, showing bile papilla.
vena cava is uncovered; the upper border of its first half has the hepatoduodenal
ligament attached to it, while to the lower border of the same segment the greater
omentum is connected. It is in such close relation with the gall-bladder that it
is usually found to be stained by bile after death, especially on its anterior surface.
It is in relation above and in front with the quadrate lobe of the liver and the gall-
bladder; behind with the gastroduodenal artery, the common bile duct, and the
portal vein; and below and behind with the head and neck of the pancreas.
The descending portion (pars descendens; second portion) is from 7 to 10 cm. long, and
extends from the neck of the gall-bladder, on a level with the first lumbar vertebra,
along the right side of the vertebral column as low as the upper border of the body
of the fourth lumbar vertebra. It is crossed in its middle third by the transverse
colon, the posterior surface of which is uncovered by peritoneum and is connected
to the duodenum by a small quantity of connective tissue. The supra- and infra-
colic portions are covered in front by peritoneum, the infracolic part by the right
leaf of the mesentery. Posteriorly the descending portion of the duodenum is not
covered by peritoneum. The descending portion is in relation, in front, from above
downward, with the duodenal impression on the right lobe of the liver, the trans-
verse colon, and the small intestine; behind, it has a variable relation to the front
of the right kidney in the neighborhood of the hilum, and is connected to it by
loose areolar tissue; the renal vessels, the inferior vena cava, and the Psoas below,
• 74
1 1 70 SPLANCHNOLOG Y
are also behind it. At its medial side is the head of the pancreas, and the common
bile duct; to its lateral side is the right colic flexure. The common bile duct and
the pancreatic duct together perforate the medial side of this portion of the intestine
obliquely (Figs. 1057 and 1100), some 7 to 10 cm. below the pylorus; the accessory
pancreatic duct sometimes pierces it about 2 cm. above and slightly in front of these.
The horizontal portion {jjars horizontaUs; third or j^reaortic or transverse portion) is
from 5 to 7.5 cm. long. It begins at the right side of the upper border of the fourth
lumbar vertebra and passes from right to left, with a slight inclination upward,
in front of the great vessels and crura of the diaphragm, and ends in the ascending
portion in front of the abdominal aorta. It is crossed by the superior mesenteric
vessels and the mesentery. Its front surface is covered by peritoneum, except
near the middle line, where it is crossed by the superior mesenteric vessels. Its
posterior surface is uncovered by peritoneum, except toward its left extremity,
where the posterior layer of the mesentery may sometimes be found covering it
to a variable extent. This surface rests upon the right crus of the diaphragm,
the inferior vena cava, and the aorta. The upper surface is in relation with the
head of the pancreas.
The ascending portion {pars ascendens; fourth portion) of the duodenum is about
2.5 cm long. It ascends on the left side of the aorta, as far as the level of the upper
border of the second lumbar vertebra, where it turns abruptly forward to become
the jejunum, forming the duodenojejunal flexure. It lies in front of the left Psoas
major and left renal vessels, and is covered in front, and partly at the sides, by
peritoneum continuous with the left portion of the mesentery.
The superior part of the duodenum, as stated above, is somewhat movable,
but the rest is practically fixed, and is bound down to neighboring viscera and the
posterior abdominal wall by the peritoneum. In addition to this, the ascending
part of the duodenum and the duodenojejunal flexure are fixed by a structure
to which the name of Musculus snspensorius duodeni has been given. This structure
commences in the connective tissue around the celiac artery and left crus of the
diaphragm, and passes downward to be inserted into the superior border of the
duodenojejunal curve and a part of the ascending duodenum, and from this it is
continued into the mesentery. It possesses, according to Treitz, plain muscular
fibers mixed with the fibrous tissue of which it is principally made up. It is of
little importance as a muscle, but acts as a suspensory ligament.
Vessels and Nerves. — The arteries supplying the duodenum are the right gastric and superior
pancreaticoduodenal branches of the hepatic, and the inferior pancreaticoduodenal branch of
the superior mesenteric. The veins end in the lienal and superior mesenteric. The nerves are
derived from the coeliac plexus.
Jejunum and Ileum. — The remainder of the small intestine from the end of the
duodenum is named jejunum and ileum; the former term being given to the upper
two-fifths and the latter to the lower three-fifths. There is no morphological line
of distinction between the two, and the division is arbitrary; but at the same time
the character of the intestine gradually undergoes a change from the commence-
ment of the jejunum to the end of the ileum, so that a portion of the bowel taken
from these two situations would present characteristic and marked differences.
These are briefly as follows:
The Jejunum {intestinum jejunum) is wider, its diameter being about 4 cm.,
and is thicker, more vascular, and of a deeper color than the ileum, so that a given
length weighs more. The circular folds {valvulop conniventes) of its mucous mem-
brane are large and thickly set, and its villi are larger than in the ileum. The aggre-
gated lymph nodules are almost absent in the upper part of the jejunum, and in
the lower part are less frequently found than in the ileum, and are smaller and tend
to assume a circular form. By grasping the jejunum between the finger and thumb
the circular folds can be felt through the walls of the gut; these being absent in
rilE SMALL INTESTINE
1171
the lower part of the ileum, it is possible in this way to distinguish the upper
from the lower part of the small intestine.
The Ileum (intestinuni ileum) is narrow, its diameter being 3.75 cm., and its
coats thinner and less vascular than those of the jejuimm. It possesses but few
circular folds, and they are small and disappear entirely toward its lower end,
but aggregated lymph nodules (Peyer's patches) are larger and more numerous.
The jejunum for the most part occupies the umbilical and left iliac regions, while
Villi
Intestinal glands
Muscularts mucosce
Duodenal glands in
sid)7nucosa
Circular muscular layer
Longitudinal muscular
layer
Si-4 Serous coat
Fia. 1058. — Section of duodenum of cat. (After Schafer.) X 60.
the ileum occupies chiefly the umbilical, hypogastric, right iliac, and pelvic regions.
The terminal part of the ileum usually lies in the pelvis, from which it ascends over
the right Psoas and right iliac vessels; it ends in the right iliac fossa by opening
into the medial side of the commencement of the large intestine. The jejunum
and ileum are attached to the posterior abdominal wall by an extensive fold of
peritoneum, the mesentery, which allows the freest motion, so that each coil can
accommodate itself to changes in form and position. The mesentery is fan-shaped;
1172
SPLANCHNOLOGY
its posterior border or root, about 15 cm. long, is attached to the posterior abdominaj
wall from the left side of the body of the second lumbar vertebra to the right sacro-
iliac articulation, crossing successively the horizontal part of the duodenum, the
aorta, the inferior vena cava, the ureter, and right Psoas muscle (Fig. 1040). Its
breadth between its vertebral and intestinal borders averages about 20 cm., and is
greater in the middle than at its upper and lower ends. According to Lockwood it
tends to increase in breadth as age advances. Between the two layers of which it is
composed are contained bloodvessels, nerves, lacteals, and lymph glands, together
with a variable amount of fat.
Central lacteal
Smooth rmiscle fibers
Reticular tissue
Columnar epithelium.
Fig. 1059. — Vertical section of a \-illus from the
dog's small intestine. X SO.
Fig. 1060. — Transverse section of a villus, from the human intes-
tine, (v. Ebner.) X 350. a. Basement membrane, here some-
what shrunken away from the epithelium. 6. Lacteal, c.
Columnar epithelium, d. Its striated border, e. Goblet cells.
/. Leucocytes in epithelium. /'. Leucocytes below epithelium.
g. Bloodvessels, h. Muscle cells cut across.
Meckel's Diverticuliun {diverticulum ilei). — This consists of a pouch which projects from the
lower part of the ileum in about 2 per cent, of subjects. Its average position is about 1 meter
above the colic valve, and its average length about 5 cm. Its cahber is generallj' similar to that
of the ileum, and its bUnd extremity may be free or may be connected with the abdominal wall
or with some other portion of the intestine by a fibrous band. It represents the remains of
the proximal part of the vitelline duct, the duct of communication between the j-olk-sac and the
pruniti\e digestive tube in early fetal life.
Structure. — The wall of the small intestine (Fig. 1058). is composed of four coats: serous,
muscular, areolar, and mucous.
The serous coat {tunica serosa) is derived from the peritoneum. The superior portion of the
duodenum is ahnost completely surrounded by this membrane near its pj-loric end, but is only
covered in front at the other extremity; the descending portion is covered by it in front, except
where it is carried off bj'^ the transverse colon; and the inferior portion lies behind the peritoneum
which passes over it without being closely incorporated with the other coats of this part of the
intestine, and is separated from it in and near the middle Une by the superior mesenteric vessels.
The rest of the small intestine is surrounded by the peritoneum, excepting along its attached
or mesenteric border; here a space is left for the vessels and nerves to pass to the gut.
The muscular coat {tunica muscularis) consists of two layers of unstriped fibers: an external,
longitudinal, and an internal, circular layer. The longitudinal fibers are thinlj' scattered over the
surface of the intestine, and are more distinct along its free border. The circular fibers form a
thick, uniform layer, and are composed of plain muscle cells of considerable length. The mus-
cular coat is thicker at the upper than at the lower part of the small intestine.
The areolar or submucous coat {tela submucosa) connects together the mucous and muscular
layers. It consists of loose, filamentous areolar tissue containing bloodvessels, lymphatics, and
nerves. It is the strongest laj^er of the intestine.
THE SMALL IXTESTIXE
1173
The mucous membrane {tunica mucosa) is thick ami highly vascular at the upper part of
the small intestine, but somewhat paler and thinner below. It consists of the following structures:
Capillaries
Lymphatic vessel
— Capillaries
-- Lymphatic vessel
Sinall artery Lymphatic plexus
Fig. 1061 — Villi of small intestine, showing bloodvessels and lymphatic vessels. (Cadiat.)
next the areolar or submucous coat is a double layer of unstriped muscular libers, outer longi-
tudinal and inner circular, the muscularis mucosae; internal to this is a quantity of retiform
tissue, enclosing in its meshes hnnph corpuscles, and in this the
bloodvessels and nerves ramify; lastly, a basement membrane,
supporting a single laj'er of epithehal cells, which tlu-oughout the
intestine are columnar in character. The cells are gi-anular in
appearance, and each possesses a clear oval nucleus. At their
superficial or unattached ends they present a distinct layer of
highly refracting material, marked by vertical striae, the striated
border.
The mucous membrane presents for examination the following
structures, contained within it or belonging to it:
Circular folds. Duodenal glands.
VilU. Solitary lymphatic nodules.
Intestinal glands. Aggregated lymphatic nodules.
The circular folds {plica' circulares [Kirkringi]; valvulw conni-
ventes; valves of Kerkring) are large valvular flaps projecting into
the lumen of the bowel. They are composed of reduplications of the
mucous membrane, the two layers of the fold being bound together
by submucous tissue; unlike the folds in the stomach, they are per-
manent, and are not obliterated when the intestine is distended.
The majority extend transversely around the cylinder of the intes-
tine for about one-half or two-thirds of its circumference, but some
form complete circles, and others have aspu-al direction; the latter
usually extend a little more than once around the bowel, but occa-
sionally two or three times. The larger folds are about 8 mm. in
depth at their broadest part; but the greater number are of smaller
size. The larger and smaller folds alternate with each other. They
are not found at the commencement of the duodenum, but begin
to appear about 2.5 or 5 cm. beyond the pylorus. In the lower
part of the descending portion, below the point where the bile and pancreatic ducts enter the
intestine, they are very large and closely approximated. In the horizontal and ascending
portions of the duodenmn and upper half of the jejunum thej' are large and numerous, but
Fig. 1062. — An intestinal gland
from the human intestine. (Flem-
ming.)
1174
SPLANCHNOLOGY
from this point, down to the middle of the ileum, they diminish considerably in size. In the
lower part of the ileum they almost entirely disappear; hence the comparative thinness of this
portion of the intestine, as compared with the duodenum and jejunum. The circular folds
retard the passage of the food along the intestines, and afford an increased surface for absorption.
Fig. 1063. — Vertical section of a human aggregated lymphatic nodule, injected through its lymphatic canals, a.
Villi with their chyle passages. 6. Intestinal glands, c. Muscularis mucosae, d. Cupola or apex of solitary nodule.
e. Mesial zone of nodule. /. Base of nodule, g. Points of exit of the lacteals from the villi, and entrance into the true
mucous membrane, h. Retiform arrangement of the lymphatics in the mesial zone. i. Course of the latter at the
base of the nodule, k. Confluence of the lymphatics opening into the vessels of the submucous tissue. /. Follicular
tissue of the latter.
,JUl-
Capillary network
The intestinal villi {villi intestinales) are highly vascular processes, projecting from the mucous
membrane of the small intestine throughout its whole extent, and giving to its surface a velvety
appearance. They are largest and most numer-
ous in the duodenum and jejunum, and become
fewer and smaller in the ileum.
Structure of the villi (Figs. 1059, 1060).— The
essential parts of a villus are: the lacteal vessel,
the bloodvessels, the epithehum, the basement
membrane, and the muscular tissue of the mu-
cosa, all being supported and held together by
retiform lymphoid tissue.
The lacteals are in some cases double, and in
some animals multiple, but usually there is a
single vessel. Situated in the axis of the villus,
each commences by dilated cecal extremities
near to, but not quite at, the summit of the
villus. The walls are composed of a single layer
of endothelial cells.
The muscular fibers are derived from the mus-
cularis mucosir, and are arranged in longitudinal
bundles around the lacteal vessel, extending from
the base to the summit of the villus, and giving
off, laterally, individual muscle cells, which are
enclosed by the reticulum, and by it are attached
to the basement-membrane and to the lacteal.
The bloodvessels (Fig. 1061) form a plexus
under the basement membrane, and are enclosed
in the reticular tissue.
These structures are surrounded by the base-
mcnt membrane, which is made up of a stratum
of endothehal cells, and upon this is placed a layer of columnar epithelium, the characteristics of
which have been described. The retiform tissue forms a net- work (Fig. lOdO) in the meshes
of which a number of leucocytes are found.
The intestinal glands (glanduUe intestinales [Lieberkuhni]; crypts of Lieberkiihn) (Fig. 1062) are
Large
circular
vessel
Fig. 1064. — Transverse section through the equatorial
plane of three aggregated lymphatic nodules from the
rabbit.
THE SMALL INTESTINE
1175
found in considerable numbers over every part of the mucous membrane of the small intestine.
They consist of minute tubular depressions of the mucous membrane, arranged perpendicularly to
the surface, ujjon which they open by small circular apertures. They may be seen with the aid
Fig. 1065
Fig. 1066
Three feet.
Six feet.
Fig. 1067
Fig. 1068
Nine feet.
Twelve feet.
Fig. 1069
Fig 1070
Seventeen feet.
Twenty feet.
FiGf. 1065, 1066, 1067, 1068, 1069, 1070. — Diagrams showing the arrangement and variations of the loops of the
mesenteric vessels for various segments of the small intestine of average length. Nearest the duodenum the mesenteric
loops are primary, the vasa recta are long and regular in distribution, and the translucent spaces (lunettes) are extensive.
Toward the ileocolic junction, secondary and tertiary loops are observed, the vessels are smaller and become obscured
by numerous fat-tabs. (After Monks.)
1176
SPLANCHNOLOGY
of a lens, their orifices appearing as minute dots scattered between the villi. Their walls are
thin, consisting of a basement membrane lined by columnar epithelium, and covered on their
exterior by capillary vessels.
The duodenal glands {glandulcr duodenales [Brutmeri]; Brunner's glands) are limited to the
duodenum (Fig. 1058), and are found in the submucous areolar tissue. They are largest and most
numerous near the pylorus, forming an almost complete layer in the superior portion and
upper half of the descending portions of the duodenum. They then begin to diminish in
number, and practically disappear at the junction of the duodenum and jejunum. They are
small compound acinotubular glands consisting of a nvunber of alveoU lined by short columnar
epithelium and opening by a single duct on the inner surface of the intestine.
The solitary lymphatic nodules (nodidi lymphatici soUtarii; solitary glands) are found scattered
throughout the mucous membrane of the small intestine, but are most numerous in the lower
part of the ileum. Their free surfaces are covered with rudimentary viUi, except at the sum-
mits, and each gland is surrounded by the openings of the intestinal glands. Each consists of a
dense interlacing retiform tissue closely packed with lymph-corpuscles, and permeated with an
abundant capillary network. The interspaces of the retiform tissue are continuous with larger
lymph spaces which surround the gland, through which they communicate with the lacteal
system. They are situated partly in the submucous tissue, partly in the mucous membrane,
where they form slight projections of its epithelial layer (see Fig. 1082).
The aggregated lymphatic nodules {noduli lymphatici aggrcgati; Peyer's patches; Peyer's glands;
agminated follicles; tonsillo' intestinales) (Fig. 1063) form circular or oval patches, from twenty
to thirty in number, and varying in length from 2 to 10 cm. They are largest and most numerous
in the ileum. In the lower part of the jejunum they are small, circular, and few in number.
They are occasionally seen in the duodenum. Thej^ are placed lengthwise in the intestine, and
are situated in the portion of the tube most distant from the attachment of the mesentery. Each
patch is formed of a group of soUtary h-mphatic nodules covered with mucous membrane, but
the patches do not, as a rule, possess villi on their free surfaces. They are best marked in the
young subject, become indistinct in middle age, and sometimes disappear altogether in
advanced life. They are freely supphed with bloodvessels (Fig. 1064), which form an abundant
plexus around each follicle and give off fine branches permeating the hinphoid tissue in the
interior of the follicle. The lymphatic plexuses are especially abundant around these patches.
Vessels and Nerves. — The jejunum and ileum are supplied by the superior mesenteric artery,
the intestinal branches of which, having reached the attached border of the bowel, run between
the serous and muscular coats, with frequent in-
osculations to the free border, where they also
anastomose with other branches running around
the opposite surface of the gut. From these
vessels numerous branches are given off, which
pierce the muscular coat, supplying it and forming
an intricate plexus in the submucous tissue.
From this plexus minute vessels pass to the glands
and viUi of the mucous membrane. The veins
have a similar course and arrangement to the
Fig. 1071. — The myenteric plexus from the rabbit.
X 50.
Fig. 1072. — The plexus of the submucosa from the
rabbit X50.
arteries. The lymphatics of the small intestine (lacteals) are arranged in two sets, those of the
mucous membrane and those of the muscular coat. The lymphatics of the villi commence in
these structures in the manner described above. They form an intricate plexus in the mucous
and submucous tissue, being joined by the lymphatics from the l3-mph spaces at the bases of
the soHtary nodules, and from this pass to larger vessels at the mesenteric border of the gut. The
IjTTiphatics of the muscular coat are situated to a great extent between the two layers of muscular
fibers, where they form a close plexus; throughout their course they communicate freely with
THE LARGE INTESTIXE 1177
the lymphatics from the mucous membrane, and empty themselves in the same manner as
these into the origins of the lacteal vessels at the attaclicd border of the gut.
The nerves of the small intestines are derived from the plexuses of sympathetic nerves around
the superior mesenteric artery. From this source they run to the myenteric plexus (Auerbach's
plexus) (Fig. 1071) of nerves and ganglia situated between the circular and longitudinal mus-
cular fibers from which the nervous branches are distriljuted to the muscular coats of the
intestine. From tliis a secondary plexus, the plexus of the submucosa {Meissner's plexus)
(Fig. 1072) is derived, and is formed by branches which have perforated the circular nuiscular
fibers. This plexus hes in the submucous coat of the intestine; it also contains ganglia from
which nerve fibers pass to the muscularis mucosae and to the mucous memljrane. The nerve
bimdles of the submucous plexus are finer tlian those of the myenteric plexus.
The Large Intestine tlntestinum Crassum). .
The large intestine extends from the end of tlie ilenni to the anus. It is about
1.5 meters long, being one-fifth of the whole extent of the intestinal canal. Its
caliber is largest at its commencement at the cecum, and gradually diminishes
as far as the rectum, where there is a dilatation of considerable size just above
the anal canal. It differs from the small intestine in its greater caliber, its more
fixed position, its sacculated form, and in possessing certain appendages to its
external coat, the appendices epiploicse. Further, its longitudinal muscular fibers
do not form a continuous layer around the gut, but are arranged in three longitudinal
bands or taeniae. The large intestine, in its course, describes an arch which sur-
rounds the ct)nvt)lutions of the small intestine. It commences in the right iliac
region, in a dilated part, the cecum. It ascends through the right lumbar and hypo-
chondriac regions to the under surface of the liver; it here takes a bend, the right
colic flexure, to the left and passes transversely across the abdomen on the confines
of the epigastric and umbilical regions, to the left hypochondriac region; it then
bends again, the left colic flexure, and descends through the left lumbar and iliac
regions to the pelvis, where it forms a bend called the sigmoid fiexm-e; from this it
is continued along the posterior wall of the pelvis to the anus. The large intestine
is divided into the cecimi, colon, rectum, and anal canal.
The Cecum (intcstinmn caecum) (Fig. 1073), the commencement of the large
intestine, is the large blind pouch situated below the colic valve. Its blind end
is directed downward, and its open end upward, communicating directly with the
colon, of which this blind pouch appears to be the beginning or head, and hence the
old name of caput caecum coli was applied to it. Its size is variously estimated by
different authors, but on an average it may be said to be 6.25 cm. in length and 7.5 in
breadth. It is situated in the right iliac fossa, above the lateral half of the inguinal
ligament : it rests on the Iliacus and Psoas major, and usually lies in contact with the
anterior abdominal wall, but the greater omentum and, if the cecum be empty,
some coils of small intestine may lie in front of it. As a rule, it is entirely enveloped
by peritoneum, but in a certain number of cases (5 per cent.. Berry) "the peritoneal
covering is not complete, so that the upper part of the i)()sterior surface is uncovered
and connected to the iliac fascia by connective tissue. The cecum lies quite free
in the abdominal cavity- and enjoys a considerable amount of movement, so that
it may become herniated down the right inguinal canal, and has occasionally
been found in an inguinal hernia on the left side. The cecum varies in shape, but,
according to Treves, in man it may be classified under oiie of four types. In early
fetal life it is short, conical, and broad at the base, with its apex turned upward
and medialward toward the ileocolic junction. It then resembles the cecum of some
monkeys, e. g., mangabey monkey. As the fetus grows the cecum increases in
length more than in breadth, so that it forms a longer tube than in the primitive
form and without the broad base, but with the same inclination of the apex toward
the ileocolic junction. This form is seen in other monkeys, e. g., the spider monkey.
As development goes on, the lower part of the tube ceases to grow and the upper
1178
SPLANCHNOLOGY
part becomes greatly increased, so that at birth there is a narrow tube, the vermi-
form process, hanging from a conical projection, the cecum. This is the infantile
form, and as it persists throughout life in about 2 per cent, of cases, it is regarded
by Treves as the first of his four types of human ceca. The cecum is conical and
the appendix rises from its apex. The three longitudinal bands start from the
appendix and are equidistant from each other. In the second type, the conical
cecum has become quadrate by the growing out of a saccule on either side of the
anterior longitudinal band. These saccules are of equal size, and the appendix
arises from between them, instead of from the apex of a cone. This type is found
in about 3 per cent, of cases. The third type is the normal type of man. Here
the two saccules, which in the second type were uniform, have grown at unequal
rates: the right with greater rapidity than the left. In consequence of this an
apparently new apex has been formed by the growing doAvnward of the right sac-
cule, and the original apex, with the appendix attached, is pushed over to the left
Terminal part of ileocolic artery
Cecal branches
Ileal branches
Appendicular
artery
^•^"^m process
Fig. 1073. — The cecum and vermiform process, with their arteries.
toward the ileocolic junction. The three longitudinal bands still start from the
base of the vermiform process, but they are now no longer equidistant from each
other, because the right saccule has grown between the anterior and postero-
lateral bands, pushing them over to the left. This type occurs in about 90 per
cent, of cases. The fourth type is merely an exaggerated condition of the third;
the right saccule is still larger, and at the same time the left saccule has become
atrophied, so that the original apex of the cecum, with the vermiform process, is
close to the ileocolic junction, and the anterior band courses medialward to the
same situation. This type is present in about 4 per cent, of cases.
The Vermiform Process or Appendix (processus vermiformis) (Fig. 1073) is a long,
narrow, worm-shaped tube, which starts from what was originally the apex of the
cecum, and may pass in one of several directions: upward behind the cecum; to
the left behind the ileum and mesentery; or downward into the lesser pelvis. It
varies from 2 to 20 cm. in length, its average being about 8.3 cm. It is retained
in position by a fold of peritoneum (mesenteriole), derived from the left leaf of
THE LARGE INTESTINE
1179
the mesentery. This fold, in the majority of cases, is more or less triangular in
shape, and as a rule extends along the entire length of the tube. Between its two
layers and close to its free margin lies tiie appendicular artery (Fig. 1073) . The canal
of the vermiform process is small, extends throughout the whole length of the tube,
and communicates with the cecum by an orifice which is placed below and behind
the ileocecal opening. It is sometimes guarded by a semilunar valve formed by a
fold of mucous membrane, but this is by no means constant.
Structure. — The coats of the vermiform process are the same as those of the intestine: serous,
muscular, submucous, and mucous. The serous coat forms a complete investment for the tube,
except along the narrow line of attachment of its niesenteriole in its proximal two-thirds. The
longitudinal muscular fibers' do not form three bands as in the greater part of the large intestine,
but invest the whole organ, except at one or two points where both the longitudinal and circular
fibers are deficient so that the peritoneal and submucous coats are contiguous over small areas.
The circular muscle fibers form a much thicker layer than the longitudinal fibers, and are
separated from them by a small amount of connective tissue. The submucous coat is well
marked, and contains a large number of masses of lymphoid tissue which cause the mucous
membrai'C to bulge into the lumen and so render the latter of small size and irregular shape.
The mucous membrane is lined by columnar epithelium and resembles that of the rest of the
large intestine, but the intestinal glands are fewer in number (Fig. 1074).
- — Muscular coat
Cohimnar
epithelium
Glands
Lymph nodule
Fig. 1074. — Transverse section of human vermiform process. X 20.
The Colic Valve (valmilacoli; ileocecal valve) (Fig. 1075). — The lower end of the ileum
ends by opening into the medial and back part of the large intestine, at the point
of junction of the cecum with the colon. The opening is guarded by a valve,
consisting of two segments or lips, which project into the lumen of the large intes-
tine. If the intestine has been inflated and dried, the lips are of a semilunar shape.
The upper one, nearly horizontal in direction, is attached by its convex border
to the line of junction of the ileum with the colon; the lower lip, which is longer
and more concave, is attached to the line of junction of the ileum with the cecum.
At the ends of the aperture the two segments of the valve coalesce, and are continued
as narrow membranous ridges around the canal for a short distance, forming the
frenula of the valve. The left or anterior end of the aperture is rounded; the right
or posterior is narrow^ and pointed. In the fresh condition, or in specimens which
have been hardened in situ, the lips project as thick cushion-like folds into the lumen
of the large gut, while the opening between them may present the appearance of a
slit or may be somewhat oval in shape.
1180
SPLANCHNOLOGY
Each lip of the valve is formed by a reduplication of the mucous membrane
and of the circular muscular fibers of the intestine, the longitudinal fibers and
peritoneum being continued uninterruptedly from the small to the large imestine.
The surfaces of the valve directed toward the ileum are covered with villi, and
present the characteristic structure of the mucous membrane of the small intestine;
while those turned toward the large intestine are destitute of villi, and marked
with the orifices of the numerous tubular glands peculiar to the mucous membrane
of the large intestine. These differences in structure continue as far as the free
margins of the valve. It is generally maintained that this valve prevents reflux
from the cecum into the ileum, but in all probability it acts as a sphincter around
the end of the ileum and prevents the contents of the ileum from passing too
quickly into the cecum.
The Colon is divided into four parts: the ascending, transverse, descending, and
sigmoid.
Upper segment
of colic valvt
Opening of ileum
Lower segment
of colic valve
Probe in vermiforrrh
process
Fig. 1075. — Interior of the cecum and lower end of ascending colon, showing colic valve.
The Ascending Colon (colon ascendens) is smaller in caliber than the cecum, with
which it is continuous. It passes upward, from its commencement at the cecum,
opposite the colic valve, to the under surface of the right lobe of the liver, on the
right of the gall-bladder, where it is lodged in a shallow depression, the colic impres-
sion; here it bends abruptly forward and to the left, forming the right colic (hepatic)
flexure (Fig. 1056) . It is retained in contact with the posterior wall of the abdomen
by the peritoneum, which covers its anterior surface and sides, its posterior surface
being connected by loose areolar tissue with the Iliacus, Quadratus lumborum,
aponeurotic origin of Transversus abdominis, and with the front of the lower and
lateral part of the right kidney. Sometimes the peritoneum completely invests
it, and forms a distinct but narrow mesocolon.^ It is in relation, in front, with the
convolutions of the ileum and the abdominal parietes.
The Transverse Colon (colon transversuvi) the longest and most movable part of
the colon, passes with a downward convexity from the right hypochondriac region
across the abdomen, opposite the confines of the epigastric and umbilical zones,
into the left hypochondriac region, where it curves sharply on itself beneath the
lower end of the spleen, forming the left colic (splenic) flexure. In its course it
describes an arch, the concavity of Avhich is directed backward and a little upward ;
toward its splenic end there is often an abrupt U-shaped curve which may descend
' Treves states that, after a careful examination of one hundred subjects, he found that in fifty-two there was neither
an ascending nor a descending mesocolon. In twenty-two there was a descending mesocolon, but no trace of a corre-
sponding fold on the other side. In fourteen subjects there was a mesocolon to both the ascending and the descending
segments of the bowel; while in the remaining twelve there was an ascending mesocolon, but no corresponding fold
on the left side. It follows, therefore, that in performing lumbar colotomy a mesocolon may be expected upon the left
side in 3G per cent, of all cases, and on the right in 26 per cent. — The Anatomy of the Intestinal Canal and Peritoneum
in Man, 1885, p. 55.
THE LARGE INTESTINE
1181
lower than the main curve. It is almost completely invested by peritoneum, and
is connected to the inferior border of the pancreas by a large and wide duplicature
of that membrane, the transverse mesocolon. It is in relation, by its upper surface,
with the liver and gall-l)hi(LikT, the greater curvature of the stomach, and the
lower end of the spleen; by its under surface, with the small intestine; by its ante-
rior surface, with the anterior layers of the greater omentum and the abdominal
parietes; its posterior surface is in relation from right to left with the descending
portion of the duodenum, the head of the pancreas, and some of the convolutions
of the jejunum and ileum.
The left colic or splenic flexure (Fig. 1056) is situated at the junction of the trans-
verse and descending parts of the colon, and is in relation with the lower end of the
spleen and the tail of the pancreas; the flexure is so acute that the end of the trans-
verse colon usually lies in contact with the front of the descending colon. It lies
at a higher level than, and on a plane posterior to, the right colic flexure, and is
attached to the diaphragm, opposite the tenth and eleventh ribs, by a peritoneal
fold, named the phrenicocolic ligament, which assists in supporting the lower end
of the spleen (see page 11 58).
Fig. 1076.
Femoral nerve
Femoral vessels
Peritoneum
Levator ani muscle
-Iliac colon, sigmoid or pelvic colon, and rectum seen from the front, after removal of pubic bones
and bladder.
The Descending Colon^ {colon descendens) passes downward through the left
hypochondriac and lumbar regions along the lateral border of the left kidney.
At the lower end of the kidney it turns medialward toward the lateral border of
the Psoas, and then descends, in the angle between Psoas and Quadratus lumborum,
to the crest of the ilium, where it ends in the iliac colon. The peritoneum covers
its anterior surface and sides, while its posterior surface is connected by areolar
tissue with the lower and lateral part of the left kidney, the aponeurotic origin of
• In the Basle nomenclature the descending colon is the portion between the left colic flexure and the superior aper-
ture of the lesser pelvis; it is, however, convenient to descnbe its lowest part as the iliac colon.
1182
SPLANCHNOLOGY
the Transversus abdominis, and the Quadratuskimborum (Fig. 1056). It is smaller
in caliber and more deeply placed than the ascending colon, and is more frequently
covered with peritoneum on its posterior surface than the ascending colon (Treves).
In front of it are some coils of small intestine.
The Iliac Colon (Fig. 107G) is situated in the left iliac fossa, and is about 12 to
15 cm. long. It begins at the level of the iliac crest, where it is continuous with
the descending colon, and ends in the sigmoid colon at the superior aperture of the
lesser pelvis. It curves downward and medialward in front of the Iliacus and Psoas,
and, as a rule, is covered by peritoneum on its sides and anterior surface only.
Fig. 1077. — The posterior aspect of the rectum exposed by removing the loner part of the sacrum and the coccyx.
The Sigmoid Colon {colon sigmoidcuvi; pelvic colon; sigmoid flexure) (Fig. 1076)
forms a loop which averages about 40 cm. in length, and normally lies within the
pelvis, but on account of its freedom of movement it is liable to be displaced into
the abdominal cavity. It begins at the superior aperture of the lesser pelvis,
where it is continuous with the iliac colon, and passes transversely across the front
of the sacrum to the right side of the pelvis; it then curves on itself and turns
toward the left to reach the middle line at the level of the third piece of the sacrum,
where it bends downward and ends in the rectum. It is completely surrounded by
peritoneum, which forms a mesentery (sigmoid mesocolon), which diminishes in
THE LARGE INTESTINE
1183
length from the center toward the ends of the loop, where it disappears, so that the
loop is fixed at its junctions with the iliac colon and rectum, but enjoys a consider-
able range of movement in its central portion. Behind the sigmoid colon are the
external iliac vessels, the left Piriformis, and left sacral plexus of nerves; in front,
it is separated from the bladder in the male, and the uterus in the female, by some
coils of the small intestine.
The Rectum {intesiin inn rectum) (Fig. 1077) is continuous above with the sigmoid
colon, while below it ends in the anal canal. From its origin at the level of the
third sacral vertebra it passes downward, lying in the sacrococcygeal curve, and
extends for about 2.5 cm. in front of, and a little below, the tip of the coccyx,
as far as the apex of the prostate. It then bends sharply backward into the anal
canal. It therefore presents two antero-posterior curves: an upper, with its con-
vexity backward, and a lower, with its convexity forward. Two lateral curves are
also described, one to the right opposite the junction of the third and fourth sacral
vertebrae, and the other to the left, opposite the left sacrococcygeal articulation;
they are, however, of little importance. The rectum is about 12 cm. long, and at
its commencement its caliber is similar to that of the sigmoid colon, but near its
termination it is dilated to form the rectal ampulla. The rectum has no sacculations
comparable to those of the colon, but when the lower part of the rectum is con-
tracted, its mucous membrane is thrown into a number of folds, which are longitudi-
nal in direction and are effaced by the distension of the gut. Besides these there
are certain permanent transverse folds, of a semilunar shape, known as Houston's
valves (Fig. 1078). They are usually three in number ; sometimes a fourth is found,
and occasionally only two are present. One is
situated near the commencement of the rectum,
on the right side; a second extends inward from
the left side of the tube, opposite the middle of
the sacrum; a third, the largest and most con-
stant, projects backward from the forepart of
the rectum, opposite the fundus of the urinary
bladder. When a fourth is present, it is situated
nearly 2.5 cm. above the anus on the left and
posterior wall of the tube. These folds are about
12 mm. in width, and contain some of the
circular fibers of the gut. In the empty state of
the intestine they overlap each other, as Houston
remarks, so effectually as to require considerable
maneuvering to conduct a bougie or the finger
along the canal. Their use seems to be, "to
support the weight of fecal matter, and prevent
its urging toward the anus, where its presence
always excites a sensation demanding its dis-
charge.^
Transverse
rectal folds
Ilectal columns
Sphincter ani
intermis
Sphincter ani
externus
Fig. 1078. — Coronal section of rectum and
anal canal.
The peritoneum is related to the upper two-
thirds of the rectum, covering at first its front
and sides, but lower down its front only; from
the latter it is reflected on to the seminal vesicles
in the male and the posterior vaginal wall in the
female.
The level at which the peritoneum leaves the anterior wall of the rectum to be
reflected on to the viscus in front of it is of considerable importance from a surgical
' Paterson ("The Form of the Rectum," Journal of Anatomy and Physiology, vol. xliii) utilizes the third fold for
the purpose of dividing the rectum into an upper and a lower portion; he considers the latter "to be just as much a
duct as the narrower anal canal below, " and maintains that, under normal conditions, it does not contain feces except
-during the act of defecation.
1184
SPLANCHNOLOGY
point of view, in connection with the removal of the lower part of the rectum. It
is higher in the male than in the female. In the former the height of the recto-
vesical excavation is about 7.5 cm., i. e., the height to which an ordinary index
finger can reach from the anus. In the female the height of the rectouterine
excavation is about 5.5 cm. from the anal orifice. The rectum is surrounded by
a dense tube of fascia derived from the
fascia endopelvina, but fused behind
with the fascia covering the sacrum
and coccyx. The facial tube is loosely
attached to the rectal wall by areolar
tissue in order to allow of distension of
the viscus.
Relations of the Rectum. — The upper part
of the rectum is in relation, behind, with the
superior hemorrhoidal vessels, the left Piri-
formis, and left sacral plexus of nerves, which
separate it from the pelvic surfaces of the
sacral vertebra?; in its lower part it hcs directly
on the sacrum, coccyx, and Levatores ani, a
dense fascia alone intervening; in front, it is
separated above, in the male, from the fundus
of the bladder; in. the female, from the intes-
tinal surface of the uterus and its appendages,
by some convolutions of the small intestine,
and frequently by the sigmoid colon ; below, it
is in relation in the male wi th the triangular
portion of the fundus of the bladder, the vesic-
ulae seminales, and ductus deferentes, and
more anteriorly with the posterior surface of
the prostate; in the female, with the poste-
rior wall of the vagina.
Fig. 1079. — Coronal section through the anal canal.
(Symington.) i?. Cavity of urinary bladder. F.D. Ductus
deferens. S.V. Seminal vesicle. R. Second part of
rectum. A.C. Anal canal. L.A. Levator ani. I.S.
Sphincter ani internus. E.S. Sphincter ani externus.
The Anal Canal {yarsanalis recti) (Figs. 1079, 1080, 1081), or terminal portion of the
large intestine, begins at the level of the apex of the prostate, is directed downward
and backward, and ends at the anus. It forms an angle with the lower part of
LONGITUDINAL
MUSCLE FIBRES
OF RECTUM
RUGiC OF
MUCOUS
MEMBRANE
COLUMNS OF
MORGAGNl
PA
LEVATO
INTERNAL
SPHINCTER
ANAL CANALS H )S
ANAL VALVES
Fig. 1080. — The interior of the anal canal and lower part of the rectum, showing the columns of Morgagni and the anal
valves between their lower ends. The columns were more numerous in the specimen than usual. (Cunningham.)
the rectum, and measures from 2.5 to 4 cm. in length. It has no peritoneal cov-
ering, but is invested by the Sphincter ani internus, supported by the Levatores
ani, and surrounded at its termination by the Sphincter ani externus. In the
V,
THE LARGE INTESTINE
1185
empty condition it presents the appearance of an antero-posterior lonfjituflinal
slit. Behind it is a mass of muscuhir and fibrous tissue, the anococcygeal body
(Symington) ; in front of it, in the male, but separated by connective tissue from
it, are the membranous portion and bulb of the urethra, and the fascia of the
urogenital diaphragm; and in the female it is separated from the lower end of
the vagina by a mass of muscular and fibrous tissue, named tlie perineal body.
MUCOUS
MEMBRANE
DILATATION
OF VEINS~iiiir
COLUMNS OF.
MORGAGNI
VALVE OF
MORGAGN
HILTON'S
WHITE LINE
SKIN <
MUSCULAR WALL
OF RECTUM
NTERNAL HEMOR-
RHOIDAL PLEXUS
DILATATION
OF VEIN
COMMUNICATION BE-
TWEEN INTERNALAND
EXTERNAL HEMOR-
RHOIDAL PLEXUS
INTERNAL
SPHINCTER
EXTERNAL
SPHINCTER
LONGITUDINAL
TENDINOUS FIBRES
SUBCUTANEOUS
CELLULAR TISSUE
Fig. 1081. — Inner wall of the lower end of the rcrtum and anus. On the right the mucous membrane has been
removed to show the dilatation of the veins and how they pass through the muscular wall to anastomose with the
external hemorrhoidal plexus. (Luschka.)
The lumen of the anal canal presents, in its upper half, a number of vertical
folds, produced by an infolding of the mucous membrane and some of the mus-
cular tissue. They are known as the rectal columns [Morgagni] (Fig. 1078), and are
Leucocytes in
epithelium
Gland
3Iuscularis
mucosce
Germ-centre
Solitary lymphatic nodule
Fig. 1082. — Section of mucous membrane of human rectum. (Sobotta.) X 60.
separated from one another by furrows (rectal sinuses), which end below in small
valve-like folds, termed anal valves, which join together the lower ends of the
rectal columns.
Structure of the Colon. — The large intestine has four coats: serous, muscular, areolar, and
mucous.
75
1186
SPLANCHNOLOGY
DAL
OIOAL
The serous coat {tunica serosa) is derived from the peritoneum, and invests the different
portions of the large intestine to a variable extent. The cecum is completely covered by the
serous membrane, except in about 5 per cent, of cases wliere the upper part of the posterior
surface is uncovered. The ascending, descending, and iliac parts of the colon are usually covered
only in front and at the sides; a variable amount of the posterior surface is uncovered.^ The
transverse colon is almost completely invested, the parts corresponding to the attachment of
the greater omentmn and transverse mesocolon being alone excepted. The sigmoid colon is
entirely surrounded. The rectum is covered above on its anterior surface and sides; below,
on its anterior aspect only; the anal canal is entirely devoid of any serous covering. In the
course of the colon the peritoneal
coat is thro^\Ti into a number of
small pouches filled with fat, called
appendices epiploicse. They are
most nmuerous on the transverse
colon.
The muscular coat (tunica jhus-
cularis) consists of an external longi-
tudinal, and an internal circular,
layer of non-striped muscular fibers.
The longitudinal fibers do not
form a continuous layer over the
whole surface of the large intestine.
In the cecum and colon they are
especially collected into three flat
longitudinal bands {tn'tiai coli),
each of about 12 mm. in width;
one, the posterior, is placed along
the attached border of the intestine;
the anterior, the largest, corre-
sponds along the arch of the colon
to the attachment of the greater
omentum, but is in front in the
ascending, descending, and iliac
parts of the colon, and in the sig-
moid colon; the third, or lateral
band, is found on the medial side
of the ascending and descending
parts of the colon, and on the under
aspect of the transverse colon.
These bands are shorter than the
other coats of the intestine, and
serve to produce the sacculi which
are characteristic of the cecum and
colon; accordingly, when they are
dissected off, the tube can be length-
ened, and its sacculated character
disappears. In the sigmoid colon
the longitudinal fibers become more
scattered; and around the rectum
they spread out and form a laj^er,
which completely encircles this por-
tion of the gut, but is thicker on
the anterior and posterior surfaces,
where it forms two bands, than on
the lateral surfaces. In addition,
two bands of plain muscular tissue arise from the second and third coccygeal vertebra^, and
pass dowTiward and forward to blend with the longitudinal muscular fibers on the posterior
wall of the anal canal. These are knowTi as the Rectococcygeal muscles.
The circular fibers form a thin layer over the cecum and colon, being especially accumulated
in the intervals between the saccuh; in the rectum they form a thick layer, and in the anal canal
they become numerous, and constitute the Sphincter ani internus.
The areolar coat (tela submucosa; submucous coat) cormects the muscular and mucous layers
closely together.
The mucous membrane {tunica mucosa) in the cecum and colon, is pale, smooth, destitute
of villi, and raised into numerous crescentic folds which correspond to the intervals between
1 See footnote, p. 1183.
MIDDLE
HEMORRHOIDAI
ARTERY
RIOR
ORRHOIDAL
RY
Fig. 1083. — The bloodvessels of the rectum and anus, showing the dis-
tribution and anastomosis on the posterior surface near the termination
of the gut. (Poirier and Charpy)
THE LARGE INTESTINE
1187
the sacculi. In the rectum it is thicker, of a tlarker color, more vascular, and connected loosely
to the muscular coat, as in the esophagus.
As in the small intestine, the mucous membrane (Fig. 1082) consists of a muscular layer, the
muscularis mucosae; a quantity of retiform tissue in which the vessels ramifj'; a ba.sement mem-
brane and epithelium which is of the columnar variety, and resembles the epithchum found in
the small intestine. The mucous membrane of the large intestine presents for examination glands
and solitary lymphatic nodules.
The glands of the great intestine are minute tubular prolongations of the mucous membrane
arranged perpendicularly, side by side, over its entire surface; they are longer, more numerous,
and placed in nmch closer apposition than those of the small intestine; and they open by minute
rounded orifices upon the surface, giving it a cribriform appearance. Each gland is lined by
short columnar epithelium and contains numerous goblet cells.
The solitary lymphatic nodules {noduli lymphatic solitarii) (Fig. 1082) of the large intestine
are most abundant in the cecum and vermiform process, but are irregularly scattered also over
the rest of the intestine. They are similar to those of the small intestine.
Vessels and Nerves. — The arteries supplying the colon are derived from the coUc and sigmoid
branches of the mesenteric arteries. They give off large branches, which ramifj'' between and
supply the muscular coats, and after dividing into small vessels in the submucous tissue, pass
to the mucous membrane. The rectum is supplied by the superior hemorrhoidal branch of the
inferior mesenteric, and the anal canal by the middle hemorrhoidal from the hypogastric, and
the inferior hemorrhoidal from the internal pudendal artery. The superior hemorrhoidal, the
continuation of the inferior mesenteric, divides into two branches, which run down either side
of the rectum to within about 12.5 cm. of the anus; they here spht up into about six branches
which pierce the muscular coat and descend between it and the nmcous membrane in a longi-
tudinal direction, parallel with each other as far as the Sphincter ani internus, where they anas-
tomose with the other hemorrhoidal arteries and form a series of loops around the anus. The
veins of the rectmn commence in a plexus of vessels which surrounds the anal canal* In the
vessels forming this plexus are smaller saccular dilatations just within the margin of the anus;
from the plexus about six vessels of considerable size are given off. These ascend between the
muscular and mucous coats for about 12.5 cm., running parallel to each other; they then
pierce the muscular coat, and, by their union, form a single trunk, the superior hemorrhoidal
vein. This arrangement is termed the hemorrhoidal plexus; it communicates with the tribu-
taries of the middle and inferior hemor-
rhoidal veins, at its commencement,
and thus a communication is estab-
Ushed between the systemic and portal
circulations. The lymphatics of the large
intestine are described on page 711.
The nerves are derived from the sym-
pathetic plexuses around the branches
of the superior and inferior mesenteric
arteries. They are distributed in a
similar way to those found in the small
intestine.
Congenital Hernia. — There are some
varieties of oblique inguinal hernia
(Fig. 1084) depending upon congenital
defects in the saccus vaginalis, the pouch
of peritoneum which precedes the
descent of the testis. Normally this
pouch is closed before birth, closure
commencing at two points, viz., at the
abdominal inguinal ring and at the top
of the epididymis, and gradually ex-
tending until the whole of the inter-
vening portion is converted into a
fibrous cord. From faihire in the com-
pletion of this process, variations in the
relation of the hernial protrusion to the
testis and tunica vaginalis are pro-
duced; these constitute distinct varieties of inguinal hernia, viz., the hernia of the funicular
process and the complete congenital variety.
Where the saccus vaginalis remains patent throughout, the cavity of the tunica vaginalis
communicates directly with that of the peritoneimi. The intestine descends along this pouch
into the cavity of the tunica vaginahs which constitutes the sac of the hernia, and the gut hes
in contact with the testis. Though this form of hernia is termed complete congenital, the term
Complete oblique inguinal
Complete congenital
Fig. 1084.
Incomplete congenital
-Varieties of oblique inguinal hernia.
1188
SPLANCHNOLOGY
does not imply that the hernia existed at birth, but merely that a condition is present which
may allow of the descent of the hernia at any moment. As a matter of fact, congenital hemiae
frequent]}^ do not appear until adult life.
Where the processus vaginahs is occluded at the lower point onty, i. e., just above the testis,
the intestine descends into the pouch of peritoneum as far as the testis, but is prevented
from entering the sac of the tunica vaginahs by the septum which has formed between it and the
pouch. This is known as hernia into the funicular process or incomplete congenital hernia; it
differs from the former in that instead of enveloping the testis it lies above it.
The Liver (Hepar).
The liver, the largest gland in the body, has both external and internal secretions,
which are formed in the hepatic cells. Its external secretion, the bile, is collected
after passing through the bile capillaries by the bile ducts, which j(nn like the twigs
and branches of a tree to form two large ducts that unite to form the hepatic duct.
The bile is either carried to the gall-bladder by the cystic duct or poured directly
into the duodenum by the common bile duct where it aids in digestion. The internal
secretions are concerned with the metabolism of both nitrogenous and carbohydrate
materials absorbed from the intestine and carried to the liver by the portal ^ein.
The carbohydrates are stored in the hepatic cells in the form of glycogen which is
secreted in the form of sugar directly into the blood stream. Some of the cells
lining the blood capillaries of the liver are concerned in the destruction of red blood
corpuscles. It is situated in the upper and right parts of the abdominal cavity,
occupying almost the whole of the right hypochondriiun, the greater part of the
epigastrium, and not imcommonly extending into the left hypoch(Midrium as far
as the mammillary line. In the male it weighs from 1 .4 to 1 .0 kilogm.. in the female
from 1.2 to 1.4 kilogm. It is relatively much larger in the fetus than in the adult,
constituting, in the former, about one-eighteenth, and in the latter about one
thirty-sixth of the entire body weight. Its greatest transverse measurement is
from 20 to 22.5 cm. Vertically, near its lateral or right surface, it measures about
15 to 17.5 cm., while its greatest antero-posterior diameter is on a level with the
upper end of the right kidney, and is from 10 to 12.5 cm. Opposite the vertebral
column its measurement from before backward is reduced to about 7.5 cm. Its
consistence is that of a soft solid; it is friable, easily lacerated and highly vascular;
its color is a dark reddish brown, and its specific gravity is 1.05.
To obtain a correct idea of its shape it must be hardened in situ, and it will
then be seen to present the appearance of a wedge, the base of which is directed
to the right and the thin edge toward the left. Symington describes its shape
as that "of a right-angled triangular prism with the right angle rounded off."
Surfaces. — The liver possesses three surfaces, viz., superior, inferior and posterior.
A sharp, well-defined margin divides the inferior from the superior in front; the other
margins are rounded. The superior surface is attached to the diaphragm and
anterior abdominal wall by a triangular or falciform fold of peritoneum, the falci-
form ligament, in the free margin of which is a rounded cord, the ligamentum teres
(obliterated umbilieal rein). The line of attachment of the falciform ligament
divides the liver into two parts, termed the right and left lobes, the right being much
the larger. The inferior and posterior surfaces are dividefl into fourlobes by five
fossa?, which are arranged in the form of the letter H. The left limb of the H marks
on these surfaces the division of the liver into right and left lobes; it is known as the
left sagittal fossa, and consists of two parts, viz., the fossa for the umbilical vein m
front and the fossa for the ductus venosus behind. The right limb of the H is formed
in front by the fossa for the gall-bladder, and behind by the fossa for the inferior vena
cava; these two fosste are separated from one another by a band of liver substance,
termed the caudate process. The bar connecting the two limbs of the II is the
porta (transverse fissure) ; in front of it is the quadrate lobe, behind it the caudate lobe.
THE LIVER
1189
The superior surface (fades superior) (Pig. 1085) comprises a part of both lobes,
and, as a whole, is convex, and fits under the vault of the dia})hragni which in front
separates it on the right from the sixth to the tenth ribs and their cartilages, and
on the left from the seventh and eighth costal cartilages. Its middle i)art lies
behind the xiphoid process, and, in the angle between the di\erging rib cartilage
of opposite sides, is in contact with the abdominal wall. Behind this the diaphragm
separates the li\er from the lower part of the lungs and pleunF, the lieart and peri-
cardium and the right costal arches from the seventh to the ele\'^enth inclusive. It
is completely covered by i)eritoneum except along the line of attachment of the
falciform ligament.
Gall-bladder
Left triangvlar ligament
Bight triangvlar
ligament
Fig. lOSo. — The superior surface of the liver. (From model by His.)
The inferior surf ace {fades inferior; visceral surface) (Figs. 1086, 1087), is uneven,
concave, directed downward, backward, and to the left, and is in relation with
the stomach and duodenum, the right colic flexure, and the right kidnej' and supra-
renal gland. The surface is almost completely invested by peritoneum; the only
parts devoid of this covering are where the gall-bladder is attached to the liver,
and at the porta hepatis where the two layers of the lesser omentum are separated
from each other by the bloodvessels and ducts of the liver. The inferior surface
of the left lobe presents behind and to the left the gastric impression, moulded
over the antero-superior surface of the stomach, and to the right of this a rounded
eminence, the tuber omentale, which fits into the conca^"ity of the lesser curvature
of the stomach and lies in front of the anterior layer of the lesser omentum. The
under surface of the right lobe is divided into two unequal portions by the fossa
for the gall-bladder; the portion to the left, the smaller of the two, is the quadrate
lobe, and is in relation with the pyloric end of the stomach, the superior portion
of the duodeniun, and the transverse colon. The portion of the under surface of
the right lobe to the right of the fossa for the gall-bladder presents two impressions,
one situated behind the other, and separated by a ridge. The anterior of these
two impressions, the colic impression, is shallow and is produced by the right colic
flexure; the posterior, the renal impression, is deeper and is occupied by the upper
part of the right kidney and lower part of the right suprarenal gland. Medial
to the renal impression is a third and slightly marked impression, lying between it
and the neck of the gall-bladder. This is caused by the descending portion of the
1190
SPLANCHNOLOGY
duodenum, and is known as the duodenal impression. Just in front of the inferior
vena cava is a narrow strip of liver tissue, the caudate process, which connects
the right inferior angle of the caudate lobe to the under surface of the right lobe.
It forms the upper boundary of the epiploic foramen of the peritoneum.
Fossa for ductus venosus
Esophageal groove
Papillary ^
process ^*'^-^*-l^^
Hepatic artery / \
Portal vein / Pound ligament
Common bile duct
Fig. lOSG. — Inferior surface of the liver. (From model by His.)
The posterior surface {fades posterior) (Fig. 1087) is rounded and broad behind
the right lobe, but narrow on the left. Over a large part of its extent it is not
Esophageal groove
Fossa for
ductus venosus
Papillary Fossa for umbilical vein
process
Fig. 1087. — Posterior and inferior surfaces of the liver. (From model by His.
covered by peritoneum; this uncovered portion is about 7.5 cm. broad at its widest
part, and is in direct contact with the diaphragm. It is marked off from the upper
surface by the line of reflection of the upper layer of the coronary ligament, and
THE LIVER 1191
from the under surface by the Hue of reflection of the lower layer of the coronary
ligament. The central part of the postericrr surface presents a deep concavity
which is moulded on the vertebral column and crura of the diaphragm. To the
right of this the inferior vena cava is lodged in its fossa between the uncovered
area and the caudate lobe. Close to the right of this fossa and immediately above
the renal impression is a small triangular depressed area, the suprarenal impression,
the greater part of which is devoid of peritoneum; it lodges the right suprarenal
gland. To the left of the inferior vena cava is the caudate lobe, which lies between
the fossa for the vena cava and the fossa for the ductus venosus. Its low^er end
projects and forms part of the posterior boundary of the porta; on the right, it
is connected with the under surface of the right lobe of the liver by the caudate
process, and on the left it presents an elevation, the papillary process. Its posterior
surface rests upon the diaphragm, being separated from it merely by the upper
part of the omental bursa. To the left of the fossa for the ductus venosus is a
groove in which lies the antrum cardiacum of the esophagus.
The anterior border {margo anterior) is thin and sharp, and marked opposite
the attachment of the falciform ligament by a deep notch, the umbilical notch,
and opposite the cartilage of the ninth rib by a second notch for the fundus of the
gall-bladder. In adult males this border generally corresponds with the lower
margin of the thorax in the right mammillary line; but in women and children it
usually projects below the ribs.
The left extremity of the liver is thin and flattened from above downward.
Fossae. — The left sagittal fossa (fossa sagittalis sinistra; longitudinal fissure)
is a deep groove, which extends from the notch on the anterior margin of the liver
to the upper border of the posterior surface of the organ; it separates the right and
left lobes. The porta joins it, at right angles, and divides it into two parts. The
anterior part, or fossa for the umbilical vein, lodges the umbilical vein in the fetus,
and its remains (the ligamentum teres) in the adult; it lies between the quadrate
lobe and the left lobe of the liver, and is often partially bridged over by a pro-
longation of the hepatic substance, the pons hepatis. The posterior part, or fossa
for the ductus venosus, lies between the left lobe and the caudate lobe; it lodges in
the fetus, the ductus venosus, and in the adult a slender fibrous cord, the ligamentum
venosum, the obliterated remains of that vessel.
The porta or transverse fissure {porta hepatis) is a short but deep fissure, about
5 cm. long, extending transversely across the under surface of the left portion of the
right lobe, nearer its posterior surface than its anterior border. It joins nearly
at right angles with the left sagittal fossa, and separates the quadrate lobe in
front from the caudate lobe and process behind. It transmits the portal vein,
the hepatic artery and nerves, and the hepatic duct and lymphatics. The hepatic
duct lies in ffont and to the right, the hepatic artery to the left, and the portal
vein behind and between the duct and arterv.
The fossa for the gall-bladder (fossa vesicce fellecp) is a shallow, oblong fossa,
placed on the under surface of the right lobe, parallel with the left sagittal fossa.
It extends from the anterior free margin of the liver, which is notched by it, to the
right extremity of the porta.
The fossa for the inferior vena cava (fossa venoB cavce) is a short deep depression,
occasionally a complete canal in consequence of the substance of the liver surround-
ing the vena cava. It extends obliquely upward on the posterior surface between
the caudate lobe and the bare area of the liver, and is separated from the porta
by the caudate process. On slitting open the inferior vena cava the orifices of
the hepatic veins will be seen opening into this vessel at its upper part, after
perforating the floor of this fossa.
Lobes. — The right lobe (lobus hepatis dexter) is much larger than the left; the
proportion between them being as six to one. It occupies the right hypo-
1192 SPLANCHNOLOGY
chondrium, and is separated from the left lobe on its upper surface by the
falciform ligament; on its under and posterior surfaces by the left sagittal
fossa; and in front by the umbilical notch. It is of a somewhat quadrilateral form,
its under and posterior surfaces being marked by three fossae: the porta and the
fossae for the gall-bladder and inferior vena cava, which separate its left part
into two smaller lobes; the quadrate and caudate lobes. The impressions on the
right lobe have already been described.
The quadrate lobe (lobiis quadratus) is situated on the under surface of the right
lobe, bounded in front by the anterior margin of the liver; behind by the porta;
on the right, by the fossa for the gall-bladder; and on the left, by the fossa for the
umbilical vein. It is oblong in shape, its antero-posterior diameter being greater
than its transverse.
The caudate lobe {lobus caiidatus; Spigelian lobe) is situated upon the posterior
surface of the right lobe of the liver, opposite the tenth and eleventh thoracic
vertebrae. It is bounded, below, by the porta; on the right, by the fossa for the
inferior vena cava; and, on the left, by the fossa for the ductus venosus. It looks
backward, being nearly vertical in position; it is longer from above downward
than from side to side, and is somewhat concave in the transverse direction. The
caudate process is a small elevation of the hepatic substance extending obliquely
lateralward, from the lower extremity of the caudate lobe to the under surface of
the right lobe. It is situated behind the porta, and separates the fossa for the gall-
bladder from the commencement of the fossa for the inferior vena ca\a.
The left lobe (lobiis hepatis sinister) is smaller and more flattened than the right.
It is situated in the epigastric and left hypochondriac regions. Its upper surface
is slightly convex and is moulded on to the diaphragm; its under surface presents
the gastric impression and omental tuberosity, already referred to page 11 89.
Ligaments. — The liver is connected to the under surface of the diaphragm
and to the anterior wall of the abdomen by five ligaments; four of these — the
falciform, the coronary, and the two lateral — are peritoneal folds; the fifth, the
round ligament, is a fibrous cord, the obliterated umbilical vein. The liver is also
attached to the lesser curvature of the stomach by the hepatogastric and to the
duodenum by the hepatoduodenal ligament (see page 1157).
The falciform ligament (ligamenhnn falciforme hepatis) is a broad and thin antero-
posterior peritoneal fold, falciform in shape, its base being directed downward
and backward, its apex upward and backward. It is situated in an antero-posterior
plane, but Jies obliquely so that one surface faces forward and is in contact with
the peritoneum behind the right Rectus and the diaphragm, while the other is
directed backward and is in contact with the left lobe of the liver. It is attached
by its left margin to the under surface of the diaphragm, and the posterior surface
of the sheath of the right Rectus as low down as the umbilicus; by its right margin
it extends from the notch on the anterior margin of the liver, as far back as the
posterior surface. It is composed of two layers of peritoneum closely united
together. Its base or free edge contains between its layers the round ligament
and the parumbilical veins.
The coronary ligament (Jigamentum coronamim hepatis) consists of an upper
and a lower layer. The upper layer is formed by the reflection of the peritoneum
from the upper margin of the bare area of the liver to the under surface of the dia-
phragm, and is continuous with the right layer of the falciform ligament. The
loiver layer is reflected from the lower margin of the bare area on to the right kidney
and suprarenal gland, and is termed the hepatorenal ligament.
The triangular ligaments (lateral ligaments) are two in number, right and left.
The right triangular ligament {ligamentinii triangidare dextrum) is situated at the
right extremity of the bare area, and is a small fold which passes to the diaphragm,
being formed by the apposition of the upper and lower layers of the coronary
THE LIVER
1193
ligament. The left triangular ligament {ligamentum triangulare sinistrum) is a fold
of some considerable size, which connects the posterior part of the upper surface
of the left lobe to the diaphragm; its anterior layer is continuous with the left
layer of the falciform ligament.
The round ligament (ligamentum teres hepatis) is a fibrous cord resulting from the
obliteration of the umbilical vein. It ascends from the umbilicus, in the free margin
of the falciform ligament, to the umbilical notch of the liver, from which it may be
traced in its proper fossa on the inferior surface of the liver to the porta, where
it becomes continuous with the ligamentuvi venosnm.
Fixation of the Liver. — Several factors contribute to maintain the liver in
place. The attachments of the liver to the diai)hragm by the coronary and tri-
angular ligamt-nts and the intervening connective tissue of the uncovered area,
together with the intimate connection of the inferior ^■ena ca\a by the connective
tissue and hepatic veins would hold up the posterior part of the liver. Some sup-
port is derived from the pressure of the abdominal viscera which completely fill
the abdomen whose muscular walls are always in a state of tonic contraction. The
superior surface of the hver is perfectly fitted to the under surface of the diaphragm
so that atmospheric pressure alone would be enough to hold it against the dia-
phragm. The latter in turn is held up by the negative pressure in the thorax. The
lax falciform ligament certainly gives no support though it probably limits lateral
displacement.
Pericardial cavity
Anterior ivdll of
pericardium
Lower wall of
pericardium
Vitelline duct
Truncus arteriosus
Dorsal mesocardium
Atrium
Cuvierian duct
Umbilical vein
Vitelline vein
Communication
between pericardial
and peritoneal cavities
Peritoneal cavity
Fig. 1088. — Liver with the septum transversum. Human embryo 3 mm. long. (After model and figure by His.)
Development. — The liver arises in the form of a diverticulum or hollow outgrowth
from the ventral surface of that portion of the gut which afterward becomes
the descending part of the duodenum (Fig. 1088). This diverticulum is lined by
entoderm, and grows upward and forward into the septum transversum, a mass
of mesoderm between the vitelline duct and the pericardial cavity, and there gives
off two solid buds of cells which represent the right and the left lobes of the liver.
The solid buds of cells grow into columns or cylinders, termed the hepatic cylinders,
which branch and anastomose to form a close meshwork. This network invades
the vitelline and umbilical veins, and breaks up these vessels into a series of capil-
lary-like vessels termed sinusoids (]Minot), which ramify in the meshes of the cellular
1194
SPLANCHNOLOGY
network and ultimately form the venous capillaries of the liver. By the continued
growth and ramification of the hepatic cylinders the mass of the liver is gradually
formed. The original diverticulum from the duodenum forms the common bile-
duct, and from this the cystic duct and gall-bladder arise as a solid outgrowth which
later acquires a lumen. The opening of the common duct is at first in the ventral
wall of the duodenum; later, owing to the rotation of the gut, the opening is carried
to the left and then dorsalward to the position it occupies in the adult.
As the liver undergoes enlargement, both it and the ventral mesogastrium of
the fore-gut are gradually differentiated from the septum transversum; and from
the under surface of the latter the liver projects downward into the abdominal
cavity. By the growth of the liver the ventral mesogastrium is divided into two
parts, of which the anterior forms the falciform and coronary ligaments, and the
posterior the lesser omentum. About the third month the liver almost fills the
abdominal cavity, and its left lobe is nearly as large as its right. From this period
the relative development of the liver is less acti^•e, more especially that of the left
lobe, which actually undergoes some degeneration and becomes smaller than the
right; but up to the end of fetal life the liver remains relatively larger than in
the adult.
Orifices of intralobular veins
Fig. 1089. — Longitudinal section of a hepatic vein.
(After Kiernan.)
Portal
vein
'''^'^dnct'':^';
- ion of canal
from which
vein has been
removed.
FiQ. 1090. — Longitudinal section of a small portal vein
and canal. (After Kiernan.)
Vessels and Nerves. — The vessels connected with the liver are: the hepatic artery, the portal
vein, and the hepatic veins.
The hepatic artery and portal vein, accompanied by numerous nerves, ascend to the porta,
between the layers of the lesser omentum. The bile duct and the lymphatic vessels descend
from the porta between the layers of the same omentum. The relative positions of the three
structures are as follows: the bile duct lies to the right, the hepatic artery to the left, and the
portal vein behind and between the other two. They are enveloped in a loose areolar tissue, the
fibrous capsule of Glisson, which accompanies the vessels in their course through the portal
canals in the interior of the organ (Fig. 1090).
The hepatic veins (Fig. 10S9) convey the blood from the liver, and are described on page 680.
They have very little cellular investment, and what there is binds their parietes closely to the
walls of the canals through which they run; so that, on section of the organ, they remain widely
open and are solitary, and may be easily distinguished from the branches of the portal vein,
which are more or less collapsed, and always accompanied by an artery and duct.
The lymphatic vessels of the liver are described on page 711.
The nerves of the liver, derived from the left vagus and sympathetic, enter at the porta and
accompany the vessels and ducts to the interlobular spaces. Here, according to Korolkow, the
THE LIVER
1195
medullated fibers are distributed almost exclusively to the coats of the bloodvessels; while the
non-medullated enter the lobules and ramify between the cells and even within them.^
Intralobular vein
Intralobular vein ■ —
Fig. 1091. — Section of injected liver (dog).
Sinusoid
Structure of the Liver.— The substance of the liver is composed of lobules, held together by
an extremely fine areolar tissue, in which ramify the portal vein, hepatic ducts, hepatic artery,
hepatic veins, lymphatics, and nerves; the whole being invested by a serous and a fibrous coat.
The serous coat {tunica serosa) is derived from the peritoneum, and invests the greater part
of the surface of the organ. It is intimately adherent to the fibrous coat.
The fibrous coat (capsula fibrosa
[Glisso/d]; areolar coat) Hes beneath
the serous investment, and covers
the entire surface of the organ. It
is difficult of demonstration, except-
ing where the serous coat is defi-
cient. At the porta it is continuous
with the fibrous capsule of Ghsson,
and on the surface of the organ with
the areolar tissue separating " the
lobules.
The lobules {lobuli hepatis) form
the chief mass of the hepatic sub-
stance; they may be seen either on
the surface of the organ, or by mak-
ing a section through the gland, as
small granular bodies, about the size
of a millet-seed, measuring from 1 to
2.5 mm. in diameter. In the human
subject their outlines are very irreg-
ular; but in some of the lower ani-
mals (for example, the pig) they are
well-defined, and, when divided
transversely, have polj'gonal out-
lines. The bases of the lobules are clustered around the smallest radicles (sublobular) of the
hepatic veins, to which each is connected (Fig. 10S9) by means of a small branch which issues
from the center of the lobule {intralobular). The remaining part of the surface of each lobule
is imperfectly isolated from the surrounding lobules by a thin stratum of areolar tissue, in
which is contained a plexus of vessels, the interlobular plexus, and ducts. In some animals, as
the pig, the lobules are completely isolated from one another by the interlobular areolar tissue
(Fig. 1092).
If one of the sublobular veins be laid open, the bases of the lobules may be seen through the
thin wall of the vein on which they rest, arranged in a form resembling a tesselated pavement,
Column of liver-
cells
Interlobxdar vein
Intralobular vein
Sublobular vein
Fig. 1092. — A single lobule of the liver of a pig. X 60.
1 Berkeley, Anat., Aug., 8, 1893; JVIacCallum, A. B., Quart. Jour. Micr. Sci., 1887, 27; Allegra, Anat., Aug. 25, 1904.
1196
SPLANCHNOLOGY
the center of each polygonal space presenting a minute aperture, the mouth of an intralobular
vein (Fig. 1089).
Microscopic Appearance (Fig. 1092).- — ^Each lobule consists of a mass of cells, hepatic cells,
arranged in irregular radiating columns between which are the blood channels (sinusoids) . These
convey the blood from the circumference to the center of the lobule, and end in the intralobular
vein, which runs through its center, to open at its base into one of the sublobular veins. Between
the cells are also the minute bile capillaries. Therefore, in the lobule there are all the essentials
of a secreting gland; that is to say: (1) cells, bj' which the secretion is formed; (2) bloodvessels,
in close relation with the cells, containing the blood from which the secretion is derived; (3)
ducts, by which the secretion, when formed, is carried away.
1. The hepatic cells are polyhedral in form. They vary in size from 12 to 25/^ in diameter.
They contain one or sometimes two distinct nuclei. The nucleus exhibits an intranuclear net-
work and one or two refractile nucleoli. The cells usually contain granules; some of which are
protoplasmic, while others consist of glycogen, fat, or an iron compound. In the lower vertebrates,
e. g., frog, the cells are arranged in tubes with the bile duct forming the lumen and bloodvessels
externally. According to Delepine, evidences of this arrangement can be found in the human
liver.
/~ 2. The Bloodvessels. — The blood in the capillar}^ plexus around the liver cells is brought to
(the liver principally by the portal vein, but also to a certain extent by the hepatic artery.
The hepatic artery, entering the liver at the porta with the portal vein and hepatic duct,
ramifies with these vessels through the portal canals. It gives off vaginal branches, which ramify
in the fibrous capsule of Glisson, and appear to be destined chiefly for the nutrition of the coats
of the vessels and ducts. It also gives off capsular branches, which reach the surface of the
organ, ending in its fibrous coat in stellate plexuses. Finally, it gives off interlobular branches,
which form a plexus outside each lobule, to supply the walls of the interlobular veins and the
accompanying bile ducts. From this plexus lobular branches enter the lobule and end in the
net-work of sinusoids between the cells.
The portal vein also enters at the porta, and runs through the portal canals (Fig, 1093),
enclosed in Glisson's capsule, dividing in its course into branches, which finally break up into a
plexus, the interlobular plexus, in the interlobular spaces. These branches receive the vaginal
and capsular veins, correspond-
Bile-duct Ii^po-ii<^ artery ji^g ^q ^j^g \-aginal and capsular
branches of the hepatic artery.
Thus it will be seen that all the
blood carried to the liver by the
portal vein and hepatic artery
finds its way into the interlob-
ular plexus. From this plexus
the blood is carried into the lobule
by fine branches which converge
from the circumference to the
, Lymphatic
vessel
Portal
vein
Fia. 1093. — Section across portal canal of pig. X 250.
Fig. 1094. — Bile capillaries of rabbit,
shown by Golgi's method. X 450.
center of the lobule, and are connected by transverse branches (Fig. 1091). The walls of these
small vessels are incomplete so that the blood is brought into direct relationship with the liver
cells. The lining endothelium consists of irregularly branched, disconnected cells (stellate cells of
Kupffer) . Moreover, according to Herring and Simpson, minute channels penetrate the hver cells
themselves, conveying the constituents of the blood into their substance. It will be seen that the
blood capillaries of the hver lobule differ structurally from capillaries elsewhere. Developmentally
they are formed by the growth of the columns of hver cells into large blood spaces or sinuses,
and hence they have received the name of "sinusoids." Arrived at the center of the lobule,
THE LIVER
\Wt
Gall-
bladder
the sinusoids empty themselves into one vein, of considerable size, which runs down the
center of the lobule from apex to base, and is called the intralobular vein. At the base of
the lobule this vein opens directly into the sublobular vein, with which the lobule is con-
nected. The sublobular veins unite to form larger and larger trunks, and end at last in the
hepatic veins, these converge to form three large trunks which open into the inferior vena cava
while that vessel is situated in its fossa on the posterior surface of the liver.
3. The bile ducts commence by little passages in the liver cells which communicate with
canaliculi termed intercellular biliary passages (bile capillaries). These passages are merely
little channels or spaces left between the contiguous surfaces of two cells, or in the angle where
three or more liver cells meet (Fig. 1094), and they are always separated from the blood capil-
laries by at least half the width of a liver cell. The channels thus formed radiate to the circum-
ference of the lobule, and open into the interlobular bile ducts which run in GUsson's capsule,
accompanying the portal vein and hepatic artery (Fig. 1093). These join with other ducts to
form two main trunks, which leave the liver at the transverse fissure, and by their union form
the hepatic duct.
Structure of the Ducts. — The walls of the biliary ducts consist of a connective-tissue coat, in
which are muscle cells, arranged both circularly and longitudinally, and an epithelial layer,
consisting of short columnar cells resting on a distinct basement membrane.
Excretory Apparatus of the Liver. — The excretory apparatus of the liver con-
sists of (1) the hepatic duct, formed by the junction of the two main ducts, which
pass out of the Kver at the porta; (2) the gall-
bladder, which serves as a reservoir for the bile;
(3) the cystic duct, or the duct of the gall-blad-
der; and (4) the common bile duct, formed by
the junction of the hepatic and cystic ducts
The Hepatic Duct (ductus hepaticus). — Two
main trunks of nearly equal size issue from
the liver at the porta, one from the right, the
other from the left lobe; these unite to form
the hepatic duct, which passes downward and
to the right for about 4 cm., between the layers
of the lesser omentum, where it is joined at
an acute angle by the cystic duct, and so forms
the common bile duct. The hepatic duct is
accompanied by the hepatic artery and portal
vein.
The Gall-bladder {vesica fellea) (Fig. 1095).
— The gall-bladder is a conical or pear-shaped
musculomembranous sac, lodged in a fossa on
the under surface of the right lobe of the liver,
and extending from near the right extremity of
the porta to the anterior border of the organ. It
is from 7 to 10 cm. in length, 2.5 cm. in breadth at
its widest part, and holds from 30 to 35 c.c. It is
divided into a fundus, body, and neck. The
fimdus, or broad extremity, is directed down-
ward, forward, and to the right, and projects
beyond the anterior border of the liver; the
body and neck are directed upward and back-
ward to the left. The upper surface of the gall-
bladder is attached to the liver by connective
tissue and vessels. The under surface is covered by peritoneum, which is reflected
on to it from the surface of the liver. Occasionally the whole of the organ is
invested by the serous membrane, and is then connected to the liver by a kind
of mesentery.
Relations. — The body is in relation, by its upper surface, with the liver; by its under surface,
with the commencement of the transverse colon; and farther back usually with the upper end
Hepatic
duct
Common bile-
duct
Fig. 1095. — The gall-bladder and bile ducts
laid open. (Spalteholz.)
1198
SPLANCHNOLOGY
of the descending portion of the duodenum, but sometimes with the superior portion of the
duodenum or pyloric end of the stomach. The fundus is completely invested by peritoneum;
it is in relation, in front, with the abdominal parietes, immediately below the ninth costal car-
. tilage; behind with the transverse colon. The neck is narrow, and curves upon itself hke the
letter S; at its point of connection with the cystic duct it presents a weU-marked constriction.
Columnar epithelium
> Fihro-muscvlar
coat
Liver-cells
Fig. 1096. — Transverse section of gall-bladder.
Structure ( Fig. 1096). — The gaU-bladder consists of three coats: serous, fibromuscular, and
mucous.
The external or serous coat {tunica serosa vesicm fellece) is derived from the peritoneum; it
completely invests the fundus, but covers the body and neck only on their under surfaces.
The fibromuscular coat {tunica inuscularis vesicce felleiv), a thin but strong layer forming the
frame-work of the sac, consists of dense fibrous tissue, which interlaces in all directions, and is
mixed with plain muscular fibers, disposed chiefly in a longitudinal direction, a few running
transverselj'.
The internal or mucous coat {tunica mucosa vesicae fellece) is loosely connected with the fibrous
layer. It is generally of a j-ellowish-brown color, and is elevated into minute rugis. Opposite
the neck of the gall-bladder the mucous membrane projects inward in the form of obhque ridges
or folds, forming a sort of spiral valve.
The mucous membrane is continuous through the hepatic duct with the mucous membrane
fining the ducts of the fiver, and through the common bile duct with the mucous membrane of
the duodenum. It is covered with columnar epithefium, and secretes mucin; in some animals
it secretes a nucleoprotein instead of mucin.
The Cystic Duct {ductus cysticus). — The cystic duct about 4 cm. long, runs back-
ward, downward, and to the left from the neck of the gall-bladder, and joins the
hepatic duct to form the common bile duct. The mucous membrane lining its
interior is thrown into a series of crescentic folds, from five to twelve in number,
similar to those found in the neck of the gall-bladder. They project into the duct
in regular succession, and are directed obliquely around the tube, presenting
much the appearance of a continuous spiral valve. When the duct is distended,
the spaces between the folds are dilated, so as to give to its exterior a twisted
appearance.
The Common Bile Duct {ductus choledochus). — The common bile duct is formed
by the junction of the cystic and hepatic ducts; it is about 7.5 cm. long, and of the
diameter of a goose-quill.
It descends along the right border of the lesser omentum behind the superior
portion of the duodenum, in front of the portal vein, and to the right of the hepatic
artery; it then runs in a groove near the right border of the posterior surface of the
head of the pancreas; here it is situated in front of the inferior vena cava, and is
occasionally completely imbedded in the pancreatic substance. At its termination
it lies for a short distance along the right side of the terminal part of the pancreatic
duct and passes with it obliquely between the mucous and muscular coats. The
THE PANCREAS
1199
two ducts unite and open by a common orifice upon the summit of the duodenal
papilla, situated at the medial side of the descending portion of the duodenum, a
little below its middle and about 7 to 10 cm. from the pylorus (Fig. 1100). The
short tube formed by the union of the two ducts is dilated into an ampulla, the
ampulla of Vater.
Structure. — The coats of the large biliary ducts are an external or fibrous, and an internal or
mucous. The fibrous coat is composed of strong fibroareolar tissue, with a certain amount of
muscular tissue, arranged, for the most part, in a circular manner around the duct. The mucous
coat is continuous with the lining membrane of the hepatic ducts and gall-bladder, and also with
that of the duodenum; and, like the mucous membrane of these structures, its epithelium is of
the colmnnar variety. It is provided with numerous mucous glands, which are lobulated apd
open by minute orifices scattered irregularly in the larger ducts.
The Pancreas (Figs. 1097, 1098).
The pancreas is a compound racemose gland, analogous in its structures to the
salivary glands, though softer and less compactly arranged than those organs.
Its secretion, the pancreatic juice, carried by the pancreatic duct to the duodenum,
is an important digestive fluid. In addition the pancreas has an important internal
secretion, probably elaborated by the cells of Langerhans, which is taken up by
the blood stream and is concerned with sugar metabolism. It is long and irregularly
Rectus abdominis
Eighth costal cartilage
Seventh costal cartilage
Seventh rib
Eighth
rib
Ninth
rib
Tenth rib
Diaphragm
Abdominal aorta
(Twelfth rib
Eleventh rib
Fig. 1097. — Transverse section through the middle of the first lumbar vertebra, showing the relations of the pancreas.
(Braune.)
prismatic in shape; its right extremity, being broad, is called the head, and is con-
nected to the main portion of the organ, or body, by a slight constriction, the neck;
while its left extremity gradually tapers to form the tail. It is situated transversely
across the posterior wall of the abdomen, at the back of the epigastric and left
hypochondriac regions. Its length varies from 12.5 to 15 cm., and its weight from
60 to 100 gm.
1200
SPLANCHNOLOGY
Relations. — The Head {capvt imncreatis) is flattened from before backward, and
is lodged within the curve of the duodenum. Its upper border is overlapped by the
Fig. 109S. — The duodenum and pancreas.
-superior part of the duodenum and its lower overlaps the horizontal part; its right
.and left borders overlap in front, and insinuate themselves behind, the descending
Celiac artery
Superior mesenteric artery
Area for Diaphragm
Fig. 1099. — The pancreas and duodenum from behind. (From model by His.)
:and ascending parts of the duodenum respectively. The angle of junction of the
lower and left lateral borders forms a prolongation, termed the uncinate process. In
THE PANCREAS 1201
the groove between the duodenum and the right Lateral and lower borders in front
are the anastomosing superior and inferior pancreaticoduodenal arteries; the com-
mon bile duct descends behind, close to the right border, to its termination in the
descending part of the duodenum.
Anterior Surface. — The greater part of the right half of this surface is in contact
with the transverse colon, only areolar tissue intervening. From its upper part
the neck springs, its right limit being marked by a groove for the gastroduodenal
artery. The lower part of the right half, below the transverse colon, is covered
by peritoneum continuous with the inferior layer of the transverse mesocolon,
and is in contact with the coils of the small intestine. The superior mesenteric
artery passes down in front of the left half across the uncinate process; the superior
mesenteric vein runs upward on the right side of the artery and, behind the neck,
joins with the lienal vein to form the portal vein.
Posterior Surface. — The posterior surface is in relation with the inferior vena
cava, the common bile duct, the renal veins, the right crus of the diaphragm, and
the aorta.
The Neck springs from the right upper portion of the front of the head. It is
about 2.5 cm. long, and is directed at first upward and forward, and then upward
and to the left to join the body; it is somewhat flattened from above downward
and backward. Its antero-superior surface supports the pylorus; its postero-
inferior surface is in relation with the commencement of the portal vein; on the
right it is grooved by the gastroduodenal artery.
The Body (corpus pancreatis) is somewhat prismatic in shape, and has three
surfaces: anterior, posterior, and inferior.
The anterior surface (fades anterior) is somewhat concave; and is directed for-
ward and upward: it is covered by the postero-inferior surface of the stomach
which rests upon it, the two organs being separated by the omental bursa. Where
it joins the neck there is a well-marked prominence, the tuber omentale, which
abuts against the posterior surface of the lesser omentum.
The posterior surface (fades posterior) is devoid of peritoneum, and is in contact
with the aorta, the lienal vein, the left kidney and its vessels, the left suprarenal
gland, the origin of the superior mesenteric artery, and the crura of the diaphragm.
The inferior surface (fades inferior) is narrow on the right but broader on the left,
and is covered by peritoneum; it lies upon the duodenojejunal flexure and on some
coils of the jejunum; its left extremity rests on the left colic flexure.
The superior border (margo superior) is blunt and flat to the right; narrow and
sharp to the left, near the tail. It commences on the right in the omental tuber-
osity, and is in relation with the celiac artery, from which the hepatic artery
courses to the right just above the gland, while the lienal artery runs toward the
left in a groove along this border.
The anterior border (margo anterior) separates the anterior from the inferior
surface, and along this border the two layers of the transverse mesocolon diverge
from one another; one passing upward over the anterior surface, the other
backward over the inferior surface.
The inferior border (margo inferior) separates the posterior from the inferior
surface; the superior mesenteric vessels emerge under its right extremity.
The Tail (cauda pancreatis) is narrow; it extends to the left as far as the lower
part of the gastric surface of the spleen, lying in the phrenicolienal ligament,
and it is in contact with the left colic flexure.
Birmingham described the body of the pancreas as projecting forward as a promi-
nent ridge into the abdominal cavity and forming part of a shelf on which the
stomach lies. "The portion of the pancreas to the left of the middle line has a
very considerable antero-posterior thickness; as a result the anterior surface is of
considerable extent; it looks strongly upward, and forms a large and ijmportant
76
1202
SPLANCHNOLOGY
part of the shelf. As the pancreas extends to the left toward the spleen it crosses
the upper part of the kidney, and is so moulded on to it that the top of the kidney
forms an extension inward and backward of the upper surface of the pancreas
and extends the bed in this direction. On the other hand, the extremity of the
pancreas comes in contact with the spleen in such a way that the plane of its
upper surface runs with little interruption upward and backward into the concave
gastric surface of the spleen, which completes the bed behind and to the left, and,
running upward, forms a partial cap for the wide end of the stomach.^
Hepatic artery
Portal vein
Common bile-duct
Orifice of common
bile-duct and pan. VWuM^W Accessory pancreatic duct
creattc duct .MmiiMHSmmr^^^'^ / „ . ,
Pancreatic duct
Tii;. 1100. — The pancreatic duct.
The Pancreatic Duct (ductus pancreaticus [Wirsungi]; duct of Wirsung) extends
transversely from left to right through the substance of the pancreas (Fig. 1 100). It
commences by the junction of the small ducts of the lobules situated in the tail of the
pancreas, and, running from left to right through the body, it receives the ducts of the
various lobules composing the gland. Considerably augmented in size, it reaches the
neck, and turning downward, backward, and to the right, it comes into relation with
the common bile duct, which lies to its right side; leaving the head of the gland,
it passes very obliquely through the mucous and muscular coats of the duodenum,
and ends by an orifice common to it and the common bile duct upon the summit
of the duodenal papilla, situated at the medial side of the descending portion
of the duodenum, 7.5 to 10 cm. below the pylorus. The pancreatic duct, near the
duodenum, is about the size of an ordinary quill. Sometimes the pancreatic duct
and the common bile duct open separately into the duodenum. Frequently there
is an additional duct, which is given off from the pancreatic duct in the neck of
the pancreas and opens into the duodenum about 2.5 cm. above the duodenal
papilla. It receives the ducts from the lower part of the head, and is known as
the accessory pancreatic duct {duct of Santorini).
Development (Figs. 1101, 1102). — The pancreas is developed in two parts, a
dorsal and a ventral. The former arises as a diverticulum from the dorsal aspect
' Journal of Anatomy and Physiology, pt. 1. xxxi. 102.
THE PANCREAS
1203
of the duodenum a short distance above the hepatic diverticulum, and, growing
upward and backward into the dorsal mesogastrium, forms a part of the head and
uncinate process and the whole of the body and tail of the pancreas. The ventral
part appears in the form of a diverticulum from the primitive bile-duct and forms
the remainder of the head and uncinate process of the pancreas. The duct of
the dorsal part (accessory pancreatic duct) therefore opens independently into the
duodenum, while that of the ventral part (pancreatic duct) opens with the common
bile-duct. About the sixth week the two parts of the pancreas meet and fuse
Accessory paucrealic dud
Dorsal pancreas
Accessory pancreatic duct
" / Dorsal pancreas
Ventral pancreas
Pancreatic duct
Bile duct
Fig. 1101.
-Pancreas of a human enibryo of five
weeks. (KoUmann.)
Bile dtiCL
Fig. 1102.-
Ventral pancreas
Pancreatic duct
-Pancreas of a human embryo at end of
sixth week. (KoUmann.)
and a communication is established between their ducts. After this has occurred
the terminal part of the accessory duct, i. c, the part between the duodenum and
the point of meeting of the two ducts, undergoes little or no enlargement, while
the pancreatic duct increases in size and forms the main duct of the gland. The
opening of the accessory duct into the duodenum is sometimes obliterated, and
even when it remains patent it is probable that the whole of the pancreatic secretion
is conveyed through the pancreatic duct.
Lesser
Liver Stomach omentum Liver
Left suprarenal Right suprarenal
gland gland
Fig. 1103. — Schematic and enlarged cross-section through the body of a human enforyo in tlie region of the
mesogastrium. Beginning of third month. (Toldt.)
At first the pancreas is directed upward and backward between the two layers
of the dorsal mesogastrium, which give to it a complete peritoneal investment,
and its surfaces look to the right and left. With the change in the position of the
stomach the dorsal mesogastrium is drawn downward and to the left, and the right
side of the pancreas is directed backward and the left forward (Fig. 1103). The
right surface becomes applied to the posterior abdominal wall, and the peritoneum
which covered it undergoes absorption (Fig. 1104) ; and thus, in the adult, the gland
appears to lie behind the peritoneal cavity.
Structure (Fig. 1105). — In structure, the pancreas resembles the salivary glands. It differs
from them, however, in certain particulars, and is looser and softer in its texture. It is not
enclosed in a distinct capsule, but is surrounded by areolar tissue, which dips into its interior,
1204
SPLANCHNOLOGY
and connects together the various lobules of which it is composed. Each lobule, like the lobules
of the sahvary glands, consists of one of the ultimate ramifications of tHe main duct, ending in a
number of cecal pouches or alveoli, which are tubular and somewhat convoluted. The minute
ducts connected with the alveoli are narrow and hned with flattened cells. The alveoli are
Lesser
Stotnach omentum
Liver
Liver
Bight suprarenal gland
Left swprarenal gland
Alveolus
Cell-islet
Fig. 1104. — Section through same region as in Fig. 1 103, at end of third month. (Toldt.)
almost completely filled with secreting cells, so that scarcely any lumen is visible. In some
animals spindle-shaped cells occupy the center of the alveolus and are knowTi as the centro-
acinar cells of Langerhans. These are prolongations of the terminal ducts. The true secreting
cells which line the wall of the alveolus are very characteristic. They are columnar in shape
and present two zones : an outer one, clear
and finely striated next the basement mem-
brane, and an inner granular one next the
lumen. In hardened specimens the outer
zone stains deeplj" with various d3-es, where-
as the inner zone stains sUghth'. Diu-ing
activity the granular zone gradually dimin-
ishes in size, and when exhausted is only
seen as a small area next to the lumen.
During the resting stages it gradually in-
creases until it forms nearly three-fourths
of the cell. In some of the secreting cells
of the pancreas is a spherical mass, stain-
ing more easily than the rest of the cell;
this is termed the paranucleus, and is be-
lieved to be an extension from the nucleus.
The connective tissue between the alveoli
presents in certain parts collections of cells,
which are termed interalveolar cell islets
{islands of Langerhayis) . The cells of these
Stain light Ij^ with hematoxj'lin or carmine,
and are more or less polyhedral in shape,
forming a net-work in which ramify many
capillaries. There are two main types of cell in the islets, distinguished as A-cells and B-cells
according to the special staining reactions of the granules they contain. The cell islets have
been supposed to produce the internal secretion of the pancreas which is necessarj- for carbo-
hydrate metaboUsm, but numerous researches have so far failed to elucidate their real function.
The walls of the pancreatic duct are thin, consisting of two coats, an external fibrous and an
internal mucous; the latter is smooth, and furnished near its termination with a few scattered
foUicles.
Vessels and Nerves. — The arteries of the pancreas are derived from the lienal, and the
pancreaticoduodenal branches of the hepatic and superior mesenteric. Its veins open into the
lienal and superior mesenteric veins. Its lymphatics are described on page 711. Its nerves are
filaments from the lienal plexus.
THE UROGENITAL APPARATUS (APPARATUS UROGENITALIS ;
UROGENITAL ORGANS).
The urogenital apparatus consists of (a) the urinary organs for the secretion
and discharge of the urine, and (6) the genital organs, which are concerned with
the process of reproduction.
Fig. 1105. — Section of pancreas of dog. X 250.
DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS 1205
DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS.
The urinary and generative organs are developed from the intermediate cell-
mass which is situated between the primitive segments and the lateral plates of
mesoderm. The permanent organs of the adult are preceded by a set of structures
which are purely embryonic, and which with the exception of the ducts disappear
almost entirely before the end of fetal life. These embryonic structures are on
either side; the pronephros, the mesonephros, the metanephros, and the Wolffian and
Miillerian ducts. The pronephros disappears very early; the structural elements
of the mesonephros mostly degenerate, but in their place is developed the genital
gland in association with which the Wolffian duct remains as the duct of the male
genital gland, the ^Miillerian as that of the female; some of the tubules of the
metanephros form part of the permanent kidney.
The Pronephros and Wolffian Duct. — In the outer part of the intermediate
cell-mass, immediately imder the ectoderm, in the region from the fifth cervical to
the third thoracic segments, a series of short evaginations from each segment grows
dorsalward and extends caudalward, fusing successively from before backward to
form the pronephric duct. This continues to grow caudalward until it opens into
the ventral part of the cloaca; beyond the pronephros it is termed the Wolffian duct.
The original evaginations form a series of transverse tubules each of which com-
municates by means of a funnel-shaped ciliated opening with the celomic cavity,
and in the course of each duct a glomerulus also is developed. A secondary
glomerulus is formed ventral to each of these, and the complete group constitutes
the pronephros. The proneplu"os undergoes rapid atrophy and disappears.
cStroma
Genital] of ovary \\
ridge j Primitive
\ ova
Mesentery
Iffian duct
Miillerian duct
■~~5» Wolffian tuhvles
Body -wall
Fig. 1106. — Section of the urogenital fold of a chick embryo of the fourth day. (Waldeyer.)
The Mesonephros, Miillerian Duct, and Genital Gland.^3n the medial side of
the Wolffian duct, from tiie sixth cervical to the third lumbar segments, a series
of tubules, the Wolffian tubules (Fig. 1106), is developed; at a later stage in develop-
ment they increase in number by outgrowths from the original tubules. These
tubules first appear as solid masses of cells, which later become hollowed in the
center; one end grows toward and finally opens into the Wolffian duct, the other
dilates and is invaginated by a tuft of capillary bloodvessels to form a glomerulus.
The tubules collectively constitute the mesonephros or Wolffian body (Figs. 986,
120G
SPLANCHNOLOGY
1107). By the fifth or sixth week this body forms an elongated spindle-shaped
structure, termed the urogenital fold (Fig. 1106), which projects into the celomic
cavity at the side of the dorsal mesentery, reaching from the septum transversum
in front to the fifth lumbar segment behind; in this fold the reproductive glands are
developed. The Wolffian bodies persist and form the permanent kidneys in fishes
and amphibians, but in reptiles, birds, and mammals, they atrophy and for the
most part disappear coincidently with the development of the permanent kidneys.
The atrophy begins during the sixth or seventh week and rapidly proceeds, so that
by the beginning of the fifth month only the ducts and a few of the tubules remain.
In the male the Wolffian duct persists,
and forms the tube of the epididymis, the
ductus deferens and the ejaculatory duct,
while the seminal vesicle arises during the
third month as a lateral diverticulum from
its hinder end. A large part of the head
end of the mesonephros atrophies and dis-
appears; of the remainder the anterior
tubules form the efferent ducts of the
testis; while the posterior tubules are
represented by the ductuli aberrantes,
and by the paradidymis, which is some-
times found in front of the spermatic
cord above the head of the epididvmis
(Fig. 1110, C).
In the female the Wolffian bodies and ducts atrophy. The remains of the
Wolffian tubules are represented by the epobphoron or organ of Rosenmiiller, and
the paroophoron, two small collections of rudimentary blind tubules which are
situated in the mesosalpinx (Fig. 1108). The lower part of the Wolffian duct
disappears, while the upper part persists as the longitudinal duct of the epoophoron
or duct of Gartner! (Fig. 1110, Bf.
Fig. 1107. — Enlarged view from the front of the
left Wolffian body before the establishinent of the
distinction of se.\. (From Farre, after Kobelt.) a,
a, b, c, d. Tubular structure of the Wolffian body.
e. Wolffian duct. /. Its upper extremity, g. Its
termination in x, the urogenital sinus, h. The duct
of ISIuller. I. Its upper, funnel-shaped extremity.
k. Its lower end, terminating in the urogenital sinus.
I. The genital gland.
,x^a
Fig. IIOS. — Broad ligament of adiilt, showing epoophoron. (From Farre, after Kobelt.) a, a. Epoophoron formed
from the upper part of the Wolffian body. b. Remains of the uppermost tubes sometimes forming appendices, c. Middle
set of tubes. (I. Some lower atrophied tubes, e. Atrophied remains of the Wolffian duct. /. The terminal bulb or
hydatid, h. The uterine tube, originally the duct of Muller. i. Appendix attached to the extremity. /. The ovary.
The Miillerian Ducts. — Shortly after the formation of the Wolffian ducts a
second pair of ducts is developed; these are named the Miillerian ducts. Each
arises on the lateral aspect of the corresponding Wolffian duct as a tubular invag-
1 Bern,' Hart (op. cit.) has described the Wolffian ducts as ending at the site of the future hymen in bulbous enlarge-
ments, which he has named the Wolffian bulbs; and states that the hymen is formed by these bulbs, "aided by a special
involution from below of the cells lining the urogenital sinus. " He further believes that "the lower third of the vagina
is due to the coalescence of the upper portion of the urogenital sinus and the lower ends of the Wolffian ducts," and
that "the epithehal lining of the vagina is derived from the Wolffian bulbs. " He also regards the colliculus semmabs
of the male urethra as being formed from the lower part of the Wolffian ducts.
DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS 1207
emtne
Fig. 1 1 09. — Urogenital sinus of female human
embryo of eight and a half to nine weeks old.
(From model by Keibel)
ination of the cells lining the celom (Fig. 1106). The orifice of the invagination
remains patent, and undergoes enlargement and modification to form the abdomi-
nal ostium of the uterine tube. The ducts pass backward lateral to the Wolffian
ducts, but toward the posterior end of tlie embr>'o they cross to the medial side
of these ducts, and thus come to lie side by side between and behind the latter —
the four ducts forming what is termed the genital cord (Fig. 1109). The Miillerian
ducts end in an epithelial elevation, the Miillerian eminence, on the ventral part of
the cloaca between the orifices of the Wolffian
ducts; at a later date they open into the cloaca Mnllerian divcts
in this situation.
In the male the Miillerian ducts atrophy,
but traces of their anterior ends are repre-
sented by the appendices testis {hydatids of
Morgogni), whWe their terminal fused portions
form the utriculus in the floor of the prostatic
portion of the urethra (Fig. 1110, C).
In the female the Miillerian ducts persist Mullerian
and undergo further development. The por-
tions which lie in the genital core fuse to form
the uterus and vagina; the parts in front of
this cord remain separate, and each forms
the corresponding uterine tube — the abdomi-
nal ostium of which is developed from the
anterior extremity of the original tubular in-
vagination from the celom (Fig. 1110, B). The
fusion of the Miillerian ducts begins in the third month, and the septum formed
by their fused medial walls disappears from below upward, and thus the cavities
of the vagina and uterus are produced. About the fifth month an annular con-
striction marks the position of the neck of the uterus, and after the sixth month
the walls of the uterus begin to thicken. For a time the vagina is represented by a
solid rod of epithelial cells. A ring-like outgrowth of this epithelium occurs at
the lower end of the uterus and marks the future vaginal fornices; about the fifth
or sixth month the lumen of the vagina is produced by the breaking down of the
central cells of the epithelium. The hymen represents the remains of the Miillerian
eminence.
Genital Glands. — The first appearance of the genital gland is essentially the
same in the two sexes, and consists in a thickening of the epithelial layer which
lines the peritoneal cavity on the medial side of the urogenital fold (Fig. 1106).
The thick plate of epithelium extends deeply, pushing before it the mesoderm and
forming a distinct projection. This is termed the genital ridge (Fig. 1106), and from
it the testis in the male and the ovary in the female are developed. At first the
mesonephros and genital ridge are suspended by a common mesentery, but as the
embryo grows the genital ridge gradually becomes pinched off from the meso-
nephros, with which it is at first continuous, though it still remains connected to
the remnant of this body by a fold of peritoneum, the mesorchium or mesovarium
(Fig. 1111). About the seventh week the distinction of sex in the genital ridge
begins to be perceptible.
The Ovary. — The ovary, thus formed from the genital ridge, is at first a mass
of cells derived from the celomic epithelium; later the mass is differentiated
into a central part or medulla (Fig. 1112) covered by a surface layer, the germinal
epithelium. Between the cells of the germinal epithelium a number of larger
cells, the primitive ova, are found, and these are carried into the subjacent stroma
by bud-like ingrowths (genital cords) of the germinal epithelium (Fig. 1113).
The surface epithelium ultimately forms the permanent epithelial covering of this
1208
SPLANCHNOLOGY
Fig. 11] 0. — Diagrams to show the develop-
ment of male and female generative organs
from a common type. (Allen Thomson.)
A. — Diagram of the primitive urogenital
organs in the embryo previous to sexual dis-
tinction. 3. Ureter. 4. Urinary bladder. 5.
Urachus. cl. Cloaca, cp. Elevation which be-
comes clitoris or penis, i. Lower part of the
intestine. Is. Fold of integument from which
the labia majora or scrotum are formed,
m, m. Right and left jMiillerian ducts uniting
together and running with the Wolffian ducts
in gc, the genital cord. ot. The genital ridge
from which either the ovary or testis is
formed, ug. Sinus urogenitalis. TT'. Left
Wolffian body, w, w. Right and left Wolffian
ducts.
B
B. — Diagram of the female type of sexual
organs. C. Greater vestibular gland, and
immediately above it the urethra, cc. Corpus
cavernosum clitoridis. dG. Remains of the
left Wolffian duct, such as give rise to the
duct of Gartner, represented by dotted lines;
that of the right side is marked w. f. The
abdominal opening of the left uterine tube.
g. Round ligament, corresponding to guber-
naculum. A. Situation of the hymen, i. Lower
part of the intestine. I. Labium major. ?i.
Labium minus, o. The left ovary, po. Epo-
ophoron. sc. Corpus cavernosum urethrae. u.
Uterus. The uterine tube of the right side
is marked m. v. Vulva, va. ^'agina. IF.
Scattered remains of Wolffian tubes near it
(paroophoron of Waldeyer).
C. — Diagram of the male type of sexual
organs. C. Bulbo-urethral gland of one side.
cp. Corpora cavernosa penis cut short, e.
Caput epididymis, g. The gubernaculum.
i. Lower part of the intestine, m. Miillerian
duct, the upper part of which remains as
the hydatid of Alorgagni; the lower part,
represented by a dotted line descending to
the prostatic utricle, constitutes the occa-
sionally existing cornu and tube of the uterus
masculinus. pr. The prostate, s. Scroturn.
sp. Corpus cavernosum urethrae. t. Testis
in the place of its original formation, t',
together with the dotted lines above, indi-
cates the direction in which the testis and
epididymis descend from the abdomen into
the scrotum, aid. Ductus deferens. t)/i. Ductus
aberrans. vs. The vesicula seminalis. W.
Scattered remains of the Wolffian body, con-
stituting the organ of Giraldds, or the para-
didymis of Waldeyer.
DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS 1209
organ; it soon loses its connection with the central mass, and a tunica albuginea
develops between them. The ova are chiefly derived from the cells of the central
mass; these are separated from one
another by the growth of connective
tissue in an irregular manner; each ovum
assumes a covering of connective tissue
(follicle) cells, and in this way the rudi-
ments of the ovarian follicles are formed
(P'ig. 1113). According to Beard the
primitive ova are early set apart during
the segmentation of the ovum and migrate
into the germinal ridge.
WnlJTian htidi)
MilUermn duct
Wolffian dxict
Intestine
Bladder
(Imbilical artery
Waldeyer taught that the primitive germ
cells are derived from the "germinal epithe-
lium," covering the genital ridge. Beard/ on
the other hand, maintains that in the skate they
are not derived from this epithelium, but are
probably formed during the later stages of cell
cleavage, before there is any trace of an embryo;
and a similar view was advanced by Nussbaum
as to their origin in amphibia. Beard says: "At
the close of segmentation many of the future
germ cells he in the segmentation cavity just
beneath the site of the future embryo, and there
is no doubt they subsequently wander into it."
The germ cells, "after they enter the resting
phase, are sharply marked off from the cells of the embryo by entire absence of mitoses among
them." They can be further recognized by their irregular form and ameboid processes, and by
Medulla spinalis
Spinal ganglion
Notoehord
Sympathetic ganglion
Inferior vena cava
Common iliac artery
Ureter
Mesovarium
Fig
1111. — Transverse section of human embryo eight
and a half to nine weeks old. (From model by Keibel.)
Uterine tube
Germinal epithelium
Medtdla —
Plica peritonalis
tubce
EpoSphoron
Bete
Mcsonephros
Uterine tube
FiQ. 1112. — Ijongitudinal section of ovary of cat embryo of 9.4 cm. long. Schematic, (.\fter Coert.)
' Journal of Anatomy and Phys ology, vol. xxxviii.
1210
SPLANCHNOLOGY
the fact that their cytoplasm has no affinity for ordinary stains, but assumes a brownish tinge
when treated by osmic acid. The path along which they travel into the embryo is a very definite
one, viz., "from the yolk sac upward between the splanchnopleure and gut in the hinder portion
of the embryo." This pathwa}', named by Beard the germinal path, "leads them directly to the
position which they ought finally to take up in the 'germinal ridge' or nidus." A considerable
number apparently never reach their proper destination, since "vagrant germ cells are found in
all sorts of places, but more particularly on the mesentery." Some of these may possibly find
their way into the germinal ridge; some probably undergo atrophy, while others may persist
and become the seat of dermoid tumors.
Genital cord
Germinal
epithelium
Priinitive ova
CcU-nest
Blood-vessel -
Ovarian follicle -
Fia. 1113. — Section of the ovary of a newly born child. (Waldeyer.)
Epithelium
Tunica
albuginea
■•Interstitial
cell
i^%]^m^
Supporting
cell
The Testis. — The testis is developed in much the same way as the ovary. Like
the ovary, in its earhest stages it consists of a central mass of epithelium covered
by a surface epithelium. In the central mass a series of cords appear (Fig. 1114),
and the periphery of the mass is con-
verted into the tunica albuginea, thus
excluding the surface epithelium from
any part in the formation of the
tissue of the testis. The cords of
the central mass run together toward
the future hilus and form a network
which ultimately becomes the rete
testis. From the cords the seminifer-
ous tubules are de\eloped, and be-
tween them connective-tissue septa
extend. The seminiferous tubules
become connected with outgrowths
from the Wolffian body, which, as
before mentioned, form the efferent
ducts of the testis.
Descent of the Testes. — The testes,
at an early period of fetal life, are
placed at the back part of the ab-
dominal cavity, behind the perito-
neum, and each is attached by a
peritoneal fold, the mesorchium, to the mesonephros. From the front of the meso-
nephros a fold of peritoneum termed the inguinal fold grows forward to meet and
fuse with a peritoneal fold, the inguinal crest, which grows backward from the
\i
Genital
cell
FiQ. 1 1 14. — Section of a genital cord of the testis of a human
embryo 3.5 cm. long. (Felix and Biihler.)
DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS 1211
antero-lateral abdominal wall. The testis thus acquires an indirect connection
with the anterior abdominal wall; and at the same time a portion of the peri-
toneal cavity lateral to these fused folds is marked off as the future saccus vagi-
nalis. In the inguinal crest a peculiar structure, the gubernaculum testis, makes
its appearance. This is at first a slender band, extending from that part of the
skin of the groin which afterward forms the scrotum through the inguinal
canal to the body and epididymis of the testis. As development advances, the
peritoneum enclosing the gubernaculum forms two folds, one above the testis
and the other below it. The one above the testis is the plica vascularis, and con-
tains ultimately the internal spermatic vessels; the one below, the plica guber-
natrix, contains the lower part of the gubernaculum, which has now grown into
a thick cord; it ends below at the abdominal inguinal ring in a tube of peritoneum,
the saccus vaginalis, which protrudes itself down the inguinal canal. By the fifth
month the lower part of the gubernaculum has become a thick cord, while the
upper part has disappeared. The lower part now consists of a central core of
unstriped muscle fiber, and outside this of a firm layer of striped elements, con-
nected, behind the peritoneum, with the abdominal wall. As the scrotum develops,
the main portion of the lower end of the gubernaculum is carried, with the skin
to which it is attached, to the bottom of this pouch; other bands are carried to
the medial side of the thigh and to the perineum. The tube of peritoneum con-
stituting the saccus vaginalis projects itself downward into the inguinal canal,
and emerges at the cutaneous inguinal ring, pushing before it a part of the Obliquus
internus and the aponeurosis of the Obliquus externus, which form respectively
the Cremaster muscle and the intercrural fascia. It forms a gradually elongating
pouch, which eventually reaches the bottom of the scrotum, and behind this pouch
the testis is drawn by the growth of the body of the fetus, for the gubernaculum
does not grow commensurately with the growth of other parts, and therefore
the testis, being attached by the gubernaculum to the bottom of the scrotum,
is prevented from rising as the body grows, and is drawn first into the inguinal
canal and eventually into the scrotum. It seems certain also that the guber-
nacular cord becomes shortened as development proceeds, and this assists in caus-
ing the testis to reach the bottom of the scrotum. By the end of the eighth month
the testis has reached the scrotum, preceded by the saccus vaginalis, which com-
municates by its upper extremity with the peritoneal cavity. Just before birth
the upper part of the saccus vaginalis usually becomes closed, and this obliteration
extends gradually downward to within a short distance of the testis. The process
of peritoneum surrounding the testis is now entirely cut off from the general peri-
toneal cavity and constitutes the tunica vaginalis.
Descent of the Ovaries. — -In the female there is also a gubernaculum, which
effects a considerable change in the position of the ovary, though not so extensive
a change as in that of the testis. The gubernaculum in the female lies in contact
with the fundus of the uterus and contracts adhesions to this organ, and thus
the ovary is prevented from descending below this level. The part of the guber-
naculum between the ovary and the uterus becomes ultimately the proper ligament
of the ovary, while the part between the uterus and the labium majus forms the
round ligament of the uterus. A pouch of peritoneum analogous to the saccus
vaginalis in the male accompanies it along the inguinal canal: it is called the canal
of Nuck. In rare cases the gubernaculum may fail to contract adhesions to the
uterus, and then the ovary descends through the inguinal canal into the labium
majus, and under these circumstances its position resembles that of the testis.
The Metanephros and the Permanent Kidney. — The rudiments of the perma-
nent kidneys make their appearance about the end of the first or the beginning
of the second month. Each kidney has a two-fold origin, part arising from the
metanephros, and part as a diverticulum from the hind-end of the Wolffian duct.
1212
SPLANCHNOLOGY
close to where the latter opens into the cloaca-(Figs. 1115, 1116). The metanephros
arises in the intermediate cell mass, caudal to the mesonephros, which it resembles
in structure. The diverticulum from the Wolffian duct grows dorsalward and
forward along the posterior abdominal wall, where its blind extremity expands
and subsequently divides into several buds, which form the rudiments of the
pelvis and calyces of the kidney; by continued growth and subdivision it gives
Wolffian duct
Mlantois \ Kidney diverticulum
Umbilical cord \ Rectvui
Umbilical vessels
Hind-gut
yotochord
Fig. It 15. — Tail end of human embryo twenty-
five to twenty-nine days old. (From model by Keibel.)
Fig. 1116. — Tail end of human embryo thirty-two
to thirty-three days old. (From model by Keibel.)
Ureter
Wolffian duct \
Miillerian duct
Bladder
Symphysis pubis
rise to the collecting tubules of the kidney. The proximal portion of the diver-
ticulum becomes the ureter. The secretory tubules are developed from the
metanephros, which is moulded over the growing end of the diverticulum from the
Wolffian duct. The tubules of the metanephros, unlike those of the pronephros
and mesonephros, do not open into the Wolffian duct. One end expands to form
a glomerulus, while the rest of the tubule rapidly elongates to form the convoluted
and straight tubules, the loops of Henle, and the connecting tubules; these last
join and establish communications
with the collecting tubules derived
from the ultimate ramifications of the
diverticulum from the Wolffian duct.
The mesoderm around the tubules be-
comes condensed to form the connec-
tive tissue of the kidney. The ureter
opens at first into the hind-end of the
Wolffian duct; after the sixth week it
separates from the Wolffian duct, and
opens independently into the part of
the cloaca which ultimately becomes
the bladder (Figs. 1117, iflS).
The secretory tubules of the kid-
ney become arranged into pyramidal
masses or lobules, and the lobulated
condition of the kidneys exists for
some time after birth, while traces of
it may be found even in the adult. The kidney of the ox and many other animals
remains lobulated throughout life.
The Urinary Bladder. — The bladder is formed partly from the entodermal
cloaca and partly from the ends of the Wolffian ducts; the allantois takes no share
in its formation. After the separation of the rectum from the dorsal part of the
cloaca (p. 1109), the ventral part becomes subdivided into three portions: (1) an
anterior vesico-urethral portion, continuous with the allantois — into this portion the
Wolffian ducts open; (2) an intermediate narrow channel, the pelvic portion; and
Glaus penis
Urethra
Vertebral column
Fig. 1117. — Tail end of human embryo; from eight and a
half to nine weeks old. (From model by Keibel.)
DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS 1213
(3) a posterior phallic portion, closed externally by the urogenital membrane (Fig.
1118). The second and third parts together constitute the urogenital sinus. The
vesico-urethral portion absorbs the ends of the Wolffian ducts and the associated
ends of the renal diverticula, and these give rise to the trigone of the bladder and
part of the prostatic urethra. The remainder of the vesico-urethral portion forms
the body of the bladder and part of the prostatic urethra; its apex is prolonged to
the umbilicus as a narrow canal, which later is obliterated and becomes the medial
umbilical ligament (urachus).
Wolffian duct —
-w^
Hind-gut
Bladder
Outer zoue\
) of kidney
Inner zone J
Pelvia of kidney
Urogenital
memhrane
Fig. 1118. — Primitive kidney and bladder, from a reconstruction. (After Schreiner.)
The Prostate. — The prostate originally consists of two separate portions, each
of which arises as a series of diverticular buds from the epithelial lining of the uro-
genital sinus and vesico-urethral part of the cloaca, between the third and fourth
months. These buds become tubular, and form the glandular substance of the two
lobes, which ultimately meet and fuse behind the urethra and also extend on to its
ventral aspect. The isthmus or middle lobe is formed as an extension of the lateral
lobes between the common ejaculatory ducts and the bladder. Skene's ducts in the
female urethra are regarded as the homologues of the prostatic glands.
The bulbo-urethral glands of Cowper in the male, and greater vestibular glands
of Bartholin in the female, also arise as diverticula from the epithelial lining of the
urogenital sinus.
The External Organs of Generation (Fig. 1119). — As already stated (page 1109),
the cloacal membrane, composed of ectoderm and entoderm, originally reaches from
the umbilicus to the tail. The mesoderm extends to the mid ventral line for some
distance behind the umbilicus, and forms the lower part of the abdominal wall;
it ends below in a prominent swelling, the cloacal tubercle. Behind this tubercle
the urogenital part of the cloacal membrane separates the ingrowing sheets of
mesoderm.
The first rudiment of the penis (or clitoris) is a structure termed the phallus; it
is derived from the phallic portion of the cloaca which has extended on to the
end and sides of the under surface of the cloacal tubercle. The terminal part of
the phallus representing the future glans becomes solid; the remainder, which
is hollow, is converted into a longitudinal groove by the absorption of the
urogenital membrane.
In the female a deep groove forms around the phallus and separates it from the
rest of the cloacal tubercle, which is now termed the genital tubercle. The sides of
1214
SPLANCHNOLOGY
the genital tubercle grow backward as the genital swellings, which ultimately form
the labia majora; the tubercle itself becomes the mons pubis. The labia minora
arise by the continued growth of the lips of the groove on the under surface of the
phallus; the remainder of the phallus forms the clitoris.
Umbilical cord
Genital tubercle
Hind-limb
Cloaca
Tail
~ Genital tubercle
— Labinm majiis
Labium minun
Urogenital
membraive
D
Glanx penis
Scrotal sivelling
Edge of groove on jjhalbix
Opening of urogenital ginu!!
Perineum
Anug
Glans clitoridig
Labium majus
Labium minus
Opening of
urogenital sinus
Perineum,
A n us
y'^__Mi
PI !}^/
Glans penis
Cavernous urethra
Scrotum,
Raphe
Preinice
Glans clitoridii
Labium majus
Labium minus
Vestibule
Vaginal orifice
t
• AnuA
)r-r
Anus
FiQ. 1119. — Stages in the development of the external sexual organs in the male and female. (Drawn from the
Ecker-Ziegler models.)
'In the male the early changes are similar, but the pelvic portion of the cloaca
undergoes much greater development, pushing before it the phallic portion. The
genital swellings extend around between the pelvic portion and the anus, and form a
scrotal area; during the changes associated with the descent of the testes this area
is drawn out to form the scrotal sacs. The penis is developed from the phallus.
As in the female, the urogenital membrane undergoes absorption, forming a channel
on the under surface of the phallus; this channel extends onl}' as far forward as the
corona glandis.
The corpora cavernosa of the penis (or clitoris) and of the urethra arise from the
THE KIDNEYS 1215
mesodermal tissue in the phallus; they are at first dense structures, but later
vascular spaces appear in them, and they gradually become cavernous.
The prepuce in both sexes is formed by the growth of a solid plate of ectoderm
into the superficial part of the phallus; on coronal section this plate presents the
shape of a horseshoe. By the breaking down of its more centrally situated cells
the plate is split into two lamella?, and a cutaneous fold, the prepuce, is liberated
and forms a hood over the glans. "Adherent prepuce is not an adhesion really,
but a hindered central desquamation" (Berry Hart, op. cit.).
The Urethra. — As already described, in both sexes the phallic portion of the
cloaca extends on to the under surface of the cloacal tubercle as far forward as the
apex. At the apex the walls of the phallic portion come together and fuse, the
lumen is obliterated, and a solid plate, the urethral plate, is formed. The remainder
of the phallic portion is for a time tubular, and then, by the absorption of the
urogenital membrane, it establishes a communication with the exterior; this open-
ing is the primitive urogenital ostium, and it extends forward to the corona glandis.
In the female this condition is largely retained; the portion of the groove on the
clitoris broadens out while the body of the clitoris enlarges, and thus the adult
urethral opening is situated behind the base of the clitoris.
In the male, by the greater growth of the pelvic portion of the cloaca a longer
urethra is formed, and the primitive ostium is carried forward with the phallus,
but it still ends at the corona glandis. Later it closes from behind forward. Mean-
while the urethral plate of the glans breaks down centrally to form a median
groove continuous with the primitive ostium. This groove also closes from behind
forward, so that the external urethral opening is shifted forward to the end of
the glans.
THE URINARY ORGANS.
The urinary organs comprise the kidneys, which secrete the urine, the ureters,
or ducts, which convey urine to the urinary bladder, where it is for a time retained;
and the urethra, through which it is discharged from the body.
The Kidneys (Renes).
The kidneys are situated in the posterior part of the abdomen, one on either side
of the vertebral column, behind the peritoneum, and surrounded by a mass of fat
and loose areolar tissue. Their upper extremities are on a level with the upper
border of the twelfth thoracic vertebra, their lower extremities on a level with the
third lumbar. The right kidney is usually slightly lower than the left, probably
on account of the vicinity of the liver. The long axis of each kidney is directed
downward and lateralward; the transverse axis backward and lateralward.
Each kidney is about 11.25 cm. in length, 5 to 7.5 cm. in breadth, and rather
more than 2.5 cm. in thickness. The left is somewhat longer, and narrower, than
the right. The weight of the kidney in the adult male varies from 125 to 170 gm.,
in the adult female from 115 to 155 gm. The combined weight of the two
kidneys in proportion to that of the body is about 1 to 240.
The kidney has a characteristic form, and presents for examination two surfaces,
two borders, and an upper and lower extremity.
Relations. — The anterior surface (fades anterior) (Figs. 1120 and 1122) of
each kidney is convex, and looks forward and lateralward. Its relations to
adjacent viscera differ so completely on the two sides that separate descriptions
are necessary.
Anterior Surface of Right Kidney. — A narrow portion at the upper extremity is in
relation with the right suprarenal gland. A large area just below this and involv-
ing about three-fourths of the surface, lies in the renal impression on the inferior
1216
SPLANCHNOLOGY
surface of the liver, and a narrow but some\\'hat variable area near the medial
border is in contact with the descending part of the duodenum. The lower part of
Great splanchnic
nerve piercing
cms.
Reeeptaculum
chyli.
Semiluna
ganglion.
Great splanchnic
nerve piercing
crus.
Semilunar
ganqlion.
Fig. 1120. — The relations of the viscera and large vessels of the abdomen. (Seen from behind, the last thoracic
vertebra being well raised.)
the anterior surface is in contact laterally with the right colic flexure, and medially,
as a rule, with the small intestine. The areas in relation with the liver and small
THE KIDNEYS
1217
intestine are covered by peritoneum; tiie suprarenal, duodenal, and colic areas
are devoid of peritoneum.
Anterior Surface of Left Kidney. — A small area along the upper part of the medial
border is in relation with the left suprarenal gland, and close to the lateral
border is a long strip in contact with the renal impression on the spleen. A
somewhat quadrilateral field, about the middle of the anterior surface, marks the
site of contact with the body of the pancreas, on the deep surface of which are the
lienal vessels. Above this is a small triangular portion, between the suprarenal
and splenic areas, in contact with the postero-inferior surface of the stomach.
Below the pancreatic area the lateral ])art is in relation with the left colic flexure.
INFERIOR PHRENIC
ARTERIES
SUPERIOR
MESENTERIC
ARTERY
INFERIOR
MESENTERIC
ARTERY
COMMON
ILIAC ARTERY
AND VEIN
CCELIAC
ARTERY
INTERNAL
SPERMATIC
ARTERY
AND VEIN
INTERNAL
ILIAC ARTERY
HETER
^ — ILIAC .
^M AND U
Fig. 1121. — Posterior abdominal wall, after removal of the peritoneum, showing kidneys, suprarenal capsules, and
great vessels. (Corning).
the medial with the small intestine. The areas in contact with the stomach and
spleen are covered by the peritoneum of the omental bursa, while that in relation
to the small intestine is covered by the peritoneum of the general cavity; behind
the latter are some branches of the left colic vessels. The suprarenal, pancreatic,
and colic areas are devoid of peritoneum.
The Posterior Surface (fades posterior) (Figs. 1123, 1124). — The posterior surface
of each kidney is directed backward and medialward. It is imbedded in areolar
and fatty tissue and entirely devoid of peritoneal covering. It lies upon the dia-
phragm, the medial and lateral lumbocostal arches, the Psoas major, the Quadratus
77
1218
SPLANCHNOLOGY
lumborum, and the tendon of the Transversus abdominis, the subcostal, and one
or two of the upper lumbar arteries, and the last thoracic, iliohypogastric, and
ilioinguinal nerves. The right kidney rests upon the twelfth rib, the left usually
on the eleventh and twelfth. The diaphragm separates the kidney from the
SUPRARENAL AREA
SUPRARENAL AREA
FERlOfS'
VENA
CAVA'
Fig. 1122. — The anterior surfaces of the kidneys, showing the areas of contact of neighboring viscera
pleura, which dips down to form the phrenicocostal sinus, but frequently the
muscular fibers of the diaphragm are defective or absent over a triangular area
immediately above the lateral lumbocostal arch, and when this is the case the
perinephric areolar tissue is in contact with the diaphragmatic pleura.
ELEVENTH RIB
TWELFTH RIB
TRANSVERSE PROCESSES
OF FIRST LUMBAR VERTEBRA
TWELFTH RIB
TRANSVERSE PROCESS
OF SECOND LUMBAR
VERTEBRA
Fig. 1123. — The posterior surfaces of the kidneys, showing areas of relation to the parietes.
Borders. — The lateral border {margo lateralis; external border) is convex, and is
directed toward the postero-lateral wall of the abdomen. On the left side it is in
contact at its upper part, with the spleen.
THE KIDNEYS
1219
The medial border {margo medialis; internal border) is concave in the center and
convex toward either extremity; it is directed forward and a httle downward.
Fig. 1124. — The relations of the kidneys from behind.
Its central part presents a deep longitudinal fissure, bounded by prominent over-
hanging anterior and posterior lips. This fissure is named the hilum, and transmits
the vessels, nerves, and ureter.
Above the hilum the medial
border is in relation with the
suprarenal gland ; below the hilum,
with the ureter.
Extremities. — The superior ex-
tremity (extremitas superior) is
thick and rounded, and is nearer
the median line than the lower; it
is surmounted by the suprarenal
gland, which covers also a small
portion of the anterior surface.
The inferior extremity (extrem-
itas inferior) is smaller and thin-
ner than the superior and farther
from the median line. It extends
to within 5 cm. of the iliac crest.
The relative position of the
main structures in the hilum is as
follows: the vein is in front, the
artery in the middle, and the
ureter behind and directed down-
ward. Frequently, however,
branches of both artery and
1 J L u* J xl- "^ J. Fig. 1125. — Sagittal section through posterior abdominal wall,
Vem are piaced benma tne ureter. showing the relations of the capsule of the kidney. (After Gerota).
Eleventh rib
Twelfth rib
Posterior
lamella of
renal fascia
Paranephric
body
Peritoneum
Vessels of hilum
of kidney
fill Section of
'bright colic
flexure
1220
SPLANCHXOLOGY
Fixation of the Kidney (Figs. 1125, 1126). — The kidney and its vessels are im-
bedded in a mass of fatty tissue, termed the adipose capsule, which is thickest at
the margins of the kidney and is prolonged through the hilum into the renal sinus.
The kidney and the adipose capsule are enclosed in a sheath of fibrous tissue con-
tinuous with the subperitoneal fascia, and named the renal fascia. At the lateral
border of the kidney the renal fascia splits into an anterior and a posterior layer.
The anterior layer is carried medialward in front of the kidney and its vessels,
and is continuous over the aorta with the corresponding layer of the opposite
side. The posterior layer extends medialward behind the kidney and blends with
the fascia on the Quadratus lumborum and Psoas major, and through this fascia
is attached to the vertebral column. Above the suprarenal gland the two layers
of the renal fascia fuse, and unite with the fascia of the diaphragm; below they
remain separate, and are gradually lost in the subperitoneal fascia of the iliac
fossa. The renal fascia is connected to the fibrous tunic of the kidney by numerous
trabeculfe, which traverse the adipose capsule; and are strongest near the lower
end of the organ. Behind the fascia renalis is a considerable quantity of fat, which
constitutes the paranephric body. The kidney is held in position partly through
the attachment of the renal fascia and partly by the apposition of the neighboring
viscera.
Subperitoneal fascia
Anterior lamella of
renal fascia
Fig. 1126
1
Peritoneum
Adipose capsule
Paranephric body
Quadratus lumborum.
Sacrospinal is
-Transverse section, showing the relations of the capsule of the kidnej-. (After Gerota.)
. General Structure of the Kidney. — The kidney is invested by a fibrous tunic,
which forms a firm, smooth covering to the organ. The tunic can be easily stripped
off, but in doing so numerous fine processes of connective tissue and small blood^■essels
are torn through. Beneath this coat a thin, wide-meshed net-work of unstriped
muscular fiber forms an incomplete covering to the organ. When the capsule is
stripped oft', the surface of the kidney is found to be smooth and even and of a deep
red color. In infants fissures extending for some depth may be seen on the surface
of the organ, a remnant of the lobular construction of the gland. The kidney is
dense in texture, but is easily lacerable by mechanical force. If a vertical section
THE KIDNEYS
1221
J
of the kidney be made from its convex to its concave ht)rder, it will be seen that the
hilura expands into a central cavity, the renal sinus, this contains the upper part of
the renal pelvis and the calyces, surrounded by some fat in which are imbedded the
branches of the renal vessels and nerves. The renal sinus is lined by a prolongation
of the fibrous tunic, which is continued around the lips of the hilum. The renal
calyces, from seven to thirteen in number, are cup-shaped tubes, each of which
embraces one or more of the renal papilhc; they unite to form two or three short
tubes, and these in turn join to form a funnel-shaped sac, the renal pelvis. The
renal pehis, wide above and narrow below where it joins the ureter, is partly out-
side the renal sinns. The renal calyces and pelvis form the upper expanded end of
the excretory duct of the kidney.
The kidney is composed of an internal medullary and an external cortical substance.
The medullary substance {substantia medvUaris) consists of a series of red-colored
striated conical masses, termed the renal pyramids, the bases of which are directed
toward the circumference of the kidney, while their apices converge toward the
renal sinus, where they form prominent papilhe projecting into the interior of the
calyces.
The cortical substance {substantia corticalis) is reddish brown in color and soft and
granular in consistence. It lies immediately beneath the fibrous tunic, arches over
the bases of the pyramids, and dips in between
adjacent pyramids toward the renal sinus. The
parts dipping in between the pyramids are
named the renal columns (Bertini), while the
portions which connect the renal columns to
each other and intervene between the bases of
the pyramids and the fibrous tunic are called
the cortical arches (indicated between A and A'
in Fig. 1127). If the cortex be examined with a
lens, it will be seen to consist of a series of
lighter-colored, conical areas, termed the radiate
part, and a darker-colored intervening substance,
which from the complexity of its structure is
named the con\oluted part. The rays gradually
taper toward the circumference of the kidney,
and consist of a series of outward prolongations
from the base of each renal pyramid.
Minute Anatomy.— The renal tubules (Fig. 1028),
of which the kidney is for the most part made up.
commence in the cortical substance, and after pursuing
a very circuitous course through the cortical and medul-
lary substances, finally end at the apices of the renal
pyramids by open mouths, so that the fluid which
they contain is emptied, through the calyces, into the
pelvis of the kidney. If the surface of one of the
papillse be examined with a lens, it will be seen to be
studded over with minute openings, the orifices of the renal tubules, from sixteen to twenty
in number, and if pressure be made on a fresh kidney, urine will be seen to exude from these
orifices. The tubules commence in the convoluted part and renal columns as the renal cor-
puscles, which are small rounded masses of a deep red color, varying in size, but of an average
of about 0.2 mm. in diameter. Each of these little bodies is composed of two parts: a central
glomerulus of vessels, and a membranous envelope, the glomerular capsule {capsule of Bowman),
which is the small pouch-like commencement of a renal tubule.
The glomerulus is a lobulated net-work of convoluted capillary bloodvessels, held together
by scanty connective tissue. This capillary net-work is derived from a small arterial twig,
the afferent vessel, which enters the capsule, generally at a point opposite to that at which
the latter is connected with the tubule; and the resulting vein, the efferent vessel, emerges
from the capsule at the same pomt. The afferent vessel is usually the larger of the two
Fig. 1127 — Vertical section of kidney.
1222
SPLANCHNOLOGY
(Fig. 1129). The glomerular or Bowman's capsule, which surrounds the glomerulus, con-
sists of a basement membrane, lined on its inner surface by a layer of flattened epithelial cells.
Glomerular capsule Neck ist convoluted tubule
Afferent vessel
Efferent vessel
Intertubular capillaries
Interlobular vein
Interlobular artery
Spiral tubule
Henle's ( Ascending linih
loop \Descending limb
Arterial arch
Venous arch
Cortical substance
'--:':-\xf-\^~~i: • -Boundary zone
Medullary
substance
Duct of Bellini
Fig. 1128. — Scheme of renal tubule and its vascular supply.
which are reflected from the lining membrane on to the glomerulus, at the point of entrance or
exit of the afferent and efferent vessels. The whole surface of the glomerulus is covered with a
continuous layer of the same cells, on a delicate supporting membrane (Fig. 1130). Thus between
the glomerulus and the capsule a space is left, forming a cavity lined by a continuous layer of
„tcj;i^'
Fig. 1129. — Distribution of bloodvessels in cortex of kidney.
Fig. 1130. — Glomerulus.
squamous cells; this cavity varies in size according to the state of secretion and the amount of
fluid present in it. In the fetus and young subject the lining epithelial cells are polyhedral or even
columnar.
THE KIDNEYS
1223
The renal tubules, commencing in tlie niial corpuscles, present, during their course, many
changes in shape and direction, and are contained partly in the medullary and partly in the
cortical substance. At their junction with tiie glomerular capsule they exhibit a somewhat
constricted portion, which is termed the neck. Beyond thia the tubule becomes convoluted,
and pursues a considerable course in the cortical substance constituting the proximal convoluted
tube. After a time the convolutions disappear, and the tube approaches the meduIJary sub-
stance in a more or less spiral nmuiier; this section of the tubule has been called the spiral tube.
Throughout this portion of their course the renal tubules are contained entirely in the cortical
substance, and present a fairly uniform caliber. They now enter the medullary substance,
suddenly become much smaller, quite straight in direction, and dip down for a variable depth
into the pyramids, constituting the descending limb of Henle's loop. Bending on themselves,
they form what is termed the loop of Henle, and reascending, they become suddenly enlarged,
forming the ascending limb of Henle's loop, and reenter the cortical substance. This portion
of the tubule ascends for a short distance, when it again becomes dilated, irregular, and angular.
This section is termed the zigzag tubule; it ends in a convoluted tube, which resembles the
proximal convoluted tubule, and is called the distal convoluted tubule. This again terminates
in a narrow junctional tube, which enters the straight or collecting tube.
The straight or collecting tubes commence in the radiate part of the cortex, where they receive
the curved ends of the distal convoluted tubules. They unite at short intervals with one another,
the resulting tubes presenting a considerable increase in caliber, so that a series of comparatively
large tubes passes from the bases of the rays into the renal pyramids. In the medulla the tubes
of each pyramid converge to join a central tube {duct of Bellini) which finally opens on the summit
of one of the papilla?; the contents of the tube are therefore discharged into one of the calyces.
Structure of the Renal Tubules. — The renal tubules consist of a basement membrane lined with
epithelium. The epithelium varies considerably in different sections of the tubule. In the neck
the epithelium is continuous with that lining the glomerular capsule, and like it consists of
flattened cells each containing an oval nucleus (Fig. 1132). The two convoluted tubules, the
spiral and zigzag tubules and the ascending limb of Henle's loop, are lined by a type of epithelium
which is histologically the same in all. The cells are somewhat columnar in shape and dovetail
into one another of their lateral aspect. Each has a striated border next the lumen of the tube,
its inner part is granular and its outer portion vertically striated. The nucleus is spherical and
situated about the center of the cell. In the descend-
ing limb of Henle's loop the epithelium resembles that
found in the glomerular capsule and the commence-
ment of the tube, consisting of flat, clear epithelial
plates, each with an oval nucleus (Fig. 11.31). The
nuclei alternate on opposite surfaces of the tubule so
that the lumen remains fairly constant.
In the straight tube the epithelium is clear and
cubical: in its papillary portion. the cells are distinctly
columnar and transparent (Fig. 1132).
The Renal Bloodvessels. — The kidney is plentifully
supphed with blood (Fig. 1133) by the renal artery, a
large branch of the abdominal aorta. Before it enters
the kidney, each artery divides into four or five
branches which at the hilum lie mainly between the
renal vein and ureter, the vein being in front, the
ureter behind; one branch usually lies behind the
ureter. Each vessel gives off some small branches to
the suprarenal glands, to the ureter, land to the sur-
rounding cellular tissue and muscles. Frequently a
second renal artery, termed the inferior renal, is given
off from the abdominal aorta at a lower level, and suppUes the lower portion of the kidney,
while occasionally an additional artery enters the upper part of the kidney. The branches
of the renal artery, while in the sinus, give off a few twigs for the nutrition of the surround-
ing tissues, and end in the arteriae propriae renales, which enter the kidney proper in the
renal columns. Two of these pass to each renal pyramid, and run along its sides for its
entire length, giving off in their course the afferent vessels of the renal corpuscles in the renal
columns. Having arrived at the bases of the pj'ramids, they form arterial arches or arcades
which lie in the boundary zone between the bases of the pyramids and the cortical arches, and
break up into two distinct sets of branches devoted to the supply of the remaining portions
of the kidney.
The first set, the interlobular arteries (Fig. 1128), are given off at right angles from the side
of the arterial arcade looking toward the cortical substance, and pass directly outward between
the medullary rays to reach the fibrous tunic, where they end in the capillary net-work of this
part. These vessels do not anastomose with each other, but form what are called end-arteries.
Fig. 11.31. — Longitudinal section of de-
scending limb of Henle's loop a. Meinbrana
propria b Epithelium.
1224
SPLANCHNOLOGY
In their outward course they give off lateral branches; these are the afferent vessels for the
renal corpuscles (see page 1221); they enter the capsule, and end in the glomerulus. From
each tuft the corresponding efferent vessel arises, and, having made its egress from the capsule
near to the point where the afferent vessel enters, breaks up into a number of branches, which
form a dense plexus around the adjacent urinary tubes.
Convoluted tvbule
r— Glomerulus
— Neck of tvbule
Fig. 1132. — Section of cortex of human kidney.
The second set of branches from the arterial arcades supply the renal pyramids, which they
«nter at their bases; and, passing straight through their substance to their apices, terminate
in the venous plexuses found in that situation. They are called the arteriae rectae. The efferent
vessels from the glomeruli nearest the medulla break up into leashes of straight vessels {false
arterice recta) which pass do^m into the medulla and join the plexus of vessels there (Fig. 1128).
_FiG. 1133. — Transverse section of pyramidal substance of kidney of pig, the bloodvessels of which are injected.
<i'. Large collecting tube, cut across, lined with cylindrical epithelium. 6. Branch of collecting tube, cut across, lined
with cubical epithelium. c,_ d. Henle's loops cut across, e. Bloodvessels cut across. D Connective tissue ground
substance.
The renal veins arise from tliree sources, viz., the veins beneath the fibrous tunic, the plexuses
around the convoluted tubules in the cortex, and the plexuses situated at the apices of
the renal pyramids. The veins beneath the fibrous tunic (venae stellatae) are stellate in
arrangement, and are derived from the capillary net-work, into which the terminal branches of
the interlobular arteries break up. These join to form the interlobular veins, which pass inward
between the rays, receive branches from the plexuses around the convoluted tubules, and, having
.arrived at the bases of the renal pyramids, join with the venaj recta^, next to be described.
THE URETERS 1225
The venae rectae are branches from the plexuses at the apices of the medullary pyramids,
formed by the terminations of the arteriaj rectip. They run outward in a straight course between
the tubes of the medullary substance, and joining, as above stated, the interlobular veins, form
venous arcades; these in turn unite and form veins which pass along the sides of the pyramids
(Fig. 1128).
These vessels, venae propriae renales, accompany the arteries of the same name, running
along the entire length of the sides of the pyramids, and quit the kidney substance to enter the
sinus. In this cavity they join the corresponding veins from the other pyramids to form the
renal vein, which emerges from the kidney at the hilum and opens into the inferior vena cava;
the left vein is longer than the right, and crosses in front of the abdominal aorta.
The lymphatics of the kidney are described on page 712.
Nerves of the Kidney. — The nerves of the kidney, although small, are about fifteen in number.
They have small ganglia developed upon them, and are derived from the renal plexus, which is
formed by branches from the celiac plexus, the lower and outer part of the celiac ganglion and
aortic plexus, and from the lesser and lowest splanchnic nerves. They communicate with the
spermatic plexus, a circumstance which may explain the occurrence of pain in the testis in affec-
tions of the kidney. They accompany the renal artery and its branches, and are distributed to
the bloodvessels and to the cells of the urinary tubules.
Connective Tissue {intertubular stroma). — Although the tubules and vessels are closely
packed, a small amount of connective tissue, continuous with the fibrous tunic, binds them
firmly together and supports the bloodvessels, lymphatics, and nerves.
Variations.— Malformations of the kidney are not uncommon. There may be an entire
absence of one kidney, but, according to Morris, the number of these cases is "excessively
small": or there may be congenital atrophy of one kidney, when the kidney is very small, but
usually healthy in structure. These cases are of great importance, and must be duly taken into
account when nephrectomy is contemplated. A more common malformation is where the two
kidneys are fused together. They may be joined together only at their lower ends by means
of a thick mass of renal tissue, so as to form a horseshoe-shaped body, or they may be completely
united, forming a disk-like kidney, from which two ureters descend into the bladder. These fused
kidneys are generally situated in the middle line of the abdomen, but may be misplaced as well.
In some mammals, e. g., ox and bear, the kidney consists of a number of distinct lobules; this
lobulated condition is characteristic of the kidney of the human fetus, and traces of it may persist
in the adult. Sometimes the pelvis is dupKcated, while a double ureter is not very uncommon.
In some rare instances a third kidney may be present.
One or both kidneys may be misplaced as a congenital condition, and remain fixed in this
abnormal position. They are then very often misshapen. They may be situated higher, though
this is very uncommon, or lower than normal or removed farther from the vertebral column
than usual; or they may be displaced into the ihac fossa, over the sacroiliac joint, on to the
promontory of the sacrum, or into the pelvis between the rectum and bladder or by the side of
the uterus. In these latter cases they may give rise to very serious trouble. The kidney may also
be misplaced as a congenital condition, but may not be fixed; it is then known as a. floating kidney.
It is beheved to be due to the fact that the kidney is completely enveloped by peritoneum which
then passes backward to the vertebral column as a double layer, forming a mesonephron which
permits movement. The kidney may also be misplaced as an acquired condition; in these cases
the kidney is mobile in the tissues by which it is smrounded, moving with the capsule in the
perinephric tissues. This condition is known as movable kidney, and is more common in the female
than in the male. It occurs in badly nourished people, or in those who have become emaciated
from any cause. It must not be confounded with the floating kidney, which is a congenital
condition due to the development of a mesonephron. The two conditions cannot, however,
be distinguished until the abdomen is opened or the kidney explored from the loin.
The Ureters.
The ureters are the two tubes which convey the urine from the kidneys to the
urinary bladder. Each commences within the sinus of the corresponding kidney
as a niunber of short cup-shaped tubes, termed calyces, which encircle the renal
papilliE. Since a single calyx may enclose more than one papilla the calyces are
generally fewer in number than the pyramids — the former varying from seven to
thirteen, the latter from eight to eighteen. The calyces join to form two or three
short tubes, and these unite to form a funnel-shaped dilatation, wide above and
narrow below, named the renal pelvis, which is situated partly inside and partly
outside the renal sinus. It is usually placed on a level with the spinous process of
the first lumbar vertebra.
1226
SPLANCHNOLOGY
The Ureter Proper measures from 25 to 30 cm. in length, and is a thiek-walled
narrow cyhndrical tube which is directly continuous near the lower end of the
kidney with the tapering extremity of the renal pelvis. It runs downward and
medialward in front of the Psoas major and, entering the pelvic cavity, finally
opens into the fundus of the bladder.
The abdominal part (pars abdominaUs) lies behind the peritoneum on the medial
part of the Psoas major, and is crossed obliquely by the internal spermatic vessels.
It enters the pelvic cavity by crossing either the termination of the common, or
the commencement of the external, iliac vessels.
At its origin the right ureter is usually covered by the descending part of the
duodenum, and in its course downward lies to the right of the inferior vena cava,
and is crossed by the right colic and ileocolic vessels, while near the superior aperture
of the pelvis it passes behind the lower part of the mesentery and the terminal
part of the ileum. The left ureter is crossed by the left colic vessels, and near the
superior aperture of the pelvis passes behind the sigmoid colon and its mesentery.
The pelvic part (pars pelvina) runs at first downward on the lateral wall of the
pelvic cavity, along the anterior border of the greater sciatic notch' and under
cover of the peritoneum. It lies in front of the hypogastric artery medial to the
obturator nerve and the umbilical, obturator, inferior vesical, and middle hemor-
rhoidal arteries. Opposite the lower part of the greater sciatic foramen it inclines
medialward, and reaches the lateral angle of the bladder, where it is situated in
front of the upper end of the seminal vesicle and at a distance of about 5 cm.
from the opposite ureter; here the ductus deferens crosses to its medial side, and
the vesical veins surround it. Finally, the ureters run obliquely for about 2 cm.
through the wall of the bladder and open by slit-like apertures into the cavity
of the viscus at the lateral angles of the trigone. When the bladder is distended
the openings of the ureters are about 5 cm. apart, but when it is empty and con-
tracted the distance between them is diminished by one-half. Owing to their
oblique course through the coats
of the bladder, the upper and
lower walls of the terminal por-
tions of the ureters become closely
applied to each other when the
viscus is distended, and, acting as
valves, prevent regurgitation of
urine from the bladder.
In the female, the ureter forms,
as it lies in relation to the wall
of the pelvis, the posterior bound-
ary of a shallow depression named
the ovarian fossa, in which the
ovary is situated. It then runs
medialward and forward on the
lateral aspect of the cervix uteri
and upper part of the vagina to
reach the fundus of the bladder.
In this part of its course it is ac-
companied for about 2.5 cm. by
the uterine artery, which then
crosses in front of the ureter and
ascends between the two layers of
the broad ligament. The ureter
is distant about 2 cm. from the side of the cervix of the uterus. The ureter is
sometimes duplicated on one or both sides, and the two tubes may remain
-• — Fibrous tissue
Longitudinal
f mi^cular Jibtrs
Circular tmiscular
fibers
Subepithelial
connective tissut
Transitional
epithelium
Fig. 1134. — Transverse section of ureter.
THE URINARY BLADDER 1227
distinct as far as the fundus of the bladder. On rare occasions they open
separately into the bhidder cavity.
Structure (Fig. 1134). — The ureter is composed of three coats: fibrous, muscular, and mucous
coats.
The fibrous coat (tunica adventUia) is continuous at one end with the fibrous tunic of the kidney
on the fioor of the sinus; while at the other it is lost in the fibrous structure of the bladder.
In the renal pelvis the muscular coat {tunica muscularis) consists of two layers, longitudinal
and circular: the longitudinal fibers become lost upon the sides of the papillae at the extremities
of the calyces; the circular fibers may be traced surrounding the medullary substance in the
same situation. In the ureter proper the muscular fibers are very distinct, and are arranged
in three layers: an external longitudinal, a middle circular, and an internal, less distinct than
the other two, but having a general longitudinal direction. According to Kolhker this internal
layer is found only in the neighborhood of the bladder.
The mucous coat (tunica mucosa) is smooth, and presents a few longitudinal folds which
become effaced by distension. It is continuous with the mucous membrane of the bladder
below, while it is prolonged over the papilla; of the kidney above. Its epithelium is of a tran-
sitional character, and resembles that found in the bladder (see Fig. 1141). It consists of sev-
eral layers of cells, of which the innermost — that is to say, the cells in contact with the urine —
arc somewhat flattened, with concavities on their deep surfaces into which the rounded ends
of the cells of the second layer fit. These, the intermediate cells, more or less resemble columnar
epithehum, and are pear-shaped, with rounded internal extremities which fit into the concavities
of the cells of the first layer, and narrow external extremities which are wedged in between the
cells of the third layer. The external or third layer consists of conical or oval cells varying in
number in different parts, and presenting processes which extend down into the basement
membrane. Beneath the epithelium, and separating it from the muscular coats, is a dense layer
of fibrous tissue containing many elastic fibers.
Vessels and Nerves. — The arteries supplying the ureter are branches from the renal, internal
spermatic, hypogastric, and inferior vesical.
The nerves are derived from the inferior mesenteric, spermatic, and pelvic plexuses.
Variations. — The upper portion of the ureter is sometimes double; more rarely it is double the
greater part of its extent, or even completely so. In such cases there are two openings into the
bladder. Asymmetry in the.se variations is common.
The Urinary Bladder (Vesica Urinaria; Bladder) (Fig. 1135).
The urinary bladder is a musculomembranous sac which acts as a reservoir
for the urine; and as its size, position, and relations vary according to the amount
of fluid it contains, it is necessary to study it as it appears (a) when empty, and (b)
when distended. In both conditions the position of the bladder varies with the
condition of the rectum, being pushed upward and forward when the rectum is
distended.
The Empty Bladder. — When hardened in situ, the empty bladder has the
form of a flattened tetrahedron, with its vertex tilted forward. It presents a fundus,
a vertex, a superior and an inferior surface. The fundus (Fig. 1152) is triangular
in shape, and is directed downward and backward toward the rectum, from which
it is separated by the rectovesical fascia, the vesiculjg seminales, and the terminal
portions of the ductus defe rentes. The vertex is directed forward toward the upper
part of the symphysis pubis, and from it the middle umbilical ligament is continued
upward on the back of the anterior abdominal wall to the umbilicus. The peri-
toneum is carried by it from the vertex of the bladder on to the abdominal wall
to form the middle umbilical fold. The superior surface is triangular, bounded
on either side by a lateral border which separates it from the inferior surface, and
behind by a posterior border, represented by a line joining the two ureters, which
intervenes between it and the fundus. The lateral borders extend from the ureters
to the vertex, and from them the peritoneum is carried to the walls of the pelvis.
On either side of the bladder the peritoneum shows a depression, named the para-
vesical fossa (Fig. 1037). The superior surface is directed upward, is covered by peri-
toneum, and is in relation with the sigmoid colon and some of the coils of the small
intestine. When the bladder is empty and firmly contracted, this surface is convex
1228
SPLANCH^OLOGY
and the lateral and posterior borders are rounded ; whereas if the bladder be relaxed
it is concave, and the interior of the viscus, as seen in a median sagittal section,
presents the appearance of a V-shaped slit with a sliorter posterior and a longer
anterior limb — the apex of the V corresponding with the internal orifice of the
urethra. The inferior siuf ace is directed downward and is uncovered by peritoneum.
It may be divided into a posterior or prostatic area and two infero-lateral surfaces.
The prostatic area is somewhat triangular: it rests upon and is in direct continuity
with the base of the prostate; and from it the urethra emerges. The infero-lateral
portions of the inferior surface are directed downward and lateralward: in front,
they are separated from the symphysis pubis by a mass of fatty tissue which is
named the retropubic pad; behind, they are in contact with the fascia wdiich covers
the Levatores ani and Obturatores interni.
Ureter
Ductus deferens
Urethra
External urethral
orijice
Sacrum
liectovesical
excavation
Coccyx
Ejaculatory duct
— Anal canal
Fig. 1135. — Median sagitta section of male pelvis.
When the bladder is empty it is placed entirely within the pelvis, below the level
of the obliterated hypogastric arteries, and below the level of those portions of the
ductus deferentes which are in contact with the lateral wall of the pelvis; after
they cross the ureters the ductus deferentes come into contact with the fundus
of the bladder. As the viscus fills, its fundus, being more or less fixed, is only
slightly depressed; while its superior surface gradually rises into the abdominal
cavity, carrying with it its peritoneal covering, and at the same time rounding
off the posterior and lateral borders.
The Distended Bladder. — When the bladder is moderately full it contains
about 0.5 liter and assumes an oval form; the long diameter of the oval measures
about 12 cm. and is directed upward and forward. In this condition it presents
a postero-superior, an antero-inferior, and two lateral surfaces, a fundus and a
THE URINARY BLADDER
1229
summit. The postero-superior surface is directed upward and backward, and is cov-
ered by peritoneum: behind, it is separated from the rectum by the rectovesical
excavation, while its anterior part is in contact with the coils of the small intestine.
The antero-inferior surface is devoid of peritoneum, and rests, below, against the
pubic bones, above which it is in contact with the back of the anterior abdominal
wall. The lower parts of the lateral surfaces are destitute of peritoneum, and are
in contact with the lateral walls of the pelvis. The line of peritoneal reflection
from the lateral surface is raised to the level of the obliterated hypogastric artery.
The fundus undergoes little alteration in position, being only slightly lowered.
It exhibits, however, a narrow triangular area, which is separated from the rectum
merely by the rectovesical fascia. This area is bounded below by the prostate,
above by the rectovesical fold of peritoneum, and laterally by the ductus deferentes.
CORPUS
CAVERNOSUM
COWPER'S
GLAND
BULBO-
CAVERNOSUS
MUSCLE
Fia. 1136. — Male pelvic organs seen from right side,
bladder and rectum shown in blue.
Bladder aiid rectum distended; relations of peritoneum to the
The arrow points to the rectovesical pouch.
The ductus deferentes frequently come in contact with each other above the pros-
tate, and under such circumstances the lower part of the triangular area is obliter-
ated. The line of reflection of the peritoneum from the rectum to the bladder
appears to undergo little or no change when the latter is distended; it is situated
about 10 cm. from the anus. The summit is directed upward and forward above
the point of attachment of the middle umbilical ligament, and hence the peritoneum
which follows the ligament, forms a pouch of varying depth between the summit
of the bladder, and the anterior abdominal wall.
The Bladder in the Child (Figs. 1137, 1138).— In the newborn child the internal
urethral orifice is at the level of the upper border of the symphysis pubis; the
bladder therefore lies relatively at a much higher level in the infant than in the
adult. Its anterior surface " is in contact with about the lower two-thirds of that
1230
SPLANCHNOLOGY
part of the abdominal wall which lies between the symphysis pubis and the umbili-
cus" (Symington^). Its fundus is clothed with peritoneum as far as the level
of the internal orifice of the urethra. Although the bladder of the infant is usually
described as an abdominal organ, Symington has pointed out that only about
Symphysis pttbis
Urethra
Anal canal
Fig. 1137. — Sagittal section through the pelvis of a newly born male child.
one-half of it lies above the plane of the superior aperture of the pelvis. Disse
maintains that the internal urethral orifice sinks rapidly during the first three
years, and then more slowly until the ninth year, after which it remains stationary
until puberty, when it again slowly descends and reaches its adult position.
Vtermc tube
Cavity of uterus
Sigmoid colon
Rectum
Anal canal
Round ligament of
uterus
~ Bladder
Symphysis pubis
Urethra
Vagina
Fig. 1138. — Sagittal section through the pelvis of a newly born female child.
The Female Bladder (Fig. 1139). — In the female, the bladder is in relation
behind with the uterus and the upper part of the vagina. It is separated from the
anterior surface of the body of the uterus by the vesicouterine excavation, but
' The Anatomy of the Child.
THE URINARY BLADDER
1231
below the level of this excavation it is connected to the front of the cervix uteri
and the upper part of the anterior wall of the vagina })y areolar tissue. When
the bladder is empty the uterus rests upon its superior surface. The female bladder
is said by some to be more capacious than that of the male, but probably the
opposite is the case.
Sacrum
Coccyx
Sectovaginnl
excavation
External uterine
orifice
Anal canal
Uterovesical
excavation
Urethra
Fig. 1139. — Median sagittal section of female pelvis.
Ligaments. — The bladder is connected to the pelvic wall by the fascia endo-
pelvina. In front this fascial attachment is strengthened by a few muscular fibers,
the Pubovesicales, which extend from the back of the pubic bones to the front
of the bladder; behind, other muscular fibers run from the fundus of the bladder
to the sides of the rectum, in the sacrogenital folds, and constitute the Rectovesicales.
The vertex of the bladder is joined to the umbilicus by the remains of the urachus
which forms the middle umbilical ligament, a fibromuscular cord, broad at its
attachment to the bladder but narrowing as it ascends.
From the superior surface of the bladder the peritoneum is carried off in a series
of folds which are sometimes termed the false ligaments of the bladder. Anteriorly
there are three folds: the middle umbilical fold on the middle umbilical ligament,
and two lateral umbilical folds on the obliterated hypogastric arteries. The reflec-
tions of the peritoneum on to the side walls of the pelvis form the lateral false
ligaments, while the sacrogenital folds constitute posterior false ligaments.
Interior of the Bladder (Fig. 1140). — The mucous membrane lining the bladder
is, over the greater part of the viscus, loosely attached to the muscular coat, and
appears wrinkled or folded when the bladder is contracted : in the distended condi-
tion of the bladder the folds are effaced. Over a small triangular area, termed the
trigonum vesicae, immediately above and behind the internal orifice of the urethra,
the mucous membrane is firmlv bound to the muscular coat, and is alwavs smooth.
1232
SPLANCHNOLOGY
The anterior angle of the trigoniim vesicae is formed by the internal orifice of the
urethra: its postero-lateral angles by the orifices of the ureters. Stretching behind
the latter openings is a slightly curved ridge, the torus uretericus, forming the base
of the trigone and produ(?ed by an underlying bundle of non-striped muscular
fibers. The lateral parts of this ridge extend beyond the openings of the ureters,
and are named the plicae uretericse; they are produced by the terminal portions of
the ureters as they traverse obliqueh' the bladder Avail. When the bladder is
illuminated the torus uretericus appears as a pale band and forms an important
guide during the operation of introducing a catheter into the ureter.
Vertex
Int. urethral
orifice
L vuloB vesicas
Triyonum
vesiccB
Torus
uretericus
Orifce of
ureter
Fig. 1140. — The interior of bladder.
The orifices of the ureters are placed at the postero-lateral angles of the trigonum
vesicae, and are usually slit-like in form. In the contracted bladder they are about
2.5 cm. apart and about the same distance from the internal urethral orifice; in
the distended viscus these measurements may be increased to about 5 cm.
The internal urethral orifice is placed at the apex of the trigonum vesicae, in the
most dependent part of the bladder, and is usually somewhat crescentic in form;
the mucous membrane immediately behind it presents a slight elevation, the
uvula vesicae, caused by the middle lobe of the prostate.
.Structure (Fig. 1141). — The bladder is composed of the four coats: serous, muscular, sub-
mucous, and mucous coats.
The serous coat {tunica serosa) is a partial one, and is derived from the peritoneum. It invests
the superior surface and the upper parts of the lateral surfaces, and is reflected from these on
to the abdominal and pelvic walls.
The muscular coat {tunica inuscularis) consists of three layers of unstriped muscular fibers:
an external layer, composed of fibers having for the most part a longitudinal arrangement; a
middle layer, in which the fibers are arranged, more or less, in a circular manner; and an internal
layer, in which the fibers have a general longitudinal arrangement.
The fibers of the external layer arise from the posterior surface of the body of the pubis in both
sexes (musculi pubovesicales), and in the male from the adjacent p.art of the prostate and its
THE URINARY BLADDER
1233
-Svbinucous coat
Inner layer of
longitudinal
muscle fibers
Circular muscle
fibers
Outer layer of
longitudinal
muscle fibers
Fio. 1141. — Vertical section of bladder wall.
capsule. They pass, in a more or less longitudinal manner, up the inferior surface of the bladder,
over its vertex, and then descend along its fundus to become attached to the prostate in the
male, and to the front of the vagina in the female. At the sides of the bladder the fibers are
arranged obliquely and intersect one another. This
layer has been named the Detrusor urinae muscle.
The fibers of the middle circular layer are very
thinly and irregularly scattered on the body of the
organ, and, although to some extent placed trans-
versely to the long axis of the bladder, are for the
most part arranged obliquely. Toward the lower
part of the bladder, around tlie internal urethral
orifice, they are disposed in a thick circular layer,
forming the Sphincter vesicae, which is continuous
with the muscular fibers of the prostate.
The internal longitudinal layer is thin, and its
fasciculi have a reticular arrangement, but with a
tendency to assume for the most part a longitudinal
direction. Two bands of obhque fibers, originating
behind the orifices of the ureters, converge to the
back part of the prostate, and are inserted by means
of a fibrous process, into the middle lobe of tha,t
organ. They are the muscles of the ureters, de-
scribed by Sir C. Bell, who supposed that during
the contraction of the bladder they serve to retain
the oblique direction of the ureters, and so prevent
the reflux of the urine into them.
The submucous coat {tela submv^osa) consists of
a layer of areolar tissue, connecting together the
muscular and mucous coats, and intimately united
to the latter.
The mucous coat {tunica mucosa) is thin, smooth, and of a pale rose color. It is continuous
above through the ureters with the lining membrane of the "renal tubules, and below with that
of the urethra. The loose texture of the submucous layer allows the mucous coat to be thrown
into folds or rugce when the bladder is empty. Over the trigonum vesicic the mucous mem-
brane is closely attached to the muscular coat, and is not thrown into folds, but is smooth and
flat. The epithelium covering it is of the transitional variety, consisting of a superficial layer
of polyhedral flattened cells, each with one, two, or three nuclei; beneath these is a stratum
of large club-shaped cells, with their narrow extremities directed downward and wedged in
between smaller spindle-shaped cells, containing oval nuclei (Fig. 1141). The epithelium varies
according as the bladder is distended or contracted. In the former condition the superficial cells
are flattened and those of the other layers are shortened; in the latter they present the appear-
ance described above. There are no true glands in the mucous membrane of the bladder, though
certain mucous foUicles which exist, especially near the neck of the bladder, have been regarded
as such.
Vessels and Nerves. — The arteries supplying the bladder are the superior, middle, and inferior
vesical, derived from the anterior trunk of the hypogastric. The obturator and inferior gluteal
arteries also supply small visceral branches to the bladder, and in the female additional branches
are derived from the uterine and vaginal arteries.
The veins form a complicated plexus on the inferior surface, and fundus near the prostate, and
end in the hypogastric veins.
The lymphatics are described on page 712.
The nerves of the bladder are (1) fine medullated fibers from the third and fourth sacral nerves,
and (2) non-medullated fibers from the hypogastric plexus. They are connected with ganglia
in the outer and submucous coats and are finally distributed, all as non-medullated fibers, to the
muscular layer and epithelial lining of the viscus.
Abnormalities. — A defect of development, in which the bladder is imphcated, is known
under the name of extroversion of the bladder. In this condition the lower part of the abdominal
wall and the anterior wall of the bladder are wanting, so that the fundus of the bladder presents
on the abdominal surface, and is pushed forward by the pressure of the viscera within the abdomen,
forming a red vascular tumor on which the openings of the ureters are visible. The penis, except
the glans, is rudimentary and is cleft on its dorsal surface, exposing the floor of the urethra, a
condition known as epispadias. The pelvic bones are also arrested in development.
78
1234
SPLANCHNOLOGY
Urethral crest
Openings oj 'prostatic utricle
and ejaculatory ducts
Prostatic part of urethra
Memhranoiis part of urethra
The Male Urethra (Urethra Virilis) (Fig. 1142).
The male urethra extends from the internal urethral orifice in the urinary bladder
to the external urethral orifice at the end of the penis. It presents a double curve
in the ordinary relaxed state of the penis (Fig. 1137). Its length varies from 17.5
to 20 cm.; and it is divided into three portions, the prostatic, membranous, and
cavernous, the structure and rela-
tions of which are essentially
different. Except during the
passage of the urine or semen,
the greater part of the urethral
canal is a mere transverse cleft
or slit, with its upper and under
surfaces in contact ; at the external
orifice the slit is vertical, in the
membranous portion irregular or
stellate, and in the prostatic por-
tion somewhat arched.
The prostatic portion {pars pros-
tatica), the widest and most dila-
table part of the canal, is about
3 cm. long. It runs almost ver-
tically through the prostate from
its base to its apex, lying nearer
its anterior than its posterior
surface; the form of the canal
is spindle-shaped, being wider in
the middle than at either extrem-
ity, and narrowest below, where
it joins the membranous portion.
A transverse section of the canal
as it lies in the prostate is horse-
shoe-shaped, with the convexity
directed forward.
Upon the posterior wall or
Lacuna viagna ^p^^ is a narrow longitudinal
ridge, the urethral crest (veni-
inontaniim), formed by an eleva-
tion of the mucous membrane
and its subjacent tissue. It is
from 15 to. 17 mm. in length,
and about 3 mm. in height, and
contains, according to Kobelt, muscular and erectile tissue. When distended,
it may serve to prevent the passage of the semen backward into the bladder.
On either side of the crest is a slightly depressed fossa, the prostatic sinus, the floor
of which is perforated by numerous apertures, the orifices of the prostatic ducts
from the lateral lobes of the prostate; the ducts of the middle lobe open behind
the crest. At the forepart of the urethral crest, below its summit, is a median
elevation, the colliculus seminalis, upon or within the margins of which are the
orifices of the prostatic utricle and the slit-like openings of the ejaculatory ducts.
The prostatic utricle {sinus pocularis) forms a cul-de-sac about 6 mm. long, which
runs upward and backward in the substance of the prostate behind the middle
lobe. Its walls are composed of fibrous tissue, muscular fibers, and mucous
Small lacuna
Fig.
Ext, urethral orifice
1142. — The male urethra laid open on its anterior (upper)
surface.
THE MALE URETHRA 1235
membrane, and numerous small glands open on its inner surface. It was called
by Weber the uterus masculinus, from its being developed from the united
lower ends of the atrophied ]\liillerian ducts, and therefore homologous with the
uterus and vagina in the female.
The membranous portion {pars memhranacea) is the shortest, least dilatable,
and, with the exception of the external orifice, the narrowest part of the canal.
It extends downward and forward, with a slight anterior concavity, between the
apex of the prostate and the bulb of the urethra, perforating the urogenital dia-
phragm about 2.5 cm. below and behind the pubic symphysis. The hinder part
of the urethral bulb lies in apposition with the inferior fascia of the urogenital
diaphragm, but its upper portion diverges somewhat from this fascia: the anterior
wall of the membranous urethra is thus prolonged for a short distance in front
of the urogenital diaphragm; it measures about 2 cm. in length, while the posterior
wall which is between the two fasciae of the diaphragm is only 1.25 cm. long.
The membranous portion of the urethra is completely surrounded by the fibers
of the Sphincter urethree membranacese. In front of it the deep dorsal vein of
the penis enters the pelvis between the transverse ligament of the pelvis and the
arcuate pubic ligament; on either side near its termination are the bulbourethral
glands.
The cavernous portion {pars cavernosa; penile or spongy portion) is the longest
part of the urethra, and is contained in the corpus cavernosum urethrse. It is
about 15 cm. long, and extends from the termination of the membranous portion
to the external urethral orifice. Commencing below the inferior fascia of the
urogenital diaphragm it passes forward and upward to the front of the symphysis
pubis; and then, in the flaccid condition of the penis, it bends downward and
forward. It is narrow, and of uniform size in the body of the penis, measur-
ing about 6 mm. in diameter; it is dilated behind, within the bulb, and again
anteriorly within the glans penis, where it forms the fossa navicularis urethrae.
The external urethral orifice {orificium iiretkrce externum; meatus urinarms) is
the most contracted part of the urethra; it is a vertical slit, about 6 mm. long,
bounded on either side by two small labia.
The lining membrane of the urethra, especially on the floor of the cavernous
portion, presents the orifices of numerous mucous glands and follicles situated
in the submucous tissue, and named the urethral glands (Littre). Besides these
there are a number of small pit-like recesses, or lacunae, of varying sizes. Their
orifices are directed forward, so that they may easily intercept the point of a
catheter in its passage along the canal. One of these lacunae, larger than the rest,
is situated on the upper surface of the fossa navicularis; it is called the lacuna
magna. The bulbo-urethral glands open into the cavernous portion about 2.5 cm.
in front of the inferior fascia of the urogenital diaphragm.
Structure. — The urethra is composed of mucous membrane, supported by a submucous tissue
which connects it with tTie various structures through which it passes.
The mucous coat forms part of the genito-urinary mucous membrane. It is continuous with
the mucous membrane of the bladder, ureters, and kidneys; externally, with the integument
covering the glans penis; and is prolonged into the ducts of the glands which open into the urethra,
viz., the bulbo-urethral glands a: d the prostate; and into the ductus deferentes and vesicular
seminales, through the ejaculatory ducts. In the cavernous and membranous portions the mucous
membrane is arranged in longitudinal folds when the tube is empty. Small papillae are found
upon it, near the external urethral orifice; its epithehal lining is of the columnar variety except
near the external orifice, where it is squamous and stratified.
The submucous tissue consists of a vascular erectile layer; outside this is a layer of unstriped
muscular fibers, arranged in a circular direction, which separates the mucous membrane and
submucous tissue from the tissue of the corpus cavernosum urethra\
Congenital defects of the urethra occur occasionall3^ The one most frequently met with is
where there is a cleft on the floor of the urethra owing to an arrest of union in the middle hne.
This is knowii as hjpospadias, and the cleft may vary in extent. The simplest and by far the
1236 SPLANCHNOLOGY
most common form is where the deficiency is confined to the glans penis. The urethra ends at
the point where the extremity of the prepuce joins the body of the penis, in a small valve-Uke
opening. The prepuce is also cleft on its under surface and forms a sort of hood over the glans.
There is a depression on the glans in the position of the normal meatus. This condition produces
no disabihty and requires no treatment. In more severe cases the cavernous portion of the
urethra is cleft throughout its entire length, and the opening of the urethra is at the point of
junction of the penis and scrotum. The under surface of the penis in the middle line presents a
furrow Uned by a moist mucous membrane, on either side of wliich is often more or less dense
fibrous tissue stretching from the glans to the opening of the urethra, which prevents complete
erection taking place. Great discomfort is induced during micturition, and sexual connection is
impossible. The condition may be remedied by a series of plastic operations. The worst form
of this condition is where the urethra is deficient as far back as the perineum, and the scrotum
is cleft. The penis is small and bound dowTi between the two halves of the scrotum, so as to
resemble an hypertrophied chtoris. The testes are often retained. The condition of parts,
therefore, very much resembles the external organs of generation of the female, and many chil-
dren the victims of this malformation have been brought up as girls. The halves of the scrotum,
deficient of testes, resemble the labia, the cleft between them looks like the orifice of the vagina,
and the diminutive penis is taken for an enlarged clitoris. There is no remedj- for this condition.
A much more uncommon form of maKormation is where there is an apparent deficiency of the
upper wall of the urethra; this is named epispadias. The deficiency may vary in extent; when
it is complete the condition is associated with extroversion of the bladder. In less extensive cases,
where there is no extroversion, there is an infundibuUform opening into the bladder. The
penis is usually dwarfed and turned upward, so that the glans Ues over the opening. Con-
genital stricture is also occasionally met with, and in such cases multiple strictures may be
present throughout the whole length of the cavernous portion.
The Female Urethra (Urethra Muliebris) (Fig. 1139).
The female urethra is a narrow membranous canal, about 4 cm. long, extending
from the internal to the external urethral orifice. It is placed behind the sym-
phj'sis pubis, imbedded in the anterior wall of the vagina, and its direction is ob-
liquely downward and forward; it is slightly curved Avith the concavity directed
forward. Its diameter when undilated is about 6 mm. It perforates the fasciae
of the urogenital diaphragm, and its external orifice is situated directly in front
of the vaginal opening and about 2.5 cm. behind the glans clitoridis. The lining
membrane is thrown into longitudinal folds, one of which, placed along the floor
of the canal, is termed the urethral crest. Many small urethral glands open into
the urethra.
Structure. — The urethra consists of tlu-ee coats: muscular, erectile, and mucous.
The muscular coat is continuous with that of the bladder; it extends the whole length of the
tube, and consists of circular fibers. In addition to this, between the superior and inferior fascise
of the urogenital diaphragm, the female urethra is surrounded by the Sphincter urethrae mem-
branaccEe, as in-the male.
A thin layer of spongy erectile tissue, containing a plexus of large veins, intermixed with
bundles of unstriped muscular fibers, lies immediately beneath the mucous coat.
The mucous coat is pale; it is continuous externally with that of the vulva, and internally with
that of the bladder. It is lined by stratified squamous epithelium, which becomes transitional
near the bladder. Its external orifice is surrounded by a few mucous folUcles.
THE MALE GENITAL ORGANS (ORGANA GENITALIA VIRILIA).
The male genitals include the testes, the ductus deferentes, the vesiculse semi-
nales, the ejaculatory ducts, and the penis, together with the following accessory
structures, viz., the prostate and the bulbourethral glands.
The Testes and Their Coverings (Figs. 1143, 1144, 1145).
The testes are two glandular organs, which secrete the semen; they are suspended
in the scrotum by the spermatic cords. At an early period of fetal life the testes
are contained in the abdominal cavity, behind the peritoneum. Before birth they
THE TESTES A\D THEIR COVERINGS
1237
descend to the inguinal canal, along which they pass with the spermatic cord,
and, emerging at the subcutaneous inguinal ring, they descend into the scrotum,
becoming invested in their course by coverings derived from the serous, muscular,
and fibrous layers of the al)dominal parietes, as well as by the scrotum.
The coverings of the testes are, the
Cremaster.
Infundibuliform fascia.
Skm \
T\ * 4- • ^bc^otum.
Dartos tunic J
Intercrural fascia.
Tunica vaginalis.
RIGHT INGUINAL CA
(OPENED)
CREMASTERIC
AND FASC
INTERCO
FASC
PERSISTENT SEROUS
CAVITY AROUND
CORD EXCEPTIONAL
TUNICA VAGINALIS—
PARIETAL LAYER
INFUNDIBULIFORM
FASCIA
'SESSILE
HYDATID
RIGHT HALF OF SCROTUM SKIN
LEFT HALF OF SCROTUM
Fig. 1143. — The scrotum. On the left side the cavity of the tunica vaginalis has been opened; on the right side
only the layers superficial to the Cremaster have been removed. (Testut.)
The Scrotum is a cutaneous pouch which contains the testes and parts of the
spermatic cords. It is divided on its surface into two lateral portions by a ridge
or raphe, which is continued forward to the under surface of the penis, and backward,
along the middle line of the perineum to the anus. Of these two lateral portions
the left hangs lower than the right, to correspond with the greater length of the
left spermatic cord. Its external aspect varies under different circumstances:
thus, under the influence of warmth, and in old and debilitated persons, it becomes
elongated and flaccid; but, under the influence of cold, and in the young and
robust, it is short, corrugated, and closely applied to the testes.
The scrotum consists of two layers, the integument and the dartos tunic.
The Integument is very thin, of a brownish color, and generally thrown into
folds or rugae. It is provided with sebaceous follicles, the secretion of which has a
1238
SPLANCHNOLOGY
peculiar odor, and is beset with thinly scattered, crisp hairs, the roots of which
are seen through the skin.
The Dartos Tunic {tunica dartos) is a thin layer of non-striped muscular fibers,
continuous, around the base of the scrotum, with the two layers of the superficial
fascia of the groin and the perineum; it sends inward a septum, which divides
the scrotal pouch into two cavities for the testes, and extends between the raphe
and the under surface of the penis, as far as its root.
EXTERNAL
ABDOMINAL
RING
ACCESSORY
SLIP OF
ORIGIN OF
CREMASTER
MUSCLE
SPERMATIC
CORD
iiii vAs
DEFERENS
IIIF SPERMATIC
ARTERY
NERVE FILAMENTS
OF SPERMATIC
PLEXUS
CREMASTER
MUSCLE
SEPTUM OF
SCROTUM
DARTOS
DEFERENTIAL
ARTERY
INFUNDIBULIFORM
FASCIA
SPERMATIC
PLEXUS
EPIDIDYMIS
PARIETAL
LAYER OF
TUNICA
VAGINALIS
Fig. 1 144. — The scrotum. The penis has been turned upward, and the anterior wall of the scrotum has been removed.
On the right side, the spermatic cord, the infundibuliform fascia, and the Cremaster muscle are displayed; on the left
side, the infundibuliform fascia has been divided by a longitudinal incision passing along the front of the cord and the
testicle, and a portion of the parietal layer of the tunica vaginalis has been removed to display the testicle and a portion
of the head of the epididymis, which are covered by the visceral layer of the tunica vaginalis. (Toldt.)
The dartos tunic is closelv united to the skin externalh', but connected with
the subjacent parts by delicate areolar tissue, upon which it glides with the
greatest facility.
The Intercrural Fascia {intercolumnar or external spermatic fascia) is a thin
membrane, prolonged downward around the surface of the cord and testis (see
page 411). It is separated from the dartos tunic by loose areolar tissue.
The Cremaster consists of scattered bundles of muscular fibers connected
together into a continuous covering by intermediate areolar tissue (see page 414).
THE TESTES AND THEIR COVERINGS
1239
The Infundibuliform Fascia (tunica vaginalis communis [testis et funiculi sper-
matid]) is a thin layer, which loosely invests the cord; it is a continuation
downward of the transversalis fascia (see page 418).
The Tunica Vaginalis is described with the testes.
Skin
Dartog tunic
Intcrarural fascia —
Cremasteric fascia
Infundibuliform fascia
Parietal tunica vaginalis
Visceral tunica vaginalis
Tunica albuginea ■■-
A lobule of the testi< —
A septum
\
Mediastinum testis -
Sinus of epidldiimis -
Spermatic vein -
Epididymis ..
Lucius deferens ..
Artery to ductus -
Internal spcrma t ic a rtery -
Internal muscular tunic -
Fig. 1 145. — Transverse section through the left side of the scrotum and the left testis. The sac of tlie tunica
vaginalis is represented in a distended condition. (Diagrammatic.) (Deldpine.)
Vessels and Nerves. — The arteries supplying the coverings of the testes are: the superficial
and deep external pudendal branches of the femoral, the superficial perineal branch of the
internal pudendal, and the cremasteric branch from the inferior epigastric. The veins follow
the course of the corresponding arteries. The lymphatics end in the inguinal lymph glands.
The nerves are the ilioinguinal and lumbpinguinal branches of the lumbar plexus, the two
superficial perineal branches of the internal pudendal nerve, and the pudendal branch of the
posterior femoral cutaneous nerve.
The Inguinal Canal (canalis inguinalis) is described on page 418.
The Spermatic Covd (funiculus spermaticits) (Fig. 1146) extends from the abdom-
inal inguinal ring, where the structures of which it is composed converge, to the back
part of the testis. In the abdominal wall the cord passes obliquely along the
inguinal canal, lying at first beneath the Obliquus internus, and upon the fascia
transversalis; but nearer the pubis, it rests upon the inguinal and lacunar liga-
ments, having the aponeurosis of the Obliquus externus in front of it, and the
inguinal falx behind it. It then escapes at the subcutaneous ring, and descends
nearly vertically into the scrotum. The left cord is rather longer than the right,
consequently the left testis hangs somewhat lower than its fellow.
Structure of the Spermatic Cord. — The spermatic cord is composed of arteries, veins, lymphatics,,
nerves, and the excretory duct of the testis. These structures are connected together by areolar
tissue, and invested by the layers brought down by the testis in its descent.
The arteries of the cord are: the internal and external spermatics; and the artery to the ductus
deferens.
The internal spermatic artery, a branch of the abdominal aorta, escapes from the abdomen
at the abdominal inguinal ring, and accompanies the other constituents of the spermatic cord
along the inguinal canal and through the subcutaneous inguinal ring into the scrotum. It then
descends to the testis, and, becoming tortuous, divides into several branches, two or three of
which accompany the ductus deferens and supply the epididymis, anastomosing with the artery
of the ductus deferens: the others supply the substance of the testis.
1240
SPLANCHXOLOGY
The external spermatic artery is a branch of the inferior epigastric artery. It accompanies the
spermatic cord and supplies the coverings of the cord, anastomosing with the internal spermatic
artery.
The artery of the ducttLS deferens, a branch of the superior vesical, is a long, slender vessel, which
accompanies the ductus deferens, ramifying upon its coats, and anastomosing with the internal
spermatic artery near the testis.
OBLIQUE
MUSCL^
VAS
DEFERENS
SPERMATIC
CORO
Fig. 1146. — The spermatic cord in the inguinal canal. (Poirier and Charpy.)
The spermatic veins (Fig. 1147) emerge from the back of the testis, and receive tributaries from
the epididymis: they unite and form a convoluted plexus, the plexus pampinifonnis, which forms
the chief mass of the cord; the vessels composing this plexus are very numerous, and ascend along
the cord in front of the ductus deferens; below the subcutaneous inguinal ring they unite to form
three or four veins, which pass along the inguinal canal, and, entering the abdomen through the
abdominal inguinal ring, coalesce to form two veins. These again unite to form a single vein,
which opens on the right side into the inferior vena cava, at an acute angle, and on the left side
into the left renal vein, at a right angle.
The Isnmphatic vessels are described on page 713.
The nerves are the spermatic plexus from the sjTnpathetic, joined by filaments from the pelvic
plexus which accompany the artery of the ductus deferens.
The scrotum forms an admirable covering for the protection of the testes. These bodies, lying
suspended and loose in the cavity of the scrotum and surrounded by serous membrane, are
capable of great mobihty, and can therefore easily shp about within the scrotum and thus
avoid injuries from blows or squeezes. The skin of the scrotum is very elastic and capable
of great distension, and on accoimt of the looseness and amount of subcutaneous tissue, the
scrotum becomes greatly enlarged in cases of edema, to which this part is especially hable as
a result of its dependent position.
The Testes are suspended in the scrotum by the spermatic cords, the left testis
hanging somewhat lower than its fellow. The average dimensions of the testis
are from 4 to 5 cm. in length, 2.5 cm. in breadth, and 3 cm. in the antero-posterior
diameter; its weight varies from 10.5 to 14 gm. Each testis is of an oval form
(Fig. 1148), compressed laterally, and having an oblique position in the scrotum;
the upper extremity is directed forward and a little lateralward; the lower,
backward and a little medialward; the anterior convex border looks forward and
downward, the posterior or straight border, to which the cord is attached,
backward and upward.
THE TESTES AXD THEIR COVERINGS
1241
The anterior border and lateral surfaces, as well as both extremities of the organ,
are convex, free, smooth, and invested by the visceral layer of the tunica vaginalis.
Fig. 1147. — Spermatic veins. (Testut.)
Tail of
epididymis
Cremaster
Tunica vaginalis
Appendix of epididymis
Head of epididymis
Appendix of testis
Fig. 1148. — The right testis, exposed by laying open the tunica vaginalis.
1242 SPLANCHNOLOGY
The posterior border, to which the cord is attached, receives only a partial invest-
ment from that membrane. Lying upon the lateral edge of this posterior border
is a long, narrow, flattened body, named the epididymis.
The epididymis consists of a central portion or body; an upper enlarged extremity,
the head (globus major); and a lower pointed extremity, the tail (globus minor),
which is continuous with the ductus deferens, the duct of the testis. The head
is intimately connected with the upper end of the testis by means of the efferent
ductules of the gland; the tail is connected with the lower end by cellular tissue,
and a reflection of the tunica vaginalis. The lateral surface, head and tail of the
epididymis are free and covered by the serous membrane; the body is also com-
pletely invested by it, excepting along its posterior border; while between the
body and the testis is a pouch, named the sinus of the epididymis (digital fossa).
The epididymis is connected to the back of the testis by a fold of the serous
membrane.
Appendages of the Testis and Epididymis. — On the upper extremity of the testis,
just beneath the head of the epididymis, is a minute oval, sessile body, the appendix
of the testis (hydatid of Morgagni) ; it is the remnant of the upper end of the Miillerian
duct. On the head of the epididymis is a second small stalked appendage (some-
times duplicated) ; it is named the appendix of the epididymis (pedunculated hydatid),
and is usually regarded as a detached efferent duct.
The testis is invested by three tunics: the tunica vaginalis, tunica albuginea,
and tunica vasculosa.
The Tunica Vaginalis (tunica vaginalis propria testis) is the serous covering of
the testis. It is a pouch of serous membrane, derived from the saccus vaginalis
of the peritoneum, which in the fetus preceded the descent of the testis from the
abdomen into the scrotum. After its descent, that portion of the pouch which
extends from the abdominal inguinal ring to near the upper part of the gland
becomes obliterated; the lower portion remains as a shut sac, which invests the
surface of the testis, and is reflected on to the internal surface of the scrotum;
hence it may be described as consisting of a visceral and a parietal lamina.
The visceral lamina (lamina visceralis) covers the greater part of the testis and
epididymis, connecting the latter to the testis by means of a distinct fold. From
the posterior border of the gland it is reflected on to the internal surface of the
scrotum.
The parietal lamina (lamina parietalis) is far more extensive than the visceral,
extending upward for some distance in front and on the medial side of the cord,
and reaching below the testis. The inner surface of the tunica vaginalis is
smooth, and covered bv a laver of endothelial cells. The interval between the
visceral and parietal laminae constitutes the cavity of the tunica vaginalis.
The obliterated portion of the saccus vaginalis may generally be seen as a fibro-
cellular thread lying in the loose areolar tissue around the spermatic cord; some-
times this may be traced as a distinct band from the upper end of the inguinal
canal, where it is connected with the peritoneum, down to the tunica vaginalis;
sometimes it gradually becomes lost on the spermatic cord. Occasionally no trace
of it can be detected. In some cases it happens that the pouch of peritoneum does
not become obliterated, but the sac of the peritoneum communicates with the
tunica vaginalis. This may give rise to one of the varieties of oblique inguinal
hernia (page 1187). In other cases the pouch may contract, but not become
entirely obliterated; it then forms a minute canal leading from the peritoneum to
the tunica vaginalis.
The Tunica Albuginea is the fibrous covering of the testis. It is a dense membrane,
of a bluish-white color, composed of bundles of white fibrous tissue which interlace
in every direction. It is covered by the tunica vaginalis, except at the points of
attachment of the epididymis to the testis, and along its posterior border, where
THE TESTES AND THEIR COVERINGS
1243
the spermatic vessels enter the gland. It is applied to the tunica vasculosa over
the glandular substance of the testis, and, at its posterior border, is reflected
into the interior of the gland, forming an incomplete vertical septum, called the
mediastinum testis {corpus Highmori).
The mediastinum testis extends from the upper to near the lower extremity
of the gland, and is wider above than below. From its front and sides numerous
imperfect septa {trahecnJae) are given off, which radiate toward the surface of the
organ, and are attached to the tunica albuginea. They divide the interior of the
organ into a number of incomplete spaces which are somewhat cone-shaped, being
broad at their bases at the surface of the gland, and becoming narrower as they
converge to the mediastinum. The mediastinum supports the vessels and duct
of the testis in their passage to and from the substance of the gland.
The Tunica Vasculosa is the vascular layer of the testis, consisting of a plexus
of bloodvessels, held together by delicate areolar tissue. It clothes the inner sur-
face of the tunica albuginea and the different septa in the interior of the gland,
and therefore forms an internal investment to all the spaces of which the gland is
composed.
Structure. — ^The glandular structure of the testis consists of numerous lobules. Their number,
in a single testis, is estimated by Berres at 250, and by Ivrause at 400. They differ in size
according to their position, those in the middle of the gland being larger and longer. The
lobules (Fig. 1149) are conical in shape, the base being directed toward the circumference of the
organ, the apex toward the mediastinum. Each lobule
is contained in one of the intervals between the fibrous
septa which extend between the mediastinum testis
and the tunica albuginea, and consists of from one to
three, or more, minute convoluted tubes, the tubuli
seminiferi. The tubules may be separately unravelled,
by careful dissection under water, and may be seen to
commence either by free cecal ends or by anastomotic
loops. They are supported by loose connective tissue
which contains here and there groups of "interstitial
cells" containing yellow pigment granules. The total
number of tubules is estimated by Lauth at 840, and
the average length of each is 70 to 80 cm. Their diam-
eter varies from 0.12 to 0.3 mm. The tubules are pale
in color in early life, but in old age they acquire a deep
yellow tinge from containing much fatty matter. Each
tubule consists of a basement layer formed of lamin-
ated connective tissue containing numerous elastic fibers
with flattened cells between the layers and covered ex-
ternally by a layer of flattened epithelioid cells. Within
the basement membrane are epithelial cells arranged
in several irregular layers, which are not always clearly
separated, but which may be arranged in three different
groups (Fig. 1150). Among these cells may be seen the
spermatozoa in different stages of development. (1)
Lining, the basement membrane and forming the outer
zone is a layer of cubical cells, with small nuclei;
some of these enlarge to become spermatogonia. The
nuclei of some of the spermatogonia may be seen to be in process of indirect division {karyo-
kineses, page 37), and in consequence of this daughter cells are formed, which constitute the second
zone. (2) Within this first layer is to be seen a number of larger polyhedral cells, with clear
nuclei, arranged in two or three layers; these are the intermediate cells or spermatocytes. Most
of these cells are in a condition of karyokinetic division, and the cells which result from this
division form those of the next layer, the spermatoblasts or spermatids. (3) The third layer of
cells consists of the spermatoblasts or spermatids, and each of these, without further subdivision,
becomes a spermatozoon. The spermatids are small polyhedral cells, the nucleus of each of
which contains half the usual number of chromosomes. In addition to these three layers of cells
others are seen, which are termed the supporting cells {cells of Sertoli). They are elongated
and columnar, and project inward from the basement membrane toward the lumen of the tube.
As development of the spermatozoa proceeds the latter group themselves around the inner
extremities of the supporting cells. The nuclear portion of the spermatid, which is partly
Tunica vi
Tunica albuginea
Its septa
Fig. 1149. — Vertical section of the testis, to
show the arrangement of the ducts.
1244
SPLANCHNOLOGY
imbedded in the supporting cell, is differentiated to form the head of the spermatozoon, while
part of the cell protoplasm forms the middle piece and the tail is produced by an outgrowth
from the double centriole of the cell. Ultimately the heads are liberated and the spermatozoa
are set free. The structure of the spermatozoa is described on pages 42, 43.
In the apices of the lobules, the tubules become less convoluted, assume a nearly straight
course, and unite together to form from twenty to thirty larger ducts, of about 0.5 mm
diameter, and these, from their straight course, are called tubuli recti (Fig. 1149).
in
Spermatocyte
Spermatid
Cell of Sertoli
Spermatogonium
Spermatozoon
Fig. 11.50. — Transverse section of a tubule of the testis of a rat. X 250.
The tubuli recti enter the fibrous tissue of the mediastinum, and pass upward and backward,
forming, in their ascent, a close net-work of anastomosing tubes which are merely channels in
the fibrous stroma, lined by flattened epithelium, and having no proper walls; this constitutes the
rete testis. At the upper end of the mediastinum, the vessels of the rete testis terminate in from
twelve to fifteen or twenty ducts, the ductuli efferentes; they perforate the tunica albuginea,
and carry the seminal fluid from the testis to the epididymis. Their course is at first straight;
they then become enlarged, and exceedingly convoluted, and form a series of conical masses,
the coni vascuTosi, which together constitute the head of the epididymis. Each cone consists
of a single convoluted duct, from 15 to 20 cm. in length, the diameter of which gradually decreases
from the testis to the epididymis. Opposite the bases of the cones the efferent vessels open at
narrow intervals into a single duct, which constitutes, by its complex convolutions, the body
and tail of the epididymis. When the convolutions of this tube are unravelled, it measures
upward of 6 meters in length; it increases in diameter and thickness as it approaches the ductus
deferens. The convolutions are held together by fine areolar tissue, and by bands of fibrous
tissue.
Ciliated
epithelium
Spermatozoa
ill lumen
Fio. 1151. — Section of epididymis of guinea-pig. X 255.
The tubuli recti have very thin walls; like the channels of the rete testis they are lined by a
single layer of flattened epithelium. The ductuli efferentes and the tube of the epididymis have
walls of considerable thickness, on account of the presence in them of muscular tissue, which is
principally arranged in a circular manner. These tubes are lined by columnar ciliated epithe-
lium (Fig. 1151).
THE DUCTUS DEFERENS 1245
Peculiarities. — The testis, developed in the lumbar region, may be arrested or delayed in its
transit to the scrotum {crijplorchism). It may be retained in the abdomen; or it may be arrested at
the abdominal inguinal ring, or in the inguinal canal; or it may just pass out of the subcutaneous
inguinal ring without finding its way to the bottom of the scrotum. When retained in the abdo-
men it gives rise to no symptoms, other than the absence of the testis from the scrotum; but
when it is retained in the inguinal canal it is subjected to pressure and may become inflamed
and painful. The retained testis is probably functionally useless; so that a man in whom both
testes are retained {anarchism) is sterile, though he may not be impotent. The absence of one
testis is termed monorchism. When a testis is retained in the inguinal canal it is often compli-
cated with a congenital hernia, the funicular process of the peritoneum not being obliterated.
In addition to the cases above described, where there is some arrest in the descent of the testis,
this organ may descend through the inguinal canal, but may miss the scrotum and assume some
abnormal position. The most common form is where the testis, emerging at the subcutaneous
inguinal ring, slips down between the scrotum and thigh and comes to rest in the perineum.
This is known as perineal ectopia testis. With each variety of abnormality in the position of the
testis, it is very common to find concurrently a congenital hernia, or, if a hernia be not actually
present, the funicular process is usually patent, and almost invariably so if the testis is in the
inguinal canal.
The testis, finally reaching the scrotum, may occupy an abnormal position in it. It may be
inverted, so that its posterior or attached border is directed forward and the tunica vaginalis is
situated behind.
Fluid collections of a serous character are very frequently found in the scrotum. To these the
term hydrocele is applied. The most common form is the ordinary vaginal hydrocele, in which
the fluid is contained in the sac of the tunica vaginalis, which is separated, in its normal condition,
from the peritoneal cavity by the whole extent of the inguinal canal. In another form, the
congenital hydrocele, the fluid is in the sac of the tunica vaginalis, but this cavity communicates
with the general peritoneal cavity, its tubular process remaining pervious. A third variety,
known as an infantile hydrocele, occurs in those cases where the tubular process becomes obliter-
ated only at its upper part, at or near the abdominal inguinal ring. It resembles the vaginal
hydrocele, except as regards its shape, the collection of fluid extending up the cord into the inguinal
canal. Fourthly, the funicular process may become obliterated both at the abdominal inguinal
ring and above the epididymis, leaving a central unobliterated portion, which may become
distended with fluid, giving rise to a condition known as the encysted hydrocele of the cord.
The Ductus Deferens (Vas Deferens; Seminal Duct).
The ductus deferens, the excretory duct of the testis, is the continuation of the
-canal of the epididymis. Commencing at the lower part of the tail of the epididymis
it is at first very tortuous, but gradually becoming less twisted it ascends along
the posterior border of the testis and medial side of the epididymis, and, as a con-
stituent of the spermatic cord, traverses the inguinal canal to the abdominal
inguinal ring. Here it separates from the other structures of the cord, curves
around the lateral side of the inferior epigastric artery, and ascends for about
2.5 cm. in front of the external iliac artery. It is next directed backward and slightly
downward, and, crossing the external iliac vessels obliquely, enters the pelvic
cavity, where it lies between the peritoneal membrane and the lateral wall of the
pelvis, and descends on the medial side of the obliterated umbilical artery and the
obturator nerve and vessels. It then crosses in front of the ureter, and, reaching
the medial side of this tube, bends to form an acute angle, and runs medialward
and slightly forward between the fundus of the bladder and the upper end of
the seminal vesicle. Reaching the medial side of the seminal vesicle, it is directed
downward and medialward in contact with it, gradually approaching the opposite
ductus. Here it lies between the fundus of the bladder and the rectum, where it
is enclosed, together with the seminal vesicle, in a sheath derived from the recto-
vesical portion of the fascia endopelvina. Lastly, it is directed downward to the
base of the prostate, where it becomes greatly narrowed, and is joined at an acute
angle by the duct of the seminal vesicle to form the ejaculatory duct, which tra-
verses the prostate behind its middle lobe and opens into the prostatic portion
of the urethra, close to the orifice of the prostatic utricle. The ductus deferens
presents a hard and cord-like sensation to the fingers, and is of cylindrical form; its
1246
SPLANCHNOLOGY
walls are dense, and its canal is extremely small. At the fundus of the bladder
it becomes enlarged and tortuous, and this portion is termed the ampulla. A small
triangular area of the fundus of the bladder, between the ductus deferentes laterally
and the bottom of the rectovesical excavation of peritoneum above, is in contact
with the rectum.
DuctTili Aberrantes. — A long narrow tube, the ductulus aberrans inferior {vas aberrans of
Holler), is occasionally found connected with the lower part of the canal of the epididymis, or
with the commencement of the ductus deferens. Its length varies from 3.5 to 35 cm., and it
may become dilated toward its extremity; more commonly it retains the same diameter through-
out. Its structure is similar to that of the' ductus deferens. Occasionally it is found unconnected
with the epididymis. A second tube, the ductulus aberrans superior, occurs in the head of the
epididymis; it is connected with the rete testis.
Paradidymis (organ of Giraldes). — This term is applied to a small collection of convoluted
tubules, situated in front of the lower part of the cord above the head of the epididymis. These
tubes are lined with columnar ciliated epithelium, and probably represent the remains of a part
of the Wolffian body.
Structure. — The ductus deferens consists of three coats: (1) an external or areolar coat; (2) a
muscular coat which in the greater part of the tube consists of two layers of unstriped muscular
fiber: an outer, longitudinal in direction, and an inner, circular; but in addition to these, at the
commencement of the ductus, there is a third layer, consisting of longitudinal fibers, placed
internal to the circular stratum, between it and the mucous membrane; (3) an internal or mucous
coat, which is pale, and arranged in longitudinal folds. The mucous coat is lined by columnar
epithelium which is non-ciliated throughout the greater part of the tube; a variable portion of
the testicular end of the tube is lined by two strata of columnar cells and the cells of the
superficial layer are ciliated.
Fig. 1152. — Fundus of tlie bladder with the vesicula; seminalea.
The Vesiculae Seminales (Seminal Vesicales) (Fig. 1152).
The vesiculse seminales are two lobulated membranous pouches, placed between
the fundus of the bladder and the rectum, serving as reservoirs for the semen,
and secreting a fluid to be added to the secretion of the testes. Each sac is somewhat
pyramidal in form, the broad end being directed backward, upward and lateralward.
It is usually about 7.5 cm. long, but varies in size, not only in different individuals,
but also in the same individual on the two sides. The anterior surface is in contact
with the fundus of the bladder, extending from near the termination of the ureter
THE PENIS
1247
to the base of the prostate. The posterior surface rests upon the rectum, from which
it is separated by the rectovesical fascia. The upper extremities of the two vesicles
diverge from each other, and are in relation with the ductus deferentes and the
terminations of the ureters, and are partly covered by peritoneum. The lower
extremities are pointed, and converge toward the base of the prostate, where each
joins with the corresponding ductus deferens to form the ejaculatory duct. Along
the medial margin of each vesicle runs the ampulla of the ductus deferens.
Each vesicle consists of a single tube, coiled upon itself, and giving off several
irregular cecal diverticula; the separate coils, as w^ell as the diverticula, are connected
together by fibrous tissue. When uncoiled, the tube is about the diameter of a
quill, and varies in length from 10 to 15 cm.; it ends posteriorly in a cul-de-sac;
its anterior extremity becomes constricted into a narrow straight duct, which
joins with the corresponding ductus deferens to form the ejaculatory duct.
Structure. — The vesicute seminales are composed of three coats: an external or areolar coat;
a middle or muscular coat thinner than in the ductus deferens and arranged in two layers, an
outer longitudinal and inner circular; an internal or mucous coat, which is pale, of a whitish
brown color, and presents a delicate reticular structure. The epithelium is columnar, and in
the diverticula goblet cells are present, the secretion of which increases the bulk of the seminal
fluid.
Vessels and Nerves. — The arteries supplying the vesiculae seminales are derived from the
middle and inferior vesical and middle liemorrhoidal. The veins and lymphatics accompany
the arteries. The nerves are derived from the pelvic plexuses.
The Ejaculatory Ducts (Ductus Ejaculatorii) (Fig. 1153).
The ejaculatory ducts are two in number, one on either side of the middle line.
Each is formed by the union of the duct from the vesicula seminalis with the ductus
deferens, and is about 2 cm. long.
They commence at the base of
the prostate, and run forw^ard
and downward between its mid-
dle and lateral lobes, and along
the sides of the prostatic utricle,
to end by separate slit-like ori-
fices close to or just within the
margins of the utricle. The ducts
diminish in size, and also converge,
toward their terminations.
Structure.— The coats of the ejacula-
tory ducts are' extremely thin. They
are: an outer fibrous layer, which is
almost entirely lost after the entrance
of the ducts into the prostate; a layer
of muscular fibers consisting of a thin
outer circular, and an inner longitu-
dinal, layer; and mucous membrane.
Ejaculatory duct
ProMatic utricle
Urethral cresJ,
Prostatic urethra
Fig. 1153. — Vesiculae seminales and ampullae of ductus defer-
entes, seen from the front. The anterior walls of the left ampulla,
left seminal vesicle, and prostatic urethra have been cut away.
The Penis.
The penis is a pendulous organ suspended from the front and sides of the pubic
arch and containing the greater part of the urethra. In the flaccid condition it is
cylindrical in shape, but when erect assumes the form of a triangular prism with
rounded angles, one side of the prism forming the dorsum. It is composed of
three cylindrical masses of cavernous tissue bound together by fibrous tissue and
covered with skin. Two of the masses are lateral, and are known as the corpora
cavernosa penis; the third is median, and is termed the corpus cavernosum urethrae
(Figs. 1154, 1155).
1248
SPLANCHNOLOGY
The Corpora Cavernosa Penis form the greater part of the substance of the
penis. For their anterior three-fourths they lie in intimate apposition with one
another, but behind they diverge in the form of two tapering processes, known
as the crura, which are firmly connected to the rami of the pubic arch. Traced
from behind forward, each cms begins by a blunt-pointed process in front of the
tuberosity of the ischium. Just before it meets its fellow it presents a slight enlarge-
ment, named by Kobelt the bulb of the corpus cavernosum penis. Beyond this point
the cms undergoes a constriction and merges into the corpus cavernosum proper,
which retains a uniform diameter to its
anterior end. Each corpus cavernosum
penis ends abruptly in a rounded ex-
tremity some distance from the point of
the penis.
The corpora cavernosa penis are sur-
rounded by a strong fibrous envelope
consisting of superficial and deep fibers.
The superficial fibers are longitudinal in
direction, and form a single tube which
encloses both corpora; the deep fibers are
arranged circularly around each corpus,
and form by their junction in the median
plane the septum of the penis. This is
thick and complete behind, but is imper-
fect in front, where it consists of a series
of vertical bands arranged like the teeth
of a comb ; it is therefore named the sep-
tum pectiniforme.
The Corpus Cavernosum Urethras
(corpus spongiosum) contains the urethra.
Dorsal veins Dorsal artery and nerve
Intigurnent
Fibrous envelope
Corpora cavernosa penis
Fig. 1154. — The constituent cavernous cylinders of
the penis. The glana and anterior part of the corpus
cavernosum urethrae are detached from the corpora
cavernosa penis and turned to one side.
Septum pectiniforme
Urethra
Corpus cavernosum urethrce
Fig. 1155. — Transverse section of the penis.
Behind, it is expanded to form the urethral bulb, and lies in apposition with the
inferior fascia of the urogenital diaphragm, from which it receives a fibrous invest-
ment. The urethra enters the bulb nearer to the upper than to the lower surface.
On the latter there is a median sulcus, from which a thin fibrous septum projects
into the substance of the bulb and divides it imperfectly into two lateral lobes or
hemispheres.
The portion of the corpus cavernosum urethra? in front of the bulb lies in a
groove on the under surface of the conjoined corpora cavernosa penis. It is cylin-
drical in form and tapers slightly from behind forward. Its anterior end is expanded
in the form of an obtuse cone, flattened from above downward. This expansion,
termed the glans penis, is moulded on the rounded ends of the corpora cavernosa
THE PENIS
1249
penis, extending farther on their upper than on their lower surfaces. At the summit
of the glans is the sHt-like vertical external urethral orifice. The circumference
of the base of the glans forms a rounded projecting border, the corona glandis,
overhanging a deep retroglandular sulcus, behind which is the neck of the penis.
For descriptive purposes it is convenient to divide the penis into three regions:
the root, the body, and the extremity.
Prostatic portion
of urethra.
Ejacidatory duct. ^
SPHINCTER ANI
Prostatic plexus^
of veiris.
Fossa
"uavicularis.
Fig. 1156.
Prepuce.
-Vertical section of bladder, penis, and urethra.
The root {radix penis) of the penis is triradiate in form, consisting of the
diverging crura, one on either side, and the median urethral bulb. Each crus
is covered by the Ischiocavernosus, while the bulb is surrounded by the Bulbo-
cavernosus. The root of the penis lies in the perineum between the inferior fascia
of the urogenital diaphragm and the fascia of Colles. In addition to being attached
to the fascise and the pubic rami, it is bound to the front of the symphysis pubis
by the fundiform and suspensory ligaments. The fundiform ligament springs from
the front of the sheath of the Rectus abdominis and the linea alba; it splits into two
fasciculi which encircle the root of the penis. The upper fibers of the suspensory
ligament pass downward from the lower end of the linea alba, and the lower fibers
from the symphysis pubis; together they form a strong fibrous band, which extends
to the upper surface of the root, where it blends with the fascial sheath of the organ.
The body (corpus penis) extends from the root to the ends of the corpora caver-
nosa penis, and in it these corpora cavernosa are intimately bound to one another.
A shallow groove which marks their junction on the upper surface lodges the
deep dorsal vein of the penis, while a deeper and wider groove between them
on the under surface contains, the corpus cavernosum urethrw. The body is
ensheathed by fascia, which is continuous above with the fascia of Scarpa, and
below with the dartos tunic of the scrotum and the fascia of Colles.
79
1250
SPLANCHNOLOGY
The extremity is formed by the glans penis, the expanded anterior end of the
corpus cavernosum urethrse. It is separated from the body by the constricted
neck, which is overhung by the corona glandis.
The integument covering the penis is remarkable for its thinness, its dark color,
its looseness of connection with the deeper parts of the organ, and its absence of
adipose tissue. At the root of the penis it is continuous with that over the pubes,
scrotum, and perineum. At the neck it leaves the surface and becomes folded
upon itself to form the prepuce or foreskin. The internal layer of the prepuce is
directly continuous, along the line of the neck, with the integument over the glans.
Immediately behind the external urethral orifice it forms a small secondary redu-
plication, attached along the bottom of a depressed median raphe, which extends
from the meatus to the neck; this fold is termed the frenulum of the prepuce. The
integument covering the glans is continuous with the urethral mucous membrane
at the orifice; it is devoid of hairs, but projecting from its free surface are a number
of small, highly sensitive papillse. Scattered glands on the corona, neck, glans and
inner layer of the prepuce, the preputial glands, have been described. ^ They secrete
a sebaceous material of very peculiar odor, which probably contains casein, and
readily undergoes decomposition; when mixed with discarded epithelial cells it is
called smegma.
The prepuce covers a variable amount of the glans, and is separated from it
by a potential sac — the preputial sac — which presents two shallow fosste, one on
either side of the frenulum.
Structure of the Penis. — From the internal surface of the fibrous envelope of the corporn
cavernosa penis, as well as from the sides of the septum, numerous bands or cords are given off,
which cross the interior of these cor-
pora cavernosa in all directions, sub-
dividing them into a number of sepa-
rate compartments, and giving the
entire structure a spongy appearance
(Fig. 1157). These bands and cords
are called trabeculse, and consist of
white fibrous tissue^ elastic fibers, and
plain muscular fibers. In them are
contained numerous arteries and nerves.
The component fibers which form the
trabecute are larger and stronger
around the circumference than at the
centers of the corpora cavernosa; they
are also thicker behind than in front.
The interspaces (cavernous spaces), on
the contrary, are larger at the center
than at the circumference, their long
diameters being directed transversely.
They are filled with blood, and are
lined bj' a layer of flattened cells sim-
ilar to the endothelial lining of veins.
The fibrous envelope of the corpus
cavernosum urethrae is thinner, whiter
in color, and more elastic than that of
the corpora cavernosa penis. The trabec-
ulffe are more deUcate, nearly uniform in size, and the meshes between them smaller than in the
corpora cavernosa penis: their long diameters, for the most part, corresponding with that of
the penis. The external envelope or outer coat of the corpus cavernosum urethrae is formed
partly of unstriped muscular fibers, and a layer of the same tissue immediately surrounds the
canal of the urethra.
Vessels and Nerves. — The arteries bringing the blood to the cavernous spaces are the deep
arteries of the penis and branches from the dorsal arteries of the penis, which perforate the fibrous
capsule, along the upper surface, especially near the forepart of the organ. On entering the
-. rtt'
^^/at.
Fig. 1157. — Section of corpus cavernosum penis in a non-dis-
tended condition. (Cadiat.) a. Trabecule of connective tissue,
with many elastic fibers and bundles of plain muscular tissue,
some of which are cut across (c). b. Blood sinuses.
■ Stieda (Comptes-rendus du XII Congr6s International de M6decine, Moscow, 1897) asserts that glands are never
found on the corona glandis, and that what have hitherto been mistaken for glands are really large papills.
I
THE PROSTATE
1251
cavernous structure the arteries divide into branches, which are supported and enclosed by the
trabeculae. Some of these arteries end in a capillary net-work, the branches of which open directly
into the cavernous spaces; others assume a tendril-like appearance, and form convoluted and
somewhat dilated vessels, which were named by Miiller helicine arteries. They open into the
CAVERNOUS
BRANCH
DORSAL ARTERY
CORPUS CAVERNOSUM
NS PENIS
INTERNAL PUDIC >" ^^.
ARTERY "*<
Fig. 1158. — Diagram of the arteries of the penis. (Testut )
spaces, and from them are also given off small capillary branches to supply the trabecular struc-
ture. They are bound down in the spaces by fine fibrous processes, and are most abundant
in the back part of the corpora cavernosa (Fig. 1157).
The blood from the cavernous spaces is •
returned by a series of vessels, some of
which emerge in considerable numbers
from the base of the glans penis and
converge on the dorsum of the organ to
form the deep dorsal vein; others pass out
on the upper surface of the corpora caver-
nosa and join the same vein; some emerge
from the under surface of the corpora
cavernosa penis and receiving branches
from the corpus cavernosum urethra, wind
around the sides of the penis to end in the
deep dorsal vein; but th? greater number
pass out at the root of the penis and
join the prostatic plexus.
The lymphatic vessels of the penis are
described on page 713.
The nerves are derived from the puden-
dal nerve and the pelvic plexuses. On the
glans and bulb some filaments of the
cutaneous nerves have Pacinian bodies
connected with them, and, according to
Krause, many of them end in peculiar end-
bulbs (see page 1060).
The Prostate (Prostata; Prostate
Glandj. (Fig. 1160.) jj^. V|fr,^,„.^p"nciAL dorsal vc.m
XJi^^ I'/itf "^H^^^i^-EXTERNAL PUDIC VEIM
The prostate is a firm, partly
glandular and partly muscular body,
which is placed immediately below
the internal urethral orifice and
around the commencement of the
urethra. It is situated in the pelvic cavity, below the lower part of the symphysis
pubis, above the superior fascia of the urogenital diaphragm, and in front of
the rectum, through which it may be distinctly felt, especially when enlarged.
It is about the size of a chestnut and somewhat conical in shape, and presents for
examination a base, an apex, an anterior, a posterior, and two lateral surfaces.
OBTURATOR VEIN
Fig. 1159. — Veins of the penis. (Testut.)
1252
SPLANCHNOLOGY
The base {basis prostata;) is directed upward, and is applied to the inferior
surface of the bladder, The greater part of this surface is directly continuous
with the bladder wall; the urethra penetrates it nearer its anterior than its
posterior border.
The apex {apex prostata') is directed downward, and is in contact with the
superior fascia of the urogenital diaphragm.
VAS
DEFERENS
!%EMINAL
VESICLE
ISTHMUS
URETHRA
PROSTATE
Fia. 1160. — Prostate with seminal vesicles and seminal ducts, viewed from in front and above.
(Spalteholz.)
Surfaces. — The posterior surface {fades posterior) is flattened from side to side
and slightly convex from above downward ; it is separated from the rectum by its
sheath and some loose connective tissue, and is distant about 4 cm. from the anus.
Near its upper border there is a depression through which the two ejaculatory
ducts enter the prostate. This depression serves to divide the posterior surface
into a lower larger and an upper smaller part. The upper smaller part constitutes
the middle lobe of the prostate and intervenes between the ejaculatory ducts and
the urethra; it varies greatly in size, and in some cases is destitute of glandular tissue.
The lower larger portion sometimes presents a shallow median furrow, which
imperfectly separates it into a right and a left lateral lobe: these form the main
mass of the gland and are directly continuous with each other behind the urethra.
In front of the urethra they are connected by a band which is named the isthmus:
this consists of the same tissues as the capsule and is devoid of glandular substance.
The anterior surface {fades anterior) measures about 2.5 cm. from above downward
but is narrow and convex from side to side. It is placed about 2 cm. behind the
pubic symphysis, from which it is separated by a plexus of veins and a quantity
of loose fat. It is connected to the pubic bone on either side by the puboprostatic
ligaments. The urethra emerges from this surface a little above and in front of the
apex of the gland.
The lateral surfaces are prominent, and are covered by the anterior portions of
the Levatores ani, which are, however, separated from the gland by a plexus
of veins.
The prostate measures about 4 cm. transversely at the base, 2 cm. in its antero-
posterior diameter, and 3 cm. in its vertical diameter. Its weight is about 8 gm.
It is held in its position by the puboprostatic ligaments; by the superior fascia of
THE BULBOURETHRAL GLANDS 1253
the urogenital diaphragm, which invests the prostate and the commencement
of the membranous portion of the urethra; and by the anterior portions of the
Levatores ani, which pass backward from the pubis and embrace the sides of
the prostate. These portions of the Levatores ani, from the support they afford
to the prostate, are named the Levatores prostatse.
The prostate is perforated by the urethra and the ejaculatory ducts. The
urethra usually lies along the junction of its anterior with its middle third. The
ejaculatory ducts pass obliquely downward and forward through the posterior
part of the prostate, and open into the prostatic portion of the urethra.
Structure. — The prostate is immediately enveloped by a thin but firm fibrous capsule,
distinct from that derived from the fascia endopelvina, and separated from it by a plexus
of veins. This capsule is firmly adherent to the prostate and is structurally continuous with
the stroma of the gland, being composed of the same tissues, viz.: non-striped muscle and fibrous
tissue. The substance of the prostate is of a pale reddish-gray color, of great density, and not
easily torn. It consists of glandular substance and muscular tissue.
The muscular tissue according to Kolliker, constitutes the proper stroma of the prostate;
the connective tissue being very scanty, and simply forming between the muscular fibers, thin
trabeculiB, in which the vessels and nerves of the gland ramify. The muscular tissue is arranged
as follows: immediately beneath the fibrous capsule is a dense layer, which forms an investing
sheath for the gland; secondly, around the urethra, as it lies in the prostate, is another dense
layer of circular fibers, continuous above with the internal layer of the muscular coat of the
bladder, and blending below with the fibers surrounding the membranous portion of the urethra.
Between these two layers strong bands of muscular tis.sue, which decussate freely, form meshes
in which the glandular structure of the organ is imbedded. In that part of the gland which is
situated in front of the urethra the muscular tissue is especially dense, and there is here little or
no gland tissue; while in that part which is behind the urethra the muscular tissue presents a
wide-meshed structure, which is densest at the base of the gland — that is, near the bladder —
becoming looser and more sponge-like toward the apex of the organ.
The glandular substance is composed of numerous follicular pouches the lining of which fre-
quently shows papillary elevations. The follicles open into elongated canals, which join to form
from twelve to twenty small excretory ducts. They are connected together by areolar tissue,
supported by prolongations from the fibrous capsule and muscular stroma, and enclosed in a
delicate capillary plexus. The epithelium which lines the canals and the terminal vesicles is of
the columnar variety. The prostatic ducts open into the floor of the prostatic portion of the
urethra, and are lined by two layers of epithelium, the inner layer consisting of columnar and
the outer of small cubical cells. Small colloid masses, known as amyloid bodies are often found
in the gland tubes.
Vessels and Nerves. — The arteries supplying the prostate are derived from the internal
pudendal, inferior vesical, and middle hemorrhoidal. Its veins form a plexus around the sides
and base of the gland; they receive in front the dorsal vein of the penis, and end in the hypogastric
veins. The nerves are derived from the pelvic plexus.
The Bulbourethral Glands (Glandulse Bulbourethrales ; Cowper's Glands).
The bulbourethral glands are two small, rounded, and somewhat lobulated bodies,
of a yellow color, about the size of peas, placed behind and lateral to the membran-
ous portion of the urethra, between the two layers of the fascia of the urogenital
diaphragm. They lie close above the bulb, and are enclosed by the transverse fibers
of the Sphincter urethra^ membranacese. Their existence is said to be constant:
they gradually diminish in size as age advances.
The excretory duct of each gland, nearly 2.5 cm. long, passes obliquely forward
beneath the mucous membrane, and opens by a minute orifice on the floor of the
cavernous portion of the urethra about 2.5 cm. in front of the urogenital diaphragm.
Structure. — Each gland is made up of several lobules, held together by a fibrous investment.
Each lobule consists of a number of acini, lined by columnar epithelial cells, opening into one
duct, which joins with the ducts of other lobules outside the gland to form the single excretory
duct.
1254
SPLANCHNOLOGY
THE FEMALE GENITAL ORGANS (ORG ANA GENITALIA MULIEBRIA).
The female genital organs consist of an internal and an external group. The
internal organs are situated within the pelvis, and consist of the ovaries, the uterine
tubes, the uterus, and the vagina. The external organs are placed below the urogenital
diaphragm and below and in front of the pubic arch. They comprise the mons
pubis, the labia majora et minora pudendi, the clitoris, the bulbus vestibuli, and the
greater vestibular glands.
The Ovaries (Ovaria).
The ovaries are homologous with the testes in the male. They are two nodular
bodies, situated one on either side of the uterus in relation to the lateral wall of
the pelvis, and attached to the back of the broad ligament of the uterus, behind
and below the uterine tubes (Fig. 1161). The ovaries are of a grayish-pink color,
and present either a smooth or a puckered uneven surface. They are each about
4 cm. in length, 2 cm. in width, and about 8 mm. in thickness, and weigh from 2
Epodphoron
Ligament of ovary
Ostium
abdominale
Ovarian fimbria
Ovarian
vessels
Fig.
External uterine orifice
1161. — Uterus and right broad ligament, seen from behind. The broad ligament has been spread out and the
ovarj- drawn downward.
to 3.5 gm. Each ovary presents a lateral and a medial surface, an upper or tubal
and a lower or uterine extremity, and an anterior or mesovarion and a posterior
free border. It lies in a shallow depression, named the ovarian fossa, on the lateral
wall of the pelvis; this fossa is bounded above by the external iliac vessels, in front
by the obliterated umbilical artery, and behind by the ureter. The exact position
of the ovary has been the subject of considerable difference of opinion, and the
description here given applies to the ovary of the nulliparous woman. The ovary
becomes displaced during the first pregnancy, and probably never again returns
to its original position. In the erect posture the long axis of the ovary is vertical.
The hihal extremity is near the external iliac vein; to it are attached the ovarian
fimbria of the uterine tube and a fold of peritoneum, the suspensory ligament of
the ovary, which is directed upward over the iliac vessels and contains the ovarian
vessels. The vtcrine end is directed downward toward the pelvic floor, it is usually
narrower than the tubal, and is attached to the lateral angle of the uterus, immedi-
ately behind the uterine tube; by a rounded cord termed the ligament of the ovary,
which lies within the broad ligament and contains some non-striped muscular
THE OVARIES
1255
fibers. The lateral surface is in contact with the parietal peritoneum, which Hnes
the ovarian fossa; the medial surface is to a large extent covered l)y the fimbriated
extremity of the uterine tube. The mesovarian border is straight and is directed
toward the obliterated umbilical artery, and is attached to the back of the broad
ligament by a short fold named the mesovarium. Between the two layers of this
fold the bloodvessels and nerves pass to reach the hilum of the ovary. The free
border is convex, and is directed toward the ureter. The uterine tube arches over
the ovary, running upward in relation to its mesovarian border, then curving over
its tubal pole, and finally passing downward on its free border and medial surface.
Fig. 1162. — Adult ovary, epoophoron, and uterine tube. (From Farre, after Kobelt.) a, a. Epoophoron formed
from the upper part of the Wolffian body. h. Remains of the uppermost tubes sometimes forming hydatids, c. Middle
set of tubes, d. Some lower atrophied tubes, e. Atrophied remains of the Wolffian duct. /. The terminal bulb or
hydatid, h. The uterine tube. i. Hydatid attached to the extremity. /. The ovary.
Epoophoron (parovarium; organ of Rosenmuller) (Figs. 1161, 1162). —The
epoophoron lies in the mesosalpinx between the ovary and the uterine tube, and
consists of a few short tubules (ductuli transversi) which converge toward the ovary
while their opposite ends open into a
rudimentary duct, the ductus longitu-
dinalis epoophori {diict of Gartner) .
Paroophoron. — The paroophoron
consists of a few scattered rudimen-
tary tubules, best seen in the child,
situated in the broad ligament be-
tween the epoophoron and the uterus.
The ductuli transversi of the epo-
ophoron and the tubules of the paro-
ophoron are remnants of the tubules
of the Wolffian body or mesonephros ;
the ductus longitudinalis epoophori is a
persistent portion of the Wolffian duct.
In the fetus the ovaries are situ-
ated, like the testes, in the lumbar
region, near the kidneys, but they
graduallv descend into the pelvis (page
1211).
Fig. 1163. — Section of the ovary. (After Schron.) 1.
Outer covering. 1'. Attached border. 2. Central stroma.
3. Peripheral stroma. 4. Bloodvessels. 5. Vesicular follicles
in their earliest stage. 6, 7, 8. More advanced foUicles. 9.
An almost mature follicle. 9'. Follicle from which the ovum
has escaped. 10. Corpus luteum.
Structure (Fig. 1163). — The surface of the ovary is covered by a layer of columnar cells which
constitutes the germinal epithelium of Waldeyer. This epithelium gives to the ovary a dull
gray color as compared with the shining smoothness of the peritoneum; and the transition be-
tween the squamous epithelium of the peritoneum and the columnar cells which cover the
ovary is usually marked by a line around the anterior border of the ovary. The ovary consists
of a number of vesicular ovarian follicles imbedded in the meshes of a stroma or frame-work.
1256
SPLANCHNOLOGY
Fibro-vascular coat ■
Membrana gramdos •
~^
^i^
- z^<
The stroma is a peculiar soft tissue, abundantly supplied with bloodvessels, consisting for the
most part of spindle-shaped cells with a small amount of ordinary connective tissue. These
cells have been regarded by some anatomists as unstriped muscle cells, which, indeed, they
most resemble; by others as connective-tissue cells. On the surface of the organ this tissue >s
much condensed, and forms a layer (tunica albuginea) composed of short connective-tissue
fibers, with fusiform cells between them. The stroma of the ovary may contain interstitial cells
resembling those of the testis.
Vesicular Ovarian Follicles {Graafian follicles). — Upon making a section of an ovary, numerous
round transparent vesicles of various sizes are to be seen; thej' are the follicles, or ovisacs con-
taining the ova. Immediately beneath the superficial covering is a layer of stroma, in which are
a large number of minute vesicles, of uniform size, about 0.25 mm. in diameter. These are the
folhcles in their earhest condition, and the layer where they are found has been termed the
cortical layer. They are especially numerous in the ovary of the j'oung child. After puberty,
and during the whole of the child-bearing period, large and mature, or almost mature follicles
are also found in the cortical layer in small numbers, and also "corpora lutea," the remains of
follicles which have burst and are undergoing atrophy and absorption. Beneath this superficial
stratum, other large and more or less mature folhcles are found imbedded in the ovarian stroma.
These increase in size as they recede from the surface toward a highly vascular stroma in the
center of the organ, termed the medullary substance (zona rasculosa of Waldeyer). This stroma
forms the tissue of the hilum by which the ovary is attached, and through which the bloodvessels
enter: it does not contain anj^ follicles.
The larger follicles (Fig. 1164) consist of an external fibrovascular coat, connected with the
surrounding stroma of the ovary by a net-work of bloodvessels; and an internal coat, which con-
sists of several layers of nucleated
cells, called the membrana granulosa.
At one part of the mature follicle the
cells of the membrana granulosa are
collected into a mass which projects
into the cavity of the follicle. This
is termed the discus proligerus, and
in it the ovum is imbedded.^ The
follicle contains a transparent albumin-
ous fluid.
The development and maturation
of the folhcles and ova continue un-
interruptedly from puberty to the end
of the fruitful period of woman's life,
while their formation commences be-
fore birth. Before puberty the ovaries
are small and the follicles contained
in them are disposed in a compara-
tively thick layer in the cortical sub-
stance; here they present the appear-
ance of a large number of minute
closed vesicles, constituting the early
condition of the folhcles; many,
however, never attain full develop-
ment, but shrink and disappear. At puberty the ovaries enlarge and become more vascular,
the follicles are developed in greater abundance, and their ova are capable of fecundation.
Discharge of the Ovum. — The follicles, after attaining a certain stage of development, gradu-
ally approach the surface of the ovary and burst; the ovum and fluid contents of the follicle
are liberated on the exterior of the ovary, and carried into the uterine tube bj- currents set up
by the movements of the cilia covering the mucous membrane of the fimbria?.
Corpus Luteum. — After the discharge of the o^-um the lining of the folhcle is thrown into
folds, and vascular processes grow inward from the surrounding tissue. In this way the space
is filled up and the corpus luteum formed. It consists at first of a radial arrangement of 3-ellow
cells with bloodvessels and lymphatic spaces, and later it merges with the surrounding stroma.
Vessels and Nerves. — The arteries of the ovaries and uterine tubes are the ovarian from
the aorta. Each anastomoses freely in the mesosalpinx, with the uterine arterj-, giving some
branches to the uterine tube, and others which traverse the mesovarium and enter the hilum of
the ovary. The veins emerge from the hilum in the form of a plexus, the pampiniform plexus ;
the ovarian vein is formed from this plexus, and leaves the pelvis in companj' with the artery.
The nerves are derived from the hypogastric or pelvic plexus, and from the ovarian plexus, the
uterine tube receiving a branch from one of the uterine nerves.
Zona striata
Germinal vesicle
Discus proligerus
Fig. 1164. — Section of vesicular ovarian follicle of cat. X 50.
' For a description of the ovum, see page 38.
THE UTERINE TUBE
1257
The Uterine Tube (Tuba Uterina [Fallopii]; Fallopian Tube; Oviduct).
(Figs. 1101, 1105).
The uterine tubes convey the ova from the ovaries to the cavity of the uterus.
They are two in number, one on either side, situated in the upper margin of the
broad ligament, and extending from tlie superior angle of the uterus to the side of
the pelvis. Each tube is about 10 cm. long, and is described as consisting of three
portions: (1) tlie isthmus, or medial constricted third; (2) the ampulla, or inter-
mediate dilated portion, which curves over the ovary; and (3) the infundibulum
with its abdominal ostium, surrounded by fimbriae, one of which, the ovarian fimbria
/
Ureter
Sacrogenital fold
Ligament of ovary
Uterine tube
Bound ligament of uterus
Pararectal fossa
Fig. 1165. — Female pelvis and its contents, seen from above and in front.
is attached to the ovary. The uterine tube is directed lateralward as far as the
uterine pole of the ovary, and then ascends along the mesovarian border of the
ovary to the tubal pole, over which it arches; finally it turns downward and ends
in relation to the free border and medial surface of the ovary. The uterine opening
is minute, and will only admit a fine bristle; the abdominal opening is somewhat
larger. In connection with the fimbria? of the uterine tube, or with the broad liga-
ment close to them, there are frequently one or more small pedunculated vesicles.
These are termed the appendices vesiculosae {hydatids of Morgagni).
Structure. — The uterine tube consists of three coats: serous, muscular, and mucous. The
external or serous coat is peritoneal. The middle or muscular coat consists of an external longi-
tudinal and an internal circular layer of non-striped muscular fibers continuous with those of
the uterus. The internal or mucous coat is continuous with the mucous lining of the uterus, and,
at the abdominal ostium of the tube, with the peritoneum. It is thrown into longitudinal folds,
which in the ampulla are much more extensive than in the isthmus. The lining epithelium is
columnar and ciliated. This form of epithelium is also found on the inner surface of the fimbriae,
while on the outer or serous surfaces of these processes the epithelium gradually merges into
the endothelium of the peritoneum.
Fertilization of the ovum is believed (page 44) to occur in the tube, and the fertilized ovum
is then normally passed on into the ilterus; the ovum, however, may adhere to and undergo develop-
ment in the uterine tube, giving rise to the commonest variety of ectopic gestation. In such cases
the anonion and chorion are formed, but a true decidua is never present; and the gestation usually
1258
SPLANCHNOLOGY
ends by extrusion of the ovum through the abdominal ostium, although it is not uncommon for
the tube to rupture into the peritoneal cavity, this being accompanied by severe hemorrhage,
and needing surgical interference.
The Uterus (Womb) (Figs. 1161, 1165, 1166).
The uterus is a hollow, thick-walled, muscular organ situated deeply in the
pelvic cavity between the bladder and rectum. Into its upper part the uterine
tubes open, one on either side, while below, its cavity communicates with that of
POSTCniOR
FORNIX
ANTERIOR
FORNIX
CLITORIS
Fig. 1166. — Sagittal section of the lower part of a female trunk, right segment. SM. INT. Small intestine. (Testut.)
the Vagina. When the ova are discharged from the ovaries they are carried to the
uterine cavity through the uterine tubes. If an ovum be fertilized it imbeds itself
in the uterine wall and is normally retained in the uterus until prenatal develop-
ment is completed, the uterus undergoing changes in size and structure to accom-
modate itself to the needs of the growing embryo (see page 59). After parturition
the uterus returns almost to its former condition, but certain traces of its enlarge-
ment remains. It is necessary, therefore, to describe as the type-form the adult
virgin uterus, and then to consider the modifications which are effected as a result
of pregnancy.
THE UTERUS 1259
fn the virgin state the uterus is flattened antero-posteriorly and is pyriform
in shape, with the apex directed downward and backward. It Hes between the
bladder in front and the pelvic or sigmoid colon and rectum behind, and is com-
pletely within the pelvis, so that its base is below the level of the superior pelvic
aperture. Its upper part is suspended by the broad and the round ligaments,
while its lower portion is imbedded in the fibrous tissue of the pelvis.
The long axis of the uterus usually lies approximately in the axis of the superior
pelvic aperture, but as the organ is freely movable its position varies with the
state of distension of the bladder and rectum. Except when much displaced by a
fully distended bladder, it forms a forward angle with the vagina, since the axis
of the vagina corresponds to the axes of the cavity and inferior aperture of the
pelvis.
The uterus measures about 7.5 cm. in length, 5 cm. in breadth, at its upper
part, and nearly 2.5 cm. in thickness; it weighs from 30 to 40 gm. It is divisible
into two portions. On the surface, about midway between the apex and base,
is a slight constriction, known as the isthmus, and corresponding to this in the
interior is a narrowing of the uterine cavity, the internal orifice of the uterus. The
portion above the isthmus is termed the body, and that below, the cervix. The
part of the body which lies above a plane passing through the points of entrance
of the uterine tubes is known as the fundus.
Body (corpus uteri) . — The body gradually narrows from the fundus to the
isthmus.
The vesical or anterior surface (fades vesicalis) is flattened and covered by
peritoneum, which is reflected on to the bladder to form the vesicouterine
excavation. The surface lies in apposition with the bladder.
The intestinal or posterior surface (fades intestinalis) is convex transversely and
is covered by peritoneum, which is continued down on to the cervix and vagina.
It is in relation with the sigmoid colon, from which it is usually separated by some
coils of small intestine.
The fundus (fundus uteri) is convex in all directions, and covered by peritoneum
continuous with that on the vesical and intestinal surfaces. On it rest some coils
of small intestine, and occasionally the distended sigmoid colon.
The lateral margins (rnarg'o lateralis) are slightly convex. At the upper end of
each the uterine tube pierces the uterine wall. Below and in front of this point
the round ligament of the uterus is fixed, while behind it is the attachment of the
ligament of the ovary. These three structures lie within a fold of peritoneum
which is reflected from the margin of the uterus to the wall of the pelvis, and is
named the broad ligament.
Cervix (cervix, uteri; neck). — The cervix is the lower constricted segment of
the uterus. It is somewhat conical in shape, with its truncated apex directed
downward and backward, but is slightly wider in the middle than either above or
below. Owing to its relationships, it is less freely movable than the body, so that
the latter may bend on it. The long axis of the cervix is therefore seldom in the
same straight line as the long axis of the body. The long axis of the uterus as a
whole presents the form of a curved line with its concavity forward, or in extreme
cases may present an angular bend at the region of the isthmus.
The cervix projects through the anterior wall of the vagina, which divides it
into an upper, supravaginal portion, and a lower, vaginal portion.
The supravaginal portion (portio supravaginalis [cervids]) is separated in front
from the bladder by fibrous tissue (parametrium), which extends also on to its sides
and lateralward between the layers of the broad ligaments. The uterine arteries
reach the margins of the cervix in this fibrous tissue, while on either side the ureter
runs downward and forward in it at a distance of about 2 cm. from the cervix.
Posteriorly, the supravaginal cervix is covered by peritoneum, which is prolonged
1260
SPLANCHNOLOGY
Uterine
tube
below on to the posterior vaginal wall, when it is reflected on to the rectum,
forming the rectouterine excavation. It is in relation with the rectum, from
which it may be separated by coils of small intestine.
The vaginal portion (portio vaginalis [cervicis]) of the cervix projects free into the
anterior wall of the vagina between the anterior and posterior fornices. On its
rounded extremity is a small, depressed, somewhat circular aperture, the external
orifice of the uterus, through which the cavity of the cervix communicates with
that of the vagina. The external orifice is bounded by two lips, an anterior and a
posterior, of which the anterior is the shorter and thicker, although, on account
of the slope of the cervix, it projects lower than the posterior. Normally, both lips
are in contact with the posterior vaginal wall.
Interior of the Uterus (Fig. 1167). — The cavity of the uterus is small in
comparison with the size of the organ.
The Cavity of the Body {cavum uteri) is a mere slit, flattened antero-posteriorly.
It is triangular in shape, the base being formed by the internal surface of the
fundus between the orifices of the uterine
tubes, the apex by the internal orifice of the
uterus through which the cavity of the body
communicates with the canal of the cervix.
The Canal of the Cervix (canalis cervicis
nteri) is somewhat fusiform, flattened from
before backward, and broader at the middle
than at either extremity. It communicates
above through the internal orifice with the
cavitv of the bodv, and below through the
external orifice with the vaginal cavity. The
wall of the canal presents an anterior and a
posterior longitudinal ridge, from each of
which proceed a number of small oblique
columns, the palmate folds, giving the appear-
ance of branches from the stem of a tree;
to this arrangement the name arbor vitse
uterina is applied. The folds on the two
walls are not exactly opposed, but fit between one another so as to close the
cervical canal.
The total length of the uterine cavity from the external orifice to the fundus
is about 6.25 cm.
Ligaments. — The ligaments of the uterus are eight in number: one anterior;
one posterior; two lateral or broad; two uterosacral; and two round ligaments.
The anterior ligament consists of the vesicouterine fold of peritoneum, which
is reflected on to the bladder from the front of the uterus, at the junction of the
cervix and body.
The posterior ligament consists of the rectovaginal fold of peritoneum, which is
reflected from the back of the posterior fornix of the vagina on to the front of the
rectum. It forms the bottom of a deep pouch called the rectouterine excavation,
which is bounded in front by the posterior wall of the uterus, the supravaginal
cervix, and the posterior fornix of the vagina; behind, by the rectum; and laterally
by two crescentic folds of peritoneum which pass backward from the cervix uteri
on either side of the rectum to the posterior wall of the pelvis. These folds are
named the sacrogenital or rectouterine folds. They contain a considerable amount
of fibrous tissue and non-striped muscular fibers which are attached to the front
of the sacrum and constitute the uterosacral ligaments.
The two lateral or broad ligaments (ligamentum latum uteri) pass from the sides of
the uterus to the lateral walls of the pelvis. Together with the uterus they form
Fig. 1167.
Internal
orifice
External
orifice
-Posterior half of uterus and upper
part of vagina.
THE UTERUS
1261
a septum across the female pelvis, dividing that cavity into two portions. In the
anterior part is contained the bladder; in the posterior part the rectum, and in
certain conditions some coils of the small intestine and a part of the sigmoid colon.
Between the two layers of each broad ligament are contained: (1) the uterine
tube superiorly; (2) the round ligament of the uterus; (3) the ovary and its ligament ;
(4) the epoophoron and paroophoron; (5) connective tissue; (6) unstriped muscular
fibers; and (7) bloodvessels and nerves. The portion of the broad ligament which
stretches from the uterine tube to the level of the ovary is known by the name
of the mesosalpinx. Between the fimbriated extremity of the tube and the lower
attachment of the broad ligament is a concave rounded margin, called the infun-
dibulopelvic ligament.
The round ligaments {Ugameniinn teres uteri) are two flattened bands between
10 and 12 cm. in length, situated between the layers of the broad ligament in front
of and below the uterine tubes. Commencing on either side at the lateral angle
of the uterus, this ligament is directed forward, upward, and lateralward over the
external iliac vessels. It then passes through the abdominal inguinal ring and along
the inguinal canal to the labium majus, in which it becomes lost. The round
ligaments consists principally of muscular tissue, prolonged from the uterus; also
of some fibrous and areolar tissue, besides bloodvessels, lymphatics; and nerves,
enclosed in a duplicature of peritoneum, which, in the fetus, is prolonged in the
form of a tubular process for a short distance into the inguinal canal. This process
is called the canal of Nuck. It is generally obliterated in the adult, but sometimes
remains pervious even in advanced life. It is analogous to the saccus vaginalis,
v.'hich precedes the descent of the testis.
In addition to the ligaments just described, there is a band named the ligamentum trans-
versalis colli (Mackenrodt) on either side of the cervix uteri. It is attached to the side of the
cervix uteri and to the vault and lateral fornix of the vagina, and is continuous externally with
the fibrous tissue which surrounds the pelvic bloodvessels.
The form, size, and situation of the uterus vary at different periods of life and under different
circumstances.
Uterine tvbe.
Cavity of uterus
Sigmoid colon
Rectum,
Anal canal ^ \ ^
Round ligament of
litems
Bladder
Symphysis pubis
Urethra
Vagina
Fig. 1168. — Sagittal section through the pelvis of a newly boru female, child.
In the fetus the uterus is contained in the abdominal cavity, projecting beyond the superior
aperture of the pelvis (Fig. 1168). The cervix is considerably larger than the body.
At puberty the uterus is pyriform in shape, and weighs from 14 to 17 gm. It has descended
into the pelvis, the fundus being just below the level of the superior aperture of this cavity. The
palmate folds are distinct, and extend to the upper part of the cavity of the organ.
1262 SPLANCHNOLOGY
The position of the uterus in the adult is liable to considerable variation, depending chiefly
on the condition of the bladder and rectum. When the bladder is empty the entire uterus is
directed forward, and is at the same time bent on itself at the junction of the body and cervix,
so that the body lies upon the bladder. As the latter fills, the uterus gradually becomes more
and more erect, until with a fully distended bladder the fundus may be directed backward toward
the sacrum.
During menstruation the organ is enlarged, more vascular, and its surfaces rounder; the external
orifice is rounded, its labia swollen, and the lining membrane of the body thickened, softer, and
of a darker color. According to Sir J. Williams, at each recurrence of menstruation, a mole-
cular disintegration of the mucous membrane takes place, which leads to its complete removal,
only the bases of the glands imbedded in the muscle being left. At the cessation of menstru-
ation, a fresh mucous membrane is formed by a proliferation of the remaining structures.
During -pregnancy the uterus becomes enormously enlarged, and in the eighth month reaches
the epigastric region. The increase in size is partly due to growth of preexisting muscle, and
partly to development of new fibers.
After ■parturition the uterus nearly regains its usual size, weighing about 42 gm.; but its cavity
is larger than in the virgin state, its vessels are tortuous, and its muscular la5'ers are more defined;
the external orifice is more marked, and its edges present one or more fissiu-es.
In old age the uterus becomes atrophied, and paler and denser in texture; a more distinct
constriction separates the body and cervix. The internal orifice is frequently, and the external
orifice occasionall}', obliterated, while the lips almost entirely disappear.
Structure. — The uterus is composed of three coats: an external or serous, a middle or
muscular, and an internal or mucous.
The serous coat {tunica serosa) is derived from the peritoneum; it invests the fundus and
the whole of the intestinal surface of the uterus; but covers the vesical surface only as far as
the junction of the body and cervix. In the lower fourth of the intestinal surface the peritoneum,
though covering the uterus, is not closely connected with it, being separated from it by a layer
of loose cellular tissue and some large veins.
The muscular coat {tunica muscularis) forms the chief bulk of the substance of the uterus.
In the virgin it is dense, firm, of a grayish color, and cuts almost like cartilage. It is thick opposite
the middle of the body and fundus, and thin at the orifices of the uterine tubes. It consists of
bundles of unstriped muscular fibers, disposed in layers, intermixed with areolar tissue, blood-
vessels, lymphatic vessels, and nerves. The layers are three in number: external, middle, and
internal. The external and middle layers constitute the muscular coat proper, while the inner
layer is a greatly hypertrophied muscularis mucosa?. During pregnancy the muscular tissue
becomes more prominently developed, the fibers being greatly enlarged.
The external layer, placed beneath the peritoneum, is disposed as a thin plane on the vesical
and intestinal surfaces. It consists of fibers which pass transversely across the fundus, and,
converging at each lateral angle of the uterus, are continued on to the uterine tube, the round
ligament, and the ligament of the ovarj': some passing at each side into the broad ligament,
and others running backward from the cervix into the sacrouterine ligaments. The middle
layer of fibers presents no regularity in its arrangement, being disposed longitudinally, obliquely,
and transverseh'. It contains more bloodvessels than either of the other two layers. The internal
or deep layer consists of circular fibers arranged in the form of two hollow cones, the apices of
which surround the orifices of the uterine tubes, their bases intermingling with one another on
the middle of the body of the uterus. At the internal orifice these circular fibers form a distinct
sphincter.
The mucous membrane {tunica mucosa) (Fig. 11G9) is smooth, and closely adherent to the
subjacent tissue. It is continuous through the fimbriated extremity of the uterine tubes, with
the peritoneum; and, through the external uterine orifice, with the lining of the vagina.
In the body of the uterus the mucous membrane is smooth, soft, of a pale red color, lined by
columnar cihated epithelium, and presents, when viewed with a lens, the orifices of numerous
tubular foUicles, arranged perpendicularly to the surface. The structure of the corium differs
from that of ordinary mucous membranes, and consists of an embryonic nucleated and highly
cellular form of connective tissue in which run numerous large lymphatics. In it are the tube-
hke' uterine glands, lined by ciliated columnar epithelium. They are of small size in the unim-
pregnated uterus, but shortly after impregnation become enlarged and elongated, presenting
a contorted or waved appearance (see page 60).
In the cervix the mucous membrane is sharply differentiated from that of the uterine cavity.
It is thrown into numerous oblique ridges, which diverge from an anterior and posterior longi-
tudinal raph6. In the upper two-thirds of the canal, the mucous membrane is provided with
numerous deep glandular follicles, which secrete a clear viscid alkaUne mucus; and, in addition,
extending through the whole length of the canal is a variable number of little cysts, presumably
follicles which have become occluded and distended with retained secretion. They are called
the ovula Nabothi. The mucous membrane covering the lower half of the cervical canal presents
numerous papillae. The epithelium of the upper two-thirds is cylindrical and cihated, but below
THE UTERUS
1263
this it loses its cilia, and gradually changes to stratified squamous epithelium close to the external
orifice. On the vaginal surface of the cervix the epithelium is similar to that lining the vagina,
viz., stratified squamous.
• Ciliated epithelium
Glands
'^^^^>v'
Circular
m oscular
fibers
Gland Stroma
Fig. 1160. — Vertical section of mucoua membrane of human uterus. (Sobotta.)
Vessels and Nerves. — The arteries of the uterus are the uterine, from the hypogastric; and
the ovarian, from the abdominal aorta (Fig. 1170). They are remarkable for their tortuous
Branches to tube
Branches to fundus
Fig. 1170. — The arteries of the internal organs of generation of the female, seen from behind. (After Hyrtl.)
course in the substance of the organ, and for their frequent anastomoses. The termination of
the ovarian artery meets that of the uterine artery, and forms an anastomotic trunk from which
branches are given off to supply the uterus, their disposition being circular. The veins are of
1264 SPLANCHNOLOGY
large size, and correspond with the arteries. They end in the uterine plexuses. In the impreg-
nated uterus the arteries carry the blood to, and the veins convey it away from, the intervillous
space of the placenta (see page 63). The lymphatics are described on page 714. The nerves
are derived from the hypogastric and ovarian plexuses, and from the third and fourth sacral
nerves.
The Vagina (Fig. 1106).
The vagina extends from the vestibule to the uterus, and is situated behind the
bladder and in front of the rectum; it is directed upward and backward, its axis
forming with that of the uterus an angle of over 90°, opening forward. Its walls
are ordinarily in contact, and the usual shape of its lower part on transverse section
is that of an H, the transverse limb being slightly curved forward or backward,
while the lateral limbs are somewhat convex toward the median line; its middle
part has the appearance of a transverse slit. Its length is 6 to 7.5 cm. along its
anterior wall, and 9 cm. along its posterior wall. It is constricted at its commence-
ment, dilated in the middle, and narrowed near its uterine extremity ; it surrounds
the vaginal portion of the cervix uteri, a short distance from the external orifice
of the uterus, its attachment extending higher up on the posterior than on the
anterior wall of the uterus. To the recess behind the cervix the term posterior
fornix is applied, while the smaller recesses in front and at the sides are called the
anterior and lateral fornices.
Relations. — The anterior surface of the vagina is in relation with the fundus of the bladder,
and with the urethra. Its posterior surface is separated from the rectum by the rectouterine
excavation in its upper fourth, and by the rectovesical fascia in its middle two-fourths; the lower
fourth is separated from the anal canal by the perineal body. Its sides are enclosed between
the Levatores ani muscles. As the terminal portions of the ureters pass forward and medial-
ward to reach the fundus of the bladder, they run close to the lateral fornices of the vagina, and
as they enter the bladder are slightly in front of the anterior fornix.
Structure. — The vagina consists of an internal mucous lining and a muscular coat separated
by a layer of erectile tissue.
The mucous membrane {tunica mucosa) is continuous above with that lining the uterus. Its
inner surface presents two longitudinal ridges, one on its anterior and one on its posterior wall.
These ridges are called the columns of ^ the vagina and from them numerous transverse ridges
or ruga3 extend outward on either side. These rugai are divided by furrows of variable depth,
giving to the mucous membrane the appearance of being studded over with conical projections
or papillEe; they are most numerous near the orifice of the vagina, especially before parturition.
The epithelium covering the mucous membrane is of the stratified squamous variety. The sub-
mucous tissue is very loose, and contains numerous large veins which by their anastomoses form
a plexus, together with smooth muscular fibers derived from the muscular coat; it is regarded
by Gussenbauer as an erectile tissue. It contains a number of mucous crypts, but no true glands.
The muscular coat {tunica inuscularis) consists of two layers: an external longitudinal, which
is by far the stronger, and an internal circular layer. The longitudinal fibers are continuous
with the superficial muscular fibers of the uterus. The strongest fasciculi are those attached
to the rectovesical fascia on either side. The two layers are not distinctly separable from each
other, but are connected by oblique decussating fasciculi, which pass from the one layer to the
other. In addition to this, the vagina at its lower end is surrounded by a band of striped muscular
fibers, the Bulbocavemosus (see page 430).
External to the muscular coat is a layer of connective tissue, containing a large plexus of
bloodvessels.
The erectile tissue consists of a layer of loose connective tissue, situated between the mucous
membrane and the muscular coat; imbedded in it is a plexus of large veins, and numerous bundles
of unstriped muscular fibers, derived from the circular muscular layer. The arrangement of the
veins is similar to that found in other erectile tissues.
The External Genital Organs (Partes Genitales Externse Muliebres)
(Fig. 1171).
The external genital organs of the female are: the mons pubis, the labia majora
et minora pudendi, the clitoris, the vestibule of the vagina, the bulb of the vestibule,
and the greater vestibular glands. The term pudendum or vulva, as generally applied,
includes all these parts.
THE EXTERNAL GENITAL ORGANS
1265
The Mons Pubis {commissura labiorum anterior; mons Veneris), the rounded
eminence in front of the pubic symphysis, is formed by a collection of fatty tissue
beneath the integument. It becomes covered with hair at the time of puberty.
The Labia Majora {labia majora pudendi) are two prominent longitudinal cuta-
neous folds which extend downward and backward from the mons pubis and form
the lateral boundaries of a fissure or cleft, the pudendal cleft or rima, into which
the vagina and urethra open. Each labium has two surfaces, an outer, pigmented
and covered with strong, crisp hairs; and an inner, smooth and beset with large
sebaceous follicles. Between the two there is a considerable quantity of areolar
tissue, fat, and a tissue resembling the dartos tunic of the scrotum, besides vessels,
nerves, and glands. The labia are thicker in front, where they form by their
meeting the anterior labial commissure. Posteriorly they are not really joined, but
Clitoris
Vestibule
External urethral
orifice
Vaginal orifice
Uymen
Fig. 1171. — External genital organs of female. Tiie labia minora have been drawn apart.
appear to become lost in the neighboring integument, ending close to, and nearly
parallel with, each other. Together with the connecting skin between them,
they form the posterior labial commissure or posterior boundary of the pudendum.
The interval between the posterior commissure and the anus, from 2.5 to 3 cm.
in length, constitutes the perineum. The labia majora correspond to the scrotum
in the male.
The Labia Minora {labia minora pudendi; nymphce) are two small cutaneous
folds, situated between the labia majora, and extending from the clitoris obliquely
downward, lateralward, and backward for about 4 cm. on either side of the orifice
of the vagina, between which and the labia majora they end; in the virgin the pos-
terior ends of the labia minora are usually joined across the middle line by a fold
of skin, named the frenulum of the labia or fourchette. Anteriorly, each labium
80
1266 SPLANCHNOLOGY
minus divides into two portions: the upper division passes above the ditoris to
meet its fellow of the opposite side, forming a fold which overhangs the glans
clitoridis, and is named the preputium clitoridis; the lower division passes beneath
the clitoris and becomes united to its under surface, forming, with its fellow of the
opposite side, the frenulum of the clitoris. On the opposed surfaces of the labia
minora are numerous sebaceous follicles.
The Clitoris is an erectile structure, homologous with the penis. It is situated
beneath the anterior labial commissure, partially hidden between the anterior
ends of the. labia minora. It consists of two corpora cavernosa, composed of
erectile tissue enclosed in a dense layer of fibrous membrane, united together along
their medial surfaces by an incomplete fibrous pectiniform septum; each corpus
is connected to the rami of the pubis and ischium by a crus; the free extremity
(glans clitoridis) is a small rounded tubercle, consisting of spongy erectile tissue,
and highly sensitive. The clitoris is provided like the penis, with a suspensory
ligament, and with two small muscles, the Ischiocavernosi, which are inserted
into the crura of the clitoris.
The Vestibule {vestihulum vagincp). — The cleft between the labia minora and
behind the glans clitoridis is named the vestibule of the vagina: in it are seen the
urethral and vaginal orifices and the openings of the ducts of the greater vestibular
glands.
The external urethral orifice {orificium vrethrcp externum; nrinary meatus) is
placed about 2.5 cm. behind the glans clitoridis and immediately in front of that
of the vagina; it usually assumes the form of a short, sagittal cleft with slightly
raised margins.
The vaginal orifice is a median slit below and behind the opening of the urethra;
its size varies inversely with that of the hymen.
The hymen is a thin fold of mucous membrane situated at the orifice of the vagina ;
the inner edges of the fold are normally in contact with each other, and the
vaginal orifice appears as a cleft between them. The hymen varies much in shape.
When stretched, its commonest form is that of a ring, generally broadest posteriorly ;
sometimes it is represented by a semilunar fold, with its concave margin turned
toward the pubes. Occasionally it is cribriform, or its free margin forms a mem-
branous fringe. It may be entirely absent, or may form a complete septum across
the lower end of the vagina ; the latter condition is known as an imperforate hymen.
It may persist after copulation, so that its presence cannot be considered a sign of
virginity. When the hymen has been ruptured, small rounded elevations known
as the carunculae hymenales are found as its remains. Between the hymen and
the frenulum of the labia is a shallow depression, named the navicular fossa.
The Bulb of the Vestibule (bulbus vestibnli; vaginal bulb) is the homologue of
the bulb and adjoining part of the corpus cavernosum urethra^ of the male, and
consists of two elongated masses of erectile tissue, placed one on either side of the
vaginal orifice and united to each other in front by a narrow median band termed
the pars intermedia. Each lateral mass measures a little over 2.5 cm. in length.
Their posterior ends are expanded and are in contact with the greater vestibular
glands; their anterior ends are tapered and joined to one another by the pars
intermedia; their deep surfaces are in contact with the inferior fascia of the uro-
genital diaphragm; superficially they are covered by the Bulbocavernosus.
The Greater Vestibular Glands (glandulo' vestibularis major [Bartholini]; Bar-
tholin's glands) are the homologues of the bulbo-urethral glands in the male. They
consist of two small, roundish bodies of a reddish-yellow color, situated one on either
side of the vaginal orifice in contact with the posterior end of each lateral mass of
the .bulb of the vestibule. Each gland opens by means of a duct, about 2 cm. long,
immediatel}' lateral to the hymen, in the groove between it and the labium minus.
THE MAMM'^ 1267
The Mammae (Mammary Gland; Breasts).
The mammae secrete the milk, and are accessory glands of the generative system.
They exist in the male as well as in the female; but in the former only in the rudi-
mentary state, unless their growth is excited by peculiar circumstances. In the
female they are two large hemispherical eminences lying within the superficial
fascia and situated on the front and sides of the chest ; each extends from the second
rib above to the sixth rib below, and from the side of the sternum to near the mid-
axillary line. Their weight and dimensions differ at different periods of life, and
in different individuals. Before puberty they are of small size, but enlarge as the
generative organs become more completely developed. They increase during preg-
nancy and especially after delivery, and become atrophied in old age. The left
mamma is generally a little larger than the right. The deep surface of each is
nearly circular, flattened, or slightly concave, and has its long diameter directed
upward and lateralward toward the axilla; it is separated from the fascia covering
the Pectoralis major, Serratus anterior, and Obliquus externus abdominis by loose
connective tissue. The subcutaneous surface of the mamma is convex, and presents,
just below the center, a small conical prominence, the papilla.
The Mammary Papilla or Nipple (papilla viammcp) is a cylindrical or conical
eminence situated about the level of the fourth intercostal space. It is capable
of undergoing a sort of erection from mechanical excitement, a change mainly
due to the contraction of its muscular fibers. It is of a pink or brownish hue, its
surface wrinkled and provided with secondary papillse; and it is perforated by from
fifteen to twenty orifices, the apertures of the lactiferous ducts. The base of the
mammary papilla is surrounded by an areola. In the virgin the areola is of a delicate
rosy hue; about the second month after impregnation it enlarges and acquires a
darker tinge, and as pregnancy advances it may assume a dark brown or even black
color. This color diminishes as soon as lactation is over, but is never entirely
lost throughout life. These changes in the color of the areola are of importance
in forming a conclusion in a case of suspected first pregnancy. Near the base of
the papilla, and upon the surface of the areola, are numerous large sebaceous glands,
the areolar glands, which become much enlarged during lactation, and present
the appearance of small tubercles beneath the skin. These glands secrete a pecu-
liar fatty substance, w^hich serves as a protection to the integument of the papilla
during the act of sucking. The mammary papilla consists of numerous vessels,
intermixed with plain muscular fibers, which are principally arranged in a circular
manner around the base: some few fibers radiating from base to apex.
Development. — The mamma is developed partly from mesoderm and partly from
ectoderm — its bloodvessels and connective tissue being derived from the former, its
cellular elements from the latter. Its first rudiment is seen about the third month,
in the form of a number of small inward projections of the ectoderm, which invade
the mesoderm; from these, secondary tracts of cellular elements radiate and sub-
sequently give rise to the epithelium of the glandular follicles and ducts. The
development of the follicles, however, remains imperfect, except in the parous
female.
Structure (Figs. 1172, 1173). — The mamma consists of gland tissue; of fibrous tissue, con-
necting its lobes; and of fatty tissue in the intervals between the lobes. The gland tissue, when
freed from fibrous tissue and fat, is of a pale reddish color, firm in texture, flattened from before
backward and thicker in the center than at the circumference. The subcutaneous surface of
the mamma presents numerous irregular processes which project toward the skin and are joined
to it by bands of connective tissue. It consists of numerous lobes, and these are composed of
lobules, connected together by areolar tissue, bloodvessels, and ducts. The smallest lobules
consist of a cluster of rounded alveoli, which open into the smallest branches of the lactiferous
ducts; these ducts unite to form larger ducts, and these end in a single canal, corresponding with
one of the chief subdivisions of the gland. The number of excretory ducts varies from fifteen
1268
SPLANCHNOLOGY
to twenty; they are termed the tubuli lactiferi. They converge toward the areola, beneath
which they form dilatations or ampullae, which serve as reservoirs for the milk, and, at the base
Lobule un
ravelled
Lactiferoiis
tubule
Lobules
Ampulla
Loculi in connective
tissue
Fig. 1172. — Dissection of the lower half of the mamma during the period of lactation. (Luschka.)
Alveoli
Fat
Dvct
of the papillae, become contracted, and pursue a straight course to its summit, perforating it
by separate orifices considerably narrower than the ducts themselves. The ducts are composed
of areolar tissue containing longitudinal and transverse elastic fibers; muscular fibers are entirely
absent; they are lined by columnar epithe-
lium resting on a basement membrane.
The epithelium of the mamma differs ac-
cording to the state of activity of the
organ. In the gland of a woman who is
not pregnant or suckling, the alveoli are
very small and solid, being filled with a
mass of granular polyhedral cells. During
pregnancy the alveoli enlarge, and the cells
undergo rapid multiplication. At the com-
mencement of lactation, the cells in the
center of the alveolus undergo fatty degen-
eration, and are eliminated in the first milk,
as colostrum corpuscles. The peripheral
cells of the alveolus remain, and form a
single layer of granular, short columnar
cells, with spherical nuclei, lining the base-
ment membrane. The cells, during the
state of activity of the gland, are capable of forming, in their interior, oil globules, which are
then ejected into the lumen of the alveolus, and constitute the milk globules. When the acini
are distended by the accumulation of the secretion the lining epithelium becomes flattened.
The fibrous tissue invests the entire surface of the mamma, and sends down septa between
its lobes, connecting them together.
The fatty tissue covers the surface of the gland, and occupies the interval between its lobes.
It usually exists in considerable abundance, and determines the form and size of the gland. There
is no fat immediately beneath the areola and papilla.
Vessels and Nerves. — The arteries supplying the mammse are derived from the thoracic
branches of the axillary, the intercostals, and the internal mammary. The veins describe an
anastomotic circle around the base of the papilla, called by Haller the circulus venosus. From
this, large branches transmit the blood to the circumference of the gland, and end in the axillary
and internal mammary veins. The lymphatics are described on page 715. The nerves are
derived from the anterior and lateral cutaneous branches of the fourth, fifth, and sixth thoracic
nerves.
Fig. 1173. — Section of portion of mamma.
THE THYROID GLAND
1269
THE DUCTLESS GLANDS.
There are certain organs which are very siniihir to secreting glands, but differ
from them in one essential particular, viz., they do not possess any ducts by which
their secretion is discharged. These organs are known as ductless glands. They
are capable of internal secretion — that is to say, of forming, from materials brought
to them in the blood, substances which have a certain influence upon the nutritive
and other changes going on in the body. This secretion is carried into the blood
stream, either directly by the veins or indirectly through the medium of the
lymphatics.
These glands include the thyroid, the parathyroids and the thymus; the pituitary
body and the pineal body; the chromaphil and cortical systems to which belong the
suprarenals, the paraganglia and aortic glands, the glomus caroticum and perhaps
the glomus coccygeum. The spleen is usually included in this list and sometimes the
lymph and hemolymph nodes described with the lymphatic system. Other glands
as the liver, pancreas and sexual glands give off internal secretions, as do the
gastric and intestinal mucous membranes.
External carotid artery
Superior thyroid artery
— Superior thyroid vein
Middle thyroid vein
Fig. 1174.^The thyroid gland and its relations,
THE THYROID GLAND (GLANDULA THYREIODEA; THYROID BODY)
(Fig. 1174).
The thyroid gland is a highly vascular organ, situated at the front and sides of
the neck; it consists of right and left lobes connected across the middle line by a
narrow portion, the isthmus. Its weight is somewhat variable, but is usually about
30 grams. It is slightly' heavier in the female, in whom it becomes enlarged during
menstruation and pregnancy.
The lobes {lobuli gl. thyreoidece) are conical in shape, the apex of each being
directed upward and lateralward as far as the junction of the middle with the lower
1270
SPLANCHNOLOGY
third of the thyroid cartilage; the base looks downward, and is on a level with the
fifth or sixth tracheal ring. Each lobe is about 5 cm. long; its greatest width is
about 3 cm., and its thickness about 2 cm. The lateral or superficial surface is con-
vex, and covered by the skin, the superficial and deep fasciae, the Sternocleido-
mastoideus, the superior belly of the Omohyoideus, the Sternohyoideus and Sterno-
thyreoideus, and beneath the last muscle by the pretracheal layer of the deep
fascia, which forms a capsule for the gland. The deep or medial surface is moulded
over the underlying structures, viz., the thyroid and cricoid cartilages, the trachea,
the Constrictor pharyngis inferior and posterior part of the Cricothyreoideus,
the esophagus (particularly on the left side of the neck), the superior and inferior
thyroid arteries, and the recurrent nerves. The anterior border is thin, and inclines
obliquely, from above downward toward the middle line of the neck, while the
posterior border is thick and overlaps the common carotid artery, and, as a rule,
the parathyroids.
The isthmus {isthmus gJ. thyreoidea) connects together the lower thirds of the
lobes; it measures about 1.25 cm. in breadth, and the same in depth, and usually
covers the second and third rings of the trachea. Its situation and size present,
however, manv variations. In the middle line of the neck it is covered bv the skin
and fascia, and close to the middle line, on either side, by the Sternothyreoideus.
Across its upper border runs an anastomotic branch uniting the two superior
thyroid arteries; at its lower border are the inferior thyroid veins. Sometimes the
isthmus is altogether wanting.
A third lobe, of conical shape, called the pyramidal lobe, frequently arises from
the upper part of the isthmus, or from the adjacent portion of either lobe, but
most commonly the left, and ascends as far as the hyoid bone. It is occasionally
quite detached, or may be divided into two or more parts.
A fibrous or muscular band is sometimes found attached, above, to the body
of the hyoid bone, and below to the isthmus of the gland, or its pyramidal lobe.
When muscular, it is termed the Levator glandulae thyreoidese.
Small detached portions of thyroid
tissue are sometimes found in the vicin-
ity of the lateral lobes or above the
isthmus; they are called accessory thy-
roid glands {glandulw thyreoidew acces-
sor ice) .
Development. — The thyroid gland is
developed from a median diverticulum
(Fig. 1175), which appears about the
fourth week on the summit of the tuber-
culum impar, but later is found in the
furrow * immediately behind the tuber-
culum (Fig. 979). It grows downward
and backward as a tubular duct, which
bifurcates and subsequently subdivides
into a series of cellular cords, from
which the isthmus and lateral lobes of
the thyroid gland are developed. The
ultimo-branchial bodies from the fifth
pharyngeal pouches are enveloped by
the lateral lobes of the thyroid gland; they undergo atrophy and do not form true
thyroid tissue. The connection of the diverticulum with the pharynx is termed
the thyroglossal duct; its continuity is subsequently interrupted, and it undergoes
degeneration, its upper end being represented by the foramen cecum of the tongue,
and its lower by the pyramidal lobe of the thyroid gland.
Thyroid gland
Parathyroids
Thymus
Thymus
Ultimo-branchial body
Fio. 1175. — Scheme showing development of bran-
chial epithelial bodies. (Modified from Kohn.) /,
//, III, IV. Branchial pouches.
THE PARATHYROID GLANDS
1271
Structure. — The thyroid gland is invested by a thin capsule of connective tissue, which pro-
jects into its substance and imperfectly divides it into masses of irregular form and size. When
the organ is cut into, it is of a brownish-red color, and is seen to be made up of a number of
closed vesicles, containing a j'ellow glairy fluid, and separated from each other by intermediate
connective tissue (Fig. 1176).
Colloid material
Colloid in
lymphatic vessel
Cubical , ^.^^
epithelium ^.^>_: * \^
Fig. 117(5. — Section of thyroid gland of sheep. X 160.
The vesicles of the thyroid of the adult animal are generally closed spherical sacs; but in some
young animals, e. g., young dogs, the vesicles are more or less tubular and branched. This
appearance is supposed to be due to the mode of growth of the gland, and merely indicates that
an increase in the number of vesicles is taking place. Each vesicle is lined by a single layer of
cubical epithelium. There does not appear to be a basement membrane, so that the epithelial
cells are in direct contact with the connective-tissue reticulum which supports the acini. The
vesicles are of various sizes and shapes, and contain as a normal product a viscid, homogeneous,
semifluid, slightly yellowish, colloid material; red corpuscles are found in it in various stages
of disintegration and decolorization, the yellow tinge being probably due to the hemoglobin,
which is thus set free from the colored corpuscles. The colloid material contains an iodine com-
pound, iodothyrin, and is readily stained by eosin. According to Bensley^ the thyroid gland
prepares and secretes into the vascular channels a substance, formed under normal conditions in
the outer pole of the cell and excreted from it directly without pa.s.SLng by the indirect route
through the follicular cavity. In addition to this direct mode of secretion there is an indirect
mode which consists in the condensation of the secretion into the form of droplets, having high
content of solids, and the extension of these droplets into the follicular ca\'ity. These droplets
are formed in the same zone of the cell as that in which the primary or chrect secretion is formed.
This internal secretion of the thyroid is supposed to contain a specific hormone which acts as a
chemical stinmhis to other tissues, increasing their metabolism.
Vessels and Nerves. — The arteries supplying the thyroid gland are the superior and inferior
thyroids and sometimes an additional branch (thyroidea ima) from the innominate artery or the
arch of the aorta, which ascends upon the front of the trachea. The arteries are remarkable
for their large size and frequent anastomoses. The veins form a plexus on the surface of the
gland and on the front of the trachea; from this plexus the superior, middle, and inferior th>Toid
veins arise; the superior and middle end in the internal jugular, the inferior in the innominate
vein. The capillary bloodvessels form a dense plexus in the connective tissue around the vesicles,
between the epithelium of the vesicles and the endothelium of the lymphatics, which surround
a greater or smaller part of the circumference of the vesicle. The Ijonphatic vessels run in the
interlobular cormective tissue, not uncommonly surrounding the arteries which they accompany,
and communicate with a net-work in the capsule of the gland; they may contain colloid material.
They end in the thoracic and right lymphatic trunks. The nerves are derived from the middle
and inferior cervical ganglia of the sympathetic.
THE PARATHYROID GLANDS (Fig. 1177).
The parathyroid glands are small brownish-red bodies, situated as a rule between
the posterior borders of the lateral lobes of the thyroid gland and its capsule.
They differ from it in structure, being composed of masses of cells arranged in a
more or less columnar fashion with numerous intervening capillaries. They meas-
' .American Journal of Anatomy, 1916. xix.
1272
SPLANCHXOLOGY
ure on an average about 6 mm. in length, and from 3 to 4 mm. in breadth, and
usually present the appearance of flattened oval disks. They are divided, accord-
ing to their situation, into superior and inferior. The superior, usually two in number,
are the more constant in position, and are situated, one on either side, at the level
of the lower border of the cricoid cartilage, behind the junction of the pharynx
and esophagus. The inferior, also usually two in number, may be applied to the
lower edge of the lateral lobes, or placed at some little distance below the thyroid
gland, or found in relation to one of the inferior thyroid veins. ^
Common carotid
artery
Tiighl parathy-
roids
Inferior thyroid
artery
Remnant of laryn-
geal nerve
Fig. 1177. — Parathyroid glands. (Halsted and Evans.)
In man, they number four as a rule; fewer than four were found in less than 1
per cent, of over a thousand persons (Pepere-), but more than four in over 33 per
cent, of 122 bodies examined bv Civalleri. In addition, numerous minute islands
of parathyroid tissue may be found scattered in the connective tissue and fat of
the neck around the parathyroid glands proper, and quite distinct from them.
Development. — The parathyroid bodies are developed as outgrowths from the
third and fourth branchial pouches (Fig. 1175).
A pair of diverticula arise from the fifth branchial pouch and form what are
termed the iiltimo-branchial bodies (Fig. 1175): these fuse with the thyroid gland,
but probably contribute no true thyroid tissue.
1 Consult an article "Concerning the Parathyroid Glands." by D. A. Welsh, Journal of .\natomy and Physiology,
vol. xxxii.
2 Consult Le Ghiandole paratiroidee, by A. Pepere, Turin, 1906.
THE THYMUS GLAND
1273
Structure. — Microscopically the parathyroids consist of intercommunicating columns of
cells supported by connective tissue containing a rich supply of blood capillaries. Most of the
cells are clear, but some, larger in size, contain oxyphil granules. Vesicles containing colloid
have been described as occurring in the parathjToid, but the observation has not been confirmed.
No doubt the parathyroid glands produce an internal secretion essential to the well-being
of the human economy; but it is still a matter of dispute what symptoms of disease are pro-
duced by their removal and suppression of their secretion. Pepere believes that they show
signs of exceptional activity during pregnane^', and that parathyroid insufficiency is a main
factor in the production of tetany in infants and adults, of eclampsia, and of certain sorts of
fits. It is probable that the tetany following parathyroidectomy is due to the accumulation of
ammonium carhonato and Kendall has suggested that the function of the parathyroid is to con-
vert ammonium carbonate into urea.
THE THYMUS GLAND (Fig. 1178).
The thymus is a temporary organ, attaining its largest size at the time of
puberty (Hammar), when it ceases to grow, gradually dwindles, and almost
disappears. If examined when its growth is most active, it will be found to con-
sist of two lateral lobes placed in close contact along the middle line, situated
partly in the thorax, partly in the neck, .and extending from the fourth costal
cartilage upward, as high as the lower border of the thyroid gland. It is covered
by the sternum, and by the origins of the Sternohyoidei and Sternothyreoidei.
Trachea
Thyroid veitis
Hiffht vagtis
Superior vena cava
I
:lavian vessels
Fig. 117S. — Tlie thymus of a full-time fetus, exposed in situ.
Below, it rests upon the pericardium, being separated from the aortic arch and
great vessels by a layer of fascia. In the neck it lies on the front and sides of the
trachea, behind the Sternohyoidei and Sternothyreoidei. The two lobes generally
differ in size; they are occasionally united, so as to form a single mass; and some-
times separated by an intermediate lobe. The thymus is of a pinkish-gray color,
soft, and lobulated on its surfaces. It is about 5 cm. in length, 4 cm. in breadth
below, and about G mm. in thickness. At birth it weighs about 15 grams, at puberty
it weighs about 35 grams; after this it gradually decreases to 25 grams at twenty-
five years, less than 15 grams at sixty, and about 6 grams at seventy years.
Development. — The thymus appears in the form of two flask-shaped entodermal
diverticula, which arise, one on either side, from the third branchial pouch (Fig.
1175), and extend lateralward and backward into the surrounding mesoderm in
front of the ventral aortse. Here thev meet and become ioined to one another bv
*^ 0 «.
connective tissue, but there is never any fusion of the thymus tissue proper. The
pharyngeal opening of each diverticulum is soon obliterated, but the neck of the
flask persists for some time as a cellular cord. By further proliferation of the cells
lining the flask, buds of cells are formed, which become surrounded and isolated
by the invading mesoderm. In the latter, numerous lymphoid cells make their
1274
SPLANCHNOLOGY
appearance, and are aggregated to form lymphoid follicles. These lymphoid
cells are probably derivatives of the entodermal cells which lined the original
diverticula and their subdivisions. Additional portions of thymus tissue are
sometimes developed from the fourth branchial pouches. Thymus continues
to grow until the time of puberty and then begins to atrophy.
Arte
antdar
cells
Fig. 1179. — Minute structure of thymus. Follicle of injected thymus from calf, four days old, slightly diagram-
matic, magnified about 50 diameters. The large vessels are disposed in two rings, one of which surrounds the follicle,
the other lies just within the margin of the medulla. (Watney.) A and B. From thymus of camel, examined without
addition of any reagent. Magnified about 400 diameters. A. Large colorless cell, containing small oval masses of
hemoglobin. Similar cells are found in the lymph glands, spleen, and medulla of bone. B. Colored blood corpuscles.
Structure. — Each lateral lobe is composed of numerous lobules held together by deUcate
areolar tissue; the entire gland being enclosed in an investing capsule of a similar but denser
structure. The primary lobules vary in size from that of a pin's head to that of a small pea, and
are made up of a number of small nodules or follicles, which are irregular in shape and are more
or less fused together, especially toward the interior of the gland. Each foUicle is from 1 to 2 mm.
in diameter and consists of a medullary and a cortical portion, and these differ in many essential
particulars from each other. The cortical portion is mainly composed of lymphoid cells, supported
by a network of finely branched cells, which is continuous with a similar network in the medullary
portion. This network forms an adventitia to the bloodvessels. In the medullary portion the
reticulum is coarser than in the cortex, the lymphoid cells are relatively fewer in number, and
there are found peculiar nest-like bodies, the concentric corpuscles of Hassall. These concentric
corpuscles are composed of a central mass, consisting of one or more granular cells, and of a
capsule which is formed of epithehoid cells (Fig. 1179). They are the remains of the epithelial
tubes which grow out from the third branchial pouches of the embryo to form the thymus.
Each folhcle is surrounded by a vascular plexus, from which vessels pass into the interior,
and radiate from the periphery toward the center, forming a second zone just within the margin
of the medullary portion. In the center of the medullary portion there are very few vessels, and
they are of minute size.
Watney has made the important observation that hemoglobin is found in the thymus, either
in cysts or in cells situated near to, or forming part of, the concentric corpuscles. This hemo-
globin occurs as granules or as circular masses exactly resembling colored blood corpuscles. He
THE HYPOPHYSIS CEREBRI
1275
has also discovered, in the lymph issuing from the thymus, similar cells to those found in the
gland, and, like them, containing hemoglobin in the form of either granules or masses. From
these facts he arrives at the conclusion that the gland is one source of the colored blood corpuscles.
More recently Schaffer has observed actual nucleated red-l)lood corjjuscles in the thymus. The
function of the thymus is ol)scure. It seems to furnish during the period of growth an internal
secretion concerned with some phases of body metabolism, es})ecially that of the sexual glands.
Vessels and Nerves. — -The arteries supplying the thymus are derived from the internal
mammar}% and from the superior and inferior thj-roids. The veins end in the left innominate
vein, and in the thjToid veins. The lymphatics are described on page 69S. The nerves are
exceedingly minute; they are derived from the vagi and sympathetic. Branches from the descen-
dens hypoglossi and phrenic reach the investing capsule, but do not penetrate into the substance
of the gland.
THE HYPOPHYSIS CEREBRI.
The hypophysis (pifuifary body) (Fig. 1180) is a small reddish-gray body, about
1 cm. in diameter, attached to the end of the infundibulum of the brain and resting
in the hypophyseal fossa.
t^Zlis Anterior Optv:
commissure recess
Ant. cerebral artery/.
Optic chiasma.
Jnfu ndibulum
N .-Circular simis
Cerd)ral peduncle
Corpus mammiUare
Post, cerebral artery
Basilar artery
Pons
Anterior
of hypophysis r> . • j i
Posterior lobe
Fig. 1180. — The hypophysis cerebri in position. Shown in sagittal section.
Optic chiasma
Srd ventricle
Exteiuion of pars intermedia
into brain substance
Process of pars intermedia
Anterior lobe
Intraglandular cleft
Pars intermedia
Fig. 1181. — Median sagittal section through the hypophysis of an adult monkey.
Posterior lobe
Semidiagrammatic. (Herring.)
The hypophysis consists of an anterior and a posterior lobe, which differ from
one another in their mode of development and in their structure (Fig. 1181). The
anterior lobe is the larger and is somewhat kidney-shaped, the concavity being
directed backward and embracing the posterior lobe. It consists of a pars anterior
1276
SPLAXCHXOLOGY
am
p.r
and a pars intermedia, separated from each other by a narrow cleft, the remnant
of the pouch or diverticuhun. The pars anterior is extremely vascular and consists
of epithelial cells of varying size and shape, arranged in cord-like trabeculfe or
alveoli and separated by large, thin-walled blood\"essels. The pars intermedia is a
thin lamina closely applied to the body and neck of the posterior lobe and extend-
ing onto the neighboring parts of the brain; it contains few bloodvessels and
consists of finely granular cells between which are small masses of colloid material.
The pars intermedia in spite of the fact that it arises in common with the pars
anterior from the ectoderm of the primitive buccal cavity is often considered as
a part of the posterior lobe
which arises from the floor- of
the third ventricle of the
brain. Although of nervous
origin the posterior lobe con-
tains no nerve cells or fibers.
It consists of neuroglia cells
and fibers and is invaded by
columns which grow into it
from the pars intermedia;
imbedded in it are large
quantities of a colloid sub-
stance histologically similar
to that found in the thvToid
gland. In certain of the
lower vertebrates, e.g., fishes,
nervous structures are pres-
ent, and the lobe is of large
size.
From the pars intermedia
a substance, no doubt an in-
ternal secretion, causes con-
striction of the bloodvessels
with rise of arterial blood-
pressure. This substance
seems to have a stimulating
effect on most of the smooth
muscles, acting directly upon
the muscle causing contrac-
tion. It also increases the se-
cretion of the urine; of the
mammary glands when in
functional activity; and of
the cerebrospinal fluid. Ex-
tracts of tliis lobe also influ-
ence the general metabolism of the carbohydrates by accelerating the process of
glycogenolysis in the liver.
The pars anterior exercises a stimulating effect on the growth of the skeleton and
probably on connective tissues in general.
Enlargement of the hypophysis and of the cavity of the sella turcica are found in the rare
disease acromegaly, which is characterized by gradual enlargement of the face, hands, and feet,
with headache and often a pecuhar tj-pe of bhndness. This bhndness is due to the pressure of
the enlarging hypophysis on the optic chiasma (Fig. 1180).
Development of the Hypophysis Cerebri. — This in the adult consists of a large
anterior, consisting of the pars anterior and the pars intermedia, and a small pos-
FiG. 1 18J. — Vertical sections of the heads of early embryos of the rab-
bit. Magnified. (From Mihalkovics.) A. From an embryo 5 mm.
long. B. From an embryo 6 mm. long. C. Vertical section of the
anterior end of the notochord and hj^pophysis, etc., from an embrj-o 16
mm. long. In A the buccopharyngeal membrane is still present. In B
it is in the process of disappearing, and the stomodeum now communi-
cates with the primitive pharynx, am. Amnion, c. Fore-brain, ch.
Notochord. /. Anterior extremity of fore-gut, i. h. Heart, if. Infun-
dibulum. m. Wall of brain cavity, mc. Mid-brain. mo. Hind-brain.
p. Original position of hj-pophyseal diverticulum, py. ph. Pharynx.
sp.e. Sphenoethmoidal, be. Central, sp.o. Sphenooccipital parts of basis
cranii. tha. Thalamus.
THE CHROMAPHIL AND CORTICAL SYSTEMS 1277
terior lobe: the former is derived from the ectoderm of the stomodeum, the latter
from the floor of the fore-brain. About the fourth ^Yeek there ajDpears a pouch-
Hke diverticuhim of the ectodermal Hning of the roof of the stomodeum. This
diverticuhuu, pouch of Rathke (Fig. 1182), is the rudiment of the anterior lobe of
the hypophysis; it extends upward in front of the cephalic end of the notochord
and the remnant of the buccopharyngeal membrane, and comes into contact wuh
the under surface of the fore-brain. It is then constricted off to form a closed
vesicle, but remains for a time connected to the ectoderm of the stomodeum by a
solid cord of cells. Masses of epithelial cells form on either side and in the front
wall of the vesicle, and by the growth between these of a stroma from the mesoderm
the development of the anterior lobe is completed. The upwardly directed hypo-
physeal involution becomes applied to the antero-lateral aspect of a downwardly
directed diverticulum from the base of the fore-brain (page 744). This divertic-
ulum constitutes the future infundibulum in the floor of the third ventricle
while its inferior extremity becomes modified to form the posterior lobe of the
h\'pophysis. In some of the lower animals the posterior lobe contains nerve cells
and nerve fibers, but in man and the higher vertebrates these are replaced by
connective tissue. A canal, craniopharyngeal canal, is sometimes found extending
from the anterior part of the fossa hypophyseos of the sphenoid bone to the under
surface of the skull, and marks the original position of Rathke's pouch; while at
the junction of the septum of the nose with the palate traces of the stomodeal
end are occasionally present (Frazer).
THE PINEAL BODY.
The pineal body (epiphysis) is a small reddish-gray body, about 8 mm. in length
which lies in the depression between the superior colliculi. It is attached to the
roof of the third ventricle near its junction with the mid-brain. It develops as an
outgrowth from the third ventricle of the brain.
In early life it has a glandular structure which reaches its greatest development
at about the seventh year. Later, especially after puberty, the glandular tissue
gradually disappears and is replaced by connective tissue.
Structure. — -The pineal body is destitute of nervous substance, and consists of follicles lined
by epithelium and enveloped by connective tissue. These follicles contain a variable quantity
of gritt}^ material, composed of phosphate and carbonate of calcium, phosphate of magnesium
and ammonia, and a httle animal matter.
It contains a substance which if injected intravenously causes fall of blood-pressure. It seems
probable that the gland furnishes an internal secretion in children that inhibits the development
of the reproductive glands since the invasion of the gland in children, by pathological growths
which practically destroy the glandular tissue, results in accelerated development of the sexual
organs, increased growth of the skeleton and precocious mentality.
THE CHROMAPHIL AND CORTICAL SYSTEMS.
Chromaphil or chromaffin cells, so-cahed because they stain yellow or brownish with
chromium salts, are associated with the ganglia of the sympathetic nervous system.
Development. — They arise in common with the sympathetic cells from the neural
crest, and are therefore ectodermal in origin. The chromaphil and sympathetic
cells are indistinguishable from one another at the time of their migration from the
spinal ganglia to the regions occupied in the adult. Differentiation of chromaphil
cells begins in embryos about 18 mm. in length but is not complete until about
birth. The chromaphiloblasts increase in size more than the sympathoblasts and
stain less intensely with ordinary dyes. Later the chrome reaction develops. The
aortic bodies differentiate first and are prominent in 20 mm. embryos. The para-
ganglia of the sympathetic plexuses dift'erentiate next and last of all the para-
ganglia of the sympathetic trunk. The carotid body is completely differentiated
1278 SPLANCHNOLOGY
in 30 mm. embryos. After birth the chromaphil organs degenerate but the para-
ganglia can be recognized with the microscope in sites originally occupied by them.
The paraganglia are small groups of chromaphil cells connected with the ganglia
of the sympathetic trunk and the ganglia of the celiac, renal, suprarenal, aortic and
hypogastric plexuses. They are sometimes found in connection with the ganglia of
other sympathetic plexuses. None have been found with the s^Tupathetic ganglia
associated with the branches of the trigeminal nerve.
The aortic glands or bodies are the largest of these groups of chromaphil cells
and measure in the newborn about 1 cm. in length. They lie one on either side of
the aorta in the region of the inferior mesenteric artery. They decrease in size with
age and after puberty are only visible with the microscope. About forty they dis-
appear entirely. Other groups of chromaphil cells have been found associated with
the sympathetic plexuses of the abdomen independently of the ganglia.
The medullary portions of the suprarenal glands and the glomus caroticum
belong to the chromaphil system.
The Suprarenal Glands ( Glandulae Suprarenalis ; Adrenal Capsule)
(Figs. 1183, 1184).
The suprarenal glands are two small flattened bodies of a yellowish color, situated
at the back part of the abdomen, behind the peritoneum, and immediately above
and in front of the upper end of each kidney; hence their name. The right one is
somewhat triangular in shape, bearing a resemblance to a cocked hat; the left is
more semilunar, usually larger, and placed at a higher level than the right. They
vary in size in different individuals, being sometimes so small as to be scarcely
detected : their usual size is from 3 to 5 cm. in length, rather less in width, and from
4 to 6 mm. in thickness. Their average weight is from 1.5 to 2.5 gm. each.
Development. — Each suprarenal gland consists of a cortical portion derived
from the celomic epithelium and a medullary portion originally composed of
sympatho-chromaffin tissue. The cortical portion is first recognizable about the
beginning of the fourth week as a series of buds from the celomic cells at the root
of the mesentery. Later it becomes completely separated from the celomic
epithelium and forms a suprarenal ridge projecting into the celom between the
mesonephros and the root of the mesentery. Into this cortical portion cells from
the neighboring masses of sympatho-chromafEn tissue migrate along the line of
its central vein to reach and form the medullary portion of the gland.
Relations. — The relations of the suprarenal glands differ on the two sides of
the body.
The right suprarenal is situated behind the inferior vena cava and right lobe of the
liver, and in front of the diaphragm and upper end of the right kidney. It is roughly
triangular in shape; its base, directed downward, is in contact with the medial and
anterior aspects of the upper end of the right kidney. It presents two surfaces for
examination, an anterior and a posterior. The anterior surface looks forward and
lateralward, and has two areas: a medial, narrow, and non-peritoneal, which lies
behind the inferior vena cava; and a lateral, somewhat triangular, in contact with
the liver. The upper part of the latter surface is devoid of peritoneum, and is in
relation with the bare area of the liver near its lower and medial angle, while its
inferior portion is covered by peritoneum, reflected onto it from the inferior layer
of the coronary ligament; occasionally the duodenum overlaps the inferior portion.
A little below the apex, and near the anterior border of the gland, is a short furrow
termed the hilum, from which the suprarenal vein emerges to join the inferior vena
cava. The posterior surface is divided into upper and lower parts by a curved ridge :
the upper, slightly convex, rests upon the diaphragm; the lower, concave, is in
THE SUPRARENAL GLANDS
1279
contact with the upper end and ihv adjacent part of the anterior surface of the
kidney.
The left suprarenal, slightly larger than the right, is crescentic in shape, its con-
cavity being adapted to the medial border of the upper part of the left kidney.
It presents a medial border, which is convex, and a lateral, which is concave; its
upper end is narrow, and its lower rounded. Its anterior surface has two areas: an
Suprarenal vein
Hepatic area
Area in con-
tact with in-
ferior vena
cava
Gastric area
Pancreatic area
Suprarenal vein
Right. Left.
Fig. 11S3. — Suprarenal glands viewed from the front.
upper one, covered by the peritoneum of the omental bursa, which separates it
from the cardiac end of the stomach, and sometimes from the superior extremity
of the spleen; and a lower one, which is in contact with the pancreas and lienal
artery, and is therefore not co\ered by the peritoneum. On the anterior surface,
near its lower end, is a furrow or hilum, directed downward and forward, from which
the suprarenal vein emerges. Its posterior surface presents a vertical ridge, which
divides it into two areas; the lateral area rests on the kidney, the medial and smaller
on the left cms of the diaphragm.
Diaphrag-_
matic area
Benal area
Diaphragmatic
area
Renal area
Suprarenal
vein^
Right. Left.
Fig. 1184. — Suprarenal glands viewed from behind.
The surface of the suprarenal gland is surrounded by areolar tissue containing
much fat, and closely invested by a thin fibrous capsule, which is difhcult to remove
on account of the numerous fibrous ]irocesses and vessels entering the organ through
the furrows on its anterior surface and base.
Small accessory suprarenals {gJandidce suprarenales accessories;) are often to be
found in the connective tissue around the suprarenals. The smaller of these, on
section, show a uniform surface, but in some of the larger a distinct medulla can be
made out.
Structure. — On section, the suprarenal gland is seen to consist of two portions (Fig. llSo):
an external or cortical and an internal or medullary. The former constitutes the chief part of
the organ, and is of a deep yellow color; the medullary substance is soft, pulpy, and of a dark red
or brown color.
1280 SPLANCHNOLOGY
The cortical portion (suhstantia corllcalis) consists of a fine connective-tissue net-worlc, in
which is imbedded the glandular epithelium. The epithelial cells are polyhedral in shape and
possess rounded nuclei; many of the cells contain coarse granules, others lipoid globules. Owing
to differences in the arrangement of the cells, three distinct zones can be made out: (1) the zona
glomerulosa, situated beneath the capsule, consists of cells arranged in rounded groups, with
here and there indications of an alveolar structure; the cells of this zone are very granular, and
stain deeply. (2) The zona fasciculata, continuous with the zona glomerulosa, is composed of
columns of cells arranged in a radial manner; these cells contain finer granules and in many
instances globules of lipoid material. (3) The zona reticularis, in contact with the medulla,
consists of cylindrical masses of cells irregularly' arranged; these cells often contain pigment
granules which give this zone a darker appearance than the rest of the cortex.
The medullary portion (suhstantia medullaris) is extremely vascular, and consists of large
chromaphil cells arranged in a network. The irregular polyhedral cells have a finely granular
cystoplasm that are probably concerned with the secretion of adrenalin. In the meshes of the
cellular network are large anastomosing venous sinuses (sinusoids) which are in close relationship
with the chromaphil or medullary cells. In many places the endothelial lining of the blood sinuses
is in direct contact with the medullary cells. Some authors consider the endothelium absent in
places and here the medullary cells are directly bathed by the blood. This intimate relationship
between the chromaphil cells and the blood stream undoubtedly facilitates the discharge of the
internal secretion into the blood. There is a loose meshwork of supporting connective tissue con-
taining non-striped muscle fibers. This portion of the gland is richly supplied with non-medullated
nerve fibers, and here and there sympathetic ganglia are foimd.
"■:^r-.'- ^ ~ ^- I: -Ty^::^_i Capsule
'^' 'y,-'^:r'-}: - -'■''■'}'':!:^j:^) Zona glomerulosa
■'-,■■,';. ■■■■^3"
'asciculata
msm
J =■ ^%v' > Zona reticularis
^^ A^' Multinucleated viass
of protoplasm
Ganglion
Fig. 118.5. — Section of a part of a suprarenal gland. (Magnified.)
Vessels and Nerves. — The arteries supplying the suprarenal glands are numerous and of
comparatively large size; they are derived from the aorta, the inferior phrenic, and the renal.
They subdivide into minute branches previous to entering the cortical part of the gland, where
they break up into capillaries which end in the venous ple.xus of the medullary portion.
The suprarenal vein returns the blood from the medullary venous plexus and receives several
branches from the cortical substance; it emerges from the hiluin of the gland and on the right
side opens into the inferior vena cava, on the left into the renal vein.
The Ijrmphatics end in the lumbar glands.
The nerves are exceedingly numerous, and are derived from the celiac and renal plexuses,
and, according to Bergmann, from the phrenic and vagus nerves. They enter the lower and
medial part of the capsule, traverse the cortex, and end around the cells of the medulla. They
have numerous small ganglia developed upon them in the medullary portion of the gland.
In connection with the development of the medulla from the sj-mpathochromaffin tissue, it is
to be noted that this portion of the gland secretes a substance, adrenalin, which has a powerful
influence on those muscular tissues which are supplied by sympathetic fibers.
GLOMUS COCCYGEUM
1281
Glomus Caroticum (Carotid Glands; Carotid Bodies).
The carotid bodies, two in number, are situated one on either side of the neck,
behind the common carotid artery at its point of bifurcation into the external
and internal carotid trunks. They are reddish brown in color and oval in shape,
the long diameter measuring about 5 mm.
M&iMK^m^
:9o^:v
Fig. 1186. — Section of part of human glomus caroticum. (Schaper.) Highly magnified. Numerous bloodvessels are
seen in section among the gland cells.
Each is invested by a fibrous capsule and consists largely of spherical or irregular
masses of cells (Fig. 1186), the masses being more or less isolated from one another
by septa which extend inward from the deep surface of the capsule. The cells
are polyhedral in shape, and each contains a large nucleus imbedded in finely
granular protoplasm, which is stained yellow by chromic salts. Numerous nerve
fibers, derived from the sympathetic plexus on the carotid artery, are distributed
throughout the organ, and a net-work of large sinusoidal capillaries ramifies among
the cells..
Fig. 11S7. — Section of an irregular nodule of the glomus coccj'geum. (Sertoli.) X 85. The section shows the
fibrous covering of the nodule, the bloodvessels within it, and the epithelial cells of which it is constituted.
Glomus Coccygeum (Coccygeal Gland or Body; Luschka's Gland).
The glomus coccygeum is placed in front of, or immediately below, the tip of the
coccyx. It is about 2.5 mm. in diameter and is irregularly oval in shape; several
smaller nodules are found around or near the main mass.
It consists of irregular masses of round or polyhedral cells (Fig. 1187), the cells
81
1282
SPLANCHNOLOGY
of each mass being grouped around a dilated sinusoidal capillary vessel. Each cell
contains a large round or oval nucleus, the protoplasm surrounding which is clear,
and is not stained by chromic salts. ^
THE SPLEEN (LIEN).
The spleen is situated principally in the left hypochondriac region, but its supe-
rior extremity extends into the epigastric region; it lies between the fundus of the
stomach and the diaphragm. It is the largest of the ductless glands, and is of
an oblong, flattened form, soft, of very friable consistence, highly vascular, and
of a dark purplish color.
Development. — The spleen appears about the fifth week as a localized thickening
of the mesoderm in the dorsal mesogastrium above the tail of the pancreas. With
the change in position of the stomach the spleen is carried to the left, and comes
to lie behind the stomach and in contact with the left kidney. The part of the
dorsal mesogastrium which intervened between the spleen and the greater curva-
ture of the stomach forms the gastrosplenic ligament.
Relations. — The diaphragmatic surface {fades cUaphragmaiica; external or phrenic
surface) is convex, smooth, and is directed upward, backward, and to the left,
except at its upper end, where it is directed slightly medialward. It is in relation
with the under surface of the diaphragm, which separates it from the ninth, tenth,
and eleventh ribs of the left side, and the intervening lower border of the left lung
and pleura.
Vein
leaving
hilun
Fig. 1 188. — The \'isceral surface of the spleen.
The visceral surface (Fig. 1188) is divided by a ridge into an anterior or gastric
and a posterior or renal portion.
The gastric surface (fades gastrica) , which is directed forward, upward, and medial-
ward, is broad and concave, and is in contact with the posterior wall of the stomach;
' Consult the following article: " tfber die mensohliche Steissdruse," von J. W. Thomson Walker, Archiv fur mikro-
skopische Anatomie und Entwickelungsgeschichte, Band G4, 1904.
THE SPLEEN 1283
and below this with the tail of the pancreas. It presents near its medial border a
long fissure, termed the hilum. This is pierced by several irregular apertures, for
the entrance and exit of vessels and nerves.
The renal surface (fades renalis) is directed medialward and downward. It is
somewhat flattened, is considerably narrower than the gastric surface, and is in
relation with the upper part of the anterior surface of the left kidney and occasion-
ally with the left suprarenal gland.
The superior extremity iextrevnias snyerior) is directed toward the vertebral
column, where it lies on a level with the eleventh thoracic vertebra. The lower
extremity or colic surface (extremitas inferior) is flat, triangular in shape, and rests
upon the left flexure of the colon and the phrenicocolic ligament, and is generally
in contact with the tail of the pancreas. The anterior border imargo anterior) is free,
sharp, and thin, and is often notched, especially below; it separates the diaphragmatic
from the gastric surface. The posterior border (niargo posterior), more rounded and
blunter than the anterior, separates the renal from the diaphragmatic surface;
it corresponds to the lower border of the eleventh rib and lies between the diaphragm
and left kidney. The intermediate margin is the ridge which separates the renal
and gastric surfaces. The inferior border {internal border) separates the diaphrag-
matic from the colic surface.
The spleen is almost entirely surrounded by peritoneum, which is firmly adherent
to its capsule. It is held in position by two folds of this membrane. One, the
phrenicolienal ligament, is derived from the peritoneum, where the wall of the general
peritoneal ca\'ity comes into contact with the omental bursa between the left kidney
and the spleen; the lienal vessels pass between its two layers (Fig. 10.39). The other
fold, the gastrolienal ligament, is also formed of two layers, derived from the
general cavity and the omental respectively, where they meet between the spleen
and stomach (Fig. 1039); the short gastric and left gastroepiploic branches of the
lienal artery run between its two layers. The lower end of the spleen is supported
by the phrenicocolic ligament (see page 1155).
The size and weight of the spleen are liable to very extreme variations at different
periods of life, in different individuals, and in the same individual under different
conditions. In the adult it is usually about 12 cm. in length, 7 cm. in breadth, and
3 or 4 cm. in thickness, and weighs about 200 grams. At birth its weight, in pro-
portion to the entire body, is almost equal to what is observed in the adult, being
as 1 to 350; while in the adult it varies from 1 to 320 and 400. In old age the organ
not only diminishes in weight, but decreases considerably in proportion to the entire
body, being as 1 to 700. The size of the spleen is increased during and after diges-
tion, and ^■aries according to the state of nutrition of the body, being large in
highly fed, and small in starved animals. In malarial fever it becomes much
enlarged, weighing occasionally as much as 9 kilos.
Frequently in the neighborhood of the spleen, and especially in the gastrolienal
ligament and greater omentum, small nodules of splenic tissue may be found, either
isolated or connected to the spleen by thin bands of splenic tissue. They are known
as accessory spleens (lien accessorius ; supernumerary spleen). They vary in size
from that of a pea to that of a plum.
Structure. — ^The spleen is invested by two coats: an external serous and an internal fibre-
elastic coat.
The external or serous coat {tunica serosa) is derived from the peritoneum ; it is thin, smooth,
and in the human subject intimately adherent to the fibroelastic coat. It invests the entire
organ, except at the hilum and along the lines of reflection of the phrenicolienal and gastroUenal
ligaments.
The fibroelastic coat {tunica alhuginea) invests the organ, and at the hilum is reflected inward
upon the vessels in the form of sheaths. From these sheaths, as well as from the inner surface
of the fibroelastic coat, numerous small fibrous bands, trabeculse (Fig. 1189), are given off in all
directions; these uniting, constitute the frame-work of the spleen. The spleen therefore consists
1284
SPLANCHNOLOGY
of a number of small spaces or areolae, formed bj' the trabeculse; in these areolae is contained
the splenic pulp.
The fibroelastic coat, the sheaths of the vessels, and the trabeculae, are composed of white and
yellow elastic fibrous tissues, the latter predominating. It is owing to the presence of the elastic
tissue that the spleen possesses a considerable amount of elasticitj", which allows of the very
great variations in size that it presents under certain circumstances. In addition to these
Fia. 1189. — Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its tributaries.
constituents of this tunic, there is found in man a small amount of non-striped muscular fiber;
and in some mammalia, e. g., dog, pig, and cat, a large amount, so that the trabeculae appear
to consist chiefly of muscular tissue.
The splenic pulp (pulpa lienis) is a soft mass of a dark reddish-brown color, resembling grumous
blood; it consists of a fine reticulum of fibers, continuous with those of the trabeculae, to which
are applied flat, branching cells. The meshes of the reticulum are filled with blood, in which.
FiQ. 1190. — Transverse section of the luiman spleen, showing the distriL)ution of the splenic artery and its branches.
however, the white corpuscles are found to be in larger proportion than they are in ordinary
blood. Large rounded cells, termed splenic cells, are also seen; these are capable of ameboid
movement, and often contain pigment and red-blood corpuscles in their interior. The cells of
the reticulum each possess a round or oval nucleus, and hke the splenic cells, they may contain
pigment granules in their cytoplasm; they do not stain deeply with carmine, and in this respect
differ from the cells of the Malpighian bodies. In the young spleen, giant ceUs may also be found,
THE SPLEEN
1285
each containing numerous nuclei or one compound nucleus. Nucleated red-blood corpuscles
have also been found in the spleen of young animals.
Bloodvessels of the Spleen. — The lienal artery is remarkable for its large size in proportion
to the size of the organ, and also for its tortuous course. It divides into six or more branches,
which enter the hilurn of the spleen and ramify throughout its substance (Fig. 1190), receiving
sheaths from an involution of the external fibrous tissue. Similar sheaths also invest the nerves
and veins.
Each branch runs in the transverse axis of the organ, from within outward, diminishing in
size during its transit, and giving off in its passage smaller branches, some of which pass to the
anterior, others to the posterior part. These ultimately leave the trabecular sheaths, and ter-
minate in the proper substance of the spleen in small tufts or pencils of minute arterioles, which
open into the interstices of the reticulum formed by the branched sustentacular cells. Each of
the larger branches of the artery supplies chiefly that region of the organ in which the branch
ramifies, having no anastomosis with the majority of the other branches.
The arterioles, supported by the minute trabeculaj, traverse the pulp in all directions in bundles
{pencilli) of straight vessels. Their trabecular sheaths gradually undergo a transformation,
become much thickened, and converted into adenoid tissue; the bundles of connective tissue
becoming looser and their fibrils more delicate, and containing in their interstices an abundance
of lymph corpuscles (W. Mtiller).
Trahecvla
Lymphatic
nodule
Spleen pulp
Fig. 1191. — Transverse section of a portion of the spleen.
The altered coat of the arterioles, consisting of adenoid tissue, presents here and there thick-
enings of a spheroidal shape, the lymphatic nodules {Malpighian bodies of the spleen). These
bodies vary in size from about 0.25 mm. to 1 mm. in diameter. They are merely local expansions
or hyperplasiae of the adenoid tissue, of which the external coat of the smaller arteries of the spleen
is formed. They are most frequently found surrounding the arteriole, which thus seems to
tunnel them, but occasionally they grow from one side of the vessel only, and present the appear-
ance of a sessile bud growing from the arterial w'all. In transverse sections, the artery, in the
majority of cases, is found in an eccentric position. These bodies are visible to the naked eye
on the surface of a fresh section of the organ, appearing as minute dots of a semiopaque whitish
color in the dark substance of the pulp. In minute structure they resemble the adenoid tissue
of lymph glands, consisting of a delicate reticulum, in the meshes of which lie ordinary lymphoid
cells (Fig. 1191). The reticulum is made up of extremely fine fibrils, and is comparatively open
in the center of the corpuscle, becoming closer at its periphery. The cells which it encloses
are possessed of ameboid movement. When treated with carmine they become deeply stained,
and can be easily distinguished from those of the pulp.
The arterioles end by opening freely into the splenic pulp; their walls become much attenuated,
they lose their tubular character, and the endothelial ceUs become altered, presenting a branched
appearance, and acquiring processes which are directly connected with the processes of the
reticular cells of the pulp (Fig. 1192). In this manner the vessels end, and the blood flowing
through them finds its way into the interstices of the reticulated tissue of the splenic pulp. Thus
1286
SPLANCHNOLOGY
the blood passing through the spleen is brought into intimate relation with the elements of the
pulp, and no doubt undergoes important changes.
After these changes have taken place the blood is collected from the interstices of the tissue
by the rootlets of the veins, which begin much in the same way as the arteries end. The con-
nective-tissue corpuscles of the pulp arrange themselves in rows, in such a way as to form an
elongated space or sinus. They become elongated and spindle-shaped, and overlap each other
at their extremities, and thus form a sort of endothelial lining of the path or sinus, which is the
radicle of a vein. On the outer surfaces of these cells are seen delicate transverse lines or markings,
which are due to minute elastic fibrillae arranged in a circular manner around the sinus. Thus
the channel obtains an external investment, and gradually becomes converted into a small
Branching cell
Small .
artery
Vessel continuous
with 'processes of
network cells
Branching cell
FiQ. 1192. — Section of the spleen, showing the termination of the small bloodvessels.
vein, which after a short course acquires a coat of ordinary connective tissue, lined by a layer of
flattened epithelial cells which are continuous with the supporting cells of the pulp. The smaller
veins unite to form larger ones; these do not accompany the arteries, but soon enter the tra-
becular sheaths of the capsule, and by their junction form six or more branches, which emerge
from the hilum, and, uniting, constitute the lienal vein, the largest radicle of the portal vein.
The veins are remarkable for their numerous anastomoses, while the arteries hardly anastomose
at all.
The lymphatics are described on page 711.
The nerves are derived from the celiac plexus and are chiefly non-medullated. They are
distributed to the bloodvessels and to the smooth muscle of the capsule and trabeculae.
SURFACE ANATOMY AND SURFACE
MARKINGS.
SURFACE ANATOMY OF THE HEAD AND NECK.
Bones (Fig. 1193). — Various bony surfaces and prominences on the skull can be
easily identified by palpation. The external occipital protuberance is situated
behind, in the middle line, at the junction of the skin of the neck with that of the
head. The superior nuchal line runs lateralward from it on either side, while extend-
ing downward from it is the median nuchal crest, situated deeply at the bottom
of the nuchal furrow. Above the superior nuchal lines the vault of the cranium
Zygomatic tubercle v^
Zygomaticofrontal
suture
Supraorbital foramen
Glabella- -
Nasion.
Inion
Reid's base
line
Median nuchal crest
t Auricular point
Pre-auricular point
Fia. 1193. — Side view of head, showing surface relations of bones.
is thinly covered with soft structures, so that the form of this part of the head is
almost that of the upper portion of the occipital, the parietal, and the frontal
bones. The superior nuchal line can be followed lateralward to the mastoid por-
tion of the temporal bone, from which the mastoid process projects downward
and forward behind the ear. The anterior and posterior borders, the apex, and
the external surface of this process are all available for superficial examination. The
anterior border lies immediately behind the concha, and the apex is on a level
( 1287 )
1288 SURFACE ANATOMY AND SURFACE MARKINGS
with the lobule of the auricula. About 1 cm. below and in front of the apex of
the mastoid process, the transverse process of the atlas can be distinguished. In
front of the ear the zygomatic arch can be felt throughout its entire length; its
posterior end is narrow and is situated a little above the level of the tragus; its
anterior end is broad and is continued into the zygomatic bone. The lower border
of the arch is more distinct than the upper, which is obscured by the attachment
of the temporal fascia. In front, and behind, the upper border of the arch can be
followed into the superior temporal line. In front, this line begins at the zygomatic
process of the frontal bone as a curved ridge which runs at first forward and
upward on the frontal bone, and then curving backward separates the forehead
from the temporal fossa. It can then be traced across the parietal bone, where,
though less marked, it can generally be recognized. Finally, it curves downward,
and forward, and passing above the external acoustic meatus, ends in the posterior
root of the zygomatic arch. Near the line of the greatest transverse diameter of
the head are the parietal eminences, one on either side of the middle line; further
forward, on the forehead, are the frontal eminences, which vary in prominence in
different individuals and are frequently unsymmetrical. Below the frontal emi-
nences the superciliary arches, which indicate the position of the frontal sinuses,
can be recognized; as a rule they are small in the female and absent in children.
, In some cases the prominence of the superciliary arches is related to the size of
the frontal sinuses, but frequently there is no such relationship. Situated betw-een,
and connecting the superciliary ridges, is a smooth, somewhat triangular area, the
glabella, below wdiich the nasion (frontonasal suture) can be felt as a slight depres-
sion at the root of the nose.
Below the nasion the nasal bones, scantily covered by soft tissues, can be traced
to their junction with the nasal cartilages, and on either side of the nasal bone
the complete outline of the orbital margin can be made out. At the junction of
the medial and intermediate thirds of the supraorbital margin the supraorbital
notch, when present, can be felt; close to the medial end of the infraorbital margin
is a little tubercle which serves as a guide to the position of the lacrimal sac. Below
and lateral to the orbit, on either side, is the zygomatic bone forming the prominence
of the cheek; its posterior margin is easily palpable, and on it just above the level
of the lateral palpebral commissure is the zygomatic tubercle. A slight depression,
about 1 cm. abo\'e this tubercle, indicates the position of the zygomaticofrontal
suture. Directly below the orbit a considerable part of the anterior surface of the
maxilla and the Avhole of its alveolar process can be palpated. The outline of the
mandible can be recognized throughout practically its entire extent; in front of
the tragus and below the zygomatic arch is the condyle, and from this the posterior
border of the ramus can be followed to the angle; from the angle to the symphysis
the lower rounded border of the mandible can be easily traced ; the lower part of
the anterior border of the ramus and the alveolar process can be made out without
difficulty. In the receding angle below the chin is the hyoid bone, and the finger
can be carried along the bone to the tip of the greater cornu, which is on a level
with the angle of the mandible: the greater cornu is most readily appreciated
by making pressure on one side, w^hen the cornu of the opposite side wall be rendered
prominent and can be felt distinctly beneath the skin.
Joints and Muscles. — The temporomandibular articulation is quite superficial, and
is situated below the posterior end of the zygomatic arch, in front of the external
acoustic meatus. Its position can be ascertained b}- defining the condyle of the
mandible; when the mouth opens, the condyle advances out of the mandibular
fossa on to the articular tubercle, and a depression is felt in the situation of the
joint.
The outlines of the muscles of the head and face cannot be traced on the surface
except in the case of the Masseter and Teir^poralis. The muscles of the scalp
SURFACE ANATOMY OF THE HEAD AND NECK
1289
are so thin that the outhne of the bone is perceptible beneath them. Those of
the face are small, covered by soft skin, and often by a considerable layer of fat,
and their outlines are therefore concealed; they serve, however, to round off and
smooth prominent borders, and to fill up what would otherwise be unsightly
angular depressions. Thus the Orbicularis oculi rounds off the prominent margin
of the orbit, and the Procerus fills in the sharp depression below the glabella. In
like manner the labial muscles converging to the lips, and assisted by the super-
imposed fat, fill up the sunken hollow of the lower part of the face. When in
action the facial muscles produce the various expressions, and in addition throw
the skin into numerous folds and wrinkles. The Masseter imparts fulness to the
hinder part of the cheek; if firmly contracted, as when the teeth are clenched, its
quadrilateral outline is plainly visible; the anterior border forms a prominent
vertical ridge, behind which is a considerable fulness especially marked at the
Svhmaxillary triangl
Hyoid bone
Thyroid cartilage
Cricoid cartilage
/
T Sternocleidomastoideus
Trapezius
Supraclavicular fossa
Jugular notch Sternal head
Fio. 1194. — Anterolateral view of head and neck.
Infraclavicular fossa
Clavicular head ) j. c. 7 -j ^ j
oj Sternocletdomastotdeud
lower part of the muscle. The Temporalis is fan-shaped and fills the temporal
fossa, substituting for the concavity a somewhat convex swelling, the anterior
part of which, on account of the absence of hair on the overlying skin, is more
marked than the posterior, and stands out in strong relief when the muscle is in
action.
In the neck, the Platysma when contracted throws the skin into oblique ridges
parallel with the fasciculi of the muscle. The Sternocleidomastoideus has the most
important influence on the surface form of the neck (Figs. 1194, 1195). When the
muscle is at rest its anterior border forms an oblique rounded edge ending below in
the sharp outline of the sternal head; the posterior border is only distinct for about
2 or 3 cm. above the middle of the clavicle. During contraction, the sternal head
stands out as a sharply defined ridge, while the clavicular head is flatter and less
prominent ; between the two heads is a slight depression : the fleshy middle portion
1290
SURFACE ANATOMY AND SURFACE MARKINGS
of the muscle appears as an oblique elevation with a thick, rounded, anterior border,
best marked in its lower part. The sternal heads of the two muscles are separated
by a V-shaped depression, in which are the Sternohyoideus and Sternothyreoideus.
Above the hyoid bone, near the middle line, the anterior belly of the Digastricus
produces a slight convexity.
The anterior border of the Trapezius presents as a faint ridge running from the
superior nuchal line, downward and forward to the junction of the intermediate
and lateral thirds of the clavicle. Between the Sternocleidomastoideus and the
Trapezius is the posterior triangle of the neck, the lower part of which appears as
a shallow concavity — the supraclavicular fossa. In this fossa, the inferior belly of
the Omohyoideus, when in action, presents as a rounded cord-like elevation a little
above, and almost parallel to, the clavicle.
^j^.
Anterior belly of Digastricus
Mylohyoideus
Hyoid hone
Thyroid cartilage
Cricoid cartilage
Sternocleidomastoideus
Supracla vkular fossa
' Trapezius
JS"
' Clavicle
Clavicular head } of Sternocleido-
Sternal head ^ itmstoideus
Fig. 1195. — Front view of neck.
Arteries. — The positions of several of the larger arteries can be ascertained
from their pulsations.
The subclavian artery can be felt by making pressure downward, backward, and
medialward behind the clavicular head of the Sternocleidomastoideus; its transverse
cervical branch may be detected parallel to, and about a finger's breadth above,
the clavicle. The common and external carotid arteries can be recognized immediately
beneath the anterior edge of the Sternocleidomastoideus. The external maxillary
artery can be traced over the border of the mandible just in front of the anterior
border of the Masseter, then about 1 cm. lateral to the angle of the mouth, and
finally as it runs up the side of the nose. The pulsation of the occipital artery
can be distinguished about 3 or 4 cm. lateral to the external occipital protuberance;
that of the posterior auricular in the groo^-e between the mastoid process and the
auricula. The course of the superficial temporal artery can be readily followed
across the posterior end of the zygomatic arch to a point about 3 to 5 cm. above
this, where it divides into its frontal and parietal branches; the pulsation of the
frontal branch is frequently visible on the side of the forehead. The supraorbital
artery can usually be detected immediately above the supraorbital notch or foramen.
SURFACE MARKINGS OF SPECIAL REGIONS OF HEAD AND NECK 1291
SURFACE MARKINGS OF SPECIAL REGIONS OF HEAD AND NECK.
The Cranium. — Scalp. — The soft parts covering the upper surface of the skull
form the scalp and comprise the following layers (Fig. 1196) : (1) skin, (2) subcuta-
neous tissue, (3) Occipitalis frontalis and galea aponeurotica, (4) subaponeurotic tissue,
(5) pericranium. The subcutaneous tissue consists of a close mesh-work of fibers,
the meshes of which contain fatty tissue ; the fibers bind the skin and galea aponeu-
rotica firmly together, so that when the Occipitalis or the Frontalis is in action
the skin moves with the aponeurosis. The subaponeurotic tissue, which intervenes
between the galea aponeurotica and the pericranium, is much looser in texture,
and permits the movement of the aponeurosis over the underlying bones.
Subcutaneous tissue
Galea aponeurotica
Pericranium
Cranial hone
Dura mater
A rachnoid
Pta mater
Superior sagittal sinus
Fig. 1196. — Diagrammatic section of scalp.
Bony Landmarks (Fig. 1193). — In addition to the bony points already described
which can be determined by palpation, the following are utilized for surface
markings:
Auricular Point. — The center of the orifice of the external acoustic meatus.
Preauricular Point. — A point on the posterior root of the zygomatic arch imme-
diately in front of the external acoustic meatus.
Asterion.- — The point of meeting of the lambdoidal, mastooccipital, and masto-
parietal sutures; it lies 4 cm. behind and 12 mm. above the level of the auricular
point.
Pterion. — The point where the great wing of the sphenoid joins the sphenoidal
angle of the parietal; it is situated 35 mm. behind, and 12 mm. above, the level
of the frontozygomatic suture.
Inion. — The external occipital protuberance.
Lambda. — The point of meeting of the lambdoidal and sagittal sutures; it is
in the middle line about G.5 cm. above the inion.
Bregma. — The meeting-point of the coronal and sagittal sutures; it lies at the
point of intersection of the middle line of the scalp with a line drawn vertically
upward through the preauricular point.
A line passing through the inferior margin of the orbit and the auricular point
is known as Reid's base line. The lambdoidal suture can be indicated on either
1292
SURFACE ANATOMY AND SURFACE MARKINGS
side by the upper two-thirds of a line from the lambda to the tip of the mastoid
process. The sagittal suture is in the line joining the lambda to the bregma. The
position of the coronal suture on either side is sufficiently represented by a line
joining the bregma to the center of the zygomatic arch.
The floor of the middle fossa of the skull is at the level of the posterior three-
fourths of the upper border of the zygomatic arch; the articular eminence of the
temporal bone is opposite the foramen spinosum and the semilunar ganglion.
Fig. 1197. — Drawing of a cast by Cunningham to illustrate the relations of the brain to the skull.
Brain (Figs. 1197, 1198). — The general outline of the cerebral hemisphere, on
either side, may be mapped out on the surface in the following manner. Starting
from the nasion, a line drawn along the middle of the scalp to the inion represents
the superior border. The line of the lower margin behind is that of the transverse
sinus (see page 1294), or more roughly a line convex upward from the inion to the
posterior root of the zygomatic process of the temporal bone; thence along the
posterior two-thirds of the upper border of the zygomatic arch where the line turns
up to the pterion ; the front part of the lower margin extends from the pterion to
the glabella about 1 cm. above the supraorbital margin. The cerebellum is so deeply
situated that there is no reliable surface marking for it; a point 4 cm. behind and
1.5 cm. below the level of the auricular point is situated directly over it.
The relations of the principal fissures and gyri of the cerebral hemispheres to
the surface of the scalp are of considerable practical importance, and several
methods of indicating them have been devised. Necessarily these methods can
SURFACE MARKINGS OF SPECIAL REGIONS OF HEAD AND NECK 1293
only be regarded as approximately correct, yet they are all sufficiently accurate
for surgical purposes. The longitudinal fissure corresponds to the medial line of
the scalp between the iiasion and inion. In order to mark out the lateral cerebral
(Sylviaji) fissure a point, termed the Sylvian point, which practically corresponds
to the pterion, is defined 35 mm. behind and 12 mm. above the level of the fronto-
zygomatic suture; this point marks the spot where the lateral fissure divides.
Another method of defining the Sylvian point is to divide the distance between
the nasion and inion into four equal parts; from the junction of the third and
fourth parts (reckoning from the front) draw a line to the frontozygomatic suture;
from the junction of the first and second parts a line to the auricular point. These
two lines intersect at the Sylvian point and the portion of the first line behind
this point overlies the posterior ramus of the lateral cerebral fissure. The position
Fig. 1198. — Relations of the brain and middle meningeal artery to the surface of the skull. I. Nasion. 2. Inion.
3. Lambda. 4. Lateral cerebral fissure. 5. Central sulcus. AA . Reid's base line. B. Point for trephining the anterior
branch of the middle meningeal artery. C. Suprameatal triangle. D. Sigmoid bend of the transverse sinus. E.
Point for trephining over the straight portion of the transverse sinus, exposing dura mater of both cerebrum and
cerebellum. Outline of cerebral hemisphere indicated in blue; course of middle meningeal artery in red.
of the posterior ramus can otherwise be obtained by joining the Sylvian point to a
point 2 cm. below the summit of the parietal eminence. The anterior ascending
ramus can be marked out by drawing a line upward at right angles to the line
of the posterior ramus for 2 cm. and the anterior horizontal ramus by a line of the
same length drawn horizontally forward — both from the Sylvian point. To define
the central sulcus {fissure of Rolando) two points are taken; one is situated 1.25
cm. behind the center of the line joining the nasion and inion; the second is at
the intersection of the line of the posterior ramus of the lateral cerebral fissure
with a line through the preauricular point at right angles to Reid's base line. The
upper 9 cm. of the line joining these two points overlies the central sulcus and forms
an angle, opening forward, of about 70° with the middle line of the scalp. An
alternative method is to draw two perpendicular lines from Ileid's base line to the
top of the head; one from the preauricular point and the other from the posterior
1294 SURFACE ANATOMY AND SURFACE MARKINGS
border of the mastoid process at its root. A line from the upper end of the posterior
line to the point where the anterior intersects the line of the posterior ramus of the
lateral fissure indicates the position of the central sulcus. The precentral and
postcentral sulci are practically parallel to the central sulcus; they are situated
respectively about 15 mm. in front of, and behind, it. The superior frontal sulcus
can be mapped out by a line drawn from the junction of the upper and middle
thirds of the precentral sulcus, in a direction parallel with the longitudinal sulcus,
to a point midway between the middle line of the forehead and the temporal line,
4 cm. above the supraorbital notch. The inferior frontal sulcus begins at the junc-
tion of the middle and lower thirds of the precentral sulcus, and follows the course
of the superior temporal line.
The horizontal limb of the intraparietal sulcus begins from the junction of the
lower with the middle third of the postcentral sulcus and curves backward parallel
to the longitudinal fissure, midway between it and the parietal eminence; it then
curves downward to end midway between the lambda and the parietal eminence.
The external part of the parietooccipital fissure runs lateralward at right angles
to the longitudinal fissure for about 2.5 cm. from a point 5 mm. in front of the
lambda. If the line of the posterior ramus of the lateral cerebral fissure be
continued back to the longitudinal fissure, the last 2.5 cm. of it will indicate the
position of the parietooccipital fissure.
The lateral ventricle may be circumscribed by a quadrilateral figure. The upper
limit is a horizontal line 5 cm. above the zygomatic arch; this defines the roof of
the ventricle. The lower limit is a horizontal line 1 cm. above the zygomatic arch;
it indicates the level of the end of the inferior horn. Two vertical lines, one through
the junction of the anterior and middle thirds of the zygomatic arch, and the other
5 cm. behind the tip of the mastoid process, indicate the extent of the anterior
horn in front and the posterior horn behind.
Vessels. — The line of the anterior division of the middle meningeal artery is
equidistant from the frontozygomatic suture and the zygomatic arch; it is obtained
by joining up the following points: (1) 2.5 cm., (2) 4 cm., and (3) 5 cm. from
these two landmarks. The posterior division can be reached 2.5 cm. above the
auricular point.
The position of the transverse sinus is obtained by taking two lines: the first
from the inion to a point 2.5 cm. behind the auricular point; the second from the
anterior end of the first to the tip of the mastoid process. The second line corre-
sponds roughly to the line of reflection of the skin of the auricula behind, and its
upper two-thirds represents the sigmoid part of the sinus. The first part of the
sinus has a slight upward convexity, and its highest point is about 4 cm. behind
and 1 cm. above the level of the auricular point. The width of the sinus is
about 1 cm.
The Face. — Air Sinuses (Fig. 1199). — The frontal and maxillary sinuses vary
so greatly in form and size that their surface markings must be regarded as only
roughly approximate. To mark out the position of the frontal sinus three points
are taken: (1) the nasion, (2) a point in the middle line 3 cm. above the nasion,
(3) a point at the junction of the lateral and intermediate thirds of the supraorbital
margin. By joining these a triangular field is described which overlies the greater
part of the sinus. The outline of the maxillary sinus is irregularly quadrilateral
and is obtained by joining up the following points: (1) the lacrimal tubercle, (2)
a point on the zygomatic bone at the level of the inferior and lateral margins of the
orbit, (3) and (4) points on the alveolar process above the last molar and the second
premolar teeth respectively.
External Maxillary Artery. — The course of this artery on the face may be indicated
by a line starting from the lower border of the mandible at the anterior margin
of the Masseter, and running at first forward and upward to a point 1 cm. lateral
SURFACE MARKINGS OF SPECIAL REGIONS OF HEAD AND NECK 1295
to the angle of the mouth, thence to the ala of the nose and upward to the medial
commissure of the eye (Fig. 1200).
Trigeminal Nerve.^ — Terminal branches of this nerve, viz., the supraorbital branch
of the ophthalmic, the infraorbitalof the maxillary, and the mentalof the mandibular
emerge from corresponding foramina on the face (Fig. 1200). The supraorbital
foramen is situated at the junction of the medial and intermediate thirds of the
supraorbital margin. A line drawn from this foramen to the lower border of the
mandible, through the interval between the two lower premolar teeth, passes over
the infraorbital and mental foramina; the former lies about 1 cm. below the margin
of the orbit, while the latter varies in position according to the age of the individual;
in the adult it is midway between the upper and lower borders of the mandible,
in the child it is nearer the lower border, while in the edentulous jaw of old age
it is close to the upper margin.
Frontal sinus
Line of nasolacrimal
dud
Maxillary sinus
FiQ. 1199.
-Outline of bones of face, showing position of
air sinuses.
Fig. 1200. — Outline of side of face, showing chief
surface markings.
The position of the sphenopalatine ganglion is indicated from the side by a
point on the upper border of the zygomatic arch, 6 mm. from the margin of the
zygomatic bone.
Parotid Gland (Fig. 1200).- — The upper border of the parotid gland corresponds to
the posterior two-thirds of the lower border of the zygomatic arch; the posterior
border to the front of the external acoustic meatus, the mastoid process, and the
anterior border of Sternocleidomastoideus. The inferior border is indicated by a
line from the tip of the mastoid process to the junction of the body and greater
cornu of the hyoid bone. In front, the anterior border extends for a variable dis-
tance on the superficial surface of the IVIasseter. The surface marking for the parotid
duct is a line drawn across the face about a finger's breadth below the zygomatic
arch, i. e., from the lower margin of the concha to midway between the red margin
1296
SURFACE ANATOMY AND SURFACE MARKINGS
of the lip and the ala of the nose; the duct ends opposite the second upper molar
tooth and measures about 5 cm. in length.
The Nose. — The outlines of the nasal bones and the cartilages forming the exter-
nal nose can be easily felt. The mobile portion of the nasal septum, formed by
the medial crura of the greater alar cartilages and the skin, is easily distinguished
between the nares. When the head is tilted back and a speculum introduced
through the naris, the floor of the nasal cavity, the lower part of the nasal septum,
and the anterior ends of the middle and inferior nasal conchie can be examined.
The opening of the nasolacrimal duct, which lies under cover of the front of the
inferior nasal concha, is situated about 2.5 cm. behind the naris and 2 cm. above
the level of the floor of the nasal ca^'ity.
Pharyngopalatine arch
Palatine tonsil
Glossopalaiine arch
Buccinator
Vallate papillce
•Isthmus
fauciv7n
Fuwjiform papillm
Fig. 1201. — -The mouth cavity. The c}ieeks have been slit transversely and the tongue pulled forward.
The Mouth. — The orifice of the mouth is bounded by the lips, which are covered
externally by the whitish skin and internally by the red mucous membrane. The
size of the orifice varies considerably in different individuals, but seems to bear a
close relationship to the size and prominence of the teeth; its angles usually corre-
spond to the lateral borders of the canine teeth. Running down the center of the
outer surface of the upper lip is a shallow groove — the philtrum. If the lips be
everted there can be seen, in the middle line of each, a small fold of mucous mem-
brane— the frenulum — passing from the lip to the gum. By pulling the angle of the
SURFACE MARKINGS OF SPECIAL REGIONS OF HEAD ANu NECK 1297
mouth outward the mucous membrane of the cheek can be inspected, and on this,
opposite the second molar tooth of the maxilla, is the little papilla which marks
the orifice of the parotid duct.
In the floor of the mouth is the tongue (Fig. 1201). Its upper surface is convex
and is marked along the middle line by a shallow sulcus; the anterior two-thirds
are rough and studded with papillae; the posterior third is smooth and tuberculated.
The division between the anterior two-thirds and the posterior third is marked
by a V-shaped furrow, the sulcus terminalis, which is situated immediately behind
the line of the vallate papillte.
Anterior Ungual gland
Lingtial nerve ^
Art. -profunda lingu
"Vena com. n. hypoglos.
Longitudinal is infer io
Plica fimbrrata
Vena com. n, hypoglossi
Frenulum
Orifice of submax. duct
Plica sublingualis
Fig. 1202. — The mouth cavity. The apex of the tongue is turned upward, and on the right side a superficial
dissection of its under surface has been made.
On the under surface of the tongue (Fig. 1202) the mucous membrane is smooth
and devoid of papillae. In the middle line, the mucous membrane extends to the
floor of the mouth as a distinct fold — the frenulum — the free edge of which runs
forward to the symphysis menti. Sometimes the ranine vein can be seen immedi-
ately beneath the mucous membrane, a little lateral to the frenulum. Close to the
attachment of the frenulum to the floor of the mouth, the slit-like orifice of the
submaxillary duct is visible on either side. Running backward and lateralward
from the orifice of the submaxillary duct is the plica sublingualis, produced by
the projection of the sublingual gland which lies immediately beneath the mucous
membrane. The plica serves also to indicate the line of the submaxillary duct
and of the lingual nerve. At the back of the mouth is the isthmus faucium, bounded
above by the palatine velum, from the free margin of which the uvula projects
downward in the middle line. On either side of the isthmus are the two palatine
arches, the anterior formed by the Glossopalatinus and the posterior by the Pharyn-
82
1298
SURFACE ANATOMY AND SURFACE MARKINGS
gopalatinus. Between the two arches of either side is the palatine tonsil, above
which is the small supratonsillar recess; the position of the tonsil corresponds to
the angle of the mandible. When the mouth is opened widely, a tense band—
the pterygomandibular raphe — can be seen and felt lateral to the glossopalatine
arch. Its lower end is attached to the mandible behind the last molar tooth,
and immediately below and in front of this the lingual nerve can be felt ; the upper
Na-'ial septum
Nasal conchce
Pharyngeal recess
Torus of auditory
tube
F/uiryngeul ostium oj
auditory tube
Fig. 1203. — Front of nasal part of pharynx, as seen with the larj-ngoscope.
end of the ligament can be traced to the pterygoid hamulus. About 1 cm. in front
of the hamulus and 1 cm. medial to the last molar tooth of the maxilla is the greater
palatine foramen through which the descending palatine vessels and the anterior
palatine nerve emerge. Behind the last molar tooth of the maxilla the coronoid
process of the mandible is palpable.
Vallecula
\
Median glossoepiglotttc fold
t
j Epiglottis
/ .Tubercle of epiglottis
mimst^^^ - y Yocal/old
Ventricular fold
A ryepiglottic fold
Cuneiform cartilage
Comiculate cartilage
Trachea
, Fig. 1201. — Laryngoscopic view of interior of larj^nx
By tilting the head well back a portion of the posterior pharyngeal wall, corre-
sponding to the site of the second and third cervical vertebrae, can be seen through
the isthmus faucium. On introducing the finger the anterior surfaces of the upper
cervical vertebrse can be felt through the thin muscular wall of the pharynx;
if the finger be hooked round the palatine velum, the choanse can be distinguished in
front, and the pharyngeal ostium of the auditory tube on either side. The level
of the choanae is that of the atlas, while the palatine velum is opposite the body
of the axis.
SURFACE MARKINGS OF SPECIAL REGIONS OF HEAD AND NECK 1299
With the laryngoscope many other structures can be seen. In the nasal part
of the pharynx (Fig. 1203), the choanae, the nasal septum, the nasal conchae, and
the pharyngeal ostia of the auditory tubes can all be examined. Further down, the
base of the tongue, the anterior surface of the epiglottis with the glossoepiglottic
and pharyngoepiglottic folds bounding the vallecultTe, and the piriform sinuses, are
readily distinguished. Beyond these is the entrance to the larynx, bounded on
either side by the aryepiglottic folds, in each of which are two rounded eminences
corresponding to the corniculate and cuneiform cartilages.
Within the larynx (Fig. 1204) on either side are the ventricular and vocal folds
(false and true vocal cords) with the ventricle between them. Still deeper are
seen the cricoid cartilage and the anterior parts of some of the cartilaginous rings
of the trachea, and sometimes, during deep inspiration, the bifurcation of the
trachea.
The Eye. — The palpebral fissure is elliptical in shape, and varies in form in dif-
ferent individuals and in different races of mankind; normally it is oblique, in a
direction upward and lateralward, so that the lateral commissure is on a slightly
higher level than the medial. When the eyes are directed forward as in ordinary
vision the upper part of the cornea is covered by the upper eyelid and its lower
margin corresponds to the level of the free margin of the lower eyelid, so that
usually the lower three-fourths are exposed.
At the medial commissure (Fig. 1205) are the caruncula lacrimalis and the plica
semilunaris. When the lids are everted, the tarsal glands appear as a series of
nearly straight parallel rows of
light yellow granules. On the
margins of the lids about 5 mm.
from the medial commissure are ^ ^^ /^^^^ j ^\\^>\x
two small openings — the lacrimal "'l'^ '^Nr^\/ ^^'^m
puncta; in the natural condition '''^^
they are in contact with the con-
junctiva of the bulb of the eye, Piinctumlacrimale-
so that it is necessary to evert
the eyelids to expose them. The
position of the lacrimal sac is indi-
cated by a little tubercle which
can be plainly felt on the lower
margin of the orbit; the sac lies
immediately above and medial to
the tubercle. If the eyelids be
drawn lateralward so as to tighten
the skin at the medial commissure
a prominent core can be felt be-
neath the tightened skin; this is the medial palpebral ligament, which lies over
the junction of the upper with the lower two-thirds of the sac, thus forming a
useful guide to its situation. The direction of the nasolacrimal duct is indicated
by a line from the lacrimal sac to the first molar tooth of the maxilla; the length
of the duct is about 12 or 13 mm.
On looking into the eye, the iris with its opening, the pupil, and the front of the
lens can be examined, but for investigation of the retina an ophthalmoscope is neces-
sary. With this the lens, the vessels of the retina, the optic disk, and the macula
lutea can all be inspected (Fig. 1206).
On the lateral surface of the nasal part of the frontal bone the pulley of the
Obliquus superior can be easily reached by pushing the finger backward along the
roof of the orbit ; the tendon of the muscle can be traced for a short distance back-
ward and lateralward from the pulley.
I'lica semilunaris
Caruncula
Punctum lacrimale
Openings of tarsal
glands
Fig.
1205. — Front of left eye with eyelids separated to show
medial canthus.
1300
SURFACE ANATOMY AND SURFACE MARKINGS
Optic disc
Macida lutea
Sclera
Choroid
Betina
Fig. 1206. — The interior of tlie posterior half of the left eyeball.
The Ear. — The various prominences and fossse of the auricula (see page 1034)
are visible (Fig. 1207). The opening of the external acoustic meatus is exposed by
drawing the tragus forward; at the orifice are a few
short crisp hairs which serve to prevent the entrance
of dust or of small insects; beyond this the secretion
of the ceruminous glands serves to catch any small
particles which may find their way into the meatus.
The interior of the meatus can be examined through
a speculum. At the line of junction of its bony
and cartilaginous portions an obtuse angle is formed
which projects into the antero-inferior wall and
produces a narrowing of the lumen in this situation.
The cartilaginous part, however, is connected to the
bony part by fibrous tissue which renders the outer
part of the meatus very movable, and therefore by
drawing the auricula upward, backward, and slightly
outward, the canal is rendered almost straight. In
children the meatus is very short, and this should
be remembered in introducing the speculum.
Through the speculum the greater part of the tym-
panic membrane (Fig. 1208) is visible. It is a pearly-
gray membrane slightly glistening in the adult, placed
obliquely so as to form with the floor of the meatus an angle of about 55°. At
birth it is more horizontal and situated in almost the same plane as the base of the
skull. The membrane is concave outward, and the point of deepest concavity —
the umbo — is slightly below the center. Running upward and slightl}^ forward
from the umbo is a reddish-yellow streak produced by the manubrium of the
malleus. This streak ends above just below the roof of the meatus at a small
white rounded prominence which is caused by the lateral process of the malleus
projecting against the membrane. The anterior and posterior malleolar folds
extend from the prominence to the circumference of the membrane and enclose
the pars flaccida. Behind the streak caused by the manubrium of the malleus a
second streak, shorter and very faint, can be distinguished; this is the long crus
Fig. 1207. — The auricula or pinna.
Lateral surface.
SURFACE MARKINGS OF SPECIAL REGIONS OF HEAD AND NECK 1301
of the incus. A narrow triangular patch extending downward and forward from the
umbo reflects the light more brightly than any other part, and is usually described
as the cone of light.
Post, malleolar f eld
Long crus of incus I
Manuhrium
of malleus
Postero-supcrior
quadrant
Postero-inferior
quMdrant
Pars flaccida
I Lat. proc. of tnallcus
^ Ant. malleolar fold
Antero-superior
quadrant
Umbo
of light
Antcro-infcrior quadrant
Fig. 1208. — The right tympanic membrane as seen through a speculum.
Groove for middle
temporal artery
ff £f /f^ ^« Parietal notch
Suprameatal
triangle
Occipitalis
Articular tubercle
Postglenoid process
Mandibular fossa
Petrotympanic fissure
Vaginal process
Styloglossus
Occipital groove
Tympanic part
STYLOHYOIDEtra
Styloid process
Fig. 1209. — Left temporal bone .showing surface markings for the tympanic antrum (red), transverse sinus (blue),
and facial nerve (yellow).
Tympanic Antrum. — The site of the tympanic antrum is indicated by the supra-
meatal triangle (Fig. 1209). This triangle is bounded above by the posterior root
of the zygomatic arch; behind by a vertical line from the posterior border of the
external acoustic meatus; in front and below by the upper margin of the meatus.
The Neck (Fig. 1210). — ^Larynx and Trachea. — In the receding angle below the
chin, the hyoidbone (page 12S8), situated opposite the fourth cervical vertebra, can
easily be made out. A finger's breadth below it is the laryngeal prominence of the
1302
SURFACE ANATOMY AND SURFACE MARKINGS
thyroid cartilage; the space intervening between the hyoid bone and the thyroid
cartilage is occupied by the hyothjrroid membrane. The outHnes of the thyroid
cartilage are readily palpated; below its lower border is a depression corresponding
to the middle cricothyroid ligament. The level of the vocal folds corresponds to
the middle of the anterior margin of the thyroid cartilage. The anterior part of
the cricoid cartilage forms an important landmark on the front of the neck; it
lies opposite the sixth cervical vertebra, and indicates the junctions of pharynx
with esophagus, and larynx with trachea. Below the cricoid cartilage the trachea
can be felt, though it is only in thin subjects that the separate rings can be distin-
guished; as a rule there are seven or eight rings above the jugular notch of the
sternum, and of these the second, third, and fourth are covered by the isthmus
of the thyroid gland.
Ext. max. art. -
Lingual art. '
Sup. th}iroidart. '
Point of bifurcation -
of com. carotid art.
Com. carotid art.
Subclavian art
Facial nerve
- ■ Ext. carotid art
Occipital art.
- Lesser oceip. nerve»
Great auric, nerve
Cervical cutan. nerve
Acce-^sonj nerve
Supraclavic. nerves
Line of upper margin
of brachial plexus
Fig. 1210. — Side of neck, showing chief surface markings.
Muscles. — The posterior belly of Digastricus is marked out by a line from the tip
of the mastoid process to the junction of the greater cornu and body of the hyoid
bone; a line from this latter point to a point just lateral to the symphysis menti
indicates the position of the anterior belly. The line of Omohyoideus begins at
the lower border of the hvoid bone, curves downward and lateralward to cross
Sternocleidomastoideus at the junction of its middle and lower thirds, i. e., opposite
the cricoid cartilage, and then runs more horizontally to the acromial end of the
clavicle.
Arteries.^ — ^The position of the common carotid artery in the neck is indicated
by a line drawn from the upper part of the sternal end of the clavicle to a point
midway between the tip of the mastoid process and the angle of the mandible.
From the clavicle to the upper border of the thyroid cartilage this line overlies
the common carotid arte^^•, be^•ond this it is over the external carotid. The
external carotid artery may otherwise be marked out by the upper part of a line
from the side of the cricoid cartilage to the front of the external acoustic meatus,
arching the line slightly forward.
The points of origin of the main branches of the external carotid in the neck
are all related to the tip of the greater cornu of the hyoid bone as follows: [l) the
superior thyroid, immediately below it; (2) the lingual, on a level with it; (3) the
facial, and (4) the occipital a little above and behind it.
SURFACE ANATOMY OF THE BACK 1303
The subclavian artery is indicatetl on the surface by a curved hue, convex upward,
from the sternocUivicuhir articulation to the middle of the clavicle. The highest
point of the convexity is from 1 to 3 cm. above the clavicle.
Veins. — ^The surface marking for the internal jugular vein is slightly lateral
and parallel to that for the common carotid artery. The position of the external
jugular vein is marked out by a line from the angle of the mandible to the middle
of the clavicle. A point on this line about 4 cm. above the clavicle indicates the
spot where the vein pierces the deep fascia. The line of the anterior jugular vein
begins close to the symphysis menti, runs downward parallel with and a little
to one side of the middle line and, at a variable distance above the jugular notch,
turns lateralward to the external jugular.
Nerves. — The facial nerve at its exit from the stvlomastoid foramen is situated
about 2.5 cm. from the surface, opposite the middle of the anterior border of the
mastoid process; a horizontal line from this point to the ramus of the mandible
overlies the stem of the nerve. To mark the site of the accessory nerve a line is
drawn from the angle of the mandible to a point on the anterior border of Sterno-
cleidomastoideus about 3 to 4 cm. below the apex of the mastoid process, or to the
midpoint of the posterior border of the muscle; the line is continued across the
posterior triangle to Trapezius.
The cutaneous branches of the cervical plexus as they emerge from the posterior
border of Sternocleidomastoideus may be indicated as follows: the lesser occipital
begins immediately above the midpoint of the border and runs along the border to
the scalp; the great auricular and cervical cutaneous both start from the middle
of the border, the former running upward toward the lobule of the auricula, the
latter crossing Sternocleidomastoideus at right angles to its long axis; the supra-
clavicular nerves emerge from immediately below the middle of the posterior border
and run down over the clavicle. The phrenic nerve begins at the level of the middle
of the thyroid cartilage and runs behind the clavicle about midway between the
anterior and posterior borders of Sternocleidomastoideus.
The upper border of the brachial plexus is indicated by a line from the side of
the cricoid cartilage to the middle of the clavicle.
Submaxillary Gland. — On either side of the neck the superficial portion of the
submaxillary gland, as it lies partly under cover of the mandible, can be palpated.
SURFACE ANATOMY OF THE BACK.
Bones. — ^The only subcutaneous parts of the vertebral column are the apices
of the spinous processes. These are distinguishable at the bottom of a furrow
which runs down the middle line of the back from the external occipital protuber-
ance to the middle of the sacrum. In the cervical region the furrow is broad and
ends below in a conspicuous projection caused by the spinous processes of the
seventh cervical and first thoracic vertebrae. Above this, the spinous process of the
sixth cervical vertebra sometimes forms a projection; the other cervical spinous
processes are sunken, but that of the axis can be felt. In the thoracic region the
furrow is shallow and during stooping disappears, and then the spinous processes
become more or less visible; the markings produced by them are small and close
together. In the lumbar region the furrow is deep and the situations of the spinous
processes are frequently indicated by little pits or depressions, especially when the
muscles in the loins are well-developed. In the sacral region the furrow is shallower,
presenting a flattened area which ends below at the most prominent part of the
dorsal surface of the sacrum, i. e., the spinous process of the third sacral vertebra.
At the bottom of the sacral furrow the irregular dorsal surface of the bone may be
felt, and below this, in the deep groove running to the anus, the coccyx.
The only other portions of the vertebral column which can be felt from the
surface are the transverse processes of the first, sixth, and seventh cervical vertebrae.
1304 SURFACE ANATOMY AND SURFACE MARKINGS
Muscles.— The muscles proper of the back are so obscured by those of the upper
extremity (Fig. 1211) that they have very Httle influence on surface form. The
Splenii by their divergence ser^e to broaden out the upper part of the back of the
neck and produce a fulness in this situation. In the loin the Sacrospinales, bound
Trapezius
Spine of scapula
Rliomboideus major
/--^ / Teres major
7 V
Deltoideus
I
Inf. angle of scapula
Laiissimus dorsi
Glutaeus medius
Glutwus maxivius
Fig. 1211. — Surface anatomv of the back.
down by the lumbodorsal fascia, form rounded vertical eminences which determine
the depth of the spinal furrow and taper below to a point on the dorsal surface of
the sacrum. The continuations of the Sacrospinales in the lower thoracic region
form flattened planes which are gradually lost on passing upward.
SURFACE MARKINGS OF THE BACK
1305
SURFACE MARKINGS OF THE BACK.
Bony Landmarks. — In order to identify any particular spinous process it is
customary to count from the prominence caused by the seventh cervical and first
Fig. 1212.-
-Diagram showing the relation of the medulla spinalis to thu dorsal surface of the trunk.
are outlined in red.
The bones
Level of
No. of •
Level of tip
Level of
No. of Level of tip
body of
nerve.
C. 1
of spine of
body of
nerve. of spine of
C. 1
T. 8
T. 9
7 T.
2
il
9
10
8
1 C.
10
11
9
3
4
2
12
10
4
5
3
11
L. 1
11
5
6
4
2
6
.7
5
12
•
3
, ,
8
6
, ^
14.
12
7
T. 1
7
5)
. ,
T. 1
2
1 T.
s. i;
2
3
L. 1
2^
3
4
2
1 •
3
4
5
3
4
■
1 L.
5
6
4
5
6
7
5
C. Ij
7
8
6
j L. 2
1306
SURFACE ANATOMY AND SURFACE MARKINGS
Fig. 1213. — Sagittal section of vertebral canal to
show the lower end of the medulla spinalis and the
filum terminale. (Testut.) Li, Lv. First and fifth
lumbar vertebrae. Sii. Second sacral vertebra. 1.
Dura mater. 2. Lower part of subarachnoid cavity.
3. Lower extremity of medulla spinalis. 4. Filum ter-
minale internum, and .5, Filum terminale externum.
6. Attachment of filum terminale to first segment of
coccyx.
}
thoracic; of these the latter is the more prominent. The root of the spine of the
scapula is on a level with the tip of the spinous process of the third thoracic vertebra,
and the inferior angle with that of the seventh. The highest point of the iliac
crest is on a level with the spinous
process of the fourth lumbar, and the
posterior superior iliac spine with that
of the second sacral.
The transverse process of the atlas
is about 1 cm. below and in front of
the apex of the mastoid process. The
transverse process of the sixth cervical
vertebra is opposite the cricoid cartil-
age; below it is the transverse pro-
cess of the seventh and occasionally
a cervical rib.
z ndCervicall ®.
e^^Cervical
6^Cerviccd
Z'^Thomcic
3^^ Cervical
sthQervical
Y^^^Cervical
j^-^ Thoracic
^^h Thoracic <
6'^^Thoracic<
6'^Th
'z '^hThoracic
yiri'^lnoracic
j^fLumbar
y^^f^Lumbar
S^^Lumbar
Coccygeal
Fig. 1214. — Scheme showing the relations of the
regions of attachment of the spinal nerves to the verte-
bral spinous processes. (After Heid.)
Medulla Spinalis. — The position of the lower end of the medulla spinalis varies
slightly wdth the movements of the vertebral column, but, in the adult, in the
upright posture it is usually at the level of the spinous process of the second lumbar
vertebra (Fig. 1212); at birth it lies at the level of the fourth lumbar.
The subdural and subarachnoid cavities end below opposite the spinous process
of the third sacral vertebra (Fig. 1213).
SURFACE ANATOMY OF THE THORAX 1307
Spinal Nerves (Fig. 1214). — The table on page 1305, after Macalister, shows the
reUitions which the pLices of attachment of the ner\es to the medulla spinalis
present to the bodies and spinous processes of the vertebra?.
SURFACE ANATOMY OF THE THORAX.
Bones. — The skeleton of the thorax is to a very considerable extent covered by
muscles, so that in the strongly developed muscular subject it is for the most part
concealed. In the emaciated subject, however, the ribs, especially in the lower and
lateral regions, stand out as prominent ridges with the sunken intercostal spaces
between them.
In the middle line, in front, the superficial surface of the sternum can be felt
throughout its entire length at the bottom of a furrow, the sternal furrow, situated
between the Pectorales majores. These muscles overlap the anterior surface
somewhat, so that the whole width of the sternum is not subcutaneous, and this
overlapping is greatest opposite the middle of the bone; the furrow, therefore, is
wide at its upper and lower parts but narrow in the middle. At the upper border
of the manubrium sterni is the jugular notch: the lateral parts of this notch are
obscured by the tendinous origins of the Sternocleidomastoidei, which appear as
oblique cords narrowing and deepening the notch. Lower down on the subcu-
taneous surface is a well-defined transverse ridge, the sternal angle; it denotes the
junction of the manubrium and body. From the middle of the sternum the sternal
furrow spreads out and ends at the junction of the body with the xiphoid process.
Immediately below this is the infrastemal notch; between the sternal ends of the
seventh costal cartilages, and below the notch, is a triangular depression, the
epigastric fossa, in which the xiphoid process can be felt.
On either side of the sternum the costal cartilages and ribs on the front of the
thorax are partly obscured by the Pectoralis major, through which, however, they
can be felt as ridges with yielding intervals between them corresponding to the
intercostal spaces. Of these spaces, that between the second and third ribs is the
widest, the next two are somewhat narrower, and the remainder, with the exception
of the last two, are comparatively narrow.
Below the lower border of the Pectoralis major on the front of the chest, the
broad flat outlines of the ribs as they descend, and the more rounded outlines of the
costal cartilages, are often visible. The lower boundary of the front of the thorax,
which is most plainly seen by bending the body backward, is formed by the xiph jid
process, the cartilages of the seventh, eighth, ninth, and tenth ribs, and the ends of
the cartilages of the eleventh and twelfth ribs.
On either side of the thorax, from the axilla downward, the flattened external
surfaces of the ribs may be defined. Although covered by muscles, all the ribs,
with the exception of the first, can generally be followed without difficulty over the
front and sides of the thorax. The first rib being almost completely covered by
the clavicle can only be distinguished in a small portion of its extent.
At the back, the angles of the ribs lie on a slightly marked oblique line on either
side of, and some distance from, the spinous processes of the vertebra?. The line
diverges somewhat as it descends, and lateral to it is a broad convex surface caused
by the projection of the ribs beyond their angles. Over this surface, except where
covered by the scapula, the individual ribs can be distinguished.
Muscles. — The surface muscles covering the thorax belong to the musculature
of the upper extremity (Figs. 1215, 1219), and will be described in that section
(page 1325). There is, however, an area of practical importance bounded by these
muscles. It is limited above by the lower border of Traper.ius, below by the upper
border of Latissimus dorsi, and laterally by the vertebral border of the scapula; the
1308
SURFACE ANATOMY AND SURFACE MARKINGS
floor is partly formed by Rhomboideus major. If the scapula be drawn forward by
folding the arms across the chest, and the trunk bent forward, parts of the sixth
and seventh ribs and the interspace between them become subcutaneous and avail-
able for ausculation. The space is therefore known as the triangle of ausculation.
^■
__,a*«rlifi«*'*^-
Pectoralis major
o ^ Trapezius
Serratus anterior
Obliquus externus
Bectus abdominis
Latissimus dorsi
Fio. 1215. — The left side of the thorax.
Mamma. — The size of the mamma is subject to great variations. In the adult
nuUiparous female, it extends vertically from the second to the sixth rib, and
transversely from the side of the sternum to the midaxillary line. In the male and
in the nulliparous female the mammary papilla is situated in the fourth interspace
about 9 or 10 cm. from the middle line, or 2 cm. from the costochondral junction.
SURFACE MARKINGS OF THE THORAX.
Bony Landmarks. — The second costal cartilage corresponding to the sternal
angle is so readily found that it is used as a starting-point from which to count the
ribs. The lower border of the Pectoralis major at its attachment corresponds to
the fifth rib; the uppermost visible digitation of Serratus anterior indicates the
sixth rib.
The jugular notch is in the same horizontal plane as the lower border of the body
of the second thoracic vertebra; the sternal angle is at the level of the fifth thoracic
vertebra, while the junction between the body and xiphoid process of the sternum
corresponds to the fibrocartilage between the ninth and tenth thoracic vertebrae.
The influence of the obliquity of the ribs on horizontal levels in the thorax is
well shown by the following line. " If a horizontal line be drawn around the body
at the level of the inferior angle of the scapula, Mdiile the arms are at the sides, the
SURFACE MARKINGS OF THE THORAX
1309
line would cut the sternum in front between the fourth and fifth ribs, the fifth rib
in the nipple line, and the ninth rib at the vertebral column." (Treves).
Diaphragm. — The shape and variations of the diaphragm as seen by skiag-
raphy have already been described (page 407).
Surface Lines. — For clinical purposes, and for convenience of description, the
surface of the thorax has been mapped out by arbitrary lines (Fig. 1220). On the
front of the thorax the most important vertical lines are the midsternal, the middle
line of the sternum; and the mammary, or, better midclavicular, which runs verti-
cally downward from a point midway between the center of the jugular notch and
the tip of the acromion. This latter line, if prolonged, is practically continuous
with the lateral line on the front of the abdomen. Other vertical lines on the front
of the thorax are the lateral sternal along the sternal margin, and the parasternal
midway between the lateral sternal and the mammary.
On either side of the thorax the anterior and posterior axillary lines are drawn
vertically from the corresponding axillary folds; the midaxillary line runs down-
ward from the apex of the axilla.
On the posterior surface of the thorax the scapular line is drawn vertically
through the inferior angle of the scapula.
Fio. 1216. — Front of thorax, showing surface relations of bones, lungs (purple), pleura, (blue), and heart (red
outline). P. Pulmonary valve. A. Aortic valve. B. Bicuspid valve. T. Tricuspid valve.
Pleurae (Figs. 1216, 1217). — The lines of reflection of the pleurae can be indicated
on the surface. On the right side the line begins at the sternoclavicular articulation
and runs downward and medialward to the midpoint of the junction between the
manubrium and body of the sternum. It then follows the midsternal line to the
lower end of the body of the sternum or on to the xiphoid process, where it turns
lateralward and downward across the seventh sternocostal articulation. It crosses
the eighth costochondral junction in the mammary line, the tenth rib in the mid-
axillary line, and is prolonged thence to the spinous process of the twelfth thoracic
vertebra.
1310
SURFACE ANATOMY AND SURFACE MARKINGS
On the left side, beginning at the sternoclavicular articulation, it reaches the
midpoint of the junction between the manubrium and body of the sternum, and
extends down the midsternal line in contact with that of the opposite side to the
level of the fourth costal cartilage. It then diverges lateralward and is continued
downward slightly lateral to the sternal border, as far as the sixth costal cartilage.
Running downward and lateralward from this point it crosses the seventh costal
cartilage, and from this onward it is similar to the line on the right side, but at a
slightly lower level.
Lungs (Figs. 1216, 1217). — ^The apex of the lung is situated in the neck above the
medial third of the clavicle. The height to which it rises above the clavicle varies
very considerably, but is generally about 2.5 cm. It may, however, extend as
high as 4 or 5 cm., or, on the other hand, may scarcely project above the level
of this bone.
Fig. 1217. — Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green).
In order to mark out the anterior borders of the lungs a line is drawn from each
apex point — 2.5 cm. above the clavicle and rather nearer the anterior than the
posterior border of Sternocleidomastoideus — downward and medialward across the
sternoclavicular articulation and manubrium sterni until it meets, or almost meets,
its fellow of the other side at the midpoint of the junction between the manubrium
and body of the sternum. From this point the two lines run downward, prac-
tically along the midsternal line, as far as the level of the fourth costal cartilages.
The continuation of the anterior border of the right lung is marked by a prolonga-
tion of its line vertically downward to the level of the sixth costal cartilage, and
then it turns lateralward and downward. The line on the left side curves lateralward
and downward across the fourth sternocostal articulation to reach the parasternal
line at the fifth costal cartilage, and then turns medialward and downward to the
sixth sternocostal articulation.
SURFACE MARKINGS OF THE THORAX 1311
In the position of expiration the lower border of the lung may be marked hy a
sHghtly curved Hne with its convexity downward, from the sixth sternocostal
junction to the tenth thoracic spinous process. This line crosses the mid-clavic-
ular line at the sixth, and the midaxillarv line at the eighth rib.
The posterior borders of the lungs are indicated by lines drawn from the level
of the spinous process of the seventh cervical vertebra, down either side of the
vertebral column, across the costovertebral joints, as low as the spinous process
of the tenth thoracic vertebra.
The position of the oblique fissure in either lung can be shown by a line drawn
from the spinous process of the second thoracic vertebra around the side of the
thorax to the sixth rib in the mid-clavicular line; this line corresponds roughly to
the line of the vertebral border of the scapula when the hand is placed on the top of
the head. The horizontal fissure in the right lung is indicated by a line drawn from
the midpoint of the preceding, or from the point where it cuts the midaxillary line,
to the midsternal line at the level of the fourth costal cartilage.
Trachea. — This may be marked out on the back by a line from the spinous
process of the sixth cervical to that of the fourth thoracic vertebra where it bifur-
cates; from its bifurcation the two bronchi are directed downward and lateralward.
In front, the point of bifurcation corresponds to the sternal angle.
Esophagus. — The extent of the esophagus may be indicated on the back by a
line from the sixth cervical to the level of the ninth thoracic spinous process,
2.5 cm. to the left of the middle line.
Heart. — The outline of the heart in relation to the front of the thorax (Figs
121G, 1218) can be represented by a quadrangular figure. The apex of the heart
is first determined, either by its pulsation or as a point in the fifth interspace,
9 cm. to the left of the midsternal line. The other three points are: (a) the seventh
right sternocostal articulation; (h) a point on the upper border of the third right
costal cartilage 1 cm. from the right lateral sternal line; (c) a point on the lower
border of the second left costal cartilage 2.5 cm. from the left lateral sternal line.
A line joining the apex to point (a) and traversing the junction of the body of the
sternum with the xiphoid process represents the lowest limit of the heart — its
acute margin. The right and left borders are represented respective!}' by lines
joining (a) to (6) and the apex to (c); both lines are convex lateralward, but the
convexity is more marked on the right where its summit is 4 cm. distant from the
midsternal line opposite the fourth costal cartilage.
A portion of the area of the heart thus mapped out is uncovered by lung, and
therefore gives a dull note on percussion; the remainder being overlapped by lung
gives a more or less resonant note. The former is known as the area of superficial
cardiac dulness, the latter as the area of deep cardiac dulness. The area of super-
ficial cardiac dulness is somewhat triangular; from the apex of the heart two lines
are drawn to the midsternal line, one to the level of the fourth costal cartilage,
the other to the junction between the body and xiphoid process; the portion of the
midsternal line between these points is the base of the triangle. Latham lays
down the following rule as a sufficient practical guide for the definition of the area
of superficial dulness. " jMake a circle of two inches in diameter around a point
midway between the nipple and the end of the sternum."
The coronary sulcus can be indicated by a line from the third left, to the sixth
right, sternocostal joint. The anterior longitudinal sulcus is a finger's breadth to
the right of the left margin of the heart.
The position of the various orifices is as follows: The pulmonary orifice is sit-
uated in the upper angle of the third left sternocostal articulation; the aortic
orifice is a little below and medial to this, close to the articulation. The left atrio-
ventricular opening is opposite the fourth costal cartilage, and rather to the left
of the midsternal line; the right atrioventricular opening is a little lower, opposite
1312
SURFACE ANATOMY AND SURFACE MARKINGS
the fourth interspace of the right side. The lines indicating the atrioventricular
openings are slightly below and parallel to the line of the coronary sulcus.
Arteries.— The line of the ascending aorta begins slightly to the left of the mid-
sternal line opposite the third costal cartilage and extends upward and to the
right to the upper border of the second right costal cartilage. The beginning of
the aortic arch is indicated by a line from this latter point to the midsternal line
about 2.5 cm. below the jugular notch. The point on the midsternal line is oppo-
site the summit of the arch, and a line from it to the right sternoclavicular articu-
lation represents the site of the innominate artery, while another line from a point
slightly to the left of it and passing through the left sternoclavicular articulation
indicates the position of the left common carotid artery in the thorax.
I
Fig. 1218. — Diagram showing relations of opened heart to front of thoracic wall. Ant. Anterior segment of tri-
cuspid valve. A O. Aorta. A.P. Anterior papillary muscle. In. Innominate artery. i^.CC Left common carotid
artery. L.S. Left subclavian artery. L.V. Left ventricle. P. A. Pulmonary artery. R.A. Right atrium. R.V.
Right ventricle. V.S. Ventricular septum.
The internal mammary artery descends behind the first six costal cartilages
about 1 cm. from the lateral sternal line.
Tains. — The line of the right iimominate vein crosses the right sternoclavicular
joint and the upper border of the first right costal cartilage about 1 cm. from the
lateral sternal line; that of the left innominate vein extends from the left sterno-
clavicular articulation to meet the right at the upper border of the first right
costal cartilage. The junction of the two lines indicates the origin of the superior
vena cava, the line of which is continued vertically down to the level of the third
right costal cartilage. The end of the inferior vena cava is situated opposite the
upper margin of the sixth right costal cartilage about 2 cm. from the mid-
sternal line.
SURFACE ANATOMY OF THE ABDOMEN 1313
SURFACE ANATOMY OF THE ABDOMEN.
Skin. — The skin of the front of the abdomen is thin. In the male it is often
thickly hair-clad, especially toward the lower part of the middle line; in the female
the hairs are confined to the pubes. Just below the line of the iliac crest, especially
marked in fat subjects, is a shallow groove termed the iliac furrow, while in the
site of the inguinal ligament a sharper fold known as the fold of the groin is easily
distinguishable.
After distension of the abdomen from pregnancy or other causes the skin com-
monly presents transverse white lines which are quite smooth, being destitute
of papillae; these are known as striae gravidarum or striae albicantes. The linea
nigra of pregnancy is often seen as a pigmented brown streak in the middle line
between the umbilicus and symphysis pubis.
In the middle line of the front of the abdomen is a shallow furrow which extends
from the junction between the body of the sternum with the xiphoid process to a
short distance below the umbilicus; it corresponds to the linea alba. The umbilicus
is situated in the middle line, but it varies in position as regards its height; in an
adult subject it is always placed above the middle point of the body, and in a nor-
mal well-nourished subject is from 2 to 2.5 cm. above the level of the tubercles
of the iliac crests.
Bones. — The bones in relation with the surface of the abdomen are (1) the lower
part of the vertebral column and the lower ribs and (2) the pelvis; the former
have already been described (page 1303), the latter will be considered with the
lower limb.
Muscles (Fig. 1219). — The only muscles of the abdomen which have any consider-
able influence on surface form are the Obliquus externus and the Rectus. The
upper digitations of origin of Obliquus externus are well-marked in a muscular sub-
ject, interdigitating with those of Serratus anterior; the lower digitations are cov-
ered by the border of Latissimus dorsi and are not visible. The attachment of the
Obliqui externus and internus to the crest of the ilium forms a thick oblique roll
which determines the iliac furrow. Sometimes on the front of the lateral region of
the abdomen an undulating line marks the passing of the muscular fibers of the
Obliquus externus into its aponeurosis. The lateral margin of the Obliquus externus
is separated from that of the Latissimus dorsi by a small triangular interval — the
lumbar triangle — the base of which is formed by the iliac crest, and its floor by
Obliquus internus.
The lateral margin of Rectus abdominis is indicated by the linea semilunaris,
which may be exactly defined by putting the muscle into action. The surface of
the Rectus presents three transverse furrows, the tendinous inscriptions : the upper
two of these, viz., one opposite, or a little below, the tip of the xiphoid process,
and the other midway between this point and the umbilicus, are usually well-
marked; the third, opposite the umbilicus, is not so distinct. Between the two
Recti the linea alba can be palpated from the xiphoid process to a point just below
the umbilicus; it is represented by a distinct dip between the muscles: beyond
this the muscles are in apposition.
Vessels. — In thin subjects the pulsation of the abdominal aorta can be readily
felt by making deep pressure in the middle line above the umbilicus.
Viscera. — Under normal conditions the various portions of the digestive tube
cannot be identified by simple palpation. Peristalsis of the coils of small intestine
can be observed in some persons with extremely thin abdominal walls when some
degree of constipation exists. In cases of constipation it is sometimes possible to
trace portions of the great intestine by feeling the fecal masses within the gut.
In thin persons with relaxed abdominal walls the iliac colon can be felt in the left
83
1314
SURFACE ANATOMY AND SURFACE MARKINGS
iliac region — rolling under the fingers when empty and forming a distinct tumor
when distended.
The greater part of the liver lies under cover of the lower ribs and their cartilages,
but in the epigastric fossa it comes in contact with the abdominal wall. The
I
I nfrasttrnal notch
Pectoralis major
I
^i err at us
anterior
Rectus abdominis
Linca alba
Aponeurosis of
Obliquus externus
Muscular fibers of
Obliquus externus
A ntericr superior
iliac spine
Inguivxil ligament
Fig. 1219. — Surface anatomy of the front of the thorax and abdomen.
position of the liver varies according to the posture of the body. In the erect
posture in the adult male the edge of the liver projects about 1 cm. below the
lower margin of the right costal cartilages, and its inferior margin can often be felt
in this situation if the abdominal wall is thin. In the supine position the liver
SURFACE MARKINGS OF THE ABDOMEN 1315
recedes above the margin of the ribs and cannot then be detected by the finger;
in the prone position it falls forward and is then generally palpable in a patient
with loose and lax abdominal walls. Its position varies with the respiratory
movements; during a deep insjiiration it descends below the ribs; in expiration
it is raised. Pressure from without, as in tight lacing, b}^ compressing the lower
part of the chest, displaces the liver considerably, its anterior edge frequently
extending as low as the crest of the ilium. Again its position varies greatly with
the state of the stomach and intestines; when these are empty the liver descends,
when they are distended it is pushed upward.
The pancreas can sometimes be felt, in emaciated subjects, when the stomach
and colon are empty, by making deep pressure in the middle line about 7 or 8 cm.
above the umbilicus.
The kidneys being situated at the back of the abdominal cavity and deeply
placed cannot be palpated unless enlarged or misplaced.
SURFACE MARKINGS OF THE ABDOMEN.
Bony Landmarks. — Above, the chief bony markings are the xiphoid process,
the lower six costal cartilages, and the anterior ends of the lower si^ ribs. The
junction between the body of the sternum and the xiphoid process is on the level
of the tenth thoracic vertebra. Below, the main landmarks are the symphysis
pubis and the pubic crest and tubercle, the anterior superior iliac spine, and the
iliac crest.
Muscles (Fig. 1227). — ^The Rectus lies between the linea alba and the linea semi-
lunaris; the former is indicated by the middle line, the latter by a curved line,
convex lateralward, from the tip of the cartilage of the ninth rib to the pubic
tubercle; at the level of the umbilicus the linea semilunaris is about 7 cm. from the
middle line. The line indicating the junction of the muscular fibers of Obliquus
extemus with its aponeurosis extends from the tip of the ninth costal cartilage
to a point just medial to the anterior superior iliac spine.
The umbilicus is at the level of the fibrocartilage between the third and fourth
lumbar vertebra?.
The subcutaneous inguinal ring is situated 1 cm. above and lateral to the pubic
tubercle; the abdominal inguinal ring lies 1 to 2 cm. above the middle of the inguinal
ligament. The position of the inguinal canal is indicated by a line joining these
two points.
Surface Lines. — For convenience of description of the viscera and of reference
to morbid conditions of the contained parts, the abdomen is divided into nine
regions, by imaginary planes, two horizontal and two sagittal, the edges of the planes
being indicated by lines drawn on the surface of the body (Fig. 1220). In the older
method the upper, or subcostal, horizontal line encircles the body at the level of the
lowest points of the tenth costal cartilages; the lower, or intertubercular, is a line
carried through the highest points of the iliac crests seen from the front, i. e.,
through the tubercles on the iliac crests about 5 cm. behind the anterior superior
spines. An alternative method is that of Addison; who adopts the following lines:
(1) An upper transverse, the transpyloric, halfway between the jugular notch
and the upper border of the symphysis pubis; this indicates the margin of the
transpyloric plane, which in most cases cuts through the pylorus, the tips of the
ninth costal cartilages and the lower border of the first lumbar vertebra; (2) a
lower transverse line midway between the upper transverse and the upper border
of the symphysis pubis; this is termed the transtubercular, since it practically corre-
sponds to that passing through the iliac tubercles; behind, its plane cuts the body
of the fifth lumbar vertebra.
1316
SURFACE ANATOMY AND SURFACE MARKINGS
By means of these horizontal planes the abdomen is divided into three zones
named from above, the subcostal, umbilical, and hypogastric zones. Each of these
is further subdivided into three regions by the two sagittal planes, which are indi-
cated on the surface by a right and a left lateral line drawn vertically through
points halfway between the anterior superior iliac spines and the middle line. The
middle region of the upper zone is called the epigastric, and the two lateral regions
Lateral sternal line
, Parasternal line
Mammary line
T^anspyloTnc
plane
\Irans tubercular
plane
■ -. Lt^l lateral line
Fig. 1220. — Surface lines of the front of the thorax and abdomen.
the right and left hypochondriac. The central region of the middle zone is the
imibilical, and the two lateral regions the right and left lumbar. The middle region
of the lower zone is the hypogastric or pubic, and the lateral are the right and left
iliac or inguinal. The middle regions, viz., epigastric, umbilical, and pubic, can each
be divided into right and left portions by the middle line. In the following descrip-
tion of the viscera the regions marked out by Addison's lines are those referred to.
SURFACE MARKINGS OF THE ABDOMEN
1317
Stomach (Fig. 1223). — The shape of the stomach is constantly undergoing altera-
tion; it is affected by the particular phase of the process of gastric digestion, by
Fig. 1221. — With the patient in the erect posture. Fig. 1222. — With the patient lying down.
Figs. 1221 and 1222. — Radiographs of a moderately distended stomach, showing the influence of posture.
(Modified from Hertz.)
the state of the surrounding viscera, and by the amount and character of its con-
tents. Its position also varies with that of the body (Figs. 1221, 1222), so
Orifice nj
vermiform proces ■•
Traivspyloric
plane
'■ V Trans tuber cwlaf
plane
Fig. 1223. — Front of abdomen, showing surface markings for liver, stomach, and great intestine.
that it is impossible to indicate it on the surface with any degree of accuracy. The
measurements given refer to a moderately filled stomach with the body in the
supine position.
1318
SURFACE ANATOMY AND SURFACE MARKINGS
The cardiac orifice is opposite the seventh left costal cartilage about 2.5 cm.
from the side of the sternum; it corresponds to the level of the tenth thoracic verte-
bra. The pyloric orifice is on the transpyloric line about 1 cm. to the right of the
middle line, or alternately 5 cm. below the seventh right sternocostal articulation;
it is at the level of the first lumbar vertebra. A curved line, convex downward and
to the left, joining these points indicates the lesser curvature. In the left lateral
line the fundus of the stomach reaches as high as the fifth interspace or the sixth
Lower lung
limit
Lower pleural
limit
Diaphragm
- - Heart contour
Stomach
^^ ^ Small intestine
_ Sigmoid
flexure
Peritoneum-
-J
Bladder
, Fig. 1224. — Topography of thoracic and abdominal viscera.
costal cartilage, a little below the apex of the heart. To indicate the greater cur-
vature a curved line is drawn from the cardiac orifice to the summit of the fundus,
thence downward and to the left, finally turning medialward to the pyloric orifice,
but passing, on its way, through the intersection of the left lateral with the trans-
pyloric line. The portion of the stomach which is in contact with the abdominal
wall can be represented roughly by a triangular area the base of which is formed by
a line drawn from the tip of the tenth left costal cartilage to the tip of the ninth
f
SURFACE MARKINGS OF THE ABDOMEN
1319
right cartilage, and the sides by two lines drawn from the end of the eighth left
costal cartilage to the ends of the base line.
A space of some clinical importance — the space of Traube — overlies the stomach
and may be thus indicated. It is semilunar in outline and lies within the following
boundaries: the lower edge of the left lung, the anterior border of the spleen, the
left costal margin and the inferior margin of the left lobe of the liver.
Duodenum (Fig. 1225). — The superior part is horizontal and extends from the
pylorus to the right lateral line; the descending part is situated medial to the
right lateral line, from the transpyloric line to a point midway between the trans-
pyloric and transtubercular lines. The horizontal part runs with a slight upward
slope from the end of the descending part to the left of the middle line; the ascending
part is vertical, and reaches the transpyloric line, where it ends in the duodeno-
jejunal flexure, about 2.5 cm. to the left of the middle line.
--■77
-'■,-4 ^ ,-'' "
f "h- / ■::■
pctncrea^s
— ^ — .' ' ^ — ' '
C:4::^9^'
A^'
"-v,.J>K^:;..
L.r
Transpyloric
plane
TYans tubercular
' plane
Fig. 1225. — Front of abdomen, showing surface markings for duodenum, pancreas, and kidneys. A A'. Plane
through joint between body and xiphoid process of sternum. B B'. Plane midway between A A' and transpyloric
plane. C C Plane midway between transpyloric and transtubercular planes.
Small Intestine. — The coils of small intestine occupy the front of the abdomen.
For the most part the coils of the jejunum are situated on the left side, i. e., in the
left lumbar and iliac regions, and in the left half of the umbilical region. The coils
of the ileum lie toward the right in the right lumbar and iliac regions, in the right
half of the umbilical region, and in the hypogastric region; a portion of the ileum
is within the pelvis. The end of the ileum, i. e., the ileocolic junction, is slightly
below and medial to the intersection of the right lateral and transtubercular lines.
Cecum and Vermiform Process. — The cecum is in the right iliac and hypo-
gastric regions; its position varies with its degree of distension, but the midpoint
of a line drawn from the right anterior superior iliac spine to the upper margin of
the symphysis pubis will mark approximately the middle of its lower border.
The position of the base of the vermiform process is indicated by a point on the
lateral line on a level with the anterior superior iliac spine.
Ascending Colon. — The ascending colon passes upward through the right
lumbar region, lateral to the right lateral line. The right colic flexure is situated in
the upper and right angle of intersection of the subcostal and right lateral lines.
Transverse Colon. — The transverse colon crosses the abdomen on the confines
of the umbilical and epigastric regions, its lower border being on a level slightly
1320 SURFACE ANATOMY AND SURFACE MARKINGS
above the umbilicus, its upper border just below the greater curvature of the
stomach.
Descending Colon. — The left colic flexure is situated in the upper left angle of
the intersection between the left lateral and transpyloric lines. The descending
colon courses down through the left lumbar region, lateral to the left lateral line,
as far as the iliac crest (see footnote p. 1181).
Hiac Colon. — The line of the iliac colon is from the end of the descending colon
to the left lateral line at the level of the anterior superior iliac spine.
Liver (Fig. 1223). — The upper limit of the right lobe of the liver, in the middle
line, is at the level of the junction between the body of the sternum and the xiphoid
process; on the right side the line must be carried upward as far as the fifth costal
cartilage in the mammary line, and then downward to reach the seventh rib at
the side of the thorax. The upper limit of the left lobe can be defined by continuing
this line downward and to the left to the sixth costal cartilage, 5 cm. from the
middle line. The lower limit can be indicated by a line drawn 1 cm. below the
lower margin of the thorax on the right side as far as the ninth costal cartilage,
thence obliquely upward to the eighth left costal cartilage, crossing the middle
line just above the transpyloric plane and finally, with a slight left convexity, to
the end of the line indicating the upper limit.
According to Birmingham the limits of the normal liver may be marked out
on the surface of the body in the following manner. Take three points: (a) 1.25
cm. below the right nipple; (6) 1.25 cm. below the tip of the tenth rib; (c) 2.5 cm.
below the left nipple. Join (a) and (c) by a line slightly convex upward; (a) and
(6) by a line slightly convex lateralward; and (b) and (c) by a line slightly convex
downward.
The fundus of the gall-bladder approaches the surface behind the anterior
end of the ninth right costal cartilage close to the lateral margin of the Rectus
abdominis.
Pancreas (Fig. 1225). — The pancreas lies in front of the second lumbar vertebra.
Its head occupies the curve of the duodenum and is therefore indicated by the same
lines as that viscus; its neck corresponds to the pylorus. Its body extends along
the transpyloric line, the bulk of it lying above this line to the tail which is in the
left hypochondriac region slightly to the left of the lateral line and above the
transpyloric.
Spleen (Figs. 1217, 1226). — To map out the spleen the tenth rib is taken as
representing its long axis; vertically it is situated between the upper border of the
ninth and the lower border of the eleventh ribs. The highest point is 4 cm. from
the middle line of the back at the level of the tip of the ninth thoracic spinous
process; the lowest point is in the midaxillary line at the level of the first lumbar
spinous process.
Kidneys (Figs. 1225, 1226).— The right kidney usually lies about 1 cm. lower
than the left, but for practical purposes similar surface markings are taken for
each.
On the front of the abdomen the upper pole lies midway between the plane of
the lower end of the body of the sternum and the transpyloric plane, 5 cm. from
the middle line. The lower pole is situated midway between the transpyloric
and intertubercular planes, 7 cm. from the middle line. The hilum is on the
transpyloric plane, 5 cm. from the middle line. Round these three points a
kidney-shaped figure 4 cm. to 5 cm. broad is drawn, two-thirds of which lies medial
to the lateral line. To indicate the position of the kidney from the back, the
parallellogram of Morris is used; two vertical lines are drawn, the first 2.5 cm.,
the second 9.5 cm. from the middle line; the parallelogram is completed by two
horizontal lines drawn respectively at the levels of the tips of the spinous process
of the eleventh thoracic and the lower border of the spinous process of the third
SURFACE MARKINGS OF THE ABDOMEN
1321
lumbar vertebra. The hilum is 5 cm. from the middle line at the level of the
spinous process of the first lumbar vertebra.
Ureters. — On the front of the abdomen, the line of the ureter runs from the
hilum of the kidney to the pubic tubercle; on the back, from the hilum vertically
downward, passing practically
through the posterior superior iliac
spine (Fig. 1226).
Vessels (Fig. 1227). — The inferior
epigastric artery can be marked out
by a line from a point midway be-
tween the anterior superior iliac
spine and the pubic symphysis to
the umbilicus. This line also indi-
cates the lateral boundary of Hessel-
bach's triangle — an area of impor-
tance in connection with inguinal
hernia ; the other boundaries are the
lateral edge of Rectus abdominis,
and the medial half of the inguinal
ligament. The line of the abdominal
aorta begins in the middle line about
4 cm. above the transpyloric line
and extends to a point 2 cm. below
and to the left of the umbilicus —
or more accurately to a point 2 cm. to the left of the middle line on a line which
passes through the highest points of the iliac crests {A A', Fig. 1227). The
Transpyloric
plane
Fig. 1226. — Back of lumbar region, showing surface markings
for kidneys, ureters, and spleen. The lower portions of the lung
and pleura are shown on the right side.
Abdominal inguinal ring
Subcutaneous inguinal
Femoral ring
Fig. 1227. — Front of abdomen, showing surface markings for arteries and inguinal canal.
point of termination of the abdominal aorta corresponds to the level of the fourth
lumbar vertebra ; a line drawn from it to a point midway between the anterior
superior iliac spine and the symphysis pubis indicates the common and external
1322 SURFACE ANATOMY AND SURFACE MARKINGS
iliac arteries. The common iliac is represented by the upper third of this Hne, the
external iliac by the remaining two-thirds.
Of the larger branches of the abdominal aorta, the celiac artery is 4 cm., the
superior mesenteric 2 cm. above the transpyloric line; the renal arteries are 2 cm.
below the same line. The inferior mesenteric artery is 4 cm. above the bifurcation
of the abdominal aorta.
Nerves. — The thoracic nerves on the anterior abdominal wall are represented by
lines continuing those of the bony ribs. The termination of the seventh nerve is
at the level of the xiphoid process, the tenth reaches the vicinity of the umbilicus,
the twelfth ends about midway between the umbilicus and the upper border of
the symphysis pubis. The first lumbar is parallel to the thoracic nerves; its ilio-
hypogastric branch becomes cutaneous above the subcutaneous inguinal ring; its
ilioinguinal branch at the ring.
SURFACE ANATOMY OF THE PERINEUM.
Skin. — In the middle line of the posterior part of the perineum and about 4 cm.
in front of the tip of the coccyx is the anal orifice. The junction of the mucous
membrane of the anal canal with the skin of the perineum is marked by a white
line which indicates also the line of contact of the external and internal Sphincters.
In the anterior part of the perineum the external genital organs are situated.
The skin covering the scrotum is rough and corrugated, but over the penis it is
smooth; extending forward from the anus on to the scrotum and penis is a median
ridge which indicates the scrotal raphe. In the female are seen the skin reduplica-
tions forming the labia majora and minora laterally, the frenulum of the labia
behind, and the prepuce of the clitoris in front; still more anteriorly is the mons
pubis.
Bones. — In the antero-lateral boundaries of the perineum, the whole outline
of the pubic arch can be readily traced ending in the ischial tuberosities. Behind
in the middle line is the tip of the coccyx.
Muscles and Ligaments. — The margin of the Glutseus maximus forms the postero-
lateral boundary, and in thin subjects, by pressing deeply, the sacrotuberous
ligament can be felt through the muscle. The only other muscles influencing
surface form are the Ischiocavernosus covering the crus penis, which lies on the side
of the pubic arch, and the Sphincter ani extemus, which, in action, closes the anal
orifice and causes a puckering of the skin around it.
SURFACE MARKINGS OF THE PERINEUM.
A line drawn transversely across in front of the ischial tuberosities divides the
perineum into a posterior or rectal, and an anterior or urogenital, triangle. This
line passes through the central point of the perineum, wliich is situated about
2.5 cm. in front of the center of the anal aperture or, in the male, midway between
the anus and the reflection of the skin on to the scrotum.
Rectum and Anal Canal. — A finger inserted through the anal orifice is grasped
by the Sphincter ani externus, passes into the region of the Sphincter ani internus,
and higher up encounters the resistance of the Puborectalis; beyond this it may
reach the lowest of the transverse rectal folds. In front, the urethral bulb and
membranous part of the urethra are first identified, and then about 4 cm. above
the anal orifice the prostate is felt; beyond this the vesiculae seminales, if enlarged,
and the fundus of the bladder, when distended, can be recognized. On either side
is the ischiorectal fossa. Behind are the anococcygeal body, the pelvic surface?
of the coccyx and lower end of the sacrum, and the sacrospinous ligaments (Fig.
1228).
SURFACE MARKINGS OF THE PERINEUM
1323
In the female the posterior wall and fornix of the vagina, and the cervix and
body of the uterus can be felt in front, wliile somewhat laterally the ovaries can
just be reached.
Ureter
Ductus deferens
\
Vxeihra
Sacrum
Rectovesical
excai'ation
Coccyx
Ejaculatory duct
Anal canal
External urethral
orifice
Fig. 1228. — Median sagittal section of male pelvis.
Male Urogenital Organs. — The corpora cavernosa penis can be followed backward
to the crura which are attached to the sides of the pubic arch. The glans penis,
covered by the prepuce, and the external urethral orifice can be examined, and the
course of the urethra traced along the under surface of the penis to the bulb M'hich
is situated immediately in front of the central point of the perineum. Through
the wall of the scrotum on either side the testis can be palpated; it lies toward
the back of the scrotum, and along its posterior border the epididymis can be felt;
passing upward along the medial side of the epididymis is the spermatic cord,
which can be traced upward to the subcutaneous inguinal ring.
By means of a sound the general topography of the urethra and bladder can
be investigated ; with the urethroscope the interior of the urethra can be illuminated
and viewed directly; with the cystoscope the interior of the bladder is in a similar
manner illuminated for visual examination. In the bladder the main points to
which attention is directed are the trigone, the torus uretericus, the plicae uretericae,
and the openings of the ureters and urethra (see Fig. 1240).
Female Urogenital Organs. — In the pudendal cleft (Fig. 1229) between the labia
minora are the openings of the vagina and inethra. In the virgin the vaginal open-
ing is partly closed by the hymen — after coitus the remains of the hymen are rep-
resented by the caruncuhie hymenales. Between the hymen and the frenulum of
the labia is the fossa navicularis, while in the groove between the hymen and the
labium minus, on either side, the small opening of the greater vestibular (Bartholin's)
gland can be seen. These glands when enlarged can be felt on either side of the
1324
SURFACE ANATOMY AND SURFACE MARKINGS
Clitorif!
Vestibule
External urethral
orifice
Vaginal orifice
Hymen
Fig. 1229. — ^External genital organs of female. The labia minora have been drawn apart.
Coccyx — T
Recto-uterine /
excavation
External uterine
orifice
Anal canal
Vesicouterine
excavation
Urethra
FiQ. 1230. — Median sagittal section of female pelvis.
SURFACE ANATOMY OF THE UPPER EXTREMITY 1325
posterior part of the vaginal orifice. By inserting a finger into the vagina the fol-
lowing structures can be examined through its wall (Fig. 1280). Behind, from
below upward, are the anal canal, the rectum, and the rectouterine excavation.
Projecting into the roof of the vagina is the vaginal portion of the cervix uteri
with the external uterine orifice; in front of and behind the cervix the anterior
and posterior vaginal fornices respectively can be examined. ^Yith the finger in the
vagina and the other hand on the abdominal wall the whole of the cervix and
body of the uterus, the uterine tubes, and the ovaries can be palpated. If a speculum
be introduced into the vagina, the walls of the passage, the vaginal portion of the
cervix, and the external uterine orifice can all be exposed for visual examination.
The external urethral orifice lies in front of the vaginal opening; the angular
gap in which it is situated between the two converging labia minora is termed the
vestibule. The urethral canal in the female is very dilatable and can be explored
with the finger. About 2.5 cm. in front of the external orifice of the urethra are
the glans and prepuce of the clitoris, and still farther forward is the mons pubis.
SURFACE ANATOMY OF THE UPPER EXTREMITY.
Skin. — The skin covering the shoulder and arm is smooth and very movable
on the underlying structures. In the axilla there are numerous hairs and many
sudoriferous and sebaceous glands. Over the medial side and front of the forearm
the skin is thin and smooth, and contains few hairs but many sudoriferous glands;
over the lateral side and back of the arm and forearm it is thicker, denser, and
contains more hairs but fewer sudoriferous glands. In the region of the olecranon
it is thick and rough, and is very loosely connected to the underlying tissue so
that it falls into transverse wrinkles when the forearm is extended. At the front
of the wrist there are three transverse furrows in the skin; they correspond respec-
tively from above downward to the positions of the styloid process of the ulna,
the wrist -joint, and the midcarpal joint.
The skin of the palm of the hand differs considerably from that of the forearm.
At the wrist it suddenly becomes hard and dense and covered with a thick layer of
epidermis; on the thenar eminence these characteristics are less marked than else-
where. In spite of its hardness and density the skin of the palm is exceedingly
sensitive and very vascular, but it is destitute of hairs and sebaceous glands. It
is tied down by fibrous bands along the lines of flexion of the digits, exhibiting
certain furrows of a permanent character. One of these, starting in front of the
wrist at the tuberositv of the navicular bone, curves around the thenar eminence
and ends on the radial border of the hand a little above the metacarpophalangeal
joint of the index finger. A second line begins at the end of the first and extends
obliquely across the palm to reach the ulnar border about the middle of the fifth
metacarpal bone. A third line begins at the ulnar border about 2.5 cm. distal to
the end of the second and extends across the heads of the fifth, fourth, and third
metacarpal bones. The proximal segments of the fingers are joined to one another
on the volar aspect by folds of skin constituting the "web" of the fingers; these
folds extend across about the level of the centers of the proximal phalanges and their
free margins are continuous with the transverse furrows at the roots of the fingers.
Since the web is confined to the volar aspect the fingers appear shorter when viewed
from in front than from behind.
Over the fingers and thumb the skin again becomes thinner, especially at the
flexures of the joints (where it is crossed by transverse furrows) and over the ter-
minal phalanges; it is disposed on numerous ridges in consequence of the arrange-
ment of the papillae in it. These ridges form, in different individuals, distinctive
and permanent patterns which can be used for purposes of identification. The
superficial fascia in the palm of the hand is made up of dense fibro-fatty tissue which
1326 SURFACE ANATOMY AND SURFACE MARKINGS
binds the skin so firmly to the palmar aponeurosis that very little movement is
permitted between the two.
On the back of the hand and fingers the subcutaneous tissue is lax, so that the
skin is freely movable on the underlying parts. Over the interphalangeal joints
the skin is very loose and is thrown into transverse wrinkles when the fingers
are extended.
Bones, — The clavicle can be felt throughout its entire length. The enlarged
sternal extremity projects above the upper margin of the sternum at the side of
the jugular notch, and from this the body of the bone can be traced lateral ward
immediately under the skin. The medial part is convex forward, but the surface
is partially obscured by the attachments of Sternocleidomastoideus and Pectoralis
major; the lateral third is concave forward and ends at the acromion of the scapula
in a slight enlargement. The clavicle is almost horizontal when the arm is lying
by the side, although in muscular subjects it may incline a little upward at its
acromial end, which is on a plane posterior to the sternal end.
The only parts of the scapula that are truly subcutaneous are the spine and
acromion, but the coracoid process, the vertebral border, the inferior angle, and to
a lesser extent the axillary border can also be readily defined. The acromion and
spine are easily recognizable throughout their entire extent, forming with the
clavicle the arch of the shoulder. The acromion forms the point of the shoulder;
it joins the clavicle at an acute angle — the acromial angle — slightly medial to, and
behind the tip of the acromion. The spine can be felt as a distinct ridge, marked
on the surface as an oblique depression which becomes less distinct and ends in a
slight dimple a little lateral to the spinous processes of the vertebrae. Below this
point the vertebral border can be traced downward and lateralward to the inferior
angle, which can be identified although covered by Latissimus dorsi. From the
inferior angle the axillary border can usually be traced upward through its thick
muscular covering, forming with its enveloping muscles the posterior fold of the
axilla. The coracoid process is situated about 2 cm. below the junction of the
intermediate and lateral thirds of the clavicle; it is covered by the anterior border
of Deltoideus, and thus lies a little lateral to the infraclavicular fossa or depression
which marks the interval between the Pectoralis major and Deltoideus.
The humerus is almost entirely surrounded by muscles, and the only parts
which are strictly subcutaneous are small portions of the medial and lateral epi-
condyles; in addition to these, however, the tubercles and a part of the head of the
bone can be felt under the skin and muscles by which they are covered. Of these,
the greater tubercle forms the most prominent bony point of the shoulder, extending
beyond the acromion; it is best recognized when the arm is lying passive by the
side, for if the arm be raised it recedes under the arch of the shoulder. The lesser
tubercle, directed forward, is medial to the greater and separated from it by the
intertubercular groove, which can be made out by deep pressure. When the arm
is abducted the lower part of the head of the humerus can be examined by pressing
deeply in the axilla. On either side of the elbow-joint and just above it are the
medial and lateral epicondyles. Of these, the former is the more prominent, but the
medial supracondylar ridge passing upward from it is much less marked than the
lateral, and as a rule is not palpable; occasionally, however, the hook-shaped supra-
condylar process (page 211) is found on this border. The position of the lateral
epicondyle is best seen during semiflexion of the forearm, and is indicated by
a depression; from it the strongly marked lateral supracondylar ridge runs
upward.
The most prominent part of the ulna, tlie olecranon, can always be identified at
the back of the elbow-joint. When the forearm is flexed the upper quadrilateral
surface is palpable, but during extension it recedes into the olecranon fossa. During
extension the upper border of the olecranon is slightly above the level of the medial
SURFACE ANATOMY OF THE UPPER EXTREMITY 1327
epicondyle and nearer to this than to the lateral; when the forearm is fully flexed
the olecranon and the epicondyles form the angles of an equilateral triangle. On
the back of the olecranon is a smooth triangular subcutaneous surface, and running
down the back of the forearm from the apex of this triangle the prominent dorsal
border of the ulna can be felt in its whole length: it has a sinuous outline, and is
situated in the middle of the back of the limb above; but below, w^here it is rounded
off, it can be traced to the small subcutaneous surface of the styloid process on the
medial side of the wrist. The styloid process forms a prominent tubercle continuous
above with the dorsal border and ending below in a blunt apex at the level of the
wrist-joint; it is most evident when the hand is in a position midway between
supination and pronation. When the forearm is pronated another prominence,
the head of the ulna, appears behind and above the styloid process.
Below the lateral epicondyle of the humerus a portion of the head of the radius
is palpable; its position is indicated on the surface by a little dimple, which is best
seen when the arm is extended. If the finger be placed in this dimple and the
semiflexed forearm be alternately pronated and supinated the head of the radius
will be felt distinctly, rotating in the radial notch. The upper half of the body of
the bone is obscured by muscles; the lower half, though not subcutaneous, can be
readily examined, and if traced downward is found to end in a lozenge-shaped con-
vex surface on the lateral side of the base of the styloid process; this is the only
subcutaneous part of the bone, and from its lower end the apex of the styloid process
bends medialward toward the wrist. About the middle of the dorsal surface of
the lower end of the radius is the dorsal radial tubercle, best perceived when the
wrist is slightly flexed; it forms the lateral boundary of the oblique groove for the
tendon of Extensor pollicis longus.
On the front of the wrist are two subcutaneous eminences, one, on the radial
side, the larger and flatter, produced by the tuberosity of the navicular and the ridge
on the greater multangular; the other, on the ulnar side, by the pisiform. The tuber-
osity of the navicular is distal and medial to the styloid process of the radius, and
is most clearly visible when the wrist-joint is extended; the ridge on the greater
midtangular is about 1 cm. distal to it. The pisiform is about 1 cm. distal to the
lower end of the ulna and just distal to the level of the styloid process of the radius;
it is crossed by the uppermost crease which separates the front of the forearm from
the palm of the hand. The rest of the volar surface of the bony carpus is covered
by tendons and the transverse carpal ligament, and is entirely concealed, with
the exception of the hamulus of the hamate bone, which, however, is difficult to
define. On the dorsal surface of the carpus only the triangular bone can be clearly
made out.
Distal to the carpus the dorsal surfaces of the metacarpal bones, covered by the
Extensor tendons, except the fifth, are visible only in very thin hands; the dorsal
surface of the fifth is, however, subcutaneous throughout almost its whole length.
Slightly lateral to the middle line of the hand is a prominence, frequently well-
marked, but occasionally indistinct, formed by the styloid process of the third
metacarpal bone; it is situated about 4 cm. distal to the dorsal radial tubercle.
The heads of the metacarpal bones can be plainly seen and felt, rounded in contour
and standing out in bold relief under the skin when the fist is clenched; the head
of the third is the most prominent. In the palm of the hand the metacarpal bones
are covered by muscles, tendons, and aponeuroses, so that only their heads can be
distinguished. The base of the metacarpal bone of the thumb, however, is promi-
nent dorsally, distal to the styloid process of the radius; the body of the bone is
easily palpable, ending at the head in a flattened prominence, in front of which
are the sesamoid bonea.
The enlarged ends of the phalanges can be easily felt. When the digits are
bent the proximal phalanges form prominences, which in the joints between the
1328 SURFACE ANATOMY AND SURFACE MARKINGS
first and second phalanges are slightly hollow, but flattened and square-shaped in
those between the second and third.
Articulations. — The sternoclavicular joint is subcutaneous, and its position is
indicated by the enlarged sternal extremity of the clavicle, lateral to the long
cord-like sternal head of Sternocleidomastoideus. If this muscle be relaxed a
depression between the end of the clavicle and the sternum can be felt, defining
the exact position of the joint.
The position of the acromioclavicular joint can generally be ascertained by
determining the slightly enlarged acromial end of the clavicle which projects above
the level of the acromion; sometimes this enlargement is so considerable as to
form a rounded eminence.
The shoulder- joint is deeply seated and cannot be palpated. If the forearm
be slightly flexed a curved crease or fold with its convexity downward is seen in
front of the elbow, extending from one epicondyle to the other; the elbow-joint
is slightly distal to the center of the fold. The position of the radiohumeral joint
can be ascertained by feeling for a slight groove or depression between the head
of the radius and the capitulum of the humerus, at the back of the elbow-joint.
The position of Ihe proximal radioulnar joint is marked on the surface at the
back of the elbow by the dimple which indicates the position of the head of the
radius. The site of the distal radioulnar joint can be defined by feeling for the
slight groove at the back of the wrist between the prominent head of the ulna
and the lower end of the radius, when the forearm is in a state of almost complete
pronation.
Of the three transverse skin furrows on the front of the wrist, the middle corre-
sponds fairly accurately with the wrist-joint, while the most distal indicates the
position of the midcarpal articulation.
The metacarpophalangeal and interphalangeal joints are readily available for
surface examination; the former are situated just distal to the prominences of the
knuckles, the latter are sufficiently indicated by the furrows on the volar, and the
wrinkles on the dorsal surfaces.
Muscles (Figs. 1194, 1231, 1232). — The anterior border of the Trapezius presents as
a slight ridge running downward and forward from the superior nuchal line of the
occipital bone to the junction of the intermediate and lateral thirds of the clavicle.
The inferior border of the muscle forms an undulating ridge passing downward
and medialward from the root of the spine of the scapula to the Spinous process
of the twelfth thoracic vertebra.
The lateral border of the Latissimus dorsi (Fig. 1215) may be traced, when the
muscle is in action, as a rounded edge starting from the iliac crest and slanting
obliquely forward and upward to the axilla, where it takes part with the Teres
major in forming the posterior axillary fold.
The Pectoralis major (Fig. 1219) conceals a considerable part of the thoracic wall
in front. Its sternal origin presents a border which bounds, and determines the
width of the sternal furrow. The upper margin is generally well-marked medially
and forms the medial boundary of a triangular depression, the infraclavicular fossa,
which separates the Pectoralis major from the Deltoideus; it gradually becomes
less" marked as it approaches the tendon of insertion and is closely blended with
the Deltoideus. The lower border of Pectoralis major forms the rounded anterior
axillary fold. Occasionally a gap is visible between the clavicular and sternal parts
of the muscle.
When the arm is raised the lowest slip of origin of Pectoralis minor produces a
fulness just below the anterior axillary fold and serves to break the sharp outline
of the lower border of Pectoralis major.
The origin of the Serratus anterior (Figs. 1215, 1219) causes a very characteristic
surface marking. When the arm is abducted the lower five or six serrations form
SURFACE ANATOMY OF THE UPPER EXTREMITY
1329
a zigzag line witli a general convexity forward; when the arm is by the side the
highest visible serration is that attached to the fifth rib.
The Deltoideus with the prominence of the upper end of the humerus produces
the rounded contour of the shoulder; it is rounded and fuller in front than behind,
where it presents a somewhat flattened form. Above, its anterior border presents
a slightly curved eminence which forms the lateral boundary of the infracla^dcular
fossa; below, it is closely united with the Pectoralis major. Its posterior border
is thin, flattened, and scarcely marked above, but is thicker and more prominent
below. The insertion of Deltoideus is marked by a depression on the lateral side
of the middle of the arm.
Flex. carj). rad.
AM. j)fiU Ion;/.
Ext. jidU. brev.
Lateral group of
a nt ibrach i' 1 1 mi(s<-lei!
I Brachialts
I I Biceps brachii
I I
t i
Flex. carp, ulnaris
Palm art's longus
Medial qroxtp of ,' ! „ . , , • /
antihraclual mLcles { / Tnccpshraclu
Anticubital fossa Medial epicondyle
Coracohrachia lis
Axilla
Pectoralis major
Serratus anterior
Fig. 1231. — Front of right upper extremity.
Of the scapular muscles the only one which influences surface form is the Teres
major; it assists the Latissimus dorsi in forming the thick, rounded, posterior
axillary fold.
When the arm is raised the Coracobrachialis reveals itself as a narrow elevation
emerging from under cover of the anterior axillary fold and running medial to the
body of the humerus.
Deltoideus
Medial eminence
Biceps brachii
Lateral eminence
Triceps hrnchii
Medial epicondyle
Olecranon
Bead of ulna
Ext. carp, tdnaris
I Flex. carp, ulnaris
.\rkconjBus
Fig. 1232. — Back of right upper extremity.
On the front and medial aspects of the arm is the prominence of the Biceps
brachii, bounded on either side by an intermuscular depression. It determines the
contour of the front of the arm and extends from the anterior axillary fold to the
bend of the elbow; its upper tendons are concealed by the Pectoralis major and
Deltoideus, and its lower tendon sinks into the anticubital fossa. When the muscle
is fully contracted it presents a globular form, and the lacertus fibrosus attached
84
I
I
1330 SURFACE ANATOMY AND SURFACE MARKINGS
to its tendon of insertion becomes prominent as a sharp ridge running downward
and medial ward.
On either side of the Biceps brachii at the lower part of the arm the Brachialis
is discernible. Laterally it forms a narrow eminence extending some distance up
the arm; medially it exhibits only a little fulness aboAe the elbow.
On the back of the arm the long head of the Triceps brachii may be seen as a
longitudinal eminence, emerging from under cover of Deltoideus and gradually
passing into the flattened plane of the tendon of the muscle at the lower part of
the back of the arm. When the muscle is in action the medial and lateral heads |
become prominent.
On the front of the elbow are two muscular elevations, one on either side, sep-
arate above but converging below so as to form the medial and lateral boundaries
of the anticubital fossa. The medial elevation consists of the Pronator teres and
the Flexors, and forms a fusiform mass, pointed above at the medial epicondyle
and gradually tapering off below. The Pronator teres is the most lateral of the
group, while the Flexor carpi radialis, lying to its medial side, is the most prominent
and may be traced downward to its tendon, which is situated nearer to the radial
than to the ulnar border of the front of the wrist and medial to the radial artery. 1
The Palmaris longus presents no surface marking above, but below, its tendon T
stands out when the muscle is in action as a sharp, tense cord in front of the middle I
of the wrist. The Flexor digitorum sublimis does not directly influence surface |
form; the position of its four tendons on the front of the lower part of the forearm
is indicated by an elongated depression between the tendons of Palmaris longus
and Flexor carpi ulnaris. The Flexor carpi ulnaris determines the contour of the
medial border of the forearm, and is separated from the Extensor group of muscles
by the ulnar furrow produced by the subcutaneous dorsal border of the ulna; its
tendon is evident along the ulnar border of the lower part of the forearm, and is
most marked when the hand is flexed and adducted.
The elevation forming the lateral side of the anticubital fossa consists of the
Brachioradialis, the Extensors and the Supinator; it occupies the lateral and a
considerable part of the dorsal surface of the forearm in the region of the elbow,
and forms a fusiform mass which is altogether on a higher level than that produced
by the medial elevation. Its apex is between the Triceps brachii and Brachialis
some distance above the elbow-joint; it acquires its greatest breadth opposite the
lateral epicondyle, and below this shades off into a flattened surface. About the
middle of the forearm it divides into two diverging longitudinal eminences. The
lateral eminence consists of the Brachioradialis and the Extensores carpi radiales
longus and brevis, and descends from the lateral supracondylar ridge in the direction
of the styloid process of the radius. The medial eminence comprises the Extensor
digitorum communis, Extensor digiti quinti proprius, and the Extensor carpi ulnaris;
it begins at the lateral epicondyle of the humerus as a tapering mass which is sep-
arated above from the Anconseus by a well-marked furrow, and below from the
Pronator teres and Flexor group by the ulnar furrow. The medial border of the
Brachioradialis starts as a rounded elevation above the lateral epicondyle; lower
down the muscle forms a prominent mass on the radial side of the upper part of
the forearm; below it tapers to its tendon, which may be traced to the styloid
process of the radius. The Anconseus presents as a triangular slightly elevated
area, immediately lateral to the subcutaneous surface of the olecranon and differ-
entiated from the Extensor group by an oblique depression; the upper angle of
the triangle is at the dimple cfver the lateral epicondyle.
At the lower part of the back of the forearm in the interval between the two
diverging eminences is an oblique elongated swelling; full above but flattened
and partially subdivided below; it is caused by the Abductor pollicis longus
and the Extensor pollicis brevis. It crosses the dorsal and lateral surfaces of
SURFACE MARKINGS OF THE UPPER EXTREMITY 1331
the radius to the radial side of the wrist-joint, whence it is continued on to
the dorsal surface of the thumb as a ridge best marked when the thumb is
extended.
The tendons of most of the Extensor muscles can be seen and felt on the back
of the wrist. Laterally' is the oblique ridge produced by the Extensor pollicis
longus. The Extensor carpi radialis longus is scarcely palpable, but the Extensor
carpi radialis brevis can be identified as a vertical ridge emerging from under the
ulnar border of the tendon of the Extensor pollicis longus when the wrist is extended,
^ledial to this the Extensor tendons of the fingers can be felt, the Extensor digiti
quinti proprius being separated from the tendons of the Extensor digitorum
communis by a slight furrow.
The muscles of the hand are principally concerned, as regards surface form, in
producing the thenar and hypothenar eminences, and cannot be individually dis-
tinguished; the thenar eminence, on the radial side, is larger and rounder than the
hypothenar, which is a long narrow elevation along the ulnar side of the palm.
When the Palmaris brevis is in action it produces a wrinkling of the skin over the
hypothenar eminence and a dimple on the ulnar border. On the back of the hand
the Interossei dorsales give rise to elongated swellings between the metacarpal
bones; the first forms a prominent fusiform bulging when the thumb is adducted,
the others are not so marked.
Arteries. — Above the middle of the clavicle the pulsation of the subclavian artery
can be detected by pressing downward, backward, and medialward against the
first rib. The pulsation of the axillary artery as it crosses the second rib can be
felt below the middle of the clavicle just medial to the coracoid process; along the
lateral wall of the axilla the course of the artery can be easily followed close to the
medial border of Coracobrachialis. The brachial artery can be recognized in practi-
cally the whole of its extent, along the medial margin of the Biceps; in the upper
two-thirds of the arm it lies medial to the humerus, but in the lower third is more
directly on the front of the bone. Over the lower end of the radius, between the
styloid process and Flexor carpi radialis, a portion of the radial artery is superficial
and is used clinically for observations on the pulse.
Veins. — The superficial veins of the upper extremity are easily rendered visible
by compressing the proximal trunks; their arrangement is described on pages 600
to 062.
Nerves. — The uppermost trunks of the brachial plexus are palpable for a short
distance above the clavicle as they emerge from under the lateral border of Sterno-
cleidomastoideus ; the larger nerves derived from the plexus can be rolled imder the
finger against the lateral axillary wall but cannot be identified. The ulnar nerve
can be detected in the groove behind the medial epicondyle of the humerus.
SURFACE MARKINGS OF THE UPPER EXTREMITY.
Bony Landmarks. — The bony landmarks as described above are so readily avail-
able for surface recognition that no special measurements are required to indicate
them. It may be noted, however, that the medial angle of the scapula is applied
to the second rib, while the inferior angle lies against the seventh. The intertuber-
cular groove of the humerus is vertically below the acromioclavicular joint when
the arm hangs by the side with the palm of the hand forward.
Articulations. — The acromioclavicular joint is situated in a plane passing sagit-
tally through the middle line of the front of the arm. The line of the elbow-joint
is not straight; the radiohumeral portion is practically at right angles to the long
axis of the humerus and is situated about 2 cm. distal to the lateral epicondyle;
the ulnohumeral portion is oblique, and its medial end is about 2.5 cm. distal to the
medial epicondyle. The position of the wrist-joint can be indicated by drawing a
1332
SURFACE ANATOMY AND SURFACE MARKINGS
curved line, with its convexity upward, between the styloid processes of the radius
and ulna; the summit of the convexity is about 1 cm. above the center of a straight
line joining the two processes.
Sheaths of terminal
parts of Flexorea
digitorum
Muscles of thenar
eminence
Sheath of Flexor
follicis longus
Sheath of Flexor carpi
radiaiis
Muscles of hypo-
thenar eminence
Gonvmon sheath of
Fkxores digitorum,
sublimis and
profundus
Flexor carpi ulnaris
FiQ. 1233. — The mucous sheatha of the tendons on the front of the wrist and digits.
Muscles. — ^The only muscles of the upper extremity which occasionally require
definition by surface lines are the Trapezius, the Latissimus dorsi, and the Pectorales
major and minor. The antero-superior border of Trapezius is indicated by a line
from the superior nuchal line about 3 cm. lateral to the external occipital protuber-
ance to the junction of the intermediate and lateral thirds of the clavicle; the line
of the lower border extends from the spinous process of the twelfth thoracic vertebra
to the vertebral border of the scapula at the root of the spine. The upper border
SURFACE MARKINGS OF THE UPPER EXTREMITY
1333
of Latissimus dorsi is almost horizontal, running from the spinous process of the
seventh thoracic vertebra to the inferior angle of the scapula and thence somewhat
obliquely to the intertubercular sulcus of the humerus; the lower border corresponds
roughly to a line drawn from the iliac crest about 2 cm. from the lateral margin of
Abd. poll. long.
Ext. carp. racl. long.
Ext carp. rad. brev.
Fio. 1-34. — The mucous sheaths of the tendons on the back of the wrist.
the Sacrospinalis to the intertubercular sulcus. The upper margin of Pectoralis
major extends from the middle of the clavicle to the surgical neck of the humerus;
its lower border is practically in the line of the fifth rib and reaches from the fifth
costochondral junction to the middle of the anterior border of Deltoideus. The
two lines indicating the borders of Pectoralis minor begin at the coracoid process
1334
SURFACE ANATOMY AND SURFACE MARKINGS
of the scapula and extend to the third and fifth ribs respectively, just lateral to the
corresponding costal cartilages. On the front of the elbow-joint a triangular space
— the anticubital fossa — is mapped out for convenience of reference. The base of
the triangle is a line joining the medial and lateral epicondyles, while the sides are
formed respectively by the salient margins of the Brachioradialis and Pronator
teres.
Fig. 1235. — Front of right upper extremity, showing surface markings for bones, arteries, and nerves.
Mucous Sheaths. — On the volar surfaces of the wrist and hand the mucous
sheaths of the Flexor tendons (Fig. 1233) can be indicated as follows. The sheath
for Flexor pollicis longus extends from about 3 cm. above the upper edge of the
transverse carpal ligament to the terminal phalanx of the thumb. The common
sheath for the Flexores digitorum reaches about 3.5 to 4 cm. above the upper edge
of the transverse carpal ligament and extends on the palm of the hand to about
the level of the centers of the metacarpal bones. The sheath for the tendons to the
little finger is continued from the common sheath to the base of the terminal phalanx
of this finger; the sheaths for the tendons of the other fingers are separated from
the common sheath by an interval; they begin opposite the necks of the meta-
carpal bones and extend to the terminal phalanges. The mucous sheaths of the
Extensor tendons are shown in Fig. 1234 (see also page 459).
Fig. 1236. — Back of right upper extremity, showing surface markings for bones and nerves.
Arteries (Fig. 1235). — The course of the axillary artery can be marked out by
abducting the arm to a right angle and drawing a line from the middle of the
clavicle to the point where the tendon of the Pectoralis major crosses the promi-
nence of the Coracobrachialis. Of the branches of the axillary artery, the origin
of the thoracoacromial corresponds to the point where the artery crosses the
upper border of Pectoralis minor; the lateral thoracic takes practically the line of
the lower border of Pectoralis minor; the subscapular is sufficiently indicated by
SURFACE MARKINGS OF THE UPPER EXTREMITY
1335
the axillary border of the scapula; the scapular circumflex is given off the sub-
scapular opposite the midpoint of a line joinino; the tip of the acromion to the
lower edge of the deltoid tuberosity, while the humeral circumflex arteries arise
from the axillary about 2 cm. above this. The position of the brachial artery is
marked by a line drawn from the junction of the anterior and middle thirds of the
distance between the anterior and posterior axillary folds to a point midway
between the epicondyles of the humerus and continued distally for 2.5 cm., at
v^'hich point the artery bifurcates. With regard to the branches of the brachial
arter}' — the profunda crosses the back of the humerus at the level of the insertion
of Deltoideus; the nutrient is given off opposite the middle of the body of the
humerus; a line from this point to the back of the medial condyle represents
the superior ulnar collateral; the inferior ulnar collateral is given off about 5 cm.
above the fold of the elbow-joint and runs directly medialward.
The position of the radial artery in the forearm is represented by a line from the
lateral margin of the Biceps tendon in the center of the anticubital fossa to the
medial side of the front of the styloid process of the radius when the limb is
in the position of supination. The situation of the distal portion of the artery
is indicated by continuing this line
around the radial side of the wrist
to the proximal end of the first inter-
metacarpal space.
On account of the curved direction
of the ulnar artery, two lines are re-
quired to indicate its course; one is
drawn from the front of the medial
epicondyle to the radial side of the
pisiform bone; the lower two-thirds
of this line represents two-thirds of
the artery; the upper third is repre-
sented by a second line from the center
of the hollow in front of the elbow-
joint to the junction of the upper and
middle thirds of the first line.
The superficial volar arch (Fig. 1237)
can be indicated by a line starting
from the radial side of the pisiform
bone and curving distalward and
lateralward as far as the base of the
thumb, with its convexity toward the
fingers. The summit of the arch is
usually on a level with the ulnar
border of the outstretched thumb.
The deep volar arch is practically
transverse, and is situated about 1
cm. nearer to the carpus.
Nerves (Figs. 1235, 1236).— In the
arm the line of the median nerve is
practically the same as that for the
brachial artery; at the bend of the
elbov*^ the nerve is medial to the
artery. The course of the nerve in the forearm is marked b\
from a point just medial to the center of one joining the epicondyles, and ex-
tending to the lateral margin of the tendon of Palmaris longus at the wrist.
The ulnar nerve follows the line of the brachial artery in the upper half of the
Radial artery --
Ulnar
artery
Fig. 1237. — Palm of left hand, showing position of skin
creases and bones, and surface markings for the volar
arches.
a line starting
1336 SURFACE ANATOMY AND SURFACE MARKINGS
arm, but at the middle of the arm it diverges and descends to the back of the
medial epicondyle. In the forearm it is represented by a line from the front
of the medial epicondyle to the radial side of the pisiform bone.
The course of the radial nerve can be indicated by a line from just below the
posterior axillary fold, to the lateral side of the humerus at the junction of its
middle and lower thirds; thence it passes vertically downward on the front of
the arm to the level of the lateral epicondyle. The course of the superficial
radial nerve is represented by a continuation of this line downward to the junction
of the middle and lower thirds of the radial artery; it then crosses the radius and
runs distalward to the dorsum of the base of the first metacarpal bone.
The axillary nerve crosses the humerus about 2 cm. above the center of a line
joining the tip of the acromion to the lower edge of the deltoid tuberosity.
SURFACE ANATOMY OF THE LOWER EXTREMITY.
Skin. — The skin of the thigh, especially in the hollow of the groin and on the
medial side, is thin, smooth and elastic, and contains few hairs except on the neigh-
borhood of the pubis. Laterally it is thicker and the hairs are more numerous.
The junction of the skin of the thigh with that on the front of the abdomen is
marked by a well-defined furrow which indicates the site of the inguinal ligament;
the furrow presents a general convexity downward, but its medial half, which is
the better marked, is nearly straight. The skin over the buttock is fairly thick
and is characterized by its low sensibility and slight vascularity; as a rule it is
destitute of conspicuous hairs except toward the post-anal furrow, where in some
males they are abundantly developed. An almost transverse fold — the gluteal
fold — crosses the lower part of the buttock; it practically bisects the lower margin
of the Glutjeus maximus and is most evident during extension of the hip-joint.
The skin over the front of the knee is covered by thickened epidermis; it is loose
and thrown into transverse wrinkles when the leg is extended. The skin of the leg
is thin, especially on the medial side, and is covered with numerous large hairs.
On the dorsum of the foot the skin is thin, loosely connected to subjacent parts,
and contains few hairs, on the plantar surface, and especially over the heel, the
epidermis is of great thickness, and here, as in the palm of the hand, there are
neither hairs nor sebaceous glands.
Bones. — The hip bones are largely covered with muscles, so that only at a few
points do they approach the surface. In front the anterior superior iliac spine is
easily recognized, and in thin subjects stands out as a prominence at the lateral
end of the fold of the groin; in fat subjects its position is indicated by an oblique
depression, at the bottom of which the bony process can be felt. Proceeding
upward and backward from this process the sinuously curved iliac crest can be
traced to the posterior superior iliac spine, the site of which is indicated by a slight
depression; on the outer lip of the crest, about 5 cm. behind the anterior superior
spine, is the prominent iliac tubercle. In thin subjects the pubic tubercle is very
apparent, but in the obese it is obscured by the pubic fat; it can, however, be
detected by following up the tendon of origin of Adductor longus. Another part
of the bony pelvis which is accessible to touch is the ischial tuberosity, situated
beneath the Glutseus maximus, and, when the hip is flexed, easily felt, as it is then
uncovered by muscle.
The femur is enveloped by muscles, so that in fairly muscular subjects the only
accessible parts are the lateral surface of the greater trochanter and the lower
expanded end of the bone. The site of the greater trochanter is generally indicated
by a depression, owing to the thickness of the Glutsei medius and minimus which
project above it; when, however, the thigh is flexed, and especially if it be crossed
over the opposite one, the trochanter produces a blunt eminence on the surface.
SURFACE ANATOMY OF THE LOWER EXTREMITY 1337
The lateral condyle is more easily felt than the medial; both epicondyles can be
readily identified, and at the upper part of the medial condyle the sharp adductor
tubercle can be recognized without difficulty. When the knee is flexed a portion
of the patellar surface is uncovered and is palpable.
The anterior surface of the patella is subcutaneous. When the knee is extended
the medial border of the bone is a little more prominent than the lateral, and if
the Quadriceps femoris be relaxed the bone can be moved from side to side. When
the joint is flexed the patella recedes into the hollow between the condyles of the
femur and the upper end of the tibia, and becomes firmly applied to the femur.
A considerable portion of the tibia is subcutaneous. At the upper end the con-
dyles can be felt just below the knee; the medial condyle is broad and smooth,
and merges into the subcutaneous surface of the body below; the lateral is narrower
and more prominent, and on it, about midway between the apex of the patella
and the head of' the fibula, is the tubercle for the attachment of the iliotibial band.
In front of the upper end of the bone, between the condyles, is an oval eminence,
the tuberosity, which is continuous below with the anterior crest of the bone. This
crest can be identified in the upper two-thirds of its extent as a flexuous ridge,
but in the lower third it disappears and the bone is concealed by the tendons of
the muscles on the front of the leg. Medial to the anterior crest is the broad
surface, slightly encroached on by muscles in front and behind. The medial
malleolus forms a broad prominence, situated at a higher level and somewhat
farther forward than the lateral malleolus; it overhangs the medial border of the
arch of the foot; its anterior border is nearly straight, its posterior presents a sharp
edge w^hich forms the medial margin of the groove for the tendon of Tibialis
posterior.
The only subcutaneous parts of the fibula are the head, the lower part of the
body, and the lateral malleolus. The head lies behind and lateral to the lateral
condyle of the tibia, and presents as a small prominent pyramidal eminence slightly
above the level of the tibial tuberosity; its position can be readily located by
following downward the tendon of Biceps femoris. The lateral malleolus is a
narrow elongated prominence, from which the lower third or half of the lateral
surface of the body of the bone can be traced upward.
On the dorsum of the tarsus the individual bones cannot be distinguished, with
the exception of the head of the talus, which forms a rounded projection in front
of the ankle-joint when the foot is forcibly extended. The whole dorsal surface of
the foot has a smooth convex outline, the summit of which is the ridge formed by
the head of the talus, the navicular, the second cuneiform, and the second meta-
tarsal bone; from this it inclines gradually lateralward, and rapidly medialward.
On the medial side of the foot the medial process of the tuberosity of the calcaneus
and the ridge separating the posterior from the medial surface of the bone are
distinguishable; in front of this, and below the medial malleolus, is the susten-
taculum tali. The tuberosity of the navicular is palpable about 2.5 to 3 cm. in
front of the medial malleolus.
Farther forward, the ridge formed by the base of the first metatarsal bone can
be obscurely felt, and from this the body of the bone can be traced to the expanded
head; beneath the base of the first phalanx is the medial sesamoid bone. On the
lateral side of the foot the most posterior bony point is the lateral process of
the tuberosity of the calcaneus, with the ridge separating the posterior from the
lateral surface of the bone. In front of this the greater part of the lateral sur-
face of the calcaneus is subcutaneous; on it, below and in front of the lateral
malleolus, the trochlear process, when present, can be felt. Farther forward the
base of the fifth metatarsal bone is prominent, and from it the body and expanded
head can be traced.
As in the case of the metacarpals, the dorsal surfaces of the metatarsal bones
1338
SURFACE ANATOMY AND SURFACE MARKINGS
Tensor fasciae latce
Femoral triangle
Sartor iiLS
are easilv defined, although their heads do not form prominences; the plantar
surfaces are obscured by muscles. The phalanges in their whole extent are readily
palpable. i ^ j
Articulations.— The hip-joint is deepl\- seated and cannot be palpated.
The inter^-al between the tibia and femur can always be easil}- felt; if the knee-
joint be extended this interval is on a higher level than the apex of the patella,
but if the joint be slightly flexed it is directly behind the apex. When the knee
is semiflexed, the medial borders of the patella and of the medial condyle of
the femur, and the upper border of the medial condyle of the tibia, bound a tri-
angular depressed area which indicates the position of the joint.
The ankle-joint can be felt on
either side of the Extensor tendons,
and during extension of the joint
the superior articular surface of
the talus presents below the ante-
rior border of the lower end of the
tibia.
Muscles. — Of the muscles of the
thigh, those of the anterior femoral
region (Fig. 1238) contribute largely
to surface form. The Tensor fasciae
latse produces a broad elevation
immediately below the anterior
part of the iliac crest and behind
the anterior superior iliac spine;
from its lower border a groove
caused by the iliotibial band ex-
tends downward to the lateral side
of the knee-joint. The upper por-
tion of Sartorius constitutes the
lateral boundary of the femoral
triangle, and, when the muscle is
in action, forms a prominent
oblique ridge which is continued
below into a flattened plane and
then gradually merges into a gen-
eral fulness on the medial side of
the knee-joint. When the Sarto-
rius is not in action, a depression
exists between the Quadriceps
femoris and the Adductors, and
extends obliquely downward and
medialward from the apex of the
femoral triangle to the side of the
knee. In the angle formed by the divergence of Sartorius and Tensor fascine
latae, just below the anterior superior iliac spine, the Rectus femoris appears, and
in a muscular subject its borders can be clearly defined when the muscle is in action.
The Vastus lateralis forms a long flattened plane traversed by the groove of the
iliotibial band. The Vastus medialis gives rise to a considerable prominence on
the medial side of the lower half of the thigh; this prominence increases toward
the knee and ends somewhat abruptly with a full curved outline. The Vastus
intermedins is completely hidden. The Adductores cannot be difi'erentiated from
one another, with the exception of the upper tendon of Adductor longus and
the lower tendon of Adductor magnus. When the Adductor longus is in action its
Quadriceps femoris
Adductores
P.
Patella — -,
»
\
Tuberosity of tibia -
Fig. 1238. — Front and medial aspect of right thigh.
SURFACE ANATOMY OF THE LOWER EXTREMITY
1339
upper tendon stands out as
a prominent ridge running
obliquely downward and
lateralward from the neigh-
borhood of the pubic tu-
bercle, and forming the me-
dial border of the femoral
triangle. The lower tendon
of Adductor magnus can be
distinctly felt as a short
ridge extending downward
between the Sartorius and
Vastus medialis to the ad-
ductor tubercle. The ad-
ductores fill in the triangular
space at the upper part of
the thigh, between the femur
and the pelvis, and to them
is due the contour of the
medial border of the thigh,
the Gracilis contributing
largely to the smoothness
of the outline.
The Glutaeus maximus (Fig.
1239) forms the full rounded
outline of the buttock; it is
more prominent behind,
compressed in front, and
ends at its tendinous inser-
tion in a depression imme-
diately behind the greater
trochanter; its lower border
crosses the gluteal fold
obliquely downward and
lateralward. The upper is
part of GlutiTeus medius
visible, but its lower part
with Glutanis minimus and
the external rotators are
completely hidden. From
beneath the lower margin
of Glutjeus maximus the
hamstrings appear; at first
they are narrow and not
well-defined, but as they
descend they become more
prominent and eventually
divide into two well-marked
ridges fornjed by their ten-
dons; these constitute the
upper boundaries of the
popliteal fossa. The tendon
of Biceps femoris is a thick
cord running to the head of
Glutceus
maximus
Tensor fasciae.
latcB
Hamstrings
-O
Gluteal fold
Biceps femoris-
■ Semimembranosus
Semitendinosus
Popliteal fossa
O-
■ Gastrocnemius
Soleus-
Perona loncjus and brcvis
■ Medial malleolus
^
•^^^m
-Tendo calcaneus
FlQ
Lateral malleolus
1239. — Back of left lower extremity.
1340
SURFACE ANATOMY AND SURFACE MARKINGS
Quadriceps
fcmoris
Biceps femoris.
Popliteal fossa ■
— Patella
I
Tuberosity
of tibia
Gastrocnemius
Peronceu."
longus
- Tibialis anterior
the fibula; the tendons of the Semimembranosus and Semitendinosus as the}^ run
medialward to the tibia are separated by a slight furrow; the Semitendinosus is
the more medial, and can be felt in certain positions of the limb as a sharp cord,
while the Semimembranosus is thick and rounded. The Gracilis is situated a little
in front of them.
The Tibialis anterior (Fig. 1240) presents a fusiform enlargement at the lateral
side of the tibia and projects beyond the anterior crest of the bone; its tendon can
be traced on the front of the tibia and ankle-joint and thence along the medial side
of the foot to the base of the first metatarsal bone. The fleshy fibers of Peronaeus
longus are strongly marked at the upper part of the lateral side of the leg; it is
separated by furrows from Extensor
digitorum longus in front and Soleus
behind. Below, the fleshy fibers end
abruptly in a tendon which overlaps
the more flattened elevation of Pero-
naeus brevis; below the lateral mal-
leolus the tendon of Peronaeus brevis
is the more marked.
On the dorsum of the foot (Fig.
1241) the tendons emerging from
beneath the transverse and cruciate
crural ligaments spread out and
can be distinguished as follows:
the most medial and largest is
Tibialis anterior, the next is Ex-
tensor hallucis proprius, then Ex-
tensor digitorum longus dividing
into four tendons, to the second,
third, fourth, and fifth toes, and
lastly Feronai'us tertius. The Ex-
tensor digitorum brevis produces a
rounded outline on the dorsum of
the foot arid a fulness in front of the
lateral malleolus. The Interossei
dorsales bulge between the metatar-
sal bones.
At the back of the knee is the
popliteal fossa, bounded above by
the tendons of the hamstrings and
below by the Gastrocnemius. Below
this fossa is the prominent fleshy
mass of the calf of the leg produced
by Gastrocnemius and Soleus (Fig.
1 239) . When these muscles are in action the borders of Gastrocnemius form two well-
defined curved lines which converge to the tendocalcaneus ; the medial border is the
more prominent. At the same time the edges of Soleus can be seen forming, on
either side of Gastrocnemius, curved eminences, of which the lateral is the longer.
The fleshy mass of the calf ends somewhat abruptly in the tendocalcaneus, which
tapers in the upper three-fourths of its extent but widens out slightly below.
Behind the medial border of the lower part of the tibia (Fig. 1242) a well-defined
ridge is produced by the tendon of Tibialis posterior during contraction of the
muscle.
On the sole of the foot the Abductor digiti quinti forms a narrow rounded eleva-
tion on the lateral side, and the Abductor hallucis a lesser elevation on the medial
Lateral
malleolus
\
Fig. 1240. — Lateral aspect of right leg.
I
SURFACE ANATOMY OF THE LOWER EXTREMITY
1341
side. The Flexor digitonun brevis, bound down by the plantar aponeurosis, is not
very apparent; it produces a flattened form, and the thickened skin underlying
it is thrown into numerous wrinkles.
Tibialis anterior
Extensor dig, longtis
Ext. hall, long,
Ext. dig. brevis
Tendo calcaneus
PeroncBus longus
peronceus hrevis Peronwus tertius
Fig. 1241. — The mucous sheaths of the tendons around the ankle. Lateral aspect.
Arteries. — The femoral artery as it crosses the brim of the pelvis is readily felt;
in its course down the thigh its pulsation becomes gradually more difficult of recog-
nition. When the knee is flexed the pulsation of the popliteal artery can easily be
detected in the popliteal fossa.
m:f//.:^,
Tibialis anterior //!r\\
Tibialis posterior
Flexor dig. longios
Ext. hall. long.
Tendo calcaneus
Fig. 1242. — The mucous sheaths of the tendons around the ankle. Medial aspect.
On the lower part of the front of the tibia the anterior tibial artery becomes
superficial and can be traced over the ankle into the dorsalis pedis; the latter can
be followed to the proximal end of the first intermetatarsal space. The pulsation
1342
SURFACE ANATOMY AND SURFACE MARKINGS
of the posterior tibial artery becomes evident near the lower end of the back of the
tibia, and is easily detected behind the medial malleolus.
Veins. — By compressing the proximal trunks, the venous arch on the dorsum
of the foot, together with the great and small saphenous veins leading from it (see
page 669), are rendered visible.
Nerves. — The only nerve of the lower extremity which can be located by palpa-
tion is the common peroneal as it winds around the lateral side of the neck of the
fibula.
SURFACE MARKINGS OF THE LOWER EXTREMITY.
Bony Landmarks. — The anterior superior iliac spine is at the level of the sacral
promontory — the posterior at the level of the spinous process of the second sacral
vertebra. A horizontal line through the highest points of the iliac crests passes
also through the spinous process of the fourth lumbar vertebra, while, as already
pointed out (page 1315), the transtubercular plane through the tubercles on the
iliac crests cuts the body of the fifth lumbar vertebra. The upper margin of the
greater sciatic notch is opposite the spinous process of the third sacral vertebra,
and slightly below this level is the posterior inferior iliac spine. The surface mark-
ings of the posterior inferior iliac spine and the ischial spine are both situated in a
line which joins the posterior superior iliac spine to the outer part of the ischial
tuberosity; the posterior inferior spine is 5 cm. and the ischial spine 10 cm. below
the posterior superior spine; the ischial spine is opposite the first piece of the
coccyx.
With the body in the erect posture the line joining the pubic tubercle to the top
of the greater trochanter is practically horizontal; the middle of this line overlies
the acetabulum and the head of the femur.
Sacrotuherous ligament
Sacrosfinous ligament
Greater trochanter
of femur
Ischial tuberosity
Fig. 1243. — N61aton's line and Bryant's triangle.
A line used for clinical purposes is that of Nelaton (Fig. 1243), which is drawn
from the anterior superior iliac spine to the most prominent part of the ischial
SURFACE ANATOMY AND SURFACE MARKINGS
1343
Superior gluteal
artery
Inferior gluteal
artery
Internal pudendal
artery
Fio. 1244. — Left gluteal region, showing surface markings for arteries and sciatic nerve.
Femoral nerve
Femoral artery
Adductor tubercle
A nterior tibial artery
" Deep peronceal nerve
Fig, 1245. — Front of right thigh, showing surface
markings for bones, femoral artery and femoral nerve.
Fig. 1246. — Lateral aspect of right leg, showing
surface markings for bones, anterior tibial and
dorsalis pedis arteries, and deep peroneal nerve.
1344
SURFACE MARKINGS OF THE LOWER EXTREMITY
\..
"---J"
-Sciatic nerve
Common
'peroneal,
nerve
Anterior
tibial'
artery
■ Popliteal artery
I t
■Tibial netve
Posterior tibial
artery
Fig. 1247. — Back of left lower extremity, showing surface markings for bones, vessels, and nerves.
SURFACE MARKINGS OF THE LOWER EXTREMITY 1345
tuberosity; it crosses the center of the acetahuhim and the upper border of the
greater trochanter. Another surface marking of chnical importance is Bryant's
triangle, which is mapped out thus: a hue from the anterior superior ihac spine
to the top of the greater trochanter forms the base of the triangle; its sides are
formed respectively by a horizontal line from the anterior superior iliac spine and
a vertical line from the top of the greater trochanter.
Articulations. — The posterior superior iliac spine overlies the center of the sacro-
iliac articulations.
The hip-joint may be indicated, as described above, by the center of a horizontal
line from tlie pubic tubercle to the top of the greater trochanter; or more generally,
it is below and slightly lateral to the middle of the inguinal ligament. The knee-joint
is superficial and requires no surface marking. The level of the ankle-joint is that
of a transverse line about 1 cm. above the level of the tip of the medial malleolus.
If the foot be forcibly extended, the head of the talus appears as a rounded promi-
nence on the medial side of the dorsum; just in front of this prominence and behind
the tuberosity of the navicular is the talonavicular joint. The calcaneocuboid joint
is situated midway between the lateral malleolus and the prominent base of the
fifth metatarsal bone; the line indicating it is parallel to that of the talonavicular
joint. The line of the fifth tarsometatarsal joint is very oblique; it starts from the
projection of the base of the fifth metatarsal bone, and if continued would pass
through the head of the first metatarsal. The lines of the fourth and third tarso-
metatarsal joints are less oblique. The first tarsometatarsal joint corresponds to a
groove which can be felt by making firm pressure on the medial border of the foot
2.5 cm. in front of the tuberosity of the navicular bone; the position of the second
tarsometatarsal joint is 1.25 cm. behind this. The metatarsophalangeal joints are
about 2.5 cm. behind the webs of the corresponding toes.
Muscles.— None of the muscles require any special surface lines to indicate
them, but there are three intermuscular spaces which occasionally require defini-
tion, viz., the femoral triangle, the adductor canal, and the popliteal fossa.
The femoral triangle is bounded above by the inguinal ligament, laterally by the
medial border of Sartorius, and medially by the medial border of Adductor longus.
In the triangle is the fossa ovalis, through which the great saphenous vein dips to
join the femoral; the center of this fossa is about 4 cm. below and lateral to the
pubic tubercle, its vertical diameter measures about 4 cm. and its transverse about
1.5 cm. The femoral ring is about 1.25 cm. lateral to the pubic tubercle.
The adductor canal occupies the medial part of the middle third of the thigh; it
begins at the apex of the femoral triangle and lies deep to the vertical part of
Sartorius. The popliteal fossa is bounded: above and medially by the tendons
of Semimembranosus and Semitendinosus; above and laterally by the tendon of
Biceps femoris; below and medially by the medial head of Gastrocnemius; below
and laterally by the lateral head of Gastrocnemius and the Plantaris.
Mucous Sheaths. — ^The positions of the mucous sheaths around the tendons
about the ankle-joints are sufficiently indicated in Figs. 1241, 1242 (see also page
489).
Arteries. — The points of emergence of the three main arteries on the buttock,
viz., the superior and inferior gluteals and the internal pudendal, may be indicated
in the following manner (Fig. 1244). With the femur slightly flexed and rotated
inward, a line is drawn from the posterior superior iliac spine to the posterior supe-
rior angle of the greater trochanter; the point of emergence of the superior gluteal
artery from the upper part of the greater sciatic foramen corresponds to the junction
of the upper and middle thirds of this line. A second line is drawn from the poste-
rior superior iliac spine to the outer part of the ischial tuberosity; the junction
of its lower with its middle third marks the point of emergence of the inferior
gluteal and internal pudendal arteries from the lower part of the greater sciatic
8")
1346 SURFACE ANATOMY AND SURFACE MARKINGS
foramen. The course of the femoral artery (Fig. 1245) is represented by the upper
two-thirds of a Hne from a point midway between the anterior superior iliac spine
and the symphysis pubis to the adductor tubercle, with the thigh abducted and
rotated outward; the profunda femoris arises from it about 1 to 5 cm. below the
inguinal ligament. The course of the upper part of the popliteal artery (Fig. 1247)
is indicated by a line from the lateral margin of Semimembranosus at the junction
of the middle and lower thirds of the thigh, obliquely downward to the middle of
the popliteal fossa; from this point it runs vertically downward for about 2.5 cm.
or to the level of a line through the lower part of the tibial tuberosity. The line
indicating the anterior tibial artery (Fig. 1246) is drawn from the medial side of
the head of the fibula to a point midway between the malleoli; the artery begins
about 3 cm. below the head of the fibula. The dorsalis pedis artery is represented
on the dorsum of the foot by a line from the center of the interval between the
malleoli to the proximal end of the first intermetatarsal space.
The course of the posterior tibial artery (Fig. 1247) can be shown by a line from
the end of the popliteal artery, i. e., 2.5 cm. below the center of the popliteal fossa,
to midway between the tip of the medial malleolus and the center of the convexity
of the heel; its main branch, the peroneal artery, begins about 7 or 8 cm. below the
level of the knee-joint and follows the line of the fibula to the back of the lateral
malleolus. The medial and lateral plantar arteries begin from the end of the poste-
rior tibial; the medial extends to the middle of the plantar surface of the ball of the
great toe, the lateral to within a finger's breadth of the tuberosity of the fifth
metatarsal bone; from tliis latter point the plantar arch crosses the foot trans-
versely to the proximal end of the first intermetatarsal space.
Veins. — The line of the great saphenous vein is from the front of the medial
malleolus to the center of the fossa ovalis; the small saphenous vein runs from the
back of the lateral malleolus to the center of the popliteal fossa.
Nerves. — The course of the sciatic nerve (Fig. 1247) can be indicated by a line
from a point midway between the outer border of the ischial tuberosity and the
posterior superior angle of the greater trochanter to the upper angle of the popliteal
fossa. The continuation of this line vertically through the center of the popliteal
fossa represents the position of the tibial nerve, while the common peroneal nerve
follows the line of the tendon of Biceps femoris. The lines for the deep peroneal
nerve and the continuation of the tibial nerve correspond respectively to those for
the anterior and posterior tibial arteries.
INDEX.
Abdomkn, 1147
apertures in walls of, 1147
boundaries of, 1147
fascia of, 408
triaiifiular, 412
lymi)h glands of, 703
muscles of, 408
actions of, 417
nerves of, 417
regions of, 1147
surface anatomy of, 1313
markings of, 1315
Abdominal aorta, 603
branches of, G03
surface markings of, 1321
aortic plexus, 987
muscles, 408
ring, deep, 418
external, 410
inguinal, 418
internal, 418
wall, lymphatic vessels of, 706
Abducent nerve, 899
composition and central con-
nections of, 861
Abductor digiti quinti muscle
(foot). 492
actions of, 496
nerves of, 495
variations of, 492
(hand), 463
actions of, 464
nerves of, 464
variations of, 464
hallucis muscle, 491
actions of, 495
nerves of, 495
variations of, 491
indicis muscle, 464
minimi digiti muscle, 463
pollicis brevis muscle, 461
actions of, 462
nerves of, 462
variations of, 462
longus muscle, 455
actions of, 456
nerves of, 456
variations of, 455
muscle, 461
Aberrant ducts of testis, 1246
Abnormalities of vertebral col-
umn, 116
Accelerator urinae muscle, 428
Accessory hemiazygos vein, 667
nerve, 913
composition and central con-
nections of, 855
cranial part of, 913
spinal part of, 913
obturator nerve, 955
olivary nuclei, 781
organs of digestive tube, 1100
of eye, 1021
pancreatic duct, 1202
part of parotid gland, 1134
processes, 106
pudendal artery, 618
sinuses of nose, 998
Accesson,' spleens, 1283
thyroid glands, 1270
Acetabular fossa, 237
notch, 237
Acetabulum, 237
Achromatic spindle, 37
Acoustic meatus, external, 145,
183, 1036
development of, 1033
internal, 143, 193
nerve, 905, 1035
composition and central con-
nections of, 857
development of, 1033
nuclei of, 788, 906
Acromioclavicular .joint, 315
movements of, 316
surface anatomy of, 1328,
1331
Acromion, 203
Acromiothoracic artery, 588
Adamantoblasts, 1123
Adductor brevis muscle, 473
actions of, 474
nerves of, 474
variations of, 474
canal, 627
hallucis muscle, 493
actions of, 496
nerves of, 495
variations of, 494
longus muscle, 472
actions of, 474
nerves of, 474
variations of, 474
magnus muscle, 473
actions of, 474
nerves of, 474
variations of, 474
minimus muscle, 474
obliquus hallucis muscle, 493
pollicis muscle, 462
pollicis muscles, actions of, 462
nerves of, 462
variations of, 462
obliquus muscle, 462
transversus muscle, 462
transversus pollicis muscle, 462
tubercle, 246
Adipose capsule of kidney, 1220
Adminiailum linecr alba', 417
Adrenal capsule, 1278
gland, lymphatic capillaries in,
686
Adrenalin, 1280
Afferent nerves, 729
vessels of kidney, 1224
After-birth, 64
Agger nasi, 161
Aggregated lymphatic nodules,
1176
Agminated follicles, 1176
Air cells, ethmoidal, 154, 998
mastoid, 142
sinuses of nose, 998
of skull, 80
Ala cinerea, 800
lobuli centralis, 789
nasi, 992
OSS. ilii, 232
684
Alse of ethmoid, 153
of sacrum, 110
of vomer, 170
Alar cartilages of nose, 993
lamina, 735
Alcock, canal of, 421
Alimentary canal, 1100
lymphatic capillaries in
Allantoic vessels, 54
Allantois, 54
Alveolar arch, 161
arteries, 561
border of mandible, 173
Canals, 158
index, 199
nerves, 890, 891, 896
point, 161, 198
process of maxiUa, 161
Alveoli, formation of, 1124
Alveus, 833, 840
Amacrine cells of retina, 1017
Amnion, 56
false, 56
Amniotic ca'vity, 56
ectoderm, 56
fold, 56
Amphiarthroses, 284
Ampulla of ductus deferens, 1246
rectal, 1183
of uterine tube, 1257
of Vater, 1199
Ampullae of semicircular canals,
1049
of tubuli lactiferi, 1268
Amygdala, 835
Amygdaline nucleus, 791
Amygdaloid nucleus, 869
Anal canal or anal part of rectum,
1184
development of, 1108
Ijinphatic vessels of, 711
membrane of, 1110
valves of, 1184
fascia, 421
Anaphase of karyokinesis, 37
Anastomoses of arteries, 543
around elbow-joint, 592
knee-joint, 634
crucial, 630
Anastomotic branch of inferior
gluteal artery, 620
Anastomotica magna of brach:
artery, 592
of femoral artery, 631
Anatomical neck of humeru
Anconseus muscle, 454
actions of, 456
nerves of, 456
Angiology, 497
Angle of Louis, 121, note
iridial or filtration, 1007
of mandible, 174
of pubis, 236
of rib, 124
sacrovertebral, 106
of sternum, 121
subscapular, 203
Angular artery, 556
gjTus, 823
movement, 286
( 1347 )
1348
INDEX
Angular vein, 645
Angulus Ludo\dci, 121
Animal cell, 35
Ankle bone, 266
Ankle-joint, 349
movements of, 351
relations of tendons and vessels
to, 351
surface anatomy of, 1338
markings of, 1343
Annular ligament, 456, 458
of ankle, 488, 489
of radius, 324
of wrist, anterior, 456
posterior, 458
Annulus fibrosus fof interverte-
bral fibrocartilage], 289
inguinalis abdominis, 418
subcutaneus, 410
ovalis, 531
(endincus communis, 1022
Anococcygeal body, 1184
nerves, 968
raphe, 426
Ansa hypoglossi, 928
lentiformis, 835, 837
subclavia [Vieusseni], 981
Anterior anniilax ligament, 456,
488
basis bundle, 760
calcaneoastragaloid ligament,
352
circumflex artery, 589
common ligament, 287
condyloid foramen, 131
cornu of medulla spinalis, 753
costovertebral ligament, 299
crural nerve, 955
inferior ligament, 348
intercostal arteries, 584
interosseous artery, 596
nerve, 938
ligament, 327
perforated substance, 869
peroneal artery, 638
pillar of fauces, 1137
pillars of fornix, 838
pulmonary nerves, 913
radial carpal artery, 594
radioulnar ligament, 325
superior dental nerve, 891
ligament, 301, 348
talotibial ligament, 351
temporal artery, 559
tibial nerve, 965
ulnar carpal artery, 598
Antero-lateral fasciculas, super-
ficial, 854
ganglionic arteries, 573
muscles of abdomen. 408
Antero-medial ganglionic arteries,
571
Antibrachial fascia, 445
cutaneous nerve, dorsal, 944
til' lateral, 935
medial, 937
Antirubital fossa, 589
Antihelix, 1033
titragicus muscle, 1035
ntitragus, 1034
Anlrurn cardiacum, 1161
of Highmore, 159. 999
pyloric, 1162, 1163
tympanic, 142, 1042
entrance to, 1042
Anus 1100, 1184
hnijjhatic vessels of, 711
\orta, 545
abdominal, 602
branches of, 603
<ii' lominaliii, 602
uM-hof, 547
branches of, 548
peculiarities of, 548
o| branches of, 548
Aorta ascendens, 545
ascending, 545
bulb of, 545
coarctation of, 547
descending, 598
thoracalis, 598
rami media stinales, 600
pericardiaci, 600
thoracic, 598
branches of, 600
transverse, 547
Aortse, anterior ventral, 516
dorsal, 517
primitive, 506
Aortic arches, 516
bodies, 1278
glands, 1269, 1278
hiatus, 406
isthmus, 517, 546
lymph glands, 705
opening of hea^t, 534
plexus, 987
semilunar valves, 534
septum, 514
sinuses, 534
spindle, 547
vestibule, 534
Aorticorenal ganglion, 985
Apertura pelvis [minor in] inferior,
240
superior, 239
tympanica canaliculi chordcB,
1038
Aperture, anterior nasal, 196
Apertures in -walls of abdomen,
1147
Apex cordis, 527
of fibula, 260
of heart, 527
lingua, 1125
of nose, 992
OSS, sacri, 110
prostata', 1252
pulmonis, 1094
Aponeurosis, 376
epicranial, 380
lumbar, 397
of obliquus externus, 410
palatine, 1139
palmar, 460
palmaris, 460
pharyngeal, 1143
plantar, 490
plantaris, 490
suprahyoid, 392
Apparatus digestorius, 1100
lacrimalis, 1028
respiratorius, 1071
urogenitalis , 1204
Appendages of testis, 1242
Appendices cpiploicce, 1 158
vesiculosa:, 1257
Appendicular artery, 607
skeleton, 79
Appendix, auricular, left, 533
right, 529
ensiform, 121
of epididymis, 1242
of testis, 1242
of ventricle of larynx, 1080
ventriculi laryngis, 1080
vermiform, 1178
xiphoid, 121
Aquccductus cerebri, 806
cochleoe, 144, 181
Fallopii, 143
vestibuli, 143
Aqueduct, cerebral, 806
of cochlea, 144
of Sylvius, 766, 806
Aqueous humor, 1018
Arachnoid, 876
granulations, 878
structure of, 876
\illi, 878
Arachnoidea encephali, 876
spinalis, 876
Arantii, corpus, 533. 535
Arbor vitce fof cerebellum], 791
utcrina, 1260
Arch, alveolar, 161
of aorta, 547
branches of, 548
peculiarities of, 548
of atlas, 99
axillary, 434
carotid, 516
crural, deep, 419
glossopalatine, 1137
lumbocostal, 405
palmar, deep, 595
superficial, 598
pharyngopalatine, 1 137
plantar, 639
pubic, 240
of a vertebra, 96
volar, deep, 595
superficial, 598
zygomatic, 183
Arches, aortic, 506. 516
branchial or \-isceral, 65
of fauces, 1137
of foot, 360
superciUarj% 135, 178, 183
Architecture of femur, 248
Arcuate artery, 637
fibers, 782, 783
ligaments, 404
line of ilium, 234
nucleus, 782
Arcus aortce, 547
cartilaginis cricoideas, 1074
glossopalatinus, 1137
lumbocostalis lateralis [Halleri],
405
medialis [Halleri], 404
parietooccipiialis, 823
pharyngopalaiinus, 1 137
volaris profundus, 595
superficialis, 598
Area acustica, 800
cribrosa media, 143
superior, 143
facialis, 143
olfactorj', 67
oval, of Flechsig, 764
parolfacloria, 827
pericardial, 47
postrema, 800
proamniotic. 47
Areas of cerebral cortex, 849
of Cohnheim, 374
vascular, 505
Areola of mamma, 1267
Areola? of bone, 93, 94
Areolar glands, 1267
Arm bone, 209
fascia of, 442
muscles of, 442
development of, 371
Arnold's nerve, 911
Arrectores pUorum muscle. 1069
Arteria alveolaris inferior, 561
superior posterior, 562
angularis, 556
anonyma, 548
arcuata, 637
auditiva interna, 580
auricularis posterior, 557
ramus auricularis, 556
occipitalis, 557
profundus, 560
axillaris, 586
basilaris, 580
rami ad ponlem, 580
hrachialis, 589
rami muscidares, 592
buccinatoria, 561
bulbi urethrae, 619
canalis pterygoidei, 562, 568
INDEX
1349
Arteria caroiis communis, 549
externa, 551
interna, 566
ramus caroticotijmpanicus,
568
centralis retina', 571, 1018
cerebelli inferior anterior, 580
posterior, 580
superior, 580
cerebri anterior, 571
media, 572
posterior, 580
cervicalis ascendens, 581
profunda, 585
chorioidea, 574
circumfiexa femoris lateralis, 630
medialis, 630
humeri anterior, 589
posterior, 589
ilium profunda, 623
superficialis, 629
scapidee, 588
caeliaca, 603
colica dcxtra, 609
media, 609
sinistra, 610
collateralis ulnaris inferior, 592
superior, 591
comes nerti phrenici, 583
comitans nervi ischiadici, 620
communicans anterior, 572
posterior, 573
coronaria [cordis] dextra, 546
sinistra, 547
cystica, 605
dor satis hallucis, 637
nasi, 571
pedis, 636
ramus plantaris profundus,
637
epigastrica inferior, 623
superficialis, 629
superior, 585
femoralis, 623
rowi musculares, 629
frontalis, 570
gastrica dextra, 604
sinistra, 603
gastroduodenalis, 604
gastroepiploica dextra, 604
sinistra, 606
^enu media, 633
suprema, 631
glutcea inferior, 620
ramus iliacus, 621
lumbalis, 621
superior, 622
hcEmorrhoidolis inferior, 619
media, 615
superior, 610
hepatica, 603
hypogastrica, 614
ileocolica, 007
iliaca externa, 622
iliolumbalis, 621
infraorbitalis, 562
interossea communis, 596
dorsalis, 596
volaris, 596
labialis inferior, 555
superior, 555
lacrimalis, 569
laryngea inferior, 581
superior, 552
lienalis, 605
rami pancreatici, 606
lingualis, 553
rami dorsales lingua, 553
ramus hyoideus, 553
malleolaris anterior lateralis, 635
medialis, 635
posterior ynedialis, 639
mammaria interna, 583
rami inter costales. 584
perforantes, 584
Arteria mammaria interna, rami
sternales, 584
masseterica, 561
maxillaris externa, 553
ra»?i glanduhwes, 555
ramus tonsillaris, 555
interna, 559
rami pterygoidei, 561
rarwMs meningeus acces-
sorius, 561
media na, 596
meningea anterior, 568
media, 560
mesenterica inferior, 609
superior, 606
muscidophrenica, 584
nutricia fibulae, 638
humeri, 591
n'bi<r, 638
obturatoria, 616
occipitalis, 556
rami musculares, 556
ramus aurieularis, 556
descendens, 557
meningeus, 557
ophthalmica, 568
palatina ascendens, 555
descendens, 562
pancreatica magna, 606
pancreaticoduodenalis inferior,
607
superior, 605
perforans prima, 631
secunda, 631
tertia, 631
pericardiacophrenica, 583
perinei, 619
peronaea, 638
ramus calcaneus lateralis,
638
communicans, 638
perforans, 638
pharyngea ascendens, 557
rami pharyngei, 558
plantaris lateralis, 639
medialis, 639
poplitea, 632
princeps cerricis, obi
hallucis, 640
poinds, 595
profunda brachii, 591
femoris, 629
penis, 620
pudenda externa profunda, 629
•superficialis, 629
interna, 617
pulmonalis, 543
ramus dexter, 545
sinister, 545
radialis, 592
romi 7nuscidares, 594
perforantes, 595
ramus carpeus dorsalis, 594
volaris, 594
volaris superficialis, 594
recurrens radialis, 594
tibialis anterior, 635
posterior, 635
recurrentes ulnaris anterior, 596
posterior, 596
sacralis lateralis, 621
media, 613
sphenopalatina, 562
spinalis anterior, 579
posterior, 579
stemocleidomasioidea, 556
stylomastoidea, 557
subclavia, 575
• sublingualis, 553
submentalis, 555
subscapularis, 588
supraorbitalis, 569
tarsea lateralis, 637
temporalis media, 558
superficialis, 558
I Arteria temporalis superficialis,
rami auriculares ante-
riores, 559
ramus frontalis, 559
parietalis, 559
thoracalis lateralis, 588
suprema, 587
thoracoacromialis, 588
thyreoidea ima, 549
inferior, 581
rami ce.'sophagei, 581
tracheales., 581
superior, 552
ramus cricothyreoideus, 552
hyoideus, 552
sternocleidomastoideus,
552
tibialis anterior, 634
rami musculares, 635
posterior, 637
rami calcanei mediates, 639
ramus communicans, 639
transversa colli, 582
ramus ascendens, 582
descendens, 582
faciei, 558
scavidoe, 582
tympanica anterior, 560
inferior, 558
ulnaris, 595
rami musculares, 598
ramus carpeus dorsalis, 598
volaris, 598
volaris profundus, 598
urethralis, 619
uterina, 615
vagirudis, 616
vertebralis, 578
rami spinales, 579
ramus meningeus, 579
vesicalis inferior, 615
medialis, 615
superior, 615
volaris indicis radialis, 595
AriericB bronchioles, 600
ciliares, 571
digitales volar es communes, 598
propria!, 598
gastricce breves, 606
fifenu inferiores, 633
super iores, 633
iliaca; communes, 613
inter CO stales, 600
intestinales , 607
lumbales, 612
metacarpeae volares, 595
metatarsew plantares, 640
cesophagece, 600
ovaricw, 611
palpebrales mediates, 570
phrenicw inferiores, 612
proprim renales, 1223
recte, 1224
renames, '610
sigmoideae, 610
spermaticoe internee, 611
suprarenates media, 610
surates, 633
tarsece mediates, 637
tunica adventitia, 499
intima, 498
media, 498
Arterial mesocardium, 526
Arterioles, 497
Artery or Arteries, abdominal
aorta, 602
accessory pudendal, 618
meningeal, 561
acromiothoracic, 588
alveolar, 561
anastomoses of, 543
anastomotic branch of inferior
gluteal, 620
anastomotica magna, of bra-
chial, 592
1350
INDEX
Artery or Arteries, anastomotica
magna of femoral, 631
angular, 556
anterior cerebral, 571
choroidal, 574
ciliary, 571
communicating, 571
humeral circumflex, 589
inferior cerebellar, 580
meningeal, 568
spinal, 579
tibial, 634
tympanic, 560
antero-lateral ganglionic, 573
antero-medial ganglionic, 561
aorta, 545
abdominal, 602
arch of, 547
ascending, 545
descending, 598
thoracic, 598
appendicular, 607
arcuate, 637
articular, 633
ascending cervical,. 581
palatine, 555
pharyngeal, 557
auditory, 580
internal, 580
auricular, anterior, 559
deep, 560
of occipital, 557
posterior, 557
axillary, 586
azygos, of knee, 633
of vagina, 616
basilar, 580
brachial, 589
brachiocephalic, 548
of brain, 574
bronchial, 600, 1100
buccal, 561
buccinator, 561
bulbar, 580
calcaneal, 638, 639
capsular, middle, 610
caroticotympanic, 568
carotid, common, 549
external, 551
internal, 566
carpal, dorsal, 594
radial, 594
ulnar, 598
volar, 594, 598
cavernous, 568
cecal, of ileocolic, 607
central, of retina, 571, 1018
cerebellar, 580
cerebral, anterior, 571
middle, 572
posterior, 580
of cerebral hemorrhage, 573
cervical, ascending, 581
deep, 585
superficial, 582
transverse, 582
choroid, 574
choroidal, 574, 581
ciliary, 571
circle of Willis, 574
circumflex, femoral, 630
humeral, 589
coccygeal of inferior gluteal, 620
cochlear, 1059
cceliac, 603
colic, 609, 610
comitans nervi ischiadici, 620
phrenici, 583
common carotid, 549
iliac, 613
interosseous, 596
communicating, anterior, 571
of dorsalis pedis, 637
posterior, 573
coronary, of heart, 546
Artery or Arteries, coronary, of
lips, 555
of stomach, 603
of corpus cavernosum, penis,
620
costocervical trunk, 585
cremasteric, 623
cricothyroid, 552
cystic, 605
deep auricular, 560
epigastric, 623
external pudendal, 629
iliac circumflex, 623
palmar arch, 595
of penis, 617
plantar, 637
temporal, 561
volar branch of ulnar, 598
dental, inferior, 561
posterior, 562
descending aorta, 598
development of, 505, 514
branch of occipital, 557
palatine, 562
digital, foot, 640
hand, 598
volar, 598
distribution of, 543
dorsal carpal of radial, 594
of ulnar, 598
interosseous, 596
metacarpal, 594
nasal, 571
of penis, 620
dorsales linguae, 553
dorsalis hallucis, 637
pedis, 636
scapulae, 588
of ductus deferens, 615
epigastric, deep or inferior, 623
superficial, 629
superior, 585
esophageal, of aorta, 600
of inferior thyroid, 581
ethmoidal, 570
external carotid, 551
iliac, 622
maxillary, 553
plantar, 639
pudendal, 629
facial, 553
transverse, 558
femoral, 623
circumflex, 630
fibular, 635
frontal, 570
ganglionic, 571, 573, 581
gastric, 603, 604, 606
gastroduodenal, 604
gastroepiploic, 604, 606
genicular, 631, 633, 634
gluteal, 620
of head and neck, 549
iielicine, 1251
hemorrhoidal, inferior, 619
middle, 615
superior, 610
hepatic, 603
highest genicular, 631
intercostal, 585
thoracic, 587
humeral circumflex, 589
hypogastric, 614
obliterated, 615
ileal, of ileocolic, 607
ileocolic, 607
iliac circumflex, deep, 623
superficial, 629
common, 613
external, 622
internal, 614
iliolumbar, 621
inferior alveolar, 561
articular, of knee, 633
cerebellar, 580
Artery or Arteries, inferior epi-
gastric, 623
genicular, 633
gluteal, 620
hemorrhoidal, 619
labial, 555
laryngeal, 581
mesenteric, 609
pancreaticoduodenal, 607
phrenic, 612
profunda, 591
thyroid, 581
tympanic, 558
ulnar collateral, 592
infrahyoid, 552
infraorbital, 562
infrascapular, 588
innominate, 548
intercostal, 600, 601
branches of internal mam-
mary, 583
highest, 585
superior, 585
interlobular, of kidney, 1223
internal auditory, 580, 1059
carotid, 566
iliac, 614
mammary, 583
maxillary, 559
palpebral, 570
plantar, 639
pudendal or pudic, 617
spermatic, 611
interosseous, anterior, 596
common, 596
dorsal, 596
palmar, 595
posterior, 596
volar, 596
intestinal, 607
labial, 555
of labyrinth, 1059
lacrimal, 569
laryngeal, inferior, 581
superior, 552
lateral calcaneal, 638
femoral circumflex, 630
nasal, 556
palpebral, 569
sacral, 621
tarsal, 637
left colic, 610
gastric, 603
gastroepiploic, 606
lienal, 605
lingual, 553
deep, 553
long ciliary, 571
thoracic, 588
of lower extremity, 623
lumbar, 612
malleolar, 635
internal, 639
mammary, internal, 583
masseteric, 561
maxillary, external, 553
internal, 559
medial palpebral, 570
mediana, 596
mediastinal, from aorta, 600
from internal mammary, 583
medidural, 560
medullary, 580
meningeal, accessory, 561
anterior, 568
of ascending pharyngeal, 558
middle, 560
of occipital, 557
small, 561
of vertebral, 579
mesenteric, inferior, 609
superior, 606
metatarsal, 637
middle cerebral, 572
genicular, 633
INDEX
1351
Artory or Arteries, middle hemor-
rhoidal, 615
meningeal, 560
sacra], 612
mode of division of, 54.3
of origin of branches, 543
musculophrenic, 583
mylohyoid, 561
nasal, 571
dorsal, 571
lateral, 556
nasopalatine, 562
nerves of, 499
obturator, 616
occipital, 556
ophthalmic, 568
ovarian, 611
palatine, ascending, 555
of ascending pharyngeal, 557
descending, 562
palmar arch, deep, 595
superficial, 598
palpebral, 569, 570
internal, 570
pancreatic, of lienal, 606
pancreaticoduodenal, 605
par\-idural, 561
perforating, of foot, 640
of hand, 595
of internal mammary, 584
of thigh, 631
pericardiacophrenic, 584
pericardial, 584, 600
perineal, 619
superficial, 619
peroneal, 638
anterior, 638
pharj^ngeal, ascending, 557
of internal maxillary, 562
phrenic, inferior, 612
superior, 601
plantar, deep, 637
lateral (external), 639
medial (internal), 639
metatarsal, 640
pontine, 580
popliteal, 632
posterior auricular, 557
cerebral, 580
communicating, 573
humeral circumflex, 589
inferior cerebellar, 580
meningeal, from vertebral,
579
scapular, 582
scrotal, 619
superior alveolar, 562
tibial, 637
postero-medial ganglionic, 574,
581
princeps cer\dcis, 557
poUicis, 595
profunda, 591
brachii, 591
cer\'icalis, 585
femoris, 629
linguae, 553
superior, 591
of pterygoid canal, 562, 568
pudendal, external, 629
internal, 617
in female, 620
in male, 617
pudic, external, 629
internal, 617
pulmonary, 543
pyloric, 604
radial, 592
recurrent, 594
radialis indicis, 595
ranine, 553
recurrent, of hand, 595
interosseous, 597
radial, 594
tibial, 635
Artery or Arteries, recurrent
ulnar, 596
renal, 610
right colic, 609
gastric, 604
gastroepiploic, 606
sacral, lateral, 621
middle, 613
scapular circimiflcx, 588
posterior, 582
transverse, 582
sciatic, 620
scrotal, posterior, 619
sheaths of, 499
short ciliary, 571
gastric, 606
sigmoid, 610
spermatic, 611
external, 623
internal, 611
sphenopalatine, 562
spinal, 579
splenic, 605
sternocleidomastoid, 552, 556
sternomastoid, 552, 556
striate, 573
structure of, 498
stylomastoid, 557
subclavian, 575
subcostal, 601
sublingual, 553
submaxillary, 555
submental, 555
subscapular, 588
superficial cervical, 582
epigastric, 629
external pudendal, 629
iliac circumflex, 629
palmar arch, 598
temporal, 558
volar, 594
arch, 598
superior articular, of knee, 633
cerebellar, 580
epigastric, 585
gluteal, 622
hemorrhoidal, 610
intercostal, 585
labial, 555
laryngeal, 552
mesenteric, 606
- phrenic, 601
profunda, 591
thoracic, 587
thyroid, 552
tympanic, 561
ulnar collateral, 591
vesical, 615
superhyoid, 553
supraorbital, 569
suprarenal, 610, 612
suprascapular, 582
sural, 633
systemic distribution of, 543
tarsal, 637
temporal, 558
deep, 561
middle, 558
superficial, 558
thoracic, 587, 588
aorta, 598
axis, 588
liighest, 587
lateral, 588
superior, 587
thoracoacromial, 588
thyreoidea ima, 549
thyrocervical trunk, 581
thyroid axis, 581
inferior, 581
superior, 552
tibial, anterior, 634
posterior, 637
recurrent, 635
tonsillar, 555
Artery or Arteries, transversa
colli, 582
transverse cervical, 582
facial, 558
perineal, 619
scapular, 582
transversalis coUi, 582
of trunk, 598
tympanic, 558, 560
ulnar, 595
recurrent, 596
umbilical, in fetus, 540
of upper extremity, 575
urethral, 619
of urethral bulb, 619
uterine, 615
vaginal, 616
vasa aberrantia, 590
brevia, 606
intestini tenuis, 607
vertebral, 578
vesical, 615
vestibular, 1059
Vidian, 562, 568
volar arch, deep, 595
superficial, 598
carpal, 594
digital, common, 598
interosseous, 596
metacarpal, 595
proper, 598
volaris indicis radialis, 595
Arthrodia, 286
Articular arteries, 633
capsules, 279
cartilage, 282
disk of acromioclavicular joint,
315
of distal radioulnar joint, 325
of sternoclavicular joint, 314
of temporomandibular joint,
258
lamella of bone, 279
meniscus, 298
processes of vertebree, 96
tubercle of temporal bone, 139,
180
Articulatio acromioclavicularis, 315
atlantoepistrophica, 292
calcaneocuboidea, 354
coxes, 333
cubiti, 321
cuneonavicularis, 356
cllipsoidea, 286
genu, 339
humeri, 317
mandihularis, 297
radiocarpea, 327
radioulnaris, 324
distalis, 325
proximalis, 324
sacroiliaca, 306
sellaris, 286
sternoclavicularis, 313
talocalcanea, 352
lalocalcaneonavicularis, 353
talocruralis, 349
tibiofibularis, 348
trochoidea, 285
Articxilation or Articulations, 279
acromioclavicular, 315
amphiarthroses, 285
of ankle, 349
atlantooccipital, 295
of atlas with axis or epistro-
pheus, 292
with occipital bone, 295
calcaneocuboid, 354
of calcaneus and astragalus, 352
with the cuboid, 354
carpometacarpal, 330
of carpus, 328
of cartilages of ribs with each
other, 304
classification of, 284
1352
INDEX
Articulation or Articulations, con-
dyloid, 285
costocentral, 299
costochondral, 304
costosternal, 302
costotransverse, 300
costovertebral, 299
coxal, 333
cuboideonavicular, 356
cuneocuboid, 357
cuneonavicular, 356
diarthroses, 285
of digits, 333
of elbow, 321
gomphosis, 284
of hip, 333
humeral, 317
immovable, 284
inferior, 325
intercarpal, 328
interchondral, 304
intercuneiform, 357
intermetacarpal, 331
intermetatarsal, 358
intertarsal, 352
of knee, 339
of lower extremity, 333
of mandible, 297
metacarpophalangeal, 332
metatarsophalangeal, 359
movable, 285
movements of, 286
of navicular with cuneiform
bones, 356
of pelvis, 306
with vertebral column, 306
of phalanges of foot, 359
of hand, 333
of pubic bones, 310
sj-mphysis, 310
radiocarpal, 327
radioulnar, 324, 325
by reciprocal reception, 286
sacrococcygeal symphysis, 309
sacroiliac, 306
of sacrum and coccyx, 309
scapuloclavicular, 315
schindylesis, 284
of shoulder, 317
sternoclavicular, 313
sternocostal, 302
of sternum, 304
sutura, 284
symphysis, 285
pubis, 310
synarthroses, 284
synchondrosis, 284
syndesmosis, 285
talocalcaneal, 352
talocalcaneonavicular, 353
talocrural, 349
tarsometatarsal, 358
of tarsus, 352
temporomandibular, 297
tibiofibular, 348
syndesmosis, 348
tibiotarsal, 349
of trunk, 287
of upper extremity, 313
of vertebral arches, 289
bodies, 287
column, 287
with cranium, 295
■wath pelvis, 306
of wrist, 327
Arliculalioncs capitulorum, 299
carpometacarpeoB, 330
poinds, 330
costotransvcrsaria, 300
costovertebralcs, 299
digitorurn manus, 333
pedis, 359
intercarpcw, 328
inter chondr ales, 304
intermetacarpew, 331
Articulationes intermctatarsew, 358
inlertarscir, 352
metatarsophalangca;, 359
ossiculoni7n aiiditus, 1045
stcrnocoslalcs, 302
tarsotnctatarse(r, 358
Aryepiglottic fold, 1079
Aryepiglotticus muscle, 1083
Arytajnoideus muscle, 1082
Arvtenoid cartilages, 1075
glands, 1084
swellings, 1071
Ascending aorta, 545
cervical artery, 582
colon, 1180
frontal convolution, 821
lumbar vein, 667
oblique muscle, 412
palatine artery, 555
parietal convolution, 823
pharyngeal arterj-, 557
ramus of ischium, 235
of OS pubis, 235
Association fibers of cerebral
hemispheres, 843
neurons, 755
•Asterion, 183, 198
Astragalus, 266
ossification of, 275
Atavistic epiphyses, 95
Atlantooccipital articulation, 295
Atlas, 99
development of anterior arch
of, 82
ossification of, 113
Atresia, congenital, of pupil, 1003
Atria of bronchi, 1098
Atrial canal, 508
Atrioventricular bundle of His,
537
opening, left, 533, 534
right, 531
Atrium dextrum; 529
of heart, left, 533
primitive, 508
right, 529
of nasal fossa, 994
sinistrurn, 533
Attic or epitympanic recess, 142,
1038
Attolens aurem muscle, 1035
Attrahens aurem muscle, 1035
Auditory artery, 580
internal, 580
canal, external, 1036
meatus, external, 1036
nerve, 905
ossicles, 1044
development of, 1033
pit, 1029
plate, 1029
teeth of Huschke, 1055
tube, 1042
cartilaginous portion of, 1043
cushion of, 1043, 1147
isthmus of, 1043
osseous portion of, 1043
pharyngeal ostium of, 1141
tonsil of, 1043-
torus tubarius, 1043
veins, 1059
vesicle, 1030
Auerbach's plexus, 1177
Auricle, left, 533
right, 523
Auricula dcxtra, 529
of ear, 1033
cartilage of, 1034
development of, 1033
ligaments of, 1035
nmscles of, 1035
vessels and nerves of, 1036
of heart, left, 533
right, 529
sinistra, 533
Auricular appendix, loft, 533
right, 529
artery, anterior, 559
deep, 560
of occipital, 557
posterior, 557
lymph glands, 693
nerve, anterior, 895
great, 926
posterior, 905
of vagus, 911
point, 198
surface of ilium, 234
of sacrum, 108
tubercle of Darwin, 1033
vein, posterior, 646
Auricularis muscles, 1035
Auricvilotemporal nerve, 895
Auriculoventricular groove, 527
Auris interna, 1047
Auscultation, triangle of, 434
Axes of ])clvis, 240
Axial filament of spermatozoon, 43
skeleton, 79
Axilla, 585
fascia of, 436
Axillary arch, 434
artery, 586
branches of, 587
surface markings of, 1331
lymph glands, 699
nerve, 934
sheath, 586
vein, 063
Axis, celiac, 603
of lens, 1019
optic, 1001
thoracic, 588
thyroid, 581
of vertebra, 100
ossification of, 113
Axis-cylinder process, 723
Axon of nerve cells, 723
Azygos arteries of vagina, 616
arten,-, articular, 633
uvulae muscle, 1139
vein, 667
Back, muscles of, 396
Baillarger, band of, 835, 845
Ball-and-socket joint, 285
Band of Baillarger, 835, 845
of Bechterew, 846
of Gennari, 846
of Giacomini, 827
ihotibial, 468
moderator, 532
Bare area of liver, 1150
Bartholin, duct of, 1136
glands of, 1213, 1266
Basal column, posterior, 758
lamina, 735
optic nucleus of Meynert, 813
plate of placenta, 63
ridge, or cingulumof tooth,1116
vein, 653
Base of cerebral peduncle, 802
of heart, 527
of sacrum, 109
of skull, inferior surface, 179
upper surface of, 190
Basichromatin, 37
Basihyal of hyoid bone, 177
Basilar artery, 580
crest, 1054
membrane, 1056
part of occipital bone, 132
plexus of veins, 660
sinus, 660
Basilic vein, 662
median, 661
Basion, 181, 198
INDEX
1353
Basis bundle, anterior, 7G0
lateral, 762
cordis, 527
OSS. sacri. 109
pcdunculi, 802
prostata, 1252
•pulmonis, 1094
Basivertebral veins, 0G8
Basket ceus of cerebellum, 794
Bechterev,-, band of, S4{i
nufleus of, 788
pontospinal fasciculus of, 872
Bed of stomach, 1102
Bell, nerve of, 928, 933
Bellini, duet of, 1223
Bertin, litiament of, 335
Betz, giant cells of, 845
Biceps brachii muscle, 443
actions of, 444
nerves of, 444
variations of, 444
femoris muscle, 478
actions of, 480
nerves of, 480
variations of, 479
flexor cubiti muscle, 443
muscle, 443
Bicipital fascia, 444
groove, 209
ridges, 209
Bicuspid teeth, 1118
valve, 534
Bigelow, Y-shaped ligament of,
335
Bile capillaries, 1197
ducts, 1197, 1198
lymphatic capillaries in, 686
structure of, 1199
Bipolar cells of retina, 1016
Bird's nest of cerebellum, 791
Biventer cervicis muscle, 400
Biventral lobes of cerebellum, 791
Bladder, 1227
gall, 1197
urinao', 1227
in child, 1229
development of, 1212
distended, 1228
empty, 1227
female, 1230
interior of, 1231
ligaments of, 1231
IjTnphatic vessels of, 712
structure of, 1232
trigone of, 1231
vessels and nerves of, 1233
Blandin, glands of, 1131
Blastodermic vesicle, 46
Blastopore, 47
Blood, composition of, 503
corpuscles, 503
development of, 505
origin of, 505
course of, in an adult, 497
in fetus, 540
islands, 506
liquor sanguinis, 503
plasma, 503
platelets, 505
Bochdalek, corimcopia of, 798
Body or Bodies, anococcygeal,
1184
aortic, 1278
carotid, 1281
ciliary, 1010
coccygeal, 1281
geniculate, 811
Malpighian, of kidney, 1221
of spleen, 1285
olivary, 769
of penis, 1249
perineal, 1184
pineal, 1277
pituitary, 814, 1275
polar, 40
Body or Bodies, restiform, 793
of stomach, 1 163
thyroid, 1269
trapezoid, 787
of uterus, 1259
of a vertebra, 96
Body-stalk, 53, 57
Bone or Bones, 86
ankle, 266
arm, 209
articular lameUa of, 279
astragnlus, 266
atlas, 99
axis, 100
breast, 119
calcaneus, 263
calf, 260
canaliculi of, 91
cancellou« tissue of, 86
capitate, 226
carpal, 221
cells, 91
chemical composition of, 91
classes of, \'iz., long, flat, mixed
or irregular, short, 79
clavicle, 280
coccyx. 111
collar, 200
compact tissue of, 86
cranial, 129
cuboid, 269
cuneiform, of carpus, 224
of tarsus, 270
development of, 86
diploe of, 80
of ear, 1044
of elbow, 214
eminences and depressions of,
80
epistropheus, 100
ethmoid, 153
facial, 156
femur, 242
fibula, 260
flat, 79
of foot, 262
frontal, 135
hamate, 227
of hand, 221
Haversian canals of, 89
systems of, 89
hip, 231
humerus, 209
hyoid, 177
ilium, 231
incus, 1044
inferior nasal conchse, 169
innominate, 231
interparietal, 132
ischium, 234
lacrimal, 163
lesser, 164
lacunae of, 90
lamellse of, 90
lingual, 177
long, 79
of lower extremity, 231
jaw, 172
lunate, 221
lymphatics of, 89
malar, 164
malleus, 1044
mandible, 172
marrow of, 87
maxUlse, 157
medullary arterj- of, 88
membrane of, 87
metacarpal, 227
metatarsal, 272
minute anatomy of. 89
multangular, greater, 225
lesser, 225
nasal, 156
navicular, of carpus, 221
of tarsus, 270
Bone or Bones, nerves of, 88
nvmiber of, in body; 79
nutrient artery of, 88
occipital, 129
OS calcis, 263
coxa», 23 i
magnum, 226
ossification of, 91
palate, 166
palatine, 166
parietal, 133
patella, 255
pehdc, 238
perforating fibers of, 90
periosteum of, 87
lymphatic capillaries in, 684
phalanges of foot, 275
of hand, 230
pisiform, 225
pubis, 236
radius, 219
ribs. 123
sacrum, 100
scaphoid, 221, 270
scapula, 202
semilunar, 224
sesamoid, 277
shin, 256
short, 79
sphenoid, 147
sphenoidal conchse, 152
stapes, 1045
sternum, 119
strength of, compared with
other materials, 87
structure and physical proper-
ties of, 86
surfaces of. 80
sutural, 156
talus, 266
tarsal, 263
temporal, 138
thigh, 242
tibia, 256
trapezium, 225
trapezoid, 225
triangular, 224
turbinated, 169
ulna, 214
unciform, 227
of upper extremity, 200
jaw, 157
vertebra prominens, 101
vertebrae, cervical, 97
coccygeal, 106
lumbar, 104
thoracic, 102
sacral, 106
vessels of, 88
vomer, 170
Wormian, 156
zygomatic, 164
Bowman, capsule of, 1222
glands of, 996
membrane of, 1008
muscle of, 1011
Brachia conjunctiva of cere-
bellum, 792
of corpora quadrigemina, 805
pontis, 793
Brachial artery, 589
branches of, 590
peculiarities of, 590
surface marking of, 1335
cutaneous nerve, lateral, 934
medial, 937
posterior, 943
fascia, 442
plexus, 930
veins, 663
Brachialis anticus muscle, 444
muscle, 444
actions of, 444
nerves of, 444
variations of, 444
1354
INDEX
Brachiocephalic artery, 548
veins, 664
Brachioradialis muscle, 451
actions of. 456
nerves of, 456
variations of, 451
Brain, arteries of, 574
commissures of, 809
development of, 736
di'i'isions of, 766
dura of, 872
meninges of, 872
pathways from, to spinal cord,
870
pia of, 878
sensory pathways from spinal
cord to, 851
surface markings of, 1292
veins of, 652
weight of, 848
Branchial arches, 65
grooves, 65
Breadth index of skull, 198
Breast bone, 119
Breasts or mammae, 1267
development of, 1267
Bregma, 178, 198
Bregmatic fontanelle, 196
Bridge of nose, 992
Brim of pelvis, 238
Broad ligaments of uterus, 1154,
1260
Broca, cap of, 822
diagonal band of, 869
gyrus of, 822
limbic lobe of, 825
, parolfactory area of, 826
Bronchi, 10^4
divisions of, 1097
eparterial, 1097
hyparterial, 1097
intrapulmonary, 1098
left, 1085
Ivmphatic capillaries in, 686
right, 1085
Bronchial arteries, 600, 1100
nerves, 913
veins, 667, 1100
Bronchomediastinal trunks, 717, !
71S
Bronchus dexter, 1085
sinister, 1085
Brunner's glands, 1176
Bryant's triangle, 1343
Buccoe, 1112
Buccal artery, 561
branches of facial nerve, 905
cavity, 1110
glands, 1112
nerve, long, 895
Buccinator artery, 561
muscle, 384
relations of, 384
nerve, 895
Bucconasal membrane, 70
Buccopharj'ngeal fascia, 390
membrane, 47
Bulb of aorta, 545
of corpuscavernosum penis, 1248
of eye, 1000
olfactory, 826, 848
of liosterior cornu, 831
spinal, 767
vaginal, 1266
of vestibule, 1266
Bulbar arteries, obO
Bulbocavernosus muscle, 428, 430
actions of, 428, 430
Bulbospinal fasciculus, 854
Bulbourethral glands of Cowper,
1215, 1253
Bulbs of internal jugular vein, 648
Bulbus cordis, 508
oculi, 1000
olfactorius, 826
Bulbils vestibuli, 12G6
Bulla ethmoidalis, 195, 995
Bundle of His, 537
oval, 735
of Vicq d'Azyr, 810, 813, 839,
869
Burdach, tract of, 752, 763
Burns' space, 389
Bursa, omental, 1152, 1155
development of, 1100
omentalis, 1155
pharyngeal, 1141
prepatellar, 471
Bursae beneath glutseus maxi-
mus, 474
mucosa, 283
near knee-joint, 345
shoulder-joint, 319
Cacuminal lobe, 790
Calamus scriptorius, 799
Calcaneal arteries, 638, 639
lateral, 638
medial, 639
nerve, internal, 963
medial, 963
sulcus, 263
tuberosity, 266
Calcaneoastragaloid articulation,
352
ligaments, 352
Calcaneocuboid ligaments, 354
Calcaneonavicular ligaments, 355
Calcaneotibial ligament, 350
Calcaneus, 263
ossification of, 275
Calcar avis, 831
Calcarine fissure, 820
Calf bone, 260 .
Calices of kidney, 1221, 1225
Callosal convolution, 825
fissure, 825, 828
Callosomarginal fissure, 820
Camper, fascia of, 408
Canaliculi of bone, 89
dental, 1119
Canaliculus, inferior tvmpanic,
144, 181
mastoid, 144, 181
Canalis centralis cochlea;, 143
craniopharyngeus, 153
rcMniens [of Hensen], 1052, 1054
Canal or Canals, adductor, 627
Alcock's, 421
alimentarj', 1100
alveolar, 158
atrial, 508
auditory, external, 1036
carotid, 143, IM
central, of medulla spinalis, 754
of cervix of uterus, 1260
condyloid, 131
craniopharyngeal, 153, 1277
ethmoidal, 138, 154
femoral, 625
Haversian, of bone, 89
of Huguier, 141, 904, 1039
Hunter's, 627
hyaloid, 1018
hypoglossal, 131
incisive, 162, 180
infraorbital, 159
inguinal, 418
lacrimal, 1028
mandibular, 173
neural, 50
neurenteric, 50
of Xuck, 1211, 1261
of Petit, 1019
pharyngeal, ISO
pterygoid, 181
pterygopalatine, 1,59, ICS
Canal or Canals, sacral, 110
of Schlemm, 1005
semicircular, i049
membranous, 1052
spermatic, 418
spiral, of modiolus, 1051
vertebral, 110
Canales semicirculares ossei, 1049
Canaliculus innominatus of Ar-
nold, 150, note
Canalis adductorius, 627
centralis [medulla spinalis] , 754
cervicis uteri, 1260
inguinalis, 418, 1239
sacralis, 110
semicircularis lateralis, 1049
posterior, 1049
superior, 1049
Cancellous tissue of bone, 86
Canine eminence, 158
fossa, 158
teeth, 1117
Caninus muscle, 383
actions of, 383
nerves of, 383
Canthi of eyelids. 1025
Cap of Broca, 822
Capillaries, 499
bile, 1179
lymphatic, 684
structure of, 500
Capitate bone, 226
Capituluni fibulae, 260
humeri, 212
mallei, 1044
stapedis, 1045
Capsula articularis. See Indi-
vidual joints.
cricoarytcenoidea, 1087
externa, 837
extrema, 835
interna, 836
lentis, 1019
vasculosa lentis, 1003
Capsular artery, middle, 610
Capsule, adipose, of kidney, 1220
adrenal, 1278
of Bowman, 1221
of brain, 835, 836, 837
of Glisson, 1157, 1194
of lens, 1019
of Tenon, 1024
Caput caecum coli, 1177
femoris, 243
humeri, 209
pancreatis, 1200
tali, 267
Cardiac cycle, 53S
ganglion of Wrisberg, 984
glands of stomach, 1166
muscular tissue, 536
nerves, cervical, 912
from sympathetic, 979
from vagus, 912
great, 979
inferior, 912
middle, 979
superior, 912
thoracic, 912
notch, 1096
orifice of stomach, 1161
plexus of nerves, 984
veins, 642
Cardinal veins, 520
Caroticoclinoid foramen, 151, 191
ligament, 153
Caroticotympanic artery, 568
nerve, 1047
Carotid arch, 516
arterj-, common, 549
branches of (occasional) ,
551
peculiarities of, 551
surface markings of, 1302
external, 551
INDEX
1355
Carotid artery, external, branches
of, 552
surface markings of, 1302
internal, 566
branches of, 568
peculiarities of, 567
bodies, 1281
canal, 143, 181
ganglion, 977
glands, 1281
groove, 148, 191
nerve, internal, 977
nerves from glossopharyngeal,
909
plexus, 977
internal, 977
sheath, 389
triangles, 5G4
Carpal arteries from radial, 594
from ulnar, 598
bones, 221
net-work, 594
Carpometacarpal articulations,
330
Carpus, 221
articulations of, 328
ossification of, 230
surface form of, 1327
Cartilage or Cartilages, articular,
280
arytenoid, 1075
of auricula, 1034
cells, 279
corniculate, 1075
costal, 127, 281
cricoid, 1074
cuneiform, 1075
of epiglottis, 1075
epiphysial, 93
ethmo vomerine, 171
histology of, 279
hyaline, 279
intrathyroid, 1074
lacunae, 280
of larynx, 1073
structure of, 1076
lateral, 993
of nose, 992, 993
Meckel's, 66, 174
parachordal, 84
permanent, 279
of pinna, 1034
of Santorini, 1075
of septum of nose, 993
sesamoid, 993
temporarv, 280
thyroid, 1073
trabecules cranii, 84
of trachea, 1086
vomeronasal, 996
white fibro-, 279, 281
of Wrisberg, 1075
Cartilagines alares minores, 993
arytccnoidece , 1075
corniculatcp. 1075
costales, 127
cuneiformes, 1075
laryngis, 1073
nasi, 992
Cartilaginous ear capsules, 85
vertebral column, 82
Cartilago alaris major, 993
cms laterale, 993
mediale, 993
auricula;, 1034
cricoidea, 1074
epiglottica, 1075
nasi lateralis, 993
septi nasi, 992
thyreoidea, 1073
triticca, 1077
Caruncula lacrimalis, 1028
Carunculce hymenales, 1266
Cauda equina, 750
helicis, 1034
Cauda pancreatis, 1201
Caudal fold of embrvo, 53
Caudate lobe of liver, 1192
nucleus, 833
process of liver, 1192
Caudatum, S33
Cavernous arteries, 568
nerves of penis, 989
plexus, 978
portion of urethra, 1235
sinuses, 658
nerves in, 900
spaces of penis, 1250
Cavity or Cavities, amniotic, 56
body or celom, 50
buccal, 1110
cotyloid, 237
glenoid, 207
of lesser pelvis, 239
mediastinal, 1090, 1092
of mouth proper, 1110
nasal, 194, 994
oral, 1110
peritoneal, 1150
of septum pellucidum, 840
sigmoid, of radius, 220
of ulna, 215
subarachnoid, 876
subdural, 875
of thorax, 524
tympanic, 1038
of uterus, 1260
Cavum conchtp, 1034
laryngis, 1078
Meckelii, 886
nasi, 194, 994
oris, 1110
proprium, 1110
septi pellucidi, 840
suharachnoideale, 876
tympani, paries carotica, 1042
labyrinthica, 1040
mastoidea, 1042
tympanum, 1037
paries jugularis, 1038
7nembranacea, 1038
tegmentalis, 1038
uteri, 1260
Cecal arteries, 607
fossa;, 1160
Cecum, 1177
lymphatic vessels of, 710
Celiac artery, 603
axis, 603
branches of vagus nerve, 913
ganglion, 985
plexus, 985
Cell or Cells, animal, 35
basket, of cerebellum, 796
of Betz, 845
of bone, 91
centro-acinar, of Langerhans,
1204
chromaffin, 1277
clasmatocytes, 377
of Claudius, 1058
definition of, 35
of Deiters, 1058
divisions of, 37
of Dogiel, 921
enamel, 1123
germinal, of medulla spinalis,
733
giant, 88
of Betz, 845
of Golgi, 845
of fundus glands, 1166
granule, 377
gustatory, 991
of Hensen, 1058
lamellar, 377
of Martinotti, 845
mass, inner, 46
intermediate, 50
Mastzelien, 377
Cell or Cells, membrane, 36
nerve, 721
nucleus of, 36
olfactory, 996
pigment, 377
plasma, 377
of Purkinje, 794
reproduction of, 37
of Sertoli, 1243
of spinal ganglia, 730, 919
splenic, 1284
structure of, 35
wandering, 377
Cella, 829
Celluhe ethmoidales, 998
Cement of teeth, 1120
formation of, 1124
Centers of ossification, 93
visual, 814
Central artery of retina, 571
canal of medulla spinalis, 754
cells of fundus glands, 1166
fissure, 819
gray stratum of cerebral aque-
duct, 806
ligament of medulla spinalis,
879
lobe, 825
nervous system, 721
part of lateral ventricle, 829
sulcus, 819
tendinouspoint of perineum, 427
tendon of diaphragm, 406
tract of cranial nerves, 805
of trigeminal nerves, 805
Centrifugal nerve fibers, 729
Centriole, 37
bodies of ovum, 40
of spermatozoon, 42, 43
Centripetal nerve fibers, 729
Centroacinar cells oi Langerhans,
1204
Centrosome, 37
Centrosphere, 37
Centrum ovale majus, 828
minus, 827
Cephalic flexure of embryonic
brain, 737
fold of embryo, 53
index, 198
portion of sympathetic system,
977
vein, 661
accessory, 662
Ceratohyal of hyoid bone, 178
Cerebellar arteries, 5s0
fasciculus, direct, 758
notches, 788
peduncles, 793
tract, direct, 761, 778
of Flechsig, 761
veins, 652
Cerebellum, 788
brachia conjunctiva, 792
pontis, 793
development of, 740
fibra; proprice, 794
gray substance of, 794
lobes of, 788
nucleus dcntatus, 796
peduncles of, 793
structure of, 791
surfaces of, 789, 790
vermis of, 788
white substance of, 791
Cerebral arteries, anterior, 571
middle, 572
posterior, 580
aqueduct, 806
cortex, nerve cells of, 845
fibers of, 846
structure of, 845
types of, 847
fissure, lateral, 819
hemispheres, 817
135G
INDEX
Cerebral hemispheres, borders of,
818
development of, 744
fibers of, association, 843
commissural, 843
projection, 843
transverse, 843
fissures of, 819
gray substance of, 845
gyri of, 821
interior of, 827
lobes of, 821, 822
localization of, 849
nerves, 881. See Cranial
nerves,
poles of, 818
structure of, 842
sulci of, 819, 820, 821
surfaces of, 818
white substance of, 842
peduncles, 800
structure of, 800
veins, 652
ventricles, 797. 815, 829
Cerebrospinal fasciculus, 759, 760
fibers of internal capsule, 836
fluid. 880
Ceruminous glands, 1037
Cervical artery, ascending, 581
deep. 585
superficial, 582
transverse, 582
branch of facial nerve, 905
cardiac nerves, 912
enlargement of medulla spin-
alis, 752
fascia, 388
flexure of embryonic brain, 131
ganglion, 978, 979. 980
lymph glands, 697
muscles, lateral. 388
nerve, cutaneous or transverse,
927
of facial, 905
nerves, 921
divisions of, anterior, 925
posterior, 921
pleura, 1088
plexus, 925
branches of, 926. 927
portion of svmpathetic, 978
rib, 102. 128
veins, 651
vertebr£B, 97
Cervicalis ascendens muscle, 399
Cervix uteri, 1259
portio supravaginalia, 1259
vaginalis, 1260
of uterus, 1259
Chambers of eye. 1012
Check ligaments, 296
of eye, 1024
Cheeks, 1112
Chest, 117
Chiasma, optic, 814, 883
oplicum, 814. 883
Chiasmatic groove. 147. 190
Choanae. 180, 196, 994
Chondrin, 282
Chondrocranium, 84
Chonc^ro-epitrochlearis muscle,
437
Chondroglossus muscle, 1130
Chondromucoid, 2S2
Chondrosternal ligament, 302
intra-articular, 303
Chondroxiphoid ligaments, 304
Chorda ohliqua, 325
tympani nerve. 904
ChordcB tendinecc [left ventricle],
535
[right ventricle], 532
Willisi. 655
Chordal furrow, 52
portion of base of skull, 84
Chorioidea, 1009
lamina choriocapillaris, 1010
vasculosa, 1010
Chorion, 60
frondosum. 62
lajve. 61
Chorionic villi. 60
Choroid artery, 574
coat of eyeball, 1009
structure of, 1010
plexuses of fourth ventricle, 798
of lateral ventricle, 840
of third ventricle, 815
vein, 653
Choroidal artery, anterior, 574
posterior, 581
fissure, 841, 1002
Chromaffin cells, 1277
Chromaphil and cortical systems,
1277
development of. 1277
Chromatin. 36
Chromatolysis. 724
Chromosomes, 37
Chyle, 683
Chvliferous vessels. 683
Cilia, 1025
Ciliaris muscle. 1010
Ciliary arteries. 571
body. 1010
ganglion. 888
glands. 1025
muscle, 1011
nerves, 888
processes, 1010
Cingulate gyrus, 825
sulcus, 820
Cingulum of cerebral hemisphere.
843
of teeth, 1116
Circle, arterial, of Willis, 574
Circular folds of small intestine,
1173
sinus, 659
sulcus, 821, 825
Circulating fluids, 503
Circulation of blood in adult, 497
in fetus, 540
Circnlus arteriosus major, 1014
minor, 1014
major [iris], 571, 1014
minor [iris], 571, 1014
venosus [mamma], 1268
Circumduction, 286
Circumferential fibrocartUage. 282
Circumflex arteries, femoral. 630
humeral. 589
nerve, 934
Circuminsular fissure, 821
Circumvallate papilliE, 1126
Cisterna basalis, 876
cht/li, 691
cerebellomedullaris, 876
chiasmatis, 877
fossa; cerebri lateralis, 877
inter peduncular is, 876
magna, 876
pontis, 876
vena magnce cerebri, 877
Cisternse subarachnoid. 876
subarachnoidales, 876
Clarke's column, 758
Clasmatocytes, 377
Claudius, cells of, 1058
Claustrum, 835
Clava, 774
Clavicle, 200
ossification of, 202
peculiarities of, in sexes, 202
structure of, 202
surface anatomy of, 1326
Clavicula, 200
Cla\apectoral fascia, 437
Cleft palate, 199
CleJdohyoideus muscle, 393
Clinging fibers of cerebellum, 79(>
Clinoid processes, anterior, 151,
190
middle, 147, 190
posterior. 147. 190
Clitoris. 1266
frenulum of, 1266
glans of, 1266
nerves of, 968
prepuce of, 1266
Clivus of sphenoid, 148
monticuli of cerebellum. 790
Cloaca, ectodermal, 1109
entodermal, 1109 ,
pelvic portion of, 1212
phallic portion of, 1213
vesicourethral portion of, 1212
Cloacal duct, 1109
membrane, 1109
tubercle, 1213
Cloquet, lymph gland of. 703
Closing membranes. 65
Coarctation of aorta. 547
Coccvgeal arteries. 620
body. 1281
cornua. Ill
gland. 1281
nerve, division of, anterior, 957
posterior. 925
plexus. 968
Coccygeus muscle. 424
actions of, 424
nerves of, 424
Coccyx, 111
ossification of, 114
Cochlea, 1050
aqueduct of, 144, 181
cupula of, 1050, 1051
hamulus Iqmince spiralis, 1051
helicotrema of, 1051
modiolus of, 1050
scalte of, 1051
spiral canal of, 1051
lamina of, 1051
vessels of, 1059
Cochlear arterv, 1059
nerve, 906, 1059
composition and central con-
nections of, 857
nuclei, 788, 906
root of acoustic nerve, 906
Cochleariform process, 145, 1042
Cog-tooth of malleus. 1044
Cohnheim. areas of, 374
Colic arteries of ileocolic. 609
left, 610
middle, 609
right. 609
flexures, right and left, 1180
impression, 1189
valve, 1179
Collar bone, 200
Collateral circulation. 543
eminence. 833
fissure. 820
ganglia, 977
Collecting tubes of kidney. 1223
CoUes. fascia of. 235, 409. "426
Colliculi. inferior. 805, 806
superior, 805, 806
Colliculus of arj'tenoid cartilage,
1075
facialis, 799
inferior, 806
nervi optici, 1015
superior, 806
Collum anatomicum, 209
femoris, 243
mallei, 1044
tali, 269
Coloboma, 1002
Colon, 1180
ascndens, 1180
ascending, 1180
des'.endens, 1181
INDEX
1357
Colon, descending, 1181
iliac, 1182
left or splenic ftexure of, 1181
pelvic, 1182
right or hepatic flexure of, 1180
sigmoid, 1182
sifimoideum, 1182
structure of, 1184
tela submucosa, 1186
transverse, 1180
iransversu m, 11 80
tunica mucosa, 1186
muscularis, 1185
serosa, 1184
vessels and nerves of, 1187
Colored lines of Retzius, 1120
or red corpuscles, 503
Colorless corpuscles, 504
Colostrum corpuscles, 1268
Columna anterior [medulla spin-
alis]. 753
fornicis, 838
lateralis [medulla spinalis], 753
nasi, 992
posterior [m.edulla spinalis], 753
vertebralis, 96
Columna; carneo', 532
Columns of Clarke, 758
of fornix, 838
of medulla spinalis, 756, 757,
758
rectal, of Morgagni, 1185
renal, 1221
of vagina, 1264
vertebral, 90, 114
Comes nervi phrenici, 584
Comitans nervi ischiadici, 620
Comma-shaped fasciculus, 764
Comniissura laborium anterior,
1265
palpebrarum lateralis, 1025
medialis, 1025
Commissural fibers of cerebral
hemispheres, 843
Commissure of brain, 809
anterior, 747, 840
middle or gray, 809
posterior, 743, 812
of corpus callosum, 747
habenular, 812
hippocampal, 838, 869
of Gudden, 814
of labia majora, 1265
of medulla spinalis, anterior
and posterior gray, 754
anterior white, 752
optic, 814
Commissures, palpebral, 1025
Common bile duct, 1198
lymphatics of, 711
carotid artery, 549
dental germ, 1122
iliac arteries, 613
glands, 704
veins, 677
integument, 1062
interosseous artery. 596
peroneal nerve, 694
Communicans fibularis nerve, 694
tibialis nerve, 962
Communicantes cervicales nerves,
928
Communicating arterv, anterior,
571
from dorsalis pedis, 637
f)osterior, 573
Compact tissue of bone, 86
Comparison of bones of hand and
foot. 276
Complexus muscle, 400
Cojnposition and central connec-
tions of cranial nerves,
855
of spinal nerves, 849
Compressor naris muscle, 382
Concha of auricula, 1034
nasal, inferior, 169
articulations of, 170
ossiffication of, 170
middle, 156
superior, 156
nasalis inferior, 169
Concha?, sphenoidal, 152
sphenoidales, 152
Conchal crest, 160, 167
Condyle of mandible, 174
Condyles of femur, 247
occipital, 131
of tibia, 256
Condj'loid articulation, 286
canal, 131
foramen, anterior, 131
fossa, 131, 181
process of mandible, 174
Cone of attraction, 45
bipolars of retina, 1017
granules of retina, 1017
of origin of axon, 724
Cones of retina, 1017
Confluence of sinuses, 131, 658
Confluens sinuum, 658
Coni vasculosi, 1244
Conical papillse, 1127
Conjoined tendon of internal
oblique and transversalis
muscles, 414
Conjugate diameter of pelvis, 239
Conjunctiva, 1026
Connecting fibrocartilages, 282
Connective tissue, extraperitoneal ,
418
Conoid ligament, 315
tubercle, 200
Constriction,duodenopyloric,1162
Constrictor muscles, 1142
pharyngis inferior muscle, 1142
medius muscle, 1143
superior muscle, 1143
urethra; muscle, 429, 431
Conus arteriosus, 531
elasticus [larynx], 1078
rnedullaris, 749
Convoluted tubes of kidney, 1223
Convolution, callosal, 825
frontal, ascending, 821
"occipitotemporal, 823
parietal, ascending, 823
Cooper, ligament of, 412
Copula, 1103
Cor, 526
Coracoacromial ligament, 316
Coracobrachialis muscle, 443
actions of, 444
nerves of, 444
variations of, 443
Coracoclavicular fascia, 437
Coracohumeral ligament, 317
Coracoid process, 207
tuberosity, 200
Cord, gangliated, 976
spermatic, 1239
spinal, 749
umbilical, 57
vocal, false, 1079
inferior, 1080
superior, 1079
true, 1080
Corium or cutis vera, 1065
layers of, 1065
stratum papillare, 1065
reticulare, 1065
Cornea, 1006
structure of, 1007
Corneal corpuscles. 1008
endothelium, 1009
epithelium, 1007
spaces, 1008
Corniculate cartilages, 1075
Cornu anterius, 830
inferior, 831
Cornu of medulla spinalis, 753
posterius, 831
Cornua of coccyx, 111
of hyoid bone, 178
of lateral ventricles, 830, 831
majora [os hyoidei], 178
7ninora [os hyoidei], 178
of sacrum, 108
of thyroid cartilage, 1073, 1074
Cornucopia of Bochdalek, 798
Corona glandis, 1249
radiata [brain], 837
[ovum], 40
Coronal suture, 178, 183
Coronary artery of heart, 546
peculiarities of, 547
of lips, 555
of stomach, 603
ligament of liver, 1150
ligaments of knee, 343
plexuses, 985, 987
sinus, 642
opening of, 530
sulcus of heart, 526
veins, 642
of stomach, 682
Coronoid fossa, 212
process of mandible, 174
of ulna, 214
Corpora cavernosa clitoridis, 1266
penis, 1248
bulbs of, 1248
crura of, 1248
mammillaria, 813
guadrigemina, 805
brachia of, 805, 806
structure of, 806
Corpus albicantia, 813
Arantii, 533
callosum, 818, 828
development of, 747
genu of, 828
peduncle of, 827
rostrum of, 828
splenium of, 828
cavernosum, artery to, 620
urethra', 1247
ciliare, 1010
fern oris, 246
fibultr, 260
fornicis, 838
geniculatum laterale, 811
mediate, 811
Highmori, 1243
humeri, 209
incudis, 1044
luteum, 1256
maxilla!, 158
OSS. hyoidei, 177
ilii, 231
ischii, 234
pubis, 235
pancreatis, 1201
papillare [corium], 1065
penis, 1249
pineale, 812
radii, 219
sphenoidale, 147
spongiosum, 1248
sterni, 120
striatum, 833
vein of, 838
subthalamicum , 812
tali, 267
tibia, 257
ulna, 215
uteri, 1259
vertebra', 96
vitreum, 1018
Corpuscles, colored, 503
development of, 505
colorless, 504
genital, 1060
of Golgi and Mazzoni, 1061
of Grandry. 1060
1358
INDEX
Corpuscles of Hassall, 1274
of Herbst, 1061
Pacinian, lOGO
of Ruffini, 1061
of Wagner and Meissner,
1061
Corrugator cutis ani muscle, 425
muscle, 381
actions of, 381
nerves of, 381
supercilii muscle, 381
Cortex of cerebellum, 794
of cerebrum 845
Corti. ganglion of, 1051, 1059
organs of, 1056
pillars or rods of, 1056
spiral organ of, 1056
tunnel of, 1057
Cortical arches of kidney, 1221
arterial system of brain, 574
portion of suprarenal gland,
1280
substance of kidney, 1221
of lens, 1020
visual center, 882
Corticostriate fibers, 835
CostoE, 123
Costal cartilages, 127, 280
element or process, 98
groove, 124
pleura, 1088
tuberosity, 202
Costocentral articulation, 299
Costocervical trunk, 585
Costochondral articulations, 304
Costocoracoid ligament, 437
membrane, 528
Cortocoracoidcus muscle, 437
Costomediastinal sinus, 1090
Costosternal articulations, 302
Costotransv^erse articulations, 300
ligaments, 302
Costovertebral articulations, 299
ligament, anterior, 299
Cotyloid cavity, 237
ligament, 237, 436
Covering bones, 85
Coverings of ovum, 40
of testes, 1236
Cowper's glands, 1213, 1253
Coxal articulation, 333
movements of, 338
muscles in relation to, 338
Cranial arachnoid, 876
bones, 129
dura mater, 872
fossa, anterior, 190
middle, 190
posterior, 190, 192
nerves, 881
abducent, 899
accessory, 913
acoustic, 905
composition and central con-
nections of, 855
development of, 748
facial, 901
glossopharyngeal, 906
hypoglossal, 914
oculomotor, 884
olfactory, 881
optic, 882
tracts of, 804, 805
trigeminal, 886
trochlear, 885
vagus, 910
pia mater, 879
sympathetics, 970
Craniology, 197
Craniopharyngeal canal, 1277
Cranium, 128
bones of, 128, 129
breadth of, 198
development of, 83
height of, 198
Cranium, horizontal circumfer-
ence of, 198
length of, 198
longitudinal arc of, 198
Cremaster muscle, 414
Cremasteric artery, 623
fascia, 414
Crescents of Gianuzzi, 1136
Crest or Crests, basilar, 1054
conchal, 159, 167
ethmoidal, 161, 167
frontal, 136
of ilium, 234
incisor, 163
infratemporal, 150, 183
internal occipital, 131, 193
intertrochanteric, 246
lacrimal, 161, 164
nasal, 163, 167
neural, 51, 736
obturator, 236
of pubis, 236
of right atrium, 529
sphenoidal, 149
supramastoid, 139
of tibia, 257
of tuVjercles of humerus, 209
urethral, in female, 1236
in male, 1234
Cribriform plate of ethmoid, 153
CricoarytEPnoideus lateralis mus-
cle, 1082
posterior muscle, 1082
Cricoarytenoid ligament, 1078
muscles, 1082
Cricoid cartilage, 1074
Cricothyreoideus muscle, 1081 .
Cricothyroid artery, 552
ligament, middle, 1078
membrane, 1078
muscle, 1081
Cricotracheal ligament, 1077
Crista arcuata [arytenoid car-
tilage], 1075
colli costce, 123
falciformis, 143
gain, 153
terminalis [of His], 509
vestibuli, 1047
Crossed commissural fibers, 755
pyramidal tract, 760
Crosses of Ranvier, 727
Crown of a tooth, 1117
Crucial anastomosis, 630
ligaments, 342
Cruciate crural ligament, 488
eminence of occipital bone, 130
ligament of atlas, 295
ligaments of knee, 342
Crura cerebri, 800
of diaphragm, 405
of fornix, 840
of penis, 1248
of stapes, 1045
of subcutaneous inguinal ring,
410
Crural arch, deep, 419
nerve, anterior, 955
septum, 626
sheath, 625
Crureus muscle, 471
Crus cerebri, 800
commune [semicircular canals],
1049
■ fornicis, 840
helicis, 1034
penis, 1248
Crusta or pes of cerebral peduncle,
802
petrosa of teeth, 1120
formation of, 1120
Cruveilhier, glenoid ligaments of,
332, 359
Crypts of Lieberkuhn, 1174
Crystalline lens, 1019
Crystalline lens, cortical sub-
stance of, 1020
development of, 1002
nucleus of, 1020
Cuboid bone, 269
Cuboideonavicular articulation,
356
Culmen monticuli [cerebellum], 789
Cuneate nucleus, 774
tubercle, 774
Cuneiform bone of carpus, 225
of tarsus, first, 270
second, 271
third, 271
cartilages, 1075
tubercle, 1079
Cuneocuboid articulation, 357
Cuneonavicular articulation, 356
Cuneus, 823
Cup, optic, 1001
Cupula of cochlea, 1051
of pleura, 1088
Curvatura ventriculi major, 1162
minor, 1162
Curvatures of stomach, 1162
Curved lines of ilium, 232, 233
Curves of vertebral column, 114
Cushion of auditory tube, 1141
of epiglottis, 1076
Cushions, endocardial, 512
Cusps of bicuspid valve, 534
of tricuspid valve, 531
Cutaneous cervical nerve, 927
nerve, external, 953
internal, 937, 955
lesser, 937
middle, 955
Cuticle, 1062
Cuticula dentis, 1123
Cutis plate, 80
vera or corium, 1065
Cutting teeth, 1115
Cuvier, ducts of, 520
Cycle, cardiac, 538
Cymba conchas, 1034
Cystic artery, 605
duct, 1198
vein, 682
Cyton, 723
Cytoplasm, 35
Cytotrophoblast, 47
Dacryon, 189, 1198
Dartos tunic, 1238
Darwin, auricular tubercle of,
1033
Daughter chromosomes, 37
Decidua, 59
basalis, 60
capsularis, 60
parietalis, 60
placentalis, 60
stratum compactum of, 59
spongiosum of, 00
unaltered or boundary layer of,
60
Decidual cells, 59
Decussation of lemniscus, 777
of optic nerves, 883
pyramidal, 767
sensory, 777
Deep abdominal ring, 418
artery of penis, 617
auricular artery, 560
cerebral veins, 653
cervical artery, 585
fascia, 388
lymph glands, 697
vein, 651
crural arch, 419
epigastric artery, 623
vein, 672
INDEX
1359
Deep external pudic artery, 629
fascia of arm, 442
of forearm, 445
femoral artery, 629
iliac circumflex vein, 673
lingual artery, 553
muscles of back, 396
palmar arch, 595
peroneal nerve, 965
petrosal nerve, 892
plantar artery, 637
Sylvian vein, 653
temporal arteries, 561
nerves, !S95
transverse fascia of leg, 483
Degeneration, Wallerian, 759
Deglutition, 1140
Deiters, cells of, 1058
nucleus of, 788, 803
Deltoid ligament, 350
muscle, 439
tuberosity, 211
Deltoideus muscle, 439
actions of, 440
nerves of, 440
variations of, 440
Demilunes of Heidenhain, 1136
Demours, membrane of, 1008
Dendrons of nerve cells, 723
Dens, or odontoid process of axis,
99
serotinus, 1118
Dental artery, inferior, 561
posterior, 562
canaliculi, 1119
forniulte, 1114
furrow, 1122
germs, 1122
lamina, 1122
nerve, inferior, 896
pulp, 1118
sac, 1123
Dentate fissure, 826
gyrus, 827, 868
ligament, 880
Denies, 1112
canini, 1116
decidui, 1118
incisivi, 1115
molares, 1118
permanentes, 1115
prcemolares, 1118
Dentin, 1119
formation of, 1123
intertubular, 1120
secondary, 1120
Dentinal canaliculi, 1119
fibers, 1119
matrix, 1119
sheath of Neumann, 1119
tubules, 1109
Depressions for arachnoid granu-
lations, 134
Depressor alae nasi muscle, 3S2
anguli oris muscle, 381
labii inferioris muscle, 383
septi muscle, 382
actions of, 382
nerves of, 382
Dermal bones, 85
Dermic coat of hair follicle, 1076
Dermis, 1065
Descemet, membrane of, 1008
Descendens cervicalis nerve, 928
Descending aorta, 598
colon, 1181
comma-shaped fasciculus, 764
oblique muscle, 409
palatine artery, 562
process of lacrimal bone, 164
ramus of hypoglossal nerve, 918
of ischium, 235
of OS pubis, 237
Descent of testis, 1210
Detrusor urinae muscle, 1233
Deutoplasm, 39
Development of allantois, 54
of amnion, 5()
of anal canal, 1108
of arteries, 515
of body cavities, 72
of bone, 86
of brain, 736
of branchial or visceral arches,
65
of chorion, 60
of chromaphil and cortical sys-
tems, 1277
of cranial nerves, 748
of deciduous teeth, 1122
of dienccphalon, 742
of digestive tube, 1101
of ear, 1029
of external organs of genera-
tion, 1213
of eye, 1001
of face, 67
of fetal membranes, 54
of heart, 500
of hypophysis cerebri, 1276
of joints, 283
of kidney, 1211
of limbs, 71
of liver, 1193
of lymphatic system, 768
of mamm», 1101
of medulla spinalis, 749
of mouth, 1101
of muscles, 371
of nervous system, 733
of neural groove and tube, 50
of nose, 67
of notochord, 52
of ovaries, 1207
of palate, 70
of palatine tonsils, 1103
of pancreas, 1202
of parathyroid glands, 1272
of permanent teeth, 1124
of pharyngeal pouches, 65
of placenta, 62
of primitive segments, 52
streak, 47
of prostate, 1213
of rectum, 1108
of respiratory organs, 1071
of ribs, 82
of salivary glands, 1102
of skeleton, 80
of skin, 1066
of skull, 83
of spinal nerves, 735
of spleen, 1282
of sternum, 83
of suprarenal glands, 1278
of teeth, 1121
of testis, 1210
of thymus, 1273
of thyroid gland, 1270
of tongue, 1102
of umbilical cord, 57
of urethra, 1215
of urinary bladder, 1212
and generative organs, 1205
of vascular system, 505
of veins, 518
of venous sinuses of dura mater,
522
of vertebral column, 80
of visceral arches, 65
of yolk-sac, 54
Diagonal band of Broca, 869
Diameters of pelvis, 239, 240
Diaphragm, lymphatic vessels of,
717
muscles of, 404
actions of, 406
nerves of, 406
variations of, 406
pelvic, 420, 1147
Diaphragm, urogenital, 428
Diaphra/jma selhe, 874
Diaphragmatic lymph glands, 715
part of pelvic fascia, 421
pleura, 1088
surface of heart, 529
Diarthroscs, 285
Diaster, 37
Diencephalon, 807
development of, 742
Digastric fossa, 141
muscle, 391
nerve from facial, 905
triangle, 564
Digastricus muscle, 391
actions of, 393
nerves of, 393
variations of, 392
Digestion, organs of, 1100
Digestive apparatus, 1100
development of, 1101
tube, 1100
Digital arteries of foot, 640
from superficial volar arch,
598
of hand, 598
fossa of epididymis, 1242
of femur, 244
nerves of lateral plantar, 963
of medial plantar, 963
of median, 938
of musculocutaneous, 937
of radial, 943
of ulnar, 939
vaginal ligaments, 449
veins of foot, 669
of hand, 660
Digits, articulations of, 333
Dilatator naris anterior muscle,
382
action of, 382
nerves of, 382
posterior muscle, 382
action of, 382
nerves of, 382
pupillffi muscle, 1013
tubse muscle, 1044
Diploe, 80
Diploic veins, 651, 652
Direct cerebellar fasciculus, 758
tract, 778
of Flechsig, 761
pyramidal tract, 759
Discharge of ovum, 1256
Discus articularis, 298
proligerus, 1256
Disk, interpubic, 311
optic, 1015
Disks, tactile, of Merkel, 1059
Diverticulum ilei, 1172
Meckel's, 54, 1172
Divisions of bronchi, 1197
of cells, 37
Dobie's line, 375
Dogiel, cells of, 921
Dorsal aortse, 517
artery of penis, 620
carpal artery, of radial, 594
of ulnar, 598
ligament, 458
cutaneous nerves, 963, 966
fissure of medulla oblongata, 767
interossei muscles, 464, 495
interosseous artery, 596
nerve, 944
lamina, 735
mesogastrium, 1103
metacarpal arteries, 594
veins, 663
nasal artery ^^ 571
nerve of penis, 968
peripheral band, 764
pulmonary nerves, 913
scapular nerve, 932
spinal artery, 579
13G0
INDEX
Dorsal veins of ponis, 676
venous arch of foot, 669
net-work of hand, 660
vestibular nucleus, 788
Dorsalis hallucis artery, 637
lingucc artery, 555
pedis artery, 636
branches of, 637
peculiarities of, 636
relations, 636
surface markings of, 1346
scapula', artery, 588
Dorsoepitrochlearis brachii mus-
cle, 434
Dorsomedian fissure of medulhi
oblongata, 767
Dorsum ilii, 232
lingua:, 1125
nasi, 992
sella, 147, 190
of tongue, 1125
Douglas, pouch of, 1152
Drum, 1037
Duct or Ducts, accessory pan-
creatic, 1202
of Bartholin, 1136
of Bellini, 1223
of bulbourethral glands, 1253
cloacal, 1109
common bile, 1198
of Cuvier, 520
cystic, 1198
ejaculatory,- 1247
frontonasal, 138
of Gartner, 1255
hepatic, 1197
lacrimal, 1028
lactiferous, 1268
of liver, 1197
lymphatic, right, 691
Miillerian, 1206
nasolacrimal or nasal, 1029
pancreatic, 1202
parotid, 1134
pronephric, 1205
prostatic, 1253
orifices of, 1234
of Rivinus, 1136
of Santorini, 1202
semicircular, 1052
seminal, 1245
Skene's, 1213
Stensen's, 1134
sublingual, 1136
submaxillary, 1135
thoracic, 690
thyroglossal, 1126, 1270
vitelline, 54
Wharton's, 1135
of Wirsung, 1202
Wolffian, 1205
Ductless glands, 1269
parathyroids, 1271
spleen, 1282
suprarenals, 1278
thymus, 1273
thyroid, 1209
Ductuli aberrantcs [testis], 1246
efferentes [testis], 1244
t ransver si [epoophoTon], 1255
Ductus arteriosus, 540
choledochus, 1198
cochlcaris, 1054
cysticus. 1198
deferens. 1245
ampulla of, 1246
structure of, 1246
ejaculatorii, 1247
endolymphaticus, 1048, 1052
hepaticus, 1197
lacrimalis, 1028
longitudinalis epoiiphori, 1255
lymphaticus dexter, 691
nasolacrinialis , 1029
pancreaticus [Wirsunoi], 1202
Ductus parotideus, 1134
Santorini, 1202
semicircular es, 1052
submaxillar is, 1135
thoracicus, 690
utriculosaccularis , 1052
venosus, 519, 542
development of, 519
fossa for, 1191
obliterated, 681
Duodenal fossie, 1159
glands, 1170
impression, 1190
Duodenojejunal flexure, 1169
fold, 1159
fossa, 1159
Duodenomesocolic fold, 1159
Duodenopyloric constriction,
1162
Duodenum, 1168
ascending portion, 1169
descending portion, 1169
horizontal portion, 1169
lymphatic vessels of, 710
superior portion, 1169
suspensory muscle of, 1170
vessels and nerves of, 1170
Dura mater, cranial, 872
arteries of, 872
endosteal layer of, 875
meningeal layer of, 875
nerves of, 875
processes of, 873
veins of, 875
encephali, 872
spinal, 875
structure of, 876
spi7ialis, 875
venous sinuses of, develop-
ment of, 522
Dural nerve, 911.
E
Ear, 1029
auricula of, 1033
muscles of, 1035
cartilaginous capsules of, 85
cochlea, 1050
development of, 1029
external, 1033
internal, or labyrinth, 1047
meatus acusticus externus,
1036
membranous labyrinth, 1051
middle, 1037
osseous labyrinth, 1047
pinna of, 1033
semicircular canals of, 1049
tympanic cavity of, 1037
muscles of, 1046
ossicles of, 1044
vessels and nerves of,
1040
vestibule of, 1047
Eberstaller, medial frontal sulcus
of, 822
Ectoderm, 47
Ectodermal cloaca, 1109
Efferent nerves, 729
Eighth nerve, 905
Ejaculator urinte muscle, 428
Ejaculatory ducts, 1247
Elastic fibrocartilage, 282
laminae of cornea, 1008
membrane of larynx, 1077
Elbow bone, 214
Elbow-joint, 321
anastomoses around, 592
movements of, 322
surface anatomy of, 1328
markings of, 1331
vessels and nerves of, 322
Eleventh nerve, 313
Embryo, form of, at different
stages, 74
separation of, 53
Embryology, 38
Embryonic disk, 47
pole, 46
Eminence, canine, 158
collateral, 833
cruciate, 130
frontal, 135, 178, 183
hypothenar, 456
iliopectineal, 234
intercondyloid, of tibia, 256
medial, of rhomboid fossa, 799
parietal, 133, 178, 183
pyramidal, of pons, 785
of tympanic cavity, 1042
thenar, 456
Eminences and depressions of
bones, 80
Eminentia arcuata, 142
articularis, 139
collateralis, 833
pyramidalis, 1042
saccularis, 813
Emissary veins, 660
Enamel cells, 1123
droplet, 1123
epithelium, 1123
fibers or prisms, 1120
organ, 1123
of teeth, 1120
formation of, 1123
Enarthrosis, 286
Encephalon, 766
End-arteries, 1223
End-bulbs of Krause, 1060
End-plates, motor, of Kiihne, 730
Endocardial cushions, 512
Endocardium, 535
Endognathion, 199
Endolymph, 1051
Endomysium, 373
Endoneurium, 728
Endosteal layer of dura mater,
875
Endothelium, corneal, 1009
Enlargements of medulla spinalis,
751
Ensiform appendix, 121
Entoderm, 47
Entodermal cloaca, 1109
Entrance of larynx, 1079
Eosinophil corpuscles, 504
Eparterial branch of right bron-
chus, 1085, 1097
Ependymal layer, 733
Epicardium, 535
Epicondyles of humerus, 212
Epicranial aponeurosis, 380
Epidermic coat of hair follicle,
1068
Epidermis, development of, 1066
structure of, 1062
Epididymis, 1242
Epidural space, 875
Epigastric artery, deep or in-
ferior, 623
peculiarities of, 623
surface markings of, 1321
superficial, 629
superior, 5.S5
lymph glands, 704
region, 1149
vein, deep, 762
inferior, 672
Epiglottis, 1075
tubercle or cushion of, 1076
Epimysium, 373
Epineurium, 728
Epiotic center of temporal bone,
146
Epiphyses, atavistic, 95
j pressure, 95
' traction, 95
INDEX
13G1
Epiphysial cartilage, 93
Epiphysis, 35, S12, 1277
Epiploic foramen, 1156
Epitrochloo-aiiconajus muscle, 448
Epistropheus, 100
Epilhalamus, 743, 812
fasciculus rctroflexus [of Mey-
nert], 812
ganglion habenula, 812
pineal body, 812
structure of, 812
posterior commissure, 812
nucleus of, bil2
trigonum habenula:, 812
Epithelium, enamel, 1123
germinal, of Waldeyer, 1209,
1255
stratified, of cornea, 1007
transitional, 1223
Epitympanic recess, 142, 1038
Eponychium, 1067
Epoophoron, 1206, 1255
Equator of lens, 1019
Erector clitoridis muscle, 430
penis muscle, 428
spinaj or sacrospinalis muscle,
397
Eruption of teeth, 1124
Erythroblasts, 88
Esophageal arteries, 581, 600
glands, 1146
hiatus in diaphragm, 406
nerves, 913
plexus, 913
Esophagus, 1144
abdominal portion of, 1146
cervical portion of, 1145
lymphatic vessels of, 719
nerves of, 1146
structure of, 1146
tela submucosa, 1146
thoracic portion of, 1145
tunica 77iucosa, 1146
muscularis, 1146
vessels of, 1146
Ethmoid bone, 153
articulations of, 156
cribriform plate of, 153
crest, 161, 167
foramina, 189
horizontal lamina of, 153
labyrinth or lateral mass of,
154
lamina papyracea of, 155
OS planum of, 155
ossification of, 155
perpendicular plate of, 153
uncinate process of, 155
vertical plate, 154
Ethmoidal arteries, 570
canals, 138, 154
cells, 154, 998
notch, 137
plate, 85
process of inferior nasal concha,
169
spine, 147, 190 •
Ethmovomerine cartilage, 171
Eustachian tube, 1042
valve, 530
Excavation, rectouterine, 1152
retrovesical, 1152
vesicouterine, 1152
Exner, plexus of, 846
Exognathion, 200
Extensor carpi radialis acces-
sorius muscle, 452
brevis muscle, 452
actions of, 456
nerves of, 456
•variations ol, 452
intermedius muscle, 452
longus muscle, 452
actions of, 456
nerves of, 456
86
Extensor carpi radialis longus
muscle, variations of, 452
ulnaris muscle, 454
actions of, 456
nerves of, 45()
variations of, 454
coccygis inuscle, 401
digiti quinti proprius muscle,
454
actions of, 456
nerves of, 456
variations of, 454
digitorum brevis muscle, 488
actions of, 488
nerves of, 488
variations of, 488
communis muscle, 452
actions of, 456
nerves of, 456
variations of, 454
longus muscle, 481
actions of, 482
nerves of, 482
variations of, 482
hallucis longus inuscle, 481
actions of, 482
nerves of, 482
variations of, 481
indicis proprius muscle, 456
actions of, 456
nerves of, 456
variations of, 456
minimi digiti muscle, 454
ossis metacarpi poUicis muscle,
455
metatarsis hallucis muscle,
481
pollicis brevis muscle, 455
actions of, 456
nerves of, 456
variations of, 455
longus muscle, 455
actions of, 456
nerves of, 456
primi internodii pollicis muscle,
455
proprius hallucis muscle, 481
secundi internodii pollicis
muscle, 455
Exterior of skull, 178
External abdominal ring, 410
arcuate ligament, 405
auditory canal, 1036
meatus, 1036
calcaneal artery, 638
calcaneoastragaloid ligament,
352
canthus of eyelids, 1025
circumflex artery, 030
cutaneous nerve, 953
geniculate body, 811
intercostal muscles, 403
lateral ligament. 297, 322, 328
ligament of malleus, 1045
malleolar artery, 635
oblique muscle, 409
plantar artery, 639
nerve, 903
popliteal nerve, 964
pterygoid muscle, 380
pudic arteries, 629
respiratory nerve of Bell, 933
saphenous vein, 670
semilunar fibrocartilage, 343
spermatic fascia, 1238
sphincter ani muscle, 425
Extraspinal veins, 668
Extremitas acromialis [clavicula],
202
siernalis [clavicula], 202
Extremity of penis, 1250
Extrinsic muscles of tongue,
1129
Eye, 1000
Eyeball or bulb of eye, 1000
Eyeball, accessory organs of, 1021
aqueous humor, 1018
capsule of Tenon, 1024
chambers of, 1012
choroid, 1009
ciliary body, 1010
muscle, 1011
processes, 1010
conjunctiva, 1026
cornea, 1006
crystalline lens, 1019
development of, 1001
fascia bulbi, 1024
fibrous tunic, 1005
hyaloid membrane, 1018
iris, 1012
orbiculus ciliaris, 1010
pupil, 1012
pupillary memVjrane, 1003
refracting media, 1018
retina, 1014
pigmented layer of, 1015
proper, 1015
supporting frame-work of,
1017
sclera, 1005
tunics of, 1005
vascular, 1009
uvea, 1013
vessels and nerves of, 1021
vitreous body, 1018
Eyebrows, 1025
Eyelashes, 1025
Eyelids, 1025
canthus of, 1025
development of, 1005
structure of, 1025
surface anatomy of, 1299
tarsi of, 1025
Eye-teeth, 1117
Face, bones of, 156
development of, 67
lymphatics of, 692
surface anatomy of, 1294
Facial artery, 553
transverse, 558
bones, 156
canal, 142
hiatus of, 142
prominence of, 1042
lymph glands, 694
nerve, 901
composition and central con-
nections of, 861
sympathetic efferent fibers of,
970
vein, anterior, 645
common, 645
deep, 645
posterior, 645
transverse, 645
Falciform ligament of liver, 1150
1192
margin of fossa ovalis, 469
process of sacrotuberous liga-
ment, 309
Fallopian tubes, 1257
Fallopius, aqueduct of, promi-
nence of, 1042
False ligaments of bladder, 1231
pelvis, 239
ribs. 123
vocal cords, 1079
Falx aponeurotica inguinalis, 414
cerebelli, 873
cerebri, 873
Fascia or Fasciae, 376
of abdomen, 408
triangular, 412
anal, 421
of ankle, 488
1362
IXDEX
Fascia or FascijE, antibrachial,
445
antibrachii, 445
of arm, 442
axillarj'. 436
bicipital, 444
brachial, 442
hrachii, 442
buccopharyngeal, 390
bulb. 1204
of Camper, 408
cer\'ical, 387, 388
clavipectoral, 437
of Colles, 235, 409, 426
colli, 388
coracoclavicular, 437
coracoclavicularis, 437
cremasteric, 414
cribrosa, 468
cruris, 480
deep, 378
of deltoideus, 439
dentata hippocampi, 827
diaphragmatic part of pelvic,
421
dorsal, of foot, 490
endopelvic, 422
of forearm, 445
general description of, 376
of hand, 456
iliaca, 466
iliopectineal, 466
infraspinata, 441
infraspinatous, 441
infundibuliform, 418
intercolumnar, 1238
intercostal, 402
intercrural, 411
lata, 468
falciform margin of, 469
fossa oralis of, 469
iliotibial tract or band of, 468
of leg. 4N0
deep transverse, 483
lumbar, 397
masseteric, 385
of obturator internus, 420
orbital, 1025
palmar, 460
parotideomasseteric, 385
pectoral, 435
pelvic, 420
plantai-, 490
pretracheal, 390
prevertebral, 390
of piriformis, 421
of psoas and iliacus, 466
of quadratus lumborum, 419
rectal, 422
rectovesical, 422
renal, 1220
of Scarpa, 408
Sibson's, 1089
spermatic, external, 411, 1238
subscapular, 440
subscapnlaris. 440
superficial, 377
supraspinala, 440
supraspinatous, 440
temporal, 386
of thigh, 467
of l:horacic region, 435
transversalis, 418
triangular, of abdomen, 412
of upper extremity. 431
of urogenital diaphragm, 42S,
429, 430
region, 426
vesical, 422
Fasciculi, intrafusal. 1061
longitxidinales, liib
Fasciculus, bulbospinal, 854
cerebelloolivary, 781
cerebrospinal, 759, 760
cerebrospinalis anterior, 759
Fasciculus, cerebrospinalis later-
alis, 700
comma-shaped, 764
cuneatus, 762
gracilis, 762
lateral proper, 762
spinothalamic, 762
lateralis proprius, 762
of Lissauer, 762
longitudinal, inferior, 844
medial, 762, 784, 803
posterior, 803
superior, 844
mammillotegmentalis, 867
mammillo-thalamic, 869
occipitofrontal, 844
olfactory, 840
olivospinal, 761, 854
perpendicular, 844
pontospinal, 872
posterior proper, 764
retroflexus of jNIeynert, 812
rubrospinal, 761, 870
secondarj- sensory, 762
solitarius. 785
spinocerebellar, dorsal, 761. 778
ventral, 761
spinoolivary, 854
spinotectal, 762
spinothalamic, 762
superficial antero-lateral, 854
tectospinal, 760, 871
thalaraomammillary, 839 •
uncinate, 843
ventral spinothalamic, 854
vestibulospinal, 760, 803, 872
Fasciola cinerea, 827
Fauces, arches or piUars of, 1137
isthmus of, 1137
muscles of, actions of. 1140
Female genital organs, 1254
bulb of vestibule, 1264
caruncuhe hymenales, 1266
clitoris, 1266
development of, 1205
epoophoron, 1255
fourchette, 1265
glands of Bartholin, 1266
greater vestibular, 1266
hymen, 1266
labia majora, 1265
minora, 12G5
mons pubis, 1265
na\acular fossa, 1266
ovaries, 1254
uterine tubes, 1257
uterus or womb, 1258
vagina, 1264
vestibule, 1266
pronucleus, 42
urethra, 1236
Femoral artery, 623
branches of, 629
peculiarities of, 629
surface marking of, 1346
canal, 625
circumflex arteries, 630
cutaneous nerve, anterior, 955
lateral, 951
posterior, 959
fossa, 626
nerve, 955
ring, 625
septum, 626
sheath, 625
triangle, 626
vein, 672
Femur, 242
architectiu-e of, 248
inner, of upper, 249
of distal portion, 253
condvles of, 247
head of, 243
neck of. 243
ossification of, 255
Femur, spiral line of, 245
surface anatomy of, 1336
trochanters of, 243, 244
Fenestra cochlea-, 1040
ovalis, 1040
rotunda, 1040
vestibuli, 1040
Fertilization of o-\-um, 44
Fetal membranes, 54
Fetus, circulation in, 540
foramen ovale in, 512, 539
valve of inferior vena cava in,
540
vascular system in, peculi-
arities of, 539
Fibers, arcuate, 782
dentinal, 1119
intercolumnar, 410
intercrural, 410
intrafusal, 1061 '
of muscles, 373 " ■
nerve, 721
non-medullated. 728
olfactory projections, 869
of Purkinje, 536
of Remak, 728
sustentacular, of Muller, 1017
of tactile discrimination, 854
taste, 861
of Tomes, 1119
touch, S54
Fibrce intercrurales, 410
pontis profunda', 7S5
superficiales, 785
propria: [cerebellum], 794
Fibrocartilage, 2S1
circumferential, 282
connecting, 282
interarticular, 281
intervertebral, 2S9
semilunar, of knee, 342, 343
stratiform, 282
yellow or elastic, 282
Fibrocartilaginous lamina, inter-
pubic, 311
Fibrous capsule of Glisson, 1194
pericardium, 525
rings of heart, 536
sheaths of flexor tendons of
fingers, 449
of toes, 492
tunic of kidney, 1220
Fibula, 260
ossification of, 262
surface form of, 1337
Fibular artery. 635
collateral ligament of knee-
joint, 341
Fifth metacarpal bone, 228
metatarsal bone, 274
nerve, 886
ventricle, 840
Filiform papilla* of tongue, 1127
Fillet, medial, 803
Filtration angle of eye, 1007
Filum terminale, 750
Fivibria hippocampi, 840
ovarian, 1257
Fimbriae of uterine tube, 1257
Fimbriodentate fissure, 827, 840
First cuneiform bone, 270
dorsal metacarpal arten.', 595
metatarsal arterj-, 636
metacarpal bone, 228
metatarsal bone, 272
nerve, 881
Fissura antitragohelicina, 1034
calcarina, 820
cerebri lateralis [Sylrii], 819
longitudinalis, 818
collateralis, 820
hippocampi, 826
mediana anterior [medulhe ob-
longata?], 767
spinalis], 752
INDEX
1363
Fissura mediana posterior [medul-
Iss oblongatEe], 767
parietooccipitalis, 820
petrotympanica, 1038
prima [cerebullum], 740
[rhinencephaloii], 827
secunda [cerebellum], 740
Fissure or Fissures, anterior me-
dian of medulla spinalis, 752
callosomarginal, 820
of cerebellum, 788, 789
development of, 741
floccular, 741
horizontal, 789
postcentral, 789
postnodular, 741, 790
postpyramidal, 790
precentral, 789
preclival, 789
prepyramidal, 790
of cerebrum, 819
calcarine, 820
callosal, 825, 828
central, 819
collateral, 820
development of, 747
external rhinal, 744
fimbriodentate, 827, 840
hippocampal, 74'j, 826
interlobular, 819
la-teral, 746, 819
longitudinal, 818
parietooccipital, 820
of Rolando, 819
of Sylvius, 819
transverse, 842
choroidal, 841, 1002
circuminsular, 821
dentate, 826
Glaserian, 140, 1038
of liver, 1191
longitudinal. 818
of lungs, 1096
of medulla oblongata, 767
orbital, inferior, 184, 189
superior, 1.51, 189, 192
petrooccipital, 181, 193
petrosphenoidal, 181
petrotympanic, 140, 180, 1038
pterj-goid, 151
ptervgomaxillarv, 185
of Rolando, 8I9-
sphenomaxillary, 1S4
of Syh-ius. 747, 819
tympanomastoid, 181
vestibular, 1051
Fixation of kidney, 1220
of muscles, 362
Flat bones, 79
Flechsig, cerebellar tract of, 761
oval area of, 764
Flexor accessorius longus digi-
torum muscle, 485
muscle, 493
bre\'is minimi digiti muscle,
464, 494
carpi radialis muscle, 446
actions of, 450
nerves of, 450
variations of, 446
ulnaris muscle, 447
actions of, 450
nerves of, 450
variations of, 448
digiti quinti brevis muscle of
foot, 494
actions of, 496
nerves of, 495
of hand, 464
actions of, 464
nen.-es of, 464
digitorum bre\-is muscle, 491
actions of, 496
nerves of, 495
variations of, 492
Flexor digitorium longus muscle,
485
actions of, 486
nerves of, 486
variations of, 485
profundus muscle, 448
actions of, 450
nerves of, 450
variations of, 449
sublimis muscle, 448
actions of, 450
nerves of, 450
' variations of, 448
hallucis brevis muscle, 493
actions of, 496
nerves of, 495
variations of, 493
longus muscle, 485
actions of, 486
nerves of, 486
variations of, 485
poUicis brevis muscle, 461
actions of, 462
nerves of, 462
variations of, 462
longus muscle, 449
actions of, 450
nerves of, 450
variations of, 449
Flexure, cervical, 737
colic, left, 1181
right, 1180
hepatic, 1180
pontine, 737
splenic, 1181
ventral cephalic, 737
Floating ribs, 123
Floccular fissure, 741
Flocculus, 791
Floor of fourth ventricle, 798
Floor-plate of medulla spinalis,
733
Fluid, cerebrospinal, 877
Fluids, circulating, 503
Fold or Folds, amniotic, 56
aryepiglottic, 1079
caudal, 53
cephalic, 53
duodenojejunal, 1159
gastropancreatic, 1156
glossoepiglottic, 1075
ileocecal, 1160
malleolar, 1039
rectouterine, 1260
sacrogenital, 1154, 1260
salpingopalatine, 1142
salpingopharyngeal, 1142
transverse, of rectum, 1183
of Treves, 1160
umbilical, 1231
ventricular, of larynx, 1079
vestigial, of Marshall, 522, 526
vocal, of larynx, 1080
Folium cacuminis, 790
vermis, 790
Follicle of hair, 1067
Follicles, agminated, 1176
Graafian, or vesicular ovarian,
1256
Fontana, spaces of, 1009
Fontanelles, 196
Foot, arches of, 360
fascia of, 490
muscles of, 490
ossification of bones of, 275
phalanges of, articulations of,
359
skeleton of, 262
surface anatomy of, 1337
Foramen, caroticoclinoid, 151, 191
cecum of frontal bone, 137
of medulla oblongata, 767
of tongue, 1103, 1125
condyloid, anterior, 131
epiploicum, 1106, 1156
Foramen of Huschke, 145, 147
incisive, 162, 180
infraorbital, 158, 187
interventricular, 816, 840
intervertebral, 96
jugular, 181, 193
lacerum, 181, 192
magnum, 129, 132, 192
Majendii, 798
mandibular, 173
mastoid, 141, 183 ,
mental, 172, 188
of Monro, 816,840
obturator, 237
optic, 147, 151, 190
ovale of heart, 512, 539
of sphenoid, 150, 180, 192
palatine, 180
parietal, 178
rotundum, 150, 192
sciatic, 309
singulare, 143
sphenopalatine, 168
spinosum, 150, 180, 192
sternal, 121
stylomastoid, 144, 181
supraorbital, 130, 186, 189
supratrochlear, 212
thyroid, 237
transversarium, 98
vena-caval, 406
vertebral, 96
Vesalii, 150, 192
of Winslow, 603, 1156
zygomaticofacial, 164, 187
zygomaticoorbital, 165
zygomaticotemporal, 164, 183
Foramina, ethmoidal, 189
intervertebral, 96
of Luschka, 798, 877
for olfactory nerves. 153
in roof of fourth ventricle, 799
sacral, 106, 108
of Scarpa, 162, ISO
of Stensen, 162, 180
Thebesii, 530
venarum minimarum, 530
Forceps, anterior, 829
posterior, 829
Forearm, fascia of, 445
muscles of, 445
Fore-brain, 51, 741, 807
Foregut, 53, 1101
Foreskin, 1250
Form of embryo at different
stages, 74
Formaiio reclicularis alba, 784
grisea, 784
of medulla spinalis, 754
Fornicolumns, 838
Fornix of brain, 838
body of, 838
columns of, 838
crura of, 840
development of, 747
pillars of, 838, 840
of conjunctiva, 1027
Fossa or Fossse, acetabular, 237
anticubital, 589
canine, 158
cecal, 1160
cochlearis, 1048
condyloid, 131, 181
coronoid, 212
cranii anterior, 190
media, 190
posterior, 192
digastric, 141
digital, of epididymis, 1242
of femur, 244
for ductus venosus, 1191
duodenal, 1159
duodenojejunal, 1159
femoral, 626
for gall-bladder, 1191
1364
INDEX
Fossa or FossiE, glenoid, 140
hyaloid, 1018
hi'pophyscos, 147, 190
ileocecal, 1160
iliac, 234
incisive, 158, 172, 188
incudis, 1042
for inferior vena cava, 1191
infraspinatous, 203
infratemporal, 1S4
infratetn poralis , 184
intercondyloid, of femur, 247
of tibia, 25G
interpeduncular, 800, 816
intersigmoid, 1161
ischiorectal, 425
ischiorectalis, 425
jugular, 144
lacrimal, 137, 188
of liver, 1191
mandibular, 140, ISO, 183
mastoid, 140
nasal, 994
navicularis [urethra], 1235
[vulva], 1266
occipital, inferior, 193
olecranon, 212
ovalis of fascia lata, 469
of heart, 531
ovarian, 1154, 1254
pararectal, 1154
paravesical, 1154
pericecal, 1160
peritoneal, 1158
popliteal, 631
pterygoid, 151
pterygopalatina, 185
pterygopalatine, 185
radial, 212
retrocecal, 1161
retroperitoneal, 1158
rhomboid, 79S
rhomboidea, 79S
of Rosenmiiller, 1141. 1142
sagittalis sinistra [liver], 1141
scaphoid, 151, 180
of skull, anterior, 190
middle, 190
posterior, 192
sphenomaxillary, 185
subarcuate, 143
subscapular. 202
supraspinatous, 203
supratonsillar, 1138
Sylvian, 747
temporal, 183
temporalis, 183
triangularis, 1034
trochanteric, 244
for umbilical vein, 1191
venre cav(V, 1191
vermian, 131
vesicm felletr ,1191
Fountain decussation of Meynert,
806
Fourchette, 1265
Fourth metacarpal bone, 228
metatarsal bone, 274
nerve, 885
ventricle, 797
floor of, 798
Fovea capitis fetjioris, 243
centralis rcfirur, 1015. 1017
structure of, 1017
dentis, 99
of rhomboid fossa, 800
trochlear, 137, ISS
Foveolae, Howship's, 88
Free nerve-endings, 1059
Freely movable joints, 2S5
Frenula of colic valve, 1179
of lips, 1111
Frenulum of clitoris, 1266
of labia minora, 1265
linguae, 1125
Frenulum of prepuce, 1250
veli, 805
Frommann's lines, 727
Frontal air sinuses, 138, 998
artery, 750
bone, 135
articulations of, 138
orbital or horizontal part of,
137
ossification of, 138
squama of, 135
structure of, 138
convolution, ascending, 821
crest, 136
eminences, 135, 178, 183
gyri, 821, 822
lobe, 821
nerve, 887
operculum, 825
process of maxilla, 161
sulci, 821
suture, 135, 178
vein, 644
Frontalis muscle, actions of, 380
nerves of, 380
variations of, 380
Frontoethmoidal suture, 190
FrontomaxUlary suture, 189
Frontonasal duct, 138
process, 97
Frontopontine fibers, 802
Frontosphenoidal process of zygo-
matic bone, 164
Fundiform ligament of penis, 1249
Fundus glands of stomach, 1166
tympani, 1038
of uterus, 1259
Fungiform papillae of tongue,
1126
Funiculi of medulla spinalis, 758,
759
Funiculus separans, 800
spermaticiis, 1239
Furcal nerve, 949
Furcula, 1071,1103
Furrow, chordal, 52
dental, 1122
nasooptic, 69, 1005
Furrowed band of cerebellum, 971
Fusiform gyrus, 823, 824
G
Galea aponeurotica, 380
Galen, veins of, 653
Gall-bladder, 1197
fossa for, 1191
lymphatic capillaries in, 686
vessels of, 711
structure of, 1198
Gangliated cord, 976
Ganglion or Ganglia, 730
aorticorenal, 985
cardiac, of Wrisberg, 984
carotid, 977
celiac, 985
cerAacal, 978, 980
cervicale inferius, 980
medium, 979
superius, 978
ciliary, 888
cceliaca, 985
collateral, 976
of Corti, 1051, 1059
Gasserian, 886
genicular, 902
gcniculi, 902
of glossopharyngeal, 906
habenulo', 812
impar, 9S4
inferior, 90S
interpeduncular, 800, 802, 868
jugular, 90S, 911
jugular e, 911
Ganglion or Ganglia, I.anglev's,
1137
lenticular, 888 -
Meckel's, 891
nodosum, 911
ophthalmic, 888
otic, 897
oticum, 897
petrosum, 908
petrous, 90S
phrenicum, 9S6
ridge or neural crest, 51, 736
of Scarpa, 1058
semilunar, of abdomen, 985
of trigeminal nerve, 886
semilunare [Gasseri], 886
sphenopalatine, 891
rami nasales posteriores in-
feriores, 893
superiores, 893
orbitales, 893
spinal, 918
spinale, 918
spiral, of cochlea, 1059
splanchnicum, 981
submaxillare, 898
submaxillary, 898
superior, of glossopharj-ngeal,
90S
mesenteric, 987
superius, 90S
of vagus, 910
vestibular, 1058
of Wrisberg, 984
Ganglionic arterial system of
brain, 574
arteries, anterolateral, 573
antero-medial, 571
postero-lateral, 5S1
postero-medial, 574, 581
layer of retina, 1016
Gartner, duct of, 1206, 1255
Gasserian ganglion, 886
Gaster, 1161
Gastric arteries, short, 600
arterv, left, 603
right, 604
glands, 1166
impression, 1189
lymph glands, 706
nerves from vagus, 913
plexuses from sympathetic,
986, 987
from vagus, 913
veins, short, 681
Gastrocnemius muscle, 482
actions of, 4^3
nerves of, 4n3
variations of, 483
Gastrocolic ligament, 1153
omentum, 1157
Gastroduodenal artery, 604
Gastroepiploic arteries, 604, 606
gland, right, 706
veins, 681. 682
Gastrohepatic omentum. 1156
Gastrolienal ligament, 1155
Gastropancreatic fold, 1 lot)
Gastrophrenic ligament, 1162
Gemelli muscles, actions of, 478
nerves of, 478
Gemellus inferior muscle, 477
superior muscle, 477
General sensations, peripheral
terminations of nerve of, 1059
Generation, development of ex-
ternal organs of, 1213
Genicular arteries, 631, 633
ganglion of facial nerve, 902
Geniculate bodies', 811
Geniculum of facial nerve, 902 ,
of internal capsule, 836
Genioglossus muscle, 1129
Geniohyoglossus muscle, 1129
Geniohyoid muscle, 393
INDEX
1365
Geniohyoideus muscle, 393
action of, 393
nerves of, 393
variatious of, 393
Genital cord, 1207
corpusclfS, 1060
organs of female, 1254
external, 1264
of male, 1236
glands, 1207
ridge, 1207
swellings, 1214
tubercle, 1213
Genitocrural nerve, 953
Genitofemoral nerve, 953
Gennari, band of, 845, 847
Genu of corpus callosum, 828
of internal capsule, 836
Gerlach, tube tonsil of, 1043
Germ centers, 089
dental, 1122
Germinal cells, 35
epithelium, 1207, 1255
path, 1210
spot, 39
vesicle, 39
Giacomini, band of, 827
Giant cells, 88
of Betz, 845
Gianuzzi, crescents of, 1 136
Gimbernat's ligament, 412
Gingiva, 1112
Ginglymus, 285
Giraldes, organ of, 124G
Girdle of inferior extremity, 200
pelvic, 200
shoulder, 200
of superior extremity, 200
Glabella, 135, 178, 198
Gladiolus, 120
Gland or Glands, accessory, of
mouth, 1137
part of parotid, 1134
anterior lingual, 1131
aortic, 1269
areolar, 1267
arytenoid, 1084
of Bartholin, 1266
of Blandin, 1131
of Bowman, 996
Brunner's, 1176
buccal, 1112
bulbourethral, 1253
cardiac, 1166
carotid, 1281
ceruminous, 1037
cUiary, 1025
coccygeal, 1281
Cowper's, 1253
ductless, 1269
duodenal, 1176
esophageal, 1140
fundus, 1166
gastric, 1166
gastro-epiploic, right, 706
genital, 1207
intestinal, 1174
labial, 1111
lacrimal, 1028 .
of larynx, 1084
lenticular, of stomach, 1167
of Littre, 1235
Luschka's, 1281
mammce, 1267
mammary, 1267
Meibomian, 1026
molar, 1112
mucous, of tongue, 1131
of Nuhn, 1131
oxyntic, 1166
parathyroid, 1271
parotid, 1132
Peyer's, 1176
preputial, 1250
prostate, 1251
Gland or Glands, pyloric, 1 166
salivary, 1132
sebaceous, 1069
serous, of tongue, 1137
solitary, 1176
sublingual, 1136
sul^maxillary, 1135
sudoriferous, 1070
suprarenal, 1278
sweat, 1070
tarsal, 1026
thymus, 1273
thyroid, 1269
of tongue, 1131
trachoma, 1028
urethral, 1235
uterine. 1262
vestibular, greater, 1266
Glandula lacrimalis, 1028
parotis, 1132
sublingualis, 1136
submaxillaTis, 1135
suprarenalis, 1278
thyreoidca, 1269
vestibularis major [Bartholini],
1266
Glandula bulbourethrales , 1253
duodenales [Brunneri], 1 176
intestinales [Lieberkuhni], 1174
labialcs, 1111
cesophagete, 1146
Pacchioni, 878
sebacecc, 1069
sudoriferw, 1070
suprarenales accessori/r, 1279
tarsales [Meibomi], 1026
thyreoidece accessoricr , 1270
Glans cliloridis, 1266
penis, 1248
Glaserian fissure, 140, 1038
Glenohumeral ligaments, 318
Glenoid cavitj', 207
fossa, 104
ligament of Cruveilhier, 332,
359
of shoulder, 319
Glenoidal labrum of hip-joint,
336
of shoulder-joint, 319
Gliding joints, 285
movement, 2S6
Glisson's capsule, 1157, 1194
Globular processes of His, 68
Globus major [epidid\-mis], 1242
minor [epididymis], 1242
pallidus, 834
Glomera carotica, 1281
Glomus caroticum, 1281
coccygeum, 1281
Glossoepiglottic folds, 1075, 1125
Glossopalatine arch, 1137
Glossopalatinus muscle, 1129,
1139 note
Glossopharyngeal nerve, 906
composition and central con-
nections of, 856
sympathetic afferent fibers
of, 972
Glottis res piratorta, 1080
vocalis, 1080
rima of, 1080
Glutaeus maximus muscle, 474
actions of, 478
nerves of, 478
medius muscle, 474
actions of, 478
nerves of, 478
variations of, 475
minimus muscle, 475
actions of, 478
nerves of, 478
variations of, 475
Gluteal arterj', inferior, 620
superior, 622
lines of ilium, 232
Gluteal muscles, 474
nerves, 959
tuberosity, 246
veins, 674
Gnathic index, 246
Golgi, cells of, 845
organs of, 1061
Golgi and Mazzoni, corpuscles of,
1061
GoU, tract of, 752, 762
Gomphosis, 284
Gonion, 198
Gower's, tract of, 761, 854
Graafian follicles, 1256
structure of, 1256
Gracile nucleus, 774
Gracilis muscle, 471
actions of, 474
nerves of, 474
Grandry, tactile corpuscles of,
1060
Granular layer of dentin, 1119 __
Granulationes arar.hnoideales, 878
Granulations, arachnoid, 878
Granule cells, 377
Graj^ commissure of brain, 809
commissures of meduUaspinalis,
754
or gelatinous nerve fibers, 728
substance of cerebellum, 794
of cerebral hemispheres, 845
of cortex, 794
of medulla oblongata, 779
spinalis, 753
Great auricular nerve, 920
cardiac nerve, 979
vein, 642
cerebral vein, 653
longitudinal fissure, 818
omentum, 1157
sacrosciatic ligament, 309
saphenous vein, 669
splanchnic nerve, 981
transverse fissure of brain, 842
wings of sphenoid, 149
Greater cavernous nerve, 989
curvature of stomach, 1162
multangular bone, 225
occipital nerve, 923
omentum, 1157
palatine foramen, 180
pelvis, 238
peritoneal sac, 1150
sciatic foramen, 309
notch, 235
sigmoid cavity, 215
splanchnic nerve, 981
superficial petrosal nerve, 892,
903
•trochanter, 244
vestibular glands, 1213, 1266
Groove, auriculoventricular, 526
bicipital, 209
carotid, 148, 191
chiasmatic, 147, 190
costal, 124
infraorbital, 159
interatrial, 527
intertubercular, of humerus, 209
lacrimal, 159, 189
musculospiral, 211
mylohyoid, 173
neural, 50
obturator, 237
occipital, 141
optic, 147
primitive, 47
pterygopalatine, 151
for radial nerve, 211
vertebral, 115
Gubernaculum dentis, 1124
testis, 1211
Gudden, commissure of, 883
mammillo-tegmental bundle of,
867
1366
INDEX
Gullet, 1144
Gums, 1112
Gustatory calyculi, 991
cells, 991
hair, 992
pore, 991
Gyre, medifrontal, 822
precentral, 821
subfrontal, 822
superfrontal, 821
Gyri of brain, 821
angular, 823
of Broca, 822
central, anterior, 821
posterior, 823
cingulate, 826
cuneus, 823
dentate, 827, 868
frontal, 821, 822
fusiform, 823
hippocampal, 826
of insula, 825
of limbic lobe, 825
lingual, 823
occipital, 823
orbital, 822
precuneus, 823
quadrate, 823
straight, 822
subcallosal, 827, 869
superior parietal lobule, 823
supracallosal, 827
supramarginal, 823
temporal, 824
transverse, of Heschl, 824
uncus, 826
Gyrus of Broca, 822
centralis anterior, 821
posterior, 823
cinguli, 825
dentatus, 827
epicallosus, 827
frontalis inferior, 822
medius, 822
superior, 821
hippocampi, 826
marginal, 822
subcallosus, 827, 869
Habenular commissure, 812
Hair cells of spiral organ of Corti,
1057
Hairs, 1067
cuticle of, 1069
follicle of, 1067
gustatory, 992
olfactory, 996
roots of, 1067
scapus or shaft of, 1069
structure of, 1068
Haller, vas aberrans of, 1246
Hamate bone, 227
Hamstring muscles, 478
Hamulus of hamate bone, 227
lacrimal, 164
laminoB spiralis, 1051
pterygoid, 150, 180
Hand, muscles of, 456
phalanges of, articulations of,
333
skeleton of, 221
surface anatomy of, 1327
markings of, 1330
Hard palate, 1112
Harrison's sulcus, 128
Hasner, plica lacrimalis of, 1029
Hassal, corpuscles of, 1274
Haversian canals of bone, 89
systems of bone, 89
Head, arteries of, 549
lymphatics of, 692
muscles of, 378
Head, muscles of, development
of, 372
veins of, 644
Head-cap of spermatozoon, 42
Hearing, organ of, 1029
Heart, 526
arteries of, 538
atrioventricular bundle of His,
537
node, 537
atrium, left, 533
right, 529
component parts of, 526
development of, 506
endocardium, 535
fibers of atria, 537
of ventricles, 537
fibrous rings of, 536
lymphatic capUlaries of, 687
vessels of, 718
nerves of, 538
sinoatrial node of, 537
size and weight of, 526
structure of, 535
surface marking of, 1311
trigonum fihrosum, 536
veins of, 642
ventricle, left, 534
right, 531
Heidenhain, demilunes of, 1136
Height index of skull, 198
Helicine arteries, 1251
Helicis major muscle, 1035
minor muscle, 1035
Helicotrema, 1050
Helix, 1033
Helwig's bundle, 854
Hemiazygos vein, 667
accessory, 667
Hemispheres, cerebellar, 788
cerebral, 817
Hemorrhoidal artery, inferior, 619
middle, 615
superior, 610
nerve, inferior, 968
plexuses of nerves, 987, 988
vein, middle, 676
superior, 681
venous plexus, 676
Henle, loop of, 1223
Henle's layer of hair follicle, 1068
Hensen, canalis reuniens of, 1054
knot of, 47
stripe of, 1058
supporting cells of, 1058
Hepar, 1188
capsula fibrosa [Glissoni], 1195
fades inferior, 1189
posterior, 1190
superior, 1189
margo anterior, 1191
tunica serosa, 1195
Hepatic artery, 603
branches of vagus nerve, 913
cells, 1196
cylinders, 1193
duct, 1197
flexure of colon, 1180
lymph glands, 706
plexus, 986
veins, 680
Hepatoduodenal ligament, 1151,
1157
Hepatogastric ligament, 1151,
1157
Hepatorenal ligament, 1150
Herbst, corpuscles of, 1061
Hernia, congenital, complete, 1187
incomplete, 1188
into funicular process, 1189
HerophUus, torcular of, 658
Heschl, gyri of, 824
Hesselbach, interfoveolar liga-
ment of, 415
triangle of, 1221
Hiatus, aortic, 406
esophageal, 406
of facial canal, 142
semilunaris, 195, 995
Higher or cortical visual centers,
814
Highest intercostal artery, 585
veins, 666
nuchal line, 129
thoracic artery, 587
Highmore, antrum of, 159, 999
Hilum of kidnev, 1219
Hilus of lung, 1095
of spleen, 1283
Hind-brain, 738, 767
Hind-gut, 53, 1101
Hinge-joint, 285
Hip bone, 231
articulations of, 238
ossification of, 237
structure of, 237
surface anatomy of, 1336
Hip-joint, 333
movements of, 338
muscles in relation with, 338
surface marking of, 1343
Hippocampal commissure, 838,
869
fissure, 746, 826
gyrus, 826
Hippocampus, 746, 832
major, 832
His, atrioventricular bundle of,
537
globular processes of, 68
Holoblastic ova, 45
Horizontal cells of retina, 1017
part of palatine bone, 167
semicircular canal, 1049
sulcus of cerebellum, 789
Houston's valves of rectum, 1183
Howship's foveolse, 88
Huguier, canal of, 141, 904, 1039
Humeral articulation, 317
bursse in relation to, 319
movements of, 319
vessels and nerves of, 319
circumflex arteries, 589
Humerus, 209
ossification of, 213
structure of, 212
surface anatomy of, 1326
Humor, aqueous, 1018
Hunter's canal, 627
Huschke, auditory teeth of, 1055
foramen of, 145, 147
Huxley's layer of hair follicle,
1068
Hyaline cartilage, 279
cell, 504
Hyaloid canal, 1018
fossa, 1018
membrane of eye, 1018
Hyaloplasm, 36
Hydatid of Morgagni, 1207, 1242,
1257
pedunculated, of epididj'mis,
1242
Hymen, 1266
Hyoepiglottic ligament, 1077
Hyoglossal membrane, 1132
Hyoglossus muscle, 1129
Hyoid arteries, 552, 553
bone, 177
body of, 177
cornua of, 177
ossification of, 178
Hyothyroid ligaments, 1077
membrane, 1076
Hyparterial bronchi, 1085, 1097
Hypochondriac regions, 1149
Hypochordal bar or brace, 82
Hypogastric artery, 614
branches of, 615
in fetus, 540
INDEX
1307
Hypogastric artery, obliterated,
615
peculiarities of, 615
lymph glands, 704
plexus, 987
region, 1149
vein, 673
zone, 1148
Hypoglossal nerve, 914
composition and central con-
nections of, 855
nucleus of, 779
Hypophysis cerebri, 814, 1275
development of, 1276
Hypothalami, pars mammillaria,
74:s
optica, 744
Hypothalamus, 812
corpora mammillaria, 813
hypophysis or pituitary body,
814, 1275
infundibulum, 813
optic chiasma, 814
subthalamic tegmental region,
812
corpus subthalamicum, or
nucleus of Luys, 812
stratum dorsale, 812
zona incerta, 812
tuber cinerum, 813
Hypothenar eminence, 456
Ileocecal fold, 1160
fossie, 1160
valve, 1179
Ileocolic artery, 607
lymph glands, 709
Ileum, 1170
lymphatic vessels of, 710
Iliac arteries, common, 613
peculiarities of, 614
surface markings of, 1322
external, 622
surface markings of, 1322
internal, 614
peculiarities of, 614
circumflex artery, deep, 623
superficial, 629
vein, deep, 673
superficial, 669
colon, 1182
fascia, 466
fossa, 234
furrow, 1313
lymph glands, 703, 704
region, 1149
spines, 234
tuberosity, 234
vein, common, 677
peculiarities of, 677
external, 672
internal, 673
Iliacus muscle, 467
actions of, 4G7
fascia of, 466
nerves of, 467
variations of, 467
Iliocapsularis muscle, 4G7
Iliococcygeus muscle, 424
Iliocostalis cervicis muscle, 399
dorsi muscle, 399
lumborum muscle, 399
Iliofemoral ligament, 334
Iliohypogastric nerve, 950
Ilioinguinal nerve, 952
Iliolumbar artery, 621
ligament, 306
vein, 678
Iliopectineal eminence, 234
fascia, 466
Iliosacralis muscle, 424
Iliotibial band or tract, 468
Iliotrochanteric ligament, 335
Ilium, 231
ala of, 232
body of, 231
crest of, 234
dorsum of, 232
gluteal linos of, 233
spines of, 234
Imbedding or implantation of
ovum, 58
Immovable articulations, 284
Impression, colic, 1189
duodenal, 1190
gastric, 1189
renal, 1189
rhomboid, 202
suprarenal, 1191
trigeminal, 143
Incisive bone, 162
canals, 162, 180
foramen, 162, 180
fossa, 158, 172, 188
teeth, 1115
Incisor crest, 163
teeth, 1115
Incisura annularis, 1162
apicis cordis, 527
cardiaca, 1162
fastigii, 741
radialis, 215
semilunaris, 215
temporalis, 826
tentorii, 874
Incremental lines of Salter, 1120
Incus, 1044
crus breve, 1044
longum, 1045
development of, 1033
ligaments of, 1045, 1046
process of, long, 1045
short, 1044
Index, cephalic or breadth, 198
gnathic or alveolar, 199
nasal, 198
orbital, 198
vertical or height, 198
Indusium griseum, 827, 868
Inferior articular arteries, 633
articulation, 325
calcaneonavicular ligament,
355
cerebellar peduncles, 793
constrictor muscle, 1142
dental artery, 561
nerve, 896
epigastric vein, 672
ganglion, 908, 911
laryngeal nerve, 912
longitudinal sinus, 055
maxillary nerve, 893
medullary velum, 794
oblique muscle, 1023
profunda artery, 591
pubic ligament, 310
quadrigeminal body, 806
semilunar lobule, 791
tarsal plate, 1025
thyroarytenoid ligaments, 1080
vocal cords, 1080
Infraclavicular branches of bra-
chial plexus, 933
Infracostales muscle, 403
Infraglenoid tuberosity, 205
Infrahyoid artery, 552
muscles, 391
Infraorbital artery, 562
canal, 159
foramen, 158, 187
groove, 159
nerve, 889 note
plexus of nerves, 891
Infrapatellar pad of fat, 344
Infrascapular artery, 588
Infraspinatous fascia, 441
fossa, 203
Infraspinatus muscle, 441
actions of, 442
nerves of, 442
Infrasternal notch, 1307
Infratemporal crest, 150, 183
fossa, 184
surface of maxilla, 158
Infratrochlear nerve, 888
Infundibuliform fascia, 418
lufundibulopelvic ligament, 1261
Infundibulum of brain, 813
of ethmoid bone, 156, 195, 995
Inguinal aponeurotic falx, 414
canal, 418
glands, 702
ligament, 411
reflected, 412
regions, 1149
ring, abdominal, 418
subcutaneous, 410
Inion, 185, 198
Inlet of pelvis, 239
Inner cell-mass, 46
Innominate artery, 548
bone, 231
articulations of, 238
ossification of, 237
veins, G64
peculiarities of, 666
Inscriptions, tendinous, of rectus
abdominis, 416
Insertion of muscles, 362
Insula, 825
circular sulcus of, 825
development of, 825
gyri of, 825
opercula of, 825
Integument, common, 1062
Interalveolar cell-islets, 1204
Interarticular chondrosternal lig-
ament, 303
costocentral ligaments, 300
fibrocartilages, 281
sternocostal ligaments, 303
Interatrial groove, 527
Intercalatum, 802
Intercapitular veins, 661, 669
Intercarpal articulations, 328
movements of, 330
Intercavernous sinuses, 659
Intercellular biliary passages,
1197
Intercentral ligaments, 287
Interchondral ligaments, 304
Interclavicular ligament, 314
Interclinoid ligament, 153
Intercolumnar fascia, 1238
fibers, 410
Intercondyloid eminence of tibia,
256
fossa of femur, 247
of tibia, posterior, 256
Intercostal arteries from aorta,
600
highest, 585
from internal mammary, 583
superior, 585
fascise, 402
lymph glands, 715
membranes, 403
muscles, 403
nerves, 945
spaces, 123
veins, 666
Intercostales externi muscles, 403
variations of, 403
interni muscles, 403
variations of, 403
Intercostobrachial nerve, 946, 947
Intercrural fascia, 411
fibers, 410
Intercuneiform articulations, 357
Interfoveolar ligament of Hessel-
bach, 415
Interglobular spaces, 1120
13G8
INDEX
Interior of bladder, 1231
of larynx, 1078
of skull, 189
of uterus, 1260
Interlobular arteries of kidney,
1223
Intermediate cell-mass, 50
Intermetacarpal articulations, 331
Intermetatarsal articulations, 358
Internal abdominal ring, 418
acoustic meatus, 143
arcuate ligament, 404
calcaneal arteries, 639
nerves, 963
calcaneoastragaloid ligament,
352
calcaneona%'icular ligament, 355
canthus of eyelids, 1025
capsule of brain, 836
circumflex artery, 630
cutaneous nerve, 937, 955
lesser, 937
geniculate body, 81 1
iUac artery, 614
glands, 704
vein, 673
intercostals muscle, 403
lateral ligament, 297, 322, 328
malleolar artery, 635, 639
mammary artery, 583
gland, 715
maxillary glands, 694
oblique muscle, 412
palpebral arteries, 570
plantar artery, 639
nerve, 963
popliteal nerve, 960
pterygoid muscle, 387
pudendal arterj', 617
veins, 674
pudic artery, 617
nerve, 967
veins, 674
respiratory nerve of Bell, 928
saphenous nerve, 956
vein, 669
semilunar fibrocartilage, 343
sphincter ani muscle, 426
Internodal segments of nerves. 727
Interossei muscles of foot, 495
actions of, 495
nerves of, 495
of hand, 464
actions of, 465
nerves of, 465
Interosseous arteries, 595, 596, 597
ligament, 302
membrane of forearm, 325
of leg, 348
nerve, dorsal or posterior, 944
volar or anterior. 938
Interparietal bone, 132
Interpeduncular fossa, 816
ganglion, 800, 802, 868
Interphalangeal articulations
333, 359
Interpleural space, 1090
Interpubic disk, 311
fibrocartilaginous lamina, 311
Intersegmental neurons, 755
septa, 80
Intersfgmoid fossa, 1167
Interspinal ligaments, 291
Interspinales muscles, 400
actions of, 402
nerves of, 402
Interspinous ligament, 291
Intersternal ligaments, 304
Intertarsal articulations, 352
Intertragic notch, 1034
Intertransversales muscle, 401
Intertransversarii muscles, 401
actions of, 402
nerves of, 402
Intertransverse ligaments, 291
Intertrochanteric crest, 246
line, 245
Intertubercular plane, 1147
Intertubular dentin, 1120
Intervenous tubercle, 531
Interventricular foramen, 816,
840
septum, 534
Intervertebral fibrocartilages, 289
foramina, 96
veins, 669
Intervillous space, 59
Intestinal arteries, 607
glands, 1174
■\dlli, 1174
Intestine, development of, 1101
large, 1177
lymphatic nodules of, 1176
lymphatics of, 710
small, 1168
structure of, 1172
vessels and nerves of, 1176
surface markings of, 1319
Intestinum ccrcum, 1177-
crassum, 1177
ileum, 1171
jejunum, 1170
rectum, 1183
tenue, 1168
tela submucosa, 1172
tunica mucosa, 1173
muscularis, 1172
serosa, 1172
Intra-articular ligament, 300
Intracartilaginous ossification, 93
Intra-epithelial plexus of cornea,
1009
Intrafusal fasciculi, 1061
fibers, 1061
Intrajugular process, 131
Intralobular veins, 1196
Intramembranous ossification, 91
Intraparietal sulcus, 822
Intrapulmonary bronchi, 1098
Intraspinal veins, 668
Intrathyroid cartilage, 1074
j Intrinsic muscles of tongue, 1130
spinal reflex paths, 850
lodothyrin, 1271
Iridial angle, 1007
Iris, 1012
structure of, 1013
vessels and nerves of, 1014
Irregular bones, 80
Ischiocapsular ligament, 334
Ischiocavemosus muscle > 428, 430
action of, 428, 430
Ischiorectal fossa, 425
Ischium, 234
body of, 234
rami of, 235
spine of, 235
tuberosity of, 235
Island of Reil, 825
Islands, blood, 506
of Langerhans, 1204
Isthmus, aortic, 517, 547
of external acoustic meatus
1043
faucium, 1137
glandula thyreoidea, 1270
of limbic lobe, 825
rhombencephali, 738
of thyroid gland, 1269
of uterine tube, 1257
Iter chorda: anterius, 1039
posterius, 1038
Ivory of teeth, 1119
Jacob's membrane, 1017
Jacobson, nerve of, 909, 1047
vomeronasal organs of, 71, 996
Jejunum, 1170
lymphatic vessels of, 710
Jelly of Wharton, 58
Joint capsules, lymphatic capil-
laries in, 684
Joints. See Articulations.
development of, 283
Jugular foramen, 181, 193
fossa, 144
ganglion of glossopharyngeal
nerve, 908
of vagus nerve, 911
nerve, 978
notch, 120, 131
process, 131, 181
surface of temporal bone, 144
tubercle, 131
vein, anterior, 647
external, 646
internal, 648
bulbs of, 648
posterior external, 647
Jugum sphenoidale, 153
Junctional tube, 1223
Karyokinesis, 37
Karyomitome, 36
Karyomitosis, 37
Karyoplasm, 36
Kerckring, ossific center of, 133
Kerkring, valves of, 1173
Kidneys, 1215
calyces of, 1221, 1225
cortical substance of, 1221
development of, 1211
fixation of, 1220
hilum of, 1219
lymphatic capillaries in, 687
vessel.s of, 712
Malpighian bodies of, 1221
capsule, 1221
medullary substance of, 1221
minute anatomy of, 1221
nerves of, 1225
paranephric body, 1220
renal artery, 610
fascia, 1220
pelvis, 1221
sinus, 1221
tubules, 1221
structure of, 1220
surface marking of, 1320
veins of, 679, 1224
weight and dimensions of, 1215
Knee cap, 255
Knee-joint, 339
bursse of, 345
movements of, 346
surface anatomy of, 1338
Krause, end-bulbs of, 1060
membrane of, 375
Kiihne, motor end-plates of, 730
Labbe, posterior anastomotic
vein of, 652
Labia cerebri, 827
majoru, 1265
minora, 1265
oris, 1111
Labial arteries, 555
coinmissures, 1265
glands, 1111
grooves, 1102
Labiodental lamina, 1122
Labrum glonoidale, 319, 336
Labyrinth, membranous, 1051
development of, 1032
vessels of, 1059
osseous, 1047
INDEX
1369
Labyrinthus ethmoidalis, 154
memhranaceus, 1051
osseus, 1047
Lacertus fibrosus, 444
Laciniate ligament, 489
Lacrimal apparatus, 1028
artery, 569
bone, 163
articulations of, 164
lesser, 164
ossification of, 164
canals, 1028
caruncula, 1028
crest, posterior, 164
ducts or canals, 1028
ampullifi of, 1028
fossa, 137, 188
glands, 1028
groove. 159, 189
hamulus, 164
nerve, 887
notch, 159
papilla, 1025
process of inferior nasal concha,
169
punctum, 1025
sac, 1028
tubercle, 161
Lacteals, 683
Lactiferous ducts, 1268
Lacuna magna [of urethra], 1235
Lacunae of bone, 89, 90
of cartilage, 280
of urethra, 1235
venous, 655
Lacunar ligament, 412
Lacus lacrimalis, 1025, 1028
Lagena, 1054
Lambda, 178, 198
Lambdoidal suture, 132, 135, 183
Lamellae of bone, 89
articular, 279
circumferential, 89
interstitial, 89
primary or fundamental, 90
secondary or special, 90
Lamellar cells, 377
Lamina affixia, 838
basalts, 1010
cartilaginis cricoiderr, 1047
choriocapillaris, 1010
cribrosa sclera", 1005
dorsal or alar, 735
elastic, of cornea, 1008
elastica anterior, 1008
■posterior, 1008
fibrocartilaginea interpubica, 311
labiodental, 1122
lingual, 1122
medullary, 810
nasal, 68
reticular, 1058
spiral, of cochlea, 1051
spiralis ossea, 1051
suprachorioidea , 1005, 1010
terminalis, 742, 816
vasculosa, 1010
ventral or basal, 735
of vertebrae, 96
Lancisi, nerves of, 868
Langerhans, centro-acinar cells
of, 1204
islands of, 1204
Langhans, layer of, 47
Langlei^'s ganglion, 1137
Lantermann, segments of, 727
Large deep petrosal nerve, 892
intestine, 1177
cecum, 1177
colic valve, 1179
colon, 1180
ascending, 1180
descending, 1181
iliac, 1182
sigmoid or pelvic, 1182
Large intestine, colon, transverse,
IISO
rectvim, 1183
superficial petrosal nerve, 892,
903
Laryngeal artery, inferior, 581
superior, 552
nerves, 912
part of pharynx, 1142
prominence, 1073
saccule, 1080
sinus, 1080
Larynx, 1072
cartilages of, 1073
couus elasticus of, 1078
elastic membrane of, 1077
glands of, 1084
interior of, 1078
ligaments of, 1076
lymphatic vessels of, 698, 1084
mucous membrane of, 1083
muscles of, 1081
actions of, 1083
nerves of, 1084
rima glottidis of, 1080
surface marking of, 1301
ventricle of, 1080
ventricular folds of, 1079
vessels of, 1084
vestibule of, 1078
vocal folds of, 1080
Lateral cartilages, 993
cricoarytenoid muscle, 1081
sinuses, 657
spinothalamic fasciculus, 762
thyrohyoid ligament, 1077
Latissimus dorsi muscle, 432
actions of, 435
nerves of, 434
variations of, 434
Layer of Langhans, 47
of rods and cones, 1017
Layers of cerebral cortex, 845
Least splanchnic nerve, 981
Left atrium, 533
auricle, 533
auricular appendix, 533
coronary plexus, 985
vein, 642
lobe of liver, 1192
■ ventricle, 534
Leg, fascia of, 480
deep transverse, 483
muscles of, 480
development of, 372
Lemniscus, lateral, 805
lateralis, 805
medial, 804
medialis, 804
spinal, 762
Lens, capsule of, 1019
vascular, 1003
changes produced in, by age,
1021
crystallina, 1019
crystalline, 1019
development of, 1002
equator of, 1019
poles of, 1019
structure of, 1020
suspensory ligament of, lOlS
vesicle, 1001
Lenticula, 834
Lenticular ganglion, 888
glands of stomach, 1167
nucleus, 834
process of incus, 1045
Lentiform nucleus, 834
Lesser cavernous nerve, 989
curvature of stomach, 1162
internal cutaneous nerve, 937
lacrimal bone, 164
multangular bone, 225
omentum, 1156
pelvis, 239
Lesser peritoneal sac, 1152, 1155
sac or omental bursa of peri-
toneum, 1155
boundaries of, 1156
sciatic foramen, 309
notch, 235
sigmoid cavity, 215
splanchnic nerve, 981
trochanter, 245
Leucocytes, 504
Levator anguli oris muscle, 383
scapulaj muscle, 435
ani muscle, 422
actions of, 424
nerves of, 424
claWculae muscle, 435
glandulae thyreoidea3 muscle,
1270
menti muscle, 383
palati muscle, 1139
palpebrae superioris muscle,
1021
actions of, 1023
nerves of, 1023
prostatte muscle, 424
scapulae muscle, 435
actions of, 435
nerves of, 435
variations of, 435
veli palatini muscle, 1139
Levatores costarum muscle, 403
Lieberkiihn, crypts of, 1174
Lien, 1228
accessorius, 1283
extremitas inferior, 1283
superior, 1283
fades gastrica, 1282
renalis, 1283
margo anterior, 1283
posterior, 1283
Lienal artery, 605
plexus of nerves, 986
vein, 681
Ligament or Ligaments, acromio-
clavicular, 315
alar, 296
of ankle, 349, 350, 351
annular, of ankle, 488, 489
of radius, 324
of stapes, 1046
of wrist, 456, 458
anterior, 327
inferior, 348
longitudinal, 287
superior, 301, 348
apical odontoid, 296
arcuate, 405
atlantoaxial, 293
atlantooccipital, 296
membrane, posterior, 296
of auricula or pinna, 1035
of Bertin, 335
bifurcated, 354, 355
of Bigelow, 335
of bladder, 1231
broad, of uterus, 1260
calcaneoastragaloid, 352
calcaneocuboid, 354
calcaneofibular, 351
calcaneonavicular, plantar, 355
calcaneotibial, 350
capsular. .See Individual Joints,
caroticoclinoid, 153
carpometacarpal, 331
of carpus, 328, 329
central, of medulla spinalis, 879
check, 296
of eye, 1024
chondrosternal, 302
intra-articular, 303
chondroxiphoid, 304
common, anterior, 287
posterior, 288
conoid, 315
• of Cooper, 412
1370
INDEX
Ligament or Ligaments, coraco-
acromial, 316
coracoclavicular, 315
coracohumeral, 318
coronary, of knee, 343
of liver, 1130, 1192
costoclavicular, 310
costocoracoid, 437
costotransverse, 301
middle, 302
posterior, 301, 302
costovertebral, anterior, 299
costoxiphoid, 304
cotyloid, 237, 436
cricoarytenoid, posterior, 1078
cricotracheal, 1077
crucial, 342
cruciate, of atlas, 295
crural, 4S8
of knee, 342
cuboideonavicular, 357
deltoid, of ankle-joint, 350
dentate, 880
digital vaginal, 449
dorsal carpal, 458
radiocarpal, 327
radioulnar, 325
of elbow, 321,322
falciform, of liver, 1150, 1192
fibular collateral, of knee-joint,
341
fundiform, of penis, 1249
gastrocolic, 1151, 1153
gastrolienal, 1155
gastrophrenic, 1162
Gimbernat's, 412
glenohumeral, 318
glenoid, 319
of Cruveilhier, 332, 359
of shoulder-joint, 318
glenoidal labrum of hip-joint,
336
of shoulder-joint, 319
hepatoduodenal, 1151, 1157
hepatogastric, 1151, 1157
hepatorenal, 1150, 1192
of Hesselbach, 415
of hip-joint, 334
hyoepiglottic, 1077
iliofemoral, 334
iliolumbar, 306
iliotrochanteric, 335
of incus, 1046
inferior transverse of scapula,
317
infundibulopelvic, 1261
inguinal, 411
reflected, 412
interarticular, of ribs, 300
sternocostal, 303
intercarpal, 328, 329
intercentral, 287
interchondral, 304
interclavicular, 314
interclinoid, 153
intercuneiform, 357
interfoveolar, 415
intermetacarpal, 331
intermetatarsal, 358
interosseous, 302
interphalangeal, 333, 359
interpubic fibrocartilaginous
lamina, 311
interspinal, 291
interspinous, 291
intersternal, 304
intertarsal, 352
intertransverse, 291, 310
intra-articular, 300
ischiocapsular, 325
of knee-joint, 340
laciniate, 489
lacunar, 412
of larynx, 1076
lateral atlantooccipital, 296
Ligament or Ligaments, lateral
external, 297, 322, 328
internal, 297, 322, 328
of uterus, 1260
left triangular, of liver, 1151
of left vena cava, 526
long plantar, 354
of Mackenrodt, 1261
of malleus, 1045
medial palpebral, 380
metacarpophalangeal, 332
metatarsophalangeal, 359
middle cricothyroid, 1078
mucosum, of knee, 344
of neck of rib, 302
nucha>, 290
oblique cord, 325
popHteal, 340
occipitoaxial, 296
odontoid, 296
orbicular, 324
of ovarv, 1254
palmar, 328, 331
palpebral, 1026
pectinate, of iris, 1009
of pelvis, 403
phrenicocolic, 1158
phrenicolienal, 1155
phrenicopericardiac, right, 678
of pinna or auricula, 1035
plantar, long, 354
posterior, 328
cricoarytenoid, 1078
inferior, 348
of knee, 340
longitudinal, 288
sacroiliac, 307
superior, 348
Poupart's, 411
pterygomandibular, 384
pterygospinous, 153, 388
pubic, 310
pubocapsular, 334
pubofemoral, 335
pulmonary, 1088, 1090
quadrate, 324
radial collateral, of elbow-joint,
322
of wrist-joint, 327
radiate, 299
sternocostal, 302
of radiocarpal joint, 327
radioulnar, 325
reflected inguinal, 412
rhomboid, 314
right triangular of liver, 1151
round, of liver, 1192
of uterus, 1261
sacrococcygeal, 309
sacroiliac, 307
sacrosciatic, 309
sacrospinous, 309
sacrotuberous, 309
of scapula, 316
of shoulder-joint, 317
sphenomandibular, 297, 388
spinoglenoid, 317
spiral, of ductus cochlearis,
1054
stellate, 299
sternoclavicular, 313
sternocostal, 302
sternopericardiac, 526
of sternum, 302
structure of, 282
stylohyoid. 392
stylomandibular, 298, 388
subpubic, 310
superficial transverse of
fingers, 461
superior transverse of scapula,
317
suprascapular, 317
supraspinal, 290
supraspinous, 290
Ligament or Ligaments, suspen-
sory, of axilla, 436
of eye, 1025
of lens, 1018
of mamma, 435
of ovary, 1254
of penis, 1249
talocalcaneal, 352, 353
talona\'icular, dorsal, 354
talotibial, 350
tarsometatarsal, 358
of tarsus, 352
temporomandibular, 297
tendo oculi, 3bl
teres, of hip, 336
thyroarytenoid, inferior, 1080
thyroepiglottic, 1078
th>Tohyoid, 1077
tibial collateral, of knee-joint,
341
tibiofibular, 348
tibionavicular, 350
transversalis colli uteri, 1261
transverse acetabular, 336
of atlas, 293
carpal, 456
crural, 488
humeral, 319
inferior, 349
of knee, 343
metacarpal, 331
metatarsal, 359
of pelvis, 429
of scapula, 317
trapezoid, 315
triangular, of liver, 1192
of urethra, 428
of tubercle of rib, 302
ulnar collateral, of elbow-joint,
321
of wrist-joint, 327
uterosacral, 1260
of uterus, 1260
ventricular, of larj'nx, 1080
of vertebrae, 287
volar carpal, 456
metacarpophalangeal, 332
radiocarpal, 327
radioulnar, 325
of Wrisberg, 343
of wrist-joint, 327
Y-shaped, of Bigelow, 335
of Zinn, 1022
Ligamenia accessoria plantaria, 359
alaria, 296
auricularia [Valsalva], 1035
basium [oss. metacarp.] dorsalia,
331
interossea, 331
rolaria, 331
[oss. metatars.] dorsalia, 358
interossea, 358
planiaria, 358
carpometacarpece dorsalia, 331
volaria, 331
collaleralia, 359
costoxiphoidea, 304
cruciata genu, 342
cuneometatarsea interossea, 359
intercarpea dorsalia, 328
interossea, 328
volaria, 328
intercuneiformia interossea, 357
plantaria, 357
interspinalia, 291
interiransversaria, 291
navicularicuneiformia dorsalia,
356
plantaria, 356
ossiculorum auditus, 1045
sternocostalia radiata, 302
suspensoria [of mamma], 435
tarsometatarsea dorsalia, 358
plantaria, 358
vocales, 1080
IXDEX
1371
Ligamentous action of muscles,
287
Ligamentum acromioclavicular e,
315
annulare baseos stapedis, 1046
radii, 324
arcuaturn pubis, 310
bifuTcatum, 354
calcaneocuboideum dorsale, 354
plantare, 354
calcaneo fibular 2, 351
calcaneonavicular e plantare, 355
capituli costa interarticulare,'iQO
radiatum, 299
transversutn, 331
ca)-pi dorsale, 458
transversum, 456
volare, 456
collaterale fibular e, 341
radiale, 322, 328
iibiale, 341
w/nare, 322, 328
coZii costoe, 302
conoideum, 315
coracoacromiale, 316
coracoclaviculare, 315
coracohumerale, 317
coronarium hepatis, 1192
costoclavicular e, 314
costotransversarium anterius,
301
posterius, 301
cricoarytcenoidcum posterius,
1078 ■
cricolhyreoideum medium, 1078
cricoiracheale, 1077
cruciatum anterius, 342
posterius, 342
cuboideonaviculare dorsale, 357
plantare, 357
deltoideum, 350
denticulatum , 879
falciforme hepatis, 1192
hyoepiglotticum, 1077
hyothyreoideum laterale, 1077
medium, 1077
iliofemorale, 335
iliolumbale, 306
incudis posterius, 1045
superius, 1046
inguinale [Pourparti], 411
reftexum [Colleri], 412
interclaviculare, 314
ischiocapsulare , 335
lacunare [Gitnbernati], 412
latum pulmonis, 1090
uteri, 1260
longitudinale anterius, 287
posterius, 288
mallei anterius, 1045
laterale, 1045
superius, 1045
malleoli lateralis anterius, 348
posterius, 348
m,ucosum, 344
nucha?, 290
patellcp, 340
plantare longum, 354
popliteum obliquum, 340
pubicum superius, 310
pubocapsulare, 335
pulmonale, 1090
radiocarpeum dorsale, 328
xolare, 327
sacrococcygeum anterius, 309
laterale, 310
posterius, 309
sacroiliacum anterius, 307
interosseum, 308
posterius, 307
sacrospinosum, 309
sacrotuberosum, 309
sphenomandibulare, 297
sternoclaviculare, 313
Ligamentum sternocostale inter-
articulare, 303
stylomandibular e, 298
supraspinale, 290
talocalcaneum anterius, 352
interosseum, 353
laterale, 352
mediate, 353
posterius, 352
talofibulare anterius, 351
posterius, 352
talonaviculare dorsale, 354
temporomandibulare, 297
<eres femoris, 336
htpatis, 1193
wfcri, 1261
thyroepiglotticum, 1078
iransversalis colli uteri, 1261
transversum acetabuli, 336
atlantis, 293
crus inferius, 295
superius, 295
cruris, 488
06 WM, 343
scapulcB inferius, 317
superius, 317
irapezoideuni, 315
triangulare dextrum, 1192
sinistrum, 1193
tuberculi costa, 302
venosum, 1193
Ligature of arteries. iSee each
Arterj-.
Ligula, 797
Limbic lobe, 825
Limbs, development of, 71
Litnbus fossa; ovalis, 513
lamimc spiralis, 1055
Limiting membranes of retina
1017
Line or Lines, arcuate, of ilium,
234
colored, of Retzius, 1120
curved, of ilium, 232
gluteal, of ilium, 232
incremental, of Salter, 1120
intercondyloid, 247
intertrochanteric, 245
mylohyoid, 173
nuchal, 129, 182
' oblique, of fibula, 261
of mandible, 172
of radius, 219
pectineal, 246
popliteal, of tibia, 258
of Schreger, 1120
spiral, of femur, 245
temporal, 134, 136, 178, 183
Linea alba, 416
aspera, 246
quadrata, 246
semicircularis, 416
splendens, 879
Linece semilunares, 417
Lingua, 1125
fades inferior , 1125
tunica mucosa, 1131
Lingual artery, 553
deep, 553
bone, 177
branches of glossopharyngeal
nerve, 909
gyrus, 823
lamina, 1122
lymph glands, 694
nerve, 895
tonsil, 1131
veins, 648
Lingula cerebelli, 789
of cerebellum, 789
of mandibulse, 173
of sphenoid, 148, 192
Linin, 36
Lip, tympanic, 1055
vestibular, 1055
Lips, 1111
Liquor amnii, 50
sanguinis, 503
Lissauer, fasciculus of, 762
tract of, 762
Littre, urethral glands of, 1235
Liver, 1188
bare area of, 1150
bile duets of, 1197
common, 1198
cystic duct, 1198
development of, 1193
excretory apparatus of, 1197
fixation of, 1193
fossae of, 1191
gall-bladder, 1197
hepatic artery, 603, 1196
cells, 1196
duct, 1197
veins, 680
ligaments of, 1192
lobes of, 1191, 1192
lobules of, 1195
longitudinal fissures of, 1191
lymphatic capillaries in, 685
vessels of, 711
nerves of, 1194
portal vein, 681, 1196
structure of, 1195
surface markings of, 1320
surfaces of, 1188
vessels of, 1194
Lobe or Lobes, cacuminal, 790
of cerebellum, 788
of cerebral hemisphere, 821
frontal, 821
insula, 825
limbic, 825
occipital, 823
olfactory, 826
parietal, 822
precuneus, 823
quadrate, 823
temporal, 823
of liver, 1191,1192
of lung, 1097
nodular, 791
Spigelian, 1192
of thymus, 1273
of thjToid gland, 1269
tuberal, 791
uvular, 791
Lobule of auricula, 1034
bi ventral, 791
inferior semilunar, 791
paracentral, 822
parietal, 823
postero-inferior, 790
postero-superior, 791
Lobules of liver, 1 195
of testes, 1243
Lobuli glandules thyreoidece, 1269
hepatis, 1195
Lobulus centralis, 790
parietalis inferior, 823
superior, 823
semilunaris inferior, 791
superior, 790
Lobus caudatus, 1192
clivi, 790
culminis, 790
frontalis, 821
hepatis dexter, 1191
sinister, 1192
noduli, 791
occipitalis, 823
olfactorius, 826
parietalis, 822
pyramidis, 791
quadratus, 1192
semilunaris, 790
temporalis, 823
tuberus, 791
uvula, 791
Localization, cerebral, 849
1372
INDEX
Lockwood, tendon of, 1022
Locus cceruleus, 800
Locwenthal's tract, 872
Long bones, 79
buccal nerve, 895
calcaneocuboid ligament, 354
ciliary nerves, 888
external lateral ligament, 341
or internal saphenous nerve, 956
root of cUiarj' ganglion, 888
saphenous nerve, 956
vein, 669
subscapular nerve, 934
thoracic artery, 588
nerve, 933
Longissimus capitis muscle, 399
cervicis muscle, 399
dorsi muscle, 399
Longitudinal fasciculus, inferior,
844
posterior, 803
superior, 844
fissure, cerebral, 818
great, 818
of liver, 1191
sinuses, 654, 655
striae, lateral and medial, 827
sulci of heart, 527
Longitudinalis linguse inferior
muscle, 1130
superior muscle, 1130
Longus capitis muscle, 349
actions of, 396
nerves of. 395
coUi muscle, 394
action of, 396
nerves of, 396
Loop of Henle, 1223
Lower extremity, arteries of, 623
articulations of, 333
bones of, 231
lymphatic glands of, 701
vessels of, 701
muscles of, 465
surface anatomy of, 1336
markings of, 1342
veins of, 669
jaw, bones of, 172
lateral cartilage, 993
visual centers, 814
Lower, tubercle of, 531
Lumbar aponeurosis, 397
arteries, 612
enlargement of medulla spina-
lis, 752
fascia, 397
lymph glands, 705
nerves, anterior, 948
posterior, 924
plexus of nerves, 949
regions of abdomen, 1149
triangle, 434
vein, ascending, 667, 678
veins, 678
vertebrae, 104
Lumbocostal arch, 404
Lumbodorsal fascia, 397
Lumbosacral plexus, 948
trunk, 948
Lumbricales muscles of foot, 493
actions of, 496
ner\-es of, 495
variations of, 493
of hand, 464
actions of, 465
nerves of, 405
A'ariations of, 464
Lunate bone, 224
surface of acetabulum, 237
Lung-buds, 1071
Lungs, 1093
development of, 1071
fissures and lobes of, 1096
nerves of, 1100
root of, 1097
Lungs, structure of, 1098
surface markings of, 1310
vessels of, 1100
Lunulie of nails, 1066
of semilunar valves, 533
Luschka, foramina of, 877
gland of, 1281
Luys, nucleus of, 812
Lymph Gland or Glands of abdo-
men, 703
aortic, 705
auricular, 693
axillarj-, 699
buccinator, 694
cer\dcal, 697
of Cloquet, 703
deltoideopectoral, 699
diapliragmatic, 715
epigastric, 704
of face, 692
facial, 694
gastric, 706
gastroepiploic, right, 706
of head, 692
hepatic, 706
hvpogastric, 704
iliac, 703. 704
ileocolic, 709
infraorbital. 694
inguinal, 702
intercostal, 715
internal mammary, 715
lingual, 694
of lower extremity, 701
lumbar, 705
mastoid, 693
maxillary, 094
mediastinal, 717
mesenteric, 709, 710
mesocolic, 709
of neck, 697 .
obturator, 704
occipital, 692
pancreaticoduodenal. 710
pancreaticolicnal, 706
pararectal. 710
paratracheal, 697
parietal. 703
parotid, 693
of pelvis, 703
popliteal, 701
preauricular, 693
retropharyngeal, 694
of Rosenmiiller, 703
sacral, 704
splenic, 706
Stahr, middle gland of, 697
sternal. 715
structure of, 688
subinguinal, 702
submaxillary. 697
submental, 697
suprahyoid, 697
supramandibular. 694
supratrochlear, 699
of thorax, 715
tibial, anterior, 701
of tongue. 696
tracheobronchial, 717
of upper extremity, 699
visceral, of abdomen and
pelvis, 706
path, 688
sinus, 689
Lymphatic capillaries, 684
distribution of, 684
duct, right, 691
nodules, aggregated, 1176
solitarj-, 1176
of spleen, 1285
system, 683
trunks, bronchomediastinal,
691, 692. 717
intestinal, 691
jugular, 691, 692
Lymphatic trunks, lumbar, 691
subclavian, 691, 692
vessels, 687
of abdomiBal viscera, 710
wall, 706
of anal canal and anus, 711
of auricula and external
acoustic meatus, 694
of bladder, 712
of cecum, 710
of colon, 711
of common bile-duct, 711
development of, 768
of diaphragm, 717
of ductus deferens, 713
of duodenum, 710
of esophagus, 719
of external genitals, 706
of face, 695
of gall-bladder, 711
of gluteal region, 703
of heart, 718
of ileum, 710
of jejunum, 710
of kidney, 712
lacteals, 683
of larynx, 698
of liver, 711
of lower extremity, 703
of lungs, 718
of mamma, 715
of mouth, 695
of nasal cavities, 695
of neck, 698
of ovary, 714
of palatine tonsil, 695
of pancreas, 711
of peh-ic viscera, 710
of pelvis, 706
of perineum, 706
of pharynx, 698
of pleura, 719
of prostate, 713
of rectum, 711
of reproductive organs, 713
of scalp, 694
of spleen, 711
of stomach, 710
structure of, 687
of suprarenal glands, 711
of testes, 713
of thoracic viscera, 718
wall, 715
of thymus, 719
of thyroid gland, 698
of tongue, 696
of upper extremity, 700
of ureter, 712
of urethra, 713
of urinary organs, 712
of uterine tube, 714
of uterus, 714
of vagina, 714
of vermiform process, 710
of vesiculse seminales, 713
Lymphocyte, 504
Lymphoglandulw , 688
auriculares, 693
axillares, 699
cervicales, 697
epigastrica , 704
facialcs profunda, 694
gastriccr, 706
hepaticw, 706
hypogastriccp, 704
inguinales, 702
inter costales, 715
linguales, 694
lumbales, 705
mediastinales , 717
mesenteric^ , 709
mesocoliccc, 709
occipitales, 692
pancreaticolienales, 706
poplitecE, 701
INDEX
1373
Lumphoglandula , sternales, 715
subinguinales, 702
submaxillares, 697
tibialis anterior, 701
Lyra of fornix, 838, 869
M
Macewen, suprameatal triangle
of, 140
Mackenrodt, ligament of, 1261
Macula acuslica sacculi, 1052
utriculi, 1051
cribrosa media, 1047
superior, 1048
lutea, 1015, 1017
structure of, 1017
Majendie, foramen of, 798, 877
Malar bone, 104
process of maxilla, 161
Male genital organs, 1236
bulbourethral glands, 1213,
1253
ductus deferens, 1245
ejaculatory duct, 1247
penis, 1247
prostate, 1251
testes and their coverings,
1236
vesicuhe seminales, 1246
pronucleus, 45
urethra, 1234
Malleolar arteries, 635
folds, 1039
sulcus, 260
^lalleolus, lateral, 260
medial, 259
Malleus, 1044
development of, 1033
ligaments of, 1045
Malpighian bodies, kidney, 1221
of spleen, 1285
capsules of kidney, 1221
MammEe, 1267
development of, 1267
lymphatic vessels of, 715
nerves of, 1268
papilla or nipple of, 1267
structure of, 1267
vessels of, 1268
Mammary arteries, 583, 588
gland, 1267
internal, 715
veins, internal, 666
Mammillary process, 106
Mammillo-thalamic fasciculus,
869
Mandible, 172
angle of- 174
articulations of, 175
body f f, 172
changes in, due to age, 175
condyloid process of, 174
coronoid process of, 174
ossification of, 174
ramus of, 173
Mandibula, 172
Mandibular arch, 66
branches of facial nerve, 905
canal, 173
foramen, 173
fossa, 140, 180, 183
nerve, 893
notch, 174
Mantle layer, 733
Manubrium of malleus, 1044
of sternum, 119
Margin, supraorbital, 135
Marginal g>Tus, 822
layer, 733
veins of foot, 669
Margins of heart, 529
Marrow of bone, 87
Marshall, oblique vein of, 522,
526, 643
vestigial fold of, 522, 526, 643
Martinotti, cells of, 845,
Massa intermedia, 809, 816
Masses, lateral, of atlas, 99
Masseter muscle, 385
action of, 387
nerves of, 387
Masseteric artery, 561
fascia, 385
nerve, 894
Mastoid canaliculus, 144, 181
cells, 142
foramen, 141, 183
fossa, 140
glands, 693
notch, 141, 181
portion of temporal bone, 141
process, 141
Mastzellon, 377
Matrix of nail, 1066
Maturation of ovum, 40
Maxilla, 157
articulations of, 163
changes in, due to age, 163
ossification of, 163
Maxillary artery, external, 553
peculiarities of, 556
internal, 559
glands, internal, 694
nerve, 889
inferior, 893
process of inferior nasal concha,
169
of palatine bone, 168
of zygomatic bone, 166
processes of fetus, 66
sinus, 159, 999
tuberosity, 159
vein, internal, 646
Meatus acusticus extemus, 1036
cartilagineus , 1036
osseus, 1036
auditory, external, 1036
external acoustic, 145, 183 1036
internal, 146, 193
urinarius, 1235
urinary, 1266
Meatuses of nose, 195, 994, 995
Mechanics of muscle, 362
Mechanism of pelvis, 311
of respiration, 407
of thorax, 304
Meckel's cartilages, 66, 174
diverticulum, 54, 1172
ganglion, 891
Media, refracting, of bulb of eye,
1018
Medial geniculate body, 811
lemniscus, 804
longitudinal fasciculus, 803
wall of nasal cavity, 995
Median antibrachial vein, 662
basilic vein, 661
nerve, 938
Mediastinal arteries from aorta,
600
from internal mammary, 583
lymph glands, 717
pleura, 1088
Mediastinum, 1090
testis, 1243
Medicornu, 831
Medidural artery, 560
Medifrontal gvre, 822
Medulla of hair, 1069
oblongata, 767
anterior district of, 768
arcuate fibers of, 782
development of, 739
fasciculus cuneatus, 776
gracilis, 776
fissures and sulci of, 767, 768
gray substance of, 779
Medulla oblongata, formalio reti-
cularis, 784
lateral district of, 769
olive of, 709
posterior district of, 774
pyramid of, 768
restiform bodies of, 782
structure of, 775
spinalis, 749
central canal of, 754
columns of, 753
development of, 749
distribution of nerve cells in,
755
enlargements of, 751
fissures of, 752
gray commissures of, 754
substance of, 753
ligamentum denticulatum , 877
meninges of, 872
neuroglia of, 753
sulci of, 752
veins of, 669
white commissure of, 752
substance of, 758
Medullary artery of bone, 88
lamina, 810
lamince of lentiform nucleus,
834
membrane of bone, 87
portion of suprarenal gland,
1280
segments of nerves, 727
sheath of nerve-fibers, 725, 726
spaces of bone, 94
substance of kidney, 1221
velum, 793, 797
Medullated nerve-fibers, 724
Meibomian glands, 1026
Meissner's plexus, 1177
tactile corpuscles, 1061
Membrana allantouccipitalis. An-
terior, 295
posterior, 296
granulosa [of Graafian follicle],
1256
hyothyreoidea, 1076
interossea antebrachii, 325
cruris, 348
pupillaris, 1014
tectoria [of atlas and occipital
bone], 296
Membrane, anal, 1110
arachnoid, 876
atlantooccipital, 295, 296
basilar, 1054, 1056
of Bowman, 1008
costocoracoid, 437
cricothyroid, 1078
of Demours, 1008
of Descemet, 1008
elastic, of larynx, 1077
fenestrated, 498
hyaloid, 1018
hyoglossal, 1132
hyothyroid, 1076
intercostal, 403
interosseous, of forearm, 325
of leg, 348
Jacob's, 1017
of Krause, 375
limiting, 1017
rneduUarv, of bone, 87
of Nasmyth, 1123
nuclear, 36
obturator, 476
pharyngeal, 1101
pupillary, 1003, 1014
of Reissner, 1054
tectorial, of ductus cochlearis,
1058
thyrohyoid, 1076
tympanic, 1039
vestibular, 1054
vitelline, 45
1374
INDEX
Membranes of brain and medulla
spinalis, 872
fetal, 54
synovial, 279
Membranous cochlea, 1054
cranium, 84
labyrinth, 1015
portion of urethra, 1235
semicircular canals, 1052
vertebral column, 81
Meningeal artery, accessory, 561
anterior, 568
from ascending pharyngeal,
558
middle, 560
surface marking of, 1294
from occipital, 557
from vertebral, 579
branch of spinal nerve, 921
layer of dura mater, 875
nerve from hypoglossal, 918
from maxillary, 889
Meninges of brain and medulla
spinalis, 872
Menisci, 281
of knee-joint, 342
Meniscus, articular, 298
Mental foramen, 172, 188
nerve, 897
point, 198
protuberance, 172
spines, 172
tubercle, 172
Mentalis muscle, 383
Mentohyoideus muscle, 392
Merkel, tactile disks of, 1059
Meroblastic ova, 45
Mesencephalon, 51, 741, 800
Mesenteric arteries, 606, 609
lymph glands, 709
plexuses of nerves, 987
veins, 681, 682
Mesenteries, 1157
mesentery proper, 1157
sigmoid mesocolon, 1153, 1157
transverse mesocolon, 1157
Mesenteriole of vermiform pro-
cess, 1178
Mesenterium, 1157
Mesocardium, arterial, 526
venous, 526
Mesocolic lymph glands, 709
Mesocolon, sigmoid, 1153, 1157
transverse, 1157
Mesoderm, 49
formation of, 47
Mesogastrium, 1103
Mesognathion, 199
Mesonephros, 1205
Mesorchium, 1207
Mesosalpinx, 1261
Mesovarium, 1207, 1255
Metacarpal bones, 227
articulations of, 230
characteristics of, 228
ossification of, 230
Metacarpophalangeal articula- '
tions, 332
Metacarpus, 227
Metanephros, 1205
Metaphase of karyokinesis, 37
Metatarsal arteries, 637
bones, 272
characteristics of, 272
veins, 672
Metatarsophalangeal articula-
tions, 359
Metatarsus, 272
ossification of, 275
Metathalamus, 743, 811
Metencephalon, 738
Metopic suture, 135
Meynert, basal optic nucleus of,
813
fasciculus retroflexus of, 812
Meynert, fountain decussation
of, 806
substantia innominata of, 837
Microcytes, 503
Mid-brain, 54, 741, 800
Mid-carpal joint, 329
Middle capsular artery, 610
cerebellar peduncles, 793
commissure of brain, 809
constrictor muscle, 1 143
costotransverse ligament, 302
cutaneous nerve, 955
dental nerve, 891
subscapular nerve, 934
thyrohyoid ligament, 1077
tibiofibular ligament, 348
Milk teeth, 1118
Mitochondria sheath, 43
Mitral cells, 848, 997
orifice, 534
valve, 534
Moderator band, 532
Modiolus of cochlea, 1050
Molar glands, 1112
teeth, 1118
Molecular layer of cortex of
cerebellum, 794
of cerebrum, 845
Monakow, rubrospinal fasciculus
of, 761
Monaster or mother star, 37
Monro, foramen of, 816, 840
sulcus of, 741, 816
Mons pubis, 1265
Veneris, 1265
Morgagni, hydatid of, 1207, 1242,
1257
rectal columns of, 1184
sinus of, 1143
Morula, 46
Moss fibers, 796
Mother star or monaster, 37
Motor areas of cerebral cortex,
847
end-plates, 730
nerves, 730
neurons, lower and upper, 870
tract, 870
Mott, spino-quadrigeminal sys-
tem of, 762
Mouth, 1110
development of, 1101
lymphatics of, 695
mucous membrane of, 1110
muscles of, 382
variations of, 385
Movable articulations, 285
Movements admitted in joints,
286
Mucous glands of tongue, 1131
sheaths, 283
of tendons around ankle, 489
on back of wrist, 459
on front of wrist, 457
Miiller, orbitalis mugcle of,
1024
sustentacular fibers of, 1017
Mullerian duct, 1206
eminence, 1207
Multangular bones, 225
Multicuspid teeth, 1118
Multifidus muscle, 400
action of, 402
nerves of, 402
spinse muscle, 400
Muscle or Muscles of abdomen,
408
abductor hallucis, 491
digili quinti (foot), 492
(hand), 463
indicis, 464
minimi digiti, 463
pollicis, 461
brevis, 461
longus, 455
Muscle or Muscles, accelerator
urina;, 428
accessorius, 399
of foot, 493
action of, on joints, 368
adductor brevis, 473
hallucis, 493
longus, 472
magnus, 473
minimus, 474
obliquus hallucis, 493
pollicis, 462
pollicis obliquus, 462
transversus, 462
of anal region, 424
anconccus, 454
anterior crural, 480
femoral, 467
vertebral, 394
anterolateral, of abdomen, 408
antitragicus, 1035
of arm, 442
development of, 371
arrectores pilonmi, 1069
arlicularis genu or subcrureus,
471
aryepiglotticus, 1083
arytcenoideus, 1082
attollens aurem, 1035
attrahens aurem, 1035
of auricula or pinna, 1035
auricularis, 1035
axillary arch, 434
azygos uvula, 1139
of back, 396
biceps, 433
brachii, 433
femoris, 478
flexor cubiti, 443
biventer cervicis, 400
Bowman's, 1011
brachialis, 444
anticus, 444
brachioradialis, 451
buccinator, 384
bulbocavernosus, 428, 430
caninus, 383
cardiac, 536
cervical, 387, 388
cervicalis ascendens, 399
chondro-epitrochlearis, 437
chondroglossus, 1130
ciliaris, 1010
cleidohyoideus, 393
coccygeus, 424
columns, 374
complexus, 400
compressor naris, 382
urethrce, 429, 431
constrictors of pharj^nx, 1142
urethra;, 429, 431
coracobrachialis , 443
corrugator, 381
cutis ani, 425
supercilii, 381
costocoroideus, 437
cremaster, 414
cricoarytcenoideus, 1082
cricoarytenoid, 1082
cricothyreoideus, 1081
cricothyroid, 1081
crureus, 471
deltoid, 439
deltoideus, 439
depressor alae nasi, 382
anguli oris, 383
labii inferioris, 383
septi, 382
detrusor urince, 1233
development of, 371
diaphragm, 404
digastric, 391
digastricus, 391
dilatator naris, 382
pupillcB, 1013
INDEX
1375
Muscle or Muscles, dilatator tubes,
1044
dorsal antibrachial, 451
dorsoepitrochlearis brachii, 434
ejaculator uriwc, 428
epicranius, 37S
epitrochleo-aiieona?us, 448
erector cliloridis, 430
penis, 428
spince, 397
extensor carpi radialis acces-
sorius, 452
breWor, 452
brevis, 452
intermedius, 452
longior, 452
longus, 452
ulnaris, 454
coccygis, 401
digili qiiinti proprius, 454
digitoruni brevis, 490
conununis, 452
longus, 481
hallucis longus, 481
indicis, 456
proprius, 456
minimi digiti, 454
ossis metacarpi hallucis, 481
pollicis, 455
poinds brevis, 455
longus, 455
primi internodii pollicis, 455
Ijroprius hallucis, 481
seeundi internodii pollicis, 455
external sphincter ani, 425
of eyelids, 380
fasciculi of, 373
fibers of, 373
fixation, 362
flexor accessorius, 493
longus digitorum, 485
brevis minimi digiti, 464, 494
carpi radialis, 446
ulnaris, 447
digiti quintl brevis [foot], 494
[of hand], 464
digitoruni brevis, 491
longus, 485
profundus, 448
sublimis, 448
hallucis brevis, 493
longus, 485
pollicis brevis, 461
longus, 449
of foot, 490
of forearm, 445
form of, 361
frontalis, 379
gastrocnemius, 482
gemellus, 477
genioglossus, 1129
geniohyoglossus, 1129
geniohyoid, 393
geniohyoideus, 393
glossopalatinus, 1129, 1139 noie
gluticus maximus, 474
medius, 474
minimus, 475
of gluteal region, 474
gracilis, 471
hamstring, 478
of hand, 456
of head, 378
development of, 372
helicis major, 1035
minor, 1035
hyoglossus, 1129
of iliac region, 466
iliacus, 467
minor, 467
iliocapsularis, 467
iliococcygeus , 424
ilioeostalis, 399
cervicis, 399
dorsi, 399
Muscle or Muscles, ilioeostalis
lumborum, 399
iliosacralis, 424
incisivus labii, 385
infracostal, 403
infrahyoid, 391
infraspinatus, 441
insertion of, 362
intercostal, 402, 403
inter CO stales, 402. 403
intermediate volar, 465
internal sphincter ani, 426
'interossei, dorsal, 495
of foot, 495
of hand, 464
plantar, 495
inter spinales, 400
intertransversales, 401
intertransversarii , 401
ischiocavernosus, 428, 430
of larynx, 1081
lateral cervical, 388
crural, 486
vertebral, 396
volar, 401
latissimus dorsi, 432
of leg, 480
development of, 372
levator anguli oris, ,383
scapula;, 435
ani, 422
cla\dculiE, 435
glandulce thyreoidea:, 1270
Tnenii, 383
palati, 1139
palpebroc superioris, 1021
prostatce, 424
scapula;, 435
veli palatini, 1139
levatores costarum, 403
lingualis, 1130
longissimus capitis, 399
cervicis, 399
dorsi, 399
longitudinalis lingua', 1130
longus capitis, 395
coZZi, 394
of lower extremity, 465
lumbricales [of foot], 493
[of hand], 404
lymphatics of, 376
■ masseter, 385
of mastication, 385
mechanics of, ,362
medial femoral, 471
volar, 462
mentalis, 383
mentohyoideus, 392
of mouth, 382
multifidus, 40G
spinte, 400
mylohyoid, 393
mylohyoideus, 393
nasalis, 382
nasolabialis, 38.5
nerves and vessels of,
376
of nose, 382
oblique, 409, 412
inferior, 1023
superior, 1022
obliquus auricula", 1035
capitis, 402
exlernus abdominis, 410
inferior, 402
internus abdominis, 412
oculi, 1022, 1023
superior, 402
obturator externus, 477
internus. All
occipitalis, 379
occipitofrontalis, 378
ocular, 1021
omohyoid, 394
omohyoideus, 394
Muscle or Muscles, opponens digiti
quinti [of foot], 494
[of hand], 464
minimi digiti, 464
pollicis, 401
orbicularis oculi, 380
oris, 384
palpebrarum, 380
orbitalis of H. Miiller, 1024
origin of, 362
of palate, 1139
palatoglossus, 1129, 1139 note
palatopharyngeus, 1139
palmaris brevis, 463
longus, 446
pectineus, 472
pectoralis major, 436
minimus, 438
minor, 438
of pelvrs, 420
perineal, superficial transverse,
427, 430
of perineum, 424
peronseus accessorius, 487
brevis, 487
longus, 486
quartus, 487
quinti digiti, 487
tertius, 482
peroneocalcaneus externum,
487
internus, 485
pcroneocuboideus, 487
pcroneotibialis, 48.5
pharyngopalaiinus, 1139
of pharynx, 1142
of pinna or auricula, 1035
piriformis, 476
pisiannularis, 464
pisimetacarpus, 464
pisiuneinatus, 404 «
plantar, first layer, 491
fourth layer, 495
second layer, 493
third layer, 493
planiaris, 483
plate, 80
platysma, 388
popliteus, 484
minor, 485
posterior crural, 482
femoral, 478
procerus, 382
pronator quadratus, 449
teres, 446
psoas magnus, 467
major, 467
minor, 467
parvus, 467
pterygoid, 386
pterygoideus externus, 388
internus, 387
pubococcygeus, 424
puborectalis , 424
pubovesicales, 1231
pull, action of, on tendon, 364
direction of, 363
pyramidalis abdominis, 416
nasi, 382
quadratus femoris, ill
labii, 383
lumborum, 420
menti, 383
planta;, 493
quadriceps extensor, 470
femoris, 470
recti [of eyeball], 1022
rectococcygeal, 1186
rectovesicales , 1231
rectus abdominis , 415
capitis anterior, 395
lateralis, 395
posterior, 401
anticus, 395
posticus, 401
1376
INDEX
Muscle or Muscles, rectus femoris,
470
retrahens aurem, 1035
rhomboideus major, 434
minor, 434
ocfipitalis, 435
risorius, 385
rotatores, 400
spina;, 400
sacrospinalis, 397
salpingopharyngeus, 1143
sarcous elements of, 375
sartorius, 470
scalenus anterior, 396
anticus, 396
medius, 396
pleuralis, 396
posterior, 396
posticus, 396
of scalp, 378
semimembranosus, 479
semispinaHs capitis, 400
cervicis, 400
colli, 400
dorsi, 400
semitendinosus, 479
sense, impulses of, 851
serratus anterior, 438
magnus, 529
posterior, 404^
posticus, 404
soleus, 493
sheaths, lymphatic capillaries
in, 684
of shoulder-girdle, development
of, 371
sphincter ani, 425
externus, 425
internus, 426
pupilUv, 1013
^ recti, 424
urethra' 7nem67'onace«E,429,431
vagina:, 430
vesiccE, 1233
spinalis capitis, 400
cerKicts, 400
colli, 400
rfors?, 399
splenius capitis, 397
cervicis, 397
colli, 397
stapedius, 1040
sternalis, 437
sternoclavicularis, 438
sternocleidomastoideus, 390
sternohyoid, 393
sternohyoideus, 393
sternomastoid, 390
sternothyreoideus, 393
sternothyroid, 393
strength of. 304
striped, 373
styloglossus, 1130
stylohyoid, 392
stylohyoideus, 392
stylopharyngeus . 1143
subancona-us, 445
subclavius, 438
subcostales, 403
subcrureus, 471
suboccipital, 401
suhscapiilaris, 440
superficial cervical, 387
supinator, 454
brevis, 454
longus, 451
suprahyoid, 391
supraclavicularis, 390
supracostalis, 403
supraspinatus, 440
suspensory, of duodenum, 1170
synergic, 362
temporal, 386
temporalis, 386
tendons of, 376
Muscle or Muscles, tensor palati,
1139
tarsi, 380
tympani, 1046
t)eK palatini, 1139
ieres major, 442
minor, 441
of thigh, 467
of thorax, 402
tibiofacialis anterior, 480
thyreoaryt(enoideus, 1083
thyreoepiglotticus, 1083
thyrohyoideus, 394 *
thyroarytenoid, 1083
thyrohyoid, 394
tibialis anterior, 480
anticus, 480
posterior, 485
of tongue, 1128
irachealis, 1087
trachelomastoid, 399
tragicus, 1035
transversalis, 414
cervicis, 399
transversus abdominis, 414
auricula;, 1035
linguce, 1130
menti, 3S3
nuchcE, 380
pedis, 493
perinaei, 427, 429
profundus, 429, 431
superficialis [in female], 430
[in male], 427
thoracis, 403
trapezius, 432
triangularis, 383
sterni, 403
triceps, 444
brachii, 444
extensor cubiti, 444
swro", 483
of trunk, 396
of tympanic cavity, 1046
of upper extremity, 432
of ureters, 1232
urogenital region [female], 430
[male], 426
of uvula, 1139
vastus externus, 470
intermedius. 471
internus, 471
latei-alis, 470
medialis, 471
ventricularis, 1083
ventrolateral, of neck, develop-
ment of, 371
vertebral, 394, 396
verticalis linguce, 1131
vocalis, 1083
volar antibrachial, 445
voluntary, 373
■work accomi)lished by, 365
zygomaticus, 383
major, 383
Muscular fibers of heart, 535
process of arytenoid cartilage,
1075
triangle, 394, 563
Muscularis mucoscr, 1173
Musculi oculi, 1021
ossiculorum attditus, 1046
papillares [of left ventricle], 534
[of right ventricle], 532
peclinati [of left auricle], 534
[of right auricle], 529
pubovesicales, 1232
Musculocutaneoua nerve of arm,
935
of leg, 966
Musculophrenic artery, 583
Musculospiral groove, 211
nerve, 943
Myelencephalon, 738
Myelocytes, 88
Myeloplaxes, 88
Mylohyoid artery, 5G1
groove, 173
line, 173
muscle, 393
nerve, 896
Mylohyoideus muscle, 393
action of, 393
nerves of, 393
variations of, 393
Myocardium, 535
Mvocel, 52
Myology, 361
N
Nails, 1066
Nares, 992, 994
Nasal aperture, anterior, 196
artery, 571
lateral, 556
bones, 156
articulations of, 157
ossification of, 157
cartilages, 992. 993
cavities, 194, 994
arteries of, 996
lymphatic capillaries in, 686
vessels of, 695
mucous membrane of, 996
nerves of, 996, 997
veins of, 997
vestibule of, 994
concha, inferior, 169
middle, 156
superior, 156
crest, 163, 167
duct, 1029
fossa, 994
index, 198
laminw, 68
mucous membrane, 996
nerve from ophthalmic, 888
nerves from nasopalatine gan-
glion, 893
notch of frontal bone, 136
of maxilla, 158
part of frontal bone, 136
of pharynx, 1141
process of frontal bone, 136
of maxilla, 161
processes of fetus, 67
septum, 194, 995
spine, anterior, 158. 163
of frontal bone. 136
posterior, 167, 180
Nasalis muscle, 382
action of, 382
nerves of, 382
Nasion, 136, 186, 198
Nasmyth's membrane, 1123
Nasociliary nerve, 888
Nasofrontal vein, 659
Nasolabialis muscle, 385
Nasolacrimal duct. 1029
Nasooptic furrow, 69, 1005
Nasopalatine nerve, 893
recess, 996
Nasopharynx, 1141
Nasus externus, 992
Navicular bone of carpus, 221
of tarsus, 270
fossa, 1266
Neck, lymphatic glands of, 697
vessels of, 698
muscles of, 387
development of, 371
triangles of, 562
veins of. 646
Nelaton's line, 1342
Neopallium, 744
Nerve cells, 721
of cerebellar cortex. 794
of cerebral cortex, 845
INDEX
13
/ i
Nerve cells of medulla spinalis,
755, 757
endings, free, 1059
fasciculi of medulla spinalis, 759
fibers of cerebral cortex, 846
medullated, 724
non-medullated, 728
roots, 916, 948
N^erve or Nerves, abducent, 899
accessory, 913
acoustic, 905, 1058
alveolar, 890, 891
inferior, 895
anococcygeal, 968
anterior crural, 953
interosseous, 938
superior alveolar, 891
thoracic, 933
tibial, 965
antibrachial cutaneous, 936,
937
Arnold's, 911
auditory, 905
auricular of auriculotemporal,
895
great, 926
posterior, 905
of vagus, 911
auriculotemporal, 895
axUlary, 934
brachial cutaneous, lateral, 934
medial, 937
posterior, 943
bronchial, 913
buccal, of facial, 905
long, 895
buccinator, 895
calcaneal, medial, 963
cardiac, cervical, 912
great, 979
of sympathetic, 979
thoracic, 912
of vagus, 912
caroticotympanic, 978, 1047
carotid of glossopharyngeal,
909
cavernous, of penis, 989
celiac, of vagus, 913
cerebral, 881. See Cranial,
cerebrospinal, structure of, 728
cervical, 928
cutaneous, 927
divisions of, 921, 925
of facial, 905
transverse, 927
chorda tj'mpani, 904, 1047
ciliary, 888, 889
circumflex, 934
of clitoris, 968
coccygeal, division of, 925, 957
cochlear, 906, 1059
cranial, 881
abducent, 899
accessory, 913
acoustic, 905
central tract of, 804
composition and central con-
nections of, 855
facial, 901
glossopharyngeal, 906
hypoglossal, 914
oculomotor, 884
olfactorv, 881
optic, 882
thalamic tract of, 805
trigeminal, 886
trochlear, 885
vagus, 910
crural, anterior, 955
cutaneous cervical, 927
external, 953
internal, 937, 955
lesser, 937
middle, 955
deep branch of radial, 944
87
Nerve or Nerves, deep branch of
ulnar, 943
peroneal, 965
petrosal, 892
temporal, 894
descending ramus of hypo-
glossal, 918
development of, 735, 747
digastric, from facial, 905
digital, of lateral plantar, 963
of medial plantar, 963
of median, 938
of radial, 944
of superficial peroneal, 966
of ulnar, 943
dorsal antibrachial cutaneous,
944
branch of ulnar, 942
cutaneous, 963, 966
digital, 9G5
of penis, 968
scapular, 932
of dura mater, 875
dural, 911
eighth, 905
eleventh, 913
end-organs of, 1059
endoneurium of, 728
epineurium of, 728
esophageal, 913
external nasal, 891
plantar, 963
popliteal, 964
saphenous, 963
spermatic, 953
facial, 901
femoral, 955
cutaneous, anterior, 955
lateral, 953
posterior, 959
fifth, 886
first, 881
fourth, 885
frontal, 887
ganglia of, 730
gastric branches of vagus,
913
genitocrural, 953
genitofemoral, 953
glossopharyngeal, 906
gluteal, 959, 960
great auricular, 926
greater occipital, 923
splanchnic, 981
superficial petrosal, 892
hemorrhoidal, inferior, 968
hepatic branches of vagus, 913
hypoglossal, 914
iliohypogastric, 950
ilioinguinal, 952
incisive, 897
inferior dental, 897
infraorbital, 889 note
infrapatellar, 956
infratrochlear, 888
intercostal, 945
intercostobrachial, 946
intermedins of Wrisberg, 901
internal calcaneal, 963
cutaneous of arm, 937
carotid, 977
plantar, 963
popliteal, 960
saphenous, 956
interosseous, dorsal, 944
volar, 938
Jacobson's, 909, 1047
jugular, 978
labial posterior, 968
superior, 891
lacrimal, 887
of Lancisi, 868
laryngeal, 912
laryngopharyngeal of sympa-
thetic, 978
Nerve or Nerves, lateral anti-
brachial cutaneous, 935,
936
brachial cutaneous, 934
femoral cutaneous, 953
plantar, 963
sural cutaneous, 964
lesser splanchnic, 891
lingual, 895
of glossopharyngeal, 909
long ciliary, 888
saphenous, 956
subscapular, 934
thoracic, 933
lowest splanchnic, 981
lumbar, divisions of, 924, 948
lumboinguinal, 953
lumbosacral trunk, 948
mandibular, 893
of facial, 905
masseteric, 894
maxillary, 889
inferior, 893
medial antibrachial cutaneous,
937
brachial cutaneous, 937
sural cutaneous, 962
plantar, 963
median, 938
meningeal, of hypoglossal, 918
of maxillary, 889
middle, 889
of spinal, 916
of vagus, 911
mental, 897
motor, 730
musculocutaneous, of arm, 935
of leg, 966
musculospiral, 943
mylohyoid, 896
nasal, of ophthalmic, 888
from sphenopalatine gan-
glion, 893
nasociliary, 888
nasopalatine, S93
ninth, 906
obturator, 953
accessory, 955
occipital, greater, 923
smaller, 926
third, 923
oculomotor, 884
olfactory, 881
ophthalmic, 887
optic, 882
orbital, 893
origins of, 729
palatine, 893
palmar cutaneous, of median,
938
of ulnar, 942
palpebral, inferior, 891
perforating cutaneous, 967
perineal, 968
perineurium of, 728
plexus of, 728
annular, 1009
aortic abdominal, 987
Auerbach's, 1177
brachial, 930
cardiac, 984
carotid, 977
cavernous, 978
celiac, 985
cervical, 925
posterior, 921, 922, 923
choroid, of fourth ventricle,
798
of lateral ventricle, 840
of third ventricle, 815
coccygeal, 968
of cornea, 1009
coronar\% 985, 987
esophageal, 910, 913
of Exner, 846
1378
INDEX
Nerve or Nerves, plexus of, gas
trie, 918, 9S7
hemorrhoidal, 987
hepatic, 986
hypogastric, 987
infraorVjital, 891
lieual, 986
lumbar, 948
lumbosacral, 948
Meissner's, 1177
mesenteric, 987
myenteric, 1177
ovarian, 987
parotid, 902
patellar, 953, 950
pelvic, 987
pharyngeal, 909, 912, 979
phrenic, 985
prostatic, 988
pudendal, 966
pulmonary, 910, 913
renal, 987
sacral, 957
solar, 985
spermatic, 987
splenic, 986
of submucosa, 1177
subsartorial, 956
suprarenal, 987
tonsillar, 909
tympanic, 1047
uterine, 989
vaginal, 989
vesical, 988
peroneal, 964, 965, 968
petrosal, deep, 892, 977
external, 978
greater superficial, 892
smaller superficial, 1047
large, deep, 892
superficial, 892, 903
pharyngeal, of glossopharyn-
geal, 909
of sphenopalatine ganglion,
893
of vagus, 911
phrenic, 928
plantar, 90^
pneumogastric, 910
popliteal, 960, 694
of pterygoid canal, 892, 977
to pterygoideus externus, 895
internus, 894
pterygopalatine, 893
pudendal, 967
inferior, 960
pudic, internal, 967
pulmonary, 913
radial, 943
rami communicantes, gray and
white, 902, 976
recurrent, 912
reflexes, trigeminal, 899
respiratory, of Bell, 928, 933
to rhomboids, 932
roots, 764, 918
sacral, 957
saphenous, 956, 963
sciatic, 960
scrotal, posterior, 968
second, 882
seventh, 901
short ciliary, 889
sixth, 899
smaller occipital, 926
spermatic, external, 953
sphenopalatine branches of
maxillary, 890
spinal, 916
accessory, 913
composition and central con-
nections of, 849
development of, 735
divisions of, 921, 925
roots of, 764, 916
Nerve or Nerves, splanchnic, 981
to stapedius, 904
stylohyoid, 905
to subclavius, 933
subscapular, 933, 934
superior labial, 891
superficial branch of radial, 944
of ulnar, 942
supra-acromial, 928
supraclavicular, 928
supraorbital, 888
suprascapular, 932
suprasternal, 928
supratrochlear, 888
sural, 963
lateral cutaneous, 964
sympathetic, 968
cranial, 970
sacral, 973
structure of, 729
thoracolumbar, 974
of taste, 992
temporal, deep, 895
of facial, 905
temporomalar, 889
tenth, 910
terminations of, 729
third, 884
thoracic, divisions of, 923, 933
thoracodorsal, 934
thyrohyoid, 918
tibial, 960
anterior, 965
of tongue, 1132
tonsillar, 909
transverse cervical, 927
trifacial, 886
trigeminal, 886
central tract of, 805
trochlear, 885
twelfth, 914
tympanic, of glossopharyngeal,
909, 1047
ulnar, 939
collateral, 943
ot urethral bulb, 968
vagus, 910
vestibular, 906, 1058
Vidian, 892
volar digital, 938
interosseous, 938
of Wrisberg, 937
zygomatic, 889
of facial, 905
zygomaticofacial, 890
zygomaticotemporal, 890
Nervi anococcygei, 968
auriculares anteriores, 895
carotid exlerni, 979
cavernosi penis minores, 989
cerebrales, 881
cervicales, 921, 925
ciliares longi, 888
clunium inferiores, 960
coccygeus, 9^25, 957
communicantes cervicales, 928
hypoglossi, 928
digitales dorsales hallucis, 965
plantares communes, 963
proprii, 963
ethmoidales, 888
intercostales, 945
lumbales, 924
anteriores, 948
posteriores, 924
nervorum, 728
olfactorii, 881
palatini, 893
sacrales, 924, 957, 968
sphenopalatini, 890
spinales, 916
rami anteriores, 925
posteriores, 928
subscapular es, 933
supraclavicular es, 928
Nervi temporales profundi, 895
thoracales, 923
anteriores, 933, 944
Nervous system, description of,
721
development of, 733
Nervus abducens, 899
accessorius, 913
ramus externus, 913
internus, 913
acusticus, 1058
alveolaris inferior, 896
auricularis magnus, 926
posterior, 905
auriculotemporalis, 895
axillaris, 934
buccinatorius , 905
canalis pterygoidei, 892
cardiacus inferior, 981
medius, 979
superior, 979
caroticotympanicus inferior, 909
superior, 909
cavernous penis major, 989
cochlearis, 1059
clunium inferior medialis, 967
inferiores, 960
communicans fibularis, 964
tibialis, 962
cutaneus antebrachii dorsalis,
944
lateralis, 936
medialis, 937
brachii medialis, 937
posterior, 943
colli, 927
dorsalis intermedins, 966
medialis, 966
femoralis lateralis, 953
posterior, 959
surw lateralis, 964
medialis, 962
descendens cervicales, 928
dorsalis clitoridis, 968
penis, 968
scapulce, 932
facialis, 901
rami buccales, 905
temporales, 905
zygomatici, 905
ramus colli, 905
digastricus. 905
marginalis mandibulcc , 905
stylohyoideus, 905
femoralis, 955
frontalis, 887
furcalis, 949
genito femoralis, 953
glossopharyngeus, 906
ganglion pctromim, 908
superius, 908
rami lingualcs, 909
pharyngei, 909
tonsillares, 909
ramus stylopharyngeus, 909
glutwus inferior, 959
' superior, 959
hcemorrJioidalis inferior, 968
hypoglossus, 914
ramus descendens, 916
thyreohyoideus , 916
iliohypogastricus, 950
ilioinguinalis , 952
infratrochlearis, 888
intermedins [of Wrisberg], 901
interosseus dorsalis, 944
volar is, 938
ischiadicus, 960
lacrimalis, 887
laryngeus superior, 912
lingualis, 895
lumboinguinalis, 953
mandibularis, 893
massetericus, 894
maxillaris, 889
INDEX
1379
Nervus maxillaris, rami aheolares
superiores j)o^icTiorcs,
890
labialis superiores, 891
nasales exlerni, 891
palpebrales inferiores, 819
rarnus alveolaris superior an-
teriores, 891
niedius, 891
meatus auditorii externi, 895
medianus, 938
meningeus inedius, 889
musculocutaneus, 935
mylohyoideus, 896
nasociliaris, 888
obturatorius, 953
accessorius, 955
occipitalis major, 923
minor, 926
oculomoiorius , 884
ophthalmicus, 887
opticus, 882
palatinus, 893
perinei, 968
peronacus communis, 964
profundus, 965
petrosus profundus, 892
superficialis major, 892
phrenicus, 928
plantaris lateralis, 963
medialis, 963
pterygoideus externus, 895
inter nus, 894
pudendus, 967
radialis, 943
recwrrcns, 912
saphenus, 956
spermaticus externus, 953
spinosus, 894
splanchnicus , 981
stapedius, 904
subclarius, 933
subscapularis, 932
supraorbitalis , 888
supralrochlearis, 8^8
suralis, 963
thoracalis longus, 933
thoracodorsalis, 934
tibialis, 960, 962, 963
trigeminus, 886
trochlearis, 885
tympanicus, 909
ulnar is, 938
ra??ii musculares, 942
ramus cuianeus palmaris, 942
dorsalis manus, 942
profundus, 943
superficialis, 942
volaris manus, 942
vagus, 910
rami bronchiales, 913
cardiaci, 912
coeliaci, 913
gastrici, 913
hepatica, 913
CBSophagei, 913
ramus auricularis, 911
meningeus, 911
pharyngeus, 911
vestibularis, 1058
zygomaticus, 889
Net-work, carpal, 594
malleolar, 636
Neumann, dentinal sheath of,
1119
Neural arch, 96
canal, 50
crest, 51, 736
folds, 50
groove, 50
tube, 50
Neurenteric canal, 50
Neuroblasts, 733
Neurocentral synchondrosis, 112
Neuroglia, 722
Neurofilia of cord, 754, 755
Neurokeratin, 725
Neurolemma, 725
Neurology, 721
Neuromcres, 750
Neuromuscular spindles, 1061
Neuron theory, 732
Neurons, motor, 870
Neurotendinous spindles, 1001
Neutrophil colorless corpuscles,
504
Nidus avis of cerebellum, 791
Ninth nerve, 906
Nipple or papilla of mamma, 1267
Nissl's granules, 723
Node, atrioventricular, 537
sinoatrial, 537
Nodes of Ranvier, 727
Nodular lobe, 790
Nodule of cerebellum, 790
Moduli lymphatici aggregati, 1176
solitarii, 1176, 1187
Modulus vermis, 790
Non-medullated nerve fibers, 728
Normffi of skull, basalis, 179
frontalis, 185
lateralis, 182
occipitalis, 185
verticalis, 178
Normoblasts, 88
Nose, 992
accessory sinuses of, 998
alar cartilages of, 993
arteries of, 993, 996
cartilage of septum of, 992
cartilaginous frame-work of,
992
cavities of, 994
development of, 67
external, 992
lateral cartilage of, 993
lymphatics of, 695
mucous membrane of, 996
muscles of, 382
variations of, 382
nerves of, 997
veins of, 997
Notch, acetabular, 237
cardiac, 1096
cerebellar, 788
ethmoidal, 137
intertragic, 1034
jugular, 131
lacrimal, 159
mandibular, 174
mastoid, 141, 181
nasal, of frontal, 136
of maxilla, 158
parietal, 141
preoccipital, 818
presternal, 120
of Rivinus, 1038
scapular, 204
sciatic, 234
sphenopalatine, 169
superior thyroid, 1073
supraorbital, 136, 186, 189
ulnar, of radius, 220
umbilical, of liver, 1191
vertebral, 97
Notochord, 52
Nuchal line, 129, 182
Nuck, canal of, 1211, 1261
Nuclear layer of cerebellar cortex,
795
layers of retina, 1016
matrix, 36
membrane, 36
substance, 36
Nucleated sheath of Schwann,
725
Nuclei of cochlear nerve, 788, 906
of glossopharyngeal and vagus
nerves, 779, 780
of oculomotor nerve, 884
Nuclei, olivary, 781
of origin of motor nerves, 881
pontis, 780
of termination of sensory
nerves, 908
of trigeminal nerve, 787, 807
of vestibular nerve, 788, 881
Nucleoli, 37
Nucleus of abducent nerve, 787
of accessory nerve, 913
ambiguus, 779
amygdaUv, 835
amygdaline, 791
amygdaloid, 869
arcuatus, 782
of Bechterew, 788
caudate, 833
caudatus, 833
of a cell, 36
of Darkschewitsch, 812
of Deiters, 788, 803
dentatus [of cerebellum], 796
dorsalis, 758
emboliformis, 796
of facial nerve, 787, 902
fastigii, 796
globosus, 796
of hypoglossal nerve, 779
inferior central, 784
intercalatus, 799
of lateral lemniscus, 906
lateralis, 784
of lens, 1020
lenticular, 834
lentiform, 834
lentiformis, 834
of Luys, 812
of medial longitudinal fascicu-
lus, 803
nervus abducentis, 787
facialis, 787
trigemini, 787
of oculomotor nerve, 807, 884
olivaris superior, 787
olivary, 781, 787
of posterior commissure, 812
pulposus, 82
red, 802
of Roller, 784
segmentation, 45
sensory, 902
trapezoid, 787
of trochlear nerve, 807, 885
of vagus nerve, 780
Nuel, space of, 1058
Nuhn, glands of, 1131
Nutrient artery of bone, 88
Nutritive yolk, 39
Nymphse, 1265
Obelion, 178, 198
Obex, 798
Oblique cord, 325
ligament, 325
line of fibula, 261
of mandible, 172
of radius, 219
muscles, 409, 412
inferior, 1023
superior, 1022
popliteal ligament, 340
ridge of clavicle, 200
sinus of pericardium, 526
vein of left atrium, 526, 643
of Marshall, 526, 643
ObHquis oruli muscles, actions of,
1023
nerves of, 1023
Obliquus auriculse muscle, 1035
capitis inferior muscle, 402
action of, 402
nerves of, 402
1380
INDEX
Obliquus capitis superior muscle,
402
action of, 402
nerves of, 402
externus abdominis muscle, 409
variations of, 412
inferior muscle, 402
internus abdominis muscle, 412
variations of, 414
oculi inferior muscle, 1023
superior muscle, 1022
superior muscle, 402
Obliterated ductus venosus, 681
hypogastric artery, 615
umbilical vein, 681, 1150
Obturator artery, 616
crest, 236
externus muscle, 477
actions of, 478
nerves of, 478
foramen, 237
groove, 237
internus muscle, 477
actions of, 478
fascia of, 420
nerves of, 478
lymph gland, 704
membrane, 476
nerve, 953
accessory, 955
tubercle, 237
vein, 676
Occipital artery, 556 ,
bone, 129
articulations of, 133
basilar part of, 132
lateral parts of, 131
ossification of, 132
squama of, 129
structure of, 123
condyles, 131
crest, internal, 131, 193
fossae, 131
groov'e, 141, 181
lobe, 823
lymph glands, 692
nerve, 923, 926
point, 198
protuberance,129, 130, 182, 183
sinus, 658
sulcus, 823
triangle, 394, 565
vein, 646
Occipitalis muscle, actions of, 380
nerves of, 380
variations of, 380
Occipitoaxial ligaments, 296
Occipitofrontal fasciculus, 844
Occipitofrontalis muscle, 378
Occipitomastoid suture, 183
Occipitotemporal convolution,
823
Ocular muscles, 1021
Oculomotor sulcus, 801
nerve, 884
composition and central con-
nections of, 863
sympathetic efferent fibers
of, 970
Odontoblasts, 1118, 1123
Odontoid ligaments, 296
process of axis, 100
Olecranon, 214
fossa, 212
Olfactory areas, 67
bulb, 820, 848
structure of, 848
cells, 996
fasciculus, 840
hair, 996
lobe, 826
nerves, 881
composition and central con-
nections of, 866
development of, 1001
Olfactory pits, 68
projection fibers, 869
sulcus, 822
tract, 826
trigone, 827
Oliva, 769
Olive, 769
peduncle of, 781
Olivary body, 769
nucleus, 781, 787
Olivospinal fasciculus, 854
Omental bursa, 1152, 1155
recess, 1156
Omentum, gastrocolic, 1157
gastrohepatic, 1156
greater, 1157
lesser, 1156
small, 1156
Omohyoid muscle, 394
Omohyoideus muscle, 394
action of, 394
nerves of, 394
variations of, 394
Ontogeny, 35
Oocytes, 38, 41
Oogonia, 34
Ooplasm, 39
Opening of aorta in left ventricle,
534
aortic, in diaphragm, 406
caval, in diaphragm, 406
of coronary sinus, 530
esophageal, in diaphragm, 406
of inferior vena cava, 530
of pulmonary artery, 531
veins, 533
saphenous, 468
of superior cava, 529
of thorax, 524
Openings, atrioventricular, 531,
534
in roof of fourth ventricle, 798
Opercula of insula, 825
Ophryon, 198
Ophthalmic artery, 568
ganglion, 888
nerve, 887
veins, 658
Opisthion, 181, 198
Opisthotic center of temporal
bone, 164
Opponens digiti quinti muscle,
464
actions of, 464
nerves of, 464
minimi digiti muscle, 464
poUicis muscle, 461
actions of, 462
nerves of, 462
variations of, 462
Optic axis, 1001
chiasma, 814, 883
commissure, 814
cup, 1001
disk, 1015
foramen, 147, 151, 190
groove, 147
nerve, 882
composition and central con-
nections of, 864
radiations, 814
recess, 816
stalk, 742, 1001
thalamus, 808
tracts, 814, 884
vesicle, 742, 1001
Ora serrata, 1014, 1018
Oral cavity, 1110
part of pharj^nx, 1142
Orbicular ligament, 342
Orbicularis oculi muscle, 380
actions of, 381, 385
lacrimal part, 380
nerves of, 381. 385
orbital part, 380
Orbicularis oculi muscle, palpe-
bral part, 380
oris muscle, 384
palpebrarum muscle, 380
Orbiculus ciliaris muscle, 1010
Orbitce, 188
Orbits, 188
relation of nerves in, 900
Orbital fascia, 1025
fissures, 151, 184, 189, 192
gyri, 822
index, 198
nerve, 889
operculum, 825
plates, 137
process of palatine bone, 168
of zygomatic bone, 165
septum, 1026
sulcus, 822
vein, 645
Orbitalis muscle of H. Miiller,
1024
Orbitosphenoids, 151
Organ, enamel, 1123
of Giraldes, 1246
of hearing, 1029
of Rosenmiiller, 1206, 1255
of sight, 1000
of smell, 992
spiral, of Corti, 1056
Organa genitalia rauliebria, 1254
virilia, 1236
oculi accessoria, 1021
Organon auditus, 1029
gustus, 991
olfactorius, 992
spirale [Corti], 1056
visus, 1000
Organs of digestion, 1100
genital, of female, 1254
of male, 1236
of Golgi, 376
of the senses, 991
of taste, 991
urogenital, 1204
vomeronasal, of Jacobson, 71,
996
Orifice, atrioventricular, 531, 533
cardiac, of stomach, 1161
mitral, 534
of mouth, 1110
pyloric, of stomach, 1162
urethral, 1232, 1235, 1266
of uterus, 1259, 1260
vaginal, 1266
Orifices of ureters, 1232
Origin of muscles, 362
Os acetabuli, 238
calcis, 263
capiiatum, 226
coccygis, W*
cordis, 536
coxcE, 231
articulations of, 238
ossification of, 237
structure of, 237
cuboideum, 269
cuneiforme primum, 270
secundum, 271
tertium, 271
ethmoidale, 153
frontale, 135
harnatum, 227
hyoideum, 177
ilii, 231
incisivum, 162
innominatum, 231
ischii, 234
lacrimale, 163
lunatum, 224
magnum, 227
multangulum, 225
naviculare manus, 221
pedis, 270
occipitale, 129
INDEX
13S1
Os palatinum, IGG
parietale, 133
pisiforme, 225
planum, 155
pubis, 236
sacrum, 106
sphenoidale, 147
ate magna, 149
parva, 151
temporale, 138
trigonum, 269
triquetum, 225
zygomaticu m , 1 64
Ossa carpi, 221
cranii, 129
extremilaiis inferioris, 231
superioris, 200
faciei, 156
metacarpalia, 228
metatarsalia, 272
nasalia, 156
sesamoidea, 277
<arsi, 263
Ossein, 91
Ossicles, auditory, 1044
development of, 1033
ligaments of, 1045
Ossicula auditus, 1044
Ossification of atlas, 113
of axis, 113
of clavicle, 202
of coccyx, 114
of ethmoid, 156
of femur, 255
of fibula, 262
of foot, 275
of frontal, 138 .
of hand, 230
of hip bone, 237
of humerus, 213
of hyoid, 178
of inferior nasal concha, 170
intracartilaginous, 93
intramembranous, 91
of lacrimal, 164
of lumbar vertebrae, 113
of mandible, 174
of maxilla, 163
of nasal, 157
,of occipital, 132
of OS coxae or innominatum, 237
of palatine, 169
of parietal, 135
of patella, 256
of radius, 220
of ribs, 127
of sacrum, 113
of scapula, 208
of seventh cervical vertebra,
113
of sphenoid, 152
of sternum, 121
of temporal, 145
of tibia, 260
of ulna, 219
of vertebral column. 111
of vomer, 171
of zygomatic, 166
Osteoblasts, 87
Osteoclasts, 88, 1124
Osteodentin, 1120
Osteogenetic fibers, 92
Osteology, 79
Ostium, abdominal, of uterine
tube, 1257
maxillare, 995
pharyngeal, of auditory tube,
1141
primitive urogenital, 1215
primum [heart], 512
secundum [heart], 512
Otic ganglion, 897
Otoconia, 1054
Outlet of pelvis, 240
Ova, primitive, 1207
Oval area of Flechsig, 764
bundle, 735
Ovaria, 1254
Ovarian arteries, 611
fossa, 1154, 1254
plexus of nerves, 987
veins, 679
Ovaries, 1254
descent of, 1207
development of, 1207
ligaments of, 1254
lymphatic capillaries of, 687
vessels of, 714
nerves of, 1256
structure of, 1255
vesicular or Graafian follicles
of, 1256
vessels of, 1256
Oviduct, 1257
Ovula Nabothi, 1262
Ovum, 35, 38
corona radiata of, 39
coverings of, 40
discharge of, 1256
fertilization of, 44
germinal spot of, 39
vesicle of, 39, 40
implantation or imbedding of,
58
maturation of, 40
mature, 40
segtnentation of, 45
structure of, 38
yolk of, 39
zona pellucida or radiata of,
40
Oxyntic cells, 1167
glands, 1167
Oxyphil colorless corpuscles, 504
Pacchionian glands, 878
Pacinian corpuscles, 1060
Pad, retropubic, 1228
Pain, impidses of, 853
Palatal process of maxilla, 162
Palate, 1112
arches of, 1112
bone, 166
development of, 70
hard, 1112
soft, 1112
Palatine aponeurosis, 1139
artery, ascending, 555
of ascending pharyngeal, 557
descending, 562
bone, 166
articulations of, 169
horizontal part of, 167
orbital process of, 168
ossification of, 169
pyramidal process or tuber-
osity of, 168
sphenoidal process of, 169
vertical part of, 167
foramen, 180
nerves, 893
process of maxilla, 162
processes of fetus, 70
tonsils, 1137
uvula, 1112
velum, 1112
Palatoglossus muscle, 1129, note.
1139
Palatopharyngeus muscle, 1139
Palatum, 1112
durum, 1112
molle, 1112
Palmar aponeurosis, 460
arch, deep, 595
superficial, 598
cutaneous branch of median
nerve, 938
Palmar cutaneous branch of
ulnar nerve, 942
fascia, 460
interossei muscles, 465
interosseous arteries, 596
ligaments, 328, 331
nerves of ulnar, 942, 943
Palmaris brevis muscle, 463
actions of, 464
nerves of, 464
variations of, 464
longus muscle, 446
actions of, 450
nerves of, 450
variations of, 446
Palpehnc, 1025 _
Palpebral arteries, 569, 570
commissures or canthi, 1025
fissure, 1025
ligament, 1026
medial, 381
nerves from maxillary, 891
raphe, lateral, 381
Pampiniform plexus of sper-
matic cord, 678
Pancreas, 1199
accessory duct of, 1202, 1203
body of, 1201
development of, 1203
duct of, 1022, 1203
head of, 1200
lymphatic vessels of, 711
neck of, 1201
nerves of, 1204
structure of, 1203
surface marking of, 1320
tail of, 1201
uncinate process of, 1200
vessels of, 1204
Pancreatic arteries, 606
duct, 1202
accessory, 1202, 1203
veins, 681
Pancreatica magna artery, 606
Pancreaticoduodenal arteries, 604,
607
lymph glands, 710
veins, 682
Pancreaticolienal lymph glands,
706
Papilla, lacrimal, 1025
foliata, 1132
mammoe, 1267
Papillae, circumvallate, 1126
conical, 1127
filiform, 1127
fungiform, 1126
of skin, 1065
of tongue, 1126
Papillary layer of skin, 1065
process, 1191
Paracentral lobule, 822
Parachordal cartilages, 84
Paradidymis, 1246
Paraganglia, 12G9, 1278
Parallel striae of Retzius, 1120
Paramastoid process, 131
Paramedial sulcus, 822
Parametrium, 1259
Paranephric body, 1220
Paranucleus, 1204
Paraplasm, 36
Paraplexus, 840
Pararectal fossa, 1154
lymph glands, 710
Parathyroid glands, 1271
development of, 1272
structure of, 1273
Paravesical fossa, 1154
Paraxial mesoderm, 50
Parietal bone, 133
articulations of, 135
ossification of, 233
cells of fundus glands, 1167
convolution, ascending, 823
1382
INDEX
Parietal eminence, 133, 178, 183
foramen, 134, 178
lobe, 822
gyri of, 823
notch, 141
operculum, 825
pleura, 1087
veins, 520
Parietomastoid suture, 183
Parietooccipital fissure, 820
Parietotemporal artery, 573
Parolfactory area of Broca, 827
Paroophoron, 1206, 1255
Parotid duct, 1134
gland, 1132
accessory part of, 1134
nerves of, 1134
structure of, 1134
surface marking of, 1295
vessels of, 1134
lymph glands, 693
plexus, 902
Parotideomasseteric fascia, 385
Parovarium, 1255
Partes genitales externce mulie-
bres, 1264
Parumbilical veins, 682
Patella, 255
articulation of, 256
movements of, 346
ossification of, 256
structure of, 256
surface anatomy of, 1337
Patellar plexus, 953, 956
retinacula, 340
surface of femur, 248
Pathways from brain to spinal
cord, 870
Pectinate ligament of iris, 1009
Pectineal line, 246
Pectineus muscle, 472
actions of, 474
nerves of, 474
variations of, 474
Pectiniforme septum, 1248
Pectoralis major muscle, 436
actions of, 439
nerves of, 439
variations of, 438
minimus nniscle, 438
minor muscle, 438
actions of, 439
nerves of, 439
variations of, 438
Peculiar thoracic vertebrae, 104
Pedicles of a vertebra, 96
Peduncle of corpus callosum, 827
of olive, 781
Peduncles of cerebellum, 792
cerebral, 800
Pedunculus cerebri, 800
Pelvic colon, 1182
diaphragm, 420
fascia of, 420
fascia, 420
endopelvic part of, 422
girdle, 200
plexuses, 987
portion of sympathetic system,
984
Pelvi's, 238, 1149
articulations of, 306
axes of, 240
boundaries of, 238
brim of, 238
cavity of lesser, 239
diameters, 239, 240
in fetus, 242
greater or false, 238
inferior aperture or outlet of,
240
lesser or true, 239
ligaments of, 307, 308
linea terminalis of, 238
lymph glands of, 703
Pelvis, major, 238
male and female, differences
between, 241
mechanism of, 311
minor, 239
position of, 241
renal, 1221
superior aperture or inlet of,
239
surface anatomy of, 1336
Penis, 1247
body of, 1249
corona glandis, 1249
corpora cavernosa, 1248
corpus cavernosum urethrce, or
corpus spongiosum, 1248
crura of, 1248
deep artery of, 620
dorsal artery of, 620
veins of, 676
extremity of, 1250
fundiform ligament of, 1249
glands, 1248
nerves of, 1250
prepuce or foreskin of, 1250
root of, 1249
septum pectiniforme, 1248
structure of, 1250
suspensory ligament of, 1249
Perforated substance, 800, 827
Perforating arteries, of hand, 595
from internal mammary, 584
from plantar, 640
from profunda femoris, 631
cutaneous nerve, 967
fibers of Sharpey, 90
Perforator of spermatozoon, 42
Pericardiacophrenic artery, 584
Pericardial area, 46
lymphatic capillaries in, 684
arteries, 584, 600
pleura, 1089
Pericardium, 524
fibrous, 526, 526
nerves of, 526
oblique sinus of, 526
relations of, 525
serous, 525
structure of, 525
transverse sinus of, 526
vessels of, 526
vestigial fold of, 526
Pericecal folds, 1160
fossae, 1160
Perichondrium, 279
Perilymph, 1051
Perimysium, 373
Perineal artery, 619
body, 1185
branch of fourth sacral nerve,
968
muscle, superficial transverse,
427, 430
nerve, 968
Perineum, boundaries of, 424
central tendinous point of, 427
lymphatic vessels of, 706
muscles of, 424
Perineurium, 728
Periosteum, 87
of bone, lymphatic capillaries
_ in, 684
Peripheral end-organs, 1059
nervous system, 728
organs of special senses, 991
terminations of nerves of
general sensations, 1059
Periscleral lymph space, 1024
Peritoneal cavity, 1150
lymphatic capillaries in, 084
fossse or recesses, 1158
sacs, 1150, 1152, 1155
Peritoneum, 1149
epiploic foramen of, 1156
lesser sac of, 1155
Peritoneum, ligaments of, 1156
main cavity or greater sac of,
1150
horizontal disposition of,
1153, 1154, 1155
vertical disposition of, 1150
mesenteries, 1157
omenta, 1156
omental bursa of, 1155
vertical disposition of, 1 152
parietal portion of, 1150
visceral portion of, 1150
Permanent cartilage, 279
choanse, 70
kidney, 1211
teeth, 1115
development of, 1124
Peronsei muscles, actions of, 488
nerves of, 487
variations of, 487
Peronseus accessorius muscle, 487
• brevis muscle, 487
longus muscle, 486
quartus muscle, 487
quinti digiti muscle, 487
tertius muscle, 482
actions of, 482
nerves of, 482
Peroneal arteries, 638
nerves, 964, 965
retinacula, 489
septa, 480
Peroneocalcaneus externus mus-
cle, 487
internus muscle, 485
Peroneocuboidevis muscle, 487
Peroneotibialis muscle, 485
Perpendicular fasciculus, 844
tine of ulna, 218
plate of ethmoid, 154
Pes or base of cerebral peduncle,
802
hippocampi, 833
Petit, canal of, 1019
triangle of, 434
Petrooccipital fissure, 181
Petrosal nerve, deep, 892
external, 979
large deep, 892
superficial, 892, 903
superficial, greater, 892, 903
smaller, 1047
process, 147
sinuses, 648, 659
Petrosphenoidal fissure, 181
Petrosquamous sinus, 658
suture, 142, 145
Petrotympanic fissure, 140, 180
Petrous ganglion, 908
portion of temporal bone, 142
Peyer's glands, 1176
patches, 1176
Phalangeal processes of Corti's
rods, 1058
Phalanges digitorum manus, 230
pedis, 275
of foot, 275
articulations of, 359
ossification of, 275
of hand, 230
articulations of, 333
ossification of, 231
ungual, 275
Pharyngeal aponeurosis, 1143
artery, ascending, 557
bursa, 1142
grooves, 65
membrane, 1101
nerve from glossopharyngeal,
909
from sphenopalatine gan-
glion, 893
from vagus, 911
ostium of auditory tube, 1141
plexus of nerves, 909, 912, 979
INDEX
1383
Pharyngeal pouches, 65
recess, 1142
tonsil, 1142
tubercle, 132, 180
veins, 649
Pharyugopalatine arch, 1137
Pharyngopalatiuus muscle, 1139
Pharynx, 1141
aponeurosis of , 1143
development of, 1103
laryngeal part of, 1142
lymphatic vessels of, 698
mucous coat of, 1144
muscles of, 1142
actions of, 1 143
nerves of, 1143
nasal part of, 1141
oral part of, 1142
structure of, 1143
Philtrum, 385
Phrenic arteries, 601, 612
nerve, 928
plexus of nerves, 985
veins, 666, 679
Phrenicocolic ligament, 1158
Phrenicocostai sinus, 1089
Phrenicolienal ligament, 1155
Phrenicopericardiac ligament, 678
Phylogeny, 35
Pia of brain, 879
of cord, 879
mater, cranial, 879
encephali, 879
spinal, 879
spinalis, 879
Pigment of iris, 1013
of skin, 1064
Pigmented layer of retina, 1015
Pili, 1067
Pillars of Corti, 1056
of external abdominal ring, 410
of fauces, 1112
of fornix, 838, 840
Pineal body, 812, 1277
structure of, 1277
recess, 743, 816
Pinna, 1033
cartilage of, 1034
ligaments of, 1035
Piriformis muscle, 476
actions of, 478
fascia of, 421
nerves of, 478
variations of, 476
Pisiannularis muscle, 464
Pisiform bone, 225
Pisimetacarpus muscle, 464
Pisiuncinatus muscle, 464
Pisohamate ligament,'329
Pisometacarpal ligament, 329
Pits, olfactory, 68
Pituitary body, 814, 1257
Pivot-joint, 285
Placenta, 62
circulation through, 63, 540
cotyledons of, 63
fetal portion of, 62
maternal portion of, 62
previa, 64
separation of, 64
Plane, intertubercular, 1147
subcostal, 1148
transpyloric, 1147
Plantar aponeurosis, 490
arch, 639
arteries, 639
cutaneous venous arch, 669
digital veins, 671
fascia, 490
interossei muscles, 495
ligament, long, 354
metatarsal arteries, 640
nerves, 963
Plantaris muscle, 483
actions of, 483
Plantaris muscle, nerves of, 483
Planum nuchale, 120
occipitale, 130
Plasma cells, 377
Plate or Plates, cribriform, of eth-
moid, 153
ethmoidal, 85
orbital, of frontal, 137
perpendicular, of ethmoid, 154
pterygoid, of sphenoid, 151
tarsal, 1025
Platelets of blood, 505
Platysma muscle, 388
action of, 388
nerves of, 388
Pleura, 1087
cavity of, 1088
cervical, 10X8
costal, 1088
cupula of, 1088
diaphragmatic, 1088
lymphatic vessels of, 719
mediastinal, 1088
nerves of, 1090
parietal, 1087
pericardial, 1088
pulmonary, 1087
reflections of, 1088
structure of, 1090
surface markings of, 1309
vessels of, 1090
Pleural ca\-itj-, lymphatic capil-
laries in, 684
Plexiform layers of retina, 1016
Plexus of nerves, annular, 1009
aortic abdominal, 9S7
Auerbach's, 1177
brachial, 930
cardiac, 984
cavernous, 978
celiac, 985
cervical, 925
posterior, 912, 922, 923
choroid, of fourth ventricle,
798
of lateral ventricle, 840
of third ventricle, 815
coccygeal, 968
of cornea, 1009
coronary, 985, 987
esophageal, 913
of Exner, 846
gastric, 987
hemorrhoidal, 987
hepatic, 986
hypogastric, 987
infraorbital, 891
internal carotid, 977
lienal, 986
lumbar, 948
lumbosacral, 948
Meissner's, 1177
mesenteric, 987
myenteric, 1177
ovarian, 987
parotid, 902
patellar, 953, 956
pelvic, 987
pharyngeal, 909, 912, 979
phrenic, 985
prostatic, 988
pudendal, 966
pulmonary, 910, 913
renal, 987
sacral, 957
solar, 985
spermatic, 987
splenic, 986
subsartorial, 956
suprarenal, 987
tonsillar, 909
tympanic, 1047
uterine, 989
vaginal, 989
vesical, 988
Plexus of veins, basilar, 660
hemorrhoidal, 676
pterygoid, 645
pudendal, 076
uterine, 676
vertebral, 668
vesical, 676
vesicoprostatic, 676
Plexus aorlicus abdominalis, 987
arleria' ovariccp, 987
brachialis, 930
cardiacus, 984
caroticus internus, 977
cavernosus, 978
cervicalis, 925
chorioideus venlriculi, 840, 841
caliacus, 985
coronarius, 985
gastricus superior, 987
hepaticus, 986
hypogaslricus, 987
lienalis, 986
lumhalis, 949
lumbosacralis, 948
mesentericus inferior, 987
phrenicus, 985
prostaticus, 988
pudendus, 966
renalis, 987
sacralis, 957
spermaticus, 987
suprarenalis, 987
venosi basilaris 660
hamorrhoidalis, 676
pterygoideus, 645
pudendalis, 676
vertebrales, 668
vesicalis, 676
Plica circulares {Kerkringi\, 1173
fimbriata [tongue], 1125
gubernatrix, 1211
lacrimalis of Hasner, 1029
semilunaris [conjunctiva], 1028
[tonsil], 1138
sublingualis, 1136
triangularis [tonsil], 1138 ♦
vascularis, 1211
vesicalis transversa, 1154
Plica: uretericcc, 1232
venfriculares [laryngis], 1079
vocales, 1080
Pneumogastric nerve, 910
Polar bodies or polocytes, 40
Poles of cerebral hemispheres,
818
of eyeball, 1001
of lens, 1019
Polymorphonuclear leucocytes,
504
Polyspermy, 45
Poinum Adami, 1073
Pons, 785
development of, 740
hepatis, 1191
structure of, 785
Varoli, 785
Ponticulus [auricula], 1034
Pontine arteries, 580
Poutospinal fasciculus, 872
Popliteal artery, 632
branches of, 633
peculiarities of, 633
surface marking of, 1346
fossa or space, 631
line of tibia, 258
lymph glands, 701
nerves, 960, 964
surface of femur, 246
vein, 672
Popliteus muscle, 484
actions of, 486
minor, 485
nerves of, 486
variations of, 485
Pore, gustatory, 991
1384
INDEX
Porta of liver, 1191
Portal vein, 681
development of, 681
Postanal gut, 1110
Postaxial borders of limbs, 71
Postcentral sulcus, 822
Postcornu, 831
Posterior annular ligament, 458
basis bundle, 764
calcaneoastragaloid ligament,
352
circumflex artery, 589
common ligament, 288
cornu of medulla spinalis, 753
costotransverse ligament, 302
cricoarytenoid muscle, 1082
deep cervical vein, 651
dental artery, 562
ground bundle, 764
inferior ligament, 348
interosseous artery, 596
nerve, 944
ligament, 327
pillar of fauces, 1137
proper fasciculus, 764
pulmonary nerves, 913
radial carpal artery, 594
radioulnar ligament, 325
sacrosciatic ligament, 309
scapular artery, 582
nerve, 932
superior ligament, 348
talotibial ligament, 350
temporal artery, 559
ulnar carpal artery, 598
vertebral vein, 651 «
Postero-lateral ganglionic arteries,
581
Postero-medial ganglionic arte-
ries, 547, 581
Postgemina, 806
Postnodular fissure, 790
Postpartum hemorrhage, 64
Postpyramidal fissure, 790
Postsphenoid part of sphenoid,
♦ 152
Pouch of Douglas, 1152
of Prussak, 1046
of Rathke, 1277
Pouches, pharyngeal, 65
Poupart's ligament, 411
Prccpulium clitoridis, 1266
Preauricular Ivmph glands, 693
point, 1291
sulcus of ilium, 234
Preaxial borders of limbs, 71
Precentral gyre, 821
sulcus, 821
Prechordal portion of base of
fetal skull, 84
Precommissure, 840
Precornu, 830
Precuneus, 823
Pregemina, 806
Premaxilla, 126
Premolar teeth, 1118
Preoccipital notch, 818
Prepatellar bursa, 471
Prepuce of clitoris, 1266
of penis, 1250
development of. 1215
Preputial glands, 1250
sac, 1250
Prepyramidal fissure, 790
tract, 761
Presphenoid, 152
Pressure epiphyses, 95
Presternal notch, 120
Pretracheal fascia, 390
Prevertebral fascia, 389
part of base of skull, 84
Primary arcolje of bone, 93
oocytes, 38
spermatocytes, 43
Primitive aortaj, 506
Primitive atrium, 508, 512
costal arches, 82
digestive tube, 53
fibrUhe of Schultze, 725
groove, 47
jugular veins, 520
ova, 1209
palate, 70
segments, 52
sheath of nerve fiber, 727
streak, 47
urogenital ostium, 1215
ventricle of heart, 508
Princeps corvicis artery, 557
pollicis artery, 595
Prismata adamantina, 1120
Proamnion, 47
Procerus muscle, 382
action of, 382
nerves of, 382
Process or Processes, alveolar, 161
articular, of vertebris, 96
ciliary, 1010
clinoid, 147, 151, 190
condyloid, of mandible, 174
coracoid, 207
coronoid, of mandible, 174
of ulna, 214
costal, 98
descending, of lacrimal, 104
of dura mater, 873
frontal, of maxilla, 161
frontonasal, 67
frontosphenoidal, of zvgomatic,
164
globular, of His, 68
of inferior nasal concha, 169
intrajugular, 131
jugular, 131, 181
lateral nasal, 68
lenticular, of incus, 1045
malar, of maxilla, 161
mastoid, 141
maxillary, of fetus, 69
of inferior nasal concha, 169
of palatine bone, 168
of zygomatic bone. 166
muscular, of arytenoid, 1075
nasal, of frontal bone, 136
of maxUla, 161
odontoid, of axis or epistro-
pheus, 100
orbital, of palatine bone, 168
of zygomatic bone, 165
palatal, of maxilla, 162
palatine, of fetus, 70
of maxilla, 162
papillary, of liver, 1191
paramastoid, 131
petrosal, 147
phalangeal, of Corli'srods, 1057
pterygoid, of sphenoidal bone,
151
pyramidal, of palatine bone,
168,180
sphenoidal, of palatine bone,
169
of septal cartilage of nose,
993
turl)inated, 152
spinous, of ilium. 234
of vertebrae, 96
styloid, of fibula, 260
of radius, 220
of temporal bone, 145, 181
of ulna, 218
temporal, of zygomatic, 166
transverse, of vertebrce, 96
trochlear, of calcaneus, 266
uncinate, of ethmoid, 155
vaginal, of sphenoid, 151
of temporal, 144, 145
vermiform, 1178
of vertebrae, 106
vocal, of arytenoid, 1075
Process or Processes, xiphoid, 121
zygomatic, of frontal, 130
of maxilla, 161
of temporal bone, 139
Processus alveolaris [maxillcv], 161
brevis [malleus], 1044
ciliares, 1010
cochleariformis, 145, 1042
condyloideus [mandihuhv], 174
coracoideus [scapulce], 207
coronoidcus [mandibula], 174
[ulnar e], 214
frontalis [maxilla-], 161
gracilis [malleus], 1044
orhitalis [as palafinum], 168
palatinus [ynaxilla-], 162
pterygoidei, 151
pyramidalis [os palatinum], 168
spinosus, 97
splenoidalis [os palatinum], 109
transversi, 97
tubarius, 152
vermiformis, 1178
xiphoideus, 121
zygomaticus, 161
Proctodeum, 1110
Prodentin, 1123
Profunda arteries, 591
brachii artery, 591
cervicalis artery, 585
femoris artery, 629
vein, 672
lingute artery, 553
Projection fibers of cerebral hemi-
sheres, 842
Prominence of aqueduct of Fal-
lopius, 1042
of facial canal, 1042
laryngeal, 1073
Prominentia canalis facialis, 1042
Promontorium, 1042
Promontory of tympanic cavity,
1042
Pronator quadratus muscle, 449
actions of, 450
nerves of, 450
variations of, 450
teres muscle, 446
actions of, 450
nerves of, 450
variations of. 446
Pronephric duct, 1205
Pronephros, 1205
Pronucleus, female, 42
male, 45
Prootic center of temporal bone,
146
Prophase of karyokinesis, 37
Prosencephalon, 51, 807
Prostata, 1251
Prostate, 1251
development of, 1213
gland, 1251
lobes of. 1252
lymphatic capillaries of, 687
vessels of, 713
nerves of, 1253
structure of, 1253
vessels of, 1253
Prostatic ducts, orifices of, 1234
plexus of nerves, 988
portion of urethra, 1234
sinus, 1234
utricle, 1234
Prosthion, 198
Prothrombin, 505
Protoplasm, 35
Protoplasmic process of nerve
cells, 723
Protuberance, mental, 172
occipital, 129, 130, 183
Prussak, pouch of, 1046
Psalterium, 838
Pseudocele, 840
Pseudonucleoli, 37
INDEX
1385
Pseudopodium, 505
Psoas inagnus muscle, 467
major muscle, 467
actions of, 467
fascia covering, 466
nerves of, 467
minor muscle, 467
actions of, 467
nerves of, 467
parvus muscle, 467
Pterion, 151, 182, 198
ossicle, 156
Pterotic center of temporal bone,
146
Pterygoid canal, 151, 180
fissure, 151
fossa of sphenoid, 151
hamulus, 151, 180
muscles, 386
plates, 151
plexus of veins, 645
processes of sphenoid, 151
tubercle, 152
Pterygoideus externus muscle,
386
action of, 387
nerves of, 387
internus muscle, 387
action of, 387
nerves of, 387
Pterygomandibular ligament, 384
raphe, 384
Pterygomaxillary fissure, 185
Pterygopalatine canal, 159, 168
fossa, 185
groove, 151
nerve, 893
Pterygospinous ligament, 153,388
Pubic arch, 240
bones, articulation of, 309
ligaments, 310
region, 1149
tubercle or spine, 236
vein, 673
Pubis, 236
angle of, 236
body of, 236
crest of, 236
iliopectineal eminence of, 236
obturator crest of, 236
rami of, 236
symphysis of, 310
tubercle or spine of, 236
Pubocapsular ligament, 334
Pubococcygeus muscle, 424
Pubofemoral ligament, 335
Puborectalis muscle, 424
Pubovesicales muscles, 1231
Pudendal artery, accessory, 618
internal, in female, 620
in male, 617
cleft or rima, 1256
nerve, 967
inferior, 980
plexus, nervous, 966
venous, 676
veins, internal, 673
Pudendum, 1264
Pudic arteries, 617, 629
nerve, internal, 967
veins, internal, 674
Pulmonary artery, 543
opening of, in right ventricle,
531
ligaments, 1088, 1090
nerves, 913
pleura, 1087
semilunar valves, 532
veins, 642
openings of, in left atrium
533
Pulmones, 1093
fades costalis, 1094
mediastinalis, 1095
margo anterior, 1096
Pulmones margo inferior, 1096
posterior, 1096
Pulp cavity of teeth, 1118
dental, 1118
of spleen, 1284
Pulvinar, 808
Puncta lacrimalia, 1028
vasculosa, 827
Pupil, 1012
congenital atresia of, 1003
Pupillary membrane, 1003, 1014
Purkinje, cells of, 794
fibers of, 536
Putamen, 834
Pyloric antrum, 1162, 1103
artery, 604
glands, 1166
orifice of stomach, 1162
part of stomach, 1162, 1163
valve, 1164
vein, 682
Pyramid, 1042
of cerebellum, 791
of medulla oblongata, 768
of temporal fjone, 142
of vestibule, 1048
Pyramidal cells of cerebral cortex,
845
decussation, 768
eminence of tympanic cavity,
1042
lobe of thyroid gland, 1270
process of palatine bone, 168,
180
tracts, 759, 760
Pyramidalis muscle, 416
variations of, 417
nasi muscle, 382
Pyramids, renal, 1221
Pyramis medullce oblongata!, 768
Q
Quadrate lobe of liver, 1 192
Quadratus femoris muscle, 477
actions of, 478
nerves of, 478
labii inferioris muscle, 383
action of, 383
nerves of, 383
superioris muscle, 383
action of, 383
nerves of, 383
lumborum muscle, 420
actions of, 420
fascia covering, 419
nerves of, 420
variations of, 420
menti muscle, 383
plantee muscle, 493
actions of, 496
nerves of, 496
variations of, 496
Quadriceps extensor muscle, 470
femoris muscle, 470
actions of, 471
nerves of, 471
Quadrigeminal bodies, 805
Radial artery, 592
branches of, 594
carpal, 594
peculiarities of, 594
recurrent, 594
surface marking of, 1335
fibers of cerebral cortex, 846
fossa, 212
nerve, 943
sulcus, 211
tuberosity, 219
Radialis indicis artery, 595
Radiate ligament, 299
sternocostal ligaments, 302
Radiocarpal articulation, 327
movements of, 328
Radioulnar articulations, 324,325
ligaments, 325
union, middle, 325
Radius, 219
grooves on lower end of, 220
oblique lino of, 219
ossification of, 220
sigmoid cavity of, 220
structure of, 220
surface anatomy of, 1327
tuberosity of, 219
ulnar notch of, 220
Radix arcus vertebra;, 97
lingwv, 1125
penis, 1249
pili, 1067
pulmonis, 1097
Rami of ischium, 235
of pubis, 236
Ramus of mandible, 173
Ranine arterv, 553
vein, 648, 649
Ranvier, crosses of, 727
nodes of, 727
Raphe, anococcygeal, 426
lateral palpebral, 381
of palate, 1112
pterygomandibular, 384
of scrotum, 1237
Rathke, pouch of, 1277
Receptaculum chyli, 691
Recess, epitympanic, 142, 1038
nasopalatine, 990
omental, 1156
optic, 816
pharyngeal. 1141, 1142
pineal, 743, 816
sphenoethmoidal, 195, 994
Recesses, lateral, of fourth ven-
tricle, 797
peritoneal, 1158
of Troltsch, 1046
Recessus ellipticus, 1048
infundibuli, 816
inter sigmoideus, 1161
pinealis, 743, 816
sacciformis, 326
sphcericus, 1047
suprapinealis, 816
Reciprocal reception, articulation
by, 286
Rectal ampulla, 1183
columns of Morgagni, 1185
layer of pelvic fascia, 422
Recti muscles, actions of, 1023
nerves of, 1023
Rectococcygeal muscles, 1186
Rectouterine folds, 1260
Rectovesical excavation, 1152
folds, 1154
layer of pelvic fascia, 422
Rectovesicales muscles, 1231
Rectum, 1183
ampulla of, 1183
anal part of, 1184
development of, 1108
Houston's valves of, 1183
lymphatic vessels of, 711
relations of, 1184
Rectus abdominis muscle, 415
sheath of, 416
capitis anterior muscle, 395
action of, 396
nerves of, 395
anticus major muscle, 395
minor muscle, 395
lateralis muscle, 395
action of, 396
nerves of, 395
posterior major muscle, 401
action of, 402
1386
INDEX
Rectus capitis posterior major
muscle, nerves of, 4t»2
minor muscle, 401
action of, 4Q2
nerves of, 402
femoris muscle, 470
actions of, 471
nerves of, 471
muscles of eyeball, 1022
Recurrent artery, interosseous,
597
radial, 594
tibial, 635
ulnar, 596
branches from deep volar arch,
595
laryngeal nerve, 912
nerve, 912
Red corpuscles, 503
nucleus, 802
Reflected inguinal ligament, 412
Reflections of pleuraj, 1088
Reflex paths, spinal intrinsic, 850
Refracting media of eye, 1018
Regions of abdomen, 1147
Reil, island of, 825
Reissner, vestibular membrane
of, 1054
Renal arteries, 610
columns, 1221
fascia, 1220
impression, 1189
pelvis, 1221, 1225
plexus, 987
pyramids, 1221
sinus, 1221
tubules, 1221
veins, 679
vessels, afferent and efferent,
1221, 1224
Renes, 1215
Reproduction of cells, 37
Respiration, mechanism of, 407
Respiratory apparatus, 1071
development of, 1071
nerve of Bell, 928, 933
system, 1071
Restiform bodies of medulla, 973
Rete canalis hypoglossi, 660
foraminis ovalis, 660
testis, 1244
Retia venosa vertebrarum, 668
Reticular lamina, 1058
layer of skin, 1065
Reticularis alba, 784
grisea, 784
Retina, 1014
central artery of, 571
development of, 1002
fovea centralis, 1015
layers of, 1015
macula lutea, 1015
membrana limitans 1017
ora serrata, 1014
structure of, 1015
supporting frame-work of, 1017
Retinacula of hip-joint, 334
patellar. 340
peroneal, 489
Retrahens aurem muscle, 1035
Retroeecal fossa, 1101
Retroglandular sulcus of penis,
1249
Retroperitoneal fossjE, 1158
Retropharyngeal Ivmph glands,
694
space, 390
Retropubic pad, 1228
Retrovesical excavation, 1152
Retzius, colored lines of, 1120
Rhinal fissure, external, 744
Rhinencephalon, 744, 826
Rhombencephalon, 51, 738, 767
Rhombic grooves, 740
lip, 739
Rhomboid fossa, 798
impression, 202
ligament, .314
Rhomboidei muscles, actionsof,435
nerves of, 435
variations of, 435
Rhomboideus major muscle, 434
minor muscle, 434
occipitalis muscle, 435
Rhomboids, nerve to, 932
Ribs, 123
common characteristics of, 123
development of, 82
false, 123
floating or vertebral, 123
ossification of, 127
peculiar, 125
structure of, 125
true, 123
vertebrochondral, 123
vertebrosternal, 123
Ridge, ganglion, 51, 736
supracondylar, 211
trapezoid or oblique, 200
Ridges, bicipital, 209
Right atrium, 529
auricle, 529
auricular appendix, 529
coronary plexus, 985
veins, 642
gastroepiploic glands, 706
ventricle, 531
Rima gloitidis, 1080
of mouth, 1110
palpebrarum, 1025
pudendal, 1265
Ring, femoral, 625
subcutaneous, 410
tympanic, 146
Rings, abdominal, 410, 418
fibrous, of heart, 536
Risorius muscle, 385
action of, 385
nerves of, 385
Rivinus, ducts of, 1136
notch of, 1038
Rod-bipolars of retina, 1017
Rod-granules of retina, 1017
Rods and cones, layer of, 1017
of Corti, 1056
of retina, 1017
Rolando, fissure of, 819
substantia gelatinosa of, 753
tubercle of, 775
Roller, nucleus of, 784
Roof plate of medulla spinalis,
133
Root of lung, 1097
of penis, 1249
Root-sheaths of hair, 1068
Roots of spinal nerves, 764, 916
of teeth, 1114
of zygomatic process, 139
Rosenmiiller, fossa of, 1141, 1142
I lymph gland of, 703
organ of, 1206, 1255
Rostrum of corpus callosum, 828
sphenoidal, 149
Rotary joint, 285
Rotation, movement of, 286
Rotatores muscles, 400
action of, 402
nerves of, 402
spinse muscle, 400
Round ligament of liver, 1192
of uterus, 1261
Rubrospinal fasciculus, 870
Ruffini, corpuscles of, 1061
Rust-colored layer of cerebellar
cortex, 795
S
Sac, dental, 1123
lacrimal, 1028
Sac, preputial, 1250
Sacs of peritoneum, 1150, 1152
Saccule, laryngeal, 1080
of vestibule, 1051, 1052
Sacculus, 1052
Saccus lacrimalis, 1028
vaginalis, 1211
Sacral arteries, lateral, 621
artery, middle, 613
canal, 110
cornua, 108
crests, 107, 108
foramina, 106, 108
groove, 107
hiatus, 107
lymph glands, 704
nerves, divisions of, 924, 957
nucleus of medulla spinalis, 758
plexus, 957
sympathetics, 973
tuberosity, 108
veins, 673, 677
Sacrococcygeal ligaments, 309
Sacrogenital folds, 1154, 1260
Sacroiliac articulation, 306
ligaments, 307, 308
Sacrosciatic ligaments, 309
Sacrospinalis muscle, 397
Sacrovertebral angle, 106
Sacrum, 106
alaof, 110
apex of, 110
articulations of, 111
auricular surface of, 108
base of, 109
ossification of, 113
structure of. 111
variations of. 111
Saddle-joint, 286
Sagittal fossa of liver, 1191
sinuses, 654, 655
sulcus, 131, 134, 136
suture, 134, 178
Salivary glands, 1132
development of, 1102
parotid, 1132
structure of, 1136
sublingual, 1136
submaxillary, 1135
Salpingopalatine fold, 1142
Salpingopharyngeal fold, 1142
Salpingopharyngeus muscle, 1143
Salter, incremental lines of, 1120
Santorini, cartilages of, 1075
duct of, 1202
Saphenous nerves, 956, 963
opening, 469
veins, 669, 670
Sarcolemma, 373
Sarcomere, 375
Sarcoplasm, 374
Sarcostyles, 374
Sarcous elements of muscles, 375
Sartorius muscle, 470
Scala media [cochlea], 1054
tympani, 3051
vestibuli, 1051
Scalene tubercle, 125
Scaleni muscles, actions of, 396
nerves of, 396
variations of, 396
Scalenus anterior muscle, 396
anticus muscle, 396
medius muscle, 396
pleuralis muscle, 396
posterior muscle, 396
posticus muscle, 396
Scalp, lymphatic vessels of, 694
skin of, 378
Scapha, 1034
Scaphoid bone, 221, 270
fossa of sphenoid, 151, 180
Scapula, 202
acromion of, 203
coracoid process of, 207
INDEX
1387
Scapuln, glenoid cavity of, 207
ligaments of, 316
ossification of, 208
spine of, 203
structure of, 207
surface anatomy of, 1326
Scapular arteries, 582
circumflex artery, 588
nerve, posterior, 932
notch, 204
Scapuloclavicular articulation,
315
Scapus or shaft of hair, 1069
pili, 1069
Scarpa, fascia of, 408
foramina of, 162, 180
ganglion of, 1058
triangle of, 626
Schindylesis, 284
Schlemm, canal of, 1005
Schreger, lines of, 1120
Schultze, primitive fibrillae of, 725
Schwann, white matter of, 726
Sciatic artery, 62(i
foramen, 309
nerves, 959, 960
notch, 235
veins, 674
Sclera, 1005
structure of, 1006
Scleral spur, 1007
Sclerocorneal junction, 1005
Sclerotogcnous layer, 80
Sclerotome, SO
Scrotal arteries, posterior, 619
nerves, posterior, 968
Scrotum, 1237
dartos tunic of, 1238
integument of, 1237
nerves of, 1239
raphe of, 1237
vessels of, 1239
Sebaceous glands, 1069
Second cuneiform bone, 271
metacarpal bone, 228
metatarsal bone, 271
nerve, 882
Secondary areolae of bone, 94
dentin, 1120
oocytes, 41
sensory fasciculus, 762
spermatocytes, 43
tympanic membrane, 1040
Secretion, internal, 1269
Segment, internodal, 727
of Lantermann, 727
medullary, 727
Segmentation of cells, 37
of fertilized ovum, 45
nucleus, 45
Segments, primitive, 52
spinal, 750
Sella turcica, 147, 190 .
Semicanalis m. tensoris iymvani,
145, 1042
tuhfr audilivcr, 145, 1042
Semicircular canals, 1047, 1052
ducts, 1052
Semilunar bone, 224
fibrocartilages of knee, 342, 343
ganglion of abdomen, 985
of trigeminal nerve, 886
lobules of cerebellum, 790
Semimembranosus muscle, 479
actions of, 4S0
nerves of, 480
variations of, 479
Seminal duct, 1245
vesicles, 1246
Semispinalis capitis muscle, 400
cervicis muscle, 400
colli muscle, 400
dorsi muscle, 400
muscles, actions of, 402
nerves of, 402
Semitendinosus muscle, 479
actions of, 480
nerves of, 480
Sensations, peripheral termina-
tions of nerves of, 1059
Senses, organs of, 991
special, peripheral organs of,
991
Sensory areas of cerebral cortex,
849
decussation, 777
pathways from spinal cord to
brain, 851
Septum, aortic, 514
canalis musculoluharii, 145,
1042
crural, 626
femoralc, 626
inferius of heart, 512
intermedium, 512
interventricular, 534
lucidum, 840
mobile nasi, 993
nasi, 194
of nose, 194, 995
orbital, 1026
pectiniforme penis, 1248
pellucidum, 840
primum, 512
secundum, 512
spurium, 510
subarachnoid, 877
of tongue, 1132
transvcrsum, 72
of semicircular ducts, 1052
urorectal, 1109
ventricular, 512, 535
ventriculorum, 535
Serosa, or false amnion, 56
Serous glands of tongue, 1131
pericardium, 526
Serratus anterior muscle, 438
actions of, 439
ner\-es of, 439
variations of, 439
magnus muscle, 438
posterior inferior muscle, 404
variations of, 404
superior muscle, 404
variations of, 404
' posticus muscles, 404
Sertoli, cells of, 1243
Sesamoid bones, 277
cartilages, 993
Seventh nerve, 901
Shaft of hair, 1069
Sheath or Sheaths of arteries, 499
carotid, 389
crural, 625
dentinal, of Neumann, 1119
femoral, 625
of flexor tendons of fingers, 449
of toes, 492
mucous, 283
of tendons around ankle, 489
on back of wrist, 459
in front of wrist, 457
of rectus abdominis muscle, 416
Shin bone, 256
Short bones, 79
calcaneocuboid ligament, 354
gastric veins, 681
plantar ligament, 354
saphenous nerve, 963
vein, 670
Shoulder blade, 202
girdle, 200
muscles of, 439
development of, 371
Shoulder-joint, 317
bursse near, 319
movements of, 319
vessels and nerves of, 319
Sibson's fascia, 1089
Sight, organ of, 1000
Sigmoid arteries, 010
cavity of radius, 220
of ulna, 215
colon, 1182
flexure, 1182
mesocolon, 1153
sinus, 657
sulcus, 142
Sinus or Sinuses, aortic, 534
' basilar, 660
cavernous, 658
cervicalis, 67
circular, 659
confluence of, 658
coronary, 642
costomediastinal, 1090
cranial, 135 note
of dura mater, 654
of epididymis, 1242
of external jugular vein, 647
frontal, 138, 998
intercavernous, 659
laryngeal, 1080
lateral, 657
longitudinal, 654, 655
maxillary, 159, 999 ,
of Morgagni, 1143
of nose, 998
occipital, 658
of pericardium, 526
petrosal, 659
petrosquamous, 658
phrenicocostal, 1089
pocularis, 1234
prostatic, 1234
pyriformis, 1142
renal, 1221
rhomboidalis, 51
sagittal, 654, 655
septum, 511
sigmoid, 657
sphenoidal, 149, 998
sphenoparietal, 658
straight, 655
tentorial, 655
tonsillaris, 67
transverse, 657, 660
urogenital, 1213
of Valsalva, 533, 534
venarum, 528
venosus, 508
Sinus or Sinuses, cavernosus, 658
coronarius, 642
durir matris, 654
frontales, 998
intercavernosi] 659
maxillaris, 159, 999
occipitalis, 658
paranasalcs, 998
petrosus, 648, 659
rectus, 655
sagittalis, 654. 655
sphenoidales, 998
tarsi, 267
transversus, 657
venosus, 529
sclera;, 1005
Sinusoids of Minot, 501
Sixth nerve, 899
Skein, or spirem, 37
Skeleton, 79
development of, 80
Skene's duct, 1213
Skin, 1062
appendages of, 1066
hairs, 1067
nails, 1066
sebaceous glands, 1069
sudoriferous or sweat glands,
1070
arteries of, 1066
corium or cutis vera, 1065
development of, 1066
epidermis or cuticle, 1062
furrows of, 1062
1388
INDEX
Skin, lymphatic capillaries in, GiS4
nerves of, 10G6
papillary layer of, 1065
reticular layer of, 10G5
stratum corneum, 1062
mucosuin, 1062
true 1065
Skull, 128
development of, 83
differences in, due to age, 196
exterior of, 178
fossa of, 190, 192
interior of, 189
norma basalts, 178, 179
frontalis, 185
lateralis, 182
occipitalis, 185
verticalis, 178
sexual differences in, 197
surface anatomy of, 1278
tables of, 195
upper surface of base of, 190
Skull-cap, inner surface of, 189
Slightly movable joints, 285
Small cardiac vein, 642
cavernous nerves, 989
intestine, 1168
areolar or submucous coat
of, 1172
circular folds of, 1173
duodenum, 1168
glands of, 1176
ileum, 1170
jejunum, 1170
lymphatic nodules of, 1176
vessels of, 710
Meckel's diverticulum of,
1172
mucous membrane of, 1173
muscular coat of, 1172
nerves of, 1176
Peyer's glands of, 1176
serous coat of, 1172
valvulie conniventes of, 1173
vessels of, 1176
villi of, 1174
saphenous vein, 670
sciatic nerve, 959
wings of sphenoid, 151
Smaller occipital nerve, 926
Smallest cardiac veins, 643
Smell, organ of, 992
Soft palate, 1112
aponeurosis of , 1139
arches or pillars of, 1112
muscles of, 1139
Solar plexus, 985
Sole of foot, muscles of, first
layer, 491
fourth layer, 495
second layer, 493
third layer, 493
Soleus muscle, 483
actions of, 483
nerves of, 483
variations of, 483
Solitary cells of medulla spinalis,
758
glands, 1176
Somatic cells, 35
fiber's of spinal nerves, 920
layer of mesoderm, 50
Somatopleure, 50
Space or Spaces, of angle of iris,
1009
of Burns, 389
corneal, 1008
interpleural, 1090
of Fontana, 1009
intercostal, 123
interglobular, 1120
of Nuel, 1058
popliteal, 631
retropharyngeal, 390
subarachnoid, 876
Space or Spaces, suprasternal, 389
Spatia zonularis, 1019
Spatium perichorioideale, 1005
Spermatic artery, internal, 611
canal, 418
cord, 1239
structure of, 1239
fascia, external, 411, 1238
plexus of nerves, 987
veins, 678
Spermatids, 43, 1243
Spermatoblasts, 1243
Spermatocytes, 43, 1243
Spermatogonia, 43, 1243
Spermatozoon 42, 1243
body or connecting piece of, 42
formation of, 1243
head of, 42
neck of, 42
perforator of, 42
tail of, 43
Sphenoethmoidal recess, 195, 994
suture, 190
Sphenofrontal suture, 182, 190
Sphenoid bone, 147
articulations of, 153
body of, 147
ossification of, 152
pterygoid processes of, 151
wings of, 149, 151
Sphenoidal air sinuses, 149, 998
concha^, 152
crest, 149
process of palatine bone, 169
of septal cartilage of nose,
993
rostrum, 149
spine, 150, 180
turbinated processes, 152
Sphenomandibular ligament, 297,
388
Sphenomaxillary fissure, 184
fossa, 185
Sphenopalatine artery, 562
foramen, 168
ganglion, 891
nerves, 890
notch, 169
Sphenoparietal sinus, 658
suture, 182
Sphenosquamosal suture, 182
Sphenozygomatic suture, 182
Sphincter ani externus muscle,
425
internus muscle, 426
pupilUe muscle, 1013
recti muscle, 424
urethrte membranaceae muscle,
429, 431
vaginae muscle, 430
Spigelian lobe of liver, 1192
Spina helicis, 1034
scapula", 203
vestibuli, 510
Spinal accessory nerve, 913
arteries, 579
bulb, 767
column, 96
cord, 749
dura of, 875
pathways from brain to, 870
pia of, 879
sensory pathways from, to
brain, 851
ganglia, 917
lenuiiscus, 762
nerves, 916
composition and central con-
nections of, 849
connections with sympa-
thetic, 920
development of , 119
divisions of, 921, 925
fibers of, 920
points of emergence of, 916
Spinal nerves, roots of, 764, 916
size and direction of, 917
structure of, 920
reflex paths, intrinsic, 850
segments, 750
Spinalis capitis muscle, 400
cervicis muscle, 400
colli muscle, 400
dorsi muscle, 399
Spindle, achromatic, 37
aortic, 547
neuromuscular, 1061
neurotendinous, 1001
Spine or Spines, ethmoidal, 147,
190
of frontal bone, 136
iliac, 234
ischial, 235
mental, 172
nasal, 158, 163, 167, 180, 187
pubic, 236
of scapula, 203
sphenoidal, 150, 180
suprameatal, 145, 183
of tibia, 256"
trochlear, 137
Spinoglenoid ligament, 317
Spinoolivary fasciculus, 854
Spinoquadrigeminal system of
Mott, 762
Spinotectal fasciculus, 762, 854
Spinothalamic fasciculus, 762
Spinous process of a vertebra, 96
Spiral canal of modiolus, 1051
ligament, 1054
line of femur, 245
organ of Corti, 1056
thread of spermatozoon, 43
tube of kidney, 1223
Spirem or skein, 37
Splanchnic fibers of spinal
nerves, 920
layer of mesoderm, 50
nerves, 981
Splanchnology, 1071
Splanchnopleure, 50
Spleen or lien, 1282
accessory, 1283
bloodvessels of, 1285
development of, 1282
lymphatic capillaries in, 686
nodulus of, 1285
vessels of, 711
Malpighian bodies of, 1285
relations of, 1282
size and weight of, 1283
structure of, 1283
supernumerary, 1283
surface marking of, 1320
Splenial center of ossification, 175
Splenic artery, 605
distribution of, 12S5
cells, 1284
glands, 706
flexure of colon, 1180
plexus, 986
pulp, 1284
vein, 681
Splenii muscles, actions of, 397
nerves of, 397
Splenium of corpus callosum, 828
Splenius capitis muscle, 397
cervicis muscle, 397
variations of, 397
colli muscle, 397
Spongioblasts, 733
Spongioplasm, 36
Spring ligament, 356
Spur of malleus, 1044
scleral, 1007
Squama, frontal, 135
occipital, 129
temporal, 139
Squamosal suture, 183
Stahr, middle gland of, 697
INDEX
1389
stalks, optic, 742, 1001
of thalamus, SI 1
Stapedius muscle, 1046
Stapes, 1045
annular ligament of, 104 5
development of, 1033
Stellate ligament, 299
veins of kidney, 1224
Stensen, duct of , 1134
foramina of, 126, 180
Stephanion, 183, 198
Sternal angle, 121
end of clavicle, 202
foramen, 121
furrow, 1307
glands, 715
plate, 83
Sternalis muscle, 437
Sternebra-, 120
Sternoclavicular articulation, 313
surface anatomy of, 1328
Sternoclaviouluris muscle, 438
Sternocleidomastoid artery, 552,
556
Sternocleidomastoideus muscle,
390
variations of, 390
Sternocostal ligaments, 302
surface of heart, 528
Sternohyoid muscle, 393
Sternohyoideus muscle, 393
variations of, 393
Sternomastoid artery, 552, 556
muscle, 390
Sternopericardiac ligaments, 526
Sternothyreoideus muscle, 393
variations of, 394
Sternothyroid muscle, 393
Sternum, 119
articulations of, 123
development of, 83
ossification of, 121
structure of, 121
Stomach, 1161
bed, 1162
body of, 1163
cardiac glands of, 1166
orifice of, 1161
component parts of, 1163
curvatures of, 1162
development of, 1103
fundus of, 1163
glands of, 1166
incisur a angular is, 1162
interior of, 1162
lymphatic vessels of, 710
mucous membrane of, 1166
muscular coat of, 1164
nerves of, 1167
openings of, 1161
position of, 1163
pyloric antrum, 1162, 1103
glands, 1166
orifice, 1162
valve, 1164
serous coat of, 1164
shape and position of, 1161
structure of, 1104
subdivisions of, 1163
sulcus inter medius, 1162
surface marking of, 1317
surfaces of, 1162
teeth, 1117
vessels of, 1167
Stomodeum, 1101
Stratiform fibrocartilage, 282
Stratum cinereum, 806
compactum [decidual, 59
corneum, 1062
dor sale, 812
germinativum, 1063
granulosum, 1063
intermedium [choroid], 1010
lemnisci, 806
lucidum, 1063
Stratum opticum [retina], 1015
[superior colliculus], 806
spongiosum [decidua], 60
zonale, 806
Streak, primitive, 47
Stria, longitudinal, 827
Striate arteries, 573
veins, inferior, 653
Striated muscle, lymphatic capil-
laries in, 684
Stripe of Hensen, 1058
Striped muscle, 373
Stroma of iris, 1013
of kidney, 1225
of ovary, 1256
Styloglossus muscle, 1130
Stylohyal part of styloid process,
145
Stylohyoid ligament, 392
muscle, 392
nerve, from facial, 905
Stylohyoideus muscle, 392
variations of, 392
Styloid process of fibula, 260
of radius, 220
of temporal bone, 145, 181
of ulna, 218
Stylomandibular ligament, 388
Stylomastoid artery, 557
foramen, 144, 181
Stylopharyngeus muscle, 1143
Subanconeus muscle, 445
Subarachnoid cavity, 876
cisternse, 876
septum, 877
space, 876
Subarcuate fossa, 143
Subcallosal gyrus, 827, 869
Subcardinal veins, 520
Subclavian arteries, 575
first part of left, 577
of right, 576
second portion of, 577
surface anatomy of, 1290
marking of, 1303
third portion of, 577
triangle, 394, 565
vein, 664
Subclavius muscle, 438
variations, 438
Subcostal arteries, 601
zone, 1148
Subcostales muscles, 403
Subcrureus or articularis genu
muscle, 471
Subcutaneous inguinal ring, 410
Subdural cavity, 875
Subepithelial plexus of cornea,
1009
Subfrontal gyre, 822
Subinguinal lymph glands, 702
Sublingual artery, 553
gland, 1136
Sublobular veins, 1196
Submaxillary artery, 555
duct, 1135
ganglion, 898
gland, 1135
lymph glands, 697
triangle, 392, 564
Submental artery, 555
lymph glands, 697
triangle, 392
Subnasal point, 198
Suboccipital muscles, 401
triangle, 402, 578
Subparietal sulcus, 823
Subperitoneal connective tissue,
418
Subpleural mediastinal plexus,
584
Subpubic ligament, 310
Subsartorial plexus, 956
Subscapular angle, 203
artery, 588
Subscapular fascia, 440
fossa, 202
nerves, 933
Subscapularis muscle, 440
Subserous areolar tissue, 1150
Substantia adamantina, 1120
alba, 758
cburnea, 1119
ferruginea, 800
gelatinosa centralis, 754
of Rolando, 753
nerve cells in, 758
grisea centralis, 753
innominata of Meynert, 837
nigra, 802
ossea, 1120
perforata anterior, 827
proj^ria [cornea], 1007
Subthalamic tegmental region,
812 _
Suctorial pad, 384
Sudoriferous glands, 1070
Sulci and fissures of cerebral
hemisphere, 819
development of, 747
of medulla oblongata, 767
spinalis, 752
Sulcus, anterior longitudinal, of
heart, 527
antihelicis transversus, 1034
arterial vcrtebralis, 99
basilaris, 785
calcaneal, 263
central, 819
centralis [Rolandi], 819
cingulate, 820
cinguli, 820
circular, 821, 825
circular is, 821
cornea, 1007
coronary, of heart, 526
frontal, 821
horizontal, of cerebellum, 789
intermcdius [stomach], 1162
intraparietal, 822
lateral cerebral, 801
limitans [rhomboid fossa], 799
lunatus, 823 note
malleolar, 262
medial frontal, of Eberstaller,
822
median, of rhomboid fossa, 799
of tongue, 1125
medianus posterior, 752
of Monro, 741, 742, 816
occipital, 823
oculomotor, 801
olfactory, 822
orbital, 822
paramedial, 822
postcentral, 822
posterior longitudinal, of
heart, 527
preauricular, of ilium, 234
precentral, 821
radial, 211
retroglandular, 1249
sagittalis, 131, 134, 136
sigmoid, 142
spirales, 1055
subparietal, 823
tali, 267
temporal, 824
terminal, of right atrium, 529
of tongue, 1125
tuhce audit iva:, 150, 181
tympanic, 145, 1037, 1039
vallecula, 790
Supercilia, 1025
Superciliary arches, 135, 178, 183
Superficial antero-lateral fasci-
culus, 854
cervical artery, 582
lymph glands 697
muscle, 387
1390
INDEX
Superficial cervical nerve, 927
epigastric artery, 629
external pudendal artery, 629
pudic artery, 623
iliac circumflex artery, 629
long plantar ligament, 354
palmar arch, 598
perineal artery, 619
peroneal nerve, 966, 96S
Sylvian vein, 652
temporal artery, 558
vein, 645
transverse ligament of fingers,
461
perineal muscle, 427, 430
volar artery, 594
Superficialis voUe artery, 594
Superf rental gyre, 821
Superior articular arteries, 633
calcaneocuboid ligament, 354
cerebellar peduncles, 792
constrictor muscle, 1143
dental nerve, 890
intercostal artery, 585
lingualis muscle, 1130
longitudinal sinus, 654
maxillary nerve, 889
medullary velum, 793
nasal concha, 156
nuchal line, 130
oblique muscle, 1022
orbital fissure, 151, 189
petrosal sinus, 659
profunda artery, 591
sagittal sinus, 654
semicircular canal, 1049
tarsal plate, 1025
thoracic artery, 587
tibiofibular articulation, 348
tympanic artery, 561
vesical artery, 615
vocal cords, 1079
Supernumerary spleen, 1283
Supinator brevis muscle, 454
longus muscle, 451
muscle, 454
Supra-acromial nerves, 928
Supporting cells of Hensen, 1058
of Sertoli, 1213
frame-work of retina, 1017
Supracallosal gyrus, 827
Supraclavicular branches of
brachial plexus, 932
nerves, 928
Supraclavicularis muscle, 390
Supracondylar process, 212 note
ridges, 211
Supracostalis muscle, 403
Supraglenoid tuberosity, 207
Suprahyoid aponeurosis, 392
artery, 553
lymph glands, 697
muscles, 391
triangle, 392, 565
Supramarginal gyrus, 823
Supramastoid crest, 139
Suprameatal spine, 145, 183
triangle, 140, 183
Supraorbital arterv, 569
foramen, 136, 186, 189
margin, 135
nerve, 887
notch, 136, 186, 189
vein, 644
Suprarenal arteries, 610, 612
glands, 1278
development of, 1278
Ij-mphatic vessels of, 711
nerves of. 1280
vessels of, 1280
impression, 1191
plexus, 987
veins, 679
Suprascapular artery, 582
ligament, 317
Suprascapular nerve, 932
Supraspinal ligament, 290
Supraspinatous fascia, 440
fossa, 203
Supraspinatus muscle, 440
Supraspinous ligament, 290
Suprasternal nerves, 298
space, 389
Supratonsillar fossa, 1138
Supratrochlear foramen, 212
nerve, 888
Sural arteries, 633
cutaneous nerve, medial, 962
nerve, 963
Surface anatomy and surface
markings of abdomen, 1315
accessorj- nerve, 1303
acromioclavicular joint, 1328,
1331
adductor canal, 1343
ankle-joint, 1338, 1343
anterior tibial arterj-, 1341,
1346
aorta, abdominal 1313, 1321
ascending, 1312
aortic arch, 1312
axillary artery, 1331, 1334
nerve, 1336
back, 1303
bones of cranium, 1291
of lower extremity, 1336
of thorax, 1308
' of upper extremity, 1325
brachial arterv, 1331, 1335
plexus, 1303, 1331
brain, 1292
Bryant's triangle, 1343
calcaneus, 1337
carpal bones, 1327
caruncula lacrimalis, 1299
cecum, 1319
celiac artery, 1322
cerebellum. 1292
cerebral hemisphere, 1292
cervical cutaneous nerve,
1303
clavicle, 1326
colon, ascending, 1319
descending, 1320
iliac, 1320
transverse, 1319
common carotid artery, 1302
iliac artery, 1322
peroneal nerve, 1342. 1346
deep peroneal nerve, 1346
deltoideus muscle, 1329
diaphragm, 1309
dorsalis pedis artery, 1341,
1346
duodenum, 1319
ear, 1300
elbow-joint, 1331
esophagus, 1311
external carotid arterj-, 1302
iliac artery, 1322
maxillarj^ arterv, 1294
eye, 1299
facial nerve, 1303
femoral artery, 1341, 1346
triangle 1343
femur. 1336
fibula, 1337
fissures of brain, 1293
fold of groin, 1313
frontal sinus, 1294
gall-bladder, 1320
gluteal arteries, 1343
fold, 1336
great auricular nerve, 1303
head and neck, 1287
heart, 1311
coronary sulcus, 1311
longitudinal sulcus, 1311
orifices of, 1311
Hesselbach's triangle, 1321
Surface anatomy and surface
markings of hip bones,
1336
hip-joint, 1338, 1343
humeral circumflex artery,
1335
humerus, 1326
hyoid bone, 1301
ileocolic junction, 1319
iliac arteries, 1322
furrow, 1313
inferior, epigastric arterv,
1321
vena cava, 1312
infrasternal notch, 1307
inguinal rings and canal
1315
innominate artery, 1312
veins, 1312
internal mammary artery,
1312
pudendal arterv, 1343
intestines, 1319, 1320
joints of fingers, 1328
of foot, 1343
jugular notch, 1307
veins, 1303
kidneys, 1320
knee-joint, 1338
lacrimal puncta, 1299
sac, 1299
larynx, 1299, 1301
lateral plantar artery, 1346
thoracic artery, 1334
ventricle of brain. 1294
latissimus dorsi, 1328, 1333
left common carotid artery
in thorax, 1312
lesser occipital nerve, 1303
linea semilunaris, 1313
liver, 1314, 1320
lower extremity, 1336
lumbar triangle, 1313
lungs, 1310
mamma, 1308
maxillary sinus, 1294
medial plantar artery, 1346
median nerve, 1335
medulla sijinalis, 1306
mesenteric arteries, 1322
metacarpal bones, 1327
middle meningeal arterv,
1294
mouth, 1296
mucous sheaths around
ankle, 1343
of wrist and hand, 1334
muscles of abdomen, 1315
of arm. 1328
of buttock. 1338
of foot, 1340
of forearm, 1329
of head and neck, 1288,
1289, 1301
of hand, 1331
of leg, 1340
of thigh, 133S
nasal part of pharynx. 1299
nasolacrimal duct, 1299
neck, 1301
Nelaton's line, 1342
nose, 1296
palatine arches, 1297
palmar or volar arches, 1335
palpebral fissure, 1299
pancreas. 1315, 1320
parotid duct, 1295
gland, 1295
patella, 1337
pectoralcs muscles, 1328,1333
pelvis, 1336
perineum, 1322
peroneal artery, 1346
ncr\-es, 1346
phalanges of foot, 1338
INDEX
1391
Surface anatomy and surface
markings of phalanKos of
hand, 1327
phrenic nerve, 1303
plantar arch, 1346
arteries, 1346
pleur£E, 1309
plica semilunaris, 1299
popliteal artery, 1341
fossa, 1343
posterior tibial artery, 1342,
1346
profunda brachii artery, 1335
femoris arterj-, 1346
pupil, 1299
radial artery, 1331, 1335
nerve, 1336
radioulnar joints, 1328
radius, 1327
rectum and anal canal, 1322
Reid's base line, 1291
renal arteries, 1322
sacroiliac joint, 1343
saphenous veins, 1346
scapula, 1326
scapular circumflex artery,
1335
sciatic nerve, 1346
serratus anterior muscle, 132 8
shoulder-joint, 1328
spinal nerves, 1307
spleen, 1320
sternal angle, 1307, 1309
sternoclavicular joint, 1328
sternocleidomastoideus
muscle, 1289
stomach, 1317
strise gravidarum or albi-
cantes, 1313
subclavian artery, 1303, 1331
subdural and subarachnoid
cavities, 1306
submaxillary gland, 1303
subscapular artery, 1334
supraclavicular nerves, 1303
superior vena cava, 1312
talus, 1337
tarsus and foot, 1337
temporomandibular joint,
1288
tendinous inscriptions of rec-
tus abdominis, 1313
thoracoacromial artery, 1334
thorax, 1307
tibia, 1337
tibial nerve, 1346
tongue, 1297
tonsil, 1298
trachea, 1301, 1311
transverse sinus, 1294
trapezius, 1332
trigeminal nerve, 1295
tympanic antrum, 1301
membrane, 1300
ulna, 1326
ulnar artery, 1335
collateral arteries, 1335
nerve, 1331, 1335
umbilicus, 1313, 1315
upper extremity, 1325
urogenital organs, female,
1323
male, 1323
vermiform process, 1319
vertebral column, 1303
volar or palmar arches, 1335
wrist and hand, 1327
wrist-joint, 1327, 1331
Suspensorv ligament of axilla, 436
of eye, 1025
of lens, 1018
of ovary, 1254
of penis, 1249
Sustentacular fibers of Miiller,
1017
Sustentaculum lienis, 1158
tali, 266
Sutura dentala, 284
harmonia, 284
limbosa, 284
notha, 284
serrata, 284
squamosa, 284
vera, 284
Sutural bones, 156
Suture, coronal, 178, 183
frontal, 178
frontoethmoidal, 190
frontomaxillary, 189
lambdoidal, 132, 135, 178, 183
metopic, 135
occipitomastoid, 183
parietomastoid, 183
petrooccipital, 193
petrosquamous, 142, 145
sagittal, 178
sphenoethmoidal, 190
sphenofrontal, 182, 190
sphenoparietal, 182
sphenopetrosal, 190
sphenosquamosal, 182
sphenozygomatic, 182
squamosal, 183
zygomaticofrontal, 182
zygomaticomaxillary, 189
zygomaticotemporal, 182
Sweat glands, 1070
Syh-ian fissure, 747
fossa, 747
veins, 652, 653
Sylvius, aqueduct of, 766, 767, 806
fissure of, 819
Sympathetic fibers of spinal
nerves, 920
nerves, 968
connections with spinal
nerves, 976
plexuses, 984, 985, 987
system, cephalic portion of, 977
cephalic portion of, 977
cervical portion of, 978
pelvic portion of, 984
thoracic portion of, 981
trunks, 976
Symphysis of mandible, 127
ossium pvbis, 310
pubis, 310
sacrococcyoea, 309
Synarthroses, 286
Synchondrosis, 284
neurocentral, 112
Syucytiotrophoblast, 47
Syncytium, 47
Syndesmology, 279
Syndesmosis, 285
tibiofibularis, 348
Synergic muscles, 362
Synovia, 283
Synovial membrane, 282. See
also Individual Joints.
Systemic circulation, 497
veins, 641
Tables of the skull, 79
Tactile corpuscles of Golgi and
Mazzoni, 1061
of Grandry, 1060
of Pacini, 1060
of Ruffini, 1061
of Wagner and Meissner,
1061
discrimination, fibers of, 854
Tcenia pontis, 785
semicircularis, 837, 869
thalami, 809
ventriculi quarti, 797
ToenicE coli, 1185
TsenijE of fourth ventricle, 797
of muscular coat of large intes-
tine, 1177
Talocalcaneal articulation, 352
Talocalcaneonavicular articula-
tion, 353
Talotibial ligaments, 351
Talus, 266
ossification of, 275
Tangential fibers of cerebral
cortex, 846
Tapetum of choroid, 1010
of corpus callosum, 829
Tarsal arteries, 637
bones, 263
glands, 1026
plates, 1025
Tarsi of eyelids, 1025
Tarsometatarsal articulations,
358
Tarsus, 263
articulations of, 352
inferior, 1025
ossification of, 275
superior, 1025
surface markings of, 1343
synovial membranes of, 358
Taste fibers, 867
nerves of, 992
organ of, 991
Taste-buds, 991
Tectorial membrane of ductus
cochlearis, 1058
Tectospinal fasciculus, 871
Teeth, 1112
bicuspid, 1118
canine, 1117
cement or crusta petrosa of,
1120
crown of, 1116, 1117
cutting, 1115
deciduous, 1118
dental canaliculi of, 1119
dentin of, 1119
development of, 1121
enamel of, 1120
eruption of, 1124
eye, 1117
general characters of, 1114
incisive, 1115
incisors, 1115
ivory of, 1119
milk, 1118
molar, 1118
multicuspid, 1118
necks of, 1114
permanent, 1115
successional, 1124
superadded, 1124
premolar, 1118
pulp cavity of, 1118
loots of, 1114
stomach, 1117
structure of, 1118
substantia adamantina of, 1120
eburnea of, 1119
ossea of, 1120
temporary, 1118
wisdom, 1118
Tegmen tympani, 124, 1038
Tegmental part of pons, 786
Tegmentum, 802
Tela chorioidea [fourth ventricle],
798
[third ventricle], 841
Telencephalon, 743, 817
Telophase of karyokinesis, 38
Temperature, impulses of, 853
Temporal arteries, 558, 561
bone, 138
articulations of, 147
mastoid portion of, 141
ossification of, 145
petrous portion of, 142
pyramid of, 142
1392
INDEX
Temporal bone, squama of, 139
structure of, 1-15
tympanic part of, 145
fascia, 386
fossa, 183
gyri, 824
lines, 134, 136, 178, 183
lobe, 823
muscle, 386
nerves of auriculotemporal, 895
deep, 895
of facial, 905
operculum, 825
process of zygomatic bone, 166
veins, 645
Temporalis muscle, 386
Temporary teeth, 1118
Temporomalar nerve, 889
Temporomandibular articulation,
297
surface anatomy of, 1288
Temporomaxillary vein, 646
Tendinous arch of pelvic fascia,
422
inscriptions of rectus abdomi-
nis muscle, 416
Tendo Achillis, 483
calcaneus, 483
oculi, 468
Tendon, action of muscle pull on,
364
central, of diaphragm, 406
conjoined, of internal oblique
and transversalis muscles, 4 14
of conus arteriosus, 531
superior, of Lockwood, 1022
of Zinn, 1022
Tendons, 376
on back of wrist, relations of,
458
Tendril fibers of cerebellum, 796
Tenon, capsule of, 1037
Tensor fasciae latce muscles, ac-
tions of, 478
nerves of, 478
palati muscle, 1139
tarsi muscle, 380
tympani muscle, 1046
semicanal for, 145, 1042
veli palatini muscle, 1139
Tenth nerve, 910
Tentorial sinus, 655
Tentorium cerehelli, 874
Teres major muscle, 442
minor muscle, 441
variations of, 442
Terminal crest of right atrium,
529
sulcus of right atrium, 529
vein, 653
ventricle, 735, 754
Testes, 1236, 1240
appendages of, 1242
coni vasculosi of, 1244
coverings of, 1236
descent of, 1210
development of, 1210
ductuli efferentes, 1244
ductus deferens, 1245
gulfernaculum testis, 1211
lobules of, 1243
lymphatic capillaries of, 687
vessels of, 713
mediastinum testis, 1243
rete testis, 1244
structure of, 1243
tubuli recti, 1244
seminiferi, 1243
tunica albuginea, 1242
vaginalis, 1242
vasculosa, 1242
Thalamencephalon, 808
Thalami, 742, 808
connections of, 810
development of, 742
Thalami, intermediate mass of,
742, 743, 809
stalks of, 811
structure of, 810
surfaces of, 808, 809
Thalamic tract of cranial nerves,
805
Thalamomammillary fasciculus,
839
Thebesius, foramina of, 530
valve of, 530, 642
veins of, 643
Thenar eminence, 456
Thigh bone, 242
fascia lata of, 468
superficial, 468
muscles of, 467
Third cuneiform bone, 271
metacarpal bone, 228
metatarsal bone, 274
nerve, 884
trochanter. 246
ventricle of brain, 815
Thoracic aorta, 598
peculiarities of, 599
arteries, 587, 588
axis, 588
cardiac nerves, 912
duct, 690
nerves, divisions of, 923, 944
portion of gangliated cord, 981
vertebrae, 102
Thoracoacromial artery, 588
Thoracodorsal nerve, 934
Thoracoepigastric vein, 670
Thoracolumbar sympathetics, 974
Thorax, 117
boundaries of, 117
cavity of, 524
lymph glands of, 715
lymphatic vessels of, 715, 716
mechanism of, 304
muscles of, 402
openings of, 117, 118, 524
parts passing through, 524
skeleton of, 117
surface anatomy of, 1307
markings of, 1308
Thromboplastin, 505
Thumb, carpometacarpal articu-
lation of, 330
Thymus, 1273
development of, 1273
glands, 1273
lymphatic capillaries in, 686
vessels of, 719
nerves of, 1275
structure of, 1274
vessels of, 1275
Thyreoarytsenoideus muscle,
1083
Thj-reohyoideus muscle, 394
a<'tion of, 394
nerves of, 394, 916
Thyreoidea ima artery, 549
Thyroarytenoid ligaments, 1080
muscle, 1083
Thyrocervical trunk, 581
Thyroepiglottic ligament, 1078
muscle, 1083
Thyroglossal duct, 1126
Thyrohyals of hyoid bone, 178
Thyrohyoid ligaments, 1077
membrane, 1076
muscle, 394
Thyroid arteries, 552, 581
axis, 581
body, 1269
cartilage, 1073
foramen, 237
gland, 1269
development of, 1270
isthmus of, 1270
lobes of, 1269
lymphatic capillaries in, 686
Thyroid gland, lymphatic ves-
sels of, 697
nerves of, 1271
pyramidal lobe of, 1270
structure of, 1271
vessels of, 1271
notch, superior, 1073
veins, 649, 666
Thyroids, accessory, 1270
Tibia, 256
condyles of, 256
ossification of, 260
spine of, 256
surface anatomy of, 1337
tuberosity of, 256
Tibial artery, anterior, 634
branches of, 635
peculiarities of, 635
surface marking of, 1337
posterior, 637
branches of, 638
peculiarities of, 638
surface marking of, 1 346
recurrent, 635
collateral ligament of knee-
joint, 341
nerve, 960
anterior, 965
surfaces of femur, 248
veins, 672
Tibialis anterior muscle, 480
anticus muscle, 480
posterior muscle, 485
Tibiofacialis muscle, 480
Tibiofibular articulation, 348
ligament, middle, 348
syndesmosis, 348
Tibionavicular ligament, 350
Tibiotarsal articulation, 349
Tomes' fibers, 1119
Tongue, 1125
development of, 1102
dorsum of, 1125
frenulum of, 1125
glands of, 1131
lymph gland of, 696
lymphatic vessels of, 696
mucous membrane of, 1131
muscles of, 1128
actions of, 1131
nerves of, 1132
papillae of, 1126
septum of, 1132
structure of, 1131
vessels of, 1132
Tonsilla cerehelli, 791
Tonsillce intesiinales, 1176
palatiud, 1137
Tonsillar artery, 555
nerves from glossopharyngeal,
909
sinus, 1138
TonsUs, 1137
lingual, 1131
palatine, 1137
development of, 1103
lymphatic vessels of, 695
nerves of, 1139
structure of, 1139
vessels of, 1139
pharyngeal, 1142
Torcular Herophili, 131, 658
Torus of auditory tube, 1141
uretericus, 1232
ulerinus, 1154
Touch fibers, 854
Trabecular carnece, 532, 535
cranii, 84
of penis, 1250
of spleen, 1283
of testis, 1243
Trachea, 1084
lymphatic capillaries in, 686
nerves of, 1087
relations of, 1084
INDEX
1393
Trachea, structure of, 1086
vessels of, 1087
Trachealis muscle, 1087
Trachelomastoid muscle, .399
Tracheobronchial glands, 717
Trachoma glands, 1028
Tract or Tracts, anterior basis
bundle, 700
of Burdach, 752, 763
central, of cranial nerves, 804
of trigeminal nerve, 805
cerebellar, of Flechsig, 761
comma, 764
dorsal peripheral band, 764
of Goll, 752, 762
of Gowers, 761, 754
lateral basis bundle, 762
of Lissauer, 762
olfactory, 826
optic, 814, 884
prepyramidal, 761
pyramidal, 759, 760
thalamic, of cranial nerves, 805
Traction epiphyses, 95
Tractus iliotibialis, 468
olfaciomcsenccphalicus, 867
olfactorius, 826
peduncularis transversus, 802
note
spiralis foraminosus, 143, 1050
Tragicus muscle, 1035
Tragus, 1034
Transpyloric plane, 1147
Transversa colli artery, 582
Transversalis cervicis muscle, 399
colli artery, 582
fascia, 418
muscle, 414
Transverse acetabular ligament
of hip-joint, 336
aorta, 547
carpal ligament, 456
cervical arteries, 582
nerve, 927
colon, 1180
crural ligament, 488
facial artery, 558
vein, 645
fibers of cerebral hemispheres,
841,842
fissure of brain, 842
of liver, 1191
folds of rectum, 1183
ligament of atlas, 293
of fingers, 461
humeral, 319
of knee, 343
metacarpal, 331
metatarsal, 359
of pelvis, 429
ligaments of scapula, 317
lingualis muscle, 1130
mesocolon, 1157
occipital sulcus, 823
process of a vertebra, 96
scapular artery, 582
sinus, 660
of pericardium, 526
temporal gyri, 824
Transversus abdominis muscle,
414
variations of, 414
auriculae muscle, 1035
linguoe muscle, 1130
menti muscle, 383
nuchse muscle, 380
pedis muscle, 493
perinaei muscle, 427
profundus muscle in female,
431
in male, 429
superficialis muscle, actions
of, 428, 430
in female, 430
in male, 427
88
Transversus thoracis muscle, 403
Trapezium, 225
Trapezius muscle, 432
actions of, 435
nerves of, 434
variations of, 432
Trapezoid, 225
body, 787
ligament, 315
nucleus, 787
ridge, 200
Treves, bloodless fold of, 1100
Triangle of auscultation, 434
Bryant's, 1343
carotid, 392, 394, 564
digastric, 564
femoral, 626
of Hesselbach, 1321
lumbar, 434
muscular, 394, 563
of neck, 562
occipital, 394, 565
of Petit, 434
Scarpa's, 626
subclavian, 394, 565
submaxillary, 392, 564
submental, 392
suboccipital, 402, 578
suprahyoid, 392, 565
suprameatal, 140, 183
Triangular articular disk, 325
bone, 224
fascia of abdomen, 412
ligament, 428
of liver, 1150, 1151
Triangularis muscle, 383
sterni muscle, 403
Triceps brachii muscle, 444
extensor cubiti muscle, 444
muscle, 444
surne muscle, 483
Tricuspid valve, 531
Trifacial nerve, 886
Trigeminal impression, 143
nerve, 886
central tract of, 805
composition and central con-
nections of, 862
reflexes, 899 _
. surface marking of, 1295
Trigone, olfactory, 827
Trigonutn coUaierale, 833
femorale, 626
habcnulcE, 812
hypoglossi, 799
olfactorium, 827
vagi, 781
vesicae, 1231
Trochanter, greater, 244
lesser, 245
third, 246
Trochanteric fossa, 244
Trochlea of humerus, 212
Trochlear fovea, 137, 188
nerve, 885 _
composition and central con-
nections of, 863
process of calcaneus, 266
spine, 137
Trochoid joint, 285
Trolard, anastomotic vein of, 652
Troltsch, recess of, 1046
Trophoblast, 46
True nucleoli, 37
pelvis, 239
skin, 1065
vocal cords, 1080
Trvncus arteriosus, 508, 514
costocervicalis, 585
sympathicus, 976
thyreocervicalis, 581
Trunk, arteries of, 598
articulations of, 287
costocervical, 585
thyrocervical, 581
Tuba auditiva, 1042
uterina [Fallopii], 1257
Tube, auditory, 1042
digestive, 1100
Eustachian, 1042
p-allopian, 1257
neural, 50
uterine, 1257
Tuber cinereum, 775
frontale, 135
omentale [liver], 1189
[pancreas], 1201
parietale, 133
valvula, 791
vermis [cerebellum], 791
Tuberse lobe, 791
Tubercle, adductor, 246
anterior, 99
articular, of temporal bone,
139, 180
auricular, of Darwin, 1033
conoid, 200
cuneate, 774
cuneiform, 1079
of epiglottis, 1076
of femur, 245
of humerus, 209
intervenous, 531
jugular, 131
lacrimal, 161
of Lower, 531
mental, 172
obturator, 273
peroneal, 266
pharyngeal, 132, 180
posterior, 99
pterygoid, 152
pubic, 236
of rib, 124
of Rolando, 775
scalene, 125
Tuberculum acusticum, 800, 906
impar, 1102
intervenosum, 531
ma jus [humeri], 209
minus [humeri], 209
sella', 147, 190
Tuberosity, calcaneal, 266
coracoid, 200
costal, 202
of cuboid, 269
deltoid, 211
of fifth metatarsal bone, 274
gluteal, 246
iliac, 234
infraglenoid, 205
of ischium, 235
maxUlary, 159
of navicular bone, 270
of palatine bone, 168
radial, 219
supraglenoid, 207
of tibia, 256
of ulna, 214
Tubules, renal, 1223
Tubidi lactifcri, 1268
recti [testis], 1244
seminij'eri, 1243
Tunic, dartos, 1238
fibrous, of kidney, 1220
Tunica adventitia, 499
albuginea [ovary], 1256
[testis], 1242
conjunctiva bulbi, 1027
dartos, 1238
elastica externa, 499
fibrosa oculi, 1005
intima, 498
media, 498
serosa, 1149
vaginalis, 1242
communis [testis et funiculi
spermatid], 1239
propria testis, 1242
vasculosa [testis], 1243
1394
INDEX
Tunica vasculosa oculi, 1009
Tunics of eyeball, 1005
Tunnel of Corti, 1057
Turbinated bone, 169
processes, sphenoidal, 152
Turner, intraparietal sulcus of,
822
Twelfth nerve, 914
Tympanic antrum, 142
artery, 560
from ascending pharj'ngeal,
558
from internal maxillary
560
canaliculus, inferior, 144, 181
cavity, 1037
arteries of, 1046
attic or epitympanic recess
of, 1038
carotid or anterior wall of,
1042
jugular wall or floor of, 1038
labyrinthic or median wall
of, 1040
mastoid or posterior wall of,
1042
membranous or lateral wall
of, 1038
mucous membrane of, 1046
muscles of, 1046
nerves of, 1046
ossicles of, 1044
tegmental wall or roof of,
1038
vessels of, 1046
lip, 1055
membrane, 1039
nerve (Jacobson's), 909, 1047
plexus, 909, 1047
ring, 146
sulcus, 145, 1037, 1039
Tympanohyal part of styloid
process, 145
Tympanomastoid fissure, 144, 181
Tympanum, 1037
Ulna, 214
articulations of, 219
coronoid process of, 214
radial notch of, 215
semilunar notch of, 215
sigmoid cavities of, 215
styloid process of, 218
surface anatomy of, 1326
Ulnar artery, 595
surface marking of, 1335
notch of radius, 220
Ultimobranchial bodies, 1273
Umbilical arteries in fetus, 61,
540
cord, 57
folds, 1231
fossa of liver, 1191
notch of liver, 1191
veins, 61, 507, 519
obliterated, 681, 1150
zcaie, 1148, 1149
Umbilicus, 417
Umbo of membrana tympani,
1039
Unciform bone, 227
Uncinate fasciculus, 843
Unconscious muscle sense, im-
pulses of, 851
Uncus, 826
Ungual phalanges, 230, 275
Ungues, 1066
Urachus, 1213
Ureter, 1225
arteries of, 1227
lymphatic vessels of, 712
muscles of, 1233
Ureter, nerves of, 1227
orifices of, 1232
Urethra, development of, 1215
female, 1236
male, 1234
crest or verumontanum of,
1234
lymphatic vessels of, 713
muliebris, 1236
virilis, 1234
Urethral artery, 619
bulb, 1235
crest, in female, 1236
in male, 1234
glands, 1235
orifices, 1232, 1235, 1266
plate, 1215
Urinary bladder, female, 1230
lymphatic capillaries in, 687
male, 1227
meatus, 1266
organs, 1215
Urogenital apparatus, 1204
diaphragm, 428
fold, 1206
organs, 1204
ostium, primitive, 1215
Urorectal septum, 1109
Uterine artery, 615
glands, 1262
plexus of nerves, 989
plexuses of veins, 676
tube, 1257
Uterosacral ligaments, 1260
Uterus, 1258
in adult, 1262
after parturition, 1262
cervix of, 1259
development of, 1207
during menstruation, 1262
pregnancy, 1262
in fetus, 1261
form, size, and situation of, 1261
fundus of, 1259
interior of, 1260
isthmus of, 1259
ligaments of, 1260
lymphatic capillaries of, 687
vessels of, 714
masculinus, or prostatic utricle,
1234, 1235
nerves of, 1263
in old age, 1262
at puberty, -1261
virgin state of, 1259
Utricle, prostatic, 1234
of vestibule, 1051
Utriculus, 1051
Uvea, 1013
Uvula of cerebellum, 791
palatine, 1112
vermis, 791
vesicir, 1232
Uvular lobe, 791
Vagina, 1264
lymphatic vessels of, 714
VagiiKV mucoi^w, 283
Vaginal artery, 616
bulb, 1266
orifice, 1266
plexus of nerves, 989
plexuses of veins, 677
process of temporal bone, 144,
145
processes of sphenoid bone, 151
Vagus nerve, 910
composition and central con-
nections of, 855
sympathetic afferent fil)ers,
973
efferent fibers of, 972
Vallecula cerebelli, 788
Valleculse of tongue, 1075
Vallum, 1126
Valsalva, sinuses of, 533, 534
Valve, bicuspid, 534
colic, 1179
of coronary sinus, 530, 642
Eustachian, 530
ileocecal, 1179
of inferior vena cava, 530, 678
mitral, 534
pyloric, 1164
Thebesian, 530, 642
tricuspid, 531
of Vieussens, 793
Valves, anal, 1184
of heart, development of, 514
of Houston, 1183
ofKerkring, 1173
of lymphatics, 687
right and left venous, 510
semilunar aortic, 534
pulmonary, 532
of veins, 501
Valvula bicuspidalis [metralis], 534
coll, 1179
sinus coronarii [Thebesii], 531
tricuspidalis, 531
vena cavce inferioris, 530
Valvulm conniventes, 1173
Vas aberrans of Haller, 1246
deferens, 1245
spirale, 1056
Vasa aberranlia [from brachial
artery], 590
brevia arteries, 606
intestini tenuis arteries, 607
vasorum [arteries], 499
[veins], 502
Vascular areas of yolk-sac, 505
capsule of lens, 1003
system, changes in, at birth,
542
development of. 505
peculiarities in fetus, 539
Vasomotor nerve fibers, 728
Vastus externus muscle, 470
intermedius muscle, 471
internus muscle, 471
lateralis muscle, 470
medialis muscle, 471
Vater, ampulLa of, 1 199
Vein or Veins, of abdomen, 672
anastomotic, of Labbe, 652
angular, 645
auditory, 1059
auricular, 646
axillary, 663
azygos, 667
basal, 653
basilic, 662
median, 661
basivertebral, 668
brachial, 663
brachiocephalic, 664
of brain, 652
bronchial, 697, 1100
cardiac, 642, 643
cardinal, 520
cephalic, 661
accessory, 662
cerebellar, 653
cerebral, 652, 653
choroid, 653
coats of, 501
common facial, 645
iliac, 677
coronary, 642
of stomach, 682
of corpus striatum, 838
cystic, 682
deep cerebral, 653
cervical, 651
ei^igastric, 672
facial, 645
INDEX
1395
Vein or Veins, dcep.of forearm,663
of hand, 663
of lower extremity, 671
of upper extremity, 663
development of, 518
digital, of foot, 669
of hand, 660
diploic, 051
dorsal digital, 660
metacarpal, 660, 663
of penis, 076
emissary, 660
epigastric, 672
extraspinal, 668
facial, 645
femoral, 672
frontal, 644
of Galen, 653
gastroepiploic, 681
gluteal, 673
of hand, 660, 663
of head and neck, 643
of heart, 642
hemiazygos, 667
hemorrhoidal, 676, 681
hepatic, 680
histology of, 501
hypogastric, 673
iliac, 672, 673, 677, 678
iliolumbar, 678
inferior vena cava, 677
innominate, 666
intercapitular, 661, 669
intercostal, highest, 666
interlobular, of kidney, 1224
of liver, 1196
intervertebral, 669
intralobular, of liver, 1197
intraspinal, 668
jugular, 646, 647, 648
primitive, 520
of Labbe, posterior anasto-
motic, 652
labial, 645
lateral sacral, 673
of left atrium, 526
lienal or splenic, 081
lingual, 648
of lower extremity, 669
lumbar, 678
ascending, 667
mammary, internal, 066
marginal, of foot, 669
masseteric, 645
maxillary, internal, 646
median antibrachial, 662
basilic, 601
of medulla spinalis, 669
mesenteric, 682
metatarsal, 072
nasofrontal, 659
of neck, 640
oblique, of left atrium [Mar-
shalli], 522, 520, 043
obturator, 073
occipital, 040
ophthalmic, 658
orbital, 045
ovarian, 079
palpebral, 045
pancreatic, 081
pancreaticoduodenal, 682
parumbilical, 082
of pelvis, 072
penis, dorsal of, 670
peroneal, 072
pharyngeal, 049
phrenic, inferior, 679
superior, 000
plantar, 671
plexus of, basilar, 600
hemorrhoidal, 070
prostatic 676
pterygoid 645
pudendal, 676
Vein or Veins, plexus of, uterine,
676
vaginal, 677
verteljral, 608
vesi("il, 070
vesicoprostatic, 070
popliteal, 072
portal, 6S0
posterior of left ventricle, 643
primitive jugular, 520
profunda femoris, 672
pubic, 673
pudendal, internal, 674
pudic, 674
pulmonary, 642
pyloric, 682
ranine, 048
renal, 679, 1224
sacral, 673, 077
saphenous, 070
sciatic, 074
short gastric, 681
spermatic, 678
of spinal cord, 609
splenic or lional, 081
striate, inferior, 053
structure of, 501
subcardinal, 520
subclavian, 604
sublobular, of liver, 1197
superficial, 041
of lower extremity, 669
of upper extremity, 6G0
superior cerebral, 652
mesenteric, 082
phrenic, 006
vena cava, 066
supraorbital, 045
suprarenal, 079
Sylvian, 052, 053
systemic, 642
• temporal, 045
temporomaxillary, 046
terminal, 653
of Thebesius, 643
thoracoepigastric, 670
of thorax, 064
thyroid, inferior, 600
middle, 649
superior, 649
• tibial, 672
transverse facial, 645
Trolard, great anastomotic of,
652
umbilical, 62, 507
obliterated, 681, 1150
of upper extremity, 600
valves of, 501
vena azygos major, 607
minor, 007
cava, inferior, 667
superior, 666
vertebral, 051
of vertebral column, 667
visceral, 518
vitelline, 500, 518
volar, 001, 003
Velamentous insertion of um-
bilical cord, 65
Velum interposiium, 841
medullarw, 793, 794
medullary, 793, 794, 797
palatine, 1112
Vena angularis, 645
anonyma dextra, 664
sinistra, 666
auricularis posterior, 646
axillaris, 663
azygos, 067
basilica, 062
cava inferior, 677
superior, 606
surface marking of, 1312
caval foramen in diaphragm,406
cephalica accessoria, 002
Vena cerebri magna, 053
media, 052
cervicalis profunda, 051
circumjlcxa ilium profunda, 673
cordis, ()42, 643
coronaria venlriculi, 682
corporis striata, 653
cystica, 082
epigastrica inferior, 672
facialis anterior, 645
posterior, 646
femoralis, 072
frontalis, 044
gastroepiploica, 081, 082
hcmorrhoidalls media, 076
hemiazygos, 077
accessoria, 077
hypogastrica, 073
iliaca externa, 072
jugularis anterior, 647
externa, 646
interna, 648
posterior, 647
linealis, 081
magna [Galeni], 053, 842
rnaxillaris interna, 040
mediana antibrachii, 002
cubiti, 601
mesenterica inferior, 681
superior, 682
obliqua atrii sinistri [Marshalli],
643
obturatoria, 676
occipitalis, 646
ophthalmica, 659
popliiea, 672
portoE, 681
posterior ventriculi sinistri, 043
profunda femoris, 072
saphena magna, 009
parva, 670
subclavia, 664
supraorbitalis , 645
temporalis super ficialis , 045
terminalis, 053
thyreoidea superioris, 049
vertebralis, 049
Vena; advehentes, 519
anonymae, 664
basivertebrales, 068 *
brachiales, 603
bronchiales, 007
cerebelli, 053
cerebri, 052, 053
comitantes, 641
cordis, 042
mini?n(B, 530
digitales plantar es, 671
diploicce, 051
dorsales penis, 676
Galeni, 842
gastrica: breves, 681
glutaecE, 674
hepaticcE, 680
iliacae communes, 077
intercostales suprema, 006
intervertebrales, 669
linguales, 648
lumbalcs, 678
mammaria: internee, 666
ovariac'V, 679
pancreaiicw, 681
pancreaticoduodenales, 682
parumbilicales, 682
pharyngea', 649
phrenicw inferiores, 679
propria renales, 1225
pulmonales, 642
rectve [kidney], 1224
renales, 079
revehentes, 519
sacrales, 070, 077
spermatica, 078
spinales, 009
stellatw [kidney], 1224
1396
INDEX
VencE suprarenales, 669
thgreoidecc injeriores, 666
tibiales,, 672
vorlicosa:, 1010. 1021
Venous arches, 669
lacunae of dura mater, 655
mesocardium, 526
plexus, hemorrhoidal, 676
ovarian, 679, 1256
pampiniform, 678, 1240. 1256
pharyngeal, 649
pterygoid, 645
pudendal, 676
spermatic, 678, 1240
uterine, 676
vaginal, 677
vesical, 676
sinuses, 641
of dura mater, 654
development of, 522
valves, right and left, 510
Ventral cochlear nucleus, 7SB
fissure of medulla oblongata,
767
lamina, 735
longitudinal bundle, 803
mesogastrium, 1103
psalterium. 869
pulmonary nerves, 193
spinal artery, 579
spinothalamic fasciculus, 854
Ventricle of fornix, 838
of mid-brain, 806
terminal, of medulla spinalis,
754
of Verga, 838
Ventricles of brain, 797,798, 815,
829
of heart, 508, 531, 534
of larynx, 1080
Ventricular folds of larynx, 1079
ligament of larj-nx, 1080
septum, 512, 534
Ventricularis muscle, 1083
Ventriculus, 1161
dexter, 531
laryngis [Morgagni], 1080
lateralis, 829
quartus, 797
tertius, 815
Ventromedian fissure of medulla
oblongata, 767
Verga, ventricle of, 838
Vermian fossa, 131
Vermiform process or appendix,
1178
Vermis of cerebellum, 788, 790
Vertebra prominens, 101
Vertebrae, 96
cervical, 97
coccjgeal, 106
ligaments of, 287-291
lumbar, 104
sacral, 106
thoracic, 102
Vertebral arch, 96
arches, articulations of, 289
artery, 578
canal, 116
column, 96, 114
articulations of, 287
surface form of, 1305
veins of. 667
foramen, 96
groove, 115
notches, 97
part of base of skull, 84
• ribs, 123
veins, 651
venous plexuses. 668
Vertical index of skull, 198
lingualis muscle, 1131
part of palatine bone, 167
"\erticalis linguae muscle, 1131
Verumontanum, 1234
Vesica fellea, 1197
urinaria, 1227
Vesical artery, 615
layer of pelvic fascia, 422
plexus of nerves, 988
of veins, 676
Vesicle, auditory, 1030
blastodermic, 46
germinal, 39
lens, 1001
optic, 742, 1001
Vesicoprostatic plexus of veins,
676
V'esicouterine excavation, 1152
Vesiciihe seminales, 1246
Vesicular ovarian follicles, 1256
Vestibular arteries, 1059
bulb, 1266
fissure, 1051
ganglion, 1058
glands, greater, 1266
lip, 1055
membrane, 1054
nerve, 906, 1058
composition and central con-
nections of, 860
nuclei of, 788
Vestibule, aortic, 534
of internal ear, 1047
of larvnx, 1078
of mouth, 1110
of nasal cavity, 994
of omental bursa, 1156
of vagina, 1266
\'estibulospinal fasciculus, 803,
872
tract, 760
Vestibulum, 1047
oris, 1110
ragiiKP, 1266
Vestigial fold of Marshall, 643
of pericardium, 526
Vicq d'Azyr, bundle of, 810, 813,
839, 869
Vidian arterj-, 562, 568
nerve, 892
Vieussens, valve of, 793
Villi, arachnoid, 878
of chorion, 60
of intestine, 1174
Visceral arches, 65
veins, 518
Visual area of cortex, 847
centres, 814
purple, 1015
Visuopsychic, area, 847
\"isuosensory area, 847
Vitelline circulation, 54, 507
duct, 1103
fluid, 54
membrane, 45
veins, 506, 518
Vitreous body of eye, 1018
table of skull. 79
Vocal cords, 1079, 1080
folds, 1080
process of arj-tenoid cartilage,
1075
Vocalis muscle, 1083
Voice, organs of, 1072
Volar arches, 595, 598
surface markings of, 1335
branch of ulnar nerve, 942
carpal artery. 594
ligament, 456
net-work, 594
digital arteries, 598
nerves, 938
interosseous artery, 596
nerve, 938
metacarpal arteries, 595
veins, 663
venous arches, 663
^"olaris indicis radialis artery,
595
Vomer, 170
Vomeronasal cartilage, 996
organs, 71, 996
Vulva, 1264
Wagner and IVIeissner, cor-
puscles of, 1061
Waldeyer, germinal epithelium
of, 1029
odontoblasts of, 1118
zona vasculosa of, 1256
Wallenburg, basal olfactorj- bun-
dle of, h67
Wallerian degeneration, 759
Wandering cells. 377
Wharton, duct of, 1135
jelly of, 58
Willis, circle of, 574
Windpipe, 1084
Winslow, foramen of, 603, 1100,
1156
Wirsung, duct of, 1202
Wisdom teeth ,1118
Wolffian bodv, 1205
duct, 1205
tubules, 1205
Womb, 1258
Wormian bones, 156
Wrisberg, cardiac ganglion of,
984
cartilages of, 1075
ligament of, 343
nerve of, 937
ner\-us intermedius of, 901
Wrist-joint, 327
surface anatomy of, 1331
Xiphoid appendix, 121
process, 121
Y-SHAPED cartilage of acetab-
ulum, 237
ligament of Bigelow, 335
Yolk, formative, 39
nutritive, 39
Yolk-sac, 54
Yolk-stalk, 1103
Zigzag tubule, 1223
Zinn, ligament or tendon of, 1022
zonule of, 1018
Zones of abdomen, 1148, 1149
Zonula ciliaris, 1018
Zonule -of Zinn. 1018
Zygomatic arch, 183
bone, 164
branch of facial nerve, 905
nerve, 889
process of frontal bone, 136
of maxilla, 161
of temporal bone, 139
Zygomaticofacial foramen, 164,
187
nerve, 889
Zygomaticofrontal suture, 182
Zygomaticoorbital foramina, 165
Zj'gomaticotemporal foramen,
164, 183
nerve, 989, 890
suture, 182
Zygomaticus muscle, 383
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